title: Off-target response of a Wip1 chemical inhibitor in skin keratinocytes.
abstract: BACKGROUND
  The wild type p53 inducible phosphatase (Wip1) plays an important role in modulating not only stress responses by various environmental stresses, but when overexpressed it also impairs the intrinsic tumor surveillance networks that are frequently found in a number of cancers including skin cancers. As a result, using a pharmacological inhibitor of Wip1 has been suggested to be a novel chemotherapeutic approach to recover the innate tumor surveillance in a variety of cancers.
  
  
  OBJECTIVE
  We studied the effect of a pharmacological inhibitor of Wip1 in skin keratinocytes, under a ultra-violet (UV) stress condition.
  
  
  METHODS
  A human keratinocyte cell line or human epidermal keratinocytes were exposed to UV, with or without the sole commercially available chemical inhibitor of Wip1, CCT007093; subsequently, we determined the diverse stress responses, including apoptosis and the activation of stress signaling.
  
  
  RESULTS
  We demonstrate that the Wip1 inhibitor unexpectedly attenuated the UV-mediated apoptotic response in skin keratinocytes, as a consequence of attenuated JNK activation and reduced H2AX phosphorylation in both, skin keratinocytes and a Wip1-null cell model. On the other hand, the loss of Wip1 expression, either by knockout or knockdown in mice or human keratinocytes respectively, promoted apoptosis and potentiated H2AX phosphorylation following UV treatment. Of note, CCT007093 treatment appeared to promote apoptosis in breast cancer cells and skin transformed keratinocytes that ectopically expressed Wip1, demonstrating that the effect of CCT007093 differs based on the level of Wip1 expression.
  
  
  CONCLUSIONS
  Thus, our studies suggest that the development of a more potent and specific Wip1 inhibitor is necessary to achieve the desired chemotherapeutic potential and to avoid off-target effects.
authors.affiliation: Department of Life Science, Sogang University, Seoul, Republic of Korea.
authors.forename: Ji-Seon
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Life Science, Sogang University, Seoul, Republic of Korea.
authors.forename: Jeong-Rak
authors.initials: JR
authors.lastname: Park
authors.affiliation: Department of Life Science, Sogang University, Seoul, Republic of Korea.
authors.forename: Ok-Seon
authors.initials: OS
authors.lastname: Kwon
authors.affiliation: Graduate School of Biomedical Science and Engineering, College of Medicine, Hanyang University, Seoul, Republic of Korea.
authors.forename: Hyongbum
authors.initials: H
authors.lastname: Kim
authors.affiliation: Department of Biochemistry and Molecular & Cellular Biology, Georgetown University, Washington, DC, USA.
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Fornace
authors.affiliation: Department of Life Science, Sogang University, Seoul, Republic of Korea. Electronic address: hjcha@sogang.ac.kr.
authors.forename: Hyuk-Jin
authors.initials: HJ
authors.lastname: Cha
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000737:chemistry; D000970:Antineoplastic Agents / Q000737:chemistry; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D003517:Cyclopentanes / Q000737:chemistry*; D005786:Gene Expression Regulation; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism; D061986:MCF-7 Cells; D051379:Mice; D008822:Mice, Transgenic; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000235:genetics; D000071636:Protein Phosphatase 2C; D012867:Skin / Q000187:drug effects* / Q000378:metabolism; D012878:Skin Neoplasms / Q000188:drug therapy*; D013876:Thiophenes / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D017304:Annexin A5; D000970:Antineoplastic Agents; C000591540:CCT007093; D003517:Cyclopentanes; D013876:Thiophenes; C000607458:PPM1D protein, human; D010749:Phosphoprotein Phosphatases; C000607468:Ppm1d protein, mouse; D000071636:Protein Phosphatase 2C; D053148:Caspase 3
keywords: Apoptosis; CCT007093; JNK; Keratinocytes; Ultra-violet radiation; Wip1