Abstract 257: Targeted inhibition of mutant k-ras by siRNA in pancreatic cancer cells results in increased sensitivity to anti-EGFR therapy

Abstract

Abstract Cancer patients are frequently resistant to anti-epidermal growth factor receptor (EGFR) therapy due to secondary mutations in k-ras. This is particularly true for pancreatic cancer patients where the frequency of k-ras mutations is exceptionally high. A variety of therapeutic strategies to target RAS effector pathways have been pursued with limited success. We report here on the use of small interfering RNA (siRNA) to silence oncogenic k-ras in a pancreatic cancer cell line with the goal of sensitizing the cells to anti-EGFR chemotherapies. The AsPC-1 pancreatic cancer cell line expresses EGFR and is homozygous for the mutant k-ras GAT (GGT to GAT in codon 12) allele resulting in the constitutive activation of downstream pathways and reduced apoptotic function. We independently transfected (lipofectamine 2000) AsPC-1 with two siRNAs, one targeted to the mutant (si-k-ras GAT) and one to the wild type (si-k-ras GGT) alleles. We found that levels of k-ras expression (RT-PCR) were significantly reduced after si-k-ras GAT transfection but not after si-k-ras GGT transfection indicating target specificity against the mutant allele. As a preliminary test of the potential clinical utility of si-k-ras GAT mediated inhibition, we measured the relative viability (Tox-8 assay) of AsPC-1 cells transfected with si-k-ras GAT and the EGFR inhibitors Gemcitabine and Erbitux. The results demonstrate a significant increase in sensitivity to both drugs in cells transfected with si-k-ras GAT. We conclude that siRNA mediated inhibition of mutant k-ras may be a promising method by which to sensitize pancreatic cancer cells to anti-EGFR therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 257. doi:10.1158/1538-7445.AM2011-257