PKD2 and PKD3 Promote Prostate Cancer Cell Invasion via uPA by Shifting Balance Between NF-κB and HDAC1

Abstract

Although protein kinase D3 (PKD3) has been shown to contribute to prostate cancer cell growth and survival, the role of PKD in prostate cancer cell motility remains unclear. Here, we show that PKD2 and PKD3 promote nuclear factor-kappaB (NF-κB) signaling and urokinase-type plasminogen activator (uPA) expression/activation, which are critical to prostate cancer cell invasion. Silencing of endogenous PKD2 and/or PKD3 markedly decreased prostate cancer cell migration and invasion, reduced uPA and uPA receptor (uPAR) expression, and increased plasminogen activator inhibitor-2 (PAI-2) expression. These results were further substantiated by the finding that PKD2 and PKD3 promoted the activity of uPA and matrix metalloproteinase (MMP)-9. Furthermore, depletion of PKD2 and/or PKD3 decreased the binding of p65 NF-κB to the uPA promoter, suppressing transcriptional activation of uPA. Endogenous PKD2 and PKD3 interacted with IκB kinase β (IKKβ); PKD2 mainly regulated the pIKK-IκB-p65 nuclear translocation cascade and phosphorylation of Ser276 on p65, while PKD3 was responsible for the phosphorylation of Ser536 on p65. Conversely, inhibition of uPA transactivation by PKD3 silencing was rescued by constitutive Ser536 phosphorylation, and reduced tumor cell invasion resulting from PKD2 or PKD3 silencing was rescued by ectopic expression of p65. Interestingly, PKD3 interacted with histone deacetylase 1 (HDAC1), suppressing HDAC1 expression and decreasing its binding to the uPA promoter. Moreover, depletion of HDAC1 resulted in recovery of uPA transactivation in PKD3-knockdown cells. Taken together, these data suggest that PKD2 and PKD3 may coordinate to promote prostate cancer cell invasion through p65 NF-κB- and HDAC1-mediated expression and activation of uPA.