Relation between DNA ploidy status and the expression of the DNA-mismatch repair genes MLH1 and MSH2 in cytological specimens of melanoma lymph node and liver metastases

DNA-mismatch repair is essential for preventing genetic instability, and it s important protective role has been demonstrated in several tumors. The ma in aim of this study was to investigate the expression of MLH1 and MSH2 (on the RNA level) in melanoma liver and lymph node metastases, and to define the relation between DNA ploidy status and mismatch repair gene expression. MLH1 was found in 29/33 melanoma lymph node and in 5/17 melanoma liver meta stases. MSH2 was present in 26/33 lymph node and 5/17 liver metastases. A c omparison of MLH1 and MSH2 positive and negative melanoma metastases showed that there were highly significant differences in the percentages of diplo id cells, aneuploid cells between 4c and 8c, octaploid cells, and 5c exceed ing rate. This fact confirms the strong relation between the loss of DNA-mi smatch repair gene expression and advanced DNA aneuploidy status in melanom a metastases. (C) 2001 Wiley-Liss, Inc.