Mechanisms of resistance to chemosensitizers in a multidrug resistant human multiple myeloma cell li...

مرکز و کتابخانه مطالعات اسلامی به زبان های اروپایی

منو

" Mechanisms of resistance to chemosensitizers in a multidrug resistant human multiple myeloma cell line "
M. R. Abbaszadegan W. S. Dalton

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1112816
Doc. No	:	TLpq304171233
Main Entry	:	M. R. Abbaszadegan
	:	W. S. Dalton
Title & Author	:	Mechanisms of resistance to chemosensitizers in a multidrug resistant human multiple myeloma cell line\ M. R. AbbaszadeganW. S. Dalton
College	:	The University of Arizona
Date	:	1995
student score	:	1995
Degree	:	Ph.D.
Page No	:	215
Abstract	:	Tumor cells in cancer patients acquire drug resistance as a result of chemotherapy. One type of acquired drug resistance is multidrug resistance (MDR) caused by the overexpression of P-glycoprotein, a transmembrane efflux protein. Inhibitors of P-glycoprotein or chemosensitizers such as verapamil are used to reverse MDR in cancer patients. Clinical studies have shown that some patients with P-glycoprotein positive cancer cells respond to the chemosensitizing effect of verapamil. However, this response is short lived and tumor cells become resistant to chemosensitizers. In order to study the mechanism of resistance to chemosensitizers, a human myeloma cell line, 8226/MDRV, was selected from a P-glycoprotein positive cell line, 8226/Dox{40}, in the continuous presence of doxorubicin and verapamil. MDRV cells are consistently more resistant to MDR drugs than the parent cells, Dox{40}. Chemosensitizers were less effective in reversing resistance in the MDRV compared to Dox{40} cells. Despite higher resistance to cytotoxic agents, MDRV expresses less P-glycoprotein in the plasma membrane compared to Dox{40}. However, total cellular P-glycoprotein was the same in both cell lines suggesting a relocation of P-glycoprotein from plasma membrane into cytoplasm. Confocal immunofluorescence microscopy showed 2.5X more P-glycoprotein in the cytoplasm of MDRV cells as compared to Dox{40} cells. The relocation of P-glycoprotein was associated with a redistribution of doxorubicin. In Dox{40} cells, doxorubicin was concentrated in the nucleus, whereas in MDRV cells, 90% of doxorubicin was found in the cytoplasm. We hypothesized that P-glycoprotein trafficking from the endoplasmic reticulum to the plasma membrane may be interrupted resulting in a higher concentration in the cytoplasm. To test this hypothesis, endoglycosidase H sensitivity of newly sensitized P-glycoprotein was examined. Medial Golgi processing of P-glycoprotein was identical between the two cell lines and the N-glycosylation of P-glycoprotein was complete by 3 hours. No mutations were found in MDR1 cDNA from MDRV cells compared to Dox{40} cells. These results suggest that increased resistance to cytotoxic drugs and chemosensitizers is associated with an altered intracellular location of P-glycoprotein which in turn causes a redistribution of doxorubicin.
Subject	:	Biological sciences
	:	drug resistance
	:	Health and environmental sciences
	:	Molecular biology
	:	multidrug resistance
	:	Pharmacology