Tumorigenicity and dissemination of primary and metastatic human melanomas implanted into different sites in athymic nude mice

In the present study, the growth features and metastatic capacity of human primary and metastatic melanomas transplanted by different routes in nude mice was examined. Eight different human melanoma early cell cultures derived from 3 primary tumors, 1 local recurrence and 4 metastatic lesions of 6 melanoma patients were characterized for cell surface HLA (class I and II) and melanoma-associated antigens and karyotype. These tumors were then transplanted in CD-1 outbred nude mice by subcutaneous, intraperitoneal and intrasplenic routes. It was found that 7 out of 8 melanomas were tumorigenic after subcutaneous implantation without giving rise to metastases; 5 out of 7 melanomas grew when injected intraperitoneally and 3 of them disseminated to peritoneal organs and infiltrated intraperitoneal lymph nodes, liver and pancreas; of 8 melanomas implanted intrasplenically 4 grew in the spleen or invaded intraperitoneal lymph nodes, liver, pancreas, ovaries or lungs. Primary and metastatic melanomas did not differ in the pattern of dissemination. In fact, 2 out of 4 metastases and 1 of 3 primary tumors and 1 recurrence disseminated after intrasplenic or intraperitoneal inoculation. Heterogeneity in the growth pattern of different metastases of the same melanoma patient was also found. No correlation could be detected between the metastatic ability of melanoma cells studied and clinical stage of patients, tumor cell karyotype abnormalities, modal number or with the antigenic phenotype.