bcl-2 expression is reciprocal to p53 and c-myc expression in metastatic human colorectal cancer.

ABSTRACT

Apoptosis (programmed cell death) inhibition may be an important mechanism by which gastrointestinal mucosal cells containing damaged DNA evade normal clearance mechanisms and grow to become invasive tumours. Since bcl-2 is an apoptosis inhibitor, bcl-2 mRNA expression was measured in 21 metastases of colorectal cancer using reverse transcription-polymerase chain reaction analysis. The mean bcl-2 mRNA expression (0.45 U, P < 0.0001) was lower than that of normal mucosal controls (= 1 U). p53 expression was inversely correlated with bcl-2 expression (P = 0.021) in 19 evaluable samples, and in tumours where p53 expression was over twice that of normal colonic mucosal values, bcl-2 mRNA was significantly decreased (mean 0.30, P = 0.0052). c-myc was also inversely correlated with bcl-2 expression (P = 0.025). Decreased bcl-2 expression in metastatic colorectal cancer may be partly due to allelic loss, given the proximity of bcl-2 to the frequently deleted DCC gene on chromosome 18q. However, the inverse correlation to p53/c-myc suggests an active downregulation of bcl-2, possibly following delegation of its apoptosis inhibiting role to other genes.