Darstellung genetischer Heterogenität und genetischer Instabilität in malignen Melanomen mittels Mikrodissektion und Mikrosatelliten-PCR

A salient feature of malignant melanoma is the histological polymorphism, what seems to be caused by a high rate of mutation of the melanoma cells. This genetic instability appears to be one reason for the immense malignancy and therapy resistance of malignant melanoma. In this study the genetic instability of malignant melanoma is shown. Primary tumors and metastasis of eight melanoma patients were examined histologically. By microdissection of pleomorph tumor cell nests, 92 tumor probes could be isolated. They were investigated microbiologically by microsatellite-PCR and TG-SSCP-analysis. The microdissection and the subsequent genetic analysis of microdissected tumor cell nests have be established and evaluated as a new technique. It could be shown, that the analysis of microsatellite-DNA emanated from microdissected tumors allows the detection of mutations in microsatellite-DNA and thus the detection of genetic heterogeneity. Furthermore it could be shown, that the analysis of microsatellite-DNA is significantly more exact using microdissected tumors as compared to non-microdissected tumors. It could be demonstrated, that tumors of the malignant melanoma show a distinct phenotypical and genotypical heterogeneity in terms of both microsatellite instability and chromosomal instability. These results make clear, that an exact and reliable statement concerning the genetic heterogeneity and the mechanisms of tumor instability can only be provided by the analysis of multiple microdissected tumor cell nests. Both factors, the genetic heterogeneity as well as the genetic instability can have an immense impact on the prognosis and therapeutical response of tumors. To verify and to concretise this statement further standardised studies in terms of microsatellite analysis of microdissected tumors has to be performed