Correlation of microsatellite status, proliferation, apoptotic and selected immunohistochemical markers in colorectal carcinoma studied with tissue microarray.

Colorectal carcinoma is a frequent malignant tumor, characterized by varying clinical course and response to treatment. At the molecular level, colorectal carcinomas are divided into tumors with chromosomal instability (microsatellite-stable, MSS), microsatellite instability (MSI-H) and low microsatellite instability (MSI-L). The method of tissue microarrays allows for combining materials originating from multiple patients into a single slide, what makes possible to simultaneously investigate large material for the presence of numerous, diversified markers. The study material consisted of 208 cases of colorectal carcinoma. Microsatellite instability was evaluated in frozen material employing the PCR reaction with gel and capillary electrophoresis. Following a standard histopathological assessment, tissue microarrays were prepared using a MTA-1 microarrayer (Beecher) and standard immunohistochemical reactions were performed to detect the presence of bcl-2, CDX-2, Ki67, MLH1, MSH2, MSH6, p16, p53 and survivin. Apoptotic cells were detected using the TUNEL method. The correlations between the reactions were investigated and differences in the expression of the investigated proteins noted in carcinomas with various degrees of microsatellite instability. The agglomeration analysis showed differences in patterns of expression between MSS, MSI-L and MSI-H carcinomas. The discriminant function analysis demonstrated that the MSI-H carcinomas were best differentiated by MLH1, survivin and Ki67 expression, while the MSI-L tumors differed from the remaining colorectal carcinomas by their apoptotic index, local tumor stage (pT), the presence of angioinvasion and mucin production.