title: Inhibition of Notch and HIF enhances the antitumor effect of radiation in Notch expressing lung cancer.
abstract: BACKGROUND
  The Notch receptor plays an important role in various cell fate decisions during development and in cancer. We have previously reported that Notch3 is upregulated by radiation in non-small cell lung cancer (NSCLC) cell lines and that the Notch pathway inhibitor γ secretase inhibitor GSI (gamma-secretase inhibitor), when combined with radiation therapy, significantly suppressed the growth of lung cancer cells. However, little is known about the mechanism of Notch upregulation induced by radiation. Based on reports of Notch expression being activated through the hypoxia inducible factor 1 (HIF-1) under hypoxic conditions, we hypothesized that HIF-1 would be involved in radiation-induced Notch activation in NSCLC.
  
  
  METHODS
  Changes in HIF-1 and Notch expression in two Notch expressing NSCLC cells line after radiation treatment were examined using Western blotting. Notch expression was evaluated after the suppression of HIF-1α by small interfering RNA. The cytotoxic effect of YC-1, a HIF inhibitor, GSI and radiation was examined using the MTT assay in vitro and the xenograft model.
  
  
  RESULTS
  We found radiation-induced expression of HIF-1α protein at 2-6 h after treatment and upregulated expression of Notch3 protein at 24 h after treatment under hypoxic conditions. Specific suppression of HIF-1α expression downregulated the radiation-induced Notch3 activation, suggesting that the Notch pathway is activated though HIF-1α after radiation. An antitumor effect of YC-1 was evident under hypoxic conditions only when there was simultaneous radiation treatment. GSI and YC-1 had a synergistic antitumor effect in vitro, and the combination of GSI and YC-1 showed the greatest radiosensitivity in vivo.
  
  
  CONCLUSIONS
  Radiation-induced upregulation of the Notch pathway and HIF-1α protein may be potential therapeutic targets for more effective radiation therapy.
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, North 15, West 7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ikezawa
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, North 15, West 7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan. konishj@med.hokudai.ac.jp.
authors.forename: Jun
authors.initials: J
authors.lastname: Sakakibara-Konishi
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, North 15, West 7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Mizugaki
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, North 15, West 7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Oizumi
authors.affiliation: First Department of Medicine, Hokkaido University School of Medicine, North 15, West 7, Kita-ku, Sapporo, Hokkaido, 060-8638, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Nishimura
mesh_terms: D000818:Animals; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000532:radiotherapy*; D015687:Cell Hypoxia / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor / Q000187:drug effects / Q000528:radiation effects; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors* / Q000235:genetics; D007191:Indazoles / Q000494:pharmacology; D008175:Lung Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D008819:Mice, Nude; D058990:Molecular Targeted Therapy / Q000379:methods; D009842:Oligopeptides / Q000494:pharmacology; D034741:RNA, Small Interfering; D051880:Receptors, Notch / Q000037:antagonists & inhibitors* / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007191:Indazoles; D009842:Oligopeptides; D034741:RNA, Small Interfering; D051880:Receptors, Notch; C523462:benzyloxycarbonyl-leucyl-leucyl-norleucinal; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole
keywords: HIF-1; Hypoxia; Lung cancer; Notch; Radiosensitivity