title: Phosphatidylinositide 3-kinase (PI3K) and PI3K-related kinase (PIKK) activity contributes to radioresistance in thyroid carcinomas.
abstract: Anaplastic (ATC) and certain follicular thyroid-carcinomas (FTCs) are radioresistant. The Phosphatidylinositide 3-kinase (PI3K) pathway is commonly hyperactivated in thyroid-carcinomas. PI3K can modify the PI3K-related kinases (PIKKs) in response to radiation: How PIKKs interact with PI3K and contribute to radioresistance in thyroid-carcinomas is unknown. Further uncertainties exist in how these interactions function under the radioresistant hypoxic microenvironment. Under normoxia/anoxia, ATC (8505c) and FTC (FTC-133) cells were irradiated, with PI3K-inhibition (via GDC-0941 and PTEN-reconstitution into PTEN-null FTC-133s) and effects on PIKK-activation, DNA-damage, clonogenic-survival and cell cycle, assessed. FTC-xenografts were treated with 5 × 2 Gy, ± 50 mg/kg GDC-0941 (twice-daily; orally) for 14 days and PIKK-activation and tumour-growth assessed. PIKK-expression was additionally assessed in 12 human papillary thyroid-carcinomas, 13 FTCs and 12 ATCs. GDC-0941 inhibited radiation-induced activation of Ataxia-telangiectasia mutated (ATM), ATM-and Rad3-related (ATR) and DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Inhibition of ATM and DNA-PKcs was PI3K-dependent, since activation was reduced in PTEN-reconstituted FTC-133s. Inhibition of PIKK-activation was greater under anoxia: Consequently, whilst DNA-damage was increased and prolonged under both normoxia and anoxia, PI3K-inhibition only reduced clonogenic-survival under anoxia. GDC-0941 abrogated radiation-induced cell cycle arrest, an effect most likely linked to the marked inhibition of ATR-activation. Importantly, GDC-0941 inhibited radiation-induced PIKK-activation in FTC-xenografts leading to a significant increase in time taken for tumours to triple in size: 26.5 ± 5 days (radiation-alone) versus 31.5 ± 5 days (dual-treatment). PIKKs were highly expressed across human thyroid-carcinoma classifications, with ATM scoring consistently lower. Interestingly, some loss of ATM and DNA-PKcs was observed. These data provide new insight into the mechanisms of hypoxia-associated radioresistance in thyroid-carcinoma.
authors.affiliation: Hypoxia and Therapeutics Group, Manchester Pharmacy School, University of Manchester, Manchester, UK.|Current address: School of Clinical Medicine, Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, Cambridge, UK.
authors.forename: Natalie
authors.initials: N
authors.lastname: Burrows
authors.affiliation: Hypoxia and Therapeutics Group, Manchester Pharmacy School, University of Manchester, Manchester, UK.
authors.forename: Joseph
authors.initials: J
authors.lastname: Williams
authors.affiliation: Hypoxia and Therapeutics Group, Manchester Pharmacy School, University of Manchester, Manchester, UK.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Telfer
authors.affiliation: Experimental and Clinical Endocrinology, Medizinische Klinik I, Lubeck, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Resch
authors.affiliation: Translational Radiobiology Group, University of Manchester, Christie Hospital, NHS Trust, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Helen R
authors.initials: HR
authors.lastname: Valentine
authors.affiliation: Department of Histopathology, CSB1, Manchester Royal Infirmary, Manchester, UK.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Fitzmaurice
authors.affiliation: Translational Radiobiology Group, University of Manchester, Christie Hospital, NHS Trust, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Amanda
authors.initials: A
authors.lastname: Eustace
authors.affiliation: Translational Radiobiology Group, University of Manchester, Christie Hospital, NHS Trust, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Joely
authors.initials: J
authors.lastname: Irlam
authors.affiliation: Hypoxia and Therapeutics Group, Manchester Pharmacy School, University of Manchester, Manchester, UK.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Rowling
authors.affiliation: Martin Luther University of Halle-Wittenberg, Halle, Salle, Germany.
authors.forename: Cuong
authors.initials: C
authors.lastname: Hoang-Vu
authors.affiliation: Translational Radiobiology Group, University of Manchester, Christie Hospital, NHS Trust, Manchester Academic Health Science Centre, Manchester, UK.|Radiotherapy Related Research Group, Manchester Cancer Research Centre, Manchester, UK.
authors.forename: Catharine M
authors.initials: CM
authors.lastname: West
authors.affiliation: Experimental and Clinical Endocrinology, Medizinische Klinik I, Lubeck, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Brabant
authors.affiliation: Hypoxia and Therapeutics Group, Manchester Pharmacy School, University of Manchester, Manchester, UK.|Radiotherapy Related Research Group, Manchester Cancer Research Centre, Manchester, UK.
authors.forename: Kaye J
authors.initials: KJ
authors.lastname: Williams
mesh_terms: D000818:Animals; D002277:Carcinoma / Q000378:metabolism / Q000532:radiotherapy*; D002291:Carcinoma, Papillary / Q000378:metabolism / Q000532:radiotherapy; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D004789:Enzyme Activation; D005260:Female; D006657:Histones / Q000378:metabolism; D006801:Humans; D000860:Hypoxia; D007191:Indazoles / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D010100:Oxygen / Q000737:chemistry; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011836:Radiation Tolerance; D015398:Signal Transduction / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000378:metabolism / Q000532:radiotherapy*
chemical_list: C532162:2-(1H-indazol-4-yl)-6-(4-methanesulfonylpiperazin-1-ylmethyl)-4-morpholin-4-ylthieno(3,2-d)pyrimidine; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D007191:Indazoles; D013449:Sulfonamides; D019869:Phosphatidylinositol 3-Kinases; D010100:Oxygen
keywords: ATM; ATR; DNA-PKcs; PI3K; radioresistance