bluuebunny/crossref_metadata_2025 huggingface dataset:
Abstract B38: Altered p53 status confers molecular subtype-dependent distinct interactions with fibroblasts in breast cancer
Authors: Sandhu Rupninder , D'Arcy Monica , Troester Melissa A.
Published: May 2015

Different molecular subtypes of breast cancer have distinct interactions with stromal and immune cells in the cancer microenvironment. However, the role of specific somatic mutations in mediating stromal interactions is not well understood. Conversely, the role of stromal interactions in modulating the biological effects of tumor genetic events is understudied. This project hypothesized that (a) p53 mutations may modulate stromal-epithelial interactions, and (b) stromal-epithelial interactions may potentiate the effects of p53 loss. The p53 gene is mutated in 50% of breast cancers, with 84% of basal-like breast cancers harboring p53 mutations, compared to just 12-32% of luminal breast cancers. The influence of p53 loss on stromal-epithelial interactions across different molecular subtypes may have important implications for tumor progression. To study how gene expression of fibroblast-epithelial cocultures differ in luminal vs. basal-like breast cancers as a function of p53 status, we employed RNAi-mediated p53 knockdown (KD) in a panel of four epithelial cell lines (two basal-like, two luminal). Cocultures were carried out with p53-wildtype or KD cell lines maintained in direct physical contact with fibroblasts for 48 hours before RNA isolation. Results of gene expression analysis show that p53 knockdown significantly altered cell-cell interactions in a subtype-specific manner. Comparing cocultures of p53-wildtype to cocultures of p53 KD basal-like cells, we identified 1600 genes whose expression was significantly altered. Among luminal breast cancer cocultures, the impact of p53 loss on gene expression was far more limited, with no genes identified at the same level of significance. Among basal-likes, p53 loss-associated gene expression occurred in immune response pathways, including IL-8 signaling, IL-15 signaling LXR/RXR activation, TREM1 signaling, B cell receptor signaling. In addition, Wnt/β-catenin Signaling was altered in coculture due to p53 loss. Other recent studies have indicated that p53 may modulate Wnt signaling and EMT via a microRNA-dependent mechanism, and these findings suggest that the p53-Wnt axis is also modulated by stromal-epithelial interactions. These observations strongly suggest that the interactions of epithelial cells with fibroblasts are significantly affected by p53 status. Given the high frequency of basal-like tumors with p53 mutations, it is important to understand how stromal-epithelial interactions potentiate the effects of p53 loss.

Citation Format: Rupninder Sandhu, Monica D'Arcy, Melissa A. Troester. Altered p53 status confers molecular subtype-dependent distinct interactions with fibroblasts in breast cancer. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B38. doi:10.1158/1538-7445.CHTME14-B38
Abstract B49: Molecular characterization of breast tumor-associated adipose
Authors: Yarina William C. , Field Lori A. , Deyarmin Brenda , Laar Ryan van , Hooke Jeffrey A. , Shriver Craig D. , Ellsworth Rachel E.
Published: May 2015

Background: Long thought to function only as an inert energy storage depot, the role of adipose tissue in breast tumorigenesis has been largely ignored. In light of increasing rates of obesity and use of breast conserving therapy and autologous fat grafting, improved understanding of the role of adipose in tumor etiology is crucial.

Methods: Adipose adjacent to and distant from invasive breast tumors (n=20), or adjacent to non-malignant diagnoses (n=20) was laser microdissected from post-menopausal women. Gene expression data were generated using microarrays and data analyzed to identify significant patterns of differential expression between adipose groups, at the individual gene and molecular pathway level.

Results: Pathway analysis revealed significant differences in immune response between non-malignant, distant and tumor adjacent adipose, with the highest response in tumor-adjacent and lowest in non-malignant adipose. Adipose from invasive breasts exhibits increased expression in anti-inflammatory genes, such as MARCO and VSIG4, while genes differentially expressed between tumor-adjacent and distant adipose such as SPP1, RRM2 and MMP9, are associated with increased cellular proliferation, invasion, and angiogenesis.

Conclusions: Gene expression levels differ in breast adipose, depending on presence of or proximity to tumor cells. Heightened immunotolerance in adipose from invasive breasts provides a microenvironment favorable to tumorigenesis. In addition, tumor-adjacent adipose demonstrates expression of genes associated with tumor growth and progression. Together, these data suggest that adipose is not an inert component of the breast microenvironment but plays an active role in tumorigenesis.

Citation Format: William C. Yarina, Lori A. Field, Brenda Deyarmin, Ryan van Laar, Jeffrey A. Hooke, Craig D. Shriver, Rachel E. Ellsworth. Molecular characterization of breast tumor-associated adipose. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B49. doi:10.1158/1538-7445.CHTME14-B49
Abstract B50: Visualizing intercellular transfer of hypoxia-induced exosomal miR-210 between breast cancer cells
Authors: Jung Kyung Oh , Kim Young-Hwa , Chung June-Key , Youn Hyewon
Published: May 2015

Purpose: Cancer cells actively release exosomes containing many functional proteins, mRNA, and miRNA to communicate with tumor microenvironment, providing a novel mechanism of paracrine signaling between the tumors and surrounding tissues. In this study, we visualized exosome-mediated transfer of miR-210 between breast cancer cells .

Methods: Mouse breast cancer cell lines, 4T1, were transfected with pCMV-luc2/miR-210 reporter vector which was designed to be turned off its luciferase signal by binding of miR-210. Hypoxia was induced by Deferoxamine Mesylate (DFO). Exosomes were characterized by western blot (Alix, CD63, and CD9) and TEM. Exosomes from hypoxic conditions were isolated and treated to normoxic breast cancer cells. Real-time PCR was performed to compare levels of miR-210. Luciferase activity was measured by luciferase activity assay and bioluminescence imaging. Immunohistochemistry was performed with antibodies of HIF-1a, luciferase, and Ephrin-A3.

Results: Amount of isolated exosome from hypoxic condition was 1.4 fold more than that of normoxic condition. Expression of miR-210 was increased in 15.70 and 12.73 fold in hypoxic cells and exosomes, respectively. Luciferase activity and bioluminescence imaging signal intensity of the cells treated with hypoxic exosome were significantly decreased at 0.50 and 0.67 fold compare to that of untreated cells. In xenograft models, luciferase signals of tumor treated hypoxic exosomes were also decreased in 0.56 fold. Luciferase was decreased in the tumor tissues treated with hypoxic exosomes, and the expression of Ephrin-A3, a target of miR-210, was also decreased in tumor tissues treated hypoxic exosome.

Conclusions: Reporter gene imaging system for monitoring hypoxia-induced miR-210 successsfully demonstrated the exosome-mediated intercellular transfer of miR-210 in vitro and in vivo.

Citation Format: Kyung Oh Jung, Young-Hwa Kim, June-Key Chung, Hyewon Youn. Visualizing intercellular transfer of hypoxia-induced exosomal miR-210 between breast cancer cells. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B50. doi:10.1158/1538-7445.CHTME14-B50
Abstract B51: SOCS3 deficiency in myeloid cells promotes prostate tumor development
Authors: Yu Hao , Liu Yudong , Deshane Jessy , Benveniste Etty (Tika) , Qin Hongwei
Published: May 2015

Suppressor Of Cytokine Signaling (SOCS) proteins are negative regulators of the JAK/STAT pathway, and have been implicated as functioning as tumor suppressors, particularly SOCS3. We have previously demonstrated that specific deletion of SOCS3 in myeloid cell leads to heightened activation of STAT3 and downstream STAT3 target gene expression. STAT3 activation has been strongly implicated in contributing to prostate cancer progression and metastasis. STAT3 signaling in myeloid cells has been demonstrated to attenuate anti-tumor immunity. Thus, we evaluated the impact of SOCS3 deletion in myeloid cells in a murine prostate tumor model. We demonstrate that prostate tumor growth is significantly enhanced in myeloid-specific SOCS3-deficient mice, which correlates with elevated levels of Myeloid Derived Suppressor Cells (MDSC) in both the spleen and tumor microenvironment, and less CD8+ T-cell infiltration in tumors. Furthermore, SOCS3-deficient bone-marrow-derived mononuclear cells exhibit heightened STAT3 activation and are preferentially differentiate into MDSC phenotype. Importantly, we identify granulocyte-colony stimulating factor (G-CSF) as a critical factor secreted by the prostate tumor microenvironment that promotes development of Gr-1+CD11b+ cells via a STAT3-depentent pathway. Abrogation of tumor-derived G-CSF reduced the proliferation and accumulation of Gr-1+CD11b+ cells and inhibited prostate tumor growth. Therefore, the tumor-derived cytokine, G-CSF, is a prospective candidate upstream of the STAT3/SOCS3 pathway in MDSC differentiation from the bone marrow. These findings highlight the critical function of SOCS3 as a negative regulator of MDSC development and function, which may contribute to tumor suppressor attributes of SOCS3.

Citation Format: Hao Yu, Yudong Liu, Jessy Deshane, Etty (Tika) Benveniste, Hongwei Qin. SOCS3 deficiency in myeloid cells promotes prostate tumor development. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B51. doi:10.1158/1538-7445.CHTME14-B51
Abstract B58: Visualization of ERK and PKA activities in the tumor microenvironment comprising of lung-metastasized 4T1 murine breast tumor cells
Authors: Kamioka Yuji , Matsuda Michiyuki
Published: May 2015

Tumor microenvironment comprising of fibroblasts, endothelial cells, immune cells and tumor cells play critical roles in the tumor development. The complexities and dynamic changes of interactions among the constituting cells hampers comprehensive understanding of tumor microenvironment by conventional methods such as immunohistochemistry of tissue or biochemical analyses. Recently, intravital imaging have been providing unprecedented insight into tumor microenvironment. From the perspective of imaging, fluorescent imaging based on the principle of Förster resonance energy transfer (FRET) provides important information about cellular events that cannot be obtained by other methods. Genetically-encoded FRET biosensors have been widely used in biology to visualize the spatiotemporal dynamics of signaling molecules. Despite the increasing multitude of these biosensors, their application has been mostly limited to cultured cells with transient biosensor expression, due to difficulties in stable expression of FRET biosensors. We have recently reported the efficient generation of transgenic mouse lines expressing heritable and functional biosensors for ERK and PKA. These transgenic mice were generated by the cytoplasmic co-injection of Tol2 transposase mRNA and a circular plasmid harboring Tol2 recombination sites. Observation of these transgenic mice by two-photon excitation microscopy enabled us to visualize the activities of ERK and PKA in live tissues. Here, we report the visualization of ERK and PKA activities in 4T1 mammary tumor cells metastasized to lung tissue, which enabled us to observe effect of tumor microenvironment. We have also developed the imaging system to stabilize the live lung tissue to obtain stable images with the reduction of image blurring caused by breathing. We hereby demonstrate the utility of a three-dimensional, intravital FRET imaging technique toward understanding the mechanisms underlying tumor invasion and metastasis.

Citation Format: Yuji Kamioka, Michiyuki Matsuda. Visualization of ERK and PKA activities in the tumor microenvironment comprising of lung-metastasized 4T1 murine breast tumor cells. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B58. doi:10.1158/1538-7445.CHTME14-B58
Abstract B64: Alternagin-C, an α2β1 integrin-binding disintegrin-like protein, induces distinct cell responses in fibroblasts, tumor breast and endothelial cells in vitro
Authors: Santosa Lívia Mara , Vieira Tamires de Castro , Selistre-de-Araújo Heloísa Sobreiro
Published: May 2015

Reciprocal interactions between tumor, stromal cells and the extracellular matrix (ECM) are considered crucial steps for tumor development and progression. Both tumor and stromal cells secrete metalloproteases (MMPs) that modify the tumor microenvironment by degrading the ECM and releasing growth factors that may induce tumor cell proliferation, migration and invasion. MMPs activation is stimulated by co-activation of integrins, major cell-surface adhesion receptors. Disintegrins are strong integrin inhibitors found in snake venoms and used as prototypes for angiogenesis inhibitors. Alternagin-C (Alt-C), a disintegrin-like, Cys-rich protein isolated from Bothrops alternatus snake venom, has strong affinity for α2β1 integrin. ALT-C inhibited adhesion to collagen I of a variety of tumor cell lines, and in low concentrations, it induces VEGF expression and angiogenesis in an in vivo matrigel model. However, its mechanism of action was not very clear and it seems to depend on the cell type. Here, we show that ALT-C inhibited MMP-9 activity and mRNA expression in human breast cancer (MDA-MB-231) and MMP-2 activity in human micro vascular endothelial cells (HMEC-1) conditioned media from monocultures. ALT-C also increased the expression of angiogenic genes such as VEGF-A in fibroblasts and tumor cells but not in HMEC-1. However, ALT-C upregulated c-MYC mRNA expression only in tumor cells. ALT-C (10, 40, 100 and 1000 nM) also inhibited transendothelial migration of MDA-MB-231 cells through a monolayer of HMEC-1. In conclusion, these results suggest that α2β1 integrin binding by ALT-C may induce distinct effects in different cell lines by modulating MMP activity and stimulating the expression of angiogenic factors that influence tumor progression. These results may be very useful for medical and biotechnological applications in the development of anti-angiogenic and anti-metastatic therapies.

Support: FAPESP, CNPq, CAPES (Brazil)

Citation Format: Lívia Mara Santosa, Tamires de Castro Vieira, Heloísa Sobreiro Selistre-de-Araújo. Alternagin-C, an α2β1 integrin-binding disintegrin-like protein, induces distinct cell responses in fibroblasts, tumor breast and endothelial cells in vitro. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B64. doi:10.1158/1538-7445.CHTME14-B64
Abstract B78: Bone marrow-derived mesenchymal stem cells promote colorectal cancer progression through paracrine neuregulin 1/HER3 signaling
Authors: Wever Olivier De , Boeck Astrid de
Published: May 2015

Objective: Bone marrow-derived mesenchymal stem cell (BM-MSC) migrate to primary tumors and drive tumor progression. This study aimed to identify the molecular mechanisms associated with these heterotypic cellular interactions and analyse their relevance in colorectal cancer (CRC).

Design: Paracrine interactions of BM-MSC and tumor-derived mesenchymal cells (T-MC) with CRC cells were studied using collagen invasion assays, cell counts, flow cytometric cell-cycle analysis and tumor xenograft models. The role of neuregulin 1 (NRG1) and the human epidermal growth factor receptor (HER) family pathways were investigated using tyrosine kinase assays, mass spectrometry, pharmacological inhibition, antibody-mediated neutralisation and RNA interference. Transmembrane NRG1 (tNRG1), HER2 and HER3 expression was analysed in primary CRCs (n = 54), adjacent normal colorectal tissues (n = 4), liver metastases (n = 3) and adjacent normal liver tissues (n = 3) by immunohistochemistry.

Results: BM-MSC and T-MC stimulate invasion, survival and tumorigenesis of CRCs through release of soluble NRG1, activating the HER2/HER3-dependent PI3K/AKT signaling cascade in CRC cells. Mesenchymal cells in primary CRCs demonstrate high tNRG1 expression. HER2 and HER3 show membrane localization in cancer cells of CRC tissue. High stromal tNRG1 expression is significantly associated with advanced UICC stage (P = .005) and invasion depth (P = .04) and decreased 5-year progression-free-survival (PFS) (P = .01).

Conclusion: Paracrine NRG1/HER3 signals initiated by BM-MSC and T-MC promote CRC cell progression, and high tNRG1 expression is associated with poor prognosis.

Citation Format: Olivier De Wever, Astrid de Boeck. Bone marrow-derived mesenchymal stem cells promote colorectal cancer progression through paracrine neuregulin 1/HER3 signaling. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B78. doi:10.1158/1538-7445.CHTME14-B78
Abstract B79: TIMP-2 mediated growth inhibition of human glioma U87MG is accompanied by elevated IGFBP7 and FSP-1/S100A4 expression at the tumor/stroma interface
Authors: Jensen-Taubman Sandra , Bourboulia Dimitra , Han Huiying , Moss Laurie Shuman , Wei Beiyang , Stetler-Stevenson William G.
Published: May 2015

The tissue inhibitor of matrix metalloproteinase–2 (TIMP-2) belongs to a small family of multifunctional secreted proteins that inhibit matrix metalloproteases (MMPs), proteases principally associated with promoting tumor invasion and metastasis. We have previously shown that forced TIMP-2 expression inhibits human lung tumor growth through MMP-independent mechanisms including tumor cell apoptosis and upregulation of insulin growth factor binding protein-7 (IGFPB7), a protein reported to function as a potential tumor suppressor in a variety of tumor types including human glioma. In the current study, we used immunohistochemistry, TUNEL assay, and dual immunofluorescence to assess the growth inhibitory effects of TIMP-2 in human glioma xenografts generated using U87MG cells lentivirally transfected to overexpress the human TIMP-2 cDNA sequence (U87MG-T2) or vector alone (U87MG-EV). Compared to EV controls, U87MG-T2 xenografts demonstrated a significant inhibition of tumor growth, accompanied by increased tumor cell apoptosis at the tumor edge. Moreover, a dramatic increase in IGFBP7 and fibroblast specific protein-1 (FSP1)/S100A4 was detected in distinct subpopulations of non-tumor cells at the tumor/stroma interface, whereas both markers were sparsely observed in U87MG-EV controls. In an effort to determine the origin of IGFBP7 positive cells, we performed dual immunofluorescence using antibodies to the blood vessel marker CD34, FSP-1/S100A4, and human mitochondria (clone 113-1). IGFBP7 positive cells did not co-express any of the three markers analyzed, indicating that IGFBP7 positive cells are host derived and consist of cells other than blood vessels or stromal fibroblasts. We conclude that endogenous TIMP-2 significantly inhibits human glioma tumor growth in vivo through tumor cell apoptosis and tumor-host interactions involving discrete subsets of non-tumor cells in the adjacent tumor microenvironment.

Citation Format: Sandra Jensen-Taubman, Dimitra Bourboulia, Huiying Han, Laurie Shuman Moss, Beiyang Wei, William G. Stetler-Stevenson. TIMP-2 mediated growth inhibition of human glioma U87MG is accompanied by elevated IGFBP7 and FSP-1/S100A4 expression at the tumor/stroma interface. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr B79. doi:10.1158/1538-7445.CHTME14-B79
Abstract IA03: Combinatorial targeting of endothelial growth factor pathways
Authors: Alitalo Kari K.
Published: May 2015

Solid tumors require blood vessels for growth and dissemination, and use lymphatic vessels as additional conduits for metastatic spread. The identification of growth factor receptor pathways regulating angiogenesis has led to clinical approval of the first anti-angiogenic molecules targeted against the vascular endothelial growth factor (VEGF)-VEGFR-2 pathway. However, in many cases resistance to anti-VEGF-VEGFR therapy occurs, and thus far the clinical benefit has been limited to only modest improvements in overall survival. Therefore, novel treatment modalities are required. I will discuss the other members of the VEGF-VEGFR family, as well as the angiopoietin growth factors and their Tie2 receptor as targets for the inhibition of tumor angiogenesis, lymphangiogenesis and metastasis. Our recent studies reveal that also the orphan receptor Tie1 is crucial for tumor angiogenesis and growth, but not for steady-state function of the vasculature. Combinatorial targeting of multiple vascular growth factor pathways shows promise for improving the efficacy of anti-angiogenic tumor therapy.

Citation Format: Kari K. Alitalo. Combinatorial targeting of endothelial growth factor pathways. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA03. doi:10.1158/1538-7445.CHTME14-IA03
Abstract IA05: Granulocytic cells in metastasis
Authors: Acharyya Swarnali
Published: May 2015

Cancer progression is a complex process that involves tumor growth at the primary site coupled with dissemination and outgrowth at distant sites also known as metastasis. Majority of the cancer-related deaths are due to metastasis commonly occurring in the bone, lung, liver and brain. Although progress has been made in deciphering the process of tumor initiation and primary tumor growth, the molecular underpinnings and mechanisms of metastasis remain poorly understood. Given the role of the tumor microenvironment in cancer progression, there has been a growing interest in understanding the function of granulocytic myeloid cells, an abundant component of the peripheral blood and tumor microenvironment. Using multiple models of breast cancer metastasis, we have characterized two distinct subpopulations of CD11b+Ly6G+ granulocytic myeloid cells in peripheral blood by RNA sequencing and proteomic profiling. The first subpopulation is abundant early before any detectable metastasis. A second subpopulation is abundant late coinciding with systemic metastasis. We have identified a network of paracrine signals between carcinoma and CXCR2 expressing CD11b+Ly6G+ granulocytic cells that drive metastasis. We find that CXCL1/2 chemokines from metastatic cells attract CD11b+Ly6G+ granulocytic myeloid cells, which in turn produce survival factors called S100A8/9 that promotes metastatic progression. Pharmacological inhibition of the CXCR2 axis in combination with chemotherapeutic agents significantly reduces multi-organ metastasis. We envision that a delicate balance exists between different granulocytic populations that function as a determinant of metastatic progression.

Citation Format: Swarnali Acharyya. Granulocytic cells in metastasis. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA05. doi:10.1158/1538-7445.CHTME14-IA05
Abstract IA10: Targeting master regulators of damage responses in the tumor microenvironment
Authors: Nelson Peter S.
Published: May 2015

The armamentarium of therapeutics used to treat cancer patients relies heavily on ionizing radiation and chemotherapeutic drugs that severely damage DNA. The responses of tumor cells to these treatments is heavily influenced by their tumor micro environment (TME): physical contacts with structural elements comprising tissues, associations with resident and transient non-malignant cells, and interactions with numerous soluble endocrine and paracrine-acting factors all influence tumor cell behavior. Importantly, this TME is not static and dynamically responds to a variety of stimuli. This discussion will detail emerging data indicating that genotoxic cancer treatments activate highly conserved damage response programs in benign cells comprising the TME. These damage signals culminate in a developmentally conserved, powerful and diverse secretory program, the DNA Damage Secretory Program (DDSP) that generates a proangiogenic, pro-inflammatory microenvironment, and also promotes adverse tumor cell phenotypes including enhanced resistance to treatment. Key master regulators of the DDSP have been identified and offer opportunities for therapies co-targeting tumor cells along with key survival mediators from the TME. A detailed understanding of these survival signals induced in the context of genotoxic stress provides a platform to develop combinatorial strategies to improve outcomes that consider malignant cells, the tumor microenvironment, and the dynamics exerted by the treatment itself.

Citation Format: Peter S. Nelson. Targeting master regulators of damage responses in the tumor microenvironment. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA10. doi:10.1158/1538-7445.CHTME14-IA10
Abstract IA13: A hypoxic microenvironment influences pancreatic cancer progression
Authors: Simon M. Celeste
Published: May 2015

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer related deaths in the United States and one of the most lethal human cancers. Chronic pancreatitis, which is characterized by inflammation of the pancreas, is a well-known risk factor for PDAC in humans. However, the precise mechanisms whereby chronic pancreatitis promotes pancreatic tumorigenesis remain elusive. Hypoxia, a condition of insufficient oxygen availability, occurs in the context of pancreatic cancer as well as chronic pancreatitis, suggesting that hypoxia is a link between chronic inflammation of the pancreas and carcinogenesis. Hypoxia inducible factor 1α (HIF-1α) is a principal mediator of hypoxic responses. HIF-1α has also been shown to tightly regulate inflammatory responses of myeloid cells. To elucidate the effects of HIF-1α on chronic inflammatory injury and regeneration of the pancreas, and define the role of HIF-1α in pancreatic cancer development, we generated mice that spontaneously develop PDAC with HIF-1α ablated. Our results indicate that HIF-1α impacts both the resolution of pancreatitis as well as the progression of pancreatic neoplasia and inflammatory cell recruitment.

Citation Format: M. Celeste Simon. A hypoxic microenvironment influences pancreatic cancer progression. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA13. doi:10.1158/1538-7445.CHTME14-IA13
Abstract IA17: Intratumoral heterogeneity in glioblastoma
Authors: Seoane Joan
Published: May 2015

Cells within tumours have diverse genomes, epigenomes, and interact differentially with their surrounding microenvironment generating intratumour heterogeneity, which has critical implications for treating cancer patients. I will present our current approach to understand the intratumour heterogeneity in glioblastoma through the analysis of patient-derived models. I will present examples of how we perform functional analysis to understand genomic alterations in the context of inter- and intra-tumoral heterogeneity taking special interest on their therapeutic implications. Linked to the concept of intratumor heterogeneity in the cellular state of differentiation, I will explain our studies related to cancer-initiating cells in glioblastoma, and I will focus on the TGF-beta pathway which has a critical role in glioblastoma.

Citation Format: Joan Seoane. Intratumoral heterogeneity in glioblastoma. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA17. doi:10.1158/1538-7445.CHTME14-IA17
Abstract IA18: A brain metastasis-promoting role for cathepsin S identified from analysis of tumor- and stroma-supplied proteolytic networks
Authors: Sevenich Lisa , Bowman Robert , Mason Steve , Quail Daniela , Rapaport Franck , Elie Benelita , Brogi Edi , Brastianos Priscilla , Hahn William , Holsinger Leslie , Massagué Joan , Leslie Christina , Joyce Johanna A.
Published: May 2015

Cancer cells in an aggressive primary tumor are adept at exploiting their local tissue microenvironment. In contrast, when metastatic cells leave these favorable surroundings, they must possess or acquire traits that will allow them to survive and colonize foreign, potentially hostile tissue environments. The obstacles that metastasizing tumor cells encounter vary from organ to organ, and are highly influenced by non-cancerous stromal cells of the tumor microenvironment. For example, the blood-brain barrier, composed of endothelial cells, astrocytes and pericytes, presents a far more formidable structure for tumor cells to penetrate, compared to the fenestrated capillaries in the bone marrow.

While the primary tumor microenvironment has emerged as an important regulator of cancer progression, it is less well understood how different tissue environments influence metastatic processes. We used a dual species-specific microarray platform to uncover tumor-stroma interactions that modulate organ tropism of brain, bone and lung metastasis in animal models of cancer. Among the differentially regulated tumor- and stroma-specific genes, we identified cathepsin S as a novel regulator of breast-to-brain metastasis. In breast cancer patients, high cathepsin S expression at the primary site correlated with decreased brain metastasis-free survival. Both macrophages and tumor cells produce cathepsin S, and only the combined depletion significantly reduced brain metastasis in experimental models in vivo. We show that cathepsin S specifically mediates blood-brain barrier transmigration via proteolytic processing of the junctional adhesion molecule (JAM)-B. Pharmacological inhibition of cathepsin S significantly reduced experimental brain metastasis, supporting its consideration as a therapeutic target for this disease.

Citation Format: Lisa Sevenich, Robert Bowman, Steve Mason, Daniela Quail, Franck Rapaport, Benelita Elie, Edi Brogi, Priscilla Brastianos, William Hahn, Leslie Holsinger, Joan Massagué, Christina Leslie, Johanna A. Joyce. A brain metastasis-promoting role for cathepsin S identified from analysis of tumor- and stroma-supplied proteolytic networks. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA18. doi:10.1158/1538-7445.CHTME14-IA18
Abstract IA19: Multiplexing TGFβ in the tumor microenvironment
Authors: Barcellos-Hoff Mary Helen
Published: May 2015

The dynamics of TGFβ biology is context dependent. TGFβ is controlled at many levels with a major mechanism in its production as a latent complex from which TGFβ is released extracellularly. TGFβ production and activity is greatly increased in many cancer cells. Tumor microenvironment can also be a significant TGFβ source, particularly bone marrow derived cells (BMDC). TGFβ regulates malignant behaviors and cell phenotype of tumor microenvironment constituents locally and the hematopoietic and immune systems at a distance. We investigated the contribution of TGFβ to the effects of radiotherapy in breast, brain and lung cancer murine models. Our studies show that radiation induces rapid TGFβ activation that can persist for days. Radiation induced TGFβ promotes rapid and effective DNA damage response, mediates tumor microenvironment composition, regulates BMDC recruitment and phenotype, and augments immune evasion. Inhibition of TGFβ during radiotherapy provides significant therapeutic benefit by molecular and microenvironmental mechanisms. TGFβ inhibition during radiotherapy impedes DNA damage recognition, which promotes tumor cell death and thus, tumor growth control. Continued TGFβ inhibition prevents vascular remodeling necessary for tumor regrowth, and blocks BMDC recruitment, which limits an exogenous TGFβ source. Multiplexing these actions with those on tumor immunity suggest potent therapeutic potential of TGFβ inhibition during radiotherapy to eliminate tumor cells and eradicate tumor promoting microenvironments.

Citation Format: Mary Helen Barcellos-Hoff. Multiplexing TGFβ in the tumor microenvironment. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr IA19. doi:10.1158/1538-7445.CHTME14-IA19
Abstract PR01: Rebastinib, a selective TIE2 kinase inhibitor, decreases TIE2-expressing macrophages, reduces metastasis, and increases survival in murine cancer models
Authors: Flynn Daniel L. , Kaufman Michael D. , Leary Cynthia B. , Hood Molly M. , Lu Wei-Ping , Turner Benjamin A. , Wise Scott C. , Rudoltz Marc S. , Smith Bryan D.
Published: May 2015

In the tumor microenvironment, TIE2 expression on tissue macrophages, bone marrow derived TIE2-expressing monocytes (TEMs), osteoclasts, and vascular endothelial cells promotes tumor invasiveness, dissemination, and metastasis. Additionally, a subset of TIE2-expressing macrophages, located within specialized vascular structures known as tumor microenvironment for metastases (TMEMs), are linked to intravasation of cancer cells into circulation and dissemination to metastatic sites. Rebastinib is a picomolar inhibitor of TIE2 kinase, and exhibits an extraordinarily long off-rate from TIE2, measured to be over 24 hours in a cell-based assay. Herein, we examine the efficacy of rebastinib in the polyoma middle-T antigen (PyMT) syngeneic mouse breast cancer model. In this model, PyMT breast cancer cells are implanted in the mammary fat pad, and primary tumor growth leads to lung metastasis, which is known to be modulated by TEMs and TMEM vascular structures. We examined multiple dosing schedules of rebastinib in combination with anti-tubulin agents (ATAs). Rebastinib treatment in this model significantly ablated TEMs in the primary tumor stroma and caused a significant decrease in lung metastases. Furthermore, the combination of rebastinib with ATAs, even with once or twice weekly oral dosing of rebastinib, led to a significant further decrease in lung metastases compared to single-agent treatment with ATAs. Rebastinib also enhanced the activity of ATAs in reducing primary tumor growth and regrowth of tumor post-resection. TIE2 inhibition with targeted therapy represents a novel treatment approach for metastatic breast cancer and other cancers that rely on TEMs and TMEMs for growth and metastasis. As such, rebastinib has been selected for further clinical development in solid tumors with a Phase 1b trial being planned for 2014.

This abstract is also presented as Poster A5.

Citation Format: Daniel L. Flynn, Michael D. Kaufman, Cynthia B. Leary, Molly M. Hood, Wei-Ping Lu, Benjamin A. Turner, Scott C. Wise, Marc S. Rudoltz, Bryan D. Smith. Rebastinib, a selective TIE2 kinase inhibitor, decreases TIE2-expressing macrophages, reduces metastasis, and increases survival in murine cancer models. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR01. doi:10.1158/1538-7445.CHTME14-PR01
Abstract PR11: Hematopoietic system aging has profound effects on the breast tumor microenvironment and cancer progression
Authors: Marsh Timothy , Wong Irene , Barakat Amey , Qin Yuanbo , McAllister Sandra S.
Published: May 2015

The majority of breast neoplasms are diagnosed in patients who are between the ages of 65 and 80. Although tumor growth is generally less aggressive and metastasis is less prevalent in older patients than in younger patients, elderly patients suffer the highest mortality and morbidity associated with breast cancer and breast cancer treatment. The reasons for age-dependent differences in incidence and aggressiveness of breast cancer are not understood. Treatment of breast cancer patients therefore presents age-specific challenges.

We recently established mouse and human xenograft breast tumor models that mimic the age dependent disease progression that is observed in breast cancer patients, whereby tumor cells implanted into aged mice had lower incidence and slower growth kinetics than when implanted into young mice. Moreover, alpha-smooth muscle actin-positive myofibroblasts within the tumor microenvironment were significantly less prevalent in the tumors from aged mice than in size-matched tumors from young mice.

We discovered that bone marrow derived cells from aged mice were significantly less effective in supporting breast cancer progression than the counterpart cells from young mice. Strikingly, bone marrow derived cells from young mice rescued tumor growth and stromal desmoplasia in aged mice. We are elucidating some of the molecular and phenotypic differences between young and aged tumor-promoting bone marrow cells. For example, we found that bone marrow cells from aged mice express lower levels of the cytokine, granulin, which is known to activate normal mammary fibroblasts in young mice.

Our findings indicate that the age of the host hematopoietic system is a powerful determinant of breast tumor progression. Defining functional and molecular differences between tumor supportive hematopoietic cells in young and aged hosts should lay a foundation for further work in this relatively uncharted area of cancer research. Understanding tumor support mechanisms that exist in young and aged hosts should suggest new ideas for preclinical development of age-stratified breast cancer therapies.

Citation Format: Timothy Marsh, Irene Wong, Amey Barakat, Yuanbo Qin, Sandra S. McAllister. Hematopoietic system aging has profound effects on the breast tumor microenvironment and cancer progression. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR11. doi:10.1158/1538-7445.CHTME14-PR11
Abstract A18: Uncovering molecular subgroups and a novel cancer driver, ACVR1, in diffuse intrinsic pontine gliomas
Authors: Buczkowicz Pawel , Hoeman Christine , Rakopoulos Patricia , Pajovic Sanja , Morrison Andrew , Bouffet Eric , Bartels Ute , Becher Oren , Hawkins Cynthia
Published: May 2015

Diffuse intrinsic pontine glioma (DIPG) is a devastating paediatric brain tumor with no effective therapy and near 100% fatality. The failure of most therapies can be attributed to the delicate location of these tumors and choosing therapies based on assumptions that DIPGs are molecularly similar to adult disease. Recent studies have unravelled the unique genetic make-up of this brain cancer with nearly 80% harbouring a K27M-H3.3 or K27M-H3.1 mutation. However, DIPGs are still thought of as one disease with limited understanding of the genetic drivers of these tumors. Here we apply methylation profiling, whole genome sequencing, expression profiling, and copy number analysis to discover that DIPGs are three molecularly distinct subgroups (H3-K27M, Silent, and MYCN) and uncover a mutations in a novel driver, ACVR1 in 20% of DIPGs. Mutations in ACVR1 were constitutively activating, leading to SMAD phosphorylation and increased expression of downstream activin signalling targets ID1 and ID2. The MYCN subgroup is not associated with histone mutations and is instead characterized by hypermethylation and chromothripsis of chromosome 2p with high-level amplifications of MYCN, ID2, and KIDINS220. The Silent subgroup affects younger children, has genomes with minimal genomic instability and fewer mutations, over-expresses WNT pathway genes, as well as genes with known cancer association such as MDM2, MSMP and ADAM33. The H3-K27M subgroup is highly K27M-H3 mutated and associated with additional hits including activating mutations in ACVR1, frequent RB1 and TP53 deletions, PVT-1/MYC or PDGFRA gains/amplifications, genomic instability and alternative lengthening of telomeres. Our results show that this seemingly homogeneous entity in fact comprises three distinct subgroups with different demographic and molecular features. This complexity needs to be considered when designing new therapeutic approaches in order to improve outcome for these children.

Citation Format: Pawel Buczkowicz, Christine Hoeman, Patricia Rakopoulos, Sanja Pajovic, Andrew Morrison, Eric Bouffet, Ute Bartels, Oren Becher, Cynthia Hawkins. Uncovering molecular subgroups and a novel cancer driver, ACVR1, in diffuse intrinsic pontine gliomas. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A18.
Abstract A22: Somatic mutations in DROSHA and DICER1 impair microRNA biogenesis in Wilms tumors
Authors: Rakheja Dinesh , Chen Kenneth S. , Liu Yangjian , Shukla Abhay A. , Hildebrand Sara , Schmid Vanessa , Sun Xiaoyong , Feng Xin , Chang Tsung-Cheng , Khokhar Shama , Karandikar Nitin J. , Malter James S. , Mendell Joshua T. , Amatruda James F.
Published: May 2015

Wilms tumor is the most common pediatric kidney cancer and the fourth most common childhood cancer overall. It is treated with a combination of surgery, chemotherapy, and radiation, and while most children are cured, survival remains poor in those with advanced-stage disease. Known driver mutations (in WT1, WTX, and CTNNB1) account for only one-third of Wilms tumor cases. To better define the genomic landscape of Wilms tumor, we performed whole-exome sequencing of 44 Wilms tumors. We also sequenced matched germline DNA by whole-exome sequencing (15 cases) or targeted Sanger sequencing (29 cases) to identify somatic mutations. Through this approach, we identified recurrent somatic mutations in MYCN, DROSHA, and DICER1, which were mutually exclusive with known Wilms tumor mutations in WT1 and CTNNB1. The ribonucleases DROSHA and DICER1 perform two key steps in the biogenesis of microRNAs (miRNAs), which are ∼22-nt non-coding RNAs that regulate the stability and translation of target mRNAs. DROSHA and DICER1 mutations occurred at or near conserved metal-binding residues in their ribonuclease (RNase) IIIB domains. In vitro processing assays modeling these mutations showed that they partially or completely disrupted the ribonuclease activity of DROSHA and DICER1. In addition, next-generation sequencing of small RNAs in these tumors revealed that the DICER1 mutations preferentially impaired processing of miRNAs derived from the 5′ arm of pre-miRNA hairpins, including the let-7 tumor suppressor miRNA family. Processing of 5′-derived miRNAs is specifically dependent on DICER1 RNase IIIB activity. Although DROSHA-mutant tumors did not exhibit skewed expression of 5′ vs. 3′-derived miRNAs, expression of let-7 and other putative tumor suppressor miRNAs was reduced in these tumors as well. While germline and somatic mutations in DICER1 have been reported in some cancers, this is the first report of recurrent DROSHA mutations in any human tumor type. Moreover, these results suggest that impairment of miRNA processing by somatic mutation of DROSHA and DICER1 defines a novel subclass of Wilms tumor.

Citation Format: Dinesh Rakheja, Kenneth S. Chen, Yangjian Liu, Abhay A. Shukla, Sara Hildebrand, Vanessa Schmid, Xiaoyong Sun, Xin Feng, Tsung-Cheng Chang, Shama Khokhar, Nitin J. Karandikar, James S. Malter, Joshua T. Mendell, James F. Amatruda. Somatic mutations in DROSHA and DICER1 impair microRNA biogenesis in Wilms tumors. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A22.
Abstract A31: The long noncoding RNA lnc277 mediates a repressive gene signature in Ewing's sarcoma
Authors: Marques Michelle , Simpson David , Chen Ron , Vaka Dedeepya , Breese Marcus , Brunner Allayne , West Rob , Sweet-Cordero Alejandro
Published: May 2015

Ewing's sarcoma is a highly aggressive tumor characterized by a translocation between members of the FET family of RNA binding proteins and one of several ETS transcription factors, with the most common translocation being EWS-FLI1. Like many oncogenic translocations, EWS-FLI1 leads to changes in gene expression through mechanisms that are not completely understood. We performed RNA sequencing analysis on human mesenchymal progenitor cells (MPCs) expressing EWS-FLI1, which are thought to be the cell of origin of Ewing's sarcoma. This analysis identified lnc277 as a previously uncharacterized long non-coding RNA upregulated by EWS-FLI1 in MPCs. Expression of lnc277 in Ewing's sarcoma cell lines requires EWS-FLI1. In addition, inhibiting the expression of lnc277 diminished the ability of Ewing's sarcoma cell lines to proliferate and form soft agar colonies. Using RNA sequencing and shRNA knockdown, we defined the transcriptional changes induced by EWS-FLI1 and lnc277. This analysis revealed that both EWS-FLI1 and lnc277 repress far more genes that they induce and that a large fraction of EWS-FLI1 repressed targets are also modulated by lnc277. Thus, lnc277 is an oncogenic long non-coding RNA downstream of EWS-FLI1 that facilitates the formation of Ewing's sarcoma via the repression of target genes.

Citation Format: Michelle Marques, David Simpson, Ron Chen, Dedeepya Vaka, Marcus Breese, Allayne Brunner, Rob West, Alejandro Sweet-Cordero. The long noncoding RNA lnc277 mediates a repressive gene signature in Ewing's sarcoma. [abstract]. In: Proceedings of the AACR Special Conference on Pediatric Cancer at the Crossroads: Translating Discovery into Improved Outcomes; Nov 3-6, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;74(20 Suppl):Abstract nr A31.