Expression of hMSH2 and hMLH1 proteins of the human DNA mismatch repair system in ameloblastoma

The human DNA mismatch repair (hMMR) system plays an important role in redu cing mutation and maintaining genomic stability. The MMR system in human ce lls is composed of at least six genes (hMSH2, hMLH1, hMSH3, hPMS1, hPMS2 an d GTBP/hMSH6). in particular, hMSH2 and hMLH1 are expressed in human cells that are undergoing rapid renewal; their reduced expresion has been reporte d in several tumors. We examined the protein expression pattern of hMSH2 an d hMLH1 by immunohistochemistry in 25 ameloblastomas. All ameloblastomas ex pressed hMSH2 and hMLH1 proteins in the outer layer of epithelial cells. Th e localization of the staining was exclusively nuclear. These data suggest that the development and progression of these tumors do not depend on a def ect in the hMMR system.