Phototoxic effects of hematoporphyrin derivative and its chromatographic fractions on hormone-producing human malignant trophoblast cells in vitro.

The in vitro phototoxicity of HPD on malignant cells relative to normal cells has been examined. Two human malignant cell lines were studied: the BeWo line of choriocarcinoma cells, which secrete the tumor marker human chorionic gonadotropin (hCG) and its alpha-subunit; and the CaSki line of human cervical carcinoma cells, which secrete hCG and its beta-subunit. Trophoblast-derived, hCG-secreting cells from human amniotic fluid were used as normal controls. In all experiments with HPD plus light, a close correlation was found 24 h after light between cell number and RIA-detectable marker concentration in the medium. Phototoxicity was greater when HPD was introduced in serum-free rather than serum-containing medium. No toxicity was observed in light and dark controls. Cells in Leighton tubes were incubated 1 h with HPD (25 micrograms/ml) in serum-free medium, then rinsed and incubated with medium containing 10% serum. At 2 and 3 days after contact with HPD, flasks were exposed to cool white fluorescent light (1 mW/cm2) for 5 min. Viable cell counts taken 1 day after the light dose indicated that HPD is significantly more phototoxic to BeWo than to CaSki cells; and that both malignant cell types are more photosensitive than amniotic fluid cells, presumably because the latter retain HPD less effectively. In another aspect of this work BeWo cells were used as a model system for comparing the phototoxic effects of the fast (F) and slow (S) eluting fractions of HPD obtained by Bio-Gel P-10 chromatography. Cells in light-shielded tubes were sensitized by incubating with porphyrins for 20 h in media containing 10% calf serum. At 2, 3, or 4 days after removal of porphyrin, with daily replacement of serum-containing medium, flasks were irradiated (see above), and then incubated in the dark for 2 to 4 additional days. Daily culture fluids were analyzed for hormone levels (hCG alpha), and cell counts were performed 2 or 3 days after the light dose. HPD-S (25 micrograms/ml) had no effect on either hormone secretion or cell viability in any of the flasks, whether exposed to light or not. HPD-F at low concentrations (0.25 or 2.5 micrograms/ml) had no detectable effect on cell count or hormone secretion in irradiated flasks. At 10 micrograms/ml, HPD-F was innocuous in dark controls, but caused a large decrease in cell count and hormone output in irradiated flasks.(ABSTRACT TRUNCATED AT 400 WORDS)