Human rhabdomyosarcoma cells in nude mice as a model for metastasis and differentiation.

We investigated the ability of alveolar (RMZ-RC2) and of embryonal (RD) human rhabdomyosarcoma cell lines to grow and metastasize in nude mice. Both cell lines produced local tumors, but failed to give rise to spontaneous metastases. When RD cells were injected intravenously into nude mice pretreated with cyclophosphamide (in order to depress primarily natural killer activity), several large lung colonies were obtained. Renal localization was also observed. In vitro cultures obtained from tumors or secondaries retained the ability to differentiate in the myogenic pathway shown by the parental cell lines. Intravenous injection into nude mice could therefore constitute an interesting experimental system to study metastatic ability and differentiation properties of human rhabdomyosarcoma cells.