Decreased expression of human melanoma-associated antigen ME491 along the progression of melanoma pre-canceroses to invasive and metastatic melanomas.

ME491 expression was examined by immunohistochemistry in the different stages of various types of human malignant melanomas. In addition, the primary and metastatic lesions in five patients were studied to compare the ME491 antigen expression between these lesions in a single patient. A large proportion of cells from melanoma pre-canceroses showed strong ME491 expression, whereas the proportion of negatively stained tumour cells increased in the melanomas invading the dermis and in metastatic melanomas. In addition, a comparison of five sets of primary tumour and its metastatic lesion revealed decreased expression of this antigen in metastases. These results show that the reduction or loss of ME491 antigen expression is associated with increased invasiveness and metastatic ability of human malignant melanoma, suggesting that ME491 may act as an anti-metastatic gene.