Abstract 28: Chemoprevention strategies to target abnormal imprinting in high-risk African American women who do or do not carry a BRCA1 mutation

Background: Genomic imprinting is an inherited form of parent-of-origin-specific epigenetic gene regulation that is dysregulated by poor prenatal nutrition and environmental toxins. KCNK9 encodes TASK3, a pH-regulated potassium channel membrane protein that is overexpressed in 40% of breast cancer. KCNK9 gene amplification accounts for increased expression in Methods/Results: Here we show that KCNK9 has imprinted expression in breast tissue and provide the first identification of the KCNK9 DMR and DMR-associated open chromatin. Our studies show that loss of KCNK9 regulatory methylation and imprinted expression occurs in 75% of triple-negative breast cancer (TNBC) and loss of methylation occurs in non-cancerous tissue from high-risk women. Functional studies show that TASK3 protein regulates mitochondrial membrane potential and apoptosis-sensitivity. In live TNBC cells and non-cancerous mammary epithelial cells from high-risk women, loss of KCNK9 DMR methylation predicts increased mitochondrial membrane potential (p=0.007). African American women have a significantly higher frequency of loss of KCNK9 imprinting than do risk-matched Caucasian women (p=0.005). African American women with BRCA1 mutation have the highest frequency of loss (p Clinical Prevention: This is the first identification of the KCNK9 DMR and demonstration that loss of methylation and overexpression of TASK3 increases mitochondrial membrane potential and promotes apoptosis resistance. Low-toxicity inhibitors of TASK3 are in clinical use and can be readily re-purposed to provide cost effective chemoprevention. These inhibitors include K+ inhibitors (developed for cardiac indications) and Schwann Pepper. Our studies identify TASK3 as a “drugable”, low-toxicity target that can be readily employed as a novel target for prevention and treatment of TNBC, particularly in high-risk African American women. Citation Format: Victoria Seewaldt, David Skaar, Eric Dietze, Shraddha Desai, Randy Jirtle. Chemoprevention strategies to target abnormal imprinting in high-risk African American women who do or do not carry a BRCA1 mutation. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Susceptibility and Cancer Susceptibility Syndromes; Jan 29-Feb 1, 2014; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(23 Suppl):Abstract nr 28. doi:10.1158/1538-7445.CANSUSC14-28