RETINOBLASTOMA AND P53 PROTEIN EXPRESSION IN SPORADIC COLORECTAL CANCERS

Aims: To ascertain if a relationship between retinoblastoma (pRb) and p53 proteins exists in sporadic colorectal carcinomas. Methods: Fifty consecutive colectomy specimens for colorectal cancer in patients over the age of 50 and with no family history of cancers in the bowel were examined for immunoexpression of pRb and p53 proteins. These findings were then related to clinicopathological findings. Commercially avail able monoclonal antibodies to pRb and p53 were used on formalin-fixed, paraffin-embedded tissue. Results: The most intense pRb immunoexpress ion was detected in well-differentiated, low-stage cancers. On the oth er hand, p53 expression was most intense in poorly differentiated, adv anced-stage carcinomas. No statistically significant associations were noted with immunoexpression and age, gender or site of lesion. Conclu sions: This study indicates that there is an inverse relationship betw een pRb and p53 protein expression in a proportion of sporadic colorec tal cancers. Twelve tumours which showed low levels of pRb showed high levels of p53 protein. Similarly, seven tumours with high pRb levels displayed low p53 expression. In terms of immunohistochemical profile, p53-high/pRb-low tumours tended to be poorly differentiated and have advanced stage cancer.