BMP-6 over-expression in prostate cancer is associated with increased Id-1 protein and a more invasive phenotype

J Pathol. 2008 Feb;214(3):394-404. doi: 10.1002/path.2292.

Abstract

Bone morphogenetic protein-6 (BMP-6) has been strongly implicated in prostate cancer development and bone metastasis. Our previous data showed that BMP-6 mRNA was absent in patients with benign prostatic hyperplasia, but evident in primary tumours with established secondary skeletal metastases. To examine the role of BMP-6 in prostate cancer progression, we have developed a BMP-6-regulatable, doxycycline-inducible gene expression system. BMP-6 induction by doxycycline addition led to increased levels of BMP-6 RNA and protein, associated with nuclear translocation of SMADs and activation of the downstream target gene Id-1. BMP-6 protein did not enhance the proliferation rate of PC3M cells but did significantly increase the rate of migration and invasion in both PC3M and DU145 cells. Increased metalloproteinase (MMP-1 and MMP-9) mRNA levels were also observed following BMP-6 induction. Luciferase reporter assays confirmed BMP-6-mediated activation of MMP-1 and MMP-9 promoters, indicating direct transcriptional activation of MMPs by BMP-6. BMP-6 stimulation also led to an increase in phosphorylation levels of MAPK proteins. We next examined the effects of BMP-6 on the downstream gene Id-1 in a cohort of prostate cancer patients. A tissue microarray (TMA) was constructed and samples stained for BMP-6 and Id-1 expression. We observed a significant increase in the intensity of staining of epithelial BMP-6 in the cancer cases compared to the benign cases (Mann-Whitney U test, p < 0.0005) and in the intensity of staining of epithelial Id-1 in the cancer cases compared to the benign cases (Mann-Whitney U test, p = 0.015). We further observed a significant positive correlation between epithelial staining for Id-1 and BMP-6 (p = 0.001) across all samples for both benign and cancer cases. These data demonstrate that BMP-6 promotes migration and invasion of prostate cancer cells, potentially through activation of Id-1 and MMP activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers, Tumor* / analysis
  • Bone Morphogenetic Protein 6
  • Bone Morphogenetic Proteins / analysis
  • Bone Morphogenetic Proteins / genetics*
  • Case-Control Studies
  • Cell Line, Tumor
  • Doxycycline / pharmacology
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic*
  • Humans
  • Immunohistochemistry
  • Inhibitor of Differentiation Protein 1 / analysis
  • Inhibitor of Differentiation Protein 1 / genetics*
  • Male
  • Matrix Metalloproteinase 1 / genetics
  • Matrix Metalloproteinase 9 / genetics
  • Neoplasm Invasiveness
  • Oligonucleotide Array Sequence Analysis
  • Phenotype
  • Prostate / metabolism
  • Prostatic Neoplasms / genetics
  • Prostatic Neoplasms / metabolism*
  • RNA, Messenger / analysis
  • Smad1 Protein / genetics
  • Statistics, Nonparametric
  • Transfection / methods

Substances

  • BMP6 protein, human
  • Biomarkers, Tumor
  • Bone Morphogenetic Protein 6
  • Bone Morphogenetic Proteins
  • ID1 protein, human
  • Inhibitor of Differentiation Protein 1
  • RNA, Messenger
  • Smad1 Protein
  • Matrix Metalloproteinase 9
  • Matrix Metalloproteinase 1
  • Doxycycline