Dysregulation of normal programmed cell death mechanisms plays an important role in the pathogenesis of breast cancer. The purpose of this study was to investigate the role of bax and p53 expression in tumorigenesis and progression of breast carcinoma as well as their relationship with proliferative and apoptotic activity. We used immunohistochemical methods and in situ detection of apoptotic cells to examine 30 carcinomas in situ (CIS), 131 invasive breast carcinomas and 45 lymph node metastases. In 25% (33 of 131) of invasive breast carcinomas examined, bax expression was absent, while p53 accumulation was present in 37% (49 of 131). Interestingly, p53 accumulation and loss of bax expression occur in breast CIS as frequently as in invasive breast carcinoma. Thus, in 17% (5 of 30) of CIS bax expression was absent, and 30% (9 of 30) presented nuclear expression of p53. p53 accumulation was related to apoptosis and proliferative activity. However, the protein level of bax was unrelated to all parameters studied, including proliferation and apoptosis of tumor cells. A multivariate analysis of disease-free survival demonstrated that p53 accumulation and bax expression are not significant independent indicators of prognosis in operable breast carcinoma. Our results also show that the proportion of bax- and p53-positive cells does not vary between primary and metastatic tumors. p53 accumulation and loss of bax expression influence the acquisition of a malignant phenotype but seem to have no further impact on tumor progression.
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