[Analysis of cytotoxicity in cultured choriocarcinoma cell lines using methotrexate and actinomycin-D]

The cytotoxicity of methotrexate (MTX) and actinomycin-D (Act-D), and the influence of Citrovorum factor on MTX-treated cells were analyzed in vitro, using two choriocarcinoma cell lines (BeWo and SCH). HCG and beta-HCG in medium were measured with a radioimmunoassay kit, and 3H-MTX,-thymidine, and-uridine with a liquid scintillation counter. The following results were obtained. The MTX resistant cell line of BeWo, named BeWo, was selected by continuous exposure to increasing concentration of MTX in culture medium. The resistant cell was 50 to 100 times as resistant to MTX as the parent BeWo to the inhibition of cell growth and the development of resistance was accompanied by two-third decrease in 3H-MTX transport. The cytotoxicity of MTX and Act-D were found to increase linearly with the drug dose for concentrations between 10(-9) and 10(-4)M, 10(-10) and 10(-7)M, respectively. Act-D caused lethal damage in three choriocarcinoma cells (BeWo, SCH and BeWo) at one-thousandths the concentration of MTX. Citrovorum factor given within twelve hours following the start of methotrexate administration decreased in 3H-MTX transport and inhibited MTX-induced growth.