title: Irreversible EGFR inhibitor EKB-569 targets low-LET γ-radiation-triggered rel orchestration and potentiates cell death in squamous cell carcinoma.
abstract: EKB-569 (Pelitinib), an irreversible EGFR tyrosine kinase inhibitor has shown potential therapeutic efficiency in solid tumors. However, cell-killing potential in combination with radiotherapy and its underlying molecular orchestration remain to be explored. The objective of this study was to determine the effect of EKB-569 on ionizing radiation (IR)-associated NFκB-dependent cell death. SCC-4 and SCC-9 cells exposed to IR (2Gy) with and without EKB-569 treatment were analyzed for transactivation of 88 NFκB pathway molecules, NFκB DNA-binding activity, translation of the NFκB downstream mediators, Birc1, 2 and 5, cell viability, metabolic activity and apoptosis. Selective targeting of IR-induced NFκB by EKB-569 and its influence on cell-fate were assessed by overexpressing (p50/p65) and silencing (ΔIκBα) NFκB. QPCR profiling after IR exposure revealed a significant induction of 74 NFκB signal transduction molecules. Of those, 72 were suppressed with EKB-569. EMSA revealed a dose dependent inhibition of NFκB by EKB-569. More importantly, EKB-569 inhibited IR-induced NFκB in a dose-dependent manner, and this inhibition was sustained up to at least 72 h. Immunoblotting revealed a significant suppression of IR-induced Birc1, 2 and 5 by EKB-569. We observed a dose-dependent inhibition of cell viability, metabolic activity and apoptosis with EKB-569. EKB-569 significantly enhanced IR-induced cell death and apoptosis. Blocking NFκB improved IR-induced cell death. Conversely, NFκB overexpression negates EKB-569 -induced cell-killing. Together, these pre-clinical data suggest that EKB-569 is a radiosensitizer of squamous cell carcinoma and may mechanistically involve selective targeting of IR-induced NFκB-dependent survival signaling. Further pre-clinical in-vivo studies are warranted.
authors.affiliation: Department of Otolaryngology, Head and Neck Surgery, University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Natarajan
authors.initials: N
authors.lastname: Aravindan
authors.forename: Charles R
authors.initials: CR
authors.lastname: Thomas
authors.forename: Sheeja
authors.initials: S
authors.lastname: Aravindan
authors.forename: Aswathi S
authors.initials: AS
authors.lastname: Mohan
authors.forename: Jamunarani
authors.initials: J
authors.lastname: Veeraraghavan
authors.forename: Mohan
authors.initials: M
authors.lastname: Natarajan
mesh_terms: D000634:Aminoquinolines / Q000494:pharmacology*; D000814:Aniline Compounds / Q000494:pharmacology*; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000473:pathology*; D016923:Cell Death / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D004273:DNA, Neoplasm / Q000378:metabolism; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D005720:Gamma Rays; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D018499:Linear Energy Transfer; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism*; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D015854:Up-Regulation / Q000187:drug effects / Q000528:radiation effects
chemical_list: D000634:Aminoquinolines; D000814:Aniline Compounds; D004273:DNA, Neoplasm; D016328:NF-kappa B; D009363:Neoplasm Proteins; D047428:Protein Kinase Inhibitors; D020569:Proto-Oncogene Proteins c-rel; D011838:Radiation-Sensitizing Agents; D066246:ErbB Receptors; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C413879:EKB 569