title: WWOX suppresses autophagy for inducing apoptosis in methotrexate-treated human squamous cell carcinoma.
abstract: Squamous cell carcinoma (SCC) cells refractory to initial chemotherapy frequently develop disease relapse and distant metastasis. We show here that tumor suppressor WW domain-containing oxidoreductase (WWOX) (also named FOR or WOX1) regulates the susceptibility of SCC to methotrexate (MTX) in vitro and cure of SCC in MTX therapy. MTX increased WWOX expression, accompanied by caspase activation and apoptosis, in MTX-sensitive SCC cell lines and tumor biopsies. Suppression by a dominant-negative or small interfering RNA targeting WWOX blocked MTX-mediated cell death in sensitive SCC-15 cells that highly expressed WWOX. In stark contrast, SCC-9 cells expressed minimum amount of WWOX protein and resisted MTX-induced apoptosis. Transiently overexpressed WWOX sensitized SCC-9 cells to apoptosis by MTX. MTX significantly downregulated autophagy-related Beclin-1, Atg12-Atg5 and LC3-II protein expression and autophagosome formation in the sensitive SCC-15, whereas autophagy remained robust in the resistant SCC-9. Mechanistically, WWOX physically interacted with mammalian target of rapamycin (mTOR), which potentiated MTX-increased phosphorylation of mTOR and its downstream substrate p70 S6 kinase, along with dramatic downregulation of the aforementioned proteins in autophagy, in SCC-15. When WWOX was knocked down in SCC-15, MTX-induced mTOR signaling and autophagy inhibition were blocked. Thus, WWOX renders SCC cells susceptible to MTX-induced apoptosis by dampening autophagy, and the failure in inducing WWOX expression leads to chemotherapeutic drug resistance.
authors.affiliation: Department of Microbiology and Immunology, National Cheng Kung University Medical College, Tainan, Taiwan.
authors.forename: C-W
authors.initials: CW
authors.lastname: Tsai
authors.forename: F J
authors.initials: FJ
authors.lastname: Lai
authors.forename: H M
authors.initials: HM
authors.lastname: Sheu
authors.forename: Y S
authors.initials: YS
authors.lastname: Lin
authors.forename: T H
authors.initials: TH
authors.lastname: Chang
authors.forename: M S
authors.initials: MS
authors.lastname: Jan
authors.forename: S M
authors.initials: SM
authors.lastname: Chen
authors.forename: P C
authors.initials: PC
authors.lastname: Hsu
authors.forename: T T
authors.initials: TT
authors.lastname: Huang
authors.forename: T C
authors.initials: TC
authors.lastname: Huang
authors.forename: M C
authors.initials: MC
authors.lastname: Sheen
authors.forename: S T
authors.initials: ST
authors.lastname: Chen
authors.forename: W C
authors.initials: WC
authors.lastname: Chang
authors.forename: N S
authors.initials: NS
authors.lastname: Chang
authors.forename: L J
authors.initials: LJ
authors.lastname: Hsu
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D045744:Cell Line, Tumor; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D008727:Methotrexate / Q000494:pharmacology* / Q000627:therapeutic use*; D008954:Models, Biological; D009363:Neoplasm Proteins / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014062:Tongue Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects; D000074584:WW Domain-Containing Oxidoreductase
chemical_list: D009363:Neoplasm Proteins; D025521:Tumor Suppressor Proteins; D010088:Oxidoreductases; D000074584:WW Domain-Containing Oxidoreductase; C486071:WWOX protein, human; D058570:TOR Serine-Threonine Kinases; D008727:Methotrexate