KRAS and colorectal cancer: In our study, we have used four colorectal cancer cell lines: SW480 cell line, which was established from a primary adenocarcinoma of the colon and which is positive for expression of c-myc, K-ras, H-ras, N-ras, myb, sis, and fos oncogenes and for the p53 protein; SW620 which was derived from a metastasis of the same tumor from which the SW480.