Purpose: We investigated the effect of manipulating endogenous BMP-7 expression on the invasion and motility of prostate cancer cells and the resulting effect on its antagonists using a ribozyme transgene.
Materials and methods: A hammerhead ribozyme transgene was synthesized and cloned into a mammalian expression vector (pcDNA3.1/nt-GFP-TOPO). PC-3 cells (American Type Culture Collection, Manassas, Virginia) were transfected with the ribozyme transgene (PC-3(DeltaBMP7)) or with an empty plasmid (PC-3(pcDNA/GFP)) by electroporation. Invasion and motility were accessed by in vitro invasion and motility assays.
Results: The ribozyme decreased BMP-7 expression at the mRNA and protein levels in PC-3 cells. Invasive potential was significantly increased following the loss of BMP-7 expression. The mean +/- SD invading cell number for PC-3(DeltaBMP7) was 231.3 +/- 28.6 vs 7.1 +/- 4.4 for the WT cell line PC-3(WT) and 2.7 +/- 2 for PC-3(pcDNA/GFP) (each p <0.001). BMP-7 knockdown in PC-3 cells significantly increased motility with a migrating cell number for PC-3(DeltaBMP7) of 24 +/- 7.5 compared with 10.2 +/- 4.5 for PC-3(WT) and 11.3 +/- 7.5 for PC-3(pcDNA/GFP) (p <0.01 and 0.011, respectively). The change in motility was seen together with changes in the cellular location of paxillin and focal adhesion kinase (p125(FAK)). Interestingly the loss of BMP-7 resulted in decreased noggin and follistatin expression.
Conclusions: The loss of endogenous BMP-7 from prostate cancer cells is associated with increased invasiveness and motility, which appears to be facilitated by changes in the level of the BMP antagonists noggin and follistatin. Endogenous BMP-7 has an important role in controlling noggin and follistatin expression.