V-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog also known as KRAS is a protein which in humans is encoded by the KRAS gene. KRAS has been extensively studied in a wide array of human malignancies, including mCRC. Mutant KRAS can be detected in approximately 30-50% of colorectal cancers. The Ras-Raf-MAPK pathway lies just downstream of EGFR.