title: Effect of shikonin on multidrug resistance in HepG2: The role of SIRT1.
abstract: BACKGROUND
  Overexpression of SIRT1 is considered to enhance the resistance of HepG2 cells to irradiation. Shikonin, a naturally occurring naphthoquinone compound, displays anticancer effects and circumvents cancer drug resistance.
  
  
  OBJECTIVE
  This study investigated the MDR reversal effect of shikonin induced by the overexpression of SIRT1.
  
  
  METHODS
  The overexpression of SIRT1 in HepG2 cells was established by lentivirus infection. Five days after transduction, real-time quantitative polymerase chain reaction and western blotting were used to detect the expression of SIRT1 and MDR1/P-gp. Drug resistance was also evaluated by flow cytometry after rhodamine-123 staining. On day 5, the multidrug resistance cells were treated by shikonin (10(-7), 10(-6), and 10(-5) µmol/L) one time. The cell viability was detected by the MTT assay, and apoptosis was evaluated by Hoechst 33342 staining and caspase-3 activity 24 h after shikonin treatment.
  
  
  RESULTS
  Overexpression of SIRT1 decreased rhodamine-123 staining and successfully produced the R-HepG2 cell line. Compared with HepG2, the expression of MDR1/P-gp mRNA (3.45 ± 0.35) and protein (1.40 ± 0.05) were both upregulated in R-HepG2. Shikonin inhibited cell viability (from 93.9 ± 2.1 to 66.7 ± 1.5%), induced apoptosis of R-HepG2 (apoptotic ratio from 3.5 ± 0.8 to 47.5 ± 2.7%, caspase-3 activity from 103.5 ± 1.9 to 329.2 ± 14.9%, respectively), downregulated the mRNA and protein expression of SIRT1 and MDR1/P-gp, and decreased rhodamin 123 efflux.
  
  
  CONCLUSIONS
  In the present study, we demonstrated that shikonin is able to overcome drug resistance in hepatocellular carcinoma cells, and the mechanism is related to the SIRT1-MDR1/P-gp signaling pathway.
authors.affiliation: Department of Medical Oncology, Sichuan Cancer Hospital , Chengdu , China and.
authors.forename: Yong-Dong
authors.initials: YD
authors.lastname: Jin
authors.forename: Yi
authors.initials: Y
authors.lastname: Ren
authors.forename: Ming-Wei
authors.initials: MW
authors.lastname: Wu
authors.forename: Ping
authors.initials: P
authors.lastname: Chen
authors.forename: Jin
authors.initials: J
authors.lastname: Lu
mesh_terms: D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D018432:Drug Resistance, Multiple / Q000187:drug effects* / Q000502:physiology; D019008:Drug Resistance, Neoplasm / Q000187:drug effects* / Q000502:physiology; D056945:Hep G2 Cells; D006801:Humans; D009285:Naphthoquinones / Q000494:pharmacology*; D056564:Sirtuin 1 / Q000502:physiology*
chemical_list: D009285:Naphthoquinones; C016101:shikonin; C447939:SIRT1 protein, human; D056564:Sirtuin 1
keywords: Apoptosis; HepG2; NAD+-dependent deacetylase; caspase-3; hepatocellular cancer; multidrug resistance 1/P-gp; paclitaxel; rhodamin-123; sirtuin 1