Prediction of in vivo tumor response to chemotherapeutic agents by the in vitro sister chromatid exchange assay.

The ability of the in vitro sister chromatid exchange (SCE) assay to predict in vivo tumor drug sensitivity was investigated using a spontaneous hepatocarcinoma in C3Hf/Kam mice and 3 chemotherapeutic agents: melphalan; cis-platinum; and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). For hepatocarcinoma cells grown in monolayer culture, melphalan was the most efficient at inducing SCEs, and BCNU, the least. cis-Platinum induced a range in SCEs that overlapped those of BCNU and melphalan, suggesting that hepatocarcinoma is not a homogeneous population with intermediate sensitivity, but is a mixture of cis-platinum-sensitive and -resistant cells. According to in vitro cell survival curves, hepatocarcinoma was most sensitive to melphalan, less sensitive to cis-platinum, and essentially resistant to BCNU. The relative antineoplastic effects of melphalan, cis-platinum, and BCNU in vivo were compared by the response of artificial and spontaneous pulmonary metastases and solid tumors to these agents. For artificial metastases, there was a dose-dependent decrease in the number of lung nodules in mice treated with melphalan or cis-platinum, with melphalan being the more effective. BCNU had no effect. Spontaneous pulmonary metastases generated from hepatocarcinoma leg tumors were reduced in those mice treated with melphalan, unaffected by cis-platinum, and increased by BCNU. In hepatocarcinoma leg tumors (5 to 6 mm in diameter), melphalan induced the longest growth delay, and BCNU the least. Therefore, the relative effects produced by these three drugs in vivo were the same as predicted by SCE induction in vitro. The SCE assay may thus have potential clinical application.