Childhood rhabdomyosarcoma xenografts: Responses to DNA-interacting agents and agents used in current clinical therapy

A laboratory model of childhood rhabdomyosarcoma (RMS) has been used to evaluate cytotoxic agents used in current clinical protocols, and DNA-reacting agents that have had either limited or no evaluation in this histiotype. Seven lines of RMS each derived from a different patient were grown as xenografts in immune-deprived mice, six of these being from specimens derived from previously untreated patients. Of the 'conventional' agents, vincristine was the most effective. Of the other agents evaluated [L-phenylalanine mustard (L-PAM), cis-dichlorodiammineplatinum (cis-DDP), mitomycin C and 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (DTIC)], L-PAM caused complete regressions in six of seven lines, including those resistant to cyclophosphamide. DTIC had marked activity in five tumors, and mitomycin C in three lines. Cyclophosphamide was active in five tumors, although efficacy was less marked in two lines in comparison to DTIC and mitomycin C.