title: Downregulation of HIF-1a sensitizes U251 glioma cells to the temozolomide (TMZ) treatment.
abstract: The aim of this study was to investigate the effect of downregulation of HIF-1α gene on human U251 glioma cells and examine the consequent changes of TMZ induced effects and explore the molecular mechanisms.
  
  
  
  U251 cell line stably expressing HIF-1α shRNA was acquired via lentiviral vector transfection. The mRNA and protein expression alterations of genes involved in our study were determined respectively by qRT-PCR and Western blot. Cell proliferation was measured by MTT assay and colony formation assay, cell invasion/migration capacity was determined by transwell invasion assay/wound healing assay, and cell apoptosis was detected by flow cytometry.
  
  
  
  We successfully established a U251 cell line with highly efficient HIF-1α knockdown. HIF-1a downregulation sensitized U251 cells to TMZ treatment and enhanced the proliferation-inhibiting, invasion/migration-suppressing, apoptosis-inducing and differentiation-promoting effects exerted by TMZ. The related molecular mechanisms demonstrated that expression of O(6)-methylguanine DNA methyltransferase gene (MGMT) and genes of Notch1 pathway were significantly upregulated by TMZ treatment. However, this upregulation was abrogated by HIF-1α knockdown. We further confirmed important regulatory roles of HIF-1α in the expression of MGMT and activation of Notch1 pathways.
  
  
  
  HIF-1α downregulation sensitizes U251 glioma cells to the temozolomide treatment via inhibiting MGMT expression and Notch1 pathway activation.
authors.affiliation: Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China.
authors.forename: Jun-Hai
authors.initials: JH
authors.lastname: Tang
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, PR China.
authors.forename: Zhi-Xiong
authors.initials: ZX
authors.lastname: Ma
authors.affiliation: Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China.
authors.forename: Guo-Hao
authors.initials: GH
authors.lastname: Huang
authors.affiliation: Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China.
authors.forename: Qing-Fu
authors.initials: QF
authors.lastname: Xu
authors.affiliation: Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiang
authors.affiliation: Division of Neuropathology and Department of Neurodegenerative Disease, Institute of Neurology, University College London, London WC1N 3BG, UK.
authors.forename: Ningning
authors.initials: N
authors.lastname: Li
authors.affiliation: Division of Neuropathology and Department of Neurodegenerative Disease, Institute of Neurology, University College London, London WC1N 3BG, UK.
authors.forename: Kastytis
authors.initials: K
authors.lastname: Sidlauskas
authors.affiliation: National Institute of Biological Sciences, Beijing 102206, PR China.
authors.forename: Eric Erquan
authors.initials: EE
authors.lastname: Zhang
authors.affiliation: Department of Neurosurgery, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, PR China. Electronic address: lvsq0518@hotmail.com.
authors.forename: Sheng-Qing
authors.initials: SQ
authors.lastname: Lv
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D015536:Down-Regulation / Q000187:drug effects* / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005910:Glioma / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics* / Q000378:metabolism; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000077204:Temozolomide; D014162:Transfection
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D003606:Dacarbazine; D000077204:Temozolomide
keywords: Brain glioma; Drug resistance; HIF-1α; Notch1 pathway; O(6)-methylguanine DNA methyltransferase (MGMT); Temozolomide