Speckle-type POZ protein suppresses lipid accumulation and prostate cancer growth by stabilizing fatty acid synthase.

Fatty acid synthase (FASN) is vital for maintaining lipid homeostasis in prostate cancer (PCa) cells, which have an increased rate of de novo fatty acid (FA) synthesis. Mutations in the gene encoding the tumor suppressor speckle-type POZ protein (SPOP), which is a E3 ubiquitin ligase, are a critical feature of PCa. Here, we provide evidence that FASN is a substrate of SPOP and that interaction of these proteins induces FASN ubiquitination and proteasome-dependent degradation. We showed that SPOP mutants commonly found in PCa cannot bind to FASN. Moreover, a decrease in SPOP levels upregulated FASN expression and triggered lipid accumulation in PCa cells. These results demonstrate that FASN is a crucial mediator of SPOP-induced inhibition of PCa cell growth. Our data provide evidence that SPOP regulates lipid metabolism by decreasing FASN expression and FA synthesis, resulting in tumor suppression. Taken together, our study indicates that this pathway may be a new therapeutic target for treating PCa.