Project 1: We continued to comprehensively examine the metabolome, proteome and transcriptome of ER-positive and ER-negative breast tumors from African-American and European-American patients for biomarker discovery. The promise of the study is the discovery of novel biomarkers for prognosis, and for elucidating what may drive the aggressiveness of breast cancer in African-American women. Using an untargeted discovery approach and validation of key metabolites, we characterized the metabolomic profile of human breast tumors and uncovered intrinsic metabolite signatures in these tumors. Importantly, the oncometabolite, 2-hydroxyglutarate (2HG), accumulated in a subset of tumors and human breast cancer cell lines. 2HG reached mmolar concentrations comparable to those in isocitrate dehydrogenase (IDH)-mutant gliomas, despite the absence of IDH mutations. Instead, we discovered a significant association between increased 2HG levels and MYC pathway activation in breast cancer, which was corroborated in human mammary epithelial and breast cancer cells with inducible MYC overexpression and knockdown. Further analyses showed a global increase of DNA methylation in 2HG-high tumors and identified a poor survival tumor subtype with distinct DNA methylation, high tissue 2HG, and heightened occurrence in African-American patients. Tumors of this subtype had a stem cell-like transcriptional signature with WNT and MYC pathway activation. These tumors over-expressed glutaminase, suggesting a functional relationship between glutamine and 2HG metabolism in breast cancer. Accordingly, 13C-labeled glutamine was metabolized into 2HG in cells with aberrant 2HG accumulation, whereas pharmacologic and siRNA-mediated inhibition of glutaminase markedly reduced 2HG. Our findings highlight 2HG as a candidate breast cancer oncometabolite associated with MYC activation and poor prognosis. These studies are being continued, and we are currently evaluating the oncogenic effects of 2HG and how they relate to the expression of ADHFE1, a mitochondrial enzyme that produces 2HG. Current data show that 2HG is a breast cancer oncometabolite that increases stem cell-like and metastatic features of human breast cancer cells while overexpression of ADHFE1 induces the same phenotypes and enhances reductive carboxylation in cancer cells, leading to increased 2HG. In a different study, focusing on the breast cancer proteome, we performed an integrated proteotranscriptomic characterization of breast tumors. We measured global proteome and transcriptome expression in 118 human breast tumors and adjacent non-cancerous tissues. Comparing proteome with transcriptome data, we found that the proteome describes differences between cancerous and non-cancerous tissue that are not captured by the transcriptome. Moreover, the proteome and transcriptome highlighted partially different tumor biologies. When we applied an integrated analysis of both technologies, the approach revealed a global increase in protein-mRNA concordance in tumors. Highly correlated protein-gene pairs were enriched in protein processing and disease metabolic pathways, and occurred more commonly in tumors of African-American patients. The increased concordance between transcript and protein levels was further associated with aggressive disease, including basal-like/triple-negative tumors, and decreased patient survival. Our study indicates that an integrated analysis of the proteome and transcriptome in cancer can uncover disease characteristics beyond the ability of a single technology. Project 2: Inflammation is widely recognized as an inducer of cancer progression. Inducible nitric oxide synthase (NOS2), cyclooxygenase-2 and cystathionine beta synthase are inflammation markers and are involved in wound healing, angiogenesis, and carcinogenesis. NOS2 up-regulation and increased nitric oxide (NO) production also affects the redox state of cells and induces protein, lipid, and DNA modifications. Recent research by our laboratory led to the novel and clinically significant observation that NOS2 expression is associated with a prognostic basal-like transcription pattern and is an independent predictor of poor survival in women with ER-negative breast tumors. These findings are further pursued in collaboration with the laboratory of Dr. David Wink at the NCI. This collaboration showed that up-regulation of NOS2 in ER-negative breast cancer cells occurs in response to hypoxia, serum withdrawal, IFN-gamma, and exogenous NO, consistent with a feed-forward regulation of NO production by the tumor microenvironment in breast cancer biology. Moreover, we found that key indicators of an aggressive cancer phenotype including increased S100 calcium binding protein A8, IL-6, IL-8, and tissue inhibitor matrix metalloproteinase-1 are up-regulated by these NOS2-induced stimulants, whereas inhibition of NOS2 in MDA-MB-231 breast cancer cells suppressed the same markers. NO also altered cellular migration and chemoresistance of MDA-MB-231 cells to Taxol and other chemotherapeutics. Most notably, MDA-MB-231 tumor xenograft growth and metastases to the brain were significantly suppressed when NOS2 was inhibited in nude mice. These novel results further link elevated NOS2 to cancer progression and show that NO production regulates chemoresistance and metastasis of breast cancer cells. Having made these observations, we recently, started to evaluate the role of cystathionine beta synthase in breast cancer progression. This enzyme, like NOS2, releases a gaseous signal molecule which is hydrogen sulfide. Hydrogen sulfide like NO stimulates angiogenesis and may affect therapy response. Preliminary data show that cystathionine, a product of cystathionine beta synthase (CBS), accumulates in breast tumors. Currently, we are establishing human breast cancer cell lines with low, medium and high expression levels of CBS to examine the dose effect of CBS on tumor xenograft growth and metastasis in mice. We will also examine the effects of CBS on therapy response and cancer metabolism and monitor hydrogen sulfide signaling with novel fluorescent probes for endogenous hydrogen sulfide. Project 3: This project evaluates the role of environmentally-induced stress signaling and co-morbidities in breast cancer progression. We started projects studying the impact of stressful life events and diabetes on tumor biology. In a clinical study, we will give breast cancer patients, who are scheduled for breast cancer surgery, a short survey evaluating their perceived stress and social isolation. We will also collect frozen tumor and adjacent normal breast tissue and blood samples from these patients and evaluate whether the breast tissue or the blood samples have a biological signatures related to their perceived stress and social isolation status. We hypothesize that patients with a high perceived stress exposure have a biological signature consistent with a more aggressive disease and poorer survival. The pilot study is designed to collect 100 tumor/normal pairs from consented patients with a completed survey. In a second study, we are evaluating the relationship between self-reported diabetes and tumor biology and breast cancer aggressiveness. Here, a patient's diabetes status based on survey and medical record data will be correlated with global gene expression and metabolite patterns in their tumors to identify cancer-related pathway that are impacted by diabetes. This study is ongoing and will assess whether type 1 and 2 diabetes induce changes to tumor biology that enhance the odds of disease progression. We are particular interested in changes to metabolic pathways, and how they can be targeted to decrease the negative impact that a diabetes diagnosis may have on breast cancer outcomes.
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