Abstract 2605: Selective targeting of KRAS mutant cancer cells by a novel small molecule compound
Authors: Iskandar Kartini , Rezlan Majidah , Yadav Sanjiv K. , Pervaiz Shazib 
Published: May 2015

We report here the molecular mechanism(s) underlying the anti-tumor activity of the novel small molecule, C1, which was previously shown by our group to trigger autophagy-associated apoptosis via a ROS-dependent manner in a variety of human cancer cell lines and primary cells derived from patients. Our results indicate the paradoxical involvement of mutant K-RAS as a specific target of this drug and its highly selective preference for cells with a mutant KRAS phenotype; HCT116 colorectal carcinoma cells that harbor an inherent mutated KRAS allele (V13D) are significantly more sensitive to this drug than HT29 cells that express wild type RAS. Exposure of HCT116 cells to C1 resulted in activation of KRAS which in turn activated downstream crucial effector, AKT. Interestingly, activated AKT was responsible for downstream ROS production, which sensitized HCT116 cells to cell death. Corroborating the upstream involvement of KRAS in the anti-tumor activity of C1, transient gene silencing of KRAS abrogated ROS generation and death inducing activity of C1 in HCT116 cells. In contrast, activation of KRAS and AKT as well as downstream ROS production were absent in HT29 cells. To confirm the specificity of C1 for KRAS mutant cells, we evaluated the effect of the small molecule compound on RWPE-1 prostate epithelial cells transformed with mutant KRAS. Interestingly, exposure to C1 resulted in a significant reduction in colony forming ability in mutant KRAS prostate cells (RWPE-1-KRAS), compared to the control RWPE-1-Vector cells. Importantly, ROS generation was also significantly higher in RWPE-1-KRAS cells than the RWPE-1-Vector cells. To provide further evidence for the specific involvment of mutant RAS signaling in the anti-cancer activity of C1, we made use of HCT116 mutant KRAS knock-out cells (KO), which have its mutant KRAS allele deleted and carries a single wild-type KRAS allele and phenotype. Notably, C1 could not trigger mitochondrial ROS production in KO cells. Furthermore, our results show that C1 could trigger KRAS-dependent Bax translocation effectively in HCT116 cells as well as RWPE-1 KRAS cell lines. We postulate that this novel small molecule compound exploits the vulnerabilities of KRAS mutant cells by targeting directly on the active KRAS, further activating it and impacting its downstream effectors, AKT in particular, with the resultant increase in intracellular ROS and execution of Bax translocation that signal for death. Taken together, these data could have tremendous therapeutic implications given the paucity of chemotherapeutic strategies specifically targeting cancers with mutated KRAS.

Citation Format: Kartini Iskandar, Majidah Rezlan, Sanjiv K. Yadav, Shazib Pervaiz. Selective targeting of KRAS mutant cancer cells by a novel small molecule compound. [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 2605. doi:10.1158/1538-7445.AM2014-2605