Apoptosis in adenoma and early adenocarcinoma of the colon

Twenty-six specimens of tubular adenoma and 7 specimens of adenocarcinoma in adenoma of the colon were examined to evaluate apoptosis between adenoma and early adenocarcinoma. Cell proliferation and cell death seemed to be balanced in adenoma with mild and moderate atypia, but unbalanced in adenoma with severe atypia and cancer. Apoptosis was considered to be suppressed at cancer in some cases. However, a number of apoptosis increased at cancer in other cases. Necrosis was seen only in cancer areas. The ratio of cells simultaneously stained by anti-Ki-67 antibody (MIB-1) and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-nick end labeling (TUNEL) tended to be high from adenoma with moderate atypia to cancer, suggesting the unstableness of DNA. It is possible that cancer cells having highly unstable DNA easily underwent apoptosis as well as necrosis, accidentally. The p53 protein was positive only in cancer areas of three cases. One of these three showed decreased apoptosis in a cancer area, but the other two cases showed increased apoptosis. Furthermore, certain numbers of cancer cells were double-stained by p53 immunohistochemistry and TUNEL. These results suggest that the p53 protein may contribute to suppress apoptosis in the last stage of carcinogenesis of the colonic adenocarcinoma, but other factors including extrinsic stimulation may cause apoptosis despite the mutation of p53 protein.