title: The phosphatase inhibitor menadione (vitamin K3) protects cells from EGFR inhibition by erlotinib and cetuximab.
abstract: OBJECTIVE
  Skin toxicity is the main side effect of epidermal growth factor receptor (EGFR) inhibitors, often leading to dose reduction or discontinuation. We hypothesized that phosphatase inhibition in the skin keratinocytes may prevent receptor dephosphorylation caused by EGFR inhibitors and be used as a new potential strategy for the prevention or treatment of this side effect.
  
  
  METHODS
  Menadione (Vitamin K3) was used as the prototype compound to test our hypothesis. HaCat human skin keratinocyte cells and A431 human squamous carcinoma cells were used. EGFR inhibition was measured by Western blotting and immunofluorescence. Phosphatase inhibition and reactive oxygen species (ROS) generation were measured by standard ELISA and fluorescence assays.
  
  
  RESULTS
  Menadione caused significant and reversible EGFR activation in a dose-dependent manner starting at nontoxic concentrations. EGFR activation by menadione was associated with reversible protein tyrosine phosphatase inhibition, which seemed to be mediated by ROS generation as exposure to antioxidants prevented both menadione-induced ROS generation and phosphatase inhibition. Short-term coincubation of cells with nontoxic concentrations of menadione and the EGFR inhibitors erlotinib or cetuximab prevented EGFR dephosphorylation. Seventy-two-hour coincubation of cells with the highest nontoxic concentration of menadione and erlotinib provided for a fourfold cell growth inhibitory protection in HaCat human keratinocyte cells.
  
  
  CONCLUSIONS
  Menadione at nontoxic concentrations causes EGFR activation and prevents EGFR dephosphorylation by erlotinib and cetuximab. This effect seems to be mediated by ROS generation and secondary phosphatase inhibition. Mild oxidative stress in skin keratinocytes by topical menadione may protect the skin from the toxicity secondary to EGFR inhibitors without causing cytotoxicity.
authors.affiliation: Department of Oncology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York 10467, USA. rperezso@montefiore.org
authors.forename: Roman
authors.initials: R
authors.lastname: Perez-Soler
authors.forename: Yiyu
authors.initials: Y
authors.lastname: Zou
authors.forename: Tianhong
authors.initials: T
authors.lastname: Li
authors.forename: Yi He
authors.initials: YH
authors.lastname: Ling
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000009:adverse effects / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D048708:Cell Growth Processes / Q000187:drug effects; D000068818:Cetuximab; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000069347:Erlotinib Hydrochloride; D016193:G1 Phase / Q000187:drug effects; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D010766:Phosphorylation / Q000187:drug effects; D017027:Protein Tyrosine Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011799:Quinazolines / Q000009:adverse effects / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D012867:Skin / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D024483:Vitamin K 3 / Q000494:pharmacology*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D011799:Quinazolines; D017382:Reactive Oxygen Species; D024483:Vitamin K 3; D000069347:Erlotinib Hydrochloride; D066246:ErbB Receptors; D017027:Protein Tyrosine Phosphatases; D000068818:Cetuximab