Potential role of bcl-2 expression and apoptotic body index in colorectal cancer

Tumor growth is the result of proliferation and apoptosis. Bcl-2 is a proto-oncogene that inhibits apoptosis. The aim of the study was to investigate the clinicopathological correlations, interactions and prognostic significance of both bcl-2 protein expression and apoptotic body index (ABI) in colorectal cancer (CRCs).

Sixty colorectal cancer (CRC) patients had colonoscopic biopsies and tumor markers assay (CEA-CA19.9). The resected specimens were subjected for routine pathologic assessment, immunocytochemical staining for bcl-2 protein detection and immunofluorescence method for apoptotic body index.

Bcl-2 immunostaining (IS) was positive in 29 patients (48.3%). The bcl-2 positive IS was significantly associated with -ve vascular invasion (P=0.05) and early tumor staging (P<0.01); the apoptotic body index had a median 3.5% and is neither correlated with bcl-2 or the clinicopathological variables. The overall survival (OS) was significantly associated with ABI (P<0.01), but not with bcl-2 expression and on bi-variant analysis, the OS is significantly better with high ABI in bcl-2 positive immunophenotype (P<0.05).

Bcl-2 is a marker of favorable parameters (-ve angioinvasion and early tumor staging) but of no prognostic value. The apoptotic body index (ABI) is a favorable prognostic factor and may be used as a stratification parameter especially the high ABI in bcl-2 +ve CRCs.