Quantitative comparison of apoptosis to cell proliferation and p53 protein in breast carcinomas

To clarify the correlation between apoptosis and tumor cell proliferative activity in human breast cancer and to investigate their relevance to p53 protein.

Seventy-one breast carcinomas with histologic grading were analyzed, using counting of mitotic activity index (MAI) and apoptotic index (AI) to examine apoptosis and cellular proliferation, which were then compared with the expression of p53 protein by using a semiquantitative immunohistochemical method.

Both the mean MAI and AI were significantly higher in the grade 3 groups (18.30 +/- 2.18 SE, 13.58 +/- 1.94) and 2 (11.32 +/- 1.30, 9.96 +/- 1.84) than in the grade 1 groups (8.24 +/- 1.10, 8.30 +/- 2.20) (P < .001). Also, MAI/AI was significantly highest in the grade 3 group (P < .001). A significant correlation was found between MAI and AI (r = .767, P < .01). Positive expression of p53 protein, indicated by distinct nuclear staining, was found in 35 of 71 carcinomas and was related to neither MAI nor AI (P > .05); there was no significant relation between p53-positive scoring and histologic grading (P > .05).

Apoptosis in breast cancer seems to correlate with proliferative activity assessed by the mitotic index and supports the hypothesis that apoptosis may play a role in the selection of clonal subpopulations with high growth potential but is not regulated by the p53 system. Further research needs to be conducted to elucidate the relation between apoptosis and tumor progression and the significance of p53 in abnormalities in breast cancer.