The majority of breast cancer specific deaths in women with estrogen receptor positive (ER+) tumors occur due to metastases that are resistant to therapy. There is a critical need for novel therapeutic approaches to achieve tumor regression and/or maintain therapy responsiveness in metastatic ER+ tumors. The objective of this study was to elucidate the role of metabolic pathways that undermine therapy efficacy in ER+ breast cancers. Our previous studies identified Exportin 1 (XPO1), a nuclear export protein, as an important player in endocrine resistance progression and showed that combining selinexor (SEL), an FDA-approved XPO1 antagonist, synergized with endocrine agents and provided sustained tumor regression. In the current study, using a combination of transcriptomics, metabolomics and metabolic flux experiments, we identified certain mitochondrial pathways to be upregulated during endocrine resistance. When endocrine resistant cells were treated with single agents in media conditions that mimic a nutrient deprived tumor microenvironment, their glutamine dependence for continuation of mitochondrial respiration increased. The effect of glutamine was dependent on conversion of the glutamine to glutamate, and generation of NAD+. PGC1α, a key regulator of metabolism, was the main driver of the rewired metabolic phenotype. Remodeling metabolic pathways to regenerate new vulnerabilities in endocrine resistant breast tumors is novel, and our findings reveal a critical role that ERα-XPO1 crosstalk plays in reducing cancer recurrences. Combining SEL with current therapies used in clinical management of ER+ metastatic breast cancer shows promise for treating and keeping these cancers responsive to therapies in already metastasized patients.

Man c ip Click he e o acce /do nload;Man c ip ;Cance find HOCA R1 4.doc Click he e o ie linked Refe ence identification of breast cancer risk and hence decreased mortality. Our findings provide the knowledge basis needed to proceed in this direction.

African American (AA) women in the United States have a 40% higher breast cancer mortality rate than Non-Hispanic White (NHW) women. The survival disparity is particularly striking among (estrogen receptor positive) ER+ breast cancer cases. The purpose of this study is to examine whether there are racial differences in metabolic pathways typically activated in patients with ER+ breast cancer. We collected pretreatment plasma from AA and NHW ER+ breast cancer cases (AA n = 48, NHW n = 54) and cancer-free controls (AA n = 100, NHW n = 48) to conduct an untargeted metabolomics analysis using gas chromatography mass spectrometry (GC–MS) to identify metabolites that may be altered in the different racial groups. Unpaired t-test combined with multiple feature selection and prediction models were employed to identify race-specific altered metabolic signatures. This was followed by the identification of altered metabolic pathways with a focus in AA patients with breast cancer. The clinical relevance of the identified pathways was further examined in PanCancer Atlas breast cancer data set from The Cancer Genome Atlas Program (TCGA). We identified differential metabolic signatures between NHW and AA patients. In AA patients, we observed decreased circulating levels of amino acids compared to healthy controls, while fatty acids were significantly higher in NHW patients. By mapping these metabolites to potential epigenetic regulatory mechanisms, this study identified significant associations with regulators of metabolism such as methionine adenosyltransferase 1A (MAT1A), DNA Methyltransferases and Histone methyltransferases for AA individuals, and Fatty acid Synthase (FASN) and Monoacylglycerol lipase (MGL) for NHW individuals. Specific gene Negative Elongation Factor Complex E (NELFE) with histone methyltransferase activity, was associated with poor survival exclusively for AA individuals. We employed a comprehensive and novel approach that integrates multiple machine learning and statistical methods, coupled with human functional pathway analyses. The metabolic profile of plasma samples identified may help elucidate underlying molecular drivers of disproportionately aggressive ER+ tumor biology in AA women. It may ultimately lead to the identification of novel therapeutic targets. To our knowledge, this is a novel finding that describes a link between metabolic alterations and epigenetic regulation in AA breast cancer and underscores the need for detailed investigations into the biological underpinnings of breast cancer health disparities.

Introduction Racial disparities in breast cancer (BrCa) mortality are well documented. We previously reported that African American (AA) women with estrogen receptor-positive (ER+) BrCa have a 4-fold higher rate of death compared to non-Hispanic whites (white) after controlling for stage at diagnosis and treatment initiation. This suggests that racial differences in tumor biology may contribute to the survival disparity. In preliminary work we found that AA BrCa cases have higher serum levels of C-reactive protein (CRP) compared to whites, and that increased CRP was associated with worse survival, suggesting that increased systemic inflammation in AA women drives aggressive tumor biology and contributes to the racial disparity in survival. The goal of this study is to identify specific inflammatory pathways that may be involved. Experimental Procedures Pre-treatment blood samples from women with stage I-III ER+ BrCa (AA, n=40; white, n=55) and from healthy controls (AA, n=51; white, n=38) were analyzed with the Olink® targeted proteomic assay, which measures 92 inflammatory proteins. Normalized data was log2 transformed, and generalized linear models compared the normalized intensities with covariates of interest. The fit of the model was tested with empirical Bayes methods. All p-values are corrected for multiple testing with the false discovery rate (FDR) method of Benjamini and Hochberg. Findings After adjustment for site of enrollment, plasma levels of 13 inflammatory cytokines showed a log2 fold-change (log2FC) ≥ 1.0 for AA compared to white women, i.e. at least a two-fold increase in the mean value on a linear scale (Table). The racial difference was evident among both cases and controls, and remained after adjusting for body mass index (BMI). There were no differences between AA cases and controls, indicating that cytokine elevation in AA BrCa patients is not an effect of the tumor. Several of the cytokines are known to promote tumor progression and aggressive biological features in breast tumors. ProteinLog2FCProteinLog2FCCXCL52.42**CCL81.13***CXCL12.06***EIF4EBP11.12**STAMBP1.91*CCL201.10**CXCL111.89**TNF141.06*CCL31.45**TGF beta1.04**CXCL61.40**CCL71.03***CCL131.16**FDR corrected p-values: * < 0.05, **< 0.01, ***< 0.001 Conclusion Systemic elevation of biologically relevant inflammatory cytokines in AA women with ER+ BrCa does not appear to be an effect of the tumor. This inflammatory phenotype may activate inflammatory programs in ER+ breast tumors that develop in AA women, leading to disproportionately aggressive tumor biology and worse outcomes. Supported by grants U54CA203000; U54CA2022995; and U54CA2022997 from the National Institutes of Health. Citation Format: Oana C. Danciu, George Chlipala, Zeynep Madak-Erdogan, Hariyali Patel, Landan Banks, Ayesha Zaidi, Ashlie Santaliz-Casiano, Lauren Schulte, Lauren Weller, Deanna Taiym, Natalie Pulliam, Elona Liko Hazizi, Elonia Martin, Anita Fareeduddin, Archana Bargaje, Carlos Garcia, Scott Hegerty, Sarah Friedewald, Seema Khan, J Julie Kim, William Gradishar, Garth Rauscher, Jonna Frasor, Kent F. Hoskins. Racial differences in circulating inflammatory cytokines and breast cancer disparities [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1176.

Introduction: Approximately 70% of human breast cancers express estrogen receptor alpha (ERα), providing a potential for targeted endocrine therapy for patients. Unfortunately, 30-40% of ER+ patients still experience recurrence and metastasis with a 5-year relative overall survival rate of just 24%. The tumor microenvironment (TME) plays a key role in the behavior of cancer cells and their response to endocrine therapies. However, there is a critical need for relevant 3D models of different metastatic sites to use for studying the molecular mechanisms driving resistance in these tumor phenotypes. Methods: We established 3D cell culture systems in novel hydrogels derived from decellularized bone, lung and liver tissues - the major sites of metastasis of ER+ tumors, and compared with standard Matrigel culture. Endocrine responsive (MCF7 and T47D) and resistant (MCF7 and T47D cells with ESR1 Y537S or D538G mutations) breast cancer cell lines were treated with fulvestrant (FUL), tamoxifen (TAM) and palbociclib (PAL). Tumorigenicity was assessed using in vitro cell viability and colony formation assays and in vivo breast cancer cell line xenografts in athymic mice. ERα cistromes and transcriptomes were assessed using ChIP-Seq and RNA-Seq analysis. Metabolic changes were assessed using whole metabolite profiling by GC-MS, a Seahorse XF analyzer, and flux analysis with labeled glucose and glutamine. Results: We observed metastatic site-specific responses to each drug. For example, TAM blocked colony formation in Matrigel and lung hydrogel but increased colony formation in bone and liver hydrogels. FUL acted as an agonist and increased colony number and size in all three-tissue matrices, but not in Matrigel. PAL increased colony size and number in Matrigel and liver hydrogel but not in bone or lung hydrogel. Genome-wide ERα recruitment to chromatin was reduced in liver hydrogels, consistent with decreased clinical response to endocrine agents in patients with liver metastasis. We found that treatment with individual drugs activated novel metabolic pathways to increase survival in different metastatic sites. Using RNA-Seq analysis, we identified increased expression of nuclear export pathway components (XPO1, KPNA2, etc.) in various metastatic sites. Combining an FDA-approved XPO1 small molecule inhibitor, Selinexor (SEL) with the current therapies used for advanced breast cancers (FUL, TAM or PAL) decreased metabolic adaptations in response to individual drug treatments and prevented colony formation in hydrogels and tumor growth in xenograft models. Conclusions: Further developing and characterizing 3D metastatic site models will enable us to elucidate the underlying mechanisms of metastasis and resistance, and target these mechanisms with novel drug combinations in already metastasized patients. Targeting metastatic-site specific adaptations to regenerate new vulnerabilities in endocrine-resistant breast tumors is novel. Given the need for better strategies for improving therapy response of metastatic ER+ tumors, our findings show uncovering the role ERα-XPO1 crosstalk plays in metastatic breast cancer could lead to new combined therapies that reduce mortality. Citation Format: Qianying Zuo, Eylem Kulkoyluoglu Cotul, Ashlie Santaliz-Casiano, Ozan Berk Imir, Elif Tunc, Chengjian Mao, David J. Shapiro, Ben Ho Park, Yosef Landesman, Zeynep Madak-Erdogan. Metastatic organ-specific changes in ERα and XPO1 signaling and metabolic adaptations dictate the therapy responses in endocrine resistant breast cancers [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5675.