BMP-6 over-expression in prostate cancer is associated with increased Id-1 protein and a more invasive phenotype.
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.
Darby
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Surgical Oncology Laboratory, Northern Institute for Cancer Research, Newcastle University, Medical School, North Terrace, Newcastle upon Tyne NE2 4HH, UK.
Cross
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Brown
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Hamdy
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Robson
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D014408:Biomarkers, Tumor / Q000032:analysis; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins / Q000032:analysis / Q000235:genetics*; D016022:Case-Control Studies; D045744:Cell Line, Tumor; D004318:Doxycycline / Q000494:pharmacology; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D051798:Inhibitor of Differentiation Protein 1 / Q000032:analysis / Q000235:genetics*; D008297:Male; D020781:Matrix Metalloproteinase 1 / Q000235:genetics; D020780:Matrix Metalloproteinase 9 / Q000235:genetics; D009361:Neoplasm Invasiveness; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D011467:Prostate / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051898:Smad1 Protein / Q000235:genetics; D018709:Statistics, Nonparametric; D014162:Transfection / Q000379:methods
C525816:BMP6 protein, human; D014408:Biomarkers, Tumor; D055418:Bone Morphogenetic Protein 6; D019485:Bone Morphogenetic Proteins; C497453:ID1 protein, human; D051798:Inhibitor of Differentiation Protein 1; D012333:RNA, Messenger; D051898:Smad1 Protein; D020780:Matrix Metalloproteinase 9; D020781:Matrix Metalloproteinase 1; D004318:Doxycycline