Complement and the hallmarks of cancer

Mikel Rezola Artero, Andrea Minery, Leon Nedelcev, Maria Radanova, Lubka

T Roumenina

► To cite this version:

Mikel Rezola Artero, Andrea Minery, Leon Nedelcev, Maria Radanova, Lubka T Roumenina. Complement and the hallmarks of cancer. Seminars in Immunology, 2025, 78, pp.101950. 10.1016/j.smim.2025.101950. hal-05029960

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Submitted on 10 Apr 2025

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Review

Complement and the hallmarks of cancer

Mikel Rezola Artero<sup>a</sup>, Andrea Minery<sup>a</sup>, Leon Nedelcev<sup>b</sup>, Maria Radanova<sup>b</sup>, Lubka T. Roumenina<sup>a, c, *</sup>

<figure><img src="image_3.png" /></figure>

ARTICLE INFO

Key words:

Hallmarks of cancer

Complement system

Intracellular complement

Immune evasion

Immunoediting

A B S T R A C T

The hallmarks of cancer are a set of traits that normal cells acquire during their transformation into malignancy. Among the biological processes influencing these hallmarks, the innate immune complement system plays a critical role. It can operate canonically—in blood and tissues—via phagocytosis, inflammation, and complement-dependent cytotoxicity, similar to its roles against invading pathogens. Additionally, it functions non-canonically by modulating the behavior of cells within the tumor microenvironment and their intracellular landscape which regulates cell fate. These mechanisms contribute to the complex and context-dependent roles of complement in both tumor growth and antitumor immunity, shaped by the characteristics of the dynamic tumor microenvironment. This review analyses the multifaceted interplay between complement proteins and cancer hallmarks, positioning this system as a target to cancer therapy.

1. Introduction

The concept of Hallmarks of Cancer, proposed by Hanahan and Weinberg, serves as a heuristic tool to group the immense complexity of cancer's phenotypes and genotypes into a set of fundamental principles [1-4] (Fig. 1). These represent functional capabilities that human cells acquire during the formation of malignant tumors. Initially, six hallmarks were defined: sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative mortality, inducing or accessing vasculature, and activating invasion and metastasis [1]. Later, four additional hallmarks were incorporated, including dysregulating cellular metabolism and avoiding immune destruction [2], and more recently, genome instability and tumor-promoting inflammation [3]. As cancer research progressed, new conceptual dimensions were introduced such as phenotypic plasticity, non-mutational epigenetic reprogramming, polymorphic microbiomes, and the role of senescent cells in the tumor microenvironment (TME) [4]. Moreover, the nervous system also influences tumor development and progression, with novel data showing its role in modulating core and emerging hallmark phenotypes [5]. In this broader context, cancer is increasingly recognized as a complex systemic disease, englobing not only tumor initiation and promotion, but also aging, metabolism, obesity, cancer

cachexia, circadian rhythms, nervous system interactions, tumor-related thrombosis, tumor micro- and immune macro-environments, and the microbiome [6]. These hallmarks enhance our understanding of cancer and can guide the development of targeted therapies. By co-targeting multiple hallmarks, drug resistance can be overcome more effectively, leading to better patient outcomes. To develop optimal therapeutic strategies, a better understanding is needed on the mechanisms behind these functional capabilities.

As a first line of immune defense against pathogens, the complement system promotes inflammation and immune destruction via opsonization, anaphylatoxin generation and membrane-attack complement (MAC)-dependent cell killing. Extending these anti-microbial mechanisms to tumor cells seems evident, given that tumor-promoting inflammation and avoiding immune destruction are two key immune-related hallmarks of cancer.

The role of the immune system in cancer is conceptualized by the 3E and 3 C theories of immunoediting and immunoevastion. Immunoediting is characterized by changes in the immunogenicity of tumors due to its crosstalk with the anti-tumor immune response, resulting in the emergence of immune-resistant malignant clones [7,8]. This process occurs in three phases: Elimination, where the immune system attacks and attempts to eliminate emerging tumor cells; Equilibrium, where

<footnote><sup>a</sup> Centre de Recherche des Cordeliers, Institut National de la Santé et de la Recherche Médicale, Sorbonne Université, Université de Paris Cité, Team Inflammation, Complement and Cancer, Paris F-75006, France</footnote>

<footnote><sup>b</sup> Department of Biochemistry, Molecular Medicine and Nutrigenomics, Medical University of Varna, Varna, Bulgaria</footnote>

<footnote><sup>c</sup> University Hospital Federation (FHU) COMET, Paris, France</footnote>

<footnote>* Correspondence to: Centre de Recherche des Cordeliers, 15 rue de l'Ecole de Medecine, Paris 75006, France.
E-mail address: lubka.roumenina@sorbonne-universite.fr (L.T. Roumenina).</footnote>
some tumor cells survive and adapt under immune pressure; and Escape, where immune-resistant tumor cells proliferate uncontrollably, evading immune detection and destruction. In 2024 the theory of 3 C is proposed to explain this immunoevasive phenotype [9]. The evasion involves mechanisms classified under the "three Cs": (1) Camouflage, hiding cancer cells from immune detection, (2) Coercion, disrupting immune effector cells, and (3) Cytoprotection, protecting cancer cells from immune attacks. Overcoming these evasive tactics is key to improving immunotherapy and anticancer strategies. However, despite in-depth analysis of the immune system's role in cancer, the complement system is rarely considered in the 3E and 3 C theories. Here, we aim to position the complement cascade within the frameworks of the 3E and 3 C theories, showing how complement, initially designed to eliminate the tumor cells, can paradoxically fuel tumor progression via chronic inflammation, reprogramming of the infiltrating immune cells, prevention of immune destruction and activation of neoangiogenesis.

In recent years, the functional role of complement has expanded beyond its classical cascade functions to include non-canonical activities. Complement proteins do not only interact with each other but also can bind complement-unrelated targets and receptors in the extracellular space, as well as act intracellularly in ways previously unrecognized. Within the intracellular space, complement proteins work together to form the *complosome*, an intracellular complement system that functions as a pro-survival mechanism, regulating cellular energy metabolism and inflammatory responses [10]. Moreover, individual complement proteins can also bind to complement-unrelated partners within the intracellular space, participating in the regulation of the cell cycle, transcription and autophagy, among others [11]. The discovery that many complement proteins contribute to diverse and unexpected cellular processes has redefined their significance and has dramatically reshaped the field. Once dismissed as a rigid plasma cascade with a confusing nomenclature—where C4 precedes C1 and C2 but comes before C3—complement research has now emerged as a dynamic area of basic and translational science, driving new discoveries and therapeutic advancements.

In this review, we explore how the complement system, both as a whole and through its individual proteins, contributes to the biological processes of the hallmarks of cancer. Beyond its role in immunoediting

and immune evasion, complement proteins exert a complex and context-dependent influence on nearly all cancer hallmarks through both extracellular and intracellular mechanisms.

## 2. Complement system

The complement system is a key part of the innate immunity, considered to serve as a first line of defense against invading pathogens and 'altered' (pathologically stressed, activated, malignant...) host cells [12]. This system is composed of more than thirty soluble plasma and membrane-bound proteins that operate in various body fluids, host tissues, and cell surfaces [13,14]. It acts as an immune surveillance system that identifies 'danger', defined as the recognition of surfaces lacking 'self' signals, or the detection of pathogen-associated molecular patterns (PAMPs) and danger-associated molecular patterns (DAMPs) that arise in pathological conditions such as infection or cancer [15]. Thus, this system requires a proper balance between complement regulators (present on 'self' cells) and activators (targeting PAMPs and DAMPs) to actively protect 'self' and target 'non-self/altered' structures.

The complement cascade can be activated through three different pathways: the classical and lectin pathways, which recognize different DAMPs and PAMPs, and the alternative pathway, which targets structures lacking complement regulators [13]. These various pathways are activated by invading pathogens and 'altered-self' cancer cells which are identified as 'danger'. However, similarly to pathogens, tumors have developed a set of strategies to subvert the complement system and survive within the host. Since complement activation is tightly regulated within the human body to prevent bystander tissue damage, cancer cells exploit this control by overexpressing membrane-bound and soluble complement regulators on their surfaces, thereby preventing excessive complement-mediated damage [12].

Complement proteins in plasma are mainly produced by the liver. Nevertheless, many stromal and immune cells can also produce these proteins, regulating their concentrations locally [16]. In its classical location—the extracellular space in blood and tissues—complement proteins work together to form the enzymatic cascade that results from the activation of this system [13,14]. Through the generation of bioactive complement molecules, this system orchestrates three different

<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Hallmarks of cancer. Adapted from Hanahan, D. [4].</figcaption></figure>
canonical complement functions: 1) inflammation through the genera-
tion of anaphylotoxins, 2) opsonophagocytosis through the deposition
and recognition of complement opsonins and 3) MAC-mediated mem-
brane damage and cell lysis (Fig. 2).

Over the past decade, this vision on the complement system has broadened. It is now recognized that complement also plays important roles at individual cell-intrinsic levels (Fig. 3). Notably, some complement components have been demonstrated to act intracellularly, sustaining various biological processes such as cell survival, cell activation or even cell metabolism [10,17–51]. Intracellular complement proteins may act together in a cascade-like fashion, or operate independently by interacting with novel intracellular partners. Similarly, in the extracellular space, complement proteins can act outside the cascade in an autocrine or paracrine manner [52–59]. These cell-autonomous functions of the complement proteins in cancer are further discussed by Revel et al. in this special issue.

Taken together, advances in our understanding of complement pro-
teins reveal that they are more than just a plasma cascade. Complement
proteins exhibit a broad spectrum of functions, within the cascade—
acting as part of the coordinated complement cascade in the

extracellular space or inside cells—as well as outside the cascade in both
intra- and extracellular environments. Each of these functions have been
described in cancer, affecting its hallmarks across tumor contextures
(Fig. 4).

3. Tumor-promoting inflammation

3.1. *Definition of the hallmark*

In tumors, cancer cells can manipulate immune cells to support their growth and expansion. During activation, especially in chronic inflammation, immune cells release cytokines and reactive oxygen species (ROS) that foster an immunosuppressive, pro-carcinogenic environment [2]. Consequently, tumor cells produce factors that promote survival, migration, blood vessel formation, and immune evasion, with activation of NF-κB, TGF-β, β-catenin or Akt signaling pathways linked to cell survival, migration, and proliferation. Additionally, immune cells release mutagenic compounds, such as ROS, that drive the genetic evolution of tumor cells.

<figure><img src="image_5.png" /><figcaption>**Fig. 2.** The complement cascade, activation and regulation. The complement cascade, operating in blood and tissues, can be activated by three pathways: classical, lectin and alternative. These pathways converge at the cleavage of the central complement component C3, followed by C5, generating the bioactive fragments C3a and C5a. These pro-inflammatory anaphylatoxins recruit and/or activate immune, endothelial and vascular smooth muscle cells, expressing C3aR and C5aR1 at the site of complement activation. C3b/d and the recognition unit of the classical pathway C1q opsonize the target cell, facilitating their phagocytosis by macrophages, neutrophils and dendritic cells, which express corresponding receptors. The activation of the terminal complement pathway results in formation of the membrane attack complex MAC, C5b-9, which activates the target nucleated cell, often resulting in cell death and elimination. To avoid host tissue damage, the complement cascade is tightly controlled by multiple negative regulators, keeping in check every step of the cascade.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Intracellular complement in homeostasis and cancer. Intracellular complement proteins impact a wide variety of functions across different cell types of the human body, playing a crucial role in maintaining cellular homeostasis. In tumor cells, intrinsic/intracellular complement proteins regulate the fundamental functions of the cell, including viability, proliferation, morphology, migration and cell cycle by still poorly understood mechanisms. These processes are important, as various cohort studies and mouse models have shown that they promote or suppress tumor growth depending on the context and the tumor type.</figcaption></figure>

<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Extracellular and intracellular functions of the complement proteins in tumor cells. Complement proteins have functions which are not restricted to the canonical, blood-borne complement cascade. They interact with each other to form the complement cascade in the extracellular space and in a cascade-like manner intracellularly. Also, they have complement-independent, moonlighting functions both in the extracellular and intracellular space, binding to proteins unrelated to the complement system. All these functions impact the hallmarks of cancer and should be taken into account when analyzing the role of a given complement protein in any biological process in cancer and beyond.</figcaption></figure>
## 3.2. Role of complement

Malignant cells fuel chronic inflammation by promoting the release of cytokines, growth factors, chemokines and ROS to induce an immunosuppressive environment. As part of the inflammatory hijacking by cancer cells, the complement system is activated upon detection of DAMPs within the tumor, leading to the generation of C3a and C5a anaphylatoxins [60] (Fig. 5). This hallmark is driven nearly entirely by the release of the anaphylatoxins in the TME.

Rather than facilitating tumor elimination, these anaphylatoxins have been shown to promote immunosuppression and tumor growth. For example, cancer mouse models have shown that anaphylatoxins promote immunosuppression through the C5a-mediated recruitment of myeloid-derived suppressor cells (MDSC) to primary tumors or pre-metastatic niches [61–64]. Additionally, complement also influences other aspects of immunity such as the C3a-mediated recruitment of polymorphonuclear neutrophil (PMN) PMN-MDSC to metastasis bearing livers [65], the C3a/C5a mediated polarization of myeloid and T cells towards pro-tumorigenic phenotypes [51,66–72], the C3a/C3aR1 axis mediated attraction of macrophages and exclusion of CD4 + T cells and neutrophils from the tumor [73] or the C5a mediated recruitment of tumor promoting macrophages [74], among others. These observations in mouse models are further supported by the synergistic anti-tumoral effects of combining C3a/C3aR1 or C5a/C5aR1 inhibition with cytotoxic therapy [75–77] or immune checkpoint inhibitors [61,78,79]. Interestingly, C5aR1 is also overexpressed in tumor-infiltrating dendritic cells (DC) compared to DCs from blood or spleen in lung cancer mouse models [80]. In this model, C5aR1 expression was confined to type 2 conventional DC (cDC2) and monocyte-derived DC (moDCs), both of which exhibited a tolerogenic phenotype that suppressed T-cell activation and supported tumor progression. Furthermore, C5aR1 activation in DCs facilitated their migration to tumor-draining lymph nodes, where elevated C5a levels were detected [80]. These data could pave the way for exploring complement-mediated tolerogenic efferocytosis by DCs, offering new avenues for research and potential therapeutic strategies

In addition to anaphylatoxins, C3d/iC3b-CR3 interaction following complement activation has been shown to support neutrophil-mediated inhibition of T cell responses in ovarian cancer [81,82]. Apart from tumor promotion, complement activation also supports tumor initiation. In a colorectal tumorigenesis mouse model, C5a/C5aR1 signaling axis recruited MDSCs into the inflamed colorectum to impair CD8+ T cells and modulated the production of pro-tumoral cytokines and chemokines, thus initiating tumor growth [83]. Moreover, factor H (FH) deficient mice, which are incapable of controlling alternative pathway activation, develop spontaneous hepatic tumor likely due to complement-mediated chronic inflammation [84]. In a study using tumor-bearing mice with high and low C5a-producing lymphoma cells, it was observed that tumors with low C5a production exhibited slower growth compared to those producing either high or no C5 [85]. This concept is interesting but has to be explored further in more physiologically-relevant models.

Chronic inflammation is one of the main mechanisms by which complement promotes tumor growth (Fig. 5). This topic is extensively discussed by Pio and colleagues in this special issue [86] and is only briefly summarized here. Even if the mechanisms vary - in some tumor models C3a/C3aR1 is playing a leading role, while more commonly C5a/C5aR1 is the main culprit, studies are consistent to show a tumor promoting role. This resulted in the initiation of several clinical trials, aiming to inhibit complement at C3 or C5aR1 level in combination with checkpoint inhibitors as anti-cancer therapy [79].

# 4. Avoiding immune destruction

## 4.1. Definition of the hallmark

In physiology, immunity is a powerful surveillance system that detects and eliminates abnormal or damaged cells. However, tumor cells can evade this process and enter an equilibrium phase, where their growth is kept in check through the attack by the immune system. During this period, tumor cells adapt to evade immune detection and

<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Intratumoral complement activation causes chronic inflammation via the release of the anaphylatoxins C3a and C5a. These molecules recruit immunosuppressive myeloid cells, decreasing T cell activation, proliferation and causing T cell dysfunction and exhaustion. Depending on the tumor type, C5a or C3a will be the dominant pathway, however, both can act in synergistically. In many cancers, these pro-tumoral processes outweigh the anti-tumoral complement-dependent cytotoxicity (CDC). The opsonophagocytosis is a double-edged sword, capable of promoting either immune tolerance and anergy or antigen presentation and immune activation, depending on the context.</figcaption></figure>
elimination by hijacking the immune checkpoint program. This process is at best now explained by the 3E and 3C theories described above [7–9].

### 4.1.1. Role of complement

#### 4.1.1.1. The membrane attack complex (MAC).
The primary function of complement is the elimination of pathogens and damaged cells, as well as the removal of cells undergoing malignant transformation [87], which likely takes place in the early elimination phase of the 3E theory [7] (Fig. 6, left). This can be mediated by MAC, a flexible immune pore complex [88] that induces cell death by multiple mechanisms, including necroptosis [89] (see the section Resisting cell death). Necroptosis, in turn, is a form of immunogenic cell death that stimulates tumor antigen presentation by dendritic cells, leading to T and B cell activation due to stimulation of follicular helper CD4 T cells needed for Isotype switching and long, pro-inflammatory humoral response memory, and a robust anti-tumor immune response [90,91]. The concept of immunogenic cell death has been primarily forged for anti-cancer therapy and viral infections. Based on the similarities between the pathways triggered by immunogenic cell death inducers and MAC, it is tempting to speculate that the MAC-mediated cell death could be immunogenic. Thus, if complement-overactivating antibodies could overcome the natural complement resistance of tumors, they may trigger an anti-tumor immune response through MAC insertion and subsequent immunogenic cell death [92]. Indeed, this mechanism has been demonstrated in preclinical mouse models using the FH-targeting antibody GT103, where complement attack on tumor cells causes immunogenic cell death due to the synergistic action of blocking a complement regulator and antibody-mediated classical pathway activation. Even if not all tumor

cells are directly killed by complement, the potent reprogramming of the immune infiltrate in the GT103-treated mice leads to a reduced tumor burden [93,94]. This antibody is now in clinical trial in combination with checkpoint inhibition in advanced lung cancer [95,96].

In tissues MAC can be generated by the activation of the complement cascade via the three well-known pathways but also by other proteolytic enzymes [97]. Two very recent studies independently demonstrate that Granzyme K (GZMK) secreted by a population of CD8 + T cells can cleave complement components, particularly C2 and C4, to form a C3 convertase [98,99]. These GZMK+ CD8 T cells secrete cytokines and have the potential to drive inflammation and have a low cytotoxic capacity as the express low levels of granzyme B and perforin [100]. Their role in complement activation in cancer is unknown but their presence is associated with neutrophil abundance in colorectal tumors and predict poor prognosis [101]. Therefore, further studies are necessary to unravel the cancer relevance of this new mechanism of complement activation.

#### 4.1.1.2. The immunogenic properties of C3d.
C3d is the terminal C3 cleavage fragment, which remains covalently bound to the cell surface following complement attack or can be generated as a free fragment after the degradation of fluid phase C3b or C3(H₂O) [102]. Extensive research with mouse models has shown that C3d acts as a “molecular adjuvant” that bridges innate and adaptive immune responses. When covalently bound to an antigen, C3d facilitates efficient antigen recognition and uptake by antigen-presenting cells, particularly follicular dendritic cells (FDCs) and B cells and via complement receptor 2 (CR2/CD21) [103–105]. Therefore, C3d is immunogenic [106] (Fig. 6, left), whereas the preceding C3 activation fragment, iC3b, has tolerogenic properties [107] (Fig. 6, right), when they interact with complement receptor 3 (CR1, CD11b/CD18) on myeloid cells. CR3 in its bent

<figure><img src="image_9.png" /></figure>

**Fig. 6.** Mechanisms of complement-mediated immune destruction and complement subversion – hypothesis for the action of complement in the different phases according to the 3E theory. Left: If the complement cascade proceeds until the end, the MAC pore is inserted into the cancer cell’s membrane, triggering different forms of cell death, including immunogenic cell death such as necroptosis. This results in immunogenic antigen presentation and the mounting of an efficient anti-tumor immune response by the T cells and B cells. Moreover, C3d opsonization of tumor cells induces myeloid cell (dendritic cells, macrophages) activation during phagocytosis via CR3, and follicular dendritic cell activation via CR2, followed by antigen presentation, T and B cell activation and expansion. This leads to tumor elimination by tumor cell killing and elicits the anti-tumor immune response. Right: Tumor cells are opsonized by iC3b, which, together with C1q on the tumor cell surface, render them a “super self”, triggering tolerogenic phagocytosis by myeloid cells (macrophages, dendritic cells) and the suppression of T cells. This is facilitated by the chronic inflammation mediated by C3a and C5a (see Fig. 5). These anaphylatoxins along with FH secreted by tumor cells, promote expansion of Tregs, which in turn suppress T cell activation, and M2 polarization of macrophages. C1q+ TAM also promote T cell exhaustion. These mechanisms synergize to facilitate the immune escape and tumor progression. They have been described in various models and may differentially impact the capacity of tumors to avoid immune destruction depending on the tumor type.
conformation engages C3d, leading to immune cell activation, whereas its extended conformation binds iC3b, inhibiting immune responses [108]. Therefore, tagging the tumor cells with C3d could boost tumor-specific immunity. Indeed, in mouse models, mouse C3d, expressed as a free peptide by transfecting tumor cells, confers resistance to tumor growth in a CD8 T-cell dependent manner, suppressing PD1 expression [109]. Linking C3d to an internalization peptide and administering it to mice triggered a robust cell-mediated immunity in a multiple myeloma model, eliminating highly mutated clones and sparing non-transformed B cells and plasma cells. Mechanistically, C3d internalized by tumor cells activated E2F1-mediated expression of long noncoding RNAs and upregulated ribosomal RNA expression, which was linked to the expression of defective ribosomal products by malignant cells and MHC-I presentation of immunogenic peptides [109] An interesting strategy was applied in mouse models of non-Hodgkin lymphoma. Treatment of the mice with anti-CD20 resulted in opsonization of the malignant cells with C3d. A drawback of the treatment in patients is the internalization of CD20, which leads to loss of therapeutic efficacy. Treatment of such C3d+ tumor models with anti-C3d neoepitope antibody dramatically improved survival and anti-CD20 treatment efficacy [110]. Further studies are needed in human settings, but C3d could be an interesting mechanism to exploit to mount immune response against tumor cells, as the immune system naturally uses it to defend against pathogens. The potential clinical applicability of C3d lies in its ability to potentiate vaccine platforms for cancer where immune tolerance to self-antigens is a major hurdle.

#### 4.1.1.3. Immune escape thanks to the tolerogenic iC3b.
Tumor cells that escape the immune surveillance activate several protective pathways that counteract the MAC-induced cell death, thus, enriching the cancer cell pool in complement-resistant cells (Fig. 6, right). Even if complement is activated on tumor cells, they will remain tagged with iC3b, the tolerogenic fragment of C3 degradation, if no CR1-expressing myeloid cells are nearby since CR1 is the only cofactor of Factor I capable of promoting the cleavage of iC3b into C3d [102]. Therefore, tumor cells will be treated as a "super self" by the immune system, as iC3b will promote a tolerogenic response, which naturally occurs during the elimination of C1q and iC3b-opsonized apoptotic cells, without proceeding to MAC formation [108].

#### 4.1.1.4. Intratumoral complement regulators – tipping the balance between immune destruction and immune tolerance.
Literature analysis suggests that the overexpression of complement regulators by the tumor cells is, in general, a defensive mechanism against complement destruction. However, the level of expression of activators and regulators must be tightly balanced to both initiate the cascade—releasing C3a and C5a to sustain chronic tumor inflammation—and simultaneously prevent MAC-dependent cytotoxicity. The example of patients with clear cell renal cell carcinoma (ccRCC) is illustrative in this respect, as the cascade is activated on intratumoral immune complexes, generating anaphylatoxins, but the formation of the MAC is inhibited [31,32,111–115]. Another very interesting example is the non-small cell lung cancer (NSCLC). In a Spanish cohort of patients, it was shown that intratumoral complement activation correlates with poor prognosis [116], while in a cohort from China, this intratumoral complement activation correlated with favorable outcome [117]. In both cases, complement regulators over-expression was at play. In the first case, the cascade was overactivated despite the overexpression of the regulators, leading to chronic inflammation through the anaphylatoxins release without achieving MAC-mediated cytotoxicity. In contrast, in the second case, the outcome was favorable since the regulator's expression were lower, allowing the cascade to achieve potential cytotoxicity [117]. These contrasting results may potentially be explained by the heterogeneity of the NSCLC entities, particularly due to the role of EGFR. Aberrant EGFR signaling was critical for the overexpression of CD55 and CD59. In European

NSCLC cohorts, the EGFR mutations are rare (10%) contrary to Asia (50%), and hence, it is not surprising that if the mechanism of the disease is different, the contribution of complement could be also different. This is a perfect illustration of how complement in cancer may be context-dependent [118], influenced by factors such as geographic origin and EGFR mutation status [119].

#### 4.1.1.5. Extracellular, complement cascade-unrelated functions of complement proteins in immune escape.
In addition to its canonical effector functions within the cascade, tumor-derived FH has also been linked to the M2 polarization of tumor-infiltrating macrophages, which is associated with tumor progression in breast cancer [120] (Fig. 6, right). Moreover, the direct binding of FH to the immune checkpoint molecule ICOS promotes the survival and function of Tregs [121]. This involves the secretion of TGF-β and IL-1 and the suppression of T-cell proliferation in glioma. Furthermore, human factor H-like protein 1 (FHL-1) has been shown to promote an M2 secretory profile in murine macrophages within a glioblastoma in vitro model [122]. The role of the complement regulators in cancer is discussed in this special issue in terms of mechanism of action and therapeutic targeting [96,123].

#### 4.1.1.6. Intracellular, complement cascade unrelated functions of complement proteins in immune escape.
Another strategy that cancer cells employ to evade immune attack involves the hijacking of physiological mechanisms that regulate immune responses, such as immune checkpoints (e.g. by overexpression of PD-L1 and PD-L2 which inhibit T cell responses). C1q-expressing tumor-associated macrophages in renal cancer, colon cancer, malignant pleural effusion and other solid tumors are associated with an immunoinhibitory effects and correlate with T cell exhaustion [112,113,124–127] (Fig. 6, right). In a mouse malignant pleural mesothelioma model, deficiency of C1q in macrophages rescued the exhausted status of CD8⁺ T cells and enhanced the immune activity of CD8⁺ T cells and NK cells [124]. The mechanism is not fully understood but is independent from the complement cascade. Furthermore, it may involve not only macrophage phenotype reprogramming (PD-L2 expression) but also the internalization of C1q by CD8 T cells, where it could deregulate energy metabolism, triggering tolerance and immunosuppression [25]. Interestingly, FABP4 +C1q+ macrophages enhance antitumor immunity and are associated with response to neoadjuvant anti-PD1 therapy and chemotherapy in lung cancer [128], suggesting that the role of C1q and the C1q+ macrophages may differ in primary tumors depending on the presence or absence of checkpoint inhibitors.

Another complement component, C1s, when overexpressed by tumor cells modulates the immune infiltrate by a still not well understood, cascade-unrelated, mechanism in ccRCC and glioma/glioblastoma, promoting an immunosuppressive phenotype in macrophages and T cells exhaustion [31,129].

Fig. 6 represents a model of how complement could function in each phase of the tumor development, from the elimination, to the equilibrium and the subversion and escape of the immune system. Further research is needed to validate it and to explore the interplay between the ensemble of the above-described mechanisms and how they could be harnessed via therapeutic approaches to induce a complement-mediated immunogenic cell death to trigger a robust anti-tumoral immune response.

# 5. Resisting cell death

## 5.1. Definition of the hallmark

Apoptosis is a programmed cell death mechanism essential for maintaining homeostasis via elimination of damaged, mutated or unnecessary cells. It is initiated by death-inducing signals, such as DNA damage, which activate cytoplasmic proteases called caspases. This activation leads to the orderly disassembly of the cell, including nuclear
DNA fragmentation and cell blebbing. The resulting apoptotic bodies are cleared by phagocytic cells. To evade apoptosis, malignant cells often inactivate key genes involved in DNA damage sensing and apoptosis induction, such as TP53, while upregulating anti-apoptotic regulators, such as Bcl-2. Apoptosis is only one form of cell death, the other being necroptosis, ferroptosis, pyroptosis, etc.

### 5.1.1. Role of complement

#### 5.1.1.1. MAC-mediated cell death.
MAC-mediated cell death is the primary mechanism of direct anti-tumor action of the complement cascade (Fig. 7). The insertion of the MAC C5b-9 complexes into the cell membrane induces a calcium ion influx which activate lytic signals (Fig. 7, left). The signaling mechanisms leading to cell death are multifactorial, likely cell type-dependent, and require further studies. Nevertheless, MAC insertion seems to activate more than one cell death pathway on nucleated cells. One pathway involves RIPK1, RIPK3, and MLKL-mediated necroptosis, likely acting in parallel to an apoptotic process [130,131].

Despite MAC's ability to trigger multiple cell death pathways, tumor cells have developed strategies to evade its cytotoxic effects. Indeed, multiple reports have linked the local increase of different complement components to cancer cell survival and apoptosis regulation. One key mechanism is the overexpression of membrane regulatory proteins (CD46, CD55 and CD59) and soluble regulators (FH, C4BP, FI, clusterin and vitronectin) [89,132–134] (Fig. 7, left), which help tumor cells evade MAC-mediated cell death. Resistance to MAC-mediated cell death is also facilitated by the elimination of C5b-9 through endocytosis or expelling via extracellular vesicles, as well as the inhibition of cell death

signals by caveolin and dynamin, Hsp70 and Hsp90, and the mitochondrial stress protein mortalin [89,135–137] (Fig. 7, left). Interestingly, malignant cells can also further enhance the protective ability of complement regulators through post-translational modifications. In breast cancer, for example, the sialylation of the membrane-bound regulator CD55 increases complement resistance [138]. In the context of EGFR-mutated lung cancer, EGFR/Wnt/β-catenin signaling triggers upregulation of CD55 and CD59, suppresses complement activation and CD8 + T cell function, facilitating tumor immune evasion and resistance to immune checkpoint inhibitors [117].

Besides membrane-bound regulators, malignant cells also hijack soluble regulators, such as FH, C4BP, FI, clusterin and vitronectin, to limit terminal pathway initiation. For instance, many intestinal and ovarian tumors present polyanionic, sulphate-rich mucins on their surfaces, which provide a strong binding surface for FH [139] (Fig. 7, left). Tumors can also express and bind the master regulator of the alternative pathway FH to evade complement attack as in the case of glioblastoma, ovarian cancer and NSCLC cells [132,140,141]. This mechanism is not only limited to FH; the hijacking of C4bp has also been observed in ovarian cancer cell lines [142].

#### 5.1.1.2. Cell-autonomous cascade-unrelated intracellular and extracellular functions of complement proteins.
Apart from MAC-mediated cell death resistance via the overexpression of regulators [96,123] (Fig. 7, left), research over the last 10 years has revealed that complement proteins overexpressed by tumor cells could promote resistance to cell death in a cell-autonomous manner (intracellular or extracellular) independent of the plasma complement cascade (Fig. 7, right). Moreover, these mechanisms impact the tumor response to cytotoxic therapy [77]. For

<figure><img src="image_10.png" /></figure>

**Fig. 7.** Complement susceptibility vs. resistance to cell death. Complement proteins impact cell death context-dependently, either via MAC (left) or in a cell-intrinsic, complement cascade independent manner (right). Left: Immune destruction of cancer cells occurs through cytotoxic pathways triggered by MAC (blue), while tumor cells counteract these effects through resistance mechanisms (green). In nucleated cells, the formation of MAC rarely triggers plasma membrane perforation but instead induces Ca²⁺ flux, leading to mitochondrial damage and regulated necrosis or apoptosis. Tumor cells develop multiple strategies to avoid MAC-mediated cytotoxicity, including inhibition of signaling pathways, endocytosis of MAC or its expulsion via ectocytosis as extracellular vesicles. These mechanisms render MAC sublytic, making tumor cells more resistant to cell death and, potentially, even stimulating their proliferation. Right: Complement proteins impact cell death pathways in a cell-intrinsic manner, independently of the complement cascade. Depending on the tumor type, the overexpression or binding of different complement proteins confers resistance or susceptibility to cell death and to cytotoxic agents. The mechanisms underlying these processes are still poorly understood.
example, knockdown of C1s in ccRCC and cutaneous squamous cell carcinoma (cSCC) cells reduces viability; however, the resulting transcriptomic changes differ across these two cancer types, suggesting a cell-type-specific role for C1s [31,143]. In ccRCC, C1s acts intracellularly [31], whereas in cSCC, its effects are extracellular, as the cSCC C1s-deficient phenotype could be replicated by the addition of anti-C1s antibodies that block its enzymatic activity [144]. Additionally, in cSCC, silencing other complement components, such as C1r [143], FB [145], C3 [145], FH [146] and FI [147], also resulted in decreased numbers of viable cells. In esophageal squamous cell carcinoma (ESCC), silencing of C1r [148] or C1s [149] increases apoptosis, with C1s knockdown linked to Bcl-2 downregulation and increased caspase 3 activation [149]. In NSCLC, the knockdown of FI increases apoptotic transcriptomic programs and renders the cells susceptible to etoposide-induced apoptosis [150]. Intracellularly, FH has also been linked to the protection against cell death in ccRCC, potentially through p53 regulation [32]. Extracellularly, C1q increases resistance to oxidative stress-induced apoptosis in murine melanoma cells [151] but not in human mesothelioma cells [152], implying species- or cancer type-specific effects. Interestingly, sublytic levels of MAC deposition (sublytic MAC) have also been implicated in resistance to cell death in cancer cells, where its deposition on prostate cancer cell lines protects them from TNF-induced cell death in vitro [153].

Paradoxically, despite all this evidence linking complement to apoptosis resistance, complement overexpression can also increase apoptosis susceptibility. In colorectal cancer (CRC), the intracellular C4bp overexpression suppresses NF-κB signaling and renders the cells susceptible to oxaliplatin-induced apoptosis [29]. Additional reports also suggest pro-apoptotic effects of some complement proteins in certain cancers (Fig. 7, right). For instance, by activating the tumor suppressor WWOX, C1q promotes the apoptosis of prostate cancer cells and of a breast cancer mouse model [154,155]. C1q additionally induces apoptosis of ovarian cancer cells through activation of TNF-α and upregulation of the pro-apoptotic Bax and Fas [156]. Likewise, pro-erin displays some antitumor effects by promoting intracellular upregulation of the pro-apoptotic factor DDIT3, which is associated with endoplasmic reticulum stress response in breast cancer [157].

Overall, complement plays a major, yet again context-dependent role in the resistance to cell death, though its mechanisms are often poorly understood. Tumor cells exploit multiple strategies to subvert complement proteins, from overexpression of complement regulators at the cell surface to counteract MAC formation to the overexpression of individual complement proteins with cascade-unrelated functions, to enhance viability and resistance to stress (Fig. 7).

# 6. Sustaining proliferative signaling

## 6.1. Definition of the hallmarks

Under normal physiological conditions, cell proliferation is essential for tissue renewal and maintenance [1]. Normal cells produce growth factors to induce proliferation in neighboring cells through paracrine signaling, which is tightly regulated to maintain homeostasis. In contrast, cancer cells bypass this regulation, leading to uncontrolled proliferation. This occurs through two main mechanisms: increased production of growth factors in the TME, and hijacking of growth factor receptors and their signalling pathways by the tumor cells. Cancer cells may increase growth factor production or influence stromal tumor-associated cells to do so. They often have a hyper-mutational profile, causing constitutive activation of signaling pathways like B-raf and PI3K, or suppression of negative feedback mechanisms involving Ras and PTEN. Additionally, cancer cells can overexpress growth factor receptors, making them hyper-responsive to mitogenic signals or altering receptor structures to enable their activation without ligand recognition.

## 6.2. Role of complement

In this context, the complement system has been shown to sustain malignant cell proliferation by various mechanisms (Fig. 8).

## 6.3. Cascade-related intracellular and extracellular functions

Anaphylatoxin receptor signaling in tumor cells expressing C3aR1 and/or C5aR1 has been shown to stimulate cancer cell proliferation via the Akt and/or the Wnt/β-catenin signaling pathways in various carcinomas. For example, the C5aR1/Akt signaling axis promotes the proliferation of human breast [158] and ovarian cancer cell lines [159], as well as the proliferation of human endometrial and squamous cell lung cancer cell lines [159]. Similarly, in colonic cancer cells, intracellular C5 is cleaved by cathepsin D (CTSD) to produce C5a in lysosomes and endosomes [160]. After stimulation by C5a, intracellular C5aR1 forms a complex with KCTD5/cullin3/Roc-1 and β-catenin to enhance the pro-tumoral β-catenin stability. Similarly, C3aR1 signaling enhances proliferation in human ovarian cancer cells through Akt activation [159, 161] and in cSCC cell lines by activating the Wnt/β-catenin pathway [162]. The proliferative effects of C3aR1 have also been observed in murine lung carcinoma cells, particularly in anchorage-independent growth [67]. However, not all carcinoma cells respond similarly. For instance, stimulation by C3a and C5a in human ccRCC cells does not enhance proliferation [31].

Despite fine-tuning of complement activation by cancer cells, sometimes the cascade can still proceed to the terminal MAC formation, leading to the insertion of sublytic levels of C5b-9 which trigger the so-called response genes to complement (RGC) [163]. These RGC genes, specially RGC-32, have been shown to stimulate cell proliferation in various cancers that overexpress them [164]. Notably, these proliferative effects have been observed upon sublytic MAC deposition on JY25 a human lymphoblastic B cell line [165], yet its impact on other cancer types remains largely unexplored.

## 6.4. Cell-autonomous, intra- and extracellular, likely cascade independent functions

Some complement proteins seem to promote cancer cell proliferation independently of sublytic MAC formation or anaphylatoxin signaling, though the exact mechanisms remain unclear. For example, intracellular complement proteins such as C1s and FH in ccRCC, as well as FH in lung adenocarcinoma (but not lung squamous cell carcinoma) promote proliferation in a cascade-independent fashion, in addition to reducing viability as previously mentioned [31,32]. In other instances, it is unknown whether complement proteins are acting intracellularly or extracellularly, but their downregulation associates with decreased proliferation. In ESCC, for example, the knockdown of C1r or C1s decreases cell proliferation [148,149]. In glioma, C1s also facilitates tumor cell proliferation, cell migration and intracranial tumor growth in nude mice [129]. In cSCC, the knockdown of C1s [143], C1r [143], factor B (FB) [145], C3 [145], FH [146] and factor I (FI) [147] leads to reduced proliferation, linked to decreased ERK1/2 pathway activity. Notably, FI silencing in NSCLC cells reduces proliferation in an ERK1/2-independent manner [150]. These results suggest that the same complement component may act via different mechanisms depending on the cell type expressing them. The case of C1s is particularly intriguing. It is overexpressed in both ccRCC and in cSCC, and its knockdown induces the same global phenotypic changes (decreased proliferation and viability). However, transcriptomic analyses comparing C1s deficient and sufficient cells revealed distinct gene expression changes across cancer types [31,143,144]. Moreover, modification of the tumor cell behavior was independent of extracellular C1s as purified protein could not rescue the phenotype in ccRCC cells, suggesting that C1s is acting in an intracellular manner [31]. On the contrary, in cSCC cells, the phenotype was dependent on extracellular C1s and its enzymatic
<figure><img src="image_11.png" /><figcaption>**Fig. 8.** Complement sustains proliferative signaling. Multiple studies show that both complement cascade activation, via C3a and C5a, as well as the cell-intrinsic/intracellular complement proteins promote tumor cell proliferation. The mechanisms are not always fully understood, but in most cases either ERK1/2 or AKT or β-catenin pathways are involved, leading to proliferative signaling, transcription changes and cell cycle progression.</figcaption></figure>

activity, as C1s inhibition with an anti-C1s antibody rescued the phenotype [144].

Complement proteins also exhibit a dual role in proliferation across different cancer types. While some promote proliferation, others have the opposite effect. For instance, in human neuroblastoma, prostate, breast and ovarian cancers, C1q can promote anti-proliferative and pro-apoptotic signals [154-156]. On the contrary, in malignant pleural mesothelioma and murine melanoma, C1q promotes tumor cell proliferation through cell-C1q interaction on hyaluronic acid surfaces coated with C1q via enhancement of Erk1/2, SAPK/JNK and p38 phosphorylation [151,152]. The C1q receptor gC1qR is likely implicated in the regulation of proliferation [166] but further studies are needed to determine the underlining mechanisms.

These cascade-unrelated roles of complement—such as influencing proliferation and viability through both intracellular and extracellular mechanisms—can be just as significant, if not more impactful, than their canonical roles within the cascade (Fig. 8). This suggests that prognostic outcomes derived from complement overexpression cannot always be explained by the canonical effector functions of the complement cascade. These mechanisms may not be impacted by the available complement inhibitors in the clinic, highlighting the need for new therapeutic approaches targeting these versatile actions of complement proteins.

# 7. Activating invasion and metastasis

## 7.1. Definition of the hallmark

Metastasis is the leading cause of cancer-related morbidity and mortality [167]. It involves the spread of malignant cells from the primary tumor to another distant part of the body. The metastatic process can be divided into three key steps: invasion of the surrounding peritumoral tissue, intravasation of cancer cells into blood or lymphatic vessels, and extravasation into the parenchyma of a distant tissue. To acquire an invasive phenotype, cancers cells derived from epithelia undergo a process known as epithelial-mesenchymal transition (EMT). Throughout this process, malignant epithelial cells gain an invasive mesenchymal phenotype able to resist apoptosis, detach from their neighboring cells and infiltrate adjacent stromal tissue.

### 7.1.1. Role of complement

#### 7.1.1.1. Cascade-related functions.
Complement can sustain invasion and metastasis in transformed cells through multiple mechanisms. Anaphylatoxin receptor signaling in C3aR- and C5aR1-expressing tumor cells can drive migration, metalloproteinases (MMP)-mediated extracellular matrix degradation and EMT in various carcinomas. In NSCLC and cSCC, C5a and C3a, respectively, have been shown to enhance MMP expression, and promote cell migration and invasion, increasing metastatic potential [162,168]. In leptomeningeal metastasis,
cancer-cell-derived C3a activates the C3aR in the choroid plexus epithelium to disrupt the blood - cerebrospinal fluid barrier, allowing entry of plasma-derived mitogens to enter the cerebrospinal fluid, promoting tumor growth [169]. The C5a/C5aR1 axis also induces actin reorganization, facilitating cell migration and invasion in human bile duct cancer cells [170] and gastric cancer cells via RhoA activation [171]. This mechanism may, in turn, explain the poor prognosis associated with C5aR1 overexpression in human gastric cancer cells [172]. Additionally, both C3a and C5a are implicated in sustaining EMT and increasing cell migration and invasion in hepatocellular carcinoma (HCC), ovarian and endometrial cancer cell lines [173,174]. Interestingly, C5a can also indirectly support cancer metastasis by activating neutrophils/PMN-MDSC to generate neutrophil extracellular traps (NET), which enhance cancer cell migration and increase circulating cancer cells in an orthotropic mouse model [175]. In a melanoma model, complement activation on the tumor endothelium generated C5a and recruited neutrophils [176]. Upon contacting the complement activated endothelium, terminal MAC formation occurred on neutrophils, activating the release of NETs. These NETs increased vascular leakage, facilitating melanoma cells' entry into the circulation and systemic spread. Depleting neutrophils or preventing MAC formation in C6-deficient animals protected the endothelium and prevented melanoma cell intravasation.

In addition to sustaining proliferative signaling, sublytic MAC deposition has been proposed to facilitate metastasis. Microarray analyses on murine colon carcinoma cells with sublytic MAC deposition have revealed an upregulation of MMP expression linked to metastasis [177]. However, the direct functional consequences of sublytic MAC deposition on migration, invasion and metastasis have yet to be experimentally confirmed and validated in clinical samples.

### 7.1.1.2. Extracellular, cascade-unrelated functions.
There are additional associations between complement components and increased migration and invasion through extracellular, cascade-unrelated functions. For instance, C1q adhesion to murine melanoma and human mesothelioma cells promotes cell migration [151,152]. In HCC, C1q supports a metastatic phenotype by stimulating EMT and cell invasion through interaction and activation of DDR1 and promotion of MAPK and PI3K/Akt signaling pathways as well as expression of MMP2 and MMP9 [178]. A potential implication of gC1qR in this invasive process is feasible [166], as it regulates lamellipodia formation and metastasis in human lung carcinoma cells [179].

### 7.1.1.3. Intracellular, likely cascade-unrelated functions.
Beyond their extracellular roles, complement components can also act intracellularly to stimulate tumor migration and invasion. For example, intracellular C3 transduces S1P/S1PR1 signaling to activate cell migration in murine breast, prostate, bladder and melanoma cell lines, as well as in human breast and head and neck squamous cell carcinoma cell lines [43]. Additionally, in ccRCC, intracellular FH co-localizes with mesenchymal markers in patient tumors and sustains migration and maintenance of the actin cytoskeleton structure, though the underlying mechanisms remain unclear [32]. In cSCC, the knockdown of C3 [145], FB [145], FI [147], C1r [143] [180], C1s [143], FH [146] has been shown to reduce the migratory and invasive capacity of cSCC cells. Similarly, reduced migration and invasion have been observed in ESCC cells following C1r silencing [148]. In contrast, in certain cancers like HCC, C1r over-expression reduces cell migration and invasion [181]. As the mechanisms of action are poorly understood, it is still unclear whether these proteins act intracellularly by interacting with each other in a cascade-like manner or interact with still poorly defined binding partners outside the cascade.

### 7.1.1.4. Complement proteins in extracellular vesicles (EVs).
Tumor-derived EVs enriched in FH promote HCC cell growth, migration,

invasiveness, tumor formation and metastases in mice [182]. Additionally, these FH-enriched EVs protect HCC cells from complement-dependent lysis and phagocytosis, but the mechanism of action is not well understood. However, this property can be exploited for therapeutic targeting, as the anti-FH therapeutic antibody GT103 can target and destroy these EVs via classical pathway-mediated elimination [183]. Indeed, the use of another anti-FH mAb abrogated tumor metastasis in this HCC model [182]. In renal cancer mouse model, EVs rich in C3 promote lung metastasis by being absorbed by lung macrophages, which in turn increase CCL2 and CXCL1 secretion, recruiting TAMs and PMN-MDSCs to establish an immunosuppressive and pro-metastatic environment [184].

Overall, similar to their roles in proliferation and resistance to cell death, complement proteins affect migration and metastatic potential via the complement cascade as well as by cascade-unrelated functions in the extracellular and intracellular compartments (Fig. 9). These phenomena are well-documented at the cellular level and in mouse models, but their molecular mechanisms and relevance to human tumors are yet to be uncovered. For example, it remains unclear whether the intracellular complement proteins interact with each other — potentially explaining why their knockdown leads to similar phenotypic changes (C1r interacting with C1s or C3 with FB, FH and FI)—or if they have completely different binding partners unrelated to the ones in the extracellular cascade. From the very limited studies in cancer and beyond, it seems that both scenarios are possible. However, further studies are needed to unravel the molecular mechanisms and determine how they can be therapeutically targeted.

## 8. Evading growth suppressors

### 8.1. Definition of the hallmark

To proliferate, malignant cells must bypass anti-proliferation regulatory programs that control key cell-cycle checkpoints (G1/S and G2/M). Two critical oncosuppressors, RB (retinoblastoma-associated) and TP53, are inactivated in many animal and human cancers. These proteins determine whether cells will proliferate, enter senescence, or undergo apoptosis. RB responds to both external and internal signals, while TP53 detects intracellular signals such as cellular stress, genome damage, glucose levels and oxygenation. Defects in either protein in cancer cells lead to persistent proliferation.

### 8.2. Role of complement

Despite extensive evidence for proliferative roles of complement components, so far very little is known about how complement promotes escape from cell cycle regulation. Still, the downregulation of complement proteins has been shown to promote cell cycle arrest in different cancer types. For example, FB knockdown in human pancreatic ductal adenocarcinoma (PDAC) cell lines induces cell cycle arrest in G0-G1 [185]. Similarly, FH silencing promotes cell cycle arrest in G0-G1 in ccRCC cell lines [32] and in G2-M in irradiated breast cancer stem cells [186]. In addition to this, sublytic MAC deposition could potentially induce the activation of proto-oncogenes and the re-entry in the cell cycle, as previously observed in oligodendrocytes and aortic smooth muscle cells [187]. Further research is necessary to define how complement proteins could impact the evasion of growth suppressors.

## 9. Enabling replicative immortality

### 9.1. Definition of the hallmark

Tumor cells enable replicative immortality by controlling the telomere length, which limits the number of division cycles in normal cells. Each mitosis shortens the telomeres until they are too short to prevent chromosome end-to-end fusions. Once telomeres reach a critical length,
<figure><img src="image_12.png" /><figcaption>**Fig. 9.** Complement activation promotes invasion and metastases. Complement activation on tumor vasculature results in C5a release and MAC formation on recruited neutrophils. This activates neutrophils to release neutrophil extracellular traps (NET), which makes the endothelium leaky, allowing tumor cell to go to the bloodstream. C3a and C5a signaling on tumor cells, along with C1q/C1qR interaction and cell-intrinsic C3, FH, FI, C1r or C1s acting in a cascade-independent manner, promote epithelial to mesenchymal transition (EMT) of tumor cells, stimulating their migration and invasion capacity. Tumor cell-derived extracellular vesicles carrying FH or C3 migrate to the pre-metastatic niche. In the pre-metastatic niche C3 EVs are engulfed by macrophages, triggering CCL2 and CXCL1 secretion. This recruits more immunosuppressive myeloid cells, further preparing the pre-metastatic niche.</figcaption></figure>

cells enter senescence (a non-proliferative but viable state) and even-
tually crisis, leading to cell death. Cancer cells replicate more rapidly
than normal cells. To counteract telomere shortening, they express
telomerase, a DNA polymerase typically inactive in most normal cells.
Telomerase carries an RNA molecule that serves as a template for
elongating telomeres, allowing cancer cells to maintain sufficient telo-
mere length and replicate indefinitely.

9.2. Role of complement

So far, no complement components have been described as being
implicated in this process.

10. Inducing or accessing vasculature

10.1. *Definition of the hallmarks*

In both normal and tumor tissues, vasculature is crucial for deliv-
ering nutrients and oxygen while removing metabolic waste and carbon
dioxide. During embryogenesis, vasculogenesis (formation of endothe-
lial tubes) and angiogenesis (creation of new vessels from existing ones)
are highly active. After this phase, angiogenesis typically ceases,
occurring only during wound healing or the menstrual cycle. Cancer
cells reactivate angiogenesis to create new blood vessels that meet the
demands of the growing tumor. Within the hypoxic environment of the
tumor, hypoxia inducible factor-1 (HIF-1) is stabilized, leading to the
expression of vascular endothelial growth factor (VEGF), fibroblast
growth factor (FGF) and platelet-derived growth factor (PDGF), all of

which drive new blood vessel formation. Tumor cells specifically over-
express VEGF-A, which binds to receptors on endothelial cells. This
VEGF/VEGF-R signaling pathway, essential for normal angiogenesis, is
hijacked by tumor cells to stimulate new vessel formation and sustain
the tumoral vascular network.

10.2. Role of complement

Complement factors modulate angiogenesis directly, via interaction of C3a, C5a or C1q with receptors in endothelial cells or indirectly, via modulation of the phenotype of other cells in the TME, stimulating the secretion of pro-angiogenic factors [188] (Fig. 10).

10.3. Direct effects

C5a directly interacts with endothelial cells-expressed C5aR1 *in vitro*, enhancing their migration, proliferation, and vessel formation [189]. C1q promotes tumor growth by stimulating angiogenesis likely by an extracellular mechanism, independently of the complement cascade activation and anaphylatoxin generation [53]. In cervical and melanoma mouse cancer models, it promotes tumor growth by modulating neoangiogenesis [113,151]. C1q-deficient mice exhibit altered vascular density and organization, along with decreased expression of VEGF and VEGF-R. These effects are independent of classical pathway activation, as C4 deficiency does not affect vascular functions [113]. However, this effect appears to be context-dependent, as C1q deficiency in a spontaneous model of breast cancer is associated with enhanced angiogenesis [155]. Recent data suggest that C1s may also be involved in the
<figure><img src="image_13.png" /><figcaption>**Fig. 10.** The role of complement in tumor neoangiogenesis. Complement activation generates C3a and C5a triggering C3aR and C5aR1 signaling on 1) endothelial cells to promote neoangiogenesis directly and 2) on TAM and tumor cells, leading to secretion of pro-angiogenic factors, indirectly enhancing neoangiogenesis. C1q expression and binding to endothelial cells directly stimulate angiogenesis, independently of the complement cascade. Additionally, C1s produced by tumor cells—through an undefined mechanism—likely mediates this process indirectly. The pro-angiogenic role of complement, as described here, is observed in most of mouse tumor models. However, the presented mechanisms may or may not operate simultaneously in every tumor. The anti-neoangiogenic impact of C1q and the anaphylatoxins, observed in the spontaneous breast cancer mouse model, is not represented here.</figcaption></figure>

<figure><img src="image_14.png" /><figcaption>**Fig. 11.** The role of complement in epigenetic reprogramming in tumors. Long non-coding RNAs, such as circ-CFH and LINC00973, promote cancer progression by sponging miRNAs, thereby upregulating the expression of certain oncogenes (ATK1 and EGFR1) and cancer-related genes (CUL4B and RNF38). Reduced miRNA levels suppress complement and CD8+ T cell activation and influence MAC-cytotoxicity resistance. Intracellular C5aR1, via the ERK1/2 signaling cascade, enhances methyltransferase-like 3 (METTL3) expression and maintains m6A levels in GPX4 mRNA. This prevents ferroptosis in cancer cells, thus facilitating tumor progression. Nuclear C3b can associate with SIN3A/HDAC to form a complex that silences GADD45A through histone deacetylation in the promoter region of the gene. This inhibits apoptosis and enhances tumor growth.</figcaption></figure>

angiogenic process, as its knockdown significantly suppresses vascularization of human cSCC xenograft tumors in vivo, but the mechanism is not well defined [143]. Intracellular FH has been shown to affect glomerular endothelial cell proliferation and the vascular characteristics in the kidney [35], but not in primary human umbilical vein endothelial (HUVEC) cells [32], highlighting the need to explore its role in tumor neoangiogenesis. The involvement of other complement components

remains uncertain.

### 10.4. Indirect effects

C3a and C5a modulate TAM functionality, promoting immunosuppression and pro-angiogenic properties, via secretion of VEGF and other angiogenic factors [190]. In a mouse model of ovarian cancer, C3- and
C5aR-deficient mice exhibited significantly impaired angiogenesis and reduced tumor growth [191]. This effect is likely attributed to altered endothelial cell function, potentially mediated through interactions with VEGF. Reduced vascular density was observed in C3aR-deficient, as well as in wild-type mice treated with C5aR1 and C3aR inhibitors in a renal cancer model [192], further supporting the pro-angiogenic role of the C3a/C3aR axis. Nevertheless, these experiments do not allow to distinguish the direct effects on the blood vessels from the indirect effects on the TAM. In a K14-HPV16 transgenic mouse model of squamous carcinogenesis, C5aR1/- mice or the administration of C5aR1 inhibitor reduced the microvascular density, concomitantly with a decrease in tumor growth. However, C3 deficiency had no effect, as C5a was not generated via complement activation but likely via cleavage of C5 by plasmin [69]. Interestingly, the key driver cells affected by C5a were tumor-associated macrophages and mast cells, but not the neutrophils. These pro-angiogenic effects, however, appear to be context-dependent as C3 activation has been found to impair angiogenesis in a Her2/neu transgenic mice and remove autochthonous mammary carcinomas, but the mechanism remains unclear [193]. From a therapeutic perspective, the simultaneous inhibition of VEGF and complement (via dual treatment with VEGFR-Fc and CR1-Fc constructs) showed strong antitumor activity by inhibiting angiogenesis and enhancing anti-tumor immunity [144].

Although results vary depending on the tested model, and translating findings from animal experiments to patients remains challenging, the relationship between complement and blood vessels is evident. This must be considered in therapeutic interventions targeting complement proteins, as it may improve treatment effectiveness while also posing risks for side effects, such as vascular complications. Therefore, further studies are needed to dissect the molecular mechanisms linking complement proteins and angiogenesis in cancer as well as in physiological wound healing, placental development and pathological conditions like preeclampsia and retinopathy of prematurity [188].

# 11. Dysregulating cellular metabolism

## 11.1. Definition of the hallmark

The rapid proliferation of tumor cells requires substantial energy. To accommodate this, they reprogram their metabolism, opting for anaerobic respiration even in the presence of oxygen—a phenomenon known as the Warburg Effect or aerobic glycolysis. Rather than relying on mitochondrial oxidative phosphorylation, they prioritize glycolysis, which not only promotes immunosuppression through TME acidification or provides a faster source of energy, but also generates essential intermediates for macromolecule biosynthesis and organelles formation.

## 11.2. Role of complement

One of the most well-described consequences of the Warburg Effect is the increased production and accumulation of lactic acid, leading to the acidification of the TME. Interestingly, complement activation is enhanced in situations where the pH drops below 7.1 [194], making the acidic pH in the TME a potential “DAMP” detected by the cascade. Indeed, complement activation is often observed across different types of tumors [118], especially in those with strong HIF-1 activation such as in ccRCC and glioblastoma [51,111]. Acidic pH has been shown to favor cascade activation through multiple mechanisms including: increased formation and stabilization of the alternative pathway C3 convertases [195], activation of the classical pathway through IgG or CRP activation [196–198], or increased spontaneous hydrolysis of C3 and formation of C3(H2O) [199], among others. Moreover, low pH induces polyreactivity of IgG [200], which may contribute to explain the massive opsonization with IgG seen in some tumor types, resulting in classical pathway activation, such as ccRCC [113]. Below pH 6, though, complement mediated cytotoxicity could be inhibited [201]. Despite the links between pH and

complement activation, this potential mechanism remains largely unexplored in the context of cancer.

There is substantial evidence demonstrating how intracellular complement proteins regulate glycolysis and oxidative phosphorylation in various immune and non-immune cells [10], but very few reports have shown direct links between complement and cancer cell metabolism. A recent study in HCC has linked the downregulation of C1r to increased aerobic glycolysis through activation and stabilization of HIF-1 [181]. Interestingly, tumors may also benefit from complement-mediated metabolic regulation in immune cells. For instance, C1q's interaction with C1q binding protein (C1qbp) on mitochondria has been shown to regulate CD8 + T cell survival and metabolism, preventing excessive activation and immunopathology in autoimmune and viral infection contexts [25]. Unexpectedly, C1qbp deficient mice present weaker anti-tumoral T cell responses in a subcutaneous xenograft mouse model, indicating that C1q may actually support T cell activation in this context [202]. Additional links between intracellular complement and cellular metabolism described in immune cells [17,203], are likely at play in cancer, happening both malignant and non-malignant cells, shaping the TME and potentially impacting therapeutic outcomes.

# 12. Genome instability and mutation

## 12.1. Definition of the hallmark

Carcinogenesis begins when a cell acquires a mutation that provides a selective advantage in its local environment. This is followed by tumor progression, characterized by a series of mutation-driven clonal expansions. The high proliferation rate of cancer cells accelerates genomic changes, affecting replication, survival and the mutational repair machinery. This results in genome instability, defined by numerous chromosome deletions and amplifications, which establishes various cancer hallmarks. Intratumoral heterogeneity arises as a consequence of this genomic instability, which increases the adaptability of the tumor to different environments.

## 12.2. Role of complement

Cancer-related inflammation has been implicated in the promotion of gene instability [204], with evidence suggesting a role for complement activation. In a 3-MCA-induced mouse sarcoma model, complement activation was shown to increase the frequency of mutations in *Trp53*, a key gene involved in genomic stability, in the absence of the PTX3-mediated complement regulation via interaction with FH [74]. Chronic complement-driven inflammation may lead to the generation and accumulation of ROS and reactive nitrogen species (RNS) [63], both of which are mutagenic and accelerate the genetic evolution of mutant cells [205].

# 13. Unlocking phenotypic plasticity

## 13.1. Definition of the hallmark

During embryogenesis, undifferentiated progenitor cells proliferate and then differentiate to form tissues and organs. As cells differentiate, they acquire specific functions and lose their ability to proliferate. Cancer cells, originating from differentiated normal cells, can dedifferentiate back to a progenitor state to regain proliferative capacity. These progenitor cells are marked by their terminal differentiation phase and usually tend to differentiate again. However, cancer cells can block this process, maintaining a progenitor-like state. Additionally, a transdifferentiation mechanism allows differentiated cells to reprogram into a different differentiation status. This phenotypic plasticity supports tumor development and progression.
## 13.2. Role of complement

Both cell-autonomous expression of complement and anaphylatoxins have been implicated in this process. In physiological contexts, C5a can sustain human embryonic stem cell pluripotency [206,207]. In CRC, malignant cells exploit this C5a/C5aR1 axis to stabilize β-catenin, promoting colorectal tumorigenesis by activating the transcription of various oncogenes that enhance cancer cell stemness [160]. Similarly, the C3a/C3aR1 axis has also been shown to activate the β-catenin pathway, supporting stemness in cSCC cells [162]. Moreover, the cell-autonomous expression of complement proteins is also linked to cell stemness in cancer. For example, FH knockdown in breast cancer cells decreases the expression of stemness markers such as Oct4, Sox2 or c-Myc via modulation of the ERK and p38 signaling pathways [186]. Additionally, in HCC cell line, C7 or FH knockdown also downregulates the expression of stemness factors via LSF-1 [208].

# 14. Non-mutational epigenetic reprogramming

## 14.1. Definition of the hallmark

Non-mutational epigenetic reprogramming is an additional strategy used by transformed cells to acquire cancer hallmarks. Unlike mutations which alter the DNA sequence, epigenetic reprogramming modifies gene expression in malignant cells through mechanisms such as histone modifications, DNA methylations or non-coding RNA (ncRNA)-associated gene silencing. MicroRNAs (miRNAs) are endogenous ncRNA which can bind specific mRNA molecules and inhibit their translation. Circular RNAs (circRNAs) are a class of RNAs with a closed-loop structure, which originate from precursor mRNA through back-splicing or exon-skipping events. These circRNAs can act as miRNA sponges, which is a common regulatory mechanism in cancer [209].

### 14.1.1. Role of complement

#### 14.1.1.1. Cell fate regulation by complement genes-related circRNA.
Complement has been implicated in epigenetic reprogramming by facilitating histone modifications and regulating of ncRNA-associated gene silencing. A circRNA derived from the *CFH* gene (circ-CFH) has been found to promote malignant cell proliferation in a cancer-specific manner. In ovarian cancer, circ-CFH facilitates tumor progression by sponging the miRNA miR-942-5p, which targets *CUL4B*, involved in ovarian cancer cell proliferation [210]. In other cancers, the pro-tumoral effect of circ-CFH is linked to the sponging of miR-610 and miR-377-3p in HCC [211,212] and to the targeting of miR-149 in glioma [213].

#### 14.1.1.2. Cascade-unrelated intracellular functions.
Intracellular complement proteins can also affect epigenetic reprogramming. For example, intracellular C5aR1 signaling inhibits ferroptosis by promoting METTL3-dependent m6A methylation of glutathione peroxidase 4 (GPX4) mRNA through the activation of the ERK1/2 signaling pathway in glioblastoma. This modification stabilizes the expression of GPX4, a core anti-ferroptotic factor, thereby facilitating glioblastoma progression [214]. Additionally, C3b has been found to translocate to the nucleus of paclitaxel-resistant NSCLC cells, where it interacts with SIN3A/HDAC1/2 to form a repressor complex that represses *GADD45A* expression via histone deacetylation in its promoter region. As *GADD45A* participates in cell growth inhibition and apoptosis induction, its repression results in enhanced cell growth, reduced apoptosis and increased resistance to paclitaxel treatment [44].

#### 14.1.1.3. Regulators regulation by microRNA.
Complement regulation at the post-transcriptional level adds another layer of complexity to its role in tumor progression. Indeed, the expression of complement proteins can be controlled by mRNAs, though this regulation remains poorly

understood. MiR-150 expression enhance resistance to MAC-dependent cytotoxicity, while miR-328, and miR-616 reduce K562 cell resistance by modulating CD46 and CD59 expression [215]. In lung cancer models, EGFR/Wnt signaling induces β-catenin-mediated expression of the long noncoding RNA (lncRNA) LINC00973, which sponges CD55-targeting miR-216b and CD59-targeting miR-150 [117]. The consequently upregulated CD55/CD59 expression suppresses complement activation, ultimately promoting the progression of EGFR-mutant lung cancers.

# 15. Polymorphic microbiomes

## 15.1. Definition of the hallmark

The microbiota refers to the commensal or symbiotic microorganisms living on barrier tissues exposed to the external environment, such as the skin, lungs, gut, and urogenital system. This diverse community, comprising bacteria, viruses, fungi and parasites, has been linked to the promotion of hallmarks of cancer such as tumor inflammation [216]. The composition of the intra-tumor microbiota can shape the immune phenotype and tumor cell survival, consequently impacting treatment responses, particularly to immunotherapy.

### 15.2. Role of complement

The crosstalk between microbiome and complement on mucosal surfaces acts as a double-edge sword in cancer. On the one hand, research on the mycobiome in PDAC has revealed that *Malassezia* spp. fungi promote tumor progression through MBL-mediated complement activation [217], highlighting how microbiota-driven complement activation fuels pro-tumoral inflammation. On the other hand, gut microbiota regulates local complement production and the protection against pro-inflammatory pathogens [218]. Disruption of this balance could lead to pro-inflammatory microbiota dysbiosis and increased cancer risk. In this sense, the C3a/C3aR1 axis has been shown to prevent the establishment of pro-tumorigenic fecal microbiota in a spontaneous mouse model of CRC [219]. Therefore, while complement is implicated in the maintenance of a protective microbiota, its uncontrolled activation can also contribute to microbiota-driven tumor progression.

# 16. Senescent cells in the tumor

## 16.1. Definition of the hallmark

Senescence is an irreversible, viable state in which cells stop proliferating but remain metabolically active. It is marked by changes in cell morphology, metabolism, and the senescence-associated secretory phenotype (SASP), which involves the release of cytokines, chemokines and proteases. SASP turns senescent fibroblasts into proinflammatory cells that have the ability to promote tumor progression [220]. These secretions can activate surrounding tumor, stromal and immune cells, facilitating the acquisition of cancer hallmarks and thereby promoting tumor development and progression. Additionally, tumor cells have developed mechanisms to evade this non-proliferative state with the ability to re-enter the cell cycle following a senescence state.

### 16.2. Role of complement

Although little is known about the role of complement in senescence escape by cancer cells, a recent study has shown that FB production by PDAC cells can help bypassing cellular senescence in an autocrine manner, potentially enabling senescent PDAC cells to regain proliferative capacity [185]. Conversely, therapy-induced senescent cancer cell lines present increased C3 production, complement activation and exhibit increased CD59 and FH expression [221].
# 17. Nervous system's influence on tumor development and progression

Recent research has linked the nervous system to the induction of cancer hallmark capabilities, resulting in the introduction of neurons as hallmark-inducing constituents of the TME [5]. Autocrine and paracrine neuronal regulatory circuits appear to be aberrantly activated in tumors and hence may constitute a distinctive “enabling” characteristic that contributes to the manifestation of hallmark functions and consequent cancer pathogenesis.

## 17.1. Role of complement

How complement contributes to the co-opting of neuronal signaling circuits by cancer cells remains unknown. Nevertheless, in recent years, an ever-growing body of literature has linked complement to neuroprotection, neuronal plasticity and neuroinflammation [222]. Complement plays a crucial role in the nervous system, guiding neurodevelopmental processes like neural migration, cell proliferation, and synaptic pruning, as well as dendritic pruning in the adult brain, which contributes to memory “forgetting” [223]. However, when disrupted, complement activity is linked to severe neurological conditions, including epilepsy and schizophrenia [224]. Both complement cascade and cascade-unrelated intracellular functions of the complement proteins are involved in this process [46,225]. Therefore, the interplay between complement and neurons in cancer is a new and exciting field yet to be explored in the future.

# 18. Conclusion

The literature reviewed here illustrates how malignant cells can co-opt the complement system to drive critical processes involved in tumor progression, influencing nearly all hallmarks of cancer. First, we present evidence demonstrating how the canonical complement cascade, as a part of the innate immunity, contributes to the tumor-promoting chronic inflammation and immune evasion. While complement activation may initially contribute to the elimination of early tumor cells through MAC deposition, it could later promote tumor growth during the escape phase by selecting complement-resistant variants that overexpress complement regulators and sustain chronic inflammation. These complement regulators shield tumor cells from complement-mediated killing while still allowing for anaphylatoxin formation, which disrupts immune effector cells and promotes immunosuppression. Nonetheless, the complement cascade per se is not the only mechanism through which complement proteins contribute to the hallmarks of cancer. Equally important are their cascade-unrelated, non-canonical functions in the extracellular and intracellular spaces. A growing body of evidence suggests that complement proteins play crucial roles in proliferation, resistance to cell death, migration and metastases, as well as angiogenesis. However, the specific binding partners and molecular mechanisms are still poorly defined. Further research is needed to determine whether these processes are related to an intracellular complement system (complosome) or occur independently from the coordinated action of several intracellular complement proteins. Regardless of the underlying mechanisms, these non-canonical functions are described for most of the hallmarks of cancer and must be taken into account when analyzing the prognostic impact of complement gene overexpression in the TME, as well as during the design of complement-based therapeutics. New biomarkers should be developed to stratify patients depending on the predominant complement mechanism of action, allowing for the establishment of cancer type-specific complement scores [53]. Given the multifaceted role of complement—either suppressing or promoting tumor progression depending on context—along with its extracellular and intracellular mechanisms, it is essential to get deeper understanding on these processes in order to identify the most suitable complement-targeting drug

combinations and to design tailored clinical trials for either complement overactivation or inhibition, depending on the specific complement-tailored patient group.

# CRediT authorship contribution statement

**Roumenina Lubka T.:** Writing – review & editing, Writing – original draft, Visualization, Project administration, Data curation, Conceptualization. **Radanova Maria:** Writing – original draft, Visualization, Conceptualization. **Nedelcev Leon:** Visualization. **Minery Andrea:** Writing – review & editing, Writing – original draft, Visualization. **Artero Mikel Rezola:** Writing – review & editing, Writing – original draft, Visualization, Data curation, Conceptualization.

# Declaration of Competing Interest

LTR reports past consulting fees and research grants in the field of complement from Alexion, Commit Biologics, CSL Behring, Omeros, Pierre Fabre and Roche. The remaining authors declare no conflicts of interest.

# Acknowledgments

This work was supported by grants to LTR from: INCAPLBio program (INCa_16096 and INCa_19274), European Union program EP PerMed COMPACT project (ANR-24-EPPM-0008-02), the UPCite Emergence grant (ANR-18-IDEX-0001), Canceropole (n°2023-1-EMERG-10-INSERM IDF CENTRE EST-1), PHC RILA 2024 (N° 51262QG), Fondation pour la Recherche Médicale FRM team label FRM: EQU202503020008, Association Robert Debré for medical research (ARDRM) award for basic research, and the SVAR Complement Excellence Award by European Complement Network. It is supported also by grants to MR from: European Union-NextGenerationEU, through the National Recovery and Resilience Plan of the Republic of Bulgaria, project Nº BG-RRP-2.004-0009-C02 and by the Medical University of Varna, Bulgaria (Grant number FS-52/18 July 2024). This work is also supported by INSERM, by Université de Paris Cité, and by Sorbonne Université. MRA was supported by funds of the EU MSCA project CORVOS 860044. All figures are original and are created with Biorender.

# Data availability

No data was used for the research described in the article.

# References

[1] D. Hanahan, R.A. Weinberg, The hallmarks of cancer, Cell 100 (1) (2000) 57-70.

[2] D. Hanahan, R.A. Weinberg, Hallmarks of cancer: the next generation, Cell 144 (5) (2011) 646-674.

[3] D. Hanahan, Rethinking the war on cancer, Lancet 383 (9916) (2014) 558-563.

[4] D. Hanahan, Hallmarks of Cancer: New Dimensions, Cancer Discov. 12 (1) (2022) 31-46.

[5] D. Hanahan, M. Monje, Cancer hallmarks intersect with neuroscience in the tumor microenvironment, Cancer Cell 41 (3) (2023) 573-580.

[6] C. Swanton, E. Bernard, C. Abbosh, F. André, J. Auwerx, A. Balmain, D. Bar-Sagi, R. Bernards, S. Bullman, J. DeGregori, C. Elliott, A. Erez, G. Evan, M.A. Febbraio, A. Hidalgo, M. Jamal-Hanjani, J.A. Joyce, M. Kaiser, K. Lamia, J.W. Locasale, S. Loi, I. Malanchi, M. Merad, K. Musgrave, K.J. Patel, S. Quezada, J.A. Wargo, A. Weeraratna, E. White, F. Winkler, J.N. Wood, K.H. Vousden, D. Hanahan, Embracing cancer complexity: Hallmarks of systemic disease, Cell 187 (7) (2024) 1589-1616.

[7] D. Mittal, M.M. Gubin, R.D. Schreiber, M.J. Smyth, New insights into cancer immunoediting and its three component phases—elimination, equilibrium and escape, Curr. Opin. Immunol. 27 (2014) 16-25.

[8] G.P. Dunn, L.J. Old, R.D. Schreiber, The three Es of cancer immunoediting, Annu Rev. Immunol. 22 (2004) 329-360.

[9] C. Galassi, T.A. Chan, I. Vitale, L. Galluzzi, The hallmarks of cancer immune evasion, Cancer Cell 42 (11) (2024) 1825-1863.

[10] E.E. West, C. Kemper, Complosome - the intracellular complement system, Nat. Rev. Nephrol. 19 (7) (2023) 426-439.

[11] B.C. King, A.M. Blom, Intracellular complement: evidence, definitions, controversies, and solutions, Immunol. Rev. 313 (1) (2023) 104-119.
[12] D. Ricklin, G. Hajishengallis, K. Yang, J.D. Lambris, Complement: a key system for immune surveillance and homeostasis, Nat. Immunol. 11 (9) (2010) 785-797.

[13] N.S. Merle, S.E. Church, V. Fremeaux-Bacchi, L.T. Roumenina, Complement system part I - molecular mechanisms of activation and regulation, Front Immunol. 6 (2015) 262.

[14] G. Hajishengallis, E.S. Reis, D.C. Mastellos, D. Ricklin, J.D. Lambris, Novel mechanisms and functions of complement, Nat. Immunol. 18 (12) (2017) 1288-1298.

[15] G. Bajic, S.E. Degn, S. Thiel, G.R. Andersen, Complement activation, regulation, and molecular basis for complement-related diseases, EMBO J. 34 (22) (2015) 2735-2757.

[16] R. Lubbers, M.F. van Essen, C. van Kooten, L.A. Trouw, Production of complement components by cells of the immune system, Clin. Exp. Immunol. 188 (2) (2017) 183-194.

[17] B.C. King, A.M. Blom, Intracellular complement and immunometabolism: the advantages of compartmentalization, Eur. J. Immunol. 54 (8) (2024) e2350813.

[18] M.K. Liszewski, M. Kolev, G. Le Friec, M. Leung, P.G. Bertram, A.F. Fara, M. Subias, M.C. Pickering, C. Drouet, S. Meri, T.P. Arstila, P.T. Pekkarinen, M. Ma, A. Cope, T. Reinheckel, S. Rodriguez de Cordoba, B. Afzali, J.P. Atkinson, C. Kemper, Intracellular complement activation sustains T cell homeostasis and mediates effector differentiation, Immunity 39 (6) (2013) 1143-1157.

[19] R.A. Franklin, W. Liao, A. Sarkar, M.V. Kim, M.R. Bivand, K. Liu, E.G. Pamer, M. O. Li, The cellular and molecular origin of tumor-associated macrophages, Science 344 (6186) (2014) 921-925.

[20] G. Arbore, E.E. West, R. Spolski, A.A.B. Robertson, A. Klos, C. Rheinheimer, P. Dutow, T.M. Woodruff, Z.X. Yu, L.A. O'Neill, R.C. Coll, A. Sher, W.J. Leonard, J. Kohl, P. Monk, M.A. Cooper, M. Arno, B. Afzali, H.J. Lachmann, A.P. Cope, K. D. Mayer-Barber, C. Kemper, T helper 1 immunity requires complement-driven NLRP3 inflammasome activity in CD4(+) T cells, Science 352 (6292) (2016) aad1210.

[21] M. Elvington, M.K. Liszewski, P. Bertram, H.S. Kulkarni, J.P. Atkinson, A C3(H20) componenting pathway is a component of the intracellular complement system, J. Clin. Invest. 127 (3) (2017) 970-981.

[22] M. Kolev, S. Dimeloe, G. Le Friec, A. Navarin, G. Arbore, G.A. Povoleri, M. Fischer, R. Belle, J. Loeliger, L. Develioglu, G.R. Bantug, J. Watson, L. Couzi, B. Afzali, P. Lavender, C. Hess, C. Kemper, Complement regulates nutrient influx and metabolic reprogramming during Th1 cell responses, Immunity 42 (6) (2015) 1033-1047.

[23] M. Kolev, E.E. West, N. Kunz, D. Chauss, E.A. Moseman, J. Rahman, T. Freiwald, M.L. Balmer, J. Lotscher, S. Dimeloe, E.C. Rosser, L.R. Wedderburn, K.D. Mayer-Barber, A. Bohrer, P. Lavender, A. Cope, L. Wang, M.J. Kaplan, N. M. Moutopoulos, D. McGavern, S.M. Holland, C. Hess, M. Kazemian, B. Afzali, C. Kemper, Diapedesis-induced integrin signaling via LFA-1 facilitates tissue immunity by inducing intrinsic complement C3 expression in immune cells, Immunity 52 (3) (2020) 513-527, e8.

[24] G. Arbore, E.E. West, J. Rahman, G. Le Friec, N. Niyozima, M. Pirooznia, I. Tunc, P. Pavlidis, N. Powell, Y. Li, P. Liu, A. Servais, L. Couzi, V. Fremeaux-Bacchi, L. Placais, A. Ferraro, P.R. Walsh, D. Kavanagh, B. Afzali, P. Lavender, H. J. Lachmann, C. Kemper, Complement receptor CD46 co-stimulates optimal human CD8(+) T cell effector function via fatty acid metabolism, Nat. Commun. 9 (1) (2018) 4186.

[25] G.S. Ling, G. Crawford, N. Buang, I. Bartok, K. Tian, N.M. Thielens, I. Bally, J. A. Harker, P.G. Ashton-Rickardt, S. Rutschmann, J. Strid, M. Botto, C1q restrains autoimmunity and viral infection by regulating CD8(+) T cell metabolism, Science 360 (6388) (2018) 558-563.

[26] M.T. Sorbara, E.G. Foerster, J. Tsalikis, M. Abdel-Nour, J. Mangiapane, I. Sirluck-Schroeder, I. Tattoli, R. van Dalen, D.E. Isenman, J.R. Rohe, S.E. Girardin, D. J. Philpott, Complement C3 drives autophagy-dependent restriction of cyto-invasive bacteria, Cell Host Microbe 23 (5) (2018) 644-652.

[27] B.C. King, K. Kulak, U. Krus, R. Rosberg, E. Golec, K. Wozniak, M.F. Gomez, E. Zhang, D.J. O'Connell, E. Renstrom, A.M. Blom, Complement component C3 is highly expressed in human pancreatic islets and prevents beta cell death via ATG16L1 interaction and autophagy regulation, Cell Metab. 29 (1) (2019) 202-210, e6.

[28] B.C. King, E. Renstrom, A.M. Blom, Intracellular cytosolic complement component C3 regulates cytoprotective autophagy in pancreatic beta cells by interaction with ATG16L1, Autophagy 15 (5) (2019) 919-921.

[29] M.M. Olcina, R.K. Kim, N.G. Balanis, C.G. Li, R. von Eyben, T.G. Graeber, D. Ricklin, M. Stucki, A.J. Giaccia, C.R. C4BPA levels regulate NF-kappaB-dependent apoptosis, iScience 23 (10) (2020) 101594.

[30] Y. Li, Y. Sha, H. Wang, L. He, L. Li, S. Wen, L. Sheng, W. Hu, H. Zhou, Intracellular C3 prevents hepatic steatosis by promoting autophagy and very-low-density lipoprotein secretion, FASEB J. 35 (12) (2021) e22037.

[31] M.V. Daugan, M. Revel, J. Russick, M.A. Dragon-Durey, C. Gaboriaud, T. Robe-Rybkine, V. Poillerat, A. Grunenwald, G. Lacroix, A. Bougouin, M. Meylan, V. Verkarre, S.M. Oudard, A. Mejean, Y.A. Vano, G. Perkins, P. Validire, X. Cathelineau, R. Sanchez-Salas, D. Damotte, V. Fremeaux-Bacchi, I. Cremer, C. Sautes-Fridman, W.H. Fridman, L.T. Roumenina, Complement C1s and C4d as prognostic biomarkers in renal cancer: emergence of noncanonical functions of C1s, Cancer Immunol. Res 9 (8) (2021) 891-908.

[32] M.V. Daugan, M. Revel, J. Thouenon, M.A. Dragon-Durey, T. Robe-Rybkine, C. Torset, N.S. Merle, R. Noe, V. Verkarre, S.M. Oudard, A. Mejean, P. Validire, X. Cathelineau, R. Sanchez-Salas, M.C. Pickering, I. Cremer, A. Mansuet-Lupo, M. Alifano, C. Sautes-Fridman, D. Damotte, W.H. Fridman, L.T. Roumenina, Intracellular factor H drives tumor progression independently of the complement cascade, Cancer Immunol. Res 9 (8) (2021) 909-925.

[33] M. Ishii, G. Beeson, C. Beeson, B. Rohrer, Mitochondrial C3a receptor activation in oxidatively stressed epithelial cells reduces mitochondrial respiration and metabolism, Front Immunol. 12 (2021) 628062.

[34] A. Armento, T.L. Schmidt, I. Sonntag, D.A. Merle, M.A. Jarboui, E. Kilger, S. J. Clark, M. Ueffing, CFH loss in human RPE cells leads to inflammation and complement system dysregulation via the NF-kappaB pathway, Int J. Mol. Sci. 22 (16) (2021).

[35] S. Mahajan, A. Jacob, A. Kelkar, A. Chang, D. McSkimming, S. Neelamegham, R. J. Quigg, J.J. Alexander, Local complement factor H protects kidney endothelial cell structure and function, Kidney Int 100 (4) (2021) 824-836.

[36] D.A. Merle, F. Provenzano, M.A. Jarboui, E. Kilger, S.J. Clark, M. Deleidi, A. Armento, M. Ueffing, mTOR inhibition via rapamycin treatment partially reverts the deficit in energy metabolism caused by FH Loss in RPE cells, Antioxidants 10 (12) (2021).

[37] B. Yan, T. Freiwald, D. Chauss, L. Wang, E. West, C. Mirabelli, C.J. Zhang, E. M. Nichols, N. Malik, R. Gregory, M. Bantscheff, S. Ghidelli-Disse, M. Kolev, T. Frum, J.R. Spence, J.Z. Sexton, K.D. Alysandratos, D.N. Kotton, S. Pittaluga, J. Bibby, N. Niyozima, M.R. Olson, S. Kordasti, D. Portilla, C.E. Wobus, A. Laurence, M.S. Lionakis, C. Kemper, B. Afzali, M. Kazemian, SARS-CoV-2 drives JAK1/2-dependent local complement hyperactivation, Sci. Immunol. 58 (58) (2021) eabg0833.

[38] N. Niyozima, J. Rahman, N. Kunz, E.E. West, T. Freiwald, J.V. Desai, N.S. Merle, A. Gidon, B. Sporsheim, M.S. Lionakis, K. Evensen, B. Lindberg, K. Skagen, M. Skjelland, P. Singh, M. Haug, M.M. Ruseva, M. Kolev, J. Bibby, O. Marshall, B. O'Brien, N. Deeks, B. Afzali, R.J. Clark, T.M. Woodruff, M. Pryor, Z.H. Yang, A. T. Remaley, T.E. Mollnes, S.M. Hewitt, B. Yan, M. Kazemian, M.G. Kiss, C. J. Binder, B. Halvorsen, T. Espevik, C. Kemper, Mitochondrial C5AR1 activity in macrophages controls IL-1beta production underlying sterile inflammation, Sci. Immunol. 6 (6) (2021) eabf2489.

[39] J. Friscic, M. Bottcher, C. Reinwald, H. Bruns, B. Wirth, S.J. Popp, K.I. Walker, J. A. Ackermann, X. Chen, J. Turner, H. Zhu, L. Seyler, M. Euler, P. Kirchner, R. Kruger, A.B. Ekici, T. Major, O. Aust, D. Weidner, A. Fischer, F.T. Andes, Z. Stanojevic, V. Trajkovic, M. Herrmann, A. Korb-Pap, I. Wank, A. Hess, J. Winter, V. Wixler, J. Distler, G. Steiner, H.P. Kiener, B. Frey, L. Kling, R. Kaza, S. Frey, A. Kleyer, T. Bauerle, T.R. Hughes, A. Gruneboom, U. Steffen, G. Kronke, A.P. Croft, A. Filer, J. Kohl, K. Klein, C.D. Buckley, G. Schett, D. Mougiakakos, M. H. Hoffmann, The complement system drives local inflammatory tissue priming by metabolic reprogramming of synovial fibroblasts, Immunity 54 (5) (2021) 1002-1021, e10.

[40] M. Kremlitzka, L. Colineau, A.A. Nowacka, F.C. Mohlin, K. Wozniak, A.M. Blom, B.C. King, Alternative translation and retrotranslocation of cytosolic C3 that detects cytoinvasive bacteria, Cell Mol. Life Sci. 79 (6) (2022) 291.

[41] E. Golec, A. Ekstrom, M. Noga, M. Omar-Hmeadi, P.E. Lund, B.O. Villoutreix, U. Krus, K. Wozniak, O. Korsgren, E. Renstrom, S. Barg, B.C. King, A.M. Blom, Alternative splicing encodes functional intracellular CD59 isoforms that mediate insulin secretion and are down-regulated in diabetic islets, Proc. Natl. Acad. Sci. USA 119 (22) (2022) e2120083119.

[42] Z.J. Sun, D.Y. Chang, M. Chen, M.H. Zhao, Deficiency of CFB attenuates renal tubulointerstitial damage by inhibiting ceramide synthesis in diabetic kidney disease, JCI Insight 7 (24) (2022) e156748.

[43] A.H. Janneh, M.F. Kassir, F.C. Atilgan, H.G. Lee, M. Sheridan, N. Oleinik, Z. Szulc, C. Voelkel-Johnson, H. Nguyen, H. Li, Y.K. Peterson, E. Marangoni, O. Saatci, O. Sahin, M. Lilly, C. Atkinson, S. Tomlinson, S. Mehrotra, B. Ogretmen, Crosstalk between pro-survival sphingolipid metabolism and complement signaling induces inflammasome-mediated tumor metastasis, Cell Rep. 41 (10) (2022) 111742.

[44] W. Wang, Y. Hao, J. Chen, P. Ding, X. Lv, D. Zhou, L. Li, L. Li, Y. Xu, Y. Zhu, W. Zhang, L. Chen, T. Liao, X. He, Q.H. Ji, W. Hu, Nuclear complex C3b promotes placitaxil resistance by assembling the SIN3A/HDAC1/2 complex in non-small cell lung cancer, Cell Death Dis. 14 (6) (2023) e351.

[45] K. Kulak, K. Kuska, L. Colineau, M. McKay, K. Maziarz, J. Slaby, A.M. Blom, B. C. King, Intracellular C3 protects beta-cells from IL-1beta-driven cytotoxicity via interaction with Fyn-related kinase, Proc. Natl. Acad. Sci. USA 121 (8) (2024) e2312621121.

[46] N. Scott-Hewitt, M. Mahoney, Y. Huang, N. Korte, T. Yvanka de Soysa, D. K. Wilton, E. Knorr, K. Mastro, A. Chang, A. Zhang, D. Melville, M. Schenone, C. Hartigan, B. Stevens, Microglial-derived C1q integrates into neuronal ribonucleoprotein complexes and impacts protein homeostasis in the aging brain, Cell 187 (16) (2024) 4193-4212, e24.

[47] S.K. Sahu, A.N. Ozanturk, D.H. Kulkarni, L. Ma, R.A. Barve, L. Dannull, A. Lu, M. Starick, J. McPhatter, L. Garnica, M. Sanfillipo-Burchman, J. Kunen, X. Wu, A. E. Gelman, S.L. Brody, J.P. Atkinson, H.S. Kulkarni, Lung epithelial cell-derived C3 protects against pneumonia-induced lung injury, Sci. Immunol. 8 (80) (2023) eabp9547.

[48] H.S. Kulkarni, M.L. Elvington, Y.C. Perng, M.K. Liszewski, D.E. Byers, C. Farkouh, R.D. Yusen, D.J. Lenschow, S.L. Brody, J.P. Atkinson, Intracellular C3 Protects Human Airway Epithelial Cells from Stress-associated Cell Death, Am. J. Respir. Cell Mol. Biol. 60 (2) (2019) 144-157.

[49] M.G. Kiss, N. Papac-Milicevic, F. Porsch, D. Tsiantoulas, T. Hendrikx, M. Takaoka, H.Q. Dinh, M.S. Narzt, L. Goderle, M. Ozsvar-Kozma, M. Schuster, M. Fortelnay, A. Hladik, S. Knapp, F. Gruber, M.C. Pickering, C. Bock, F.K. Swirski, K. Ley, A. Zelecka, C. Cochain, C. Kemper, Z. Mallat, C.J. Binder, Cell-autonomous regulation of complement C3 by factor H limits macrophage effectorcytosis and exacerbates atherosclerosis, Immunity 56 (8) (2023) 1809-1824, e10.

[50] E. Golec, R. Olsson, E.C. Tuysuz, M. Karlsson, Y. Serjieh, B.C. King, M. Wennstrom, A.M. Blom, Neuronal CD59 isoforms IRIS-1 and IRIS-2 as
regulators of neurotransmitter release with implications for Alzheimer's disease, Alzheimers Res Ther. 17 (1) (2025) 11.

[51] R. Rosberg, K.I. Smolag, J. Sjolund, E. Johansson, C. Bergelin, J. Wahlden, V. Pantazopoulou, C. Ceberg, K. Pietras, A.M. Blom, A. Pietras, Hypoxia-induced complement component 3 promotes aggressive tumor growth in the glioblastoma microenvironment, JCI Insight 9 (19) (2024).

[52] A. Mangogna, C. Agostinis, D. Bonazza, B. Belmonte, P. Zacchi, G. Zito, A. Romano, F. Zanconati, G. Ricci, U. Kishore, R. Bulla, Is the complement protein C1q a pro- or anti-tumorigenic factor? bioinformatics analysis involving human carcinomas, Front Immunol. 10 (2019) 865.

[53] A. Balduit, C. Agostinis, R. Bulla, Beyond the Norm: The emerging interplay of complement system and extracellular matrix in the tumor microenvironment, Semin. Immunol. 77 (2025) 101929.

[54] K.I. Smolag, J. Olszowka, R. Rosberg, E. Johansson, E. Marinko, K. Leandersson, D.J. O'Connell, V. Governa, E.C. Tuysuz, M. Belting, A. Pietras, M. Martin, A. M. Blom, Complement factor H is an ICOS ligand modulating tregs in the glioma microenvironment, Cancer Immunol. Res 13 (1) (2025) 122-138.

[55] B. Ghebrehiwet, K.H. Hoszu, E.I. Peerschke, C1q as an autocrine and paracrine regulator of cellular functions, Mol. Immunol. 84 (2017) 26-33.

[56] M. Son, F. Santiago-Schwarz, Y. Al-Abed, B. Diamond, C1q limits dendritic cell differentiation and activation by engaging LAIR-1, Proc. Natl. Acad. Sci. USA 109 (46) (2012) E3160-7.

[57] P. Garred, N. Genster, K. Pilely, R. Bayarri-Olmos, A. Rosberg, Y.J. Ma, M. O. Skjoedt, A journey through the lectin pathway of complement-MBL and beyond, Immunol. Rev. 274 (1) (2016) 74-97.

[58] Y. Wang, S.N. Sun, Q. Liu, Y.Y. Yu, J. Guo, K. Wang, B.C. Xing, Q.F. Zheng, M. J. Campa, E.F. Patz Jr., S.Y. Li, Y.W. He, Autocrine complement inhibits IL10-dependent T-cell-mediated antitumor immunity to promote tumor progression, Cancer Discov. 6 (9) (2016) 1022-1035.

[59] C.A. Ogden, A. deCathelineau, P.R. Hoffmann, D. Bratton, B. Ghebrehiwet, V. A. Fadok, P.M. Henson, C1q and mannose binding lectin engagement of cell surface calreticulin and CD91 initiates macropinocytosis and uptake of apoptotic cells, J. Exp. Med 194 (6) (2001) 781-795.

[60] E.S. Reis, D.C. Mastellos, D. Ricklin, A. Mantovani, J.D. Lambris, Complement in cancer: untangling an intricate relationship, Nat. Rev. Immunol. 18 (1) (2018) 5-18.

[61] D. Ajona, S. Ortiz-Espinosa, H. Moreno, T. Lozano, M.J. Pajares, J. Agorreta, C. Bertolo, J.J. Lasarte, S. Vicent, K. Hoehlig, A. Vater, F. Lecanda, L. M. Montuenga, R. Pio, A combined PD-1/C5a blockade synergistically protects against lung cancer growth and metastasis, Cancer Discov. 7 (7) (2017) 694-703.

[62] X. Han, H. Zha, F. Yang, B. Guo, B. Zhu, Tumor-derived tissue factor aberrantly activates complement and facilitates lung tumor progression via recruitment of myeloid-derived suppressor cells, Int J. Mol. Sci. 18 (1) (2017).

[63] M.M. Markiewski, R.A. DeAngelis, F. Benencia, S.K. Ricklin-Lichtsteiner, A. Koutoulaki, C. Gerard, G. Coukos, J.D. Lambris, Modulation of the antitumor immune response by complement, Nat. Immunol. 9 (11) (2008) 1225-1235.

[64] S.K. Vadrevu, N.K. Chintala, S.K. Sharma, P. Sharma, C. (2008) 1225-1235.
S. Manne, D.P. Fairlie, W. Gorczyca, O. Almanza, M. Karbowniczek, M. M. Markiewski, Complement c5a receptor facilitates cancer metastasis by altering T-cell responses in the metastatic niche, Cancer Res 74 (13) (2014) 3454-3465.

[65] B.E. Hsu, J. Roy, J. Mouhanna, R.F. Rayes, T. Ramsay, S. Tabaries, M.G. Annis, I. R. Watson, J.D. Spicer, S. Costantino, P.M. Siegel, C3a elicits unique migratory responses in immature low-density neutrophils, Oncogene 39 (12) (2020) 2612-2623.

[66] S. Guglietta, A. Chiavelli, E. Zagato, C. Krieg, S. Gandini, P.S. Ravenda, B. Bazolli, B. Lu, G. Penna, M. Rescigno, Coagulation induced by C3aR-dependent NETosis drives protumorigenic neutrophils during small intestinal tumorigenesis, Nat. Commun. 7 (2016) 11037.

[67] J.W. Kwak, J. Laskowski, H.Y. Li, M.V. McSharry, T.R. Sippel, B.L. Bullock, A. M. Johnson, J.M. Poczobutt, A.J. Neuwelt, S.P. Malkoski, M.C. Weiser-Evans, J. D. Lambris, E.T. Clambe, J.M. Thurman, R.A. Nemenoff, Complement activation via a C3a receptor pathway alters CD4(+) T lymphocytes and mediates lung cancer progression, Cancer Res 78 (1) (2018) 143-156.

[68] E. Magrini, S. Di Marco, S.N. Mapelli, C. Perucchi, F. Pasqualini, A. Donato, M. L. Guevara Lopez, R. Carriero, A. Ponzetta, P. Colombo, F. Cananzi, D. Supino, E. S. Reis, C. Peano, A. Inforzato, S. Jaillon, A. Doni, J.D. Lambris, A. Mantovani, C. Garlanda, Complement activation promoted by the lectin pathway mediates C3aR-dependent sarcoma progression and immunosuppression, Nat. Cancer 2 (2) (2021) 218-232.

[69] T.R. Medler, D. Murugan, W. Horton, S. Kumar, T. Cotechini, A.M. Forsyth, P. Leyshock, J.J. Leitenberger, M. Kulesz-Martin, A.A. Margolin, Z. Web, L. M. Coussens, Complement C5a fosters squamous carcinogenesis and limits T cell response to chemotherapy, Cancer Cell 34 (4) (2018) 561-578, e6.

[70] C. Piao, W.M. Zhang, T.T. Li, C.C. Zhang, S. Qiu, Y. Liu, S. Liu, M. Jin, L.X. Jia, W. C. Song, J. Du, Complement 5a stimulates macrophage polarization and contributes to tumor metastases of colon cancer, Exp. Cell Res 366 (2) (2018) 127-138.

[71] H. Zha, X. Wang, Y. Zhu, D. Chen, X. Han, F. Yang, J. Gao, C. Hu, C. Shu, Y. Feng, Y. Tan, J. Zhang, Y. Li, Y.Y. Wan, B. Guo, B. Zhu, Intracellular activation of complement C3 leads to PD-L1 antibody treatment resistance by modulating tumor-associated macrophages, Cancer Immunol. Res 7 (2) (2019) 193-207.

[72] Y. Zhang, Y. Song, X. Wang, M. Shi, Y. Lin, D. Tao, S. Han, An NFAT1-C3a-C3aR positive feedback loop in tumor-associated macrophages promotes a glioma stem cell malignant phenotype, Cancer Immunol. Res 12 (3) (2024) 363-376.

[73] J.A. Nabizadeh, H.D. Manthey, F.J. Steyn, W. Chen, A. Widiapradja, F.N. Md Akhir, G.M. Boyle, S.M. Taylor, T.M. Woodruff, B.E. Rolfe, The complement C3a

receptor contributes to melanoma tumorigenesis by inhibiting neutrophil and CD4+ T cell responses, J. Immunol. 196 (11) (2016) 4783-4792.

[74] E. Bonavita, S. Gentile, M. Rubino, V. Maina, R. Papait, P. Kunderfranco, C. Greco, F. Feruglio, M. Molgora, I. Laface, S. Tartari, A. Doni, F. Pasqualini, E. Barbati, G. Basso, M.R. Galdiero, M. Nebuloni, R. Moncalli, P. Colombo, L. Laghi, J.D. Lambris, S. Jaillon, C. Garlanda, A. Mantovani, PTX3 is an extrinsic oncosuppressor regulating complement-dependent inflammation in cancer, Cell 160 (4) (2015) 700-714.

[75] C. Beach, D. MacLean, D. Majorova, S. Melemenidis, D.K. Nambiar, R.K. Kim, G. N. Valbuena, S. Guglietta, C. Krieg, M. Darvish-Mavandavi, T. Suwa, A. Easton, L. V. Hillson, A.K. McCulloch, R.K. McMahon, K. Pennel, J. Edwards, S.M. O'Cathail, C.S. Roxburgh, E. Domingo, E.J. Moon, D. Jiang, Y. Jiang, Q. Zhang, A.C. Koong, T.M. Woodruff, E.E. Graves, T. Maughan, S.J. Buczacki, M. Stucki, Q.T. Le, S. J. Leedham, A.J. Giaccia, M.M. Olcina, Improving radiotherapy in immunosuppressive microenvironments by targeting complement receptor C5aR1, J. Clin. Invest 133 (23) (2023).

[76] Q.H. Sodji, D.K. Nambiar, V. Viswanathan, R. von Eyben, D. Colburg, M. S. Binkley, C.G. Li, M.M. Olcina, D.T. Chang, Q.T. Le, A.J. Giaccia, The combination of radiotherapy and complement C3a inhibition potentiates natural killer cell functions against pancreatic cancer, Cancer Res Commun. 2 (7) (2022) 725-738.

[77] K.S.W. Lee, Q. Zhang, T. Suwa, H. Clark, M.M. Olcina, The role of the complement system in the response to cytotoxic therapy, Semin. Immunol. 77 (2025) 101927.

[78] C. Zhang, K. Cao, M. Yang, Y. Wang, M. He, J. Lu, Y. Huang, G. Zhang, H. Liu, C5aR1 blockade reshapes immunosuppressive tumor microenvironment and synergizes with immune checkpoint blockade therapy in high-grade serous ovarian cancer, Oncoimmunology 12 (1) (2023) 2261242.

[79] N.S. Merle, L.T. Roumenina, The complement system as a target in cancer immunotherapy, Eur. J. Immunol. 54 (10) (2024) e2350820.

[80] Y. Senent, A. Remírez, D. Repáraz, D. Llopiz, D.P. Celias, C. Sainz, R. Entrialgo-Cadierno, L. Suarez, A. Rouzaut, D. Alignani, P. Tavira, J.D. Lambris, T. M. Woodruff, C.E. de Andrea, B. Ruffell, P. Sarobea, D. Ajona, R. Pio, The C5a/C5aR1 axis promotes migration of tolerogenic dendritic cells to lymph nodes, impairing the anticancer immune response, Cancer Immunol. Res. (2024).

[81] T.R. Emmons, T. Giridharan, K.L. Singel, A.N.H. Khan, J. Ricciuti, K. Howard, S. L. Silva-Del Toro, I.L. Debreceni, C.E.M. Aarts, M.C. Brouwer, S. Suzuki, T. W. Kuijpers, I. Jongerius, L.H. Allen, V.P. Ferreira, A. Schubart, H. Sellner, J. Eder, S.M. Holland, S. Ram, J.A. Lederer, K.H. Eng, K.B. Moysich, K. Odunsi, M. B. Yaffe, E. Zisros, B.H. Segal, Mechanisms driving neutrophil-induced T-cell immunoparalysis in ovarian cancer, Cancer Immunol. Res 9 (7) (2021) 790-810.

[82] K.L. Singel, T.R. Emmons, A.N.H. Khan, P.C. Mayor, S. Shen, J.T. Wong, K. Morrell, K.H. Eng, J. Mark, R.B.ankert, J. Matsuzaki, R.C. Koya, A.M. Blom, K.R. McLeish, J. Qu, S. Ram, K.B. Moysich, S.I. Abrams, K. Odunsi, E. Zisros, B. H. Segal, Mature neutrophils suppress T cell immunity in ovarian cancer microenvironment, JCI Insight 4 (5) (2019).

[83] P. Ding, L. Li, L. Li, X. Lv, D. Zhou, Q. Wang, J. Chen, C. Yang, E. Xu, W. Dai, X. Zhang, N. Wang, Q. Wang, W. Zhang, L. Wang, Y. Zhou, H. Gu, Q. Lei, X. Zhou, W. Hu, C5aR1 is a master regulator in Colorectal Tumorigenesis via Immune modulation, Theranostics 10 (19) (2020) 8619-8632.

[84] J. Laskowski, B. Renner, M.C. Pickering, N.J. Serkova, P.M. Smith-Jones, E. T. Clambey, R.A. Nemenoff, J.M. Thurman, Complement factor H-deficient mice develop spontaneous hepatic tumors, J. Clin. Invest 130 (8) (2020) 4039-4054.

[85] L. Gunn, C. Ding, M. Liu, Y. Ma, C. Qi, Y. Cai, X. Hu, D. Aggarwal, H.G. Zhang, J. Yan, Opposing roles for complement component C5a in tumor progression and the tumor microenvironment, J. Immunol. 189 (6) (2012) 2985-2994.

[86] D. Ajona, M.S. Cragg, R. Pio, The complement system in clinical oncology: applications, limitations and challenges, Semin. Immunol. 77 (2025) 101921.

[87] N.S. Merle, R. Noe, L. Halbwachs-Mecarelli, V. Fremeaux-Bacchi, L. T. Roumenina, Complement system part II: role in immunity, Front Immunol. 6 (2015) 257.

[88] A. Menny, M. Serna, C.M. Boyd, S. Gardner, A.P. Joseph, B.P. Morgan, T. Topf, N. J. Brooks, D. Bubeck, CryoEM reveals how the complement membrane attack complex ruptures lipid bilayers, Nat. Commun. 9 (1) (2018) 5316.

[89] Z. Fishelson, M. Kirschfink, Complement C5b-9 and cancer: mechanisms of cell damage, cancer counteractions, and approaches for intervention, Front Immunol. 10 (2019) 752.

[90] G. Kroemer, L. Galluzzi, O. Kepp, L. Zitvogel, Immunogenic cell death in cancer therapy, Annu Rev. Immunol. 31 (2013) 51-72.

[91] G. Kroemer, C. Galassi, L. Zitvogel, L. Galluzzi, Immunogenic cell stress and death, Nat. Immunol. 23 (4) (2022) 487-500.

[92] V. Ovcinnikovs, K. Dijkman, G.G. Zom, F.J. Beurskens, L.A. Trouw, Enhancing complement activation by therapeutic anti-tumor antibodies: mechanisms, strategies, and engineering approaches, Semin Immunol. 77 (2025) 101922.

[93] R. Saxena, R.T. Bushey, M.J. Campa, E.B. Gottlin, J. Guo, E.F. Patz Jr., Y.-W. He, Promotion of an antitumor immune program by a tumor-specific, complement-activating antibody, J. Immunol. 212 (10) (2024) 1589-1601.

[94] R.T. Bushey, R. Saxena, M.J. Campa, E.B. Gottlin, Y.-W. He, E.F. Patz, Jr., Antitumor immune mechanisms of the anti-complement factor H antibody GT103, Mol. Cancer Ther. 22 (6) (2023) 7789-7789.

[95] J.M. Clarke, G.R. Simon, H. Mamdani, L. Gu, J.E. Herndon, T.E. Stinchcombe, N. Ready, J. Crawford, G. Sonpavde, S. Balevic, A.B. Nixon, M. Campa, E. B. Gottlin, H. Li, R. Saxena, Y.W. He, S. Antonia, E.F. Patz Jr., Complement factor H targeting antibody GT103 in refractory small non-small cell lung cancer: a phase 1b dose escalation trial, Nat. Commun. 16 (1) (2025) 93.
[96] R. Saxena, E.B. Gottlin, M.J. Campa, Y.-W. He, E.F. Patz Jr., Complement regulators as novel targets for anti-cancer therapy: a comprehensive review, Semin. Immunol. 77 (2025) 101931.

[97] M. Huber-Lang, K.N. Ekdahl, R. Wiegner, K. Fromell, B. Nilsson, Auxiliary activation of the complement system and its importance for the pathophysiology of clinical conditions, Semin Immunopathol. 40 (1) (2018) 87–102.

[98] F. Lan, J. Li, W. Miao, F. Sun, S. Duan, Y. Song, J. Yao, X. Wang, C. Wang, X. Liu, J. Wang, L. Zhang, H. Qi, GZMK-expressing CD8(+) T cells promote recurrent airway inflammatory diseases, Nature 638 (8050) (2025) 490–498.

[99] C.A. Donado, E. Theisen, F. Zhang, A. Nathan, M.L. Fairfield, K.V. Rupani, D. Jones, K.P. Johannes, R.A.S.L.E.N. Accelerating, 2025, C.A. Donado, E. Theisen, F. Zhang, A. Nathan, M.L. Fairfield, K.V. Rupani, D. Jones, K.P. Johannes, R.A.S.L. E.N. Accelerating Medicines Partnership, S. Raychaudhuri, D.F. Dwyer, A.H. Jonsson, M.B. Brenner, Granzyme K activates the entire complement cascade, Nature (2025)..

[100] A.H. Jonsson, F. Zhang, G. Dunlap, E. Gomez-Rivas, G.F.M. Watts, H.J. Faust, K. V. Rupani, J.R. Mears, N. Meednu, R. Wang, G. Keras, J.S. Coblyn, E. M. Massarotti, D.J. Todd, J.H. Anolik, A. McDavid, R.A.S.L.E.N. Accelerating Medicines Partnership, K. Wei, D.A. Rao, S. Raychaudhuri, M.B. Brenner, Granzyme K(+) CD8 T cells form a core population in inflamed human tissue, Sci. Transl. Med 14 (649) (2022) eab0686.

[101] S. Tiberti, C. Catozzi, O. Croci, M. Ballerini, D. Cagnina, C. Soriani, C. Scirgolea, Z. Gong, J. He, A.D. Macandog, A. Nabinejad, C.B. Nava Lauson, A. Quinte, G. Bertalot, W.L. Petz, S.P. Ravenda, V. Licursi, P. Paci, M. Rasponi, L. Rotta, N. Fazio, G. Ren, U. Fumagalli-Romario, M.H. Schaefer, S. Campaner, E. Lugli, L. Nezi, T. Manzo, GZMK(high) CD8(+) T effector memory cells are associated with CD15(high) neutrophil abundance in non-metastatic colorectal tumors and predict poor clinical outcome, Nat. Commun. 13 (1) (2022) 6752.

[102] A. Zarantonello, M. Revel, A. Grunewald, L.T. Roumenina, C3-dependent effector functions of complement, Immunol. Rev. 313 (1) (2023) 120–138.

[103] P.W. Dempsey, M.E. Allison, S. Akkaraju, C.C. Goodnow, D.T. Fearon, C3d of complement as a molecular adjuvant: bridging innate and acquired immunity, Science 271 (5247) (1996) 348–350.

[104] R.E. Miller, The barium enema in the high-risk carcinoma patient, Radiology 123 (3) (1977) 813–815.

[105] A.A. Wahid, R.W. Dunphy, A. Macpherson, B.G. Gibson, L. Kulik, K. Whale, C. Back, T.M. Hallam, B. Alkhawaja, R.L. Martin, I. Meschede, A. Laabei, A.D. G. Lawson, V.M. Holers, A.G. Watts, S.J. Crennell, C.L. Harris, K.J. Marchbank, J. M.H. van den Elsen, Insights into the structure-function relationships of dimeric C3d fragments, Front Immunol. 12 (2021) 714055.

[106] Michael C. Carroll, David E. Isenman, Regulation of humoral immunity by complement, Immunity 37 (2) (2012) 199–207.

[107] J.-H. Sohn, P.S. Bora, H.-J. Suk, H. Molina, H.J. Kaplan, N.S. Bora, Tolerance is dependent on complement C3 fragment iC3b binding to antigen-presenting cells, Nat. Med. 9 (2) (2003) 206–212.

[108] A. Herbert, Complement controls the immune synapse and tumors control complement, J. Immunother. Cancer 8 (2) (2020) e001712.

[109] J.L. Platt, C. Zhao, J. Chicca, M.J. Pianko, J. Han, S. The, A. Rao, E.T. Keller, M. Garcia de Mattos Barbosa, L. Naing, T. Pasieka-Axenov, L. Axenov, S. Schaefer, E. Farkash, M. Cascalho, Complement C3d enables cell-mediated immunity capable of distinguishing spontaneously transformed from nontransformed cells, Proc. Natl. Acad. Sci. 121 (52) (2024) e2405824121.

[110] S. Baskar, H. Peng, E.M. Gaglione, E.J. Carstens, M.A. Lindorfer, I.E. Ahn, S.E. M. Herman, M. Skarzynski, J. Chang, K. Keyvanfar, V. Butera, A. Blackburn, B. Vire, I. Maric, M. Stetler-Stevenson, C.M. Yuan, M.A. Eckhaus, S. Soto, M.Z. H. Farooqui, R.P. Taylor, C. Rader, A. Wiestner, Potentiating CD20 monoclonal antibody therapy by targeting complement C3 fragments covalently deposited on lymphoma cells, Blood 145 (12) (2025) 1309–1320.

[111] M. Revel, M. Rezola Artero, H. Hamidi, A. Grunewald, L. Blasco, Y.A. Vano, S. Marie Oudard, R. Sanchez-Salas, P. Macek, L. Rodriguez Sanchez, X. Cathelineau, B. Vedie, C. Sautes-Fridman, W. Herman Fridman, L. T. Roumenina, M.A. Dragon-Durey, Humoral complementomics - exploration of noninvasive complement biomarkers as predictors of renal cancer progression, Oncoimmunology 13 (1) (2024) 232843.

[112] M. Revel, C. Sautes-Fridman, W.H. Fridman, L.T. Roumenina, C1q+ macrophages: passengers or drivers of cancer progression, Trends Cancer 8 (7) (2022) 517–526.

[113] L.T. Roumenina, M.V. Daugan, R. Noe, F. Petitprez, Y.A. Vano, R. Sanchez-Salas, E. Becht, J. Meilleroux, B.L. Clec'h, N.A. Giraldo, N.S. Merle, C.M. Sun, V. Verkarre, P. Validire, J. Selves, L. Lacroix, O. Delfour, J. Vandenberghe, C. Thuilliez, S. Keddani, I.B. Sakhi, E. Barret, P. Ferre, N. Corvaia, A. Passioukov, E. Chetaille, M. Botto, A. de Reynies, S.M. Oudard, A. Mejean, X. Cathelineau, C. Sautes-Fridman, W.H. Fridman, Tumor cells hijack macrophage-produced complement C1q to promote tumor growth, Cancer Immunol. Res 7 (7) (2019) 1091–1105.

[114] G.S. Netti, G. Lucarelli, F. Spadaccino, G. Castellano, M. Gigante, C. Divella, M. T. Rocchetti, F. Rascio, V. Mancini, G. Stallone, G. Carrieri, L. Gesualdo, M. Battaglia, E. Ranieri, PTX3 modulates the immunoflogosis in tumor microenvironment and is a prognostic factor for patients with clear cell renal cell carcinoma, Aging (Albany NY) 12 (8) (2020) 7585–7602.

[115] G. Lucarelli, G.S. Netti, M. Rutigliano, F. Lasora, D. Loizzo, M. Milella, A. Schirinzi, A. Fontana, F. Di Serio, R. Tamma, D. Ribatti, M. Battaglia, E. Ranieri, P. Dittonno, MUC1 expression affects the immunoflogosis in renal cell carcinoma microenvironment through complement system activation and immune infiltrate modulation, Int J. Mol. Sci. 24 (5) (2023).

[116] D. Ajona, M.J. Pajares, L. Corrales, J.L. Perez-Gracia, J. Agorreta, M.D. Lozano, W. Torre, P.P. Massion, J.P. de-Torres, E. Jantus-Lewintre, C. Camps, J.J. Zulueta, L.M. Montuenga, R. Pio, Investigation of complement activation product c4d as a diagnostic and prognostic biomarker for lung cancer, J. Natl. Cancer Inst. 105 (18) (2013) 1385–1393.

[117] F. Shao, Y. Gao, W. Wang, H. He, L. Xiao, X. Geng, Y. Xia, D. Guo, J. Fang, J. He, Z. Lu, Silencing EGFR-upregulated expression of CD55 and CD59 activates the complement system and sensitizes lung cancer to checkpoint blockade, Nat. Cancer 3 (10) (2022) 1192–1210.

[118] L.T. Roumenina, M.V. Daugan, F. Petitprez, C. Sautes-Fridman, W.H. Fridman, Context-dependent roles of complement in cancer, Nat. Rev. Cancer 19 (12) (2019) 698–715.

[119] L.T. Roumenina, I. Cremer, COMPLEMENTing immunotherapy, Nat. Cancer 3 (10) (2022) 1144–1146.

[120] K.I. Smolag, C.M. Mueni, K. Leandersson, K. Jirstrom, C. Hagerling, M. Morgelin, P.N. Barlow, M. Martin, A.M. Blom, Complement inhibitor factor H expressed by breast cancer cells differentiates CD14(+) human monocytes into immunosuppressive macrophages, Oncoimmunology 9 (1) (2020) 1731135.

[121] K.I. Smolag, J. Olszowka, R. Rosberg, E. Johansson, E. Marinko, K. Leandersson, D.J.O. Connell, V. Governa, E.C. Tuysuz, M. Belting, A. Pietras, M. Martin, A. M. Blom, Complement factor H is an ICOS ligand modulating Tregs in the glioma microenvironment, Cancer Immunol. Res (2024).

[122] L. Zhai, A. Bell, E. Ladomersky, K.L. Lauing, L. Bollu, B. Nguyen, M. Genet, M. Kim, P. Chen, X. Mi, J.D. Wu, M.J. Schipma, B. Wray, J. Griffiths, R.D. Unwin, S.J. Clark, R. Acharya, R. Bao, C. Horbinski, R.V. Lukas, G.E. Schultz, D. A. Wainwright, Tumor Cell IDO enhances immune suppression and decreases survival independent of tryptophan metabolism in glioblastoma, Clin. Cancer Res 27 (23) (2021) 6514–6528.

[123] G. Liu, X. He, G. Zhao, Z. Lu, Complement regulation in tumor immune evasion, Semin. Immunol. 76 (2024) 101912.

[124] F.-S. Yi, X. Qiao, S.-F. Dong, Q.-Y. Chen, R.-Q. Wei, M.-M. Shao, H.-Z. Shi, Complement C1q is a key player in tumor-associated macrophage-mediated CD8⁺ T cell and NK cell dysfunction in malignant pleural effusion, Int. J. Biol. Sci. 20 (15) (2024) 5979–5998.

[125] A. Obradovic, N. Chowdhury, S.M. Haake, C. Ager, V. Wang, L. Vlahos, X.V. Guo, D.H. Aggen, W.K. Rathmell, E. Jonasch, J.E. Johnson, M. Roth, K.E. Beckermann, B.I. Rini, J. McKiernan, A. Califano, C.G. Drake, Single-cell protein activity analysis identifies recurrence-associated renal tumor macrophages, Cell 184 (11) (2021) 2988–3005, e16.

[126] L. Zhang, Z. Li, K.M. Skrzypczynska, Q. Fang, W. Zhang, S.A. O'Brien, Y. He, L. Wang, Q. Zhang, A. Kim, R. Gao, J. Orf, T. Wang, D. Sawant, J. Kang, D. Bhatt, D. Lu, C.M. Li, A.S. Rapaport, K. Perez, Y. Ye, S. Wang, X. Hu, X. Ren, W. Ouyang, Z. Shen, J.G. Egen, Z. Zhang, X. Yu, Single-cell analyses inform mechanisms of myeloid-targeted therapies in colon cancer, Cell 181 (2) (2020) 442–459.

[127] L. Dong, C. Chen, Y. Zhang, P. Guo, Z. Wang, J. Li, Y. Liu, J. Liu, R. Chang, Y. Li, M. Liang, W. Lai, M. Sun, U. Dougherty, M.B. Bissonnette, H. Wang, L. Shen, M. M. Xu, D. Han, The loss of RNA N(6)-adenosine transferase Mettl14 in tumor-associated macrophages promotes CD8(+) T cell dysfunction and tumor growth, Cancer Cell 39 (7) (2021) 945–957, e10.

[128] D. Zhang, M. Wang, G. Liu, X. Li, W. Yu, Z. Hui, X. Ren, Q. Sun, Novel FABP4(+) C1q(+) macrophages enhance antitumor immunity and associated with response to neoadjuvant pembrolizumab and chemotherapy in NSCLC via AMPK/JAK/STAT axis, Cell Death Dis. 15 (10) (2024) 717.

[129] L. Gao, X. Jing, Q. Hua, Z. Li, P. Lei, P. Song, L. Zhou, Y. Tian, J. Liu, Q. Cai, Complement C1S is a potential prognostic biomarker and associated with M2 macrophage infiltration in gliomas: From bioinformatics to comprehensive experimental validation, Int Immunopharmacol. 143 (Pt 3) (2024) 113573.

[130] M. Lusthaus, N. Mazkereth, N. Donin, Z. Fishelson, Receptor-interacting protein kinases 1 and 3, and mixed lineage kinase domain-like protein are activated by sublytic complement and participate in complement-dependent cytotoxicity, Front Immunol. 9 (2018) 306.

[131] C.B. Xie, D. Jane-Wit, J.S. Pober, Complement membrane attack complex: new roles, mechanisms of action, and therapeutic targets, Am. J. Pathol. 190 (6) (2020) 1138–1150.

[132] D. Ajona, Y.F. Hsu, L. Corrales, L.M. Montuenga, R. Pio, Down-regulation of human complement factor H sensitizes non-small cell lung cancer cells to complement attack and reduces in vivo tumor growth, J. Immunol. 178 (9) (2007) 5991–5998.

[133] J. Chen, P. Ding, L. Li, H. Gu, X. Zhang, L. Zhang, N. Wang, L. Gan, Q. Wang, W. Zhang, W. Hu, CD59 regulation by SOX2 is required for epithelial cancer stem cells to evade complement surveillance, Stem Cell Rep. 8 (1) (2017) 140–151.

[134] J. Hakulinen, S. Meri, Complement-mediated killing of microtumors in vitro, Am. J. Pathol. 153 (3) (1998) 845–855.

[135] R. Jubran, M. Saar-Ray, A. Wawruszak, L. Ziporen, N. Donin, O. Bairey, Z. Fishelson, Mortalin peptides exert antitumor activities and act as adjuvants to antibody-mediated complement-dependent cytotoxicity, Int J. Oncol. 57(4) (2020) 1013–1026.

[136] P. Rozenberg, L. Ziporen, D. Gancz, M. Saar-Ray, Z. Fishelson, Cooperation between Hsp90 and mortalin/GRP75 in resistance to cell death induced by complement C5b-9, Cell Death Dis. 9 (2) (2018) 150.

[137] O. Moskovich, L.O. Herzog, M. Ehrlich, Z. Fishelson, Caveolin-1 and dynamin-2 are essential for removal of the complement C5b-9 complex via endocytosis, J. Biol. Chem. 287 (24) (2012) 19904–19915.

[138] W.D. Lin, T.C. Fan, J.T. Hung, H.L. Yeo, S.H. Wang, C.W. Kuo, K.H. Khoo, L. M. Pai, J. Yu, A.L. Yu, Sialylation of CD55 by ST3GAL1 facilitates immune evasion in cancer, Cancer Immunol. Res 9 (1) (2021) 113–122.
[139] S. Meri, E. Magrini, A. Mantovani, C. Garlanda, The yin yang of complement and cancer, Cancer Immunol. Res 11 (12) (2023) 1578-1588.

[140] D. Ajona, Z. Castano, M. Garayoa, E. Zudaire, M.J. Pajares, A. Martinez, F. Cuttitta, L.M. Montuenga, R. Pio, Expression of complement factor H by lung cancer cells: effects on the activation of the alternative pathway of complement, Cancer Res 64 (17) (2004) 6310-6318.

[141] S. Junnikkala, J. Hakulinen, H. Jarva, T. Manuelian, L. Bjorge, R. Butzow, P. F. Zipfel, S. Meri, Secretion of soluble complement inhibitors factor H and factor H-like protein (FHL-1) by ovarian tumour cells, Br. J. Cancer 87 (10) (2002) 1119-1127.

[142] M.T. Holmberg, A.M. Blom, S. Meri, Regulation of complement classical pathway by association of C4b-binding protein to the surfaces of SK-OV-3 and Caov-3 ovarian adenocarcinoma cells, J. Immunol. 167 (2) (2001) 935-939.

[143] P. Riihila, K. Viiklepp, L. Nissinen, M. Farshchian, M. Kallajoki, A. Kivisaari, S. Meri, J. Peltonen, S. Peltonen, V.M. Kahari, Tumour-cell-derived complement components C1r and C1s promote growth of cutaneous squamous cell carcinoma, Br. J. Dermatol. 182 (3) (2020) 658-670.

[144] L. Nissinen, P. Riihila, K. Viiklepp, V. Rajagopal, M.J. Storek, V.M. Kahari, C1s targeting antibodies inhibit the growth of cutaneous squamous carcinoma cells, Sci. Rep. 14 (1) (2024) 13465.

[145] P. Riihila, L. Nissinen, M. Farshchian, M. Kallajoki, A. Kivisaari, S. Meri, R. Grenman, S. Peltonen, J. Peltonen, T. Pihlajaniemi, R. Heljasvaara, V. M. Kahari, Complement component C3 and complement factor B promote growth of cutaneous squamous cell carcinoma, Am. J. Pathol. 187 (5) (2017) 1186-1197.

[146] P.M. Riihila, L.M. Nissinen, R. Ala-Aho, M. Kallajoki, R. Grenman, S. Meri, S. Peltonen, J. Peltonen, V.M. Kahari, Complement factor H: a biomarker for progression of cutaneous squamous cell carcinoma, J. Invest Dermatol. 134 (2) (2014) 498-506.

[147] P. Riihila, L. Nissinen, M. Farshchian, A. Kivisaari, R. Ala-Aho, M. Kallajoki, R. Grenman, S. Meri, S. Peltonen, J. Peltonen, V.M. Kahari, Complement factor I promotes progression of cutaneous squamous cell carcinoma, J. Invest Dermatol. 135 (2) (2015) 579-588.

[148] M. Tang, S. Zhao, L. Ren, Q. Li, L. Li, C. Wang, C. Meng, Y. Chen, W. Hu, Tumor cell-derived complement component C1r acts as a prognostic biomarker and promotes esophageal squamous cell carcinoma progression, Front Biosci. 29 (4) (2024) 138.

[149] R. Ge, Z. Luan, T. Guo, S. Xia, J. Ye, J. Xu, The expression and biological role of complement C1s in esophageal squamous cell carcinoma, Open Life Sci. 19 (1) (2024) 20220915.

[150] A. Felberg, M. Bienkowski, T. Stokowy, K. Mysczynski, Z. Polakiewicz, K. Kitowska, R. Sadej, F. Mohlin, A. Kuzniewska, D. Kowalska, G. Stasilojc, I. Jongerius, R. Spaapen, M. Mesa-Guzman, L.M. Montuenga, A.M. Blom, R. Pio, M. Okroj, Elevated expression of complement factor I in lung cancer cells associates with shorter survival-Potentially via non-canonical mechanism, Transl. Res 269 (2024) 1-13.

[151] R. Bulla, C. Tripodo, D. Rami, G.S. Ling, C. Agostinis, C. Guarnotta, S. Zorzet, P. Durigotto, M. Botto, F. Tedesco, C1q acts in the tumour microenvironment as a cancer-promoting factor independently of complement activation, Nat. Commun. 7 (2016) 10346.

[152] C. Agostinis, R. Vidergar, B. Belmonte, A. Mangogna, L. Amadio, P. Geri, V. Borelli, F. Zanconati, F. Tedesco, M. Confalonieri, C. Tripodo, U. Kishore, R. Bulla, Complement proteinesco C1q binds to hyaluronic acid in the malignant pleural mesothelioma microenvironment and promotes tumor growth, Front Immunol. 8 (2017) 1559.

[153] L. Liu, W. Li, Z. Li, M. Kirschfink, Sublytic complement protects prostate cancer cells from tumour necrosis factor-alpha-induced cell death, Clin. Exp. Immunol. 169 (2) (2012) 100-108.

[154] Q. Hong, C.I. Sze, S.R. Lin, M.H. Lee, R.Y. He, L. Schultz, J.Y. Chang, S.J. Chen, R. J. Boacke, L.J. Hsu, N.S. Chang, Complement C1q activates tumor suppressor WWOX to induce apoptosis in prostate cancer cells, PLoS One 4 (6) (2009) e5755.

[155] S. Bandini, M. Macagno, A. Hysi, S. Lanzardo, L. Conti, A. Bello, F. Riccardo, R. Ruiu, I.F. Merighi, G. Forni, M. Iezzi, E. Quaglino, F. Cavallo, The non-inflammatory role of C1q during Her2/neu-driven mammary carcinogenesis, Oncoimmunology 5 (12) (2016) e1253653.

[156] A. Kaur, S.H. Sultan, V. Murugaiah, A.A. Pathan, F.S. Alhamlan, E. Karteris, U. Kishore, Human C1q induces apoptosis in an ovarian cancer cell line via tumor necrosis factor pathway, Front Immunol. 7 (2016) 599.

[157] I. Block, C. Muller, D. Sdogati, H. Pedersen, M. List, A.M. Jaskot, S.D. Syse, P. Lund Hansen, S. Schmidt, H. Christiansen, C. Casella, S. Bering Olsen, M. M. Blomstrom, A. Riedel, M. Thomassen, T.A. Kruse, S.W. Karlskov Hansen, P. Kioschis, J. Mollenhauer, CFP suppresses breast cancer cell growth by TES-mediated upregulation of the transcription factor DDIT3, Oncogene 38 (23) (2019) 4560-4573.

[158] Y. Lu, X.B. Hu, C5a stimulates the proliferation of breast cancer cells via Akt-dependent RGC-32 gene activation, Oncol. Rep. 32 (6) (2014) 2817-2823.

[159] M.S. Cho, H.G. Vasquez, R. Rupaimoole, S. Pradeep, S. Wu, B. Zand, H.D. Han, C. Rodriguez-Aguayo, J. Bottsford-Miller, J. Huang, T. Miyake, H.J. Choi, H. J. Dalton, C. Ivan, K. Baggerly, G. Lopez-Berestein, A.K. Sood, V. Afshar-Kharghan, Autocrine effects of tumor-derived complement, Cell Rep. 6 (4) (2016) 1085-1095.

[160] P. Ding, Y. Xu, L. Li, X. Lv, L. Li, J. Chen, D. Zhou, X. Wang, Q. Wang, W. Zhang, T. Liao, Q.H. Ji, Q.Y. Lei, W. Hu, Intracellular complement C5a/C5aR1 stabilizes beta-catenin to promote colorectal tumorigenesis, Cell Rep. 39 (9) (2022) 110851.

[161] J. Huang, L. Zhou, K. Deng, Prognostic marker C3AR1 is associated with ovarian cancer cell proliferation and immunosuppression in the tumor microenvironment, J. Ovarian Res. 16 (1) (2023) 64.

[162] Z. Fan, J. Qin, D. Wang, S. Geng, Complement C3a promotes proliferation, migration and stemness in cutaneous squamous cell carcinoma, J. Cell Mol. Med 23 (5) (2019) 3097-3107.

[163] T.C. Badea, F.I. Niculescu, L. Soane, M.L. Shin, H. Rus, Molecular cloning and characterization of RGC-32, a novel gene induced by complement activation in oligodendrocytes, J. Biol. Chem. 273 (41) (1998) 26977-26981.

[164] S.I. Vlaicu, C.A. Tegla, C.D. Cudrici, J. Danoff, H. Madani, A. Sugarman, F. Niculescu, P.A. Mircea, V. Rus, H. Rus, Role of C5b-9 complement complex and response gene to complement-32 (RGC-32) in cancer, Immunol. Res 56 (1) (2013) 109-121.

[165] F. Niculescu, H. Rus, T. van Biesen, M.L. Shin, Activation of Ras and mitogen-activated protein kinase pathway by terminal complement complexes is G protein dependent, J. Immunol. 158 (9) (1997) 4405-4412.

[166] B. Ghebrehiwet, M. Zaniewski, A. Fernandez, M. DiGiovanni, T.N. Reyes, P. Ji, A. G. Savitt, J.L. Williams, M.A. Seeliger, E.I.B. Peerschke, The C1q and gC1qR axis as a novel checkpoint inhibitor in cancer, Front Immunol. 15 (2024) 1351656.

[167] D.R. Welch, D.R. Hurst, Defining the hallmarks of metastasis, Cancer Res 79 (12) (2019) 3011-3027.

[168] D. Ajona, C. Zandueta, L. Corrales, H. Moreno, M.J. Pajares, S. Ortiz-Espinosa, E. Martinez-Terroba, N. Perurena, F.J. de Miguel, E. Jantus-Lewintie, C. Camps, S. Vicent, J. Agorreta, L.M. Montuenga, R. Pio, F. Lecanda, Blockade of the complement C5a/C5aR1 axis impairs lung cancer bone metastasis by CXCL16-mediated effects, Am. J. Respir. Crit. Care Med. 197 (9) (2018) 1164-1176.

[169] A. Boire, Y. Zou, J. Shieh, D.G. Macalinao, E. Pentova, J. Massage, Complement component 3 adapts the cerebrospinal fluid for leptomeningeal metastasis, Cell 168 (6) (2017) 1101-1113, e13.

[170] H. Nitta, Y. Wada, Y. Kawano, Y. Murakami, A. Irie, K. Taniguchi, K. Kikuchi, G. Yamada, K. Suzuki, J. Honda, M. Wilson-Morifuji, N. Araki, M. Eto, H. Baba, T. Imamura, Enhancement of human cancer cell motility and invasiveness by anaphylatoxin C5a via aberrantly expressed C5a receptor (CD88), Clin. Cancer Res 19 (8) (2013) 2004-2013.

[171] T. Kaida, H. Nitta, Y. Kitano, K. Yamamura, K. Arima, D. Izumi, T. Higashi, J. Kurashige, K. Imai, H. Hayashi, M. Iwatsuki, T. Ishimoto, D. Hashimoto, Y. Yamashita, A. Chikamoto, T. Imanura, T. Ishiko, T. Beppu, H. Baba, C5a receptor (CD88) promotes motility and invasiveness of gastric cancer by activating RhoA, Oncotarget 7 (51) (2016) 84798-84809.

[172] H. Nitta, T. Shimose, Y. Emi, T. Imamura, K. Ohnishi, T. Kusumoto, M. Yamamoto, K. Fukuzawa, I. Takahashi, H. Higashi, A. Tsuji, Y. Akagi, E. Oki, Y. Maehara, H. Baba, s. Kyushu Study Group of Clinical Cancer ancillary, Expression of the anaphylatoxin C5a receptor in gastric cancer: implications for vascular invasion and patient outcomes, Med Oncol. 33 (11) (2016) 118.

[173] M.S. Cho, R. Rupaimoole, H.J. Choi, K. Noh, J. Chen, Q. Hu, A.K. Sood, V. Afshar-Kharghan, Complement component 3 is regulated by TWIST1 and mediates epithelial-mesenchymal transition, J. Immunol. 196 (3) (2016) 1412-1418.

[174] W.H. Hu, Z. Hu, X. Shen, L.Y. Dong, W.Z. Zhou, X.X. Yu, C5a receptor enhances hepatocellular carcinoma cell invasion effectiveness via activating ERK1/2-mediated epithelial-mesenchymal transition, Exp. Mol. Pathol. 100 (1) (2016) 101-108.

[175] S. Ortiz-Espinosa, X. Morales, Y. Senent, D. Alignani, B. Tavira, I. Macaya, B. Ruiz, H. Moreno, A. Remirez, C. Sainz, A. Rodriguez-Pena, A. Oyarbide, M. Ariz, M. P. Andueza, K. Valencia, A. Teijeira, K. Hoehlig, A. Vater, B. Rolfe, T. M. Woodruff, J.M. Lopez-Picazo, S. Vicent, G. Kochan, D. Escors, I. Gil-Bazo, J. L. Perez-Gracia, L.M. Montuenga, J.D. Lambris, C. Ortiz de Solorzano, F. Lecanda, D. Ajona, R. Pio, Complement C5a induces the formation of neutrophil extracellular traps by myeloid-derived suppressor cells to promote metastasis, Cancer Lett. 529 (2022) 70-84.

[176] X. Liu, Y. Wang, A.T. Bauer, M. Kirschfink, P. Ding, C. Gebhardt, L. Borsig, T. Tuting, T. Renne, K. Haffner, W. Hu, S.W. Schneider, C. Gorzelanny, Neutrophils activated by membrane attack complexes increase the permeability of melanoma blood vessels, Proc. Natl. Acad. Sci. USA 119 (33) (2022) e2122716119.

[177] L.D. Towner, R.A. Wheat, T.R. Hughes, B.P. Morgan, Complement membrane attack and tumorigenesis: a SYSTEMS BIOLOGY APPROACH, J. Biol. Chem. 291 (29) (2016) 14927-14938.

[178] J.H. Lee, B. Poudel, H.H. Ki, S. Nepali, Y.M. Lee, J.S. Shin, D.K. Kim, Complement C1q stimulates the progression of hepatocellular tumor through the activation of discoidin domain receptor 1, Sci. Rep. 8 (1) (2018) 4908.

[179] K.B. Kim, J.S. Yi, N. Nguyen, J.H. Lee, Y.C. Kwon, B.Y. Ahn, H. Cho, Y.K. Kim, H. J. Yoo, J.S. Lee, Y.G. Ko, Cell-surface receptor for complement component C1q (gC1qR) is a key regulator for lamellipodia formation and cancer metastasis, J. Biol. Chem. 286 (26) (2011) 23093-23101.

[180] K. Viiklepp, L. Nissinen, M. Ojalill, P. Riihila, M. Kallajoki, S. Meri, J. Heino, V. M. Kahari, C1r Upregulates production of matrix metalloproteinase-13 and promotes invasion of cutaneous squamous cell carcinoma, J. Invest Dermatol. 142 (5) (2022) 1478-1488, e9.

[181] X. Ma, Y. Wang, P. Tuo, Z. Meng, B. Jiang, Y. Yuan, Y. Ding, A. Naeem, X. Guo, X. Wang, Downregulation of C1R promotes hepatocellular carcinoma development by activating HIF-1alpha-regulated glycolysis, Mol. Carcinog. 63 (11) (2024) 2237-2253.

[182] X. Mao, L. Zhou, S.K. Tey, A.P.Y. Ma, C.L.S. Yeung, T.H. Ng, S.W.K. Wong, B.H. M. Liu, Y.M.E. Fung, E.F. Patz Jr., P. Cao, Y. Gao, J.W.P. Yam, Tumour extracellular vesicle-derived Complement Factor H promotes tumorigenesis and metastasis by inhibiting complement-dependent cytotoxicity of tumour cells, J. Extra Vesicles 10 (1) (2020) e12031.
[183] R.T. Bushey, E.B. Gottlin, M.J. Campa, E.F. Patz, Jr., Complement factor H protects tumor cell-derived exosomes from complement-dependent lysis and phagocytosis, PLOS ONE 16 (6) (2021) e0252577.

[184] Y. Zhang, X. Wang, Y. Gu, T. Liu, X. Zhao, S. Cheng, L. Duan, C. Huang, S. Wu, S. Gao, Complement C3 of tumor-derived extracellular vesicles promotes metastasis of RCC via recruitment of immunosuppressive myeloid cells, Proc. Natl. Acad. Sci. U.S.A. 122 (4) (2025) e2420005122.

[185] R. Shimazaki, S. Takano, M. Satoh, M. Takada, Y. Miyahara, K. Sasaki, H. Yoshitomi, S. Kagawa, K. Furukawa, T. Takayashiki, S. Kuboki, K. Sogawa, S. Motohashi, F. Nomura, M. Miyazaki, M. Ohsuka, Complement factor B regulates cellular senescence and is associated with poor prognosis in pancreatic cancer, Cell Oncol. (Dordr.) 44 (4) (2021) 937-950.

[186] S.Y. Park, D.Y. Eum, Y. Jin, C.Y. Lee, J.W. Shim, S.H. Choi, S.J. Park, K. Heo, Y. J. Choi, Downregulation of complement factor H attenuates the stemness of MDA-MB-231 breast cancer cells via modulation of the ERK and p38 signaling pathways, Oncol. Lett. 26 (6) (2023) 521.

[187] H.G. Rus, F.I. Niculescu, M.L. Shin, Role of the C5b-9 complement complex in cell cycle and apoptosis, Immunol. Rev. 180 (2001) 49-55.

[188] M.M. Markiewicz, E. Daugherty, B. Reese, M. Karbowniczek, The role of complement in angiogenesis, Antibodies 9 (4) (2020).

[189] R. Kurihara, K. Yamaoka, N. Sawamukai, S. Shimajiri, K. Oshita, S. Yukawa, M. Tokunaga, S. Iwata, K. Saito, K. Chiba, Y. Tanaka, C5a promotes migration, proliferation, and vessel formation in endothelial cells, Inflamm. Res 59 (8) (2010) 659-666.

[190] M.A. Khan, A.M. Assiri, D.C. Broering, Complement and macrophage crosstalk during process of angiogenesis in tumor progression, J. Biomed. Sci. 22 (1) (2015) 58.

[191] S. Nunez-Cruz, P.A. Gimotty, M.W. Guerra, D.C. Connolly, Y.Q. Wu, R. A. DeAngelis, J.D. Lambris, G. Coukos, N. Scholler, Genetic and pharmacologic inhibition of complement impairs endothelial cell function and ablates ovarian cancer neovascularization, Neoplasia 14 (11) (2012) 994-1004.

[192] B. Reese, A. Silwal, E. Daugherty, M. Daugherty, M. Arabi, P. Daly, Y. Paterson, L. Woolford, A. Christie, R. Elias, J. Brugarolas, T. Wang, M. Karbowniczek, M. M. Markiewicz, Complement as prognostic biomarker and potential therapeutic target in renal cell carcinoma, J. Immunol. 205 (11) (2020) 3218-3229.

[193] S. Bandini, C. Curcio, M. Macagno, E. Quaglino, M. Arigoni, S. Lanzardo, A. Hysi, G. Barutello, L. Consolino, D.L. Longo, P. Musiani, G. Forni, M. Iezzi, F. Cavallo, Early onset and enhanced growth of autochthonous mammary carcinomas in C3-deficient Her2/neu transgenic mice, Oncoimmunology 2 (9) (2013) e26137.

[194] H.I. Kenawy, I. Boral, A. Bevington, Complement-coagulation cross-talk: a potential mediator of the physiological activation of complement by low pH, Front Immunol. 6 (2015) 215.

[195] Z. Fishelson, R.D. Horstmann, H.J. Muller-Eberhard, Regulation of the alternative pathway of complement by pH, J. Immunol. 138 (10) (1987) 3392-3395.

[196] K. Miyazawa, K. Inoue, Complement activation induced by human C-reactive protein in mildly acidic conditions, J. Immunol. 145 (2) (1990) 650-654.

[197] D.P. Noone, T.T. van der Velden, T.H. Sharp, Cryo-electron microscopy and biochemical analysis offer insights into the effects of acidic pH, such as occur during acidosis, on the complement binding properties of C-reactive protein, Front. Immunol. 12 (2021).

[198] L.T. Roumenina, M.M. Ruseva, A. Zlatarova, R. Ghai, M. Kolev, N. Olova, M. Gadjeva, A. Agrawal, B. Bottazzi, A. Mantovani, K.B.M. Reid, U. Kishore, M. S. Kojouharova, Interaction of C1q with IgG1, C-reactive protein and pentraxin 3: mutational studies using recombinant globular head modules of human C1q A, B, and C chains, Biochemistry 45 (13) (2006) 4093-4104.

[199] K. Fromell, A. Adler, A. Aman, V.A. Manivel, S. Huang, C. Duhrkop, K. Sandholm, K.N. Ekdahl, B. Nilsson, Assessment of the role of C3(H2O) in the alternative pathway, Front Immunol. 11 (2020) 530.

[200] I.K. Djoumerska-Alexieva, J.D. Dimitrov, E.N. Voynova, S. Lacroix-Desmazes, S. V. Kaveri, T.L. Vassilev, Exposure of IgG to an acidic environment results in molecular modifications and in enhanced protective activity in sepsis, FEBS J. 277 (14) (2010) 3039-3050.

[201] E. Dantas, F.E. Dfaz, P.P. Gerber, A. Merlotti, A. Varese, M. Ostrowski, J. Sabatté, J. Geffner, Low pH impairs complement-dependent cytotoxicity against IgG-coated target cells, Oncotarget 7 (45) (2016).

[202] H. Tian, G. Wang, Q. Wang, B. Zhang, G. Jiang, H. Li, D. Chai, L. Fang, M. Wang, J. Zheng, Complement C1q binding protein regulates T cells' mitochondrial fitness to affect their survival, proliferation, and anti-tumor immune function, Cancer Sci. 113 (3) (2022) 875-890.

[203] E.E. West, C. Kemper, 2019, Complement and T Cell Metabolism: Food for Thought, Immunometabolism 1(T Cell Metabolic Reprogramming) (2019) e190006.

[204] F. Colotta, P. Allavena, A. Sica, C. Garlanda, A. Mantovani, Cancer-related inflammation, the seventh hallmark of cancer: links to genetic instability, Carcinogenesis 30 (7) (2009) 1073-1081.

[205] B. Halliwell, Oxygen and nitrogen are pro-carcinogens. Damage to DNA by reactive oxygen, chlorine and nitrogen species: measurement, mechanism and the effects of nutrition, Mutat. Res. 443 (1-2) (1999) 37-52.

[206] O.A. Hawksworth, L.G. Coulthard, S.M. Taylor, E.J. Wolvetang, T.M. Woodruff, Brief report: complement C5a promotes human embryonic stem cell pluripotency in the absence of FGF2, Stem Cells 32 (12) (2014) 3278-3284.

[207] K. Bujko, K. Brzenziakiewicz-Janus, M. Lucia, M.Z. Ratajczak, Intracellular complement (Complosome) is expressed in several types of human adult bone marrow—derived stem cells, Stem Cell Rev. Rep. 20 (1) (2024) 437-439.

[208] H.S. Seol, S.E. Lee, J.S. Song, J.K. Rhee, S.R. Singh, S. Chang, S.J. Jang, Complement proteins C7 and CFH control the stemness of liver cancer cells via LSF-1, Cancer Lett. 372 (1) (2016) 24-35.

[209] R. Zhou, Y. Wu, W. Wang, W. Su, Y. Liu, Y. Wang, C. Fan, X. Li, G. Li, Y. Li, W. Xiong, Z. Zeng, Circular RNAs (circRNAs) in cancer, Cancer Lett. 425 (2018) 134-142.

[210] Z. Du, L. Wang, Y. Xia, Circ_0015756 promotes the progression of ovarian cancer by regulating miR-942-5p/CUL4B pathway, Cancer Cell Int 20 (1) (2020) 572.

[211] Z. Chen, J. Du, C. Yang, G. Si, Y. Chen, circ-CFH promotes the development of HCC by regulating cell proliferation, apoptosis, migration, invasion, and glycolysis through the miR-377-3p/RNF38 axis, Open Life Sci. 17 (1) (2022) 248-260.

[212] W. Guo, L. Zhao, G. Wei, P. Liu, Y. Zhang, L. Fu, Circ_0015756 aggravates hepatocellular carcinoma development by regulating FGFR1 via sponging miR-610, Cancer Manag Res 12 (2020) 7383-7394.

[213] A. Bian, Y. Wang, J. Liu, X. Wang, D. Liu, J. Jiang, L. Ding, X. Hui, Circular RNA complement factor H (CFH) promotes glioma progression by sponging miR-149 and regulating AKT1, Med Sci. Monit. 24 (2018) 5704-5712.

[214] X. Meng, Z. Wang, Q. Yang, Y. Liu, Y. Gao, H. Chen, A. Li, R. Li, J. Wang, G. Sun, Intracellular C5aR1 inhibits ferroptosis in glioblastoma through METTL3-dependent m6A methylation of GPX4, Cell Death Dis. 15 (10) (2024) 729.

[215] Y. Hillman, M. Mardamshina, M. Pasmanik-Chor, L. Ziporen, T. Geiger, N. Shomron, Z. Fishelson, MicroRNAs affect complement regulator expression and mitochondrial activity to modulate cell resistance to complement-dependent cytotoxicity, Cancer Immunol. Res. 7 (12) (2019) 1970-1983.

[216] M.P. Lythgoe, B.H. Mullish, A.E. Frampton, J. Krell, Polymorphic microbes: a new emerging hallmark of cancer, Trends Microbiol. 30 (12) (2022) 1131-1134.

[217] B. Aykut, S. Pushalkar, R. Chen, Q. Li, R. Abengozar, J.I. Kim, S.A. Shadaloey, D. Wu, P. Preiss, N. Verma, Y. Guo, A. Saxena, M. Vardhan, B. Diskin, W. Wang, J. Leinwand, E. Kurz, J.A. Kochen Rossi, M. Hundeyin, C. Zambrínis, X. Li, D. Saxena, G. Miller, The fungal mycobiome promotes pancreatic oncogenesis via activation of MBL, Nature 574 (7777) (2019) 264-267.

[218] M. Wu, W. Zheng, X. Song, B. Bao, Y. Wang, D. Ramanan, D. Yang, R. Liu, J. C. Macbeth, E.A. Do, W.A. Andrade, T. Yang, H.S. Cho, F.S. Gazzaniga, M. Ilves, D. Coronado, C. Thompson, S. Hang, I.M. Chiu, J.R. Moffitt, A. Hsiao, J. J. Mekalanos, C. Benoist, D.L. Kasper, Gut complement induced by the microbiota combats pathogens and spares commensals, Cell 187 (4) (2024) 897-913, e18.

[219] C. Krieg, L.M. Weber, B. Fosso, M. Marzano, G. Hardiman, M.M. Olcina, E. Domingo, S. El Aidy, K. Mallah, M.D. Robinson, S. Guglietta, Complement downregulation promotes an inflammatory signature that renders colorectal cancer susceptible to immunotherapy, J. Immunother. Cancer 10 (9) (2022).

[220] J.P. Coppe, P.Y. Desprez, A. Krtolica, J. Campisi, The senescence-associated secretory phenotype: the dark side of tumor suppression, Annu Rev. Pathol. 5 (2010) 99-118.

[221] A.H. Abu-Humaidan, M.A. Ismail, F.M. Ahmad, S. Al Shboul, R. Barham, J. S. Tadros, A. Alhesa, M. El-Sadoni, M.R. Alotaibi, N.A. Ababneh, T. Saleh, Therapy-induced senescent cancer cells exhibit complement activation and increased complement regulatory protein expression, Immunol. Cell Biol. 102 (4) (2024) 240-255.

[222] S.S. Bohlson, A.J. Tenner, Complement in the brain: contributions to neuroprotection, neuronal plasticity, and neuroinflammation, Annu Rev. Immunol. 41 (2023) 431-452.

[223] S.E. Parker, M.C. Bellingham, T.M. Woodruff, Complement drives circuit modulation in the adult brain, Prog. Neurobiol. 214 (2022) 102282.

[224] J.D. Lee, L.G. Coulthard, T.M. Woodruff, Complement dysregulation in the central nervous system during development and disease, Semin Immunol. 45 (2019) 101340.

[225] S. Hong, V.F. Beja-Glasser, B.M. Fnonoyim, A. Frouin, S. Li, S. Ramakrishnan, K. M. Merry, Q. Shi, A. Rosenthal, B.A. Barres, C.A. Lemere, D.J. Selkoe, B. Stevens, Complement and microglia mediate early synapse loss in Alzheimer mouse models, Science 352 (6286) (2016) 712-716.