A NEW ALLOGENEIC MODEL FOR METASTATIC MELANOMA

Metastatic melanoma cells, clonally derived from an affected lymph nod e of an ultraviolet-irradiated laboratory opossum, were allografted su bcutaneously into suckling young, juveniles and adults to determine th eir tumorigenicity and metastatic potential. All injected 1- and 3-wee k-old suckling young survived well beyond weaning at 8 weeks, One died 12 weeks after injection from the effects of rampant metastatic invol vement, while the rest were killed 13 to 26 weeks after injection. At necropsy, most animals showed extensive primary tumour growth, many sh owed metastasis to nodes and/or lungs, and in some there was dissemina tion to distant sites including liver and spleen. Animals injected as juveniles or adults rejected the allografts. Injection of allogeneic m alignant melanoma cells during early postnatal development facilitates successful, long-term allografting and metastasis without concomitant immunosuppressive agents. Developmental lack of self-recognition (imm unological immaturity) or induced tolerance may be responsible. This u nique model system will be useful for further metastasis studies and m ay be valuable for investigations of novel antineoplastic therapies.