title: Everolimus sensitizes Ras-transformed cells to radiation in vitro through the autophagy pathway.
abstract: Modern radiation therapy strives to minimize injury to organs while increasing the anticancer effects. The present study aimed to investigate the radiosensitizing effects of everolimus and to examine the molecular mechanisms responsible for everolimus‑mediated radiosensitization. Radiation in combination with everolimus (30 nM) sensitized Ras-transformed cells to radiation in vitro. Radiation induced apoptotic markers (sub-G1 cell accumulation, membrane inversion and DNA fragmentation) and treatment with everolimus did not promote radiation-induced apoptosis. However, LC3-II expression increased following combination treatment with everolimus and radiation, and the radiosensitizing effects of everolimus were reversed following transfection with small interfering RNA (siRNA) targeting Beclin 1. In addition, the protein levels of activated S6 kinase 1 (S6K1) were significantly reduced following treatment with everolimus, and the phosphorylation of factor 4E binding protein 1 (4EBP1) was suppressed following combination treatment. Taken together, our data demonstrate that everolimus sensitizes Ras-transformed cells to radiation in vitro. Everolimus-mediated radiosensitization is associated with the autophagy pathway. Thus, everolimus is a novel radiosensitizing agent with potential for use in cancer radiotherapy.
authors.affiliation: Department of Hematological Oncology, Buddhist Dalin Tzu Chi Hospital, Chiayi 62247, Taiwan, R.O.C.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Su
authors.affiliation: Department of Hematological Oncology, Buddhist Dalin Tzu Chi Hospital, Chiayi 62247, Taiwan, R.O.C.
authors.forename: Chih-Chia
authors.initials: CC
authors.lastname: Yu
authors.affiliation: Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 11221, Taiwan, R.O.C.
authors.forename: Fei-Ting
authors.initials: FT
authors.lastname: Hsu
authors.affiliation: Institute of Traditional Medicine, National Yang-Ming University, Taipei 11221, Taiwan, R.O.C.
authors.forename: Shu-Ling
authors.initials: SL
authors.lastname: Fu
authors.affiliation: Department of Biomedical Imaging and Radiological Sciences, National Yang-Ming University, Taipei 11221, Taiwan, R.O.C.
authors.forename: Jeng-Jong
authors.initials: JJ
authors.lastname: Hwang
authors.affiliation: Institute of Traditional Medicine, National Yang-Ming University, Taipei 11221, Taiwan, R.O.C.
authors.forename: Ling-Chien
authors.initials: LC
authors.lastname: Hung
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi Hospital, Chiayi 62247, Taiwan, R.O.C.
authors.forename: Moon-Sing
authors.initials: MS
authors.lastname: Lee
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi Hospital, Chiayi 62247, Taiwan, R.O.C.
authors.forename: Wen-Yen
authors.initials: WY
authors.lastname: Chiou
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi Hospital, Chiayi 62247, Taiwan, R.O.C.
authors.forename: Hon-Yi
authors.initials: HY
authors.lastname: Lin
authors.affiliation: Department of Radiation Oncology, Buddhist Dalin Tzu Chi Hospital, Chiayi 62247, Taiwan, R.O.C.
authors.forename: Shih-Kai
authors.initials: SK
authors.lastname: Hung
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects* / Q000528:radiation effects*; D000071186:Beclin-1; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000528:radiation effects; D002460:Cell Line; D053938:DNA Fragmentation / Q000187:drug effects / Q000528:radiation effects; D000068338:Everolimus; D020287:In Situ Nick-End Labeling; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000235:genetics; D011827:Radiation; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D011878:Radiotherapy / Q000379:methods; D051381:Rats; D019893:Ribosomal Protein S6 Kinases / Q000235:genetics / Q000378:metabolism; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology; D014162:Transfection
chemical_list: D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D002352:Carrier Proteins; D000068338:Everolimus; D047908:Intracellular Signaling Peptides and Proteins; D008869:Microtubule-Associated Proteins; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D011838:Radiation-Sensitizing Agents; D019893:Ribosomal Protein S6 Kinases; D020123:Sirolimus; C512829:Becn1 protein, rat; C499526:Eif4ebp1 protein, rat; C526109:Anxa3 protein, rat; C526901:Rps6kb1 protein, rat