KRAS and colorectal cancer: The genetic contribution in the formation of adenomas, as well as progression to malignancy, include: Mutation in proto-oncogenes (K-ras) Inactivation of tumor suppressor gene: Stepwise progression of the tumor is associated with inactivation of tumor suppressor gene designated DCC (deleted in colorectal cancer) on chromosome 18q- (responsible for normal cell-cell adhesive interactions) in more than 75% of cases, i.e., 18q deletion is the most common cytogenetic abnormality.