Abstract 3982: Targeting of miRNA networks for prevention of basal-like breast cancers

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Abstract Introduction: Approximately 75% of women who develop sporadic breast cancer have no known epidemiological risk factors. This creates a significant challenge for identification of at risk patients for prevention. We hypothesized that detailing the molecular signature of the precancerous state by subtype will provide opportunities to identify biomarkers of subtype specific breast cancer risk and identify pathways that can be targeted for subtype specific prevention. Experimental procedures: Using cell lines that model breast cancer progression and The Cancer Genome Atlas (TCGA) genome-characterization datasets, we have identified common microRNA (miRNA)-gene signatures as potential biomarkers for early detection and targets for prevention of basal/ triple negative breast cancer (TNBC). We have performed next generation RNA and small RNA seq of MCF10A cell line based TNBC progression model (10A P; parental, 10AT1; atypia, DCIS; ductal carcinoma in situ and Ca1d; invasive carcinoma) and used cell proliferation assay, western blotting, and miRNA analysis by QPCR to study the effects of target inhibition. Results: We have identified miRNA-29c as a lead candidate because it satisfied 3 key criteria necessary for subtype-tailored intervention. First, it found it to be expressed at high levels in MCF10A (immortalized normal line), and showed a steady decrease in the TNBC progression model. Second, it strongly inhibited migration of the metastatic TNBC cell line, MDA MB 231. Third, its downstream targets include druggable pathways such as src kinase, GSK-3β, Pan-ErbB TK, EGFR, MEK1/2, PI3K, PI3Kγ and c-met. One particularly interesting candidate is DNMT3A, the DNA methyl transferase, which we show to be inversely correlated to miRNA-29c and up-regulated in the progression from normal to cancer in the TNBC model. The miRNA-29c-DNMT3A connection that we uncovered strongly suggests an epigenetic component to tumorigenesis in basal like breast cancers and thus, we have tested natural occurring HDAC inhibitor and a small molecule drug, sulforaphane and sodium butyrate, for their ability to revert cellular phenotype of MCF 10A.AT1 and DCIS cells and found these compounds inhibit cell proliferation. We have also used small molecule synthetic inhibitors to target miRNA-29c regulated pathways and studied their effect on cell proliferation and target inhibition. In these analyses a small molecule inhibitor of PI3K/AKT, LY294002 effectively inhibited the AKT signaling and cell proliferation in MCF10A.AT1, and MCF10A.DCIS cells. Similarly, MEK inhibitors PD032590 and GSK1120212 inhibited MEK signaling and cell proliferation in both hyperplastic and DCIS cells. Conclusions: Our study suggests that miRNA-29c-network, may play a key role in the development of triple negative of breast cancer and this networks may provide novel opportunities at several levels for prevention of TNBC/ basal like breast cancer. Citation Format: Anjana Bhardwaj, Kazunoshin Tachibana, Nivetha Ganesan, Yinghong Pan, Kimal Rajapakshi, Cristian Coarfa, Preethi H. Gunaratne, Isabelle Bedrosian. Targeting of miRNA networks for prevention of basal-like breast cancers. [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 3982. doi:10.1158/1538-7445.AM2015-3982