title: P-glycoprotein depresses cisplatin sensitivity in L1210 cells by inhibiting cisplatin-induced caspase-3 activation.
abstract: Multidrug resistance (MDR) is a phenomenon in which cells become resistant to cytostatic drugs and other substances with diverse chemical structures and cytotoxicity mechanisms. The most often observed molecular mechanism for MDR includes high levels of P-glycoprotein (P-gp)--an ABCB1 member of the ABC drug transporter family. Overexpression of P-gp in neoplastic tissue is an obstacle to chemotherapeutic treatment. Herein, we were focused on differences in apoptosis induced by cisplatin (no substrate for P-gp) between P-gp-positive and P-gp-negative L1210 cells. P-gp-positive cells were obtained by either L1210 cell adaptation to vincristine (R) or L1210 cell transfection with the human gene for P-gp (T) and compared with parental L1210 cells (S). R and T cells were more resistant to CisPt than S cells. R and T cell resistance to CisPt-induced apoptosis could not be reversed by verapamil (a well-known P-gp inhibitor), which excludes P-gp transport activity as a cause of CisPt resistance. CisPt induced a more pronounced entry into apoptosis in S than R and T cells, which was measured using the annexin-V/propidium iodide apoptosis kit. CisPt induced more pronounced caspase-3 activation in S than R and T cells. CisPt did not induce changes in the P-gp protein level for R and T cells. While similar levels of Bax and Bcl-2 proteins were observed in P-gp-negative and P-gp-positive cells, CisPt induced a more significant decrease in Bcl-2 levels for S cells than P-gp-positive cells. Expression of p53 and its molecular chaperone Hsp90 were more pronounced in R and T than S cells. Moreover, CisPt enhanced the upregulation of p53 and Hsp90 in R and T cells to a higher degree than S cells. Apoptosis was shown to be the prevalent mode of cell death in S, R and T cells by the typical DNA fragmentation and cell ultrastructure changes. All of the above findings indicate that P-gp, independent of its drug efflux activity, induced changes in cell regulatory pathways that confer a partial loss of cisplatin sensitivity.
authors.affiliation: Institute of Molecular Physiology and Genetics, Centre of Excellence of the Slovak Research and Development Agency BIOMEMBRANES2008, Slovak Academy of Sciences, 83334 Bratislava, Slovak Republic.
authors.forename: Lenka
authors.initials: L
authors.lastname: Gibalová
authors.forename: Mário
authors.initials: M
authors.lastname: Sereš
authors.forename: Andrej
authors.initials: A
authors.lastname: Rusnák
authors.forename: Peter
authors.initials: P
authors.lastname: Ditte
authors.forename: Martina
authors.initials: M
authors.lastname: Labudová
authors.forename: Branislav
authors.initials: B
authors.lastname: Uhrík
authors.forename: Jaromir
authors.initials: J
authors.lastname: Pastorek
authors.forename: Ján
authors.initials: J
authors.lastname: Sedlák
authors.forename: Albert
authors.initials: A
authors.lastname: Breier
authors.forename: Zdenka
authors.initials: Z
authors.lastname: Sulová
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000187:drug effects / Q000378:metabolism; D002945:Cisplatin / Q000494:pharmacology*; D053938:DNA Fragmentation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D007939:Leukemia L1210 / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics; D014700:Verapamil / Q000494:pharmacology; D014750:Vincristine / Q000494:pharmacology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D018841:HSP90 Heat-Shock Proteins; D016159:Tumor Suppressor Protein p53; D014750:Vincristine; D014700:Verapamil; D053148:Caspase 3; D002945:Cisplatin