1alpha,25-Dihydroxyvitamin D(3) antiproliferative actions involve vitamin D receptor-mediated activation of MAPK pathways and AP-1/p21(waf1) upregulation in human osteosarcoma

Cancer Lett. 2007 Aug 28;254(1):75-86. doi: 10.1016/j.canlet.2007.02.013. Epub 2007 Apr 6.


The molecular mechanisms underlying antiproliferative actions of the steroid 1alpha,25-dihydroxy vitamin D(3) (1,25D) in human osteosarcoma cells are known only partially. To better understand the signaling involved in 1,25D anti-tumorigenic properties in bone, we stably silenced vitamin D receptor (VDR) expression in the human osteosarcoma SaOS-2 cell line. We found that 1,25D treatment reduced cell proliferation by approximately 25% after 3 days only in SaOS-2 cells expressing native levels of VDR protein, and involved activation of MAPK/AP-1/p21(waf1) pathways. Both sustained (3 days) and transient (15min) 1,25D treatment activated JNK and ERK1/2 MAPK signaling in a nongenomic VDR-dependent manner. However, only sustained exposure to hormone led to upregulation of p21 and subsequent genomic control of the cell cycle. Specific blockade of MEK1/MEK2 cascade upstream from ERK1/2 abrogated 1,25D activation of AP-1 and p21, and subsequent antiproliferative effects, even in the presence of a nuclear VDR. We conclude that 1,25D-induced inhibition of human osteosarcoma cell proliferation occurs via sustained activation of JNK and MEK1/MEK2 pathways downstream of nongenomic VDR signaling that leads to upregulation of a c-Jun/c-Fos (AP-1) complex, which in turn modulates p21(waf1) gene expression. Our results demonstrate a cross-talk between 1,25D/VDR nongenomic and genomic signaling at the level of MAP kinase activation that leads to reduction of cell proliferation in human osteosarcoma cells.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Blotting, Western
  • Butadienes / pharmacology
  • Cell Line, Tumor
  • Cell Proliferation / drug effects*
  • Cyclin-Dependent Kinase Inhibitor p21 / genetics
  • Cyclin-Dependent Kinase Inhibitor p21 / metabolism*
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Humans
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • MAP Kinase Signaling System / drug effects
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / metabolism*
  • Models, Biological
  • Nitriles / pharmacology
  • Proto-Oncogene Proteins c-fos / metabolism
  • RNA, Small Interfering / genetics
  • Receptors, Calcitriol / genetics
  • Receptors, Calcitriol / metabolism*
  • Time Factors
  • Transcription Factor AP-1 / genetics
  • Transcription Factor AP-1 / metabolism*
  • Transfection
  • Up-Regulation / drug effects
  • Vitamin D / analogs & derivatives
  • Vitamin D / pharmacology*


  • Butadienes
  • CDKN1A protein, human
  • Cyclin-Dependent Kinase Inhibitor p21
  • Enzyme Inhibitors
  • Nitriles
  • Proto-Oncogene Proteins c-fos
  • RNA, Small Interfering
  • Receptors, Calcitriol
  • Transcription Factor AP-1
  • U 0126
  • dihydroxy-vitamin D3
  • Vitamin D
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases