[Inhibitory effects of OK-432 and PSK on cell growth of in vitro human choriocarcinoma cell lines].

The cancer chemotherapy combined with immuno-potentiators, OK-432 and/or PSK, had yielded an improvement in survival rate of choriocarcinoma patients in our clinic as previously reported elsewhere. In the present study, for the purpose of evaluation of direct antitumor activity of OK-432 and PSK, inhibitory effects of the drugs on cell growth of GCH-1 and GCH-2 (in vitro cell lines of human choriocarcinoma) were analyzed referring to those of MTX (methotrexate) and Act-D (actinomycin D). 1) IC 50 (50% inhibitory concentration) of OK-432 and of PSK were 0.56 KE/ml on GCH-1 and 0.48 KE/ml on GCH-2, and 310 micrograms/ml on GCH-1 and 460 micrograms/ml on GCH-2, respectively. 2) The morphological changes of the target cells, observed by light and electron microscope, induced by OK-432 and PSK seemed to be not different from those by MTX and Act-D. 3) Serial changes of hCG levels in the culture media in which OK-432 or PSK was added were roughly comparable with those in MTX or Act-D. Thus, the direct antitumor activity of OK-432 and PSK on GCH-1 and GCH-2 was exquisitely weak judging from their IC50 and it was suggested that their direct antitumor effects in vivo might be clinically negligible in choriocarcinoma.