Expression of p73 gene, cell proliferation and apoptosis in breast cancer: Immunohistochemical and clinicopathological study.

p73 is a member of p53 tumor suppressor protein family. In spite of similarities of three meaningful domains between p53 and p73, the exact function of p73 protein is not established. To approach the relevance of p73 expression to a pathological parameter in human breast cancer, the apoptotic index (AI) and the mitotic index (MI) were examined for 75 patients with the breast cancer after mastectomies. We found that both of the AI and MI in p73-positive cases were significantly higher compared to the p73-negative cases, suggesting that the p73-positive cases in the breast cancer were in advanced grade. In six cases of breast cancer with distant metastasis, however, the p73 expression was slight and showing low AI but high MI. Advanced breast cancer with distant metastasis seemed to lose the p73 expression and gain the function of evading apoptosis. Altogether, these data demonstrate that p73 expression is well correlated with AI in breast cancer.