Retinoic acid and cisdiaminodichloroplatinum in the treatment of murine teratocarcinomas in vivo in a nullipotent model.

Induction of differentiation as a treatment modality for nonseminomatous germ cell tumors (NSGCTs) may promote the development of residual mature teratoma (RMT), which is usually associated with primary tumors that are capable of spontaneous somatic differentiation. Therefore, we studied the combination of a cytotoxic drug and a differentiation-inducing agent in vivo in three murine teratocarcinoma models with different levels of spontaneous somatic differentiation: E86-379 (moderate differentiation); NF-1 (poor differentiation); and MH-15 (no differentiation). We used retinoic acid (RA) as differentiation-inducing agent and cisdiaminodichloroplatinum (CDDP) as cytotoxic drug, plus a combination of both. In four separate experiments, the combination of RA and CDDP gave a significant further reduction of tumor size as compared with treatment with either RA or CDDP alone. Morphologically intact tumor after treatment with combined RA-CDDP contained a smaller proportion of undifferentiated tissue (embryonal carcinoma) than after CDDP alone. However, somatic differentiation was not induced in the tumor model lacking spontaneous somatic differentiation. Toxicity was reflected in loss of body weight and death of some animals and closely paralleled the degree of tumor reduction in all experiments.