title: Inhibition of the JNK signaling pathway increases sensitivity of hepatocellular carcinoma cells to cisplatin by down-regulating expression of P-glycoprotein.
abstract: OBJECTIVE
  The resistance of hepatocellular carcinoma (HCC) to chemotherapy may be mediated by the c-Jun N-terminal kinase (JNK) pathway. We wished to verify the involvement of this pathway in resistance of HCC cells to cisplatin.
  
  
  METHODS
  We used HepG2 cell line and cisplatin-resistant clone (HepG2/DDP). Expressions of drug resistance and apoptosis-related genes were analyzed by qPCR. Protein expressions were assessed by Western blot. The JNK pathway was assessed as total JNK1/2 and JNK1/2 phosphorylation. Cell growth kinetics was quantified by the CCK-8 assay, and cell apoptosis (Annexin V / propidium iodide) by flow cytometry.
  
  
  RESULTS
  HepG2/DDP cells were more resistant and less apoptotic on cisplatin. Expression of drug-resistance genes MDR1, MRP1 and MPR2 was significantly up-regulated in HepG2/DDP cells (p < 0.05), with up-regulation of MDR1 being the highest. This was confirmed by Western blot analysis of P-glycoprotein (P-gp), MRP1 and MRP2 proteins, the proteins encoded by the above genes. Expression of anti-apoptotic genes Bcl-2 and Bcl-XL was significantly up-regulated, and expression of pro-apoptotic genes Bak and Bad was significantly reduced, in HepG2/DDP cells (p < 0.05). Cisplatin treatment of HepG2 led to increased phosphorylation of JNK1/2; the trend reversed by the inhibitor SP600125. Furthermore, cisplatin increased expression of P-gp, which was also attenuated by SP600125. Cell growth was inhibited more substantially, and cell apoptosis promoted, when HepG2 cells were exposed to both cisplatin and SP600125.
  
  
  CONCLUSIONS
  Inhibition of the JNK signaling pathway enhances the sensitivity of HCC cells to cisplatin by down-regulating the expression of P-gp.
authors.affiliation: Department of Oncology, The First Affiliated Hospital of Chongqing Medical University, Chongqing, China. 631681076@qq.com.
authors.forename: X-Y
authors.initials: XY
authors.lastname: Liu
authors.forename: S-P
authors.initials: SP
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Jiang
authors.forename: X
authors.initials: X
authors.lastname: Zhang
authors.forename: T
authors.initials: T
authors.lastname: Zhang
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000502:physiology; D002945:Cisplatin / Q000494:pharmacology* / Q000627:therapeutic use; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D056945:Hep G2 Cells; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D048031:JNK Mitogen-Activated Protein Kinases; D002945:Cisplatin