Reversal of the human and murine multidrug-resistance phenotype with megestrol acetate.
MA is an orally active PG derivative with an excellent safety profile that is used primarily for the treatment of carcinomas of the breast and endometrium. We investigated the potential application of MA as an MDR-reversal agent using cell culture and human tumor xenograft models. The reversing activity of MA in vitro was compared with that of PG and VER in two human MDR cell lines, the colon carcinoma HCT-116/VM46 and the breast carcinoma MCF-7/ADR, and in a murine cell line, J774.2. At concentrations as low as 3 microM, MA was capable of partially restoring sensitivity to Act D in the HCT-116/VM46 cells and sensitivity to DOX in the MCF-7/ADR cells. Although less effective than VER, MA was about 2.5 times more potent than PG in reversing MDR at equimolar concentrations. Increased accumulation of DOX in drug-resistant cells that were treated simultaneously with MA was observed by flow cytometry. In vivo, using established human colon and breast carcinoma xenografts implanted s.c. in athymic mice, the combined therapy with MA and DOX resulted in enhanced antitumor activity relative to that of DOX alone in the MDR sublines. These results suggest that MA may be a promising clinical MDR-reversing agent.
Wang
L
L
Department of Experimental Therapeutics, Bristol-Myers Squibb Company, Princeton, NJ 08543.
Yang
C P
CP
Horwitz
S B
SB
Trail
P A
PA
Casazza
A M
AM
D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000037:antagonists & inhibitors* / Q000627:therapeutic use / Q000633:toxicity; D001943:Breast Neoplasms / Q000188:drug therapy; D002277:Carcinoma / Q000188:drug therapy; D017024:Chemotherapy, Adjuvant; D003110:Colonic Neoplasms / Q000188:drug therapy; D003609:Dactinomycin / Q000008:administration & dosage / Q000633:toxicity; D004317:Doxorubicin / Q000008:administration & dosage / Q000633:toxicity; D004351:Drug Resistance; D004354:Drug Screening Assays, Antitumor; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000188:drug therapy; D008535:Megestrol / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use / Q000633:toxicity; D019290:Megestrol Acetate; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010641:Phenotype; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured / Q000187:drug effects
D003609:Dactinomycin; D004317:Doxorubicin; D008535:Megestrol; D019290:Megestrol Acetate