title: Intercellular transfer of P-glycoprotein from the drug resistant human bladder cancer cell line BIU-87 does not require cell-to-cell contact.
abstract: OBJECTIVE
  The efflux activity of transmembrane P-glycoprotein prevents various therapeutic drugs from reaching lethal concentrations in cancer cells, resulting in multidrug resistance. We investigated whether drug resistant bladder cancer cells could transfer functional P-glycoprotein to sensitive parental cells.
  
  
  METHODS
  Drug sensitive BIU-87 bladder cancer cells were co-cultured for 48 hours with BIU-87/ADM, a doxorubicin resistant derivative of the same cell line, in a Transwell® system that prevented cell-to-cell contact. The presence of P-glycoprotein in recipient cell membranes was established using fluorescein isothiocyanate, laser scanning confocal microscopy and Western blot. P-glycoprotein mRNA levels were compared between cell types. Rhodamine 123 efflux assay was done to confirm that P-glycoprotein was biologically active.
  
  
  RESULTS
  The amount of P-glycoprotein protein in BIU-87 cells co-cultured with BIU-87/ADM was significantly higher than in BIU-87 cells (0.44 vs 0.25) and BIU-87/H33342 cells (0.44 vs 0.26, each p <0.001), indicating P-glycoprotein transfer. P-glycoprotein mRNA expression was significantly higher in BIU-87/ADM cells than in co-cultured BIU-87 cells (1.28 vs 0.30), BIU-87/H33342 (0.28) and BIU-87 cells (0.25, each p <0.001), ruling out a genetic mechanism. After 30 minutes of efflux, rhodamine 123 fluorescence intensity was significantly lower in BIU-87/ADM cells (5.55 vs 51.45, p = 0.004) and co-cultured BIU-87 cells than in BIU-87 cells (14.22 vs 51.45, p <0.001), indicating that P-glycoprotein was functional.
  
  
  CONCLUSIONS
  Bladder cancer cells can acquire functional P-glycoprotein through a nongenetic mechanism that does not require direct cell contact. This mechanism is consistent with a microparticle mediated process.
authors.affiliation: Department of Urology, First Affiliated Hospital, Fujian Medical University, Fuzhou, People's Republic of China. zhhllq@sina.com
authors.forename: Hui-liang
authors.initials: HL
authors.lastname: Zhou
authors.forename: Yong-jun
authors.initials: YJ
authors.lastname: Zheng
authors.forename: Xiao-zhi
authors.initials: XZ
authors.lastname: Cheng
authors.forename: Yi-song
authors.initials: YS
authors.lastname: Lv
authors.forename: Rui
authors.initials: R
authors.lastname: Gao
authors.forename: Hou-ping
authors.initials: HP
authors.lastname: Mao
authors.forename: Qin
authors.initials: Q
authors.lastname: Chen
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D001693:Biological Transport, Active; D015153:Blotting, Western; D045744:Cell Line, Tumor / Q000187:drug effects; D018920:Coculture Techniques; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D006801:Humans; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D001749:Urinary Bladder Neoplasms / Q000188:drug therapy / Q000473:pathology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D012333:RNA, Messenger
keywords: ABC; FBS; FITC; LSCM; MDR; P-glycoprotein; P-gp; PBS; PCR; RT-PCR; Rh123; adenosine triphosphate binding cassette; cell-derived microparticles; drug resistance; fetal bovine serum; fluorescein isothiocyanate; laser scanning confocal microscopy; multidrug resistance; phosphate buffered saline; polymerase chain reaction; reverse transcriptase-PCR; rhodamine 123; urinary bladder; urinary bladder neoplasms