In situ analysis of transforming growth factor-{beta}s (TGF-{beta}1, TGF-{beta}2, TGF-{beta}3and TGF-3 type II receptor expression in malignant melanoma

We have analysed, by in situ hybridization, mRNA expressionof TGF-ß1, TGF-ß2, TGF-ß3, andof TGF-ß type II receptor in benign melanocytic naevi,primary melanomas, and in skin metastases of malignant melanomas.Our results show that melanoma progression correlates with overexpressionof TGF-ß. All skin metastases and most primary melanomasinvasive to Clark's level IV-V revealed specific TGF-ß2mRNA and protein expression. However, expression of this cytokinewas not observed in benign melanocytic lesions and was detectedonly in one of five early primary melanomas investigated. Someprimary melanomas and skin metastases also revealed specificTGF-ß1 mRNA signals although expression of this isoformwas not found in benign naevi. TGF-ß3 expression,which was only barely detectable in benign melanocytic lesions,was enhanced in some skin metastases. Interestingly, the epidermisoverlaying melanomas revealed lower levels of TGF-ß3mRNA expression than epidermis of healthy skin or epidermisadjacent to benign naevi, thereby suggesting that paracrinemechanisms between tumour cells and keratinocytes may influencemelanoma development. In primary melanomas TGF-ß typeII receptor mRNA signals were much more heterogeneously distributedwhen compared to benign melanocytic naevi, suggesting variabledegrees of TGF-ß resistance among melanoma cells withinindividual lesions. However, melanoma progression appeared notto be correlated with a complete loss of TGF-ß typeII receptor gene expression, since all skin metastases revealedclearly detectable although heterogeneous levels of TGF-ßtype II receptor mRNA expression.