title: PF-00477736 mediates checkpoint kinase 1 signaling pathway and potentiates docetaxel-induced efficacy in xenografts.
abstract: OBJECTIVE
  Checkpoint kinase 1 (Chk1) plays a critical role in the activation of mitotic spindle checkpoint and DNA damage checkpoint. We examined the preclinical use of the Chk1 inhibitor PF-00477736 as a docetaxel-sensitizing agent. Specifically, we investigated the correlation between PF-00477736-mediated modulation of biomarkers and the sensitization of docetaxel efficacy.
  
  
  METHODS
  In vitro and in vivo studies using COLO205 and other cell lines were done to assess PF-00477736-induced enhancement of docetaxel efficacy and effects on associated biomarkers.
  
  
  RESULTS
  PF-00477736 significantly enhanced the docetaxel-induced efficacy in tumor cells and xenografts. Docetaxel induced dose- and time-dependent increase in the levels of phosphorylated Chk1 (Ser(345)), phosphorylated histone H3 (Ser(10)), and gammaH2AX foci and promoted the cytoplasmic localization of phosphorylated Cdc25C (Ser(216)). PF-00477736 cotreatment suppressed docetaxel-induced changes in phosphorylated histone H3 and cytoplasmic phosphorylated Cdc25C (Ser(216)) levels and concurrently sensitized the docetaxel-induced apoptosis. Docetaxel alone or in combination with PF-00477736 induced significant antiproliferative activity in xenografts, shown via [18F]FLT-PET imaging. However, changes in [18F]FLT uptake did not reflect the potentiation of docetaxel efficacy. In contrast, bioluminescence imaging showed that PF-00477736 sensitized docetaxel-induced suppression of tumor survival.
  
  
  CONCLUSIONS
  Docetaxel triggers mitotic spindle checkpoint activation at low concentrations and activates both the DNA damage checkpoint and the spindle checkpoint at high concentrations. In combination with docetaxel, PF-00477736 abrogates the mitotic checkpoint, as well as the DNA damage checkpoint, and results in sensitization to docetaxel. Chk1 inhibitor PF-00477736 offers a therapeutic potential for the enhancement of taxane therapy.
authors: Oncology Research Unit, Pfizer Global Research and Development, La Jolla Laboratories, San Diego, California, USA. cathy.zhang@pfizer.com
authors: Cathy
authors: C
authors: Zhang
authors: Zhengming
authors: Z
authors: Yan
authors: Cory L
authors: CL
authors: Painter
authors: Qin
authors: Q
authors: Zhang
authors: Enhong
authors: E
authors: Chen
authors: Maria E
authors: ME
authors: Arango
authors: Kyle
authors: K
authors: Kuszpit
authors: Kenneth
authors: K
authors: Zasadny
authors: Max
authors: M
authors: Hallin
authors: Jill
authors: J
authors: Hallin
authors: Anthony
authors: A
authors: Wong
authors: Dana
authors: D
authors: Buckman
authors: Guizhen
authors: G
authors: Sun
authors: Ming
authors: M
authors: Qiu
authors: Kenna
authors: K
authors: Anderes
authors: James G
authors: JG
authors: Christensen
mesh_terms: D000818:Animals; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D001570:Benzodiazepinones / Q000008:administration & dosage / Q000494:pharmacology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D000071877:Checkpoint Kinase 1; D015224:Dideoxynucleosides; D000077143:Docetaxel; D004357:Drug Synergism; D005462:Fluorine Radioisotopes; D006657:Histones / Q000378:metabolism; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*; D011720:Pyrazoles / Q000008:administration & dosage / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects*; D043823:Taxoids / Q000008:administration & dosage / Q000494:pharmacology; D014055:Tomography, Emission-Computed; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays; D020687:cdc25 Phosphatases / Q000378:metabolism
chemical_list: D001570:Benzodiazepinones; D015224:Dideoxynucleosides; D005462:Fluorine Radioisotopes; D006657:Histones; C532366:PF 00477736; D011720:Pyrazoles; D043823:Taxoids; D000077143:Docetaxel; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605869:Chek1 protein, mouse; C517010:Cdc25c protein, mouse; D020687:cdc25 Phosphatases