Expression of the mismatch repair protein hMSH2 in carcinoma in situ and invasive cancer of the breast

Background: Dysregulations in the mechanism of DNA-repair are contributed t o tumorgenesis and tumorprogression in human cancer. The mismatch repair ge ne hMSH2 encodes a protein, which recognizes and binds to mismatch-sequence s of the DNA. Methods: Using immunohistochemical techniques hMSH2 expressio n was analyzed in invasive cancer (n=85) and in situ carcinoma (n= 34) of t he breast. Results: The percentage of hMSH2 positive cases was significantl y (p=0.0001) decreased in invasive cancer as compared to in situ carcinomas . There was an association of hMSH2 expression with parameters of unfavorab le prognosis, such as lymph none involvement (p=0.03), higher degree of mal ignancy (p=0.05) and higher proliferative activity (p=0.05). Conclusions: D uring development from in situ to invasive cancer of the breast, hMSH2 expr ession seems to be downregulated However, in invasive cancel, hMSH2 express ion seems to be associated with tumor progression. This could be explained by the fact that enhanced proliferation of tumor cells results in increased mistakes within DNA replication procedures.