Anti-tumor effect of (S)-10-hydroxycamptothecin on mouse hepatoma BW7756 and its possible mode of action.

(S)-10-Hydroxycamptothecin (OPT), an analog of camptothecin (CPT), was found to inhibit the growth of the mouse hepatoma BW7756, when given at 1.0 mg/kg/day for 14 days. Cell cycle studies using flow cytofluorometry indicated that this drug inhibited the S-Phase of the tumor cells in vivo and the S and G2/M phases in vitro. Similar studies on host liver showed little or no effect. In spite of the narrow range of the effective dose of this drug against mouse hepatoma BW7756, the use of OPT in combination with other antitumor agents may be useful in primary hepatoma or liver metastases in view of its low toxicity towards host liver. A simple cytofluorometric method useful for live cell cycle study has been adapted for this investigation and can be adopted for other drug studies.