Cellular kinetics and expression of bcl-2 and p53 in ductal carcinoma of the breast

In this study, the expression of p53 (wild-type and mutated form) and bcl-2 in ductal carcinoma im situ (DCIS) and infiltrating ductal carcinoma (IDC) of the breast was evaluated by immunohistochemistry and PCR-SSCP and corre lated with cellular kinetic parameters, i.e., mitotic index (MI) and apopto tic index (AI). The results showed a significant inverse correlation betwee n p53 and bcl-2 expression in all cases of DCIS and IDC. In the DCIS group, two subgroups with different kinetic characteristics were identified. The first group was characterized by p53 positivity, bcl-2 negativity and high values of MI and AI; the other group was characterized by p53 negativity, b cl-2 positivity and low values of MI and AI. Conversely, in IDC some cases were p53 negative, bcl-2 positive and with high values of AI and MI, other cases were p53 positive, bcl-2 negative and with low AI and MI. Molecular b iological analysis showed that p53 was wild-type in DCIS, while it was in t he mutated form in IDC. These results suggest that in IDC mutated p53 contr ibutes to a change in cellular kinetics and the selection of genetically ab errant cells, thereby favouring neoplastic progression. The coexistence of bcl-2 positivity and high AI could be explained by the presence of 'pathway s' of apoptosis that work independently of bcl-2.