Background: Prostate cancer (PCa) is one of the most heritable human cancers and it is the second most frequent malignancy in men worldwide. It accounts for a significant morbidity and mortality throughout the world. PCa with mismatch repair (MMR) deficiency often has aggressive clinical and histological features, but its rarity prevents the analysis of the underlying biology. Therefore, in this study, we aimed to evaluate the immunohistochemical expression of MMR proteins and P53 in PCa.

Materials and methods: Fifty cases of PCa were histologically examined. The MMR proteins and P53 immunoexpression were assessed. Also, P53 serum concentration levels using ELIZA was measured and pre-operative prostatic specific antigen (PSA) serum levels were obtained.

Results: There was a significant positive relation between mutS homologue 2 (MSH2) immunoexpression and both PSA serum level and P53 serum concentration (p value 0.001*). Also, there was a significant relation between MSH2 immunoexpression and tumour size, nodal metastasis, distant metastasis and grade grouping. While mutL homologue 1 (MLH1) immunoexpression showed a significant relation with human P53 serum concentrations only (p value 0.035*). Moreover, MLH1 immunoexpression showed only significant relation with nodal metastasis and tumour burden, p value was 0.033* and 0.001*, respectively.

Conclusion: MMR protein loss, especially MSH2, was seen in a significant subset of PCa. Interestingly, it was associated with significantly higher levels of serum PSA and p53. Moreover, it may be associated with unfortunate prognostic features as large tumour size, higher grade grouping and finally nodal and distant metastasis.