INTERLEUKIN-10 PRODUCTION IN MALIGNANT-MELANOMA - PREFERENTIAL DETECTION OF IL-10-SECRETING TUMOR-CELLS IN METASTATIC LESIONS

IL-10 mRNA expression and protein production in established melanoma c ell lines and freshly cultured primary and metastatic melanoma cells w as examined. The in situ distribution of IL-10 in native melanoma tiss ue was also investigated by immunohistochemistry in primary tumors, me tastases, benign melanocytic nevi and normal skin of healthy persons a nd melanoma patients. IL-10 mRNA, but not IL-10 protein in the culture supernatant, was found in 1 of 4 cultured melanoma cells of primary t umors, while 3 of 6 melanoma-metastasis-derived cultures expressed bot h IL-10 mRNA and protein. No IL-10 was detected in skin biopsies of he althy volunteers or in the healthy skin of melanoma patients; nor was IL-10 found in congenital melanocytic nevi. In only 1 of the 11 examin ed primary malignant melanomas was IL-10 immunoreactivity detected wit hin the cytoplasm of cells in the tumor. On the other hand, 4 of 9 met astases clearly displayed scattered IL-10(+) cells. In all sections wi th IL-10-positive cells, the cells were positive for HMB-45. No co- ex pression of CD3 and IL-10 was observed. The data suggest that melanoma cells themselves are the main origin of IL-10 in tumor specimens in v ivo. The preferential expression of IL-10 in metastatic lesions and in cultured cells from metastases might indicate an increased spreading potential of IL-10-secreting melanoma-cell clones. (C) 1996 Wiley-Liss , Inc.