RAGE inhibitor TTP488 (Azeliragon) suppresses metastasis in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and metastatic cancer subtype, which is generally untreatable once it metastasizes. We hypothesized that interfering with the Receptor for Advanced Glycation End-products (RAGE) signaling with the small molecule RAGE inhibitors (TTP488/Azeliragon and FPS-ZM1) would impair TNBC metastasis and impair fundamental mechanisms underlying tumor progression and metastasis. Both TTP488 and FPS-ZM1 impaired spontaneous and experimental metastasis of TNBC models, with TTP488 reducing metastasis to a greater degree than FPS-ZM1. Transcriptomic analysis of primary xenograft tumor and metastatic tissue revealed high concordance in gene and protein changes with both drugs, with TTP488 showing greater potency against metastatic driver pathways. Phenotypic validation of transcriptomic analysis by functional cell assays revealed that RAGE inhibition impaired TNBC cell adhesion to multiple extracellular matrix proteins (including collagens, laminins, and fibronectin), migration, and invasion. Neither RAGE inhibitor impaired cellular viability, proliferation, or cell cycle in vitro. Proteomic analysis of serum from tumor-bearing mice revealed RAGE inhibition affected metastatic driver mechanisms, including multiple cytokines and growth factors. Further mechanistic studies by phospho-proteomic analysis of tumors revealed RAGE inhibition led to decreased signaling through critical BC metastatic driver mechanisms, including Pyk2, STAT3, and Akt. These results show that TTP488 impairs metastasis of TNBC and further clarifies the signaling and cellular mechanisms through which RAGE mediates metastasis. Importantly, as TTP488 displays a favorable safety profile in human studies, our study provides the rationale for evaluating TTP488 in clinical trials to treat or prevent metastatic TNBC.

Propagated Circulating Tumor Cells Uncover the Potential Role of NFκB, EMT, and TGFβ Signaling Pathways and COP1 in Metastasis

Circulating tumor cells (CTCs), a population of cancer cells that represent the seeds of metastatic nodules, are a promising model system for studying metastasis. However, the expansion of patient-derived CTCs ex vivo is challenging and dependent on the collection of high numbers of CTCs, which are ultra-rare. Here we report the development of a combined CTC and cultured CTC-derived xenograft (CDX) platform for expanding and studying patient-derived CTCs from metastatic colon, lung, and pancreatic cancers. The propagated CTCs yielded a highly aggressive population of cells that could be used to routinely and robustly establish primary tumors and metastatic lesions in CDXs. Differential gene analysis of the resultant CTC models emphasized a role for NF-κB, EMT, and TGFβ signaling as pan-cancer signaling pathways involved in metastasis. Furthermore, metastatic CTCs were identified through a prospective five-gene signature (BCAR1, COL1A1, IGSF3, RRAD, and TFPI2). Whole-exome sequencing of CDX models and metastases further identified mutations in constitutive photomorphogenesis protein 1 (COP1) as a potential driver of metastasis. These findings illustrate the utility of the combined patient-derived CTC model and provide a glimpse of the promise of CTCs in identifying drivers of cancer metastasis.

Abstract B46: Immune characterization of C57BL/6J syngeneic breast cancer mouse models for application in immunotherapy development

Background: Breast cancer is the second leading cause of cancer-related mortality in women worldwide. While immunotherapy has shown success in various solid tumors, it has been largely ineffective in breast cancer. Critical to establishing effective immunotherapies in breast cancer is the development and better characterization of the tumor immunology of immunocompetent syngeneic models. Here, we describe the molecular and in-depth immunological characterization of three C57BL/6J syngeneic breast cancer mouse models: AT3, Py8119 and E0771 cells. Methods: AT3, Py8119, and E0771 cells were obtained from commercial sources. 5x105 cells were implanted orthotopically in 8 weeks old C57BL/6J female mice. Tumors were isolated from mice and breast cancer subtype classification was performed by immunohistochemical (IHC) staining of estrogen receptor alpha (ERα), progesterone receptor (PR) and Erb-B2 Receptor Tyrosine Kinase 2 (ERBB2/HER2). T cell and myeloid cell infiltration patterns of the tumors were determined by CD3 and CD11b IHC staining respectively. Immunophenotyping of splenic immune cell populations and tumor-infiltrating immune cells was performed with multicolor flow cytometry in all three models. Results: Based on the IHC analysis of the orthotopic murine tumors, E0771 and Py8119 tumors fit the histopathological criteria of triple-negative breast cancer models, while AT3 tumors appear to be a model of the HER2-enriched breast cancer subtype. We show significant differences between the AT3, Py8119 and E0771 models regarding the accumulation of myeloid cells (mMDSC, gMDSC, macrophages, dendritic cells) in the tumor and spleen. Furthermore, analysis of tumor-infiltrating CD4 and CD8 T lymphocytes showed high expression levels of PD-1 in all three models, and varying levels of expression of other immune checkpoint molecules (CTLA4, TIM3, LAG3 and PD-L1) that were model specific. Furthermore, flow cytometry analysis also revealed high levels of PD-L1 expression on all three tumor cell types. Conclusion: In summary, we determined the breast cancer molecular subtype, and described the splenic and intratumoral immune landscape of the AT3, Py8119 and E0771 orthotopic C57BL/6J syngeneic breast cancer mouse models. These data will aid the better design of future tumor immunological studies and provide essential knowledge about these preclinical breast cancer models for use in immunotherapy development.

Citation Format: Melinda Magna, Marc E Lippman, Barry I Hudson. Immune characterization of C57BL/6J syngeneic breast cancer mouse models for application in immunotherapy development [abstract]. In: Proceedings of the AACR Special Conference: Tumor Immunology and Immunotherapy; 2022 Oct 21-24; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(12 Suppl):Abstract nr B46.

Relationships Between Serum Cortisol, RAGE-Associated s100A8/A9 Levels, and Self-Reported Cancer-Related Distress in Women With Nonmetastatic Breast Cancer

OBJECTIVE

Elevated inflammation and psychological distress in patients with breast cancer (BCa) have been related to poorer health outcomes. Regulation of the hypothalamic-pituitary-adrenal axis and signaling of the receptor for advanced glycation end products (RAGE) are important in the inflammatory response and have been associated with increased stress and poorer health outcomes in patients with cancer. This study examined relationships among circulating cortisol, a measure of hypothalamic-pituitary-adrenal axis activity and physiological stress; s100A8/A9, a RAGE ligand and emerging cancer-related biological measure; and self-reported cancer-related distress.

METHODS

Patients with BCa ( N = 183, stages 0-IIIb) were recruited 2 to 10 weeks after surgery but before receiving adjuvant therapies. Participants provided blood samples, from which serum cortisol and s100A8/A9 levels were determined, and completed a psychosocial questionnaire. Regression analyses, adjusting for age, cancer stage, time since surgery, race, and menopausal status, were conducted examining the relationships between cortisol, s100A8/A9, and cancer-related distress (Impact of Event Scale [IES]-Revised).

RESULTS

Cortisol and s100A8/A9 levels were positively related ( β = 0.218, t (112) = 2.332, p = .021), although the overall model was not significant. Cortisol levels were also positively associated with IES-Intrusions ( β = 0.192, t (163) = 2.659, p = .009) and IES-Hyperarousal subscale scores ( β = 0.171, t (163) = 2.304, p = .022).

CONCLUSIONS

Patients with higher cortisol levels also reported higher s100A8/A9 levels and more cancer-related distress. The relationship between cortisol and s100A8/A9 supports a link between the stress response and proinflammatory physiological processes known to predict a greater metastatic risk in BCa. Stress processes implicated in cancer biology are complex, and replication and extension of these initial findings are important.

Abstract P1-08-05: Expression of the human APOE4 genotype modulates Doxorubicin cardiotoxicity in mice

Background: The human apolipoprotein E (APOE) gene has three major allelic variants: APOE2, -E3 and -E4. Carriers of the E4 allele are at increased risk for Alzheimer’s and other age-related neurodegenerative disorders. Recently, APOE4 has been associated with risk for cancer-related cognitive decline following chemotherapy with Doxorubicin (DOX), a frequent component of adjuvant therapy for breast cancer. To date, the mechanisms for APOE4 neurotoxicity are unknown, but may greater vulnerability to oxidative stress. DOX also causes dose-dependent cardiotoxicity, but a role for APOE4 in heart damage has not been previously demonstrated. Objective: To determine whether APOE4 predisposes to DOX-induced damage to the myocardium. Methods: C57Bl/6 mice (5-7 mo and 14-18 mo, male and female) with human APOE3 or APOE4 homozygous knock-in (=hAPOE3 and hAPOE4, respectively) were subjected to a single IP injection of saline (Control) or DOX (10 mg/kg, or 5 weekly injections of 5 mg/kg, =DOX), and monitored between 3-45 days afterward. Left ventricular systolic function was quantitated using echocardiography (Vevo 3100) at baseline, during and at the end of each study. TUNEL assay was used to identify apoptotic cells. Collagen was imaged using Masson’s Trichrome staining. Myocardial protein and RNA were extracted from the left ventricle and was analyzed by immunoblotting, realtime PCR and RNASeq on an Illumina NexGen platform.Results: Aged female APOE4 mice had more myocardial collagen at baseline (8.93±1.23 vs. 6.06±1.44%). Baseline cardiac function were similar at baseline in the 2 mouse strains. Three days after DOX, apoptotic myocytes were more abundant in hAPOE4 vs hAPOE3 hearts (1.2 vs. 4.6 TUNEL+ cells per section, n= 5, p<0.05). After DOX treatment, hAPOE4 mice had greater declines in left ventricular ejection fraction (EF, 46.9 vs 62.1%, p = hAPOE4 vs hAPOE3, p < 0.001). Quantitative PCR, RNASeq and protein studies revealed multiple differences in the cardiac transcriptome between hAPOE3 and hAPOE4 mice both at baseline and after DOX treatment. Baseline expression of MEF2D, a key driver of the myocardial stress response, was increased in hAPOE4 vs APOE3, driven by a 3500x (p = 4.76E-17) in transcript variant 1. Robust differences were seen in expression of c-Jun, JunB, and myosin heavy chain genes Myh6 and Myh7 at baseline and following DOX treatment at day 3. Growth Arrest And DNA Damage Inducible Alpha(GADD45A) gene expression was ~2x higher in hAPOE4 mice at baseline, but was similar to hAPOE3 mice by day 14 after DOX. Protein levels of caspase-1, an essential regulator of inflammation and the innate immune response, increased with age in hAPOE3 mice. In contrast, levels of casp-1 were lower in hAPOE4 and did not increase with age (p= 0.002 for APOE4 vs APOE3 at 17 mo). Conclusions: These findings support a model in which the APOE4 allele increases vulnerability to DOX-induced cardiac damage through mechanisms that involve significant and complex alterations in the response to oxidative stress and/or damage signaling. Studies are ongoing to further elucidate transcriptional differences conferred by APOE4, to analyze substrates downstream of caspase-1 affected by APOE4, and to determine the extent to which APOE4 may contribute to DOX toxicity in patient populations.

Citation Format: Guannan Wang, G. William Rebeck, Olga Rodriguez, Marc E. Lippman, Nanette H. Bishopric. Expression of the human APOE4 genotype modulates Doxorubicin cardiotoxicity in mice [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-08-05.

The role of estrogen receptor signaling in suppressing the immune response to cancer

Immune checkpoint blockade (ICB) therapies are standard of care for the treatment of many solid tumors. While some patients with cancer experience exceptional and long-term responses, intrinsic and acquired mechanisms of resistance limit the clinical efficacy of ICBs. In addition, ICBs can elicit life-threatening side effects. Alternative options that can increase ICB responses without added toxicities are needed. In this issue of the JCI, Chakraborty et al. explored the role of estrogen receptor α (ERα) in modulating ICB activity. Using transcriptomics and preclinical melanoma models, the authors show that ERα signaling in tumor-associated macrophages contributed to an immune-suppressive state within the tumor microenvironment (TME) by promoting CD8+ T cell dysfunction and exhaustion. Further, in murine melanoma models, the addition of fulvestrant, a selective estrogen receptor downregulator (SERD) approved for the treatment of breast cancer, enhanced the antitumor effects of ICB. These results provide a rationale for human trials to test the combination of antiestrogens with ICBs.

Applying a Life Course Biological Age Framework to Improving the Care of Individuals With Adult Cancers: Review and Research Recommendations

Importance

The practice of oncology will increasingly involve the care of a growing population of individuals with midlife and late-life cancers. Managing cancer in these individuals is complex, based on differences in biological age at diagnosis. Biological age is a measure of accumulated life course damage to biological systems, loss of reserve, and vulnerability to functional deterioration and death. Biological age is important because it affects the ability to manage the rigors of cancer therapy, survivors' function, and cancer progression. However, biological age is not always clinically apparent. This review presents a conceptual framework of life course biological aging, summarizes candidate measures, and describes a research agenda to facilitate clinical translation to oncology practice.

Observations

Midlife and late-life cancers are chronic diseases that may arise from cumulative patterns of biological aging occurring over the life course. Before diagnosis, each new patient was on a distinct course of biological aging related to past exposures, life experiences, genetics, and noncancer chronic disease. Cancer and its treatments may also be associated with biological aging. Several measures of biological age, including p16INK4a, epigenetic age, telomere length, and inflammatory and body composition markers, have been used in oncology research. One or more of these measures may be useful in cancer care, either alone or in combination with clinical history and geriatric assessments. However, further research will be needed before biological age assessment can be recommended in routine practice, including determination of situations in which knowledge about biological age would change treatment, ascertaining whether treatment effects on biological aging are short-lived or persistent, and testing interventions to modify biological age, decrease treatment toxic effects, and maintain functional abilities.

Conclusions and Relevance

Understanding differences in biological aging could ultimately allow clinicians to better personalize treatment and supportive care, develop tailored survivorship care plans, and prescribe preventive or ameliorative therapies and behaviors informed by aging mechanisms.

Heterotypic clustering of circulating tumor cells and circulating cancer-associated fibroblasts facilitates breast cancer metastasis

BACKGROUND

Cancer-associated fibroblasts (CAFs) are recruited to the tumor microenvironment (TME) and are critical drivers of breast cancer (BC) malignancy. Circulating tumor cells (CTCs) travel through hematogenous routes to establish metastases. CTCs circulate both individually and, more rarely, in clusters with other cell types. Clusters of CTCs have higher metastatic potential than single CTCs. Previously, we identified circulating CAFs (cCAFs) in patients with BC and found that while healthy donors had no CTCs or cCAFs, both were present in most Stage IV patients. cCAFs circulate individually, as cCAF-cCAF homotypic clusters, and in heterotypic clusters with CTCs.

METHODS

In this study, we evaluate CTCs, cCAFs, and heterotypic cCAF-CTC clusters in patients with stage I-IV BC. We evaluate the association of heterotypic clusters with BC disease progression and metastasis in a spontaneous mouse model. Using previously established primary BC and CAF cell lines, we examine the metastatic propensity of heterotypic cCAF-CTC clusters in orthotopic and tail vein xenograft mouse models of BC. Using an in vitro clustering assay, we determine factors that may be involved in clustering between CAF and BC cells.

RESULTS

We report that the dissemination of CTCs, cCAFs, and clusters is an early event in BC progression, and we find these clusters in all clinical stages of BC. Furthermore, cCAFs-CTC heterotypic clusters have a higher metastatic potential than homotypic CTC clusters in vivo. We also demonstrate that the adhesion and stemness marker CD44, found on a subset of CTCs and CAF cells, is  involved in heterotypic clustering of these cells.

CONCLUSION

We identify a novel subset of circulating tumor cell clusters that are enriched with stromal CAF cells in BC patient blood and preclinical mouse models of BC metastasis. Our data suggest that clustering of CTCs with cCAFs augments their metastatic potential and that CD44 might be an important mediator of heterotypic clustering of cCAFs and BC cells.

Analysis of immune checkpoint blockade biomarkers in elderly patients using large-scale cancer genomics data

2543

Background: Immune checkpoint blockade (ICB) immunotherapy in some cases elicits striking patient responses, but its efficacy appears to be dependent on several incompletely understood factors. Most studies of ICB therapies in elderly patients have concluded that they received no reduced benefit or even increased benefit compared to the younger patients analyzed, despite the systemic age-related immune changes that might be expected to produce a less effective immune response, such as loss of the capacity to generate new naive T cells. To understand and apply these results, it is necessary to investigate the relationship of age and the immune tumor microenvironment. Methods: We apply bioinformatics methods to genomic, transcriptomic, and clinical data from 9,523 patients across 31 cancer types from TCGA, 15,557 patients with breast, colon, or head and neck cancers from Caris Life Sciences, and 37,961 patients across 8 cancer types collected by GENIE. From these data we apply multivariate linear models across and within individual tumor types to estimate age-related associations to tumor mutational burden (TMB), T cell receptor diversity (miTCR), differential gene expression (edgeR), pathway enrichment (mSigDB and fgsea), and immune cell type infiltration (Quantiseq and MIXTURE). Results: Our analysis of large-scale molecular and clinical databases associates patient age with changes in several major biomarkers of ICB response. Notably, a robust correlation between increased tumor mutational burden and age was found across three different large cohorts (TCGA, Caris Life Sciences, and GENIE) in most ICB-approved cancer types. In the TCGA data, TMB increased with age pan-cancer (p < 1x10-16) and in 7 of 9 ICB-approved cancer types. These associations were validated in the larger cohort of patient samples in GENIE, which demonstrated correlations between increased TMB levels and patient age in all eight ICB-approved cancer types assayed (Table), as well as in the Caris colorectal (q < 0.001) and breast (q < 0.001) cancer cohorts. Significant associations of age to other biomarkers of ICB response (checkpoint gene expression, immune infiltration, and immune related pathway signaling) will be presented. Conclusions: These results provide context for the efficacy of ICB in elderly patients, highlight potential biomarkers for the treatment of elderly patients with immunotherapies, and strongly suggest the value of large-scale prospective study of elderly cancer patients treated with ICB.[Table: see text]

Effects of brief stress management interventions on distress and leukocyte nuclear factor kappa B expression during primary treatment for breast cancer: A randomized trial

BACKGROUND

A randomized controlled trial (RCT) of 5-week stress management interventions teaching cognitive behavioral therapy (CBT) or relaxation training (RT) techniques showed decreases in stress and serum inflammatory markers over 12 months in women undergoing treatment for breast cancer (BCa). To understand the molecular mechanisms involved, we examined the effects of these interventions on the transcription factor NF-κB DNA binding activity in leukocytes in parallel with circulating inflammatory markers, stress management skill efficacy and multiple distress indicators.

METHODS

This is a secondary analysis using blood samples of 51 BCa patients (Stage 0-III) with high cancer-specific distress selected from a completed RCT (NCT02103387). Women were randomized to one of three conditions, CBT, RT or health education control (HE). Blood samples and self-reported distress measures (Affects Balance Scale-Negative Affect [ABS-NA], Impact of Events Scale-hyperarousal [IES-H] and intrusive thoughts [IES-I]) were collected at baseline (T0) and 12-month follow-up (T2). Self-reported distress measures and perceived stress management skills (PSMS) were also measured immediately post-intervention (baseline + 2 months: T1). Repeated measures analyses compared changes in distress and NF-κB expression among conditions, controlling for age, stage of cancer, days from surgery to baseline, and receipt of chemotherapy and radiation. Regression analyses related T0 to T2 change in NF-κB expression with T0 to T1 changes in self-reported PSMS and distress measures. Exploratory regression analyses also associated change in NF-κB expression with change in serum cytokines (IL-1β, IL-6 and TNF-α); and s100A8/A9, a circulating inflammatory marker important in breast cancer progression.

RESULTS

There was a significant condition (CBT/RT, HE)xtime (T0, T2) effect on NF-κB, F(1, 39)= 5.267, p = 0.036, wherein NF-κB expression significantly increased over time for HE but did not change for RT or CBT. Greater increases in PSMS from T0 to T1 were associated with less increase in NF-κB expression over 12 months (β = -0.426, t(36) = -2.637, p = 0.048). We found that women assigned to active intervention (CBT/RT) had significant decreases in ABS-NA (F(1, 40)= 6.537, p = 0.028) and IES-I (F(1, 40)= 4.391, p = 0.043) from T0 to T1 compared to women assigned to HE, who showed no change over time (p's > 0.10). For women assigned to CBT or RT, lower NF-κB expression at T2 was related to less ABS-NA, IES-H, and IES-I, all p's < 0.05, although T0-T1 change in distress was not related to T0-T2 change in NF-κB expression for those in an active intervention.

CONCLUSIONS

Brief CBT or RT stress management interventions can mitigate increases in pro-inflammatory leukocyte NF-κB binding over 12 months of primary treatment in highly distressed BCa patients. These effects are likely brought about by improved stress management skills.

Hormone-Dependent Prostate Cancers are Dependent on Rac Signaling for Growth and Survival

Prostate cancer remains a common cause of cancer mortality in men. Initially, cancers are dependent of androgens for growth and survival. First line therapies reduce levels of circulating androgens or target the androgen receptor (AR) directly. Although most patients show durable responses, many patients eventually progress to castration-resistant prostate cancer (CRPC) creating a need for alternative treatment options. The Rac1 signaling pathway has previously been implicated as a driver of cancer initiation and disease progression. We investigated the role of HACE1, the E3 ubiquitin ligase for Rac1, in prostate cancer and found that HACE1 is commonly lost resulting in hyperactive Rac signaling leading to enhanced cellular proliferation, motility and viability. Importantly, we show that a Rac inhibitor can attenuate the growth and survival of prostate cancer cells. Rac signaling was also found to be critical in prostate cancers that express the AR. Rac inhibition in androgen dependent cells resulted in reduction of AR target gene expression suggesting that targeting Rac1 may be an alternative method for blocking the AR signaling axis. Finally, when used in combination with AR antagonists, Rac inhibition enhanced the suppression of AR target gene expression. Therefore, targeting Rac in prostate cancer has the potential to enhance the efficacy of approved AR therapies.

The Major Pre- and Postmenopausal Estrogens Play Opposing Roles in Obesity-Driven Mammary Inflammation and Breast Cancer Development

Many inflammation-associated diseases, including cancers, increase in women after menopause and with obesity. In contrast to anti-inflammatory actions of 17β-estradiol, we find estrone, which dominates after menopause, is pro-inflammatory. In human mammary adipocytes, cytokine expression increases with obesity, menopause, and cancer. Adipocyte:cancer cell interaction stimulates estrone- and NFκB-dependent pro-inflammatory cytokine upregulation. Estrone- and 17β-estradiol-driven transcriptomes differ. Estrone:ERα stimulates NFκB-mediated cytokine gene induction; 17β-estradiol opposes this. In obese mice, estrone increases and 17β-estradiol relieves inflammation. Estrone drives more rapid ER+ breast cancer growth in vivo. HSD17B14, which converts 17β-estradiol to estrone, associates with poor ER+ breast cancer outcome. Estrone and HSD17B14 upregulate inflammation, ALDH1 activity, and tumorspheres, while 17β-estradiol and HSD17B14 knockdown oppose these. Finally, a high intratumor estrone:17β-estradiol ratio increases tumor-initiating stem cells and ER+ cancer growth in vivo. These findings help explain why postmenopausal ER+ breast cancer increases with obesity, and offer new strategies for prevention and therapy.

Rac Signaling Drives Clear Cell Renal Carcinoma Tumor Growth by Priming the Tumor Microenvironment for an Angiogenic Switch

Clear cell renal cell carcinoma (ccRCC) remains a common cause of cancer mortality. Better understanding of ccRCC molecular drivers resulted in the development of antiangiogenic therapies that block the blood vessels that supply tumors with nutrients for growth and metastasis. Unfortunately, most ccRCC patients eventually become resistant to initial treatments, creating a need for alternative treatment options. We investigated the role of the small GTPase Rac1 in ccRCC. Analysis of ccRCC clinical samples indicates that Rac signaling drives disease progression and predicts patients with poorer outcomes. Investigation of Rac1 identifies multiple roles for Rac1 in the pathogenesis of ccRCC. Rac1 is overexpressed in RCC cell lines and drives proliferation and migratory/metastatic potential. Rac1 is also critical for endothelial cells to grow and form endothelial tubular networks potentiated by angiogenic factors. Importantly, Rac1 controls paracrine signaling of angiogenic factors including VEGF from renal carcinoma cells to surrounding blood vessels. A novel Rac1 inhibitor impaired the growth and migratory potential of both renal carcinoma cells and endothelial cells and reduced VEGF production by RCC cells, thereby limiting paracrine signaling both in vitro and in vivo Lastly, Rac1 was shown to be downstream of VEGF receptor (VEGFR) signaling and required for activation of MAPK signaling. In combination with VEGFR2 inhibitors, Rac inhibition provides enhanced suppression of angiogenesis. Therefore, targeting Rac in ccRCC has the potential to block the growth of tumor cells, endothelial cell recruitment, and paracrine signaling from tumor cells to other cells in the tumor microenvironment.

Abstract P3-01-11: Targeting RAGE inhibits breast cancer invasion and metastasis

Background: Breast cancer (BC) is treatable with early detection, but once metastasis occurs, there is no cure. Therefore, it is of upmost importance to find targetable biomarkers that are involved in modulating the multi-step metastatic process. The Receptor for Advanced Glycation Endproducts (RAGE) and its ligands are an inflammatory pathway that are involved in modulating breast cancer progression and metastasis. We recently demonstrated that genetic or pharmacological interruption of RAGE signaling affected tumor progression and metastasis. However, no studies have dissected the role of RAGE in tumor growth from the metastatic cascade. Here, we show for the first time in multiple metastatic breast cancer models that targeting RAGE impairs BC metastasis.

Methods: We tested the anti-metastatic effect of RAGE in vitro using the RAGE inhibitor FPS-ZM1 or RAGE shRNA knockdown in cell invasion, proliferation, migration and sphere formation assays (with 4T1, Py8119 and E0771 mouse BC cells). For in vivo assays we used orthotopic BC models (4T1/BALB/c and E0771 & Py8119/C57BL6) and experimental metastasis assays (tail vein injection of 4T1/BALB/c and Py8119/C57BL6). To target RAGE, we used genetic (shRNA in 4T1 cells and RAGE knockout in C57BL6 mice) and pharmacological approaches (I.P. injection of FPS-ZM1). To investigate the synergistic effects of RAGE inhibition on progression and metastasis, we tested combination therapy of low-dose doxorubicin and FPS-ZM1.

Results: Inhibition of RAGE with FPS-ZM1 (1-5uM) impaired tumor cell invasion of 4T1, E0771 and Py8119 cells. Similarly, in spheroid assays, treatment of cells with FPS-ZM1 resulted in fewer and smaller colonies. However, FPS-ZM1 treatment did not affect cell proliferation. In vivo studies revealed that FPS-ZM1 (1mg/kg) has a modest effect on tumor growth in 4T1/BALB/c injected mice but displayed a dramatic inhibitory effect on metastasis to the lungs. In experimental metastasis assays, tail-vein injection of 4T1 cells in BALB/c mice demonstrated that FPS-ZM1 treatment strongly impaired metastatic disease in mice compared to controls. To dissect the genetic role of RAGE in the tumor versus host, we test the effect of RAGE knockdown in 4T1 cells in experimental metastasis assays. RAGE shRNA impaired metastasis to the lungs, albeit to a lower degree seen with the RAGE inhibitor. To test the role of the host, we injected Py8119 cells into wild-type and RAGE knockout (RKO) mice. RKO mice displayed fewer metastatic burden compared to wild-type mice. Finally, in our combination treatment experiments, treatment of 4T1-injected BALB/c mice with Doxorubicin and FPS-ZM1 (alone and in combination), demonstrated that drug combination was more effective in inhibiting lung metastasis than either reagent alone. We are currently assessing how RAGE mechanistically drives these metastatic changes.

Conclusion: Our data strongly suggests RAGE plays an important role in breast cancer metastasis, with less of an effect on tumor growth. Ongoing studies in our lab are testing which stage of the metastatic cascade RAGE is involved in, and the underlying mechanisms driving these processes. In conclusion, the use of RAGE inhibitors could represent a novel therapeutic approach for metastatic breast cancer.

Citation Format: Gyong Ha Hwang, Melinda Magna, Barbara Mera, Toni Yeasky, Taekyoung Kwak, Lucas Outcault, Masaru Takabatake, Thuy-Mai Le, Marc E. Lippman, Barry I. Hudson. Targeting RAGE inhibits breast cancer invasion and metastasis [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-01-11.

Paget's disease of the nipple in a Her2-positive breast cancer xenograft model

PURPOSE

Paget's disease (PD) of the breast is an uncommon disease of the nipple usually accompanied by an underlying carcinoma, often HER2 + , and accounting for 0.5-5% of all breast cancer. To date, histogenesis of PD of the breast remains controversial, as two theories-transformation and epidermotropic-have been proposed to explain this disease. Currently, animal models recapitulating PD of the nipple have not been described.

METHODS

HER2-enriched DT13 breast cancer cells were injected into the mammary fat pad of NOD scid gamma null (NSG) female mice. Immunohistochemical staining and pathological studies were performed on tumor samples, and diagnosis of PD of the nipple was confirmed by expression of proteins characteristic of Paget cells (epidermal growth factor 2 (HER2), androgen receptor (AR), cytokeratin 7 (CK7), cytokeratin 8/18 (CK8/18), and mucin 1 (MUC1)). In addition, DT13 cells grown in 2D culture and in soft agar assays were sensitive to in vitro treatment with pharmacological inhibitors targeting Her2, adenylyl cyclase, mTOR, and PI3K signaling pathways.

RESULTS

Mice developed tumors and nipple lesions that were detected exclusively on the tumor-bearing mammary fat pad. Tumor cells were positive for proteins characteristic of Paget cells. In vitro, DT13 cells were sensitive to inhibition of Her2, adenylyl cyclase, mTOR, and PI3K signaling pathways.

CONCLUSIONS

Our results suggest that injection of HER2 + DT13 cells into the mammary fat pad of NSG mice recapitulates critical aspects of the pathophysiology of PD of the nipple, supporting the epidermotropic theory as the more likely to explain the histogenesis of this disease.

A novel RNA aptamer identifies plasma membrane ATP synthase beta subunit as an early marker and therapeutic target in aggressive cancer

PURPOSE

Primary breast and prostate cancers can be cured, but metastatic disease cannot. Identifying cell factors that predict metastatic potential could guide both prognosis and treatment.

METHODS

We used Cell-SELEX to screen an RNA aptamer library for differential binding to prostate cancer cell lines with high vs. low metastatic potential. Mass spectroscopy, immunoblot, and immunohistochemistry were used to identify and validate aptamer targets. Aptamer properties were tested in vitro, in xenograft models, and in clinical biopsies. Gene expression datasets were queried for target associations in cancer.

RESULTS

We identified a novel aptamer (Apt63) that binds to the beta subunit of F1Fo ATP synthase (ATP5B), present on the plasma membrane of certain normal and cancer cells. Apt63 bound to plasma membranes of multiple aggressive breast and prostate cell lines, but not to normal breast and prostate epithelial cells, and weakly or not at all to non-metastasizing cancer cells; binding led to rapid cell death. A single intravenous injection of Apt63 induced rapid, tumor cell-selective binding and cytotoxicity in MDA-MB-231 xenograft tumors, associated with endonuclease G nuclear translocation and DNA fragmentation. Apt63 was not toxic to non-transformed epithelial cells in vitro or adjacent normal tissue in vivo. In breast cancer tissue arrays, plasma membrane staining with Apt63 correlated with tumor stage (p < 0.0001, n = 416) and was independent of other cancer markers. Across multiple datasets, ATP5B expression was significantly increased relative to normal tissue, and negatively correlated with metastasis-free (p = 0.0063, 0.00039, respectively) and overall (p = 0.050, 0.0198) survival.

CONCLUSION

Ecto-ATP5B binding by Apt63 may disrupt an essential survival mechanism in a subset of tumors with high metastatic potential, and defines a novel category of cancers with potential vulnerability to ATP5B-targeted therapy. Apt63 is a unique tool for elucidating the function of surface ATP synthase, and potentially for predicting and treating metastatic breast and prostate cancer.

RAC1b Overexpression Confers Resistance to Chemotherapy Treatment in Colorectal Cancer

Resistance to chemotherapy represents a major limitation in the treatment of colorectal cancer. Novel strategies to circumvent resistance are critical to prolonging patient survival. Rac1b, a constitutively activated isoform of the small GTPase Rac1, is upregulated with disease progression and promotes cell proliferation and inhibits apoptosis by activation of NF-κB signaling. Here, we show that Rac1b overexpression correlates with cancer stage and confirmed Rac1b expression is associated with increased growth through enhancing NF-κB activity. Rac1b knockdown reduced cellular proliferation and reduced NF-κB activity. Surprisingly, Rac1b expression and NF-κB activity were upregulated in cells treated with chemotherapeutics, suggesting that Rac1b facilitates chemo-resistance through activation of NF-κB signaling. Knockdown of Rac1b or Rac inhibition increases the sensitivity of the cells to oxaliplatin. When used in combination, inhibition of Rac prevents the increase in NF-κB activity associated with chemotherapy treatment and increases the sensitivity of the cells to oxaliplatin. Although Rac inhibition or oxaliplatin treatment alone reduces the growth of colorectal cancer in vivo, combination therapy results in improved outcomes compared with single agents alone. We provide the first evidence that Rac1b expression confers resistance to chemotherapy in colorectal cancer. Additionally, we show that the use of a Rac inhibitor prevents chemoresistance by blocking activation of chemotherapy induced NF-κB signaling, providing a novel strategy to overcome resistance to chemotherapy in colorectal cancer.

Abstract PD9-10: Circulating CAF/cancer stem cell co-clusters bolster breast cancer metastasis

Background: Metastatic disease is the primary cause of breast cancer (BC) mortality. Cancer associated fibroblasts (CAFs) are the majority of stroma in BC and critical players in BC malignancy. For example, CAFs are the main source of SDF-1, a prominent chemokine in the tumor microenvironment (TME) that also imparts stem cell-like characteristics to BC cells. Metastasis occurs due to the transport of circulating tumor cells (CTC) and clusters of CTCs through the vasculature. Stem-like CTCs and clusters have a greater propensity to establish metastasis. We recently identified circulating CAFs (cCAFs) in blood from patients with BC and in spontaneous, syngeneic, and xenograft mouse models of BC. cCAFs not only circulate individually, but are also found in clusters with CTCs. In this study, we examine the role of CAFs in promoting egress of stem-like CTCs (cCSCs), determine the capacity of stem-like CTCs to cluster with CAFs, and evaluate the involvement of CTC/cCAF clustering in augmenting BC metastasis.

Methods: Our model employs NSG mice with orthotopic xenograft implantation of BC cells, primary CAF cell lines, or co-implantation of BC and CAF cell lines. We used two different BC cell lines: the non-metastatic BC cell line, MCF-7, and the highly metastatic primary BC cell line, DT28. We also employed the MMTV-PyMT spontaneous model of BC metastasis, and we used BALB/c mice injected with syngeneic 4T1 or 67nR cells to evaluate cCAFs, CTCs, and cluster egress in preclinical models. Mice were sacrificed at specific time points, and cardiac blood was collected. Blood was filtered using the faCTChecker microfluidic filtration instrument (Circulogix). Filters were stained for IF and cCAFs, CTCs, cCSCs, and clusters were enumerated. Tumors from CAF co-injected mice were evaluated for their stem cell-like phenotype and re-implanted in mice to evaluate tumorigenicity and metastasis.

Results: In spontaneous, syngeneic, and orthotopic xenograft models of BC, cCAFs, CTCs, and cCAF/CTCs co-clusters appear early in tumor development. cCAF/CTC clusters increase in correlation with tumor burden and metastasis. Co-inoculation of CAFs with BC cells resulted in a significant increase in tumor progression, metastasis, and in a substantially higher number of both individual cells and clusters in circulation. Dissociated tumor cells from CAF co-injected tumors had a higher proportion of CD44+stem cell-like cells (CSCs), enhanced ALDH-1 expression, and enhanced mammosphere formation. CD44+ CSCs, individually and in clusters, are found early on in the circulation of mice injected with dissociated tumor cells from CAF co-injected tumors. Upon re-implantation of CAF co-injected dissociated tumor cells without CAFs, dissociated tumor cells showed enhanced tumorigenicity and malignancy.

Conclusion: CAFs are highly motile and cCAFs precede CTCs into circulation and can do so independently of tumor cells. CAFs sustain egress of tumor cells by augmenting malignancy and stemness of BC cells. cCAF clusters with the highly metastatic stem cell-like subset of CTCs bolster metastatic colonization. Targeting primary CAF function and/or cCAF/cCSC co-clusters may provide novel avenues to abrogate BC metastasis.

Citation Format: Sharma U, Miller P, Medina Saenz K, Picon-Ruiz M, Morata-Tarifa C, Spartz A, Troness B, Park DN, Seagroves TN, Slingerland JM, Lippman ME, El-Ashry D. Circulating CAF/cancer stem cell co-clusters bolster breast cancer metastasis [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD9-10.

Abstract P5-05-13: Quantitative combinatory indexed ChIP-seq reveals distinct transcriptional complexes containing estrogen receptor and GREB1 at chromatin in breast cancer cells

GREB1 is an estrogen-activated gene in estrogen receptor a (ER)-positive breast cancer cells. GREB1 is also required for estrogen-stimulated breast cancer cell growth and its level is highly correlated to ER level in breast cancer cells and tumor samples. In endocrine resistant diseases, GREB1 is often dysregulated. GREB1 has been shown to interact with ER and bind to the same ER binding sites throughout the genome. There is no identified functional domain in GREB1 and it is not completely known how GREB1 exerts its function to regulate the transcription of ER target genes. In order to demonstrate whether GREB1 is present in the ER-containing transcriptional complex at chromatin, we have adapted and developed a quantitative combinatory indexed ChIP-seq assay suitable for dissecting components in a transcriptional cofactor complex in a genome-wide scale. In ER-positive MCF-7 breast cancer cells, we found that almost all GREB1 binding sites are the same sites bound by ER or its bona fide coactivator SRC-3. We further found that GREB1 and SRC-3 are both present in the same ER-containing complex at chromatin. Thus, both GREB1 and SRC-3 are integral members of the ER transcriptional complex at chromatin. Moreover, we discovered that only a portion of GREB1 at chromatin is present in the ER complex while the other portion of GREB1 is present in a different complex lacking ER or SRC-3 at the same genomic loci. Thus, two distinct GREB1-containing complexes are identified in equilibrium at chromatin: one contains ER/SRC-3 and the other one lacks ER/SRC-3. Our results suggest a non-traditional role of GREB1 in transcriptional regulation of ER target genes. The method used in our study can be widely applied for probing components of transcriptional complexes at chromatin.

Citation Format: Sun J, Lippman ME. Quantitative combinatory indexed ChIP-seq reveals distinct transcriptional complexes containing estrogen receptor and GREB1 at chromatin in breast cancer cells [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-13.

The effects of a randomized trial of brief forms of stress management on RAGE-associated S100A8/A9 in patients with breast cancer undergoing primary treatment

BACKGROUND

Women with breast cancer (BCa) experience heightened distress, which is related to greater inflammation and poorer outcomes. The s100 protein family facilitates the inflammatory response by regulating myeloid cell function through the binding of Toll-like receptor 4 and the receptor for advanced glycation end products (RAGE). The heterodimer s100A8/A9 RAGE ligand is associated with hastened tumor development and metastasis. Previously, a 10-week stress-management intervention using cognitive behavioral therapy (CBT) and relaxation training (RT) was associated with less leukocyte inflammatory gene expression in patients with BCa; however, its impact on s100A8/A9 was not examined. Because a 10-week intervention may be impractical during primary treatment for BCa, the authors developed briefer forms of CBT and RT and demonstrated their efficacy in reducing distress over 12 months of primary treatment. Here, the effects of these briefer interventions were tested effects on s100A8/A9 levels over the initial 12 months of BCa treatment.

METHODS

Postsurgical patients with BCa (stage 0-IIIB) were randomized to a 5-week, group-based condition: CBT, RT, or health education control (HE). At baseline and at 12 months, women provided sera from which s100A8/A9 levels were determined using any enzyme-linked immunosorbent assay.

RESULTS

Participants (mean age ± standard deviation, 54.81 ± 9.63 years) who were assigned to either CBT (n = 41) or RT (n = 38) had significant s100A8/A9 decreases over 12 months compared with those who were assigned to HE (n = 44; F_[1,114]  = 4.500; P = .036) controlling for age, stage, time since surgery, and receipt of chemotherapy or radiation. Greater increases in stress-management skills from preintervention to postintervention predicted greater reductions in s100A8/A9 levels over 12 months (β = -0.379; t_[101]  = -4.056; P < .001).

CONCLUSIONS

Brief, postsurgical, group-based stress management reduces RAGE-associated s100A8/A9 ligand levels during primary treatment for BCa.

Liquid biopsy: expanding the frontier of circulating biomarker discovery and validation in breast cancer

Liquid biopsies represent an attractive, minimally-invasive alternative to surgical sampling or complex imaging of breast cancer and breast cancer metastasis. Here we present a summary of the major biomarker components often evaluated in liquid biopsy samples from patients with breast cancer, including circulating tumor cells, circulating cell-free tumor DNA, and cancer-associated plasma proteins. We discuss recent advancements in methods of detection and use of these biomarkers in breast cancer. Finally, we highlight some of our own recent contributions to breast cancer liquid biopsy, including the identification and characterization of circulating Cancer Associated Fibroblasts.

Avelumab, an anti-PD-L1 antibody, in patients with locally advanced or metastatic breast cancer: a phase 1b JAVELIN Solid Tumor study

PURPOSE

Agents targeting programmed death receptor 1 (PD-1) or its ligand (PD-L1) have shown antitumor activity in the treatment of metastatic breast cancer (MBC). The aim of this study was to assess the activity of avelumab, a PD-L1 inhibitor, in patients with MBC.

METHODS

In a phase 1 trial (JAVELIN Solid Tumor; NCT01772004), patients with MBC refractory to or progressing after standard-of-care therapy received avelumab intravenously 10 mg/kg every 2 weeks. Tumors were assessed every 6 weeks by RECIST v1.1. Adverse events (AEs) were graded by NCI-CTCAE v4.0. Membrane PD-L1 expression was assessed by immunohistochemistry (Dako PD-L1 IHC 73-10 pharmDx).

RESULTS

A total of 168 patients with MBC, including 58 patients with triple-negative breast cancer (TNBC), were treated with avelumab for 2-50 weeks and followed for 6-15 months. Patients were heavily pretreated with a median of three prior therapies for metastatic or locally advanced disease. Grade ≥ 3 treatment-related AEs occurred in 13.7% of patients, including two treatment-related deaths. The confirmed objective response rate (ORR) was 3.0% overall (one complete response and four partial responses) and 5.2% in patients with TNBC. A trend toward a higher ORR was seen in patients with PD-L1+ versus PD-L1- tumor-associated immune cells in the overall population (16.7% vs. 1.6%) and in the TNBC subgroup (22.2% vs. 2.6%).

CONCLUSION

Avelumab showed an acceptable safety profile and clinical activity in a subset of patients with MBC. PD-L1 expression in tumor-associated immune cells may be associated with a higher probability of clinical response to avelumab in MBC.

Targeting RAGE Signaling in Inflammatory Disease

The receptor for advanced glycation end-products (RAGE) is a multiligand pattern recognition receptor implicated in diverse chronic inflammatory states. RAGE binds and mediates the cellular response to a range of damage-associated molecular pattern molecules (DAMPs) including AGEs, HMGB1, S100s, and DNA. RAGE can also act as an innate immune sensor of microbial pathogen-associated molecular pattern molecules (PAMPs) including bacterial endotoxin, respiratory viruses, and microbial DNA. RAGE is expressed at low levels under normal physiology, but it is highly upregulated under chronic inflammation because of the accumulation of various RAGE ligands. Blocking RAGE signaling in cell and animal models has revealed that targeting RAGE impairs inflammation and progression of diabetic vascular complications, cardiovascular disease (CVD), and cancer progression and metastasis. The clinical relevance of RAGE in inflammatory disease is being demonstrated in emerging clinical trials of novel small-molecule RAGE inhibitors.

Elevated S100A8 protein expression in breast cancer cells and breast tumor stroma is prognostic of poor disease outcome

PURPOSE

Elevated S100A8 expression has been observed in cancers of the bladder, esophagus, colon, ovary, and breast. S100A8 is expressed by breast cancer cells as well as by infiltrating immune and myeloid cells. Here we investigate the association of elevated S100A8 protein expression in breast cancer cells and in breast tumor stroma with survival outcomes in a cohort of breast cancer patients.

PATIENTS AND METHODS

Tissue microarrays (TMA) were constructed from breast cancer specimens from 417 patients with stage I-III breast cancer treated at the University of Michigan Comprehensive Cancer Center between 2004 and 2006. Representative regions of non-necrotic tumor and distant normal tissue from each patient were used to construct the TMA. Automated quantitative immunofluorescence (AQUA) was used to measure S100A8 protein expression, and samples were scored for breast cancer cell and stromal S100A8 expression. S100A8 staining intensity was assessed as a continuous value and by exploratory dichotomous cutoffs. Associations between breast cancer cell and stromal S100A8 expression with disease-free survival and overall survival were determined using the Kaplan-Meier method and Cox proportional hazard models.

RESULTS

High breast cancer cell S100A8 protein expression (as indicated by AQUA scores), as a continuous measure, was a significant prognostic factor for OS [univariable hazard ratio (HR) 1.24, 95% confidence interval (CI) 1.00-1.55, p = 0.05] in this patient cohort. Exploratory analyses identified optimal S100A8 AQUA score cutoffs within the breast cancer cell and stromal compartments that significantly separated survival curves for the complete cohort. Elevated breast cancer cell and stromal S100A8 expression, indicated by higher S100A8 AQUA scores, significantly associates with poorer breast cancer outcomes, regardless of estrogen receptor status.

CONCLUSIONS

Elevated breast cancer cell and stromal S1008 protein expression are significant indicators of poorer outcomes in early stage breast cancer patients. Evaluation of S100A8 protein expression may provide additional prognostic information beyond traditional breast cancer prognostic biomarkers.

A closer look at next generation sequencing (NGS) in breast cancer: A retrospective analysis

e13023

Background: Targeted cancer therapy has been posited to revolutionize treatment paradigms in oncology. There are, a paucity of data regarding the use of NGS in breast cancer (BC). Herein we report our experience with NGS in a consecutive series of BC patients. Methods: Using an IRB approved protocol, we retrospectively identified patients with BC treated at the Sylvester Comprehensive Cancer Center (UMMSOM) who underwent NGS. Data were collected on demographics, tumor characteristics, genomic mutation profiles, and subsequent response to targeted therapy after 3 months. Results: Between January 2013 and April 2016, 101 BC patients underwent NGS. The mean age at diagnosis was 49. Ninety-one percent were stage IV, 6% were stage III, 2% were stage II, and 1% were stage I. Fifty percent had estrogen receptor (ER)+, HER2- tumors, 31% had triple-negative tumors, 13% had HER2+, ER+ tumors, and 6% had HER2+, ER- tumors. Ninety-six percent had at least one mutation, of which 78% had a targetable mutation. Sixteen patients received targeted therapy (TT). The average time between NGS and TT was 5 months ranging 0-22 months, during which seven patients received other systemic therapy. The most common reasons for not receiving TT were no actionable mutations (24%), not meeting criteria for an available clinical trial (14%), stable disease (SD) (13% ), lost to follow up (11%), physician decision (11%). Of the 16 patients who received TT, 7 patients had progression of disease, 3 died before response could be evaluated and presumably had no benefit, 2 discontinued TT due to side effects, 1 had SD, 1 had a partial response, and 2 were too early to be assessed. Conclusions: The majority of BC patients in our series had actionable mutations. However, TT was not offered to a significant number of patients for a multiplicity of reasons and the clinical benefit in those patients treated according to NGS findings was dismal. While NGS is surely a promising technology that should be utilized in combination with molecular tumor board, a host of reasons limit its usefulness at this time and its expense may well not justify its use outside of clinical trials.

Abstract P4-12-13: High intratumoral and stromal S100A8 expression is prognostic of poor outcome in breast cancer

Background: S100A8 and S100A9 are members of a family of calcium binding proteins that regulate inflammatory response, and are biomarkers of inflammatory diseases, S100A8/A9 preferentially form heterodimers that interact with their receptor, RAGE, to activate signaling pathways (ERK1/2 MAPK, JNK, and NF-κB) and stimulate tumor cells. Elevated expression of S100A8/A9 has been observed in cancers of the bladder, esophagus, colon, ovary, and breast. S100A8/A9 are expressed intratumorally by cancer cells and in the stroma by infiltrating immune and myeloid cells as well. We investigated the associations of elevated expression of intratumoral and stromal S100A8 with survival outcomes in breast cancer.

Methods: Tissue microarrays (TMA) were constructed from breast cancer specimens from patients with stage I-III breast cancer treated at the University of Michigan Comprehensive Cancer Center between 2004-2006, ensuring a minimum of 10-year follow-up. Each patient was represented on the TMA by representative regions of non-necrotic tumor and distant normal tissue. Automative Quantitative Immunofluorescence (AQUA) was performed for S100A8 protein, and samples were scored for intratumoral and stromal S100A8 expression. S100A8 staining was assessed as a continuous value and by exploratory dichotomous cutoffs. Associations with disease-free survival (DFS) or overall survival (OS) and S100A8 expression, either as continuous value or based on the exploratory cutoffs, were determined using the Kaplan-Meier method and Cox proportional hazards models.

Results: In the entire patient cohort, high intratumoral S100A8 expression, as a continuous measure, was a significant prognostic factor for OS (univariable hazard ratio [HR] 1.26, 95% confidence interval [CI] 1.02-1.56, p=0.036), and for DFS (multivariable HR [95%CI] = 1.24 [1.01-1.53], p = 0.043). Exploratory analyses demonstrated optimal cutoffs of intratumoral and intrastromal staining that greatly separated survival curves. We evaluated whether the prognostic significance of S100A8 expression is different in breast cancer patients based on hormone receptor status and determined that neither intratumoral nor stromal S100A8 expression were significantly associated with outcomes.

Conclusions: Elevated intratumoral and stromal expression of S100A8 are significant indicators of poor outcome in breast cancer patients. These data further support a biological role for S100A8 signaling in mammary carcinogenesis and aggressive tumor behavior. Evaluation of S100A8 protein expression might provide additional prognostic information beyond traditional breast cancer prognostic biomarkers. Further validation is necessary to investigate these findings.

Citation Format: Miller P, Kidwell K, Thomas D, Sabel M, Rae J, Hayes DF, Lippman ME, El-Ashry D. High intratumoral and stromal S100A8 expression is prognostic of poor outcome in breast cancer [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P4-12-13.

Abstract P6-03-02: Chronic CXCL12 exposure induces a metastatic phenotype in ER-positive breast cancer cells through transcriptional reprogramming

The chemokine CXCL12 is transcriptionally activated by estrogen in estrogen receptor (ER)-positive breast cancer cells. We have found that CXCL12 signaling is essential to maintain the long-term growth of ER-positive breast cancer cells and promotes cancer cell growth in the absence of estrogen. Chronic blockade of CXCL12 signaling with AMD3100, an inhibitor of CXCL12 receptor CXCR4, causes cell death in these cells. Chronic exposure to CXCL12 reprograms ER-positive breast cancer cells through genome-wide transcriptional changes and activates numerous signaling pathways including EMT and the inflammatory response. Many ER target genes are activated in CXCL12-reprogrammed cells even in the absence of estrogen which leads to the diminished estrogen modulated transcription in these cells. These cells also show enhanced signaling via TGFb, EGFR and Rac1 pathways, rendering these cells more sensitive to the CDK7 inhibitor, THZ1, and to drug combinations of THZ1 with the EGFR inhibitor Gefitinib or the RAC1 inhibitor EHT 1864. Furthermore, CXCL12-reprogrammed ER-positive breast cancer cells become more motile in vitro and display a metastatic phenotype in a mouse model. The lung-tropic phenotype of CXCL12-reprogramed MCF-7 cells could be explained by increased expression of integrins and pro-inflammatory signaling molecules. Our novel finding of chronic CXCL12 action on ER-positive breast cancer cells suggests a mechanism by which the interaction between stromal and tumor cells leads to increased breast tumor metastatic potential.

Citation Format: Sun J, Slingerland JM, Lippman ME. Chronic CXCL12 exposure induces a metastatic phenotype in ER-positive breast cancer cells through transcriptional reprogramming [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-03-02.

Abstract P3-06-01: Therapeutic targeting of RAGE in the tumor and tumor microenvironment inhibits breast progression and metastasis

Background: The Receptor for Advanced-Glycation End-products (RAGE) is highly expressed in various cancers and its expression is correlated with poorer outcomes in breast cancer. We have previously implicated RAGE in breast cancer, but whether RAGE drives breast cancer progression and metastasis either through tumor cell intrinsic effects, non-tumor cells of the tumor microenvironment, or both, is not fully understood. More importantly, studies are lacking that target RAGE therapeutically in cancer, and may therefore represent a novel treatment for breast cancer metastasis.

Methods: Using multiple human and murine breast cancer models we dissected the tumor intrinsic versus tumor microenvironment role of RAGE in metastasis. RAGE was targeted in tumor cells using multiple shRNAs, in non-tumor cells by global gene knockout in mice, and both by therapeutically targeting with the novel RAGE inhibitor FPS-ZM1. In vivo orthotopic models included the NSG (NOD-SCID-gamma) xenograft mouse model (with MDA-MB-231 cells; herein 231), BALBc (4T-1 and 67NR), and C57BL6 wild-type and RAGE knockout (RAGE -/-) mice (with MMTV-PyMT spontaneous breast cancer derived AT-3 cells).

Results: We first tested how RAGE impacts tumor cell intrinsic mechanisms using either RAGE shRNAs or FPS-ZM1 in 231, 4175 (231 isogenic highly metastatic cells) and 4T-1 cells. RAGE shRNA and FPS-ZM1 both decreased RAGE MAP-kinase signaling, transwell invasion and soft agar colony formation, without affecting proliferation. In vivo, RAGE shRNA knockdown in 231 cells did not affect tumor growth, but inhibited metastasis to lung and liver. RAGE shRNA knockdown in 4175 cells, decreased orthotopic tumor growth, and reduced tumor angiogenesis and tumor recruitment of leukocyte / macrophages. Furthermore, RAGE shRNA knockdown dramatically decreased metastasis of 4175 cells to lung and liver in a time and sized matched manner compared to shRNA controls. Similarly, RAGE knockdown in 4T-1 cells reduced cell invasion and colony formation, and inhibited lung metastasis from the orthotopic site in BALBc immunocompetent mice.

To test the non-tumor cell microenvironment role of RAGE, we performed syngeneic studies with orthotopically injected AT-3 cells in RAGE +/+ and RAGE -/- C57BL6 mice. RAGE -/- mice displayed striking impairment of tumor cell growth compared to RAGE +/+ mice, along with decreased MAP-kinase signaling, tumor angiogenesis and inflammatory cell recruitment.

Finally, to test the combined inhibition of RAGE in both tumor cell intrinsic and non-tumor cells of the microenvironment, we performed in vivo treatment of 4175 tumors with FPS-ZM1 (1mg/kg, twice per week). Compared to vehicle, FPS-ZM1 inhibited primary tumor growth, inhibited tumor angiogenesis and inflammatory cell recruitment, and most importantly prevented metastasis to lung and liver.

Conclusion: These data clearly demonstrate a role for RAGE in breast cancer progression and metastasis through distinct effects in the tumor cell and non-tumor cells of the tumor microenvironment. Furthermore, our data from drug inhibitor studies highlight the combined targeting of RAGE in the tumor and tumor microenvironment, and as a viable therapeutic means for breast and other metastatic cancers.

Citation Format: Kwak T, Drews-Elger K, Ergonul A, Braley A, Hwang GH, El-Ashry D, Slingerland JM, Lippman ME, Hudson BI. Therapeutic targeting of RAGE in the tumor and tumor microenvironment inhibits breast progression and metastasis [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-06-01.

Abstract P6-01-05: Novel cytotoxic RNA aptamers that distinguish between metastasis-prone and indolent breast and prostate cancers

Background: Prostate and breast cancers are, respectively, the most common malignancies diagnosed in men and women worldwide. These cancers develop in different organs but have significant biological similarities: both are typically hormone-dependent, and both require early detection and treatment, as metastatic disease is incurable. At the same time, early stage tumors are often over-treated. Better markers for tumor aggressiveness would help to optimize treatment strategies in both breast and prostate cancer.

Objective: Develop high affinity nucleic acid oligomers (aptamers) that can distinguish between indolent tumors that will remain organ-confined and those with heightened potential to metastasize.

Methods: We performed subtractive RNA Cell-SELEX to select for surface ligands specific to aggressive tumors, using as a positive selector the highly metastasis-competent LN3 subclone of prostate cancer cell line LNCaP, and as negative selectors parental LNCaP and a non-metastasizing subclone, Pro5. . The RNA aptamer pool was PCR amplified from a 40-mer random nucleotide cDNA library with appropriate flanking sequences, and transcribed in vitro. After 11 SELEX cycles, aptamer pools from cycles 0, 4, 9, and 11 were subjected to high-throughput sequencing. Eight aptamers, representing 4 sequence families, were chosen for further study. Representative relevant and irrelevant aptamers were labeled with Cy3 and used to stain LNCaP-LN3 and LNCaP-Pro5 in culture and as xenografts in NOD-SCID-gamma mice. Additional cell and tumor lines from both breast and prostate cancer were used for validation.

Results: Two aptamers bound avidly to the surface of the aggressive LNCaP-LN3 subclone, both in culture and in fixed xenograft tumors, but not to the indolent Pro5 subclone. Aptamer binding led to rapid and specific cytotoxicity in vitro but had no effect on other cell lines to which the aptamer did not bind. The same aptamers showed similar high specificity for multiple other metastasis-competent cancer cells, including the prostate adenocarcinoma PC-3 and PC-3ML subclones, breast cancer cell lines MDA-MB436 and MDA-MB231, and the primary dissociated breast tumor DT28 , while exhibiting no detectable binding to the non-metastasizing MCF-7 breast cancer cell line and DT22 primary dissociated breast tumor cells, and the non-tumorigenic prostate epithelial cell line RPWE-1.

Conclusion: We identified RNA aptamers that specifically bind to metastasis-prone prostate cancer and breast cancer cell surface targets, and exert cell-specific toxicity dependent upon aptamer binding. While the target(s) remain to be identified, we propose that these aptamers may discriminate between progressive and indolent breast and prostate cancers, and may have substantial promise as anticancer agents either alone or suitably liganded to toxic moieties.

Citation Format: Bishopric NH, Speransky S, Serafini P, De la Fuente AC, Bicciato S, El-Ashry D, Lippman ME. Novel cytotoxic RNA aptamers that distinguish between metastasis-prone and indolent breast and prostate cancers [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P6-01-05.

Abstract 3588: The spindle assembly checkpoint gene Bub1b is essential for the survival of some breast cancers

As normal breast epithelium evolves towards malignancy, cells accumulate genomic changes that give them a replicative advantage while at the same time increasing their genomic instability. Increased genomic instability results in accumulation of genomic aberrations that compromise the genomic integrity and, therefore, threaten cell viability, thus putting cancer cells under mitotic stress. As a consequence, cancer cells evolutionarily must adapt themselves to compete with the possible detrimental effects of genomic instability. Finding a balance between the instability that gives them a replicative advantage and the instability that could lead them to mitotic catastrophe is crucial. The mitotic stress caused by genomic instability may require overexpression of certain spindle assembly checkpoint (SAC) genes, which can prevent mitotic catastrophe that would occur if cancer cells undergo mitosis prematurely. Although the full mechanism of action of SAC is yet to be elucidated, Bub1b through its protein BubR1 is an important part of this checkpoint, and inhibits the onset of anaphase until all chromosomes are aligned correctly at the metaphase plate.

Our analysis of clinical datasets shows a significant increase in the expression of Bub1b in breast cancer as compared to normal epithelia. Furthermore, Bub1b overexpression correlates with decreased overall survival in patient samples. Our analyses also show a pattern of increasing Bub1b overexpression in more aggressive variants of breast cancer such as triple negative tumors and high-grade tumors, which also tend to be more resistant to current therapies. Expression analyses of breast cancer cell lines reveal that Bub1b overexpression is positively correlated with more aggressive behavior.

We postulated that the requirement for Bub1b expression might be a vulnerability of rapidly proliferating cancers; therefore, its inhibition will result in cell death through mitotic catastrophe. Using RNA interference with siRNAs, we reduced Bub1b levels in a variety of breast cancer cells. Our results showed significant decrease in cell viability and clonogenicity in soft agar upon Bub1b knockdown, especially in triple negative breast cancer cell lines. However, the viability of normal breast epithelium cells, MCF12A, was not affected.

Our data indicate that Bub1b is a critical player in breast cancer viability, and further investigation of the role of Bub1b in promoting successful proliferation of breast cancer cells with genomic instability could provide a new therapeutic strategy particularly in concert with standard genotoxic treatments such as alkylators, spindle poisons and radiation therapy.

Citation Format: Dilara Koyuncu, Erik T. Goka, Philip C. Miller, Marc E. Lippman. The spindle assembly checkpoint gene Bub1b is essential for the survival of some breast cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3588.

Abstract 4396: Circulating CAFs and CAF-secreted factors may be indicative of breast cancer metastasis

Tumor metastasis is the main cause of breast cancer mortality. Increasing evidence demonstrates stromal cells play pivotal roles in promoting breast cancer progression and metastasis. Breast cancer stroma is comprised mainly of Cancer Associated Fibroblasts (CAFs). CAFs secrete various growth factors and cytokines that promote breast cancer progression and metastasis; one of these factors is SDF-1 (CXCL12), a soluble chemokine that is promotes chemotaxis and motility, and facilitates cancer cell motility and angiogenesis. CAFs also secrete soluble factors that activate ERK 1/2 MAPK signaling in breast cancer cells, which has been shown to promote loss of estrogen receptor (ER) in luminal breast cancer cells. Hyperactivation of MAPK signaling (hMAPK) also associates with aggressive, basal-like and HER2-positive breast cancer and poor prognosis. Recently, we identified a patient-derived hMAPK-microRNA signature indicative of poor clinical outcome that contains microRNAs known to regulate breast cancer associated genes. The vast majority of ER- breast cancers display this microRNA signature, as do a subset of ER+ breast cancers with poorer clinical outcome. We also discovered that the breast cancers that exhibit this microRNA signature display high stromal and immune infiltrate scores, suggesting that breast cancer stroma provides important contributions to this microRNA signature and the poor clinical outcomes associated with it.

To study the role of CAFs and CAF-secreted factors in breast cancer progression and metastasis, we established primary breast CAF lines from ‘indolent’ breast cancers (Luminal A), and from ‘aggressive’ breast cancers (ER-/HER2 amplified; triple negative). We have demonstrated that these CAFs differentially express several members of the hMAPK-microRNA signature compared to cultured primary breast cancer cells, supporting the contribution of stroma to the signature. Importantly hMAPK-microRNAs secreted from “aggressive” CAFs can be taken up by breast cancer cells, whereupon they repress their targets. Normal human mammary fibroblasts (HMFs) and ‘indolent’ CAFs do not secrete these microRNAs.

We identified a novel class of circulating cells in the blood of breast cancer patients with metastases -CAFs (cCAFs). Patients without metastases did not have these cCAFs - suggesting cCAFs may be “aggressive” CAFs that facilitate breast cancer metastasis. Patients with overt metastasis and elevated counts of cCAFs have significantly higher levels of circulating SDF-1 in their plasma, as well as differential circulating microRNAs, and specifically hMAPK-microRNAs also found secreted by “aggressive” CAFs. Our results suggest there is a hierarchy of CAFs whereby “aggressive” tumors establish “aggressive” CAFs to facilitate metastasis. We also establish a clear link between circulating CAFs and CAF-secreted factors such as SDF-1 and microRNAs with breast cancer metastasis.

Citation Format: Sanket H. Shah, Phil Miller, Leah Machlin, Kelsie Medina-Saenz, Ritesh Parajuli, Marc E. Lippman, Dorraya El-Ashry. Circulating CAFs and CAF-secreted factors may be indicative of breast cancer metastasis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4396.

Abstract P2-05-07: RAGE-ligand signaling drives breast cancer metastasis through affecting cells of the tumor and microenvironment

Breast cancer is most common malignant state in women, with 20% of these patients developing metastasis during the course of their disease. Further understanding is needed of the process and mechanisms of metastasis. Our lab and others have been shown that Receptor of Advanced-Glycation End-products (RAGE) plays a role in tumorigenesis and metastasis. RAGE is highly expressed in various cancers including breast cancer and its protein levels correlate with poor patient outcome in breast cancer and other cancers. Activation of RAGE results in increased proliferation, migration and invasion of cancer cells. Further studies in mice have shown it may be a therapeutic target to reduce tumor growth and the resulting metastasis. Further understanding is needed of the role of RAGE in driving metastasis through affecting cells of both the tumor and tumor stroma to design novel therapeutics. Using the breast cancer cell model (MDA-MB-231) and its organotropic sister cells lines selected in vivo for increased metastasis to lung (4175) and bone (1833), we tested the role of RAGE in driving tumor metastasis in vitro and in vivo with xenograft mouse models. To test the role of RAGE in the tumor microenvironment we used the AT-3 syngeneic breast cancer cell model in C57BL6 wild-type and RAGE knockout mice. We demonstrated that the highly metastatic variant of 231 cells (4175 and 1833) have increased expression level of RAGE compared to MDA-MB-231 parental cells. Ectopic over-expression of RAGE in parental 231 cells led to increased migratory and invasive properties compared to vector control cells, without affecting cell proliferation or viability. RAGE knockdown by shRNA in 4175 and 231 parental cells showed decreased cell invasion in transwell assays compared to control scramble shRNA. To validate our data in vivo, we performed mammary fat pad injection of 4175 cells (RAGE and scr shRNA) in NOD SCID gamma mice. Tumor growth and weight was impaired in RAGE gene knockdown 4175 cells compared to scramble (scr) controls. Analysis of lung and liver tissue retrieved from mice revealed RAGE knockdown in 4175 cells prevented metastasis compared to 4175 scr control cells. To test the role of RAGE on non-tumor cells of the breast stroma we next performed syngeneic studies with AT-3 cells (MMTV-PyMT spontaneous BC cell model), by injection into the mammary fat pad of wild-type and RAGE knockout C57BL6 immunocompetent mice. RAGE knockout mice (RAGE -/-) displayed striking impairment of tumor cell growth compared to wild-type (RAGE +/+) mice. We are currently testing whether novel RAGE inhibitors impact breast cancer progression and metastasis.

These data highlight RAGE drives breast cancer progression and metastasis through affecting both tumor cell intrinsic and non-tumor cell microenvironment effects. Future studies will demonstrate the potential of RAGE inhibition as a novel therapeutic approach for preventing and treating metastatic disease in breast and other cancers.

Citation Format: Kwak T, Drews-Elger K, Ergonul A, Zhao D, Besser A, Slingerland JM, Lippman ME, Hudson BI. RAGE-ligand signaling drives breast cancer metastasis through affecting cells of the tumor and microenvironment. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-05-07.

Abstract P2-02-10: Circulating cells from the tumor microenvironment as liquid biopsy biomarkers alongside circulating tumor cells in metastatic breast cancer

Background: Metastasis is a multistep process that involves the shedding of tumor cells in the peripheral circulation. These Circulating Tumor Cells (CTCs) have prognostic implications in patients with metastatic breast cancer (MBC). Cancer Associated Fibroblasts (CAFs) are a major component of the breast tumor microenvironment. The reciprocal signaling between tumor cells and its microenvironment promotes carcinogenesis, invasion, and metastasis. Studies in mouse models have shown that metastatic cells can bring their own stromal components from the primary site to the site of metastasis, and that these cotraveling stromal cells provide an early growth advantage to the accompanying metastatic cancer cells. CAFs have not been identified in the peripheral circulation. Using a microfilter capture technique, we discovered non-tumor, non-immune cells in the blood of metastatic patients and identified these cells as circulating CAFs (cCAFs). The purpose of this study is to demonstrate the presence of cCAFs as a biomarker of metastasis simultaneously with CTCs in patients with MBC.

Materials and Methods: We identified 20 patients with MBC (Metastatic/MET Group) and 10 patients with cured breast cancer (Ductal carcinoma in situ or Stage I post definitive treatment with &gt;5 years of disease free survival i.e. Localized/LOC Group). A total of 7.5 ml of peripheral blood was obtained from each patient. The enumeration of CTCs and cCAFs was carried out by the microfilter capture technique. Identification of these cells was done by a triple immunofluorescence staining for pan-CK (cytokeratin), FAP (Fibroblast Activated Protein) and CD45. cCAFs were identified as CK-, FAP+, CD45- cells and CTCs as CK+, CD45- cells. Identification and confirmation of cCAF was also carried out in parallel samples by a simultaneous FAP/α-Smooth Muscle Actin staining.

Results: cCAFs were detected in 17/20 (85%) MET patients but in only 2/10 (20%) LOC patients. CTCs were detected in 20/20 (100%) MET patients and in 8/10 (80%) LOC patients. The counts of CTCs and cCAFs in MET group ranged between 1-98 (median 13.5) and 0-117 (median 4), respectively. The counts of CTCs and cCAFs in the LOC group ranged between 1-14 (median 6) and 0-2 (median 0), respectively. For patients with exhibited cCAFs, 2/10 LOC and 5/17 MET patients had cCAFs counts of 2 or less. Although the sample size was small, patients exhibiting cCAFs (odds ratio=22.67, 95% CI: 3.14-163.63, p=0.002) were more likely to be in MET group than LOC group.

Conclusion: This is the first demonstration that CAFs, the predominant mesenchymal cell in the breast tumor microenvironment, are shed into the circulation and can be identified and enumerated as cCAFs in MBC patients along with CTCs. There was a clear difference in the numbers of CTCs and cCAFs levels between the MET and the LOC groups suggesting that CTCs and cCAFs are associated with advanced stage disease. While most patients, both in the LOC and MET group, exhibited CTCs, very few LOC patients exhibited cCAFs. We suggest that cCAFs could independently or along with CTCs serve as liquid biopsy biomarkers of metastasis. Validation of these findings in a larger cohort of patients will be presented during the meeting.

Citation Format: Parajuli R, Ao Z, Shah SH, Sengul TK, Lippman ME, Datar R, El-Ashry D. Circulating cells from the tumor microenvironment as liquid biopsy biomarkers alongside circulating tumor cells in metastatic breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-02-10.

Identification of Cancer-Associated Fibroblasts in Circulating Blood from Patients with Metastatic Breast Cancer

Metastasis is facilitated by cancer-associated fibroblasts (CAF) in the tumor microenvironment through mechanisms yet to be elucidated. In this study, we used a size-based microfilter technology developed by our group to examine whether circulating CAF identified by FAP and α-SMA co-expression (cCAF) could be distinguished in the peripheral blood of patients with metastatic breast cancer. In a pilot study of patients with breast cancer, we detected the presence of cCAFs in 30/34 (88%) patients with metastatic disease (MET group) and in 3/13 (23%) patients with localized breast cancer (LOC group) with long-term disease-free survival. No cCAFs as defined were detected in healthy donors. Further, both cCAF and circulating tumor cells (CTC) were significantly greater in the MET group compared with the LOC group. Thus, the presence of cCAF was associated with clinical metastasis, suggesting that cCAF may complement CTC as a clinically relevant biomarker in metastatic breast cancer.

Abstract 2270: RAGE-ligand signaling drives breast cancer invasion and metastasis

Background: Breast cancer is most common malignant state in women and 20% of these patients will develop metastasis during the course of their disease. Further understanding is needed of the process and mechanisms of metastasis. Our lab and others have been shown that Receptor of Advanced-Glycation End-products (RAGE) plays a role in tumorigenesis and metastasis. RAGE is highly expressed in various cancers including breast cancer and its protein levels correlate with poor patient outcome in breast cancer and other cancers. Activation of RAGE results in increased proliferation, migration and invasion of cancer cells. Further studies in mice have shown its blockade may be a therapeutic target to reduce tumor growth and the resulting metastasis.

Methods: Using the breast cancer cell model (MDA-MB-231) and its organotropic sister cells lines selected in vivo for increased metastasis to lung (4175) and bone (1833), we tested the role of RAGE in driving mechanisms of metastasis in vitro and in vivo.

Results: First, we demonstrated that the highly metastatic variant of 231 cells (4175 and 1833) have increased expression level of RAGE compared to MDA-MB-231 parental cells. Moreover, RAGE knockdown by shRNA in 4175 and 231 parental cells showed decreased cell invasion in transwell assays compared to control scramble shRNA. Ectopic over-expression of RAGE in parental 231 cells led to increased migratory and invasive properties compared to vector control cells, without affecting cell proliferation or viability. To explore the underlying mechanisms we probed for differences in RAGE signaling pathways including MEK/ERK, p38, AKT and SAPK/JNK; with MEK/ERK and Akt showing activation. Using chemical inhibitors of these pathways we demonstrated that the MEK/ERK, but not other pathways inhibited RAGE-driven cell invasion in transwell assays. To validate our data in vivo, we performed mammary fat pad injection of 4175 cells (RAGE and scr shRNA) in NSG mice. Tumor growth and weight was impaired in RAGE gene knockdown 4175 cells compared to scramble (scr) controls. Analysis of lung tissue retrieved from mice revealed RAGE knockdown in 4175 cells resulted in less metastasis compared to 4175 scr control cells.

Conclusion: We have shown that higher RAGE levels are seen in metastatic human breast cancer BC cells. RAGE gene knockdown in metastatic BC cells reduces their invasive properties in vitro and reduces tumor progression and metastasis in vivo in NSG mice.

These data highlight RAGE as a novel therapeutic target for metastatic disease in breast and other cancers.

Citation Format: Taekyoung Kwak, Katherine Drews-Elger, Dekuang Zhao, Alexander Besser, Ayse Ergonul, Joyce M. Slingerland, Marc E. Lippman, Barry I. Hudson. RAGE-ligand signaling drives breast cancer invasion and metastasis. [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 2270. doi:10.1158/1538-7445.AM2015-2270

Loss of the E3 ubiquitin ligase HACE1 results in enhanced Rac1 signaling contributing to breast cancer progression

The transition from ductal carcinoma in situ (DCIS) to invasive breast cancer (IBC) is a crucial step in breast cancer progression. The specific alterations that govern this transition have not been elucidated. HER2/neu is frequently overexpressed in DCIS but is less common in IBC, thereby suggesting additional requirements for transformation. To identify genes capable of cooperating with HER2/neu to fully transform mammary epithelial cells, we used an insertional mutagenesis screen on cells isolated from wild-type neu expressing mice and identified the E3 ligase HACE1 as HER2 cooperative tumor suppressor gene. Loss of HACE1 expression is commonly seen in clinical breast cancer data sets. HACE1 downregulation in normal human mammary epithelial cells (HMECs) results in the accumulation of the activated GTP-bound Rac1 partially transforming these cells. Overexpression of HER2 activates Rac1, which further accumulates upon HACE1 loss resulting in Rac1 hyperactivation. Although the knockdown of HACE1 or overexpression of HER2 alone in HMECs is not sufficient for tumorigenesis, HER2 overexpression combined with HACE1 downregulation fully transforms HMECs resulting in robust tumor formation. The pharmaceutical interference of Rac function abrogates the effects of HACE1 loss both in vitro and in vivo, resulting in marked reduction in tumor burden. Our work supports a critical role for HACE1 in breast cancer progression and identifies patients that may benefit from Rac-targeted therapies.

Maastricht Delphi consensus on event definitions for classification of recurrence in breast cancer research

BACKGROUND

In breast cancer studies, many different endpoints are used. Definitions are often not provided or vary between studies. For instance, "local recurrence" may include different components in similar studies. This limits transparency and comparability of results. This project aimed to reach consensus on the definitions of local event, second primary breast cancer, regional and distant event for breast cancer studies.

METHODS

The RAND-UCLA Appropriateness method (modified Delphi method) was used. A Consensus Group of international breast cancer experts was formed, including representatives of all involved clinical disciplines. Consensus was reached in two rounds of online questionnaires and one meeting.

RESULTS

Twenty-four international breast cancer experts participated. Consensus was reached on 134 items in four categories. Local event is defined as any epithelial breast cancer or ductal carcinoma in situ (DCIS) in the ipsilateral breast, or skin and subcutaneous tissue on the ipsilateral thoracic wall. Second primary breast cancer is defined as epithelial breast cancer in the contralateral breast. Regional events are breast cancer in ipsilateral lymph nodes. A distant event is breast cancer in any other location. Therefore, this includes metastasis in contralateral lymph nodes and breast cancer involving the sternal bone. If feasible, tissue sampling of a first, solitary, lesion suspected for metastasis is highly recommended.

CONCLUSION

This project resulted in consensus-based event definitions for classification of recurrence in breast cancer research. Future breast cancer research projects should adopt these definitions to increase transparency. This should facilitate comparison of results and conducting reviews as well as meta-analysis.

Abstract P5-04-06: Loss of the E3 ubiquitin ligase HACE1 plays a critical role in transformation of mammary cells and clinical progression of human breast cancer via accumulation of active Rac1

Invasive ductal breast cancer arises when the immediate precursor, ductal carcinoma in situ (DCIS), breaches the basement membrane of the ductal lumen and invades into the surrounding tissue. Although this transition has been implicated as a crucial step in the progression of breast cancer, the specific alterations responsible for this transition have yet to be identified.

HER2/neu, a member of the epidermal growth family receptor (EGFR) family, is frequently overexpressed in non-invasive lesions (50-60%) but is significantly less common in invasive breast cancer (20-30%). This suggests that while HER2/neu may be partially transformative, additional alterations are required for mammary epithelial cells to achieve full malignant transformation.

To identify novel genes capable of cooperating with HER2, we performed an insertional mutagenesis screen for genes whose alteration induces anchorage-independent growth on primary mouse mammary epithelial cells isolated from MMTV-neu transgenic mice. We identified HECT domain and ankyrin repeat containing E3 ubiquitin-protein ligase 1 (HACE1) as a putative breast tumor suppressor gene whose loss contributes to the transformative process.

Loss of HACE1 expression is commonly seen in publicly available breast cancer patient data sets as well as in established breast cancer cell lines supporting the role of HACE1 as a breast cancer tumor suppressor gene. Knockdown of HACE1 in HER2 overexpressing human mammary epithelial cells (HMECs) enhanced colony formation over HER2 overexpressing HMEC controls cells. Moreover, knockdown of HACE1 alone was sufficient to allow anchorage-independent growth in soft agar in the HMECs while the overexpression of HACE1 in breast cancer cell lines diminishes clonogenic capacity in soft agar.

We confirmed recent studies that have shown that HACE1 is capable of tagging the Rho GTPase Rac1 for ubiquitin-mediated proteasomal degradation. In mammary epithelial cells, the loss of HACE1 leads to enhanced levels of active Rac1 resulting in increased clonogenicity, migration and invasion. Importantly, we show that targeting Rac1 can rescue the effects of HACE1 loss in mammary epithelial cells. Our results establish HACE1 as a breast cancer tumor suppressor gene by attenuating active Rac1 signaling. Our work supports the role of Rac1 as a critical signaling node in breast cancer and that loss of HACE1 leads to enhanced Rac1 signaling resulting in driving cancer progression. Furthermore, our results suggest the role of HACE1 loss as a biomarker for tumor progression and may identify patients vulnerable to Rac1 or Rac effector targeted therapies.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-04-06.

CD44 is prognostic for overall survival in the NCI randomized trial on breast conservation with 25 year follow-up

CD44 is a transmembrane glycoprotein involved in numerous cellular functions, including cell adhesion and extracellular matrix interactions. It is known to be functionally diverse, with alternative splice variants increasingly implicated as a marker for tumor-initiating stem cells associated with poor prognosis. Here, we evaluate CD44 as a potential marker of long-term breast cancer outcomes. Tissue specimens from patients treated on the National Cancer Institute 79-C-0111 randomized trial of breast conservation versus mastectomy between 1979 and 1987 were collected, and immunohistochemistry was performed using the standard isoform of CD44. Specimens were correlated with patient characteristics and outcomes. Survival analysis was performed using the log rank test. Fifty-one patients had evaluable tumor sections and available long-term clinical follow up data at a median follow up of 25.7 years. Significant predictors of OS were tumor size (median OFS 25.4 years for ≤2 cm vs. 7.5 years for >2 cm, p = 0.001), nodal status (median OS 17.2 years for node-negative patients vs. 6.7 years for node positive patients, p = 0.017), and CD44 expression (median OS 18.9 years for CD44 positive patients vs. 8.6 years for CD44 negative patients, p = 0.049). There was a trend toward increased PFS for patients with CD44 positive tumors (median PFS 17.9 vs. 4.3 years, p = 0.17), but this did not reach statistical significance. These findings illustrate the potential utility of CD44 as a prognostic marker for early stage breast cancer. Subgroup analysis in patients with lymph node involvement revealed CD44 positivity to be most strongly associated with increased survival, suggesting a potential role of CD44 in decision making for axillary management. As there is increasing interest in CD44 as a therapeutic target in ongoing clinical trials, the results of this study suggest additional investigation regarding the role CD44 in breast cancer is warranted.