title: Inhibitors of EGFR signaling retard cytotoxicity of fenretinide in rat gliosarcoma cells.
abstract: OBJECTIVE
  Fenretinide, 4-(N-hydroxyphenyl) retinamide, (4-HPR) is a well tolerated analog of alltrans retinoic acid. The gangliosideGM3, is a non-specific inhibitor of EGF receptor autophosphorylation (EGFR-phos). Both compounds were found preferentially cytotoxic to malignant and proliferating cells when compared to non-proliferating normal brain cells. Some of the small molecule inhibitors of EGFR-phos are also known to inhibit growth of brain tumors at relatively non-toxic doses. The purpose of this investigation was to evaluate if 4-HPR and inhibitors of EGFR-phos could be used together in the treatment of brain tumors.
  
  
  METHODS
  The 9L rat gliosarcoma cells were treated in vitro with 4-HPR either alone or in combination with the non-specific or specific inhibitors of EGFR-phos, GM3 or AG-1478, respectively. The relative viability of the control and treated cells was determined using 3-(4,5-imethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The experimental data were analyzed for statistical significance.
  
  
  RESULTS
  In contrast to the expected additive/synergistic effect on cell growth inhibition, the sub-toxic and toxic concentrations of 4-HPR protected GM3 treated cells. The viable cells were 3.86 times higher following GM3 plus 4-HPR treatments compared to GM3 treatment alone. Additionally, a specific inhibitor of EGFR-phos signaling, AG-1478 caused a concentration dependent protection of cells from the toxicity of 4-HPR. Our results show counteracting cytotoxic responses of 4-HPR and EGFR-phos inhibitors when used together in 9L rat gliosarcoma cells.
authors.affiliation: Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA.
authors.forename: Ayesha
authors.initials: A
authors.lastname: Zaheer
authors.forename: Shailendra K
authors.initials: SK
authors.lastname: Sahu
authors.forename: Vincent C
authors.initials: VC
authors.lastname: Traynelis
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D066246:ErbB Receptors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017313:Fenretinide / Q000494:pharmacology*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D017313:Fenretinide; D066246:ErbB Receptors