EFFECT OF PSC-833 ON THE EFFICACY OF DOXORUBICIN IN-VITRO IN A MEDULLARY-THYROID CARCINOMA CELL-LINE

In medullary carcinoma of the thyroid (MTC), multidrug resistance (MDR ) remains the major obstacle to effective chemotherapy. In this work M DR was investigated in TT cells, a human MTC cell line. We studied the effect of an efficient MDR agent (SDZ PSC 833) on doxorubicin (DOX)-i nduced cytotoxicity in TT cells cultured in monolayers. The toxicity w as evaluated with four tests: MTT test, lacticodehydrogenase and gluta thione assays, and neutral red uptake. PSC 833 (3 mu M) partially reve rsed the resistance to DOX in vitro after a 48-hour coincubation, foll owed by a 24 hour-post incubation. Under these conditions, PSC 833 was not toxic at the concentration used. Our results suggest that PSC 833 has the potential to reverse the MDR phenotype in MTC cells.