Reciprocal expression of bcl-2 and p53 oncoproteins in urothelial dysplasia and carcinoma of the urinary bladder

In order to investigate if and when the bcl-2 oncoprotein is activated in bladder tumorigenesis and its relationship with p53 overexpression and patient survival, we studied bcl-2 and p53 expression immunohistochemically in matched normal urothelium, dysplasia and cancer specimens selected by step-sectioning from 54 radically resected bladders for non-metastatic transitional cell carcinoma (TCC). In normal urothelium and mild dysplasia, bcl-2 was restricted to the basal cell compartment, while in moderate and severe dysplasia its expression was detectable also in the upper regions. Excess bcl-2 immunoreactivity was found in 27 (50%) of carcinomas, and a larger proportion of high-grade TCCs showed bcl-2 expression compared with that of low-grade TCCs (P < 0.05). Overexpression of p53 protein showed a increasing trend toward the progression of bladder tumorigenesis (P < 0.01) and a significant reciprocal correlation was found between bcl-2 and p53 expression in either various dysplasias (P < 0.01) or carcinoma (P < 0.05). With the evolution from mild dysplasia to carcinoma in individual cases, loss of bcl-2 expression was more frequently observed in superficial (P < 0.02) or low-grade carcinoma (P < 0.05) than in muscle-invasive or high-grade carcinoma. Furthermore, patients with negative immunostaining for both bcl-2 and p53 in cancer lesions had a significantly more favorable prognosis compared with those with positive immunostaining for the oncoproteins (P < 0.05), although bcl-2 by itself did not predict patient survival. We suggest that aberrant activated bcl-2, which is seen earlier than p53, appears to facilitate bladder tumorigenesis and to enhance tumor aggression in some extent.