KRAS and malignant colon neoplasm: Likewise, Trejo-Becerril et al. demonstrated that NIH-3T3 cells exposed to DNA from KRAS mutation-positive patient serum or cell supernatant developed a KRAS mutation over time, and when KRAS-positive cells plus the colon cancer carcinogen 1,2-dimethylhydrazine were injected into rats, the rats developed tumors with detectable KRAS mutations [20].