Abstract A15: DNA damage response-targeted molecules for breast cancer therapy

Abstract

Abstract Breast cancer genes 1 and 2 (BRACA1 and BRACA2) are known to be linked to breast cancer risk. BRCA1 is an ATM substrate and plays critical roles in the DNA damage response (DDR) and maintenance of genomic stability. Furthermore, recent studies have shown that the aberrant expression of DNA damage repair transducer, ataxia-telangiectasia mutated (ATM), is associated with breast cancers. To develop target-specific drugs, we rationally designed a dual-function small molecule, SP-1-303, by conferring ATM activation and HDAC inhibition activity. The compound was screened against a panel of Class I and Class II HDAC enzymes in vitro and identified as a pan-HDAC inhibitor at an IC50 of 120 nM. Western analysis revealed that SP-1-303 increased acetylated histone H3/H4, α-tubulin, and ATM activation (p-ATM/S1987). Testing two ER-positive BC cell lines (MCF7 and T-47D), two triple-negative breast cancer (TNBC) cell lines (MDA-MB-231 and HCC 1937), and one normal breast epithelial cell line as a control (MCF10A), the effect of SP-1-303 on cell growth was examined by cytotoxicity assays. SP-1-303 demonstrated cytotoxicity (IC50) of ER-positive BC cells in a range of 0.2-0.3 μM, while the values for TNBC cells are in a range of 1-3 μM and 12 μM for normal breast epithelial cells, respectively. Furthermore, proteomic analysis of MCF7 cells following SP-1-303 treatment identified differential effects on expression of various DDR molecules and chromatin regulators, including ATM, BRCA1, TP53BP1, NBN, histones, and chromatin remodelers. Taken together, SP-1-303 shows specificity for ER-positive breast cancers, potentially by modulating the DDR signaling pathway. Citation Format: Alfredo Valenea, Scott Grindrod, Mira Jung. DNA damage response-targeted molecules for breast cancer therapy [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr A15.