Use of a human tumor cloning system to screen retinoids for antineoplastic activity.

Retinoid analogs are being actively evaluated as antitumor agents in man. A human tumor cloning system was used to assess the antineoplastic activity of all-trans-retinoic acid, all-trans-retinol and 13-cis-retinoic acid. The effect of retinoids on the formation of tumor colony forming units (T-CFU) was surveyed for 67 different human tumors. These analogs showed minor activity in a variety of neoplasms. The decrease in T-CFU varied between histologic tumor types and between tumor of the same type. No significant difference between retinoid analogs was noted.