title: Targeting epidermal growth factor receptor/human epidermal growth factor receptor 2 signalling pathway by a dual receptor tyrosine kinase inhibitor afatinib for radiosensitisation in murine bladder carcinoma.
abstract: Given the promising control of bladder cancer achieved by combined chemotherapy/radiotherapy with selective transurethral resection, obstacles remain to the treatment of unresectable bladder cancer. The aim of this study was to determine whether targeting epidermal growth factor receptor (EGFR)/human epidermal growth factor receptor 2 (HER2) can radiosensitise a murine bladder tumour (MBT-2) cell line. Cell survival, expression of signal proteins and cell cycle changes in MBT-2 cells treated in vitro and in vivo with afatinib, an irreversible EGFR/HER2 inhibitor, plus radiotherapy were investigated by colony formation assay, Western blot assay and flow cytometry, respectively. Ectopic xenografts were established by subcutaneous injection of MBT-2 cells in C3H/HeN mice. Mice were randomised into 4 groups to receive afatinib (10mg/kg/day on day 1-7) and/or radiotherapy (15Gy on day 4). Positron emission tomography (PET) on day 8 was used to evaluate the early treatment response. Afatinib (200-1000nM) increased cell killing by radiation (0-10Gy). Pre-treatment of irradiated cells with afatinib inhibited radiation-activated HER2 and EGFR phosphorylation. As compared to either treatment alone, the combination increased the level of the cleavage form of poly (ADP-ribose) polymerase, the expression of phospho-γH2AX and the percentage of cells in subG1 phase (indicating enhanced induction of apoptosis), and decreased tumour metabolism and inhibited tumour growth by 64%. Afatinib has therapeutic value as a radiosensitiser of murine bladder cancer cells. The synergism between afatinib and radiation likely enhances DNA damage, leading to increased cell apoptosis.
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yu-Chieh
authors.initials: YC
authors.lastname: Tsai
authors.forename: Chih-Hsien
authors.initials: CH
authors.lastname: Yeh
authors.forename: Kai-Yuan
authors.initials: KY
authors.lastname: Tzen
authors.forename: Pei-Yin
authors.initials: PY
authors.lastname: Ho
authors.forename: Tsung-Fan
authors.initials: TF
authors.lastname: Tuan
authors.forename: Yeong-Shiau
authors.initials: YS
authors.lastname: Pu
authors.forename: Ann-Lii
authors.initials: AL
authors.lastname: Cheng
authors.forename: Jason Chia-Hsien
authors.initials: JC
authors.lastname: Cheng
mesh_terms: D000077716:Afatinib; D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003131:Combined Modality Therapy; D053960:DNA Breaks / Q000187:drug effects / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D066246:ErbB Receptors / Q000378:metabolism*; D016193:G1 Phase / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D051379:Mice; D008809:Mice, Inbred C3H; D009368:Neoplasm Transplantation; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D011878:Radiotherapy / Q000379:methods; D011897:Random Allocation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D001749:Urinary Bladder Neoplasms / Q000378:metabolism / Q000473:pathology / Q000628:therapy*
chemical_list: D000077716:Afatinib; D066246:ErbB Receptors; D011065:Poly(ADP-ribose) Polymerases; D051057:Proto-Oncogene Proteins c-akt; D011799:Quinazolines; D011838:Radiation-Sensitizing Agents; D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human