Abstract IA17: The global phospho-proteome of K-Ras mutant cells and tissues

Abstract

Abstract K-Ras is the most commonly mutated oncogene in cancer and it plays a predominant role in the pathogenesis of cancers of the pancreas, colon, and lung. Mutationally activated K-Ras influences cellular behaviors through broad and complex effects on downstream signal transduction pathways. In an effort to understand the molecular mechanisms underlying the oncogenic properties of mutant forms of K-Ras, we are using mass spectroscopy (MS) to quantify proteome-wide changes in protein phosphorylation in primary mouse tissues that are engineered to express mutant forms of K-Ras. In total, we have obtained relative quantification of 5,936 and 11,455 phospho-peptides from mouse pancreas and colon of varying K-Ras genotype. The dataset paints a complex picture of signaling downstream of K-Ras, as phosphorylation of many proteins in known Ras effector pathways (i.e. MAPK and PI3K) are unaffected or down-regulated by mutationally activated K-Ras. Moreover, we have found that different activating K-Ras alleles often have polar effects on the phosphorylation state of a given downstream protein. The biological significance of any given phosphorylation change in a large dataset such as this is often difficult to interpret, since the vast majority of quantified sites have no functional annotation. To combat this issue, we developed phospho-site set enrichment analysis (PSSEA), a computational tool that identifies kinases that are activated in a given sample based on the representation of known substrates in the phospho-MS dataset. PSSEA revealed, for example, that casein kinase 2 (Csnk2a1) is selectively activated by K-RasG12D in the pancreas, but not in the colon. Overall, this study provides an unprecedented view of K-Ras signaling on a global scale and reveals a variety of novel insights into the signal transduction properties of different K-Ras alleles. Ultimately, systems-level and bioinformatic analyses of these data will reveal new therapeutic targets for cancers expressing mutant forms of K-Ras. Citation Format: Kevin Haigis.{Authors}. The global phospho-proteome of K-Ras mutant cells and tissues. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Advances in Science and Clinical Care; 2016 May 12-15; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(24 Suppl):Abstract nr IA17.