bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract IA04: Targeting macrophages to promote anti-tumor immunity
Authors: Varner Judith A.
Published: February 2021

Macrophages accumulate rapidly in tumors, where they promote immune suppression, tumor growth and resistance to therapy. Strategies to inhibit macrophage accumulation by blocking their recruitment from circulation have had limited therapeutic success. We found that the majority of macrophages in aggressive solid tumors accumulate by proliferation from c-Kit dependent tissue resident macrophages, rather than by trafficking from the circulation. Tissue resident macrophages express signatures of proliferation and profound immune suppression that correlate with unfavorable outcomes in cancer patients. By comparison, bone marrow derived macrophages express mixed signatures of inflammation and immune suppression that correlate with more favorable clinical outcomes. Genetic and pharmacological inhibition of proliferation mechanisms suppressed the expansion of these macrophages, thereby limiting their accumulation in tumors and inhibiting tumor progression in mouse models of cancer. These results identify macrophage proliferation is a new target for the development of therapeutic strategies to stimulate anti-cancer immunity.

Citation Format: Judith A. Varner. Targeting macrophages to promote anti-tumor immunity [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr IA04.
Abstract IA09: The IRE1 ER stress sensor activates natural killer cell immunity by regulating c-Myc
Authors: Glimcher Laurie H.
Published: February 2021

Natural killer (NK) cells are critical mediators of host immunity to pathogens. Here, we demonstrate that the endoplasmic retic- ulum stress sensor inositol-requiring enzyme 1 (IRE1α) and its substrate transcription factor X-box-binding protein 1 (XBP1) drive NK cell responses against viral infection and tumors in vivo. IRE1α-XBP1 were essential for expansion of activated mouse and human NK cells and are situated downstream of the mammalian target of rapamycin signaling pathway. Transcriptome and chromatin immunoprecipitation analysis revealed c-Myc as a new and direct downstream target of XBP1 for regulation of NK cell proliferation. Genetic ablation or pharmaceutical blockade of IRE1α downregulated c-Myc, and NK cells with c-Myc haplo- insufficency phenocopied IRE1α-XBP1 deficiency. c-Myc overexpression largely rescued the proliferation defect in IRE1α−/− NK cells. Like c-Myc, IRE1α-XBP1 also promotes oxidative phosphorylation in NK cells. Overall, our study identifies a IRE1α-XBP1- cMyc axis in NK cell immunity, providing insight into host protection against infection and cancer.

Citation Format: Laurie H. Glimcher. The IRE1 ER stress sensor activates natural killer cell immunity by regulating c-Myc [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr IA09.
Abstract IA10: Building improved personal cancer vaccines
Authors: Wu Catherine J.
Published: February 2021

Multiple lines of evidence have convincingly demonstrated tumor neoantigens as an important class of immunogenic tumor antigens, and have motivated the development of personalized cancer neoantigen targeting approaches. Neoantigens arise from amino acid changes encoded by somatic mutations in the tumor cell and have the potential to bind to and be presented by personal HLA molecules. Because the immune response has the capacity of addressing multiple tumor neoantigens simultaneously, immune-based therapy has a potential for directly address tumor heterogeneity. As a field, we have now successfully moved beyond the first wave proof-of-concept studies that have demonstrated the safety, feasibility and high immunogenicity of these personalized neoantigen-targeting vaccines. An imperative now is to address the challenges of discovering and optimizing the selection of antigens to target, the delivery approach, and extending this promising approach to a broader array of cancer settings.

Citation Format: Catherine J. Wu. Building improved personal cancer vaccines [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr IA10.
Abstract IA13: The future of CAR therapies
Authors: Shpall Elizabeth J.
Published: February 2021

Great progress has been made in the development of clinical CAR-T cell therapies. The autologous CAR-T cell approaches in the clinic today are extremely effective but have been associated with significant toxicities and are very expensive. The use of allogeneic, off-the-shelf CAR therapies using natural killer cells from several different sources will be reviewed as potentially less toxic and less expensive immune effector cell products to treat cancer patients.

Citation Format: Elizabeth J. Shpall. The future of CAR therapies [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr IA13.
Abstract IA17: The role of the senescence-associated secretory phenotype in cancer
Authors: Patel Rupesh S. , Romero Rodrigo , Liang Anthony C. , Watson Emma V. , Burger Megan , Westcott Peter M.K. , Mercer Kim L. , Bronson Roderick T. , Wooten Eric C. , Bhutkar Arjun , Jacks Tyler , Elledge Stephen J.
Published: February 2021

Cellular senescence is a stress-activated differentiation pathway that causes proliferation arrest governed by two powerful tumor suppressor pathways, USP28-TP53-CDKN1A and CDKN2A-RB. Senescent cells exhibit a pro-inflammatory secretory program termed the senescence-associated secretory phenotype (SASP) that is composed of chemokines, cytokines, growth factors, and proteases. SASP induction is independent of TP53 and RB function and its role in cancer has not been fully elucidated. We genetically targeted the master regulator of SASP, GATA4, and found that SASP functions as a non-cell autonomous tumor suppressor mechanism. We show that SASP is tumor suppressive in mouse models of cancer using both deletion and overexpression contexts. SASP-dependent tumor suppression requires the immune system, specifically CD8 cytotoxic T cells, to suppress tumor growth. Human tumors deficient in GATA4 have reduced lymphocyte infiltrates, indicating that human cancers may avoid immune infiltration by limiting SASP.

Citation Format: Rupesh S. Patel, Rodrigo Romero, Anthony C. Liang, Emma V. Watson, Megan Burger, Peter M.K. Westcott, Kim L. Mercer, Roderick T. Bronson, Eric C. Wooten, Arjun Bhutkar, Tyler Jacks, Stephen J. Elledge. The role of the senescence-associated secretory phenotype in cancer [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr IA17.
Abstract PO009: Epigenetic silencing by SETDB1 represses tumor-cell intrinsic immunogenicity
Authors: Wu Jingyi , Iracheta-Vellve Arvin , Patti James , Hsu Jeffrey , Davis Thomas , Dele-Oni Deborah , Du Peter , Ishizuka Jeffrey , Kim Sarah , Klaeger Susan , Knudsen Nelson , Miller Brian , Nguyen Tung , Robitschek Emily , Schneider Emily , Zimmer Margaret , Jaffe Jacob , Doench John , Haining W. Nicholas , Yates Kathleen , Manguso Robert , Bernstein Bradley , Griffin Gabriel K.
Published: February 2021

Epigenetic alterations are defining features of many tumor types and have recently been implicated in tumor immunity. However, the epigenetic mechanisms that mediate immune sensitivity or resistance in cancer cells are poorly characterized. To systematically identify epigenetic regulators of immune evasion in cancer, we performed in vivo loss of function CRISPR screens against 936 chromatin regulator genes in syngeneic murine tumor models treated with immune checkpoint blockade. These screens identified SETDB1, an H3K9-methyltransferase, and associated members of the HUSH and KAP1 complexes as intrinsic mediators of immune evasion in cancer cells. We also found that amplification of SETDB1 (1q21) in certain human tumors is associated with immune exclusion and resistance to immune checkpoint blockade. Mechanistically, we find that SETDB1 targets broad domains, hundreds of kilobases in size, that are predominantly located within the open genome compartment “A” (i.e., euchromatin). These SETDB1 domains show strong enrichment for transposable elements (TEs) of the LTR family, and gene loci that arose through segmental duplication events, a key driver of mammalian genome evolution. Setdb1 KO derepresses latent regulatory elements at TEs within these regions and leads to the transcriptional up-regulation of nearby immune genes, including canonical stimulatory ligands of the NKG2D receptor. SETDB1 loss also triggers the activation of hundreds of TEs with the potential to encode retroviral proteins (Gag, Pol, Env), and promotes immune responses dependent on CD8+ T cells and tumor expression of MHC Class I. Our study establishes SETDB1 as an epigenetic checkpoint that represses intrinsic immunogenicity in cancer cells, and thus represents a novel target to enhance the efficacy and scope of immunotherapy.

Citation Format: Jingyi Wu, Arvin Iracheta-Vellve, James Patti, Jeffrey Hsu, Thomas Davis, Deborah Dele-Oni, Peter Du, Jeffrey Ishizuka, Sarah Kim, Susan Klaeger, Nelson Knudsen, Brian Miller, Tung Nguyen, Emily Robitschek, Emily Schneider, Margaret Zimmer, Jacob Jaffe, John Doench, W. Nicholas Haining, Kathleen Yates, Robert Manguso, Bradley Bernstein, Gabriel K. Griffin. Epigenetic silencing by SETDB1 represses tumor-cell intrinsic immunogenicity [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO009.
Abstract PO018: Restoring the tumor-suppressed immune response during chemotherapy by targeting Mer:PTP1b interactions
Authors: Prieto-Dominguez Nestor , Ubil Eric S.
Published: February 2021

The development of adaptive immune checkpoint inhibitors, which prevent tumor-mediated inactivation of lymphocytes, has drastically improved outcomes for advanced cancer patients. However, only 20-30% of patients benefit from these treatments and those that do often present moderate toxicity and/or later relapse. After discovering a novel innate immune checkpoint, we have identified a therapeutic strategy to restore the tumor-suppressed immune response during chemotherapy. Here, we show that multiple tumor types (including melanoma, lung, breast and pancreatic cancers) co-cultured with murine primary macrophages suppress the expression of the essential Toll-like Receptor (TLR) signal-transducing adapter protein MyD88 by 57-81% +/- 2-5% (mean +/- SEM). In the absence of MyD88, macrophages are unable to respond to TLR stimulating Damage Associated Molecular Patterns (DAMPs) released by dying tumor cells after chemotherapy, leading to as much as 97% +/- 6% reduction in pro-inflammatory gene expression in our co-culture models. Tumors exert this suppression by activating the macrophage Mer receptor, inducing recruitment of a phosphatase, known as PTP1b, and Stat1 to Mer. Increasing association between PTP1b and Stat1 leads to reduced Stat1 phosphorylation and translocation to the nucleus as well as a downstream reduction in MyD88 expression. Treatment with a pharmacological inhibitor of PTP1b (BVT948) blocks the association of Mer, PTP1b and Stat1, restoring MyD88 expression and responsiveness to chemotherapy-released DAMPs. In chemotherapy-resistant murine syngeneic melanoma models, including B16F10 and GEMM6 (Braf V600E, Pten-/-), we show that combination therapy with BVT948 and Cisplatin or Vemurafenib, respectively, leads to a 47% reduction in tumor growth rates. Treating chemo- and immuno-therapy resistant Lewis Lung Cancer (LLC) tumor-bearing mice with combination BVT948/Cisplatin therapy leads to a similar reduction in tumor growth that is magnified with the addition of adaptive immune checkpoint blockade. In summary, we have described a novel mechanism of cancer-mediated immune suppression that dramatically reduces the immune response during chemotherapy. PTP1b inhibition could represent a novel therapeutic strategy to improve the effectiveness of conventional chemotherapy in patients with advanced malignancies.

Citation Format: Nestor Prieto-Dominguez, Eric S. Ubil. Restoring the tumor-suppressed immune response during chemotherapy by targeting Mer:PTP1b interactions [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO018.
Abstract PO023: Immune-mediated tumor growth inhibition by selective HDAC6 inhibitor SP-2-225
Authors: Grindrod Scott , Noonepalle Satish , Aghdam Nima , Velena Alfredo , Gracia-Hernandez Maria , Zevallos-Delgado Christian , Jung Mira , Dritschilo Anatoly , Villagra Alejandro
Published: February 2021

In addition to their canonical role in transcriptional regulation, Histone deacetylases (HDACs) regulate other cellular functions by maintaining a balance of lysine acetylation on key cellular proteins. HDAC inhibitors are under development for use in treating cancers, neurological, and immunological diseases. A barrier to the development of HDAC inhibitors has been the toxicity associated with non-selective pan-HDAC inhibitors, which simultaneously inhibit multiple HDAC isoforms. Isoform selective HDAC inhibitors offer disease targeting with an improved toxicity profile. HDAC6 presents an important target due to its role in immune regulatory processes involved in antitumor immune responses. We have shown that selective inhibition of HDAC6 regulates macrophages to recognize, phagocyte, and present antigens to the adaptive immune system. Treatment with our selective HDAC6 inhibitor, SP-2-225, was shown to enhance the production of cancer-associated antigens and macrophage antigen cross-presentation to T cells. Through a non-cytotoxic mechanism, SP-2-225 significantly reduced the tumor volume in a syngeneic SM1 melanoma model. Analysis of the tumors from treated animals showed a significant shift in the M1/M2 ratio of the infiltrating macrophages as compared to control, indicating that SP-2-225 caused a pro-inflammatory, antitumor shift in the macrophage equilibrium surrounding the tumor. This was identified as the putative mechanism through adoptive cell therapy where macrophages from naive animals were harvested and treated ex-vivo with SP-2-225. Reimplantation of these SP-2-225 ex-vivo treated macrophages resulted in reduced tumor volumes when compared to both vehicle and untreated macrophage animal cohorts. We propose that this selective inhibitor of HDAC6 offers potential as a stand-alone cancer therapy and in combination with other immunotherapies and radiation treatments.

Citation Format: Scott Grindrod, Satish Noonepalle, Nima Aghdam, Alfredo Velena, Maria Gracia-Hernandez, Christian Zevallos-Delgado, Mira Jung, Anatoly Dritschilo, Alejandro Villagra. Immune-mediated tumor growth inhibition by selective HDAC6 inhibitor SP-2-225 [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO023.
Abstract PO033: Exposure to E-cigarette aerosol reduces the expression of Toll-like receptor 3 in lung epithelial cells
Authors: Brobst Daniel , Manyanga Jimmy , Georgescu Constantin , Wren Jonathan , Queimado Lurdes
Published: February 2021

Background and Aim: The use of conventional cigarettes is a major and preventable health problem and the leading cause of preventable morbidity and mortality. Electronic cigarettes have been shown to yield plasma nicotine levels similar to that seen in traditional cigarette users. E-cigarettes have been touted as a healthier alternative to traditional cigarettes and as a smoking cessation tool with mixed results. The increasing use of e-cigarettes by youth is concerning with 27.5% of high school students and 10.5% of middle school students reporting using e-cigarettes in 2019. Use among young adults (18-24) is increasing with 7.6% reporting use in 2018. Toll-like receptors (TLRs) are key sensors in the activation of innate immunity. In addition to activating antiviral and pro-inflammatory responses, TLR3 in particular has been shown to behave as a death receptor, causing apoptosis in cancer cells. TLR3 expression is reduced in the airway epithelial cells of smokers, leading to a reduction in the downstream expression of type I interferons following viral infection.

Methods: E-cigarette aerosol extracts were prepared from two brands of e-cigarettes, as previously described. Mainstream tobacco smoke extract was used as a positive control. Normal lung epithelial cells were exposed for 2 weeks to e-cigarette aerosol extracts at nicotine doses comparable to those observed in e-cigarette users. Whole-cell RNA was isolated. Gene expression was assessed by RNA-sequencing and validated by western blot.

Results: Exposure of lung epithelial cells to e-cigarette aerosol extracts significantly decreased the mRNA expression levels of TLR3 (p<0.0001). A significant reduction (p<0.0001) in the mRNA expression of downstream innate immune system molecules including RIG1, IRF7 and interferons was also observed. The reduction in gene expression was similar to that observed from traditional cigarette smoke extracts.

Conclusions: Our study suggests that exposure to e-cigarette aerosol can decrease the expression of key genes involved in innate immune response. TLR3 expression has been associated with good prognosis in early stage lung cancer. A decrease in TLR3 expression could allow tumors to evade immune surveillance and apoptosis

Citation Format: Daniel Brobst, Jimmy Manyanga, Constantin Georgescu, Jonathan Wren, Lurdes Queimado. Exposure to E-cigarette aerosol reduces the expression of Toll-like receptor 3 in lung epithelial cells [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO033.
Abstract PO051: Enhancing NK cell penetration of the tumor stroma using gene modification and nanomedicine
Authors: Bonan Nicole F. , Yvon Eric , Fernandes Rohan
Published: February 2021

Adoptive cell therapy has shown great success in treating liquid tumors. While T cells have been most commonly used for these indications, NK cells are emerging as a promising immune effector cell against solid tumors. Solid tumors present a more heterogeneous population of tumor antigens than liquid tumors, and NK cells, unlike T cells, can target multiple antigens to decrease the likelihood of antigen escape. NK cells can also be transplanted allogeneically with a lower risk of inducing graft-versus-host disease than T cells, which makes off-the-shelf NK cell therapy both simpler than T cell therapy and available to leukopenic patients. However, barriers to treating solid tumors with adoptive cell therapy remain, including the physical barrier of the dense stroma, which blocks immune cell infiltration. This project aims to develop an adoptive cell therapy to overcome this barrier. We tested the ability of cord blood-derived NK cells to kill mesothelioma tumor cell lines H226 and H2452 in the presence of heparanase, a heparan sulfate proteoglycan endoglucuronidase that both degrades the tumor stroma and stimulates NK cell invasion. We also conjugated this heparanase to FDA-approved Prussian blue nanoparticles to determine whether these nanoparticles might increase heparanase accumulation in the tumor and protect it from degradation. We used cytotoxicity assays, transwell invasion assays, and spheroid coculture assays to determine whether heparanase or hep-PBNPs aid NK cell cytotoxicity, invasion, and penetration. Surprisingly, our results indicate that PBNPs themselves may have heparanase activity. However, our invasion and penetration assays must be repeated to fully elucidate the effect of PBNPs and hep-PBNPs on NK cell invasion.

Citation Format: Nicole F. Bonan, Eric Yvon, Rohan Fernandes. Enhancing NK cell penetration of the tumor stroma using gene modification and nanomedicine [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO051.
Abstract PO061: Prognostic significance of S100A2 expression in patients with resected lung adenocarcinoma
Authors: Hung Jung-Jyh
Published: February 2021

Background: Lung cancer is the leading cause of cancer death worldwide. The S100 protein family has been reported to regulate inflammatory responses, cell cycle progression, differentiation, and play an important role in initiation and progression of a variety of human cancers. Overexpression of S100A2 has been reported in a variety of cancer types. S100A2 has been reported to be a putative tumor suppressor in the early stages of carcinogenesis in lung cancer. However, other reports showed that S100A2 overexpression was significantly associated with poor survival and increased metastasis in patients with resected lung cancer. Due to the discrepancies in the direction of prognosis in the literature, the prognostic value of S100A2 in lung cancer needs further demonstration.

Methods: The clinicopathological characteristics of 85 patients with lung adenocarcinoma at Taipei Veterans General Hospital were retrospectively reviewed. Expression of S100A2 was investigated using immunohistochemistry. Their prognostic significance in probability of overall survival and disease-free survival was analyzed.

Results: With a median follow-up time of 26.7 months (26.8 ± 6.3), the 2-year probability of overall survival rate was 94.7%. By immunohistochemistry, overexpression of S100A2 was identified in 17 (20.0%) of the 85 patients. S100A2 overexpression was not a significant prognostic factor for overall survival (P = 0.122). For disease-free survival, patients with stage I disease have significantly better disease-free survival than those with stage II or III disease (P < 0.001) in univariate analysis. Patients with S100A2 overexpression have a significantly worse disease-free survival (P = 0.028). In multivariate analysis, S100A2 overexpression was still a significant prognostic factor for worse disease-free survival (P = 0.019). Stage I disease was also a significant prognostic factor for better disease-free survival (P = 0.006).

Conclusions: Our study showed that S100A2 overexpression was a significant prognostic factor for worse disease-free survival in patients with resected lung adenocarcinoma.

Citation Format: Jung-Jyh Hung. Prognostic significance of S100A2 expression in patients with resected lung adenocarcinoma [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO061.
Abstract PO065: Single cell transcriptomics of triple negative breast cancer allografts following chemotherapy treatment reveals increased T cell abundance in doxorubicin-sensitive tumors
Authors: Hum Nicholas R. , Sebastian Aimy , Gilmore Sean F. , Gravano David M. , Rios-Arce Naiomy D. , Martin Kelly A. , Wheeler Elizabeth K. , Coleman Matthew A. , Loots Gabriela G.
Published: February 2021

The contribution of stromal cells on drug response in primary tumors remains unclear. To determine how individual cells within the stroma of triple negative breast cancer (TNBC) allografts respond to chemotherapy, we used single cell sequencing to profile cells present in murine tumors with or without exposure to doxorubicin. Doxorubicin is a chemotherapeutic agent commonly used to treat TNBC by inhibiting cancer cell proliferation through intercalation of DNA and preventing topoisomerase II activity. In this study, murine TNBC 4T1 cell line was utilized to generate allograft tumors in immunocompetent BALB/c mice. Syngeneic 4T1 tumors exhibit a range of responsiveness to doxorubicin treatment. Tumor growth rates were monitored throughout the chemotherapeutic regiment then stratified into sensitive or resistant response. Cellular composition and behavior were then analyzed via single cell RNA sequencing (scRNA-seq) and flow cytometry 8 days post-doxorubicin chemotherapeutic administration mimicking clinical treatment. ScRNA-seq revealed decreases in tumor infiltrating lymphocytes after doxorubicin exposure. Furthermore, an increase in T cell abundance was discovered in tumors sensitive to doxorubicin treatment. This finding was further supported by flow cytometric analysis showing a tumor specific increase in all, CD4+, and CD8+ T cell populations relative to resistant tumors. Additionally, T-cell differentiation, exhaustion, and activation states were further examined from scRNA-seq data providing insights into functional properties of the tumor residing T cell populations undergoing chemotherapeutic treatment. Future work will focus on analyzing prognostic value of specific T-cell populations in disease regression following doxorubicin treatment. This study received funding from LLNL LDRD grant 19-SI-003. This work was conducted under the auspices of the USDOE by LLNL (DE-AC52-07NA27344).

Citation Format: Nicholas R. Hum, Aimy Sebastian, Sean F. Gilmore, David M. Gravano, Naiomy D. Rios-Arce, Kelly A. Martin, Elizabeth K. Wheeler, Matthew A. Coleman, Gabriela G. Loots. Single cell transcriptomics of triple negative breast cancer allografts following chemotherapy treatment reveals increased T cell abundance in doxorubicin-sensitive tumors [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO065.
Abstract PO082: Significance of Treg cells in pathogenesis of oral squamous cell carcinoma
Authors: Aggarwal Sadhna , Sharma Suresh C. , Das Satya N.
Published: February 2021

Oral squamous cell carcinoma (OSCC) is one of the major cancers affecting in Asian countries. The main causative factor has been tobacco habit. It has been reported that immune dysfunction in these patients is one of the major factors for tumor growth and dissemination that affects disease free survival of the patients. We assessed the phenotypic and functional characteristics of Regulatory T (Treg) CD4+CD25+FoxP3+subsets in patients with OSCC by multicoloured flow cytometry. Subsequently we investigated the effects their inhibition via TDG on growth of OSCC cell lines in vitro. An increased (p<0.05) prevalence of Treg phenotypes (CD4+CD25+, CD4+FoxP3+, CD8+FoxP3+, CD4+CD25+FoxP3+) was observed in the peripheral circulation of OSCC patients that positively correlated with clinicopathological features. The increased frequency of CD4+CD8+CD25+FoxP3+, a unique T cell subset, CTLA4+, GITR+, NrP1+ and granzyme B+ (GzmB) Tregs also showed a significantly higher prevalence in OSCC patients. Functionally CD4+FoxP3+ Tregs showed skewed expression of IL2, IL10 and IL35 in patients as compared with the normal controls. Higher expression of TGFβ in tumor tissues suggests their dominant role in the up regulation of differentiation of Tregs from naive T cells in the tumor bearing host. Further, enhanced expression of CCR5 and CCR7 on Tregs with up regulation of their ligands (CCL5, CCL19 and CCL21) in tumor cells indicates efficient recruitment and trafficking of Tregs to the tumor site. Gal-1 expression was observed to be significantly higher in oral cancer patients. Treatment with βGBP showed growth promoting effects on Tregs and oral cancer cells. However, the treatment with its inhibitor TDG resulted in inhibition of Treg subsets and also decreased the frequency of IL10+ and IL35+ Tregs indicating its immunomodulatory effects. Hence, it seems reasonable to assume that modulation of functional dynamics of selective Treg subsets may be useful in enhancing anti tumor immunity and developing immunotherapeutic strategies for patients with oral squamous cell carcinoma.

Citation Format: Sadhna Aggarwal, Suresh C. Sharma, Satya N. Das. Significance of Treg cells in pathogenesis of oral squamous cell carcinoma [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO082.
Abstract PO084: Patterns of T cell clonal expansion in cancer patients associate with response to immunotherapy
Authors: Madireddi Shravan , Wu Thomas D. , de Almeida Patricia E. , Banchereau Romain , Chen Ying-Jiun J. , Chitre Avantika S. , Iftikhar Hina , O'Gorman William E. , Au-Yeung Amelia , Takahashi Chikara , Goldstein Leonard D. , Poon Chungkee , Keerthivasan Shilpa , Mariathasan Sanjeev , Das Thakur Meghna , Huseni Mahrukh A. , Ballinger Marcus , Estay Ivette , Caplazi Patrick , Modrusan Zora , Delamarre Lélia , Mellman Ira , Bourgon Richard , Grogan Jane L.
Published: February 2021

Upon encountering their cognate antigens, T cells can undergo clonal expansion to produce multiple copies of a cell with a shared T cell receptor (TCR). Despite the fundamental role of clonal expansion in cancer immunity, little is known about its relationship with T cell subpopulations or antitumor responses in cancer patients. Here we have performed single-cell RNA sequencing (scRNA-seq) and deep analysis of TCR clonotypes (scTCR-seq) in cancer patients across several indications, assessing the profiles of TCRs in the various populations of T cells in tumors, normal adjacent tissue (NAT), and peripheral blood. We found that, although most clonotypes were represented by a single cell, the remaining clonal lineages showed expansion in either NAT or tumor exclusively, or dual-residence with expansion in both compartments. In a subset of patients, we find clear evidence of clonotypic expansion of T effector- and effector memory-like cells not only within the tumor but also in NAT. Importantly, expanded clonotypes found in the tumor and NAT can also typically be detected in peripheral blood, suggesting a continuously replenishment from sites outside of the tumor with fresh, non-exhausted replacement cells. Our data further suggests a continued activity of the cancer immunity cycle in these patients, the acceleration of which may be associated with clinical response.

Citation Format: Shravan Madireddi, Thomas D. Wu, Patricia E. de Almeida, Romain Banchereau, Ying-Jiun J. Chen, Avantika S. Chitre, Hina Iftikhar, William E. O'Gorman, Amelia Au-Yeung, Chikara Takahashi, Leonard D. Goldstein, Chungkee Poon, Shilpa Keerthivasan, Sanjeev Mariathasan, Meghna Das Thakur, Mahrukh A. Huseni, Marcus Ballinger, Ivette Estay, Patrick Caplazi, Zora Modrusan, Lélia Delamarre, Ira Mellman, Richard Bourgon, Jane L. Grogan. Patterns of T cell clonal expansion in cancer patients associate with response to immunotherapy [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO084.
Abstract PO085: Cryogel-based cancer vaccine to treat acute myeloid leukemia
Authors: Najibi Alexander J. , Shah Nisarg J. , Shih Ting-Yu , Mao Angelo S , Sharda Azeem , Scadden David T. , Mooney David J.
Published: February 2021

Acute myeloid leukemia (AML) is a hematopoietic malignancy with limited therapeutic options. Standard-of-care chemotherapy depletes AML cells to induce remission, but often precedes disease relapse. To promote robust and durable immunity against AML, we developed a macroporous cryogel-based vaccine which provided a sustained release of GM-CSF to concentrate dendritic cells (DCs), TLR agonist CpG-ODN, and leukemia antigen. Prophylactic vaccination in mice against AML cell lysates or peptide antigen induced a potent anti-tumor adaptive immune response and prevented the engraftment of AML cells. This immunity was transferable, as bone marrow transplanted from vaccinated mice immunized recipients against AML. In models of established disease, only the combination of chemotherapy and biomaterial vaccination entirely eradicated AML in all mice and generated long-term T cell immunity preventing relapse. Notably, in combination with chemotherapy, a cryogel vaccine delivering no antigen (only GM-CSF and CpG-ODN) generated robust AML-specific T cell immunity, depleted leukemia, and enabled long-term survival. In this setting, tumor antigens were likely sourced from chemotherapy-induced AML cell death, as AML cells expressing high levels of apoptotic markers were found in the vaccine site and draining lymph node, co-localizing with DCs activated by the vaccine. These results demonstrate the capacity of a biomaterial-based vaccine to induce a potent immune response depleting AML and preventing relapse, even without defined antigen targets.

Citation Format: Alexander J. Najibi, Nisarg J. Shah, Ting-Yu Shih, Angelo S Mao, Azeem Sharda, David T. Scadden, David J. Mooney. Cryogel-based cancer vaccine to treat acute myeloid leukemia [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO085.
Abstract PO088: Sensitivity of cancer cells to oncolytic viruses is defined by IWS1 phosphorylation dependent epigenetic regulation of U2AF2 splicing and nucleocytoplasmic export of type I IFN transcripts
Authors: Laliotis Georgios I. , Kenney Adam D. , Chavdoula Evangelia , Orlacchio Arturo , Anastas Vollter , La Ferlita Alessandro , Kaba Abdul , Sehgal Lalit , Coppola Vincenzo , Yount Jacob S. , Tsichlis Philip N.
Published: February 2021

We have previously shown that loss of IWS1 phosphorylation promotes the alternative RNA splicing of U2 Associated-Factor 2 (U2AF2), resulting in transcripts lacking exon 2. This exon encodes part of the Serine-Rich (SR) domain of U2AF65, which is responsible for its binding with pre-mRNA Processing Factor 19 (Prp19). Here, we show that whereas both U2AF65 isoforms bind cytoplasmic accumulation response elements (CAR-E) of intronless mRNAs, the loading of Prp19 occurs only in exon 2-containing U2AF65, in cells expressing phosphorylated IWS1, promoting their nucleocytoplasmic export. Furthermore, this Prp19 loading is RNA Pol II dependent. Given that IFNA1 and IFNB1 are among the target genes, the expression of IFNα and IFNβ was decreased in cells deficient in IWS1 phosphorylation, and their sensitivity to the oncolytic VSV and Reovirus virus infection was increased accordingly. More importantly, treatment of the lung adenocarcinoma cells with the pan-AKT inhibitor, MK2206 phenocopied the loss of IWS1 phosphorylation and showed increased sensitivity to oncolytic viral infection. These data identify a novel mechanism by which the AKT/p-IWS1 axis, via the epigenetic regulation of alternative RNA splicing, contribute to the sensitivity to oncolytic viruses.

Citation Format: Georgios I. Laliotis, Adam D. Kenney, Evangelia Chavdoula, Arturo Orlacchio, Vollter Anastas, Alessandro La Ferlita, Abdul Kaba, Lalit Sehgal, Vincenzo Coppola, Jacob S. Yount, Philip N. Tsichlis. Sensitivity of cancer cells to oncolytic viruses is defined by IWS1 phosphorylation dependent epigenetic regulation of U2AF2 splicing and nucleocytoplasmic export of type I IFN transcripts [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PO088.
Abstract PR005: Highly potent fully human anti-VISTA antibodies – A new target checkpoint inhibitor against immunosuppressive myeloid cells
Authors: Guillaudeux Thierry , Tarcha Eric , Bader Robert , Dutzar Benjamin , Eyde Nathan , Frazier Emily , Jurchen David , Lance Remington , Loomis Cristina , Lustig Kurt , Ovechkina Yulia , Peckham David , Posakony Jeff , Sridhar Shaarwari , Xu Mei , Iadonato Shawn
Published: February 2021

V-domain Immunoglobulin Suppressor of T cell Activation (VISTA/PD-1H) is a B7 family ligand expressed on circulating and intratumoural myeloid cells as well as Treg and NK cells. It has been shown to inhibit T cell responses in vitro and in preclinical models. In patients, VISTA is also a potential mediator of resistance to anti-CTLA-4 and anti-PD1 therapies and therefore is a valuable new target for cancer immunotherapy. Kineta has analyzed 107 fully human ScFv antibodies directed against VISTA. Our lead candidates exhibit high potencies in the subnanomolar range and are also characterized by a long kDis. They specifically target human and cynomolgus monkey VISTA on a singular unique epitope. In a Staphylococcus Enterotoxin B T-cell activation assay, Kineta’s anti-VISTA antibodies efficiently induce IFNg secretion. They also promote strong maturation of Antigen Presenting Cells with an increase of CD80 and HLA-DR surface expression as well as CXCL10 secretion. The mechanism of action is mediated in part by NK cells. We demonstrated that myeloid cells acquire a high level of VISTA expression during MDSC or M2 differentiation in vitro and that Kineta’s anti-VISTA antibodies prevent the differentiation of MDSC as well as their immunosuppressive activity against T cells. Anti-VISTA antibodies mediate single-agent antitumor effects in syngeneic tumor models in wild-type mice and show enhanced activity in combination with anti-PD1 and anti-CTLA-4 treatment. Candidate anti-VISTA antibodies have also been evaluated in exploratory tolerability and PK studies in cynomolgus monkey. These studies demonstrated that multiple weekly doses of antibodies are well-tolerated with appropriate PK for lead selection and optimization. Our results strongly favor further characterization and continued development of selected lead antibodies for the potential treatment of colder, less immunogenic tumors.

This abstract is also being presented as PO035.

Citation Format: Thierry Guillaudeux, Eric Tarcha, Robert Bader, Benjamin Dutzar, Nathan Eyde, Emily Frazier, David Jurchen, Remington Lance, Cristina Loomis, Kurt Lustig, Yulia Ovechkina, David Peckham, Jeff Posakony, Shaarwari Sridhar, Mei Xu, Shawn Iadonato. Highly potent fully human anti-VISTA antibodies – A new target checkpoint inhibitor against immunosuppressive myeloid cells [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR005.
Abstract PR009: The functional genomic landscape of recurrent glioblastoma
Authors: Chokshi Chirayu , Tieu David , Brown Kevin , Venugopal Chitra , Liu Lina , Kuhlman Laura , Chan Katherine , Tong Amy , Savage Neil , McKenna Dillon , Aghaei Nikoo , Subapanditha Minomi , Salamoun Joseph M , Rossotti Martin , Wipf Peter , Sharlow Elizabeth , Lazo John S. , Kislinger Thomas , Henry Kevin , Lu Yu , Moffat Jason , Singh Sheila K.
Published: February 2021

Glioblastoma (GBM) is a highly fatal brain cancer where mortality is predominantly caused by disease recurrence and lack of second-line therapies. Here, utilizing genome-wide CRISPR-Cas9 screening, we uncover treatment-based conditional genetic interactions modulating sensitivity to combined radiation therapy (RT) and temozolomide (TMZ), the standard of care treatment administered to over 70% of glioblastoma patients. To investigate therapy-induced changes in the functional landscape of glioblastoma stem cells (GSCs) without confounding patient-to-patient differences, we systematically mapped genetic dependencies in patient-matched pre-treatment primary and post-treatment recurrent GSCs. This comparison highlights a remodelling of genes and pathways regulating tumor cell survival at disease relapse, arming recurrent GSCs with newly acquired genetic drivers and further loss of tumor suppressors. Among these genes, we identify PTP4A2, encoding protein tyrosine phosphatase 4A2, as a major regulator of stemness and tumorigenicity in recurrent GSCs. Genetic perturbation or pharmacological inhibition of PTP4A2 influences the phosphorylation status and expression of interacting proteins belonging to axonal guidance pathways, as phosphoproteomic studies showed specific enrichment in axon guidance regulator Roundabout Guidance Receptor 1 (ROBO1) in recurrent GSCs. We therefore designed and developed efficacious Camelid biotinylated single-domain antibody (bio-sdAb) and tetrameric complexes targeting human ROBO1 (MKRo-20). Subsequently, we orthotopically engrafted recurrent GSCs into immunocompromised mice and administered local treatments of tetrameric MKRo-20. All mice treated with tetrameric MKRo-20 were rendered tumor free, suggesting that modulation of ROBO1 with bio-sdAbs presents a new immunotherapeutic strategy to target recurrent glioblastoma. Our work reveals a context-specific dependence on axonal guidance through a PTP4A2-ROBO axis in recurrent glioblastoma, highlighting new avenues of therapeutic intervention for second-line therapy in GBM.

This abstract is also being presented as PO025.

Citation Format: Chirayu Chokshi, David Tieu, Kevin Brown, Chitra Venugopal, Lina Liu, Laura Kuhlman, Katherine Chan, Amy Tong, Neil Savage, Dillon McKenna, Nikoo Aghaei, Minomi Subapanditha, Joseph M Salamoun, Martin Rossotti, Peter Wipf, Elizabeth Sharlow, John S. Lazo, Thomas Kislinger, Kevin Henry, Yu Lu, Jason Moffat, Sheila K. Singh. The functional genomic landscape of recurrent glioblastoma [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR009.
Abstract PR010: Potentiating the efficacy of immune checkpoint blockade by targeting the epithelial-to-mesenchymal transition (EMT) in breast carcinomas
Authors: Dongre Anushka , Rashidian Mohammad , Ng Eaton Elinor , Reinhardt Ferenc , Thiru Prat , Zagorulya Maria , Nepal Sunita , Banaz Tuba , Martner Anna , Spranger Stefani , Weinberg Robert A.
Published: February 2021

The epithelial-to-mesenchymal transition (EMT), which conveys epithelial (E) carcinoma cells to quasi-mesenchymal (qM) states, enables these cells to gain tumor-initiating stem like abilities, metastasize and acquire resistance to several drug and chemotherapeutic regimens. In addition to these aforementioned features, we have recently demonstrated that the EMT program also contributes to the generation of an immunosuppressive tumor microenvironment (TME) in breast carcinomas and confers resistance to immune checkpoint blockade therapies. Specifically, qM tumors recruit immunosuppressive cells to their TME and are refractory to checkpoint blockade, while E tumors recruit CD8+ T-cells instead and are sensitive to checkpoint blockade. Importantly, minority populations of qM cells within a tumor can cross-protect their more E neighbors from immune attack. The underlying mechanisms by which this immunosuppression and cross-protection are achieved have been unclear. Using a combination of novel E and qM tumor models arising in syngeneic immunocompetent hosts combined with CRISPR/Cas9 and transcriptomic approaches, we demonstrate that qM but not E tumors are specifically associated with an immunosuppressive gene signature. Furthermore, abrogation of carcinoma cell-derived factors (CD73, Csf1 or Spp1) specifically associated with the qM state, prevents the assembly of an immunosuppressive TME and sensitizes otherwise refractory qM tumors partially or completely to checkpoint blockade immunotherapy. Taken together, our work indicates that carcinoma cell-intrinsic factors specifically associated with residence in the qM state can directly influence their response to anti-tumor immunity and checkpoint blockade. As a result, this work brings to the forefront the possibility of using the epithelial-mesenchymal state of carcinoma cells as an important surrogate marker that can be used to predict responses to immune checkpoint blockade therapies.

This abstract is also being presented as PO038.

Citation Format: Anushka Dongre, Mohammad Rashidian, Elinor Ng Eaton, Ferenc Reinhardt, Prat Thiru, Maria Zagorulya, Sunita Nepal, Tuba Banaz, Anna Martner, Stefani Spranger, Robert A. Weinberg. Potentiating the efficacy of immune checkpoint blockade by targeting the epithelial-to-mesenchymal transition (EMT) in breast carcinomas [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR010.
Abstract PR011: Selective inhibition of VEGF binding to VEGFR2 promotes an immune stimulatory microenvironment in murine models of breast cancer
Authors: Zhang Yuqing , Huang Huocong , Sorrelle Noah , Brekken Rolf
Published: February 2021

Vascular endothelial growth factor-A (VEGF) is the dominant angiogenic factor that promotes tumor neovascularization, making it a critical target for cancer therapy. VEGF binds and activates VEGF receptor 1 (VEGFR1) and VEGFR2, with VEGFR2 being the principal receptor mediating VEGF-induced angiogenesis while VEGFR1 has a negative regulatory effect on this process. Previously, we found that selective inhibition of VEGF binding to VEGFR2 with a fully human monoclonal antibody (r84) or its mouse chimeric counterpart (mcr84) is sufficient for effective control of tumor growth in preclinical models of breast cancer. However, accumulating evidence indicates that the effect of blocking VEGF activity in solid tumors extends beyond inhibition of angiogenesis. Concordantly, we have shown that VEGF blockade regulates immune cell trafficking across the endothelium by increasing the expression of adhesion molecules while decreasing FasL expression on tumor vasculature. In addition, specifically blocking VEGF binding to VEGFR2 promotes an immune stimulatory microenvironment by enhancing activation of CD8+ cytotoxic T cells as evidenced by elevated secretion of Granzyme B and IFN-γ. In addition, VEGF blockade also reduces FoxP3+ regulatory T cell infiltration in multiple murine models of cancer. We and others have shown that immune cells express receptors for VEGF. Our data indicate that VEGFR2 expression is elevated on myeloid cells selectively in tumor-bearing animals. Consistent with VEGFR2 expression, treatment with mcr84 results in a reduction in macrophage/myeloid cell infiltration into murine breast tumors. In conclusion, our results enhance understanding of the function of VEGFR2 signaling on myeloid cells and suggest that selective inhibition of VEGF from binding VEGFR2 facilitates immune activation landscape in breast cancer models, which might enhance the efficacy of immune checkpoint blockade.

This abstract is also being presented as PO045.

Citation Format: Yuqing Zhang, Huocong Huang, Noah Sorrelle, Rolf Brekken. Selective inhibition of VEGF binding to VEGFR2 promotes an immune stimulatory microenvironment in murine models of breast cancer [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2020 Oct 19-20. Philadelphia (PA): AACR; Cancer Immunol Res 2021;9(2 Suppl):Abstract nr PR011.