title: DICKKOPF-4 activates the noncanonical c-Jun-NH2 kinase signaling pathway while inhibiting the Wnt-canonical pathway in human renal cell carcinoma.
abstract: BACKGROUND
  To the authors' knowledge, the functional significance of the Wnt antagonist dickkopf homolog 4 (DKK4) has not been investigated previously in renal cancer.
  
  
  METHODS
  The authors initially observed that the expression of DKK4 was significantly higher in renal cancer tissues compared with adjacent normal kidney tissues. To assess the function of DKK4, stable DKK4-transfected cells were established, and functional analyses were performed, including a T-cell factor/lymphoid enhancer factor (TCF/LEF) reporter assay and tests for cell viability, colony formation, apoptosis, cell cycle, invasive capability, wound-healing capability, and in vivo tumor growth.
  
  
  RESULTS
  The relative TCF/LEF activity was significantly lower in DKK4-transfected cells compared with empty vector, and nuclear β-catenin expression was decreased in DKK4 transfectants. In addition, expression levels of the β-catenin downstream effector proteins cyclin D1 and c-Myc were decreased in DKK4 transfectants. However, greater invasiveness and migration were observed in stably transfected DKK4 cells. Increased growth of DKK4-transfected tumors also was observed in nude mice. Members of the Wnt noncanonical/c-Jun-NH2 kinase (JNK) signaling pathway also were effected, such as c-Jun, which had significantly increased expression and phosphorylation in DKK4-stable transfectants, and matrix metalloproteinase-2, which had significantly increased expression in DKK4-stable transfectants.
  
  
  CONCLUSIONS
  This is the first study to indicate that DKK4 expression is increased in renal cancer tissues and that DKK4 activates the noncanonical JNK signaling pathway while inhibiting the Wnt-canonical pathway.
authors.affiliation: Department of Urology, San Francisco Veterans Affairs Medical Center and University of California at San Francisco, San Francisco, California 94121, USA.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hirata
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hinoda
authors.forename: Shahana
authors.initials: S
authors.lastname: Majid
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.forename: Mohd S
authors.initials: MS
authors.lastname: Zaman
authors.forename: Koji
authors.initials: K
authors.lastname: Ueno
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakajima
authors.forename: Z Laura
authors.initials: ZL
authors.lastname: Tabatabai
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Ishii
authors.forename: Rajvir
authors.initials: R
authors.lastname: Dahiya
mesh_terms: D000328:Adult; D000368:Aged; D002292:Carcinoma, Renal Cell / Q000378:metabolism*; D045744:Cell Line, Tumor; D002999:Clone Cells; D005260:Female; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D007680:Kidney Neoplasms / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D051153:Wnt Proteins / Q000378:metabolism*
chemical_list: C442333:DKK4 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D051153:Wnt Proteins; D048031:JNK Mitogen-Activated Protein Kinases