Tissue microarray FISH applied to colorectal carcinomas with various microsatellite status.

Colorectal carcinoma is etiopathologically heterogenic. It may develop through a sequence of mutations leading to chromosome instability or be a result of defects in DNA repair mechanisms manifested by microsatellite instability of varying degrees. Colorectal carcinoma can thus be classified into microsatellite-stable (MSS), highly microsatellite unstable (MSI-H) and intermediate low-level microsatellite unstable (MSI-L) groups. Fluorescent hybridization in situ (FISH) is a method of detecting specific sequences of nucleic acids that is based on specific bonding of a fluorescent marker-associated probe and specific DNA fragment. The material consisted of 146 non-selected cases of colorectal carcinoma patients operated on at First Chair of General Surgery, Collegium Medicum, Jagiellonian University in Cracow, Poland. Following a standard histopathological evaluation, tissue microarrays were prepared using a Tissue MicroArray Builder, and FISH was performed employing probes specific for chromosomes 1, 8, 17 and 18. Microsatellite instability was evaluated in frozen material using the PCR reaction with gel and capillary electrophoresis. The mean number of signals obtained for chromosome 1 in the entire material was 2.06, while the corresponding mean values in the MSS group equaled 2.07, in the MSI-L group - 2.07, and in the MSI-H group - 2.01. The mean number of signals for chromosome 17 in the entire material was 2.1, in the MSS group - 2.11, in the MSI-L group - 2.13, and in the MSI-H group - 2.01. The number of signals for chromosome 18 in the entire material was 2, in the MSS group - 2, in the MSI-L group - 2, and in the MSI-H group - 2. The means number of signals for chromosome 8 in the entire material was 2.07, in the MSS group - 2.08, in the MSI-L group - 2.01, and in the MSI-H group - 2. These differences are not sufficient for distinguishing colorectal carcinoma molecular forms.