Human Breast Cancer Subtypes Research Articles

A novel single domain antibody (sdAb) SBT-100 targeting intracellular STAT3 to inhibit major subtypes of human breast cancer.

e14000Background: The primary role of ER+/PR+ and HER2+ in breast cancers is well known. It has been well established that antiestrogens and Herceptin are very efficacious for ER+/PR+ and HER2+ can...

Multifunctional roles of PKCδ: Opportunities for targeted therapy in human disease.

The serine-threonine protein kinase, protein kinase C-δ (PKCδ), is emerging as a bi-functional regulator of cell death and proliferation. Studies in PKCδ-/- mice have confirmed a pro-apoptotic role for this kinase in response to DNA damage and a tumor promoter role in some oncogenic contexts. In non-transformed cells, inhibition of PKCδ suppresses the release of cytochrome c and caspase activation, indicating a function upstream of apoptotic pathways. Data from PKCδ-/- mice demonstrate a role for PKCδ in the execution of DNA damage-induced and physiologic apoptosis. This has led to the important finding that inhibitors of PKCδ can be used therapeutically to reduce irradiation and chemotherapy-induced toxicity. By contrast, PKCδ is a tumor promoter in mouse models of mammary gland and lung cancer, and increased PKCδ expression is a negative prognostic indicator in Her2+ and other subtypes of human breast cancer. Understanding how these distinct functions of PKCδ are regulated is critical for the design of therapeutics to target this pathway. This review will discuss what is currently known about biological roles of PKCδ and prospects for targeting PKCδ in human disease.

Production and characterization of monoclonal antibodies specific for canine CD138 (syndecan-1) for nuclear medicine preclinical trials on spontaneous tumours.

We isolated 11 antibodies specific for canine CD138 (cCD138) to validate the interest of CD138 antigen targeting in dogs with spontaneous mammary carcinoma. The affinity of the monoclonal antibodies in the nanomolar range is suitable for immunohistochemistry and nuclear medicine applications. Four distinct epitopes were recognized on cCD138 by this panel of antibodies. CD138 expression in canine healthy tissues is comparable to that reported in humans. CD138 is frequently expressed in canine mammary carcinomas corresponding to the human triple negative breast cancer subtype, with cytoplasmic and membranous expression. In canine diffuse large B-cell lymphoma, CD138 expression is associated with the 'non-germinal center' phenotype corresponding to the most aggressive subtype in humans. This homology of CD138 expression between dogs and humans confirms the relevance of tumour-bearing dogs as spontaneous models for nuclear medicine applications, especially for the evaluation of new tumour targeting strategies for diagnosis by phenotypic imaging and radio-immunotherapy.

Molecular based subtyping of feline mammary carcinomas and clinicopathological characterization

Molecular classification of feline mammary carcinomas (FMC) from which specific behavioral patterns may be estimated has potential applications in veterinary clinical practice and in comparative oncology. In this perspective, the main goal of this study was to characterize both the clinical and the pathological features of the different molecular phenotypes found in a population of FMC (n = 102), using the broadly accepted IHC-based classification established by St. Gallen International Expert Consensus panel.The luminal B/HER2-negative subtype was the most common (29.4%, 30/102) followed by luminal B/HER2-positive subtype (19.6%, 20/102), triple negative basal-like (16.7%, 17/102), luminal A (14.7%, 15/102), triple negative normal-like (12.7%, 13/102) and finally, HER2-positive subtype (6.9%, 7/102). Luminal A subtype was significantly associated with smaller tumors (p = 0.024) and with well differentiated ones (p < 0.001), contrasting with the triple negative basal-like subtype, that was associated with larger and poorly differentiated tumors (p < 0.001), and with the presence of necrotic areas in the tumoral lesion (p = 0.003). In the survival analysis, cats with Luminal A subtype presented the highest survival time (mean OS = 943.6 days) and animals with triple negative basal-like subtype exhibited the lowest survival time (OS mean = 368.9 days). Moreover, two thirds (64%, 32/50) of the queens with multiple primary tumors showed different molecular subtypes in each carcinoma, revealing that all independent lesions should be analyzed in order to improve the clinical management of animals.Finally, the similarities between the subtypes of feline mammary tumors and human breast cancer, reveal that feline can be a valuable model for comparative studies.

Abstract A43: Long noncoding RNAs as targets of mammary tumor cell proliferation and migration

Abstract Objective: Recent genome-wide studies revealed that as much as 80% of the human genome can be transcribed whereas only 2% of this RNA is translated into proteins. Non-coding transcripts can be subdivided into several groups, with long non-coding RNAs (lncRNAs) representing the largest and most diverse class. With breast cancer being the most frequent malignancy in women worldwide, we set out to investigate the potential of lncRNAs as novel therapeutic targets. Methods: We focused on the luminal B and the HER2/neu-positive subtypes of breast cancer, as both are associated with high prevalence and bad prognosis. By performing RNA-Seq on tumor sections and mammary organoids from MMTV-PyMT and MMTV-Neu-NDL mice, modeling the luminal B and HER2/neu-amplified subtypes of human breast cancer respectively, we generated a comprehensive catalog of differentially expressed lncRNAs. We functionally validated the role of a subset of these lncRNAs by antisense oligonucleotide (ASO) mediated knockdown in primary mammary tumor cells and 3D ex vivo organoids. Results: We identified several hundred potentially oncogenic lncRNAs that were over-expressed in a subtype-specific manner as well as numerous lncRNAs up-regulated in both MMTV-PyMT and MMTV-Neu-NDL tumors. To narrow down the candidate list of lncRNAs with the highest therapeutic potential, we sorted the data computationally and defined a subset of previously uncharacterized lncRNAs as Mammary Tumor Associated RNAs (MaTARs). Upon independent knockdown of several MaTARs, we observed significantly reduced cell proliferation, invasion and/or collective cell migration in a cancer-specific context. Conclusion: MaTARs are likely important drivers of mammary tumor progression and/or metastasis and represent promising new therapeutic targets. Future studies will focus on the molecular characterization of these lncRNAs and elucidation of their potential role(s) in mammary tumor progression and metastasis. Citation Format: Sarah D. Diermeier, Kung-Chi Chang, Susan M. Freier, Frank Rigo, C. Frank Bennett, David L. Spector. Long noncoding RNAs as targets of mammary tumor cell proliferation and migration. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr A43.

Identification of novel pathways linking epithelial-to-mesenchymal transition with resistance to HER2-targeted therapy.

Resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapies in the treatment of HER2-positive breast cancer is a major clinical problem. To identify pathways linked to resistance, we generated HER2-positive breast cancer cell lines which are resistant to either lapatinib or AZD8931, two pan-HER family kinase inhibitors. Resistance was HER2 independent and was associated with epithelial-to-mesenchymal transition (EMT), resulting in increased proliferation and migration of the resistant cells. Using a global proteomics approach, we identified a novel set of EMT-associated proteins linked to HER2-independent resistance. We demonstrate that a subset of these EMT-associated genes is predictive of prognosis within the ERBB2 subtype of human breast cancers. Furthermore, targeting the EMT-associated kinases Src and Axl potently inhibited proliferation of the resistant cells, and inhibitors to these kinases may provide additional options for the treatment of HER2-independent resistance in tumors.

Abstract IA20: Genomics of a STAT1 knockout mouse model of human ER+ breast cancer

Abstract Estrogen receptor alpha positive luminal breast cancers are the most frequent subtype of breast cancer. Previous work has established that Stat1-/- mouse mammary tumor model recapitulates signaling, expression and phenotypic alterations observed in this subtype of human breast cancers. To identify transforming events that contribute to tumorigenesis, we performed whole genome sequencing of 22 Stat1-/- primary mammary tumors and cell lines. We discovered a novel hotspot of somatic mutations in 100% of tumors that resulted in a truncated form of the prolactin receptor (Prlr). Targeted sequence analysis identified similar mutations in 77.8% of ductal carcinoma in situ. Co-expression of truncated and full-length Prlr in normal cells led to activation of oncogenic Stat3 and Stat5 as well as cellular transformation. In conclusion, truncating mutations of Prlr drive tumor development in a model of human ERa+ breast cancer and should be considered as novel antitumor targets. Citation Format: Elaine Mardis, Obi L. Griffith, Ruby Chan Szeman, Malachi Griffith, Kilannin Krysiak, Zachary Skidmore, Jasreet Hundal, Julie A. Allen, Arthur Cora, Alexander P. Miceli, Heather Schmidt, Lee Trani, Krishna-Latha Kanchi, Christopher A. Miller, David E. Larson, Robert S. Fulton, Richard K. Wilson, Robert D. Schreiber. Genomics of a STAT1 knockout mouse model of human ER+ breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr IA20.

Cell Fate Decisions During Breast Cancer Development.

During the formation of breast cancer, many genes become altered as cells evolve progressively from normal to a pre-malignant to a malignant state of growth. How mutations in genes lead to specific subtypes of human breast cancer is only partially understood. Here we review how initial genetic or epigenetic alterations within mammary epithelial cells (MECs) can alter cell fate decisions and put pre-malignant cells on a path towards cancer development with specific phenotypes. Understanding the early stages of breast cancer initiation and progression and how normal developmental processes are hijacked during transformation has significant implications for improving early detection and prevention of breast cancer. In addition, insights gleaned from this understanding may also be important for developing subtype-specific treatment options.

Therapeutic targeting of casein kinase 1δ in breast cancer.

Identification of specific drivers of human cancer is required to instruct the development of targeted therapeutics. We demonstrate that CSNK1D is amplified and/or overexpressed in human breast tumors and that casein kinase 1δ (CK1δ) is a vulnerability of human breast cancer subtypes overexpressing this kinase. Specifically, selective knockdown of CK1δ, or treatment with a highly selective and potent CK1δ inhibitor, triggers apoptosis of CK1δ-expressing breast tumor cells ex vivo, tumor regression in orthotopic models of triple-negative breast cancer, including patient-derived xenografts, and tumor growth inhibition in human epidermal growth factor receptor 2-positive (HER2(+)) breast cancer models. We also show that Wnt/β-catenin signaling is a hallmark of human tumors overexpressing CK1δ, that disabling CK1δ blocks nuclear accumulation of β-catenin and T cell factor transcriptional activity, and that constitutively active β-catenin overrides the effects of inhibition or silencing of CK1δ. Thus, CK1δ inhibition represents a promising strategy for targeted treatment in human breast cancer with Wnt/β-catenin involvement.

Conserved E2F mediated metastasis in mouse models of breast cancer and HER2 positive patients.

To improve breast cancer patient outcome work must be done to understand and block tumor metastasis. This study leverages bioinformatics techniques and traditional genetic screens to create a novel method of discovering potential contributors of tumor progression with a focus on tumor metastasis. A database of 1172 of expression data from a variety of mouse models of breast cancer was assembled and queried using previously defined oncogenic activity signatures. This analysis revealed high activity of the E2F family of transcription factors in the MMTV-Neu mouse model. A genetic cross of MMTV-Neu mice into an E2F1 null, E2F2 null, or E2F3 heterozygous background revealed significant changes in tumor progression specifically reductions in tumor latency and metastasis with E2F1 or E2F2 loss. These findings were found to be conserved in human HER2 positive patients. Patients with high E2F1 activity were shown to have worse outcomes such as relapse free survival and distant metastasis free survival. This study shows conserved mechanisms of tumor progression in human breast cancer subtypes and analogous mouse models and underlies the importance of increased research into the characterization of and comparisons between mouse and human tumors to identify which mouse models resemble each subtype of human breast cancer.

Multipotent luminal mammary cancer stem cells model tumor heterogeneity.

IntroductionThe diversity of human breast cancer subtypes has led to the hypothesis that breast cancer is actually a number of different diseases arising from cells at various stages of differentiation. The elusive nature of the cell(s) of origin thus hampers approaches to eradicate the disease.MethodsClonal cell lines were isolated from primary transgenic polyomavirus middle T (PyVmT) luminal tumors. Mammary cancer stem cell (MaCSC) properties were examined by immunofluorescence, flow cytometry, differentiation assays and in vivo tumorigenesis.ResultsClonal cell lines isolated from primary PyVmT mouse mammary luminal tumors can differentiate into luminal, myoepithelial, alveolar and adipocyte lineages. Upon orthotopic injection, progeny of a single cell follow a pattern of progression from ductal carcinoma in situ, to adenoma, adenocarcinoma and epithelial metastasis that recapitulates the transgenic model. Tumors can evolve in vivo from hormone receptor-positive to hormone receptor-negative Her2-positive, or triple negative CD44hi basal-like and claudin-low tumors. Contrary to the current paradigm, we have defined a model in which multiple tumor subtypes can originate from a single multipotent cancer stem cell that undergoes genetic and/or epigenetic evolution during tumor progression. As in human tumors, the more aggressive tumor subtypes express nuclear p53. Tumor cell lines can also be derived from these more advanced tumor subtypes.ConclusionsSince the majority of human tumors are of the luminal subtype, understanding the cell of origin of these tumors and how they relate to other tumor subtypes will impact cancer therapy. Analysis of clonal cell lines derived from different tumor subtypes suggests a developmental hierarchy of MaCSCs, which may provide insights into the progression of human breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0615-y) contains supplementary material, which is available to authorized users.

Tumor suppressor functions of BNIP3 and mitophagy

There is a growing realization that tumor cells rely on healthy mitochondria to promote their growth under changing microenvironmental stresses and do so by dynamically modulating both their mitochondrial mass and state of mitochondrial fusion. Our recent work adds to this appreciation by showing that the mitophagy receptor BNIP3 functions as a tumor suppressor in mammary tumorigenesis and also as a prognostic indicator of progression to metastasis in certain sub-types of human breast cancer.

Abstract A03: Integrative analyses reveal distinct metabolic dysregulation in MYC-driven, basal breast cancer

Abstract Dysregulated metabolism is a hallmark of all human cancers. The observation that tumors display unique changes in metabolism led to the hypothesis that tumors may be dependent upon an altered metabolic state. c-MYC (MYC) is a proto-oncogene and transcription factor activated in many cancers that regulates multiple metabolic pathways. Our lab and others have shown that MYC is activated in a large proportion of basal-like breast cancer, the most aggressive subtype of human breast cancer. However, the role of MYC in basal breast cancer metabolism is largely unknown. No efficacious MYC inhibitor is available for clinical use, however, an alternative treatment strategy is to target cellular pathways required in the context of MYC activation. We hypothesize that basal-like breast cancer harbors distinct, MYC-driven metabolic dysregulation, and that this dysregulation can be targeted therapeutically to induce MYC-dependent synthetic lethality. Utilizing in vitro and in vivo models of MYC-driven and basal breast cancer, including patient-derived cell lines and patient-derived xenograft mouse tumor models, we have performed metabolomic and transcriptomic analyses. We investigate MYC-dependent metabolic dysregulation via integrated analyses of these datasets, and find distinct changes that could reveal essential metabolic pathways for MYC-driven, basal tumorigenesis. Citation Format: Roman Camarda, Sanjeev Balakrishnan, Alicia Y. Zhou, Brittany Anderton, Henok Eyob, Rebecca Kohnz, Daniel K. Nomura, Andrei Goga. Integrative analyses reveal distinct metabolic dysregulation in MYC-driven, basal breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Myc: From Biology to Therapy; Jan 7-10, 2015; La Jolla, CA. Philadelphia (PA): AACR; Mol Cancer Res 2015;13(10 Suppl):Abstract nr A03.

Abstract A76: MicroRNA mediated negative regulation of caveolin 1 as a biological mechanism driving breast cancer disparities

Abstract Although rates of breast cancer incidence are lower in African American (AA) women, the mortality rates are significantly higher compared to non-Hispanic white (WNH) women. This shocking statistic illustrates the racial disparities in breast cancer, as AA women have a poorer prognosis compared to WNH women. While this may be due in part to socioeconomic and standard of care issues, increasing evidence suggests that the racial disparity exists independent of these issues and could also be attributed to poorly understood inherent genetic and molecular characteristics within racial specific tumors. Caveolin-1 (Cav1) is a scaffolding protein with a tumor suppressor role. Loss of Cav1 in the tumor stromal compartment has emerged as a novel biomarker for predicting poor clinical outcome in all of the most common subtypes of human breast cancer, including the more lethal triple negative subtype which is significantly more common in AA women. While the loss of stromal Cav1 is becoming well established as a marker of poor outcome in breast cancer, the mechanism of this loss is still unknown. We propose that differences in microRNA mediated stromal Cav1 loss between AA and WNH women is driving the racial disparity in breast cancer. MicroRNAs (miRNAs) are short, endogenous, non-coding RNA that function as negative regulators of gene expression. miR-510 is an oncogenic miRNA that has been shown to be elevated in breast tumors. Cav1 is a predicted target of miR-510 and therefore miR-510 mediated negative regulation may be a novel mechanism of Cav1 loss in the tumor stroma. Our research shows that Cav1 is directly targeted by miR-510 by luciferase reporter assay and that overexpression of miR-510 leads to downregulation of Cav1 protein expression, specifically in the stromal compartment. Tumor epithelium and stroma co-culture assays demonstrate that epithelial derived miR-510 may be transferred to neighboring stromal cells and negatively regulate Cav1 expression in the stromal compartment. This may be racially significant as our supporting studies also show that miR-510 levels are elevated and Cav1 levels are reduced in AA breast cancer patients compared to their white counterparts. Our results suggest that the difference in miR-510 mediated regulation of stromal Cav1 is driving racial disparity in breast cancer. Citation Format: Qi Jin Guo, Brooke King, Bobbie Blake, Amanda C. LaRue, Judith D. Salley, Marvella E. Ford, Ashley Evans-Knowell, Victoria J. Findlay. MicroRNA mediated negative regulation of caveolin 1 as a biological mechanism driving breast cancer disparities. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr A76.

Overview of Genetically Engineered Mouse Models of Breast Cancer Used in Translational Biology and Drug Development.

Breast cancer is a heterogeneous condition with no single standard of treatment and no definitive method for determining whether a tumor will respond to therapy. The development of murine models that faithfully mimic specific human breast cancer subtypes is critical for the development of patient-specific treatments. While the artificial nature of traditional in vivo xenograft models used to characterize novel anticancer treatments has limited clinical predictive value, the development of genetically engineered mouse models (GEMMs) makes it possible to study the therapeutic responses in an intact microenvironment. GEMMs have proven to be an experimentally tractable platform for evaluating the efficacy of novel therapeutic combinations and for defining the mechanisms of acquired resistance. Described in this overview are several of the more popular breast cancer GEMMs, including details on their value in elucidating the molecular mechanisms of this disorder.

Abstract 1352: Identifying pre-diagnostic breast cancer antigens in transgenic mouse mammary tumor models for preventative vaccine development

Abstract Preventative vaccine therapy may benefit women at high risk for breast cancer but currently it is impossible to identify women who will develop breast cancer prior to tumor development to identify initiating cancer antigens. Immunocompetent transgenic mouse mammary tumor models that are genetically similar to human breast cancer subtypes may identify pre-invasive antigens because mice can be followed longitudinally. Comparing tumor growth characteristics in two mouse models (TgMMTV-neu is genetically similar to luminal B breast cancer and C3(1)tag is genetically similar to triple negative breast cancer) demonstrated that, similar to triple negative breast cancer, C3(1)Tag mice develop tumors earlier and tumors grow more rapidly than TgMMTV-neu tumors. Furthermore, C3(1)Tag tumors have increased CD8+/CD4+ ratio (p&amp;lt;0.05) similar to human triple negative tumors. Using these two mouse models, we identified putative pre-invasive breast cancer antigens present prior to tumor development by serologic analysis of recombinant cDNA expression libraries and serological analysis of chip-arrayed proteins. We identified 65 pre-invasive antigens that were present in mice that would develop cancer but not parental control mice. The goal of this study was to identify which of the 65 antigens were required for human breast cancer survival with the goal to develop a preventative multi-antigen polyepitope breast cancer vaccine. We chose the pre-invasive antigens necessary for human breast cancer tumor cell survival using a high throughput siRNA screen evaluating for increased apoptosis and decreased cell survival in either HER2 positive or triple negative human breast cancer cell lines with decreased expression of the target protein. Five of the antigens were essential for human breast cancer cell survival: VPS35, SERBP1, ARPC2, PDIA6, and KRT8. All of these genes have roles in human cancer progression, and KRT8, SERBP1, and PDIA6 have identified roles in breast cancer pathogenesis. After designing human MHC class II peptides for each of these targets that cover at least 25% of the protein, we evaluated implanted tumor inhibition in the mouse models. Vaccination VPS35 peptides inhibited tumor growth by 47% (p&amp;lt;0.0001), vaccination with ARPC2 peptides inhibited tumor growth by 54% (p&amp;lt;0.0001), and vaccination with SERBP1 peptides inhibited tumor growth by 61% (p&amp;lt;0.0001) in the TgMMTV-neu mice. In C3(1)Tag mice, vaccination with VPS35 peptides inhibited tumor growth by 39% (p&amp;lt;0.0001) and vaccination with SERBP1 peptides inhibited tumor growth by 59% (p&amp;lt;0.0001) but vaccination with ARPC2 peptides did not inhibit tumor growth. These studies have demonstrated that mouse models can be used to identify pre-invasive breast cancer antigens. Further studies will evaluate the use of vaccines containing epitopes from several of the antigens to prevent spontaneous tumors in these mouse models. Citation Format: Sasha E. Stanton, Ekram Gadd, Lauren Rastetter, James Annis, Jianning Mao, John Ladd, Samir Hanash, Mary L. Disis. Identifying pre-diagnostic breast cancer antigens in transgenic mouse mammary tumor models for preventative vaccine development. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1352. doi:10.1158/1538-7445.AM2015-1352

Abstract 4161: Differential expression of VEGFR2 Protein in HER2 positive primary human breast cancer: Potential relevance to newer anti-angiogenic therapies

Abstract Previously, we demonstrated immunohistochemical expression of VEGFR2 protein and vascular phenotypes in human breast carcinomas (Holzer, Nasir et al AACR 2014). Here, we carried out a large-scale immunopathologic analysis of tumor vascular density and differential expression of VEGFR2 protein in various subsets of primary human breast carcinomas from 186 females (Mean age: 59 years; range 33-88 years). Sections from a primary breast cancer tissue microarray (Yale University), were stained for a sensitive tumor vascular marker (CD34) and for VEGFR2 protein using a novel VEGFR2 IHC assay developed and standardized in our laboratory (Holzer, Nasir et al PLOS One 2013). Discrete VEGFR2+ and CD34+ tumor vessels were counted in each analyzable TMA core by an experienced breast pathologist, excluding any suboptimal/inadequate cores or any areas of tumor necrosis. Histologic subtypes of primary breast carcinomas included invasive ductal, lobular, mixed ductal-lobular and colloid (N = 139, 22, 18, 7) respectively. Based on hormone receptor (HR) and Her2 status, cases were grouped into HR+, Her2+ and triple-negative subsets. Pathologic assessments of vascular density (CD34 counts) and imunohistochemical expression of VEGFR2 protein were made only in the viable invasive carcinoma tissue. The observed CD34+ and VEGFR2+ tumor vascular counts in individual cases were heterogeneous, ranging from high vascular density and high VEGFR2 expression to minimal vascular density and/or minimal or no VEGFR2 expression. Among all histologies, mean CD34+ and VEGFR2+ tumor vascular counts were 11 and 3.4 per tumor TMA core respectively. Eighty-nine of 186 (48%) cases had &amp;gt;10 CD34+ tumor vessels, while 97/186 (52%) had fewer CD34+ vessels in each TMA core. Of 169 analyzable cores in the VEGFR2 stained TMA, 90 (53%) showed 1 to 5 VEGFR2+ tumor vessels/TMA core, while 42/169 (25%) cores had no VEGFR2+ tumor vessels. Thirteen of 169 (8%) cases also showed tumor cell (cytoplasmic and/or membrane) expression of VEGFR2 protein. Triple-negative breast cancers (TNBCs) appeared to be less vascular (Mean VD = 9.8, range 0-34) than other breast cancer subtypes. Overall, VEGFR2+ tumor vessel counts were significantly higher in Her2+ as compared to HR+ (p = 0.03) and TNBC (p = 0.01) tissues. Compared to Her2- cases, Her2+ breast cancers had higher VEGFR2+ tumor vessel counts (p = 0.006). These data provide insights about tumor vascular density and vascular VEGFR2 expression in primary human breast cancer subtypes, especially Her2 positive breast cancer, and offer a pathobiologic hypothesis for the patterns of clinical response of breast cancer patients to newer anti-angiogenic therapies. Citation Format: Aejaz Nasir, Timothy R. Holzer, Michael Man, Laura E. Benjamin, Allen S. Melemed, Andrerw E. Schade. Differential expression of VEGFR2 Protein in HER2 positive primary human breast cancer: Potential relevance to newer anti-angiogenic therapies. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4161. doi:10.1158/1538-7445.AM2015-4161

Effect of cellular senescence on the growth of HER2-positive breast cancers.

Oncogene-induced senescence (OIS) is a tumor suppressor mechanism. However, senescent cells remain viable and display a distinct secretome (also known as senescence-associated secretory phenotype [SASP] or senescence messaging secretome, [SMS]) that, paradoxically, includes protumorigenic factors. OIS can be triggered by ectopic overexpression of HER2, a receptor tyrosine kinase and the driving oncogene in a subtype of human breast cancer. However, cellular senescence has not been characterized in HER2-positive tumors. Using an approach based on their inability to proliferate, we isolated naturally occurring senescent cells from a variety of tumor models including HER2-positive cells, transgenic mice (n = 3), and patient-derived xenografts (PDXs) (n = 6 mice per group from one PDX derived from one patient). Using different biochemical and cell biological techniques, we characterized the secretome of these senescent cells. All statistical tests were two-sided. We found that senescent cells arise constantly in different models of advanced breast cancers overexpressing HER2 and constitute approximately 5% of tumor cells. In these models, IL-6 and other cytokines were expressed mainly, if not exclusively, by the naturally occurring senescent cells (95.1% and 45.0% of HCC1954 cells and cells from a HER2-positive PDX expressing a senescent marker expressed IL-6, respectively). Furthermore, inhibition of IL-6 impaired the growth of the HER2-positive PDX (mean tumor volume at day 101, control vs anti-huIL-6 treated, 332.2mm(3) [95% confidence interval {CI} = 216.6 to 449.8] vs 114.4mm(3) [95% CI = 12.79 to 216.0], P = .005). Senescent cells can contribute to the growth of tumors by providing cytokines not expressed by proliferating cells, but required by these to thrive.

Abstract P1-07-16: Galectin-7 increases resistance of breast cancer cells to drug-induced apoptosis and promotes tumor escape by killing T cells

Abstract Resistance to apoptosis induced by anti-cancer drugs is a major obstacle for the treatment of aggressive forms of breast cancer. Galectin-7 was recently shown to be specifically expressed in basal-like and HER-2 positive but not in luminal subtypes of human breast cancer. Galectin-7 also increases the metastatic behavior of breast cancer cells since overexpression of this protein in poorly metastatic breast cancer cells increases their ability to metastasize to the bone and to the lung. This pro-tumoral activity of galectin-7 in breast cancer is surprising since galectin-7 had been previously associated with activation of p53 and breast cancer cells often harbor a transcriptionally inactive form of p53. We have recently reconcile this apparent contradiction by showing that elevated levels of galectin-7 in breast cancer cells occurs via a gain-of-function mechanism of mutant p53. In p53-null breast cancer cells, we have shown that C/EBPβ-2 (also known as LAP2), the most transcriptionally active of the C/EBPβ isoforms, is responsible for the upregulation of galectin-7. How galectin-7 contributes to the progression of breast cancer remains unclear. Up to now, regulation of apoptosis by intracellular galectins has been largely attributed to their ability to translocate to mitochondria, possibly following their interaction with bcl-2. Here, we report that a mutant of galectin-7 that is unable to translocate to mitochondria induces resistance of human breast cancer cells to apoptosis induced by etoposide or by hypoxia-mimicking conditions. Surprisingly, this mutant and the wild-type form of galectin-7 bind equally well to bcl-2 in vitro and in vivo. Interestingly, both forms decreases the translocation of p53 to the nucleus and reduce the expression of p21 following treatment with doxorubicin. We also found that galectin-7 was released by breast cancer cells and that recombinant galectin-7 increased apoptosis of monocytes, T CD4+ and T CD8+ cells. This suggests that galectin-7 contributes to the establishment of an immunosuppressive tumor microenvironment by killing helper and effector T cells. Taken together, these results challenges the current paradigm that mitochondrial galectins are important for resistance to apoptosis and call for a greater focus on the role of galectin-7 in breast cancer. They also indicate that targeting both cytosolic and extracellular galectin-7 could improve the efficacy of anti-cancer drugs for the treatment of aggressive forms of breast cancer. Citation Format: Yves St-Pierre, Andrée-Anne Grosset, Marilyne Labrie, Donald Gagné, Maria-Claudia Vladoiu, Louis Gaboury, Nicolas Doucet. Galectin-7 increases resistance of breast cancer cells to drug-induced apoptosis and promotes tumor escape by killing T cells [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-07-16.

Mouse models of breast cancer.

Breast cancer is the most common cause of cancer death in women worldwide. This malignancy is a complex disease, which is defined by an intrinsic heterogeneity on the histopathological and molecular level as well as response to therapy and outcome. In addition to classical histopathological features, breast cancer can be categorized into at least five major subtypes based on comprehensive gene expression profiling: luminal A, luminal B, basal-like, ERBB2-positive, and normal-like breast cancer. Genetically engineered mouse models can serve as tools to study the molecular underpinnings for this disease. Given the genetic complexity that drives the initiation and progression of individual breast cancer subtypes, it is evident that certain models can reflect only particular aspects of this malignancy. In this book chapter, we will primarily focus on advances in modeling breast cancer at defined stages of carcinogenesis using genetically engineered mice. We will discuss the ability as well as shortcomings of these models to faithfully recapitulate the spectrum of human breast cancer subtypes.