title: Combination effects of arsenic trioxide and fibroblast growth factor receptor inhibitor in squamous cell lung carcinoma.
abstract: Lung cancer remains the top cancer killer worldwide, with squamous cell carcinoma (SCC) as the second commonest histologic subtype. Arsenic trioxide (ATO) was previously shown to suppress growth of lung cancer. Fibroblast growth factor receptor (FGFR) amplification was recently demonstrated in lung SCC, with specific FGFR inhibitor (e.g. PD173074) developed as a potential targeted therapy. Therefore the combination effects of ATO and PD173074 in SCC was studied.
  
  
  
  The combination of ATO/PD173074 was studied in a proof-of-principle model using a lung SCC cell line with FGFR1 overexpression: SK-MES-1. The effects of ATO and/or PD173074 on cell viability and protein expression were studied by MTT assay and Western blot respectively. Cell cycle analysis, phosphatidylserine externalization and mitochondrial membrane depolarization were monitored by flow cytometry. FGFR1 knockdown was performed with siRNAs. Proteasome inhibitor (MG-132) was used to study the degradation mechanism. In vivo effect of ATO and/or PD173074 was investigated using a nude mice xenograft model.
  
  
  
  Combined ATO/PD173074 reduced cell viability along with increased sub-G1 population, phosphatidylserine externalization and mitochondrial membrane depolarization more significantly than single treatments. Downregulation of FGFR1, p-Akt, Akt, p-Src, Src, p-c-Raf, c-Raf, Erk and survivin as well as upregulation of p-Erk and cleaved PARP were observed upon ATO and/or PD treatment. MG-132 partially reversed the degradation of Akt, Src, c-Raf and Erk induced by ATO/PD, suggestive of ubiquitin-independent proteasome-dependent degradation. However, the mechanism of FGFR1 downregulation remained unknown. Downregulation of FGFR1, Akt, Src, c-Raf and Erk as well as cleaved PARP elevation induced by ATO and/or PD were confirmed in vivo.
  
  
  
  Massive protein degradation (FGFR1, Akt, Src, c-Raf and Erk) was induced by ATO and/or PD173074 treatment mainly mediated by activation of proteasomal degradation in SCC cell line SK-MES-1 in vitro and in vivo.
authors: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China.
authors: Sze-Kwan
authors: SK
authors: Lam
authors: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China.
authors: Leanne Lee
authors: LL
authors: Leung
authors: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China.
authors: Yuan-Yuan
authors: YY
authors: Li
authors: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China.
authors: Chun-Yan
authors: CY
authors: Zheng
authors: Division of Respiratory Medicine, Department of Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong SAR, China. Electronic address: jhocm@hku.hk.
authors: James Chung-Man
authors: JC
authors: Ho
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology* / Q000627:therapeutic use; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D045744:Cell Line, Tumor / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D004359:Drug Therapy, Combination / Q000379:methods*; D005260:Female; D007976:Leupeptins / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000188:drug therapy* / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D010087:Oxides / Q000494:pharmacology* / Q000627:therapeutic use; D011743:Pyrimidines / Q000494:pharmacology*; D051496:Receptor, Fibroblast Growth Factor, Type 1 / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays / Q000379:methods
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D010087:Oxides; C115711:PD 173074; D011743:Pyrimidines; C496348:FGFR1 protein, human; D051496:Receptor, Fibroblast Growth Factor, Type 1; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; D000077237:Arsenic Trioxide
keywords: Apoptosis; Arsenic trioxide; FGFR1 inhibitor; Proteasome degradation system; Squamous cell lung carcinoma; Xenograft