Detection of Phospho-KRAS by Electrophoretic Mobility Change in Human Cell Lines and in Tumor Samples from Nude Mice Grafts

KRAS is the oncogene most frequently mutated in human solid tumors especially in pancreas, colon, small intestine, biliary tract and lung. We have recently demonstrated that oncogenic KRAS needs S181 phosphorylation to fully display its oncogenic features suggesting its inhibition as a therapeutic treatment against KRAS-driven tumors. Due to the importance to detect KRAS phosphorylation in human tumors and the absence of specific antibodies against phosphorylated KRAS, we developed a new protocol based on the Phos-tag SDS methodology to detect this post-translational modification for KRAS. Phos-tag is a molecule that binds specifically to phosphorylated proteins, decreasing their migration speed in SDS-PAGE and allowing its separation from the non-phosphorylated forms.