title: Prediction of synergistic antitumour effect of gefitinib and radiation in vitro.
abstract: OBJECTIVE
  This study investigated the potential of a series of biomarkers in predicting the interaction of gefitinib and radiation in tumour treatment.
  
  
  METHODS
  In vitro assays were performed on human skin cancer and melanoma cell lines. The antitumour effect was measured by using the MTT assay. Total and phosphorylated epidermal growth factor receptor (EGFR and pEGFR) levels were determined by cell-based ELISA.
  
  
  RESULTS
  Gefitinib and radiation interacted to inhibit tumour cell proliferation in a cell line-dependent manner. Synergism dominated the interaction (76%), followed by additive effect (20%) and a few instances of antagonism (4%). Correlation analyses revealed a significant correlation between the median combination index (CI) and gefitinib IC₅₀, radiation ID₅₀, gefitinib- or EGF-modulated EGFR and/or pEGFR expression (all p ≤ 0.05).
  
  
  CONCLUSIONS
  A potential role of gefitinib efficacy, radiation efficacy and gefitinib- or EGF-modulated EGFR and/or pEGFR expression in the prediction of interaction between gefitinib and radiation is supported.
authors.affiliation: ANSTO LifeSciences, Australian Nuclear Science and Technology Organisation, Locked Bag 2001 Kirrawee DC, NSW 2232, Australia. hql@ansto.gov.au
authors.forename: Hui Qiang
authors.initials: HQ
authors.lastname: Lin
authors.forename: Haider
authors.initials: H
authors.lastname: Meriaty
authors.forename: Andrew
authors.initials: A
authors.lastname: Katsifis
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004797:Enzyme-Linked Immunosorbent Assay; D066246:ErbB Receptors / Q000378:metabolism*; D000077156:Gefitinib; D006801:Humans; D066298:In Vitro Techniques; D008545:Melanoma / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D011799:Quinazolines / Q000494:pharmacology*; D011839:Radiation, Ionizing; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology*
chemical_list: D000970:Antineoplastic Agents; D011799:Quinazolines; D066246:ErbB Receptors; D000077156:Gefitinib