Abstract 2597: Direct inhibition of oncogenic KRAS by hydrocarbon-stapled SOS1 helices

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Activating mutations in KRAS represent the most frequent oncogenic driving force among the RAS homologs K-, N- and H-RAS, and are associated with poor prognosis and chemoresistance. KRAS mutations are present in approximately 30% of tumors, and at even higher frequencies in cancers of the pancreas, lung, thyroid gland, colon, and liver. In pancreatic ductal adenocarcinomas (PDAC), which carries a 5-year survival rate of less than 5%, activating KRAS mutations are present in over 90% of tumors. Moreover, these mutations have been causally linked to the initiation and progression of PDAC. Despite the mechanistic insights into KRAS-mediated oncogenesis, development of high affinity targeted inhibitors remains a formidable challenge. Here, we report the synthesis and application of hydrocarbon-stapled peptides as prototype therapeutics for blocking wild type and mutant KRAS in vitro and in cancer cells. Stabilized Alpha-Helices of SOS1 (SAH-SOS1) were generated by inserting hydrocarbon staples into SOS1 peptide sequence to recapitulate the alpha-helical structure of the native KRAS-interaction domain. SAH-SOS1 peptides, but not negative control analogs, bound to a variety of KRAS constructs with nanomolar affinity, inhibiting nucleotide exchange. This sequence-specific biochemical activity correlated with impairment of KRAS-driven cancer cell viability and signal transduction. These studies provide proof-of-concept for the utility of SAH-SOS1 peptides in dissecting and targeting the oncogenic KRAS pathway in human cancer. Citation Format: Elizaveta Leshchiner, Joseph Bellairs, Gregory H. Bird, Kwadwo Opoku-Nsiah, Marina Godes, Lored D. Walensky. Direct inhibition of oncogenic KRAS by hydrocarbon-stapled SOS1 helices. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2597. doi:10.1158/1538-7445.AM2014-2597