Apoptosis and Bcl-2 expression in relation to age, tumor characteristics and prognosis in breast cancer

Abstract

The extent of apoptosis and the expression of Bcl-2 was investigated in tumor samples from 165 women who underwent surgery for primary breast carcinoma between 1989 and 1990 in South-East Sweden. Apoptosis was assessed by a DNA fragmentation assay for flow cytometry. Bcl-2 protein expression was analyzed with immunocytochemistry. Bcl-2 immunoreactivity correlated with estrogen receptor (ER) and progesterone receptor (PgR) positivity and was inversely correlated with p53 accumulation. Apoptosis increased with patient age and a high degree of apoptosis was negatively associated with Bcl-2 immunostaining. Apoptosis showed no significant correlation with any of the other variables studied, including prognosis. The group with Bcl-2-positive tumors tended to have a lower risk of distant recuurrence than others, but the association of Bcl-2 with recurrence was different in groups divided by ER and PgR status. Whereas Bcl-2 positivity indicated a low recurrence rate among PgR-negative patients, in the PgR-positive group, those with Bcl-2-positive tumors showed a non significantly higher recurrence rate than Bcl-2-negative cases. In the PgR-positive group, Bcl-2-positive tumors also appeared more frequently to be the lymph node positive and DNA aneuploid. The results suggest that hormone receptor status is one of importance for the prognostic role of Bcl-2. Likewise, patient age merits consideration when apoptosis is studied in human cancer.