IMMUNOHISTOCHEMICAL EXPRESSION OF P53, BCL-2, MDM2 AND WAF1 P21 PROTEINS IN COLORECTAL ADENOCARCINOMAS/

The present study was undertaken to examine the distribution of p53, p 21, mdm-2 and bcl-2 protein expression in human colorectal adenocarcin omas in order to obtain combined information about the immunophenotype s characterising these tumours. Formalin-fixed paraffin-embedded tissu e sections from 52 cases of colorectal adenocarcinomas were stained us ing immunohistochemical methods for the detection of p53, p21/waf1, md m2 and bcl-2 proteins. P53, p21/waf1, mdm2 and bcl-2 proteins were exp ressed in 35/52, 45/52, 9/52 and 27/52 cases, respectively. All nine m dm2 + cases expressed p53 and p21 proteins as well. The three patterns observed in p53/p21 expression were: p53+/p21+, p53+/p21- and p53-/p2 2+ in 28, 7, and 17 cases, respectively. Consequently, p53+/mdm2-/p21, p53+/mdm-/p21- and p53-/mdm2-/p21+ immunophenotypes were expressed i n 19, 7, and 17 cases respectively. Foul patterns of p53/bcl2 expressi on were identified: p53+/bcl2+, 20 cases; p53+/bcl2-, 15 cases; p53-/b cl2+, 7 cases; p53-/bcl2-, 10 cases. It was noteworthy that 9 of the 2 0 p53-/bcl2-tumours had negative lymph node status. The present result s suggest that both p53dependent and p53-independent induction of p21 expression may be involved in the molecular mechanisms controlling the se tumours. High expression of the p53 protein in colorectal carcinoma s could be due not only to p53 gene mutations but also to binding to m dm2 protein which leads to p53 protein stabilisation. In addition, tum ours with p53-/bcl2- immunophenotype are frequently associated to nega tive lymph node status and seem to be less aggressive.