p53 and Bcl-2 (both regulators of cell apoptosis) have been considered to be involved in the initiation and progression of the colorectal tumorigenic process, respectively. In this study, we investigated their association with tumor stage and grade –both substantially affecting prognosis. Immunohistochemical assessment of p53 and Bcl-2 was retrospectively conducted (using DO-7 and Ca-124 monoclonal antibodies, respectively) in 119 surgically resected colorectal carcinomas, and the results were correlated to tumor stage and grade. The proportion of tumors positively stained was 70% for p53 and 46% for Bcl-2, whereas co-expression of both markers was observed in 28% of cases. Tumors exhibiting the highest p53 staining (>60% stained cells) were more frequently found in disease stage IV (p=0.03), while Bcl-2 positivity showed a predilection for earlier stage (p=0.02) and better grade (p=0.028). The associations of both markers with stage, along with a reciprocal relationship between p53(+) and Bcl-2(+) tumors (p=0.02), stronger for cases with p53 staining >30% (p=0.007), remained significant only for distal tumors. The distinct correlations of p53 and Bcl-2 with disease progression and aggressiveness (being influenced by the extent of staining and tumor site) may be clinically useful in the determination of high-risk colorectal cancer cases.

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