An enhanced ability for transforming adriamycin into a noncytotoxic form in a multidrug-resistant cell line (LZ-8)

• Published in: Biochemical pharmacology Vol. 44; no. 9; p. 1869
• Main Authors: Zhang, Y, Sweet, K M, Sognier, M A, Belli, J A
• Format: Journal Article
• Language: English
• Published: England 03.11.1992
• Subjects: Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Cell Line; Cell Membrane; Chromatography, High Pressure Liquid; Cricetinae; Cricetulus; Culture Media; Doxorubicin - metabolism; Doxorubicin - pharmacokinetics; Doxorubicin - toxicity; Drug Resistance - physiology; Inactivation, Metabolic; Intracellular Fluid - metabolism; Membrane Glycoproteins - metabolism; Protein Binding; Stem Cells - drug effects
• ISSN: 0006-2952
• DOI: 10.1016/0006-2952(92)90083-U

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.