p53 expression in colorectal carcinomas and its correlation with clinicopathological parameters

Background: p53 over expression is based on the fact that the mutant form of p53 protein having prolonged half-life can accumulate and be over expressed in nuclei which can easily detected by immunohistochemistry. Objective: To estimate the frequency of p53 protein overexpression in colorectal carcinoma and its correlation with some clinicopathologic parameters. Methods: The overexpression of p53 protein was studied in sixty paraffin-preserved colorectal carcinoma samples using a monoclonal antibody (clone DO-7). The number of cells stained were scored semiquantitatively as (score 0): <5% positive cells, (score 1+): 5 – 25% positive cells,(score 2++): 25 – 75% positive cells, and (score 3+++): >75% positive cells..The correlation between p53 protein over expression and clinicopathological parameters were evaluated using Chi-square analysis. Results: p53 staining was positive in 42 of 60 specimens. Out of these , 10 were weekly (score1+), 16 moderately (score 2++), and 16 intensely(score 3+++) positive for P53 protein overexpression. There was statistically significant correlation between p53 staining and age(< 40 years vs >= 40 years; P- 0.006). Statistically significant correlation was also found between p53 staining and pathological type( mucinous vs non mucinous; p- 0.007) There were no significant correlations between p53 staining and gender (P =0.86 ), site of tumor (right colon vs. left colon and rectum; P=0.69) and stage of the disease (P =0.34 ). Conclusion: As p53 protein overexpression is seen in relatively high percentage of patients of colorectal carcinoma., it seems that p53 mutation plays an important role colorectal carcinogenesis. There was significant association between p53 protein expression and some common clinicopathologic variables such as age and pathologic type ( mucinous/nonmucinous), whereas no significant association was found between p53 expression and other parameters like gender, site of tumor, tumor grade and stage of the disease.