Abstract 2914: Biphenylene and bipyridine connected benzofuran compounds as novel regulators of kRAS transcription

Abstract

Pancreatic cancer is the fourth most deadly cancer with 5 year survival rate of ∼6%. One of the major attributes of pancreatic cancer is kRAS mutations. kRAS is a proto-oncogene with intrinsic GTPase activity, and is responsible for cell proliferation, division, and apoptosis. kRAS mutations are observed in >95% of pancreatic adenocarcinoma and in 30% all human tumors. When mutated it leads to continuous activity and uncontrolled proliferation which results in increased tumorigenicity and poor prognosis. Downregulating kRAS expression has shown to halt proliferation and leads to cellular death in pancreatic cancer models, but to date no small molecule capable of such transcriptional silencing has been described. A novel series of molecules with either biphenylene or bipyridine spacer connecting the terminal benzofuran ring was synthesized using solution phase chemistry. Tertiary amine side chains were incorporated to the C2-position of the benzofuran ring to improve the DNA binding affinity of these compounds. The synthesized compounds were purified using a “catch and release” method employing the sulfonic acid based resins. The eleven novel compounds were screened in parallel for their ability to stabilize G-quadruplex structures in the kRAS promoter, and to downregulate kRAS promoter activity. Two of the compounds increased the thermal profile of non-canonical DNA formations in the promoter region by >5 °C; however, on the whole these compounds did not seem to function as G-quadruplex-stabilizing agents. Eight compounds significantly decreased luciferase expression under the explicit control of the kRAS promoter by up to 75%, by compound BF 4.3, through an as-yet unknown mechanism of action. The compound series was examined for the inhibition of cellular viability in two mutant kRAS pancreatic cancer cell lines - Panc-1 and MIA PaCa-2; in both cell lines the compounds containing the bipyridine spacer had greater cytotoxic effects with IC50's of ∼30 μM, consistently. qPCR is being used to confirm the decrease in promoter activity in native cellular conditions. These agents are intriguing in both their novel scaffold and their unexpected activity decreasing kRAS expression in a mechanism unrelated to higher order DNA structures. Ultimately, down regulation of kRAS transcription will provide a novel therapeutic approach for pancreatic cancer and improve the prognosis of this highly lethal disease. Citation Format: Harshul Batra, Mohammad K. Islam, David E. Thurston, Khondaker M. Rahman, Tracy A. Brooks. Biphenylene and bipyridine connected benzofuran compounds as novel regulators of kRAS transcription. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2914.