title: Monitoring of gefitinib sensitivity with radioiodinated PHY based on EGFR expression.
abstract: Epidermal growth factor receptor (EGFR) is attractive target for tumor diagnosis and therapy, as it is specifically and abundantly expressed in tumor cells. EGFR-tyrosine kinase (TK) inhibitors such as gefitinib and erlotinib are widely used in the treatment of non-small cell lung cancer (NSCLC). In this study, we investigated whether radioiodinated 4-(3-iodo-phenoxy)-6,7-diethoxy-quinazoline (PHY), which is a candidate EGFR-TK imaging agent for single photon emission computed tomography (SPECT) is able to predict gefitinib sensitivity. We used four NSCLC cell lines-A549 (wild-type EGFR), H1650 (mutant EGFR; del E746_A750), H1975 (mutant EGFR; L858R, T790M) and H3255 (mutant EGFR; L858R)-and one epidermoid carcinoma cell line, A431 (wild-type EGFR). Cell proliferation assay and Western blotting revealed that A431 and H3255 with high EGFR expression showed high sensitivity to gefitinib. On the other hand, A549, H1650 and H1975 showed much lower sensitivity to gefitinib. The blocking study revealed that gefitinib decreased tumor uptake in (125)I-PHY in A431-bearing mice. Moreover, in vivo tumor uptake of (125)I-PHY was correlated with the IC50 of gefitinib for cell proliferation. In the present study, tumor uptake of (125)I-PHY was correlated with the gefitinib sensitivity and this uptake was based on expression levels of EGFR, but not on mutation status. Although the mutation status is the most important factor for predicting gefitinib sensitivity, the abundant expression of EGFR is essential for therapy with EGFR-TK inhibitors. Therefore, radioiodinated PHY is a potential imaging agent to predict gefitinib sensitivity based on EGFR expression levels though further modifications of the imaging agent is needed to accurately estimate the mutation status.
authors.affiliation: Division of Functional Imaging, National Cancer Center Hospital East.
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Yoshimoto
authors.forename: Masahiko
authors.initials: M
authors.lastname: Hirata
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Kanai
authors.forename: Sadahiro
authors.initials: S
authors.lastname: Naka
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Nishii
authors.forename: Shinya
authors.initials: S
authors.lastname: Kagawa
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kawai
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Ohmomo
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D000077156:Gefitinib; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009154:Mutation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D011799:Quinazolines / Q000494:pharmacology* / Q000627:therapeutic use; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
chemical_list: D000970:Antineoplastic Agents; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D066246:ErbB Receptors; D000077156:Gefitinib