Interplay of PKD3 with SREBP1 Promotes Cell Growth via Upregulating Lipogenesis in Prostate Cancer Cells

Protein kinase D (PKD) has been implicated in cancer cell survival, proliferation, migration and angiogenesis. However, it is still unknown whether PKD regulates cell proliferation through lipid metabolism in cancer cells. Here we report a novel function of PKD3, a member of PKD family, in regulating of prostate cancer cell proliferation by modulation of SREBP1-mediated de novo lipogenesis. We show that silencing of PKD3 significantly reduces lipid content and expression of the lipogenic genes encoding FASN and ATP-citrate lyase (ACLY). Moreover, endogenous PKD3 interacts with sterol regulatory element binding protein 1(SREBP1) in DU145 cells. Interestingly, PKD3 silencing decreases not only the level of matured-SREBP1 (68KD) but also the binding of SREBP1 to the promoter of fasn gene. In addition, overexpression of SREBP1 reverses the suppression of cell growth caused by PKD3 depletion. Finally, immune-histochemical staining indicate that PKD3 expression is positively correlated with expression of FASN and SREBP1 in prostate cancers. Taken together, these data suggest that targeting PKD3-mediated de novo lipogenesis may be a potential therapeutic approach to block prostate cancer progression.