p53 expression and K-ras mutation in colorectal adenomas.

The frequency of p53 overexpression and K-ras codon 12 mutation was investigated in a series of colorectal adenomas. p53 was detected by immunohistochemistry in only 5% of tumours, whereas K-ras mutation was found in eight of 30 adenomas examined. In vitro, mutant p53 and ras genes cooperate to transform primary rat cells into a tumourigenic cell line. The presence of both p53 overexpression and K-ras mutation in a benign tubulovillous polyp in the present series suggests that in vivo this combination of events is insufficient to cause malignant transformation of a large bowel adenoma.