PTEN/MMAC1 in malignant melanoma and its importance for tumor progression.

A novel tumor suppressor gene, PTEN/MMAC1, on 10q23, displayed a number of mutations in solid tumors as gliomas and breast cancer. Aberrations of the long arm of chromosome 10 have been frequently detected in tumor progression of malignant melanoma of the skin by a variety of methods including cytogenetic analysis, fluorescence in situ hybridization and loss of heterozygosity analysis. Compared to previous studies, which propose an involvement of PTEN/MMAC1 in malignant melanoma mostly on the basis of data derived from cell lines and metastases, we analyzed a broader spectrum of exclusively patient derived tumor tissue by PCR and direct sequencing analysis of PTEN/MMAC1. Here, we present data of 25 primary melanomas (8 superficial spreading melanomas, 17 nodular melanomas) and 25 metastases of 41 patients. Neither loss of the complete gene nor a whole exon nor any nonsense mutations could be demonstrated. However, we detected several polymorphisms and some mutations in the introns, and in two metastatic tumors mutations with an amino acid change. Our results obtained from tissue samples underline that mutations of PTEN/MMAC1 are not an essential event in the onset of malignant melanoma of the skin, but could have an impact on tumor progression.