8-METHOXYPSORALEN POTENTIATES THE PHOTOCYTOTOXIC EFFECT OF PHOTOFRIN-II TOWARDS EMT-6 MURINE TUMOR-CELLS

Pretreatment of EMT-6 murine tumor cells for 24 h with 10(-4) M 8-meth oxypsoralen (8-MOP) increased the photocytotoxicity of Photofrin II (P 2) after cell exposure to low doses (1-1.5 J/cm(2)) of WA by two- to t hree-fold. 8-MOP alone had no cytotoxic action under these experimenta l conditions and did not significantly change the amount of P2 recover ed in cells. 8-MOP enhanced the lipid peroxidation end product formati on measured as thiobarbituric acid reactive substances (TEARS) during cell photosensitization by P2. The psoralen alone also slightly increa sed the TEARS level after WA exposure. These results suggest that 8-MO P, albeit non-photocytotoxic by itself under our experimental conditio ns, could enhance the efficiency of P2 by increasing cellular lipid pe roxidation following light exposure. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.