[Characterization of two choliocarcinoma cell lines and their sensitivity to MTX]

Both the sensitivity to MTX and hCG secretion were compared in two choriocarcinoma cell lines (BeWo and HCCM-5) and study on mechanisms about MTX-resistance was described. The uptake of nucleotides and protein precursors was decreased in dose-dependent manner in both cell lines when exposed to MTX, but HCCM-5 cells showed more sensitivity to MTX. In HCCM-5 cells, both hCG and hCG-beta levels in the medium were decreased with exposure to 10(-9)M MTX, but they tended to increase when exposed to higher concentration of MTX in contrast to the inhibition of 3H-thymidine uptake. However, in BeWo cells, an inverse relationship between the incorporation of 3H-thymidine and secretion of hCG was not clearly observed. The content of dihydrofolate reductase (DHFR) in HCCM-5 cells was about one-half of that in BeWo cells. Although the peak of 3H-MTX incorporation was observed at 120 minutes in both cell lines, HCCM-5 cells incorporated about 4 times higher 3H-MTX than BeWo cells. The difference of sensitivity to MTX between those two cell lines seems to be concerned with both the decrease of MTX transport and increase of intracellular DHFR levels.