CORRELATION OF CYCLIN D1 AND RB GENE-EXPRESSION WITH APOPTOSIS IN INVASIVE BREAST-CANCER

Background-In vitro studies have shown that amplification and overexpr ession of the cyclin D1 gene can accelerate the progress of cells thro ugh the G(1) phase. Therefore, cyclin D1 may have an apoptosis inhibit ing effect. The retinoblastoma (Rb) gene was shown recently to be an i mportant regulator of apoptosis.Aims-To evaluate whether expression of the cyclin D1 and Rb genes correlated with apoptotic counts in a grou p of 97 invasive breast cancers. Methods-Expression of the cyclin D1 a nd Rb genes was detected by standard immunohistochemistry using paraff in wax embedded sections. Apoptotic cells were counted according to a strict protocol, in 10 fields of vision systematically spread over the most poorly differentiated area of the tumour, at a magnification of x630. Apoptotic cells counts were expressed as apoptotic cells/mm(2). Results-Cyclin D1 overexpression was found in 49% of cases. Loss of Rb expression was found in 44% of cases, and occurred particularly in po orly differentiated tumours. Cyclin D1 and Rb expression showed a posi tive correlation (p = 0.003). Apoptotic counts varied from 1 to 62/mm( 2). There were no significant correlations between cyclin D1 overexpre ssion and apoptotic counts in the total group or in the retinoblastoma protein (pRb) positive tumours. Loss of Rb expression also showed no correlation with apoptotic counts. Conclusions-Cyclin D1 is frequently overexpressed in pRb positive tumours, but no evidence has been found for an anti-apoptotic effect of cyclin D1 overexpression or Rb expres sion in invasive breast cancer.