[Cytotoxic and antitumor effect of antibiotic PSX-1 in vitro and in vivo].

The inhibitory effect of antibiotic PSX-1 on tumour cells was studied in vitro and in vivo. The antibiotic inhibited above all the utilization of the added 14C-labelled uridine and adenine in EAC cells. After a short exposure to PSX-1 (180 min) the synthesis of nucleic acids and proteins in EAC proliferating in vitro was suppressed. Antibiotic PSX-1 in concentrations of about 2.5 mg/ml showed relatively low toxicity on normal human fibroblasts but caused a marked cytotoxic and cytopathic effect on tumour cells. A potential antitumor effect of PSX-1 was evaluated in vivo by using gradually EAC and L 1210 tumours. All the animals treated with the antibiotic in doses of 2.5--5.0 mg/kg/day with the use of EAC and 5.0 mg/kg/day with the use of L 1210 survived for 90 and 40 days respectively and no tumours developed in the treated mice during this period.