An enhanced ability for transforming adriamycin into a noncytotoxic form in a multidrug-resistant cell line (LZ-8).
Multidrug-resistant LZ-8 cells are 9000-fold more resistant to Adriamycin (ADRM) exposure than wild-type V79 cells. To understand more about the mechanisms producing such high level resistance, we tested whether LZ-8 cells inactivate ADRM toxicity to a greater extent than wild-type V79 cells. ADRM was recovered from (1) culture media of wild-type V79 and ADRM-resistant LZ-8 cells; (2) V79 and LZ-8 cells; and (3) LZ-8 cell plasma membrane, and the cytotoxicity was determined by treating V79 cells for 1 hr with a known concentration of the recovered ADRM. ADRM obtained from LZ-8 cells or its culture medium exhibited less cytotoxicity than that recovered from V79 cells or its culture medium. ADRM extracted from LZ-8 cell plasma membrane was noncytotoxic. HPLC analysis revealed that the extracted ADRM was structurally changed compared to stock ADRM. The retention time in the column was 7 min for stock ADRM, and 23 min for the recovered ADRM. Thus, LZ-8 cells have an increased ability to transform ADRM into a noncytotoxic form compared to wild-type V79 cells. This transformation involves structural conversion into a previously unidentified ADRM metabolite. The greatly increased survival of LZ-8 cells compared to V79 cells after ADRM treatment is due to at least two mechanisms: (1) an enhanced ability to inactivate the cytotoxicity of ADRM, and (2) increased drug efflux resulting from the amplification and overexpression of the pgp 1 gene in these cells. Our results suggest the possibility that P-glycoprotein participates in drug binding/inactivation in addition to serving as a drug efflux pump.
University of Texas Medical Branch, Department of Radiation Therapy, Galveston 77555.
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Y
Zhang
K M
KM
Sweet
M A
MA
Sognier
J A
JA
Belli
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D003412:Cricetulus; D003470:Culture Media; D004317:Doxorubicin / Q000378:metabolism / Q000493:pharmacokinetics* / Q000633:toxicity; D004351:Drug Resistance / Q000502:physiology; D008658:Inactivation, Metabolic; D007424:Intracellular Fluid / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D011485:Protein Binding; D013234:Stem Cells / Q000187:drug effects
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003470:Culture Media; D008562:Membrane Glycoproteins; D004317:Doxorubicin