title: Liposome-mediated RNA interference delivery against Erk1 and Erk2 does not equally promote chemosensitivity in human hepatocellular carcinoma cell line HepG2.
abstract: BACKGROUND
  Extracellular signal-regulated kinase (Erk)1 and Erk2 are central mediators of mitogen-activated protein kinase signaling pathway, which plays a key role in proliferation and chemoresistance of cancer cells. However, the effect of Erk1 and Erk2 in these processes may not be the same. The aim of this study was to investigate differential effect of Erk1 and Erk2 down-regulation on chemoresistance in human hepatocellular carcinoma (HCC) cells. Expression level and relative expression analysis in HepG2 cells were performed using RT-PCR and qRT-PCR, respectively. Phosphorylated-Erk1/2 and apoptosis analysis was performed by flow-cytometry (FCM) technique.
  
  
  RESULTS
  The results showed a higher expression level of Erk2 relative to Erk1 in HepG2 cells (P < 0.01). A significant decrease in phosphorylated-Erk1/2 and a compensational response was observed after Erk1 and/or Erk2 silencing using specific small interfering ribonucleic acids (siRNAs) (P < 0.01). Furthermore, 5-fluorouracil (5-FU) chemotherapy following siRNA-mediated knockdown lead to a significant enhancement of chemosensitivity with a higher rate of early apoptosis in Erk2 silencing relative to that of Erk1) + 9%, P < 0.01). 5-FU treatment after dual knockdown of Erk1/2 showed higher rate of early apoptosis relative to single Erk1 silencing (+9.25%, P < 0.01) and also higher rate of late apoptosis compared to single Erk1 and Erk2 silencing (+4.96% and +4.66%, P < 0.01).
  
  
  CONCLUSIONS
  Our data show that liposomal siRNA-mediated down-regulation of Erk1/2 can lead to potent chemosensitizing effects in HepG2 cells. Moreover, a higher chemosensitivity following Erk2 down-regulation than Erk1 down-regulation may be associated with the higher expression of Erk2 in human HCC.
authors.affiliation: a Liver and Gastrointestinal Diseases Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.|b Stem Cell Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.|c Student Research Committee , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Mehdizadeh
authors.affiliation: a Liver and Gastrointestinal Diseases Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Somi
authors.affiliation: b Stem Cell Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Masoud
authors.initials: M
authors.lastname: Darabi
authors.affiliation: d Biotechnology Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Safar
authors.initials: S
authors.lastname: Farajnia
authors.affiliation: e School of Advanced Medical Sciences , Tabriz University of Medical Sciences , Tabriz , Iran.|f Drug Applied Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Abolfazl
authors.initials: A
authors.lastname: Akbarzadeh
authors.affiliation: b Stem Cell Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Soheila
authors.initials: S
authors.lastname: Montazersaheb
authors.affiliation: f Drug Applied Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Yousefi
authors.affiliation: a Liver and Gastrointestinal Diseases Research Center , Tabriz University of Medical Sciences , Tabriz , Iran.|g Center of Excellence for Biodiversity, Faculty of Natural Sciences , University of Tabriz , Tabriz , Iran.
authors.forename: Mortaza
authors.initials: M
authors.lastname: Bonyadi
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000473:pathology*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D005472:Fluorouracil / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D006801:Humans; D008081:Liposomes; D008113:Liver Neoplasms / Q000473:pathology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics*
chemical_list: D008081:Liposomes; D034741:RNA, Small Interfering; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D005472:Fluorouracil
keywords: Hepatocellular carcinoma; chemotherapy; small interfering ribonucleic acid