Potential role of bcl-2 and Ki-67 expression and apoptosis in colorectal carcinoma - A clinicopathologic study

Colorectal cancer is associated with deregulation of apoptotic and proliferative processes. The purpose of this study was to investigate the presence of apoptosis and proliferation in colorectal cancer and evaluate their possible correlation with classic prognostic markers and patients' survival. Tumors from 117 patients, followed for 44 - 142 months, were studied immunohistochemically using the anti-bcl-2 and anti-Ki-67 antibodies. Apoptotic body index (ABI) was assessed by a standard TUNEL method. The bcl-2 protein was detected in 65% of adenocarcinomas with increased expression in low-grade and early-stage tumors. No association was noted between bcl-2 expression and proliferative activity, ABI, or patients' survival. A positive correlation was observed between ABI and proliferation (P < 0.05). Apoptosis was more frequently observed in advanced tumor stage or high-grade neoplasms. Cox analysis revealed that only tumor stage and grade constituted independent prognostic factors. The study suggests that there is a possible deregulation of the mechanisms that control bcl-2 expression in high-grade and advanced-stage colorectal carcinomas. Regulation of apoptosis is a complex phenomenon and other factors, including tumor heterogeneity, may be involved.