Bax protein expression in DCIS of the breast in relation to invasive ductal carcinoma and other molecular markers

This study describes the incidence of Bax protein expression in a series of 106 cases of breast cancer including 56 cases of ductal carcinoma in situ (DCIS) and 50 cases of invasive ductal carcinoma (IDC). Relationships of Bax expression to the histological grades of DCIS & IDC, and to the expression of Ki67, ER, p53, cerbB2 & Bcl2 are described. The expression of Bax, Ki67, ER, p53, cerbB2 and Bcl2 proteins is determined immunohistochemically. Cases were regarded positive for Bax, Bcl2 and cerbB2 when they showed either moderate or strong staining for these markers. The nuclear stains (Ki67, ER, and p53) were quantified in terms of percentage positive cells and cases for ER and p53 were considered positive when more than 10% cells were labelled. DCIS were graded histologically as well (n=18), intermediately (n=18), and poorly differentiated (n=20) Invasive ductal carcinoma was graded as grade I (well-differentiated) n=7, grade II (intermediate) n=24 and grade III (poorly differentiated) n=19. 65/106 cases (61%) were Bax positive including 37/56 (66%) of DCIS and 28/50 (56%) of IDC. Bax expression did not correlate to increasing histological grades of either DCIS or IDC. It did not correlate to Ki67, ER, p53 or cerbB2 but positive correlation was seen with Bcl2 (p=0.003). Bcl2 immunostaining displayed a negative correlation with increasing histological grades both of DCIS and IDC (p=0.026), (p=0.041) respectively. There was a trend of negative correlation of Bcl2 with Ki67 (p=0.062). It correlated positively with Bax (p=0.003) and ER (p<0.0001). Results suggest that the regulation of apoptosis is important in ductal carcinoma in situ of the breast as well as invasive ductal carcinomas. Bcl2 is associated with good prognostic markers in both DCIS and IDC, whereas the regulation of Bax is complex and does not necessarily correlate with mutant p53.