N,N-Dimethylformamide-induced morphological differentiation and reduction of tumorigenicity in cultured mouse rhabdomyosarcoma cells.

N,N-Dimethylformamide treatment of cell cultures established from a transplantable murine rhabdomyosarcoma-induced morphological differentiation and a marked reduction in the tumorigenicity of the sarcoma cells. Fourteen of 17 CE/J mice receiving injections of inducer-treated cells did not develop tumors after 6 months, whereas all 21 mice receiving inocula of untreated sarcoma cells died of disease between 11 and 31 days. The drug-treated cells did not grow in soft agar; untreated tumor cells grew in the semisolid medium. The untreated tumor cells showed a reduced serum requirement and had a higher saturation density compared to drug-treated cells. Thus the reduction in tumorigenicity of N,N-dimethylformamide-treated cells correlated with certain in vitro growth properties that are more characteristic of normal, mesenchymally derived cells than of sarcoma cells.