Rho Small GTPase Family in Androgen-Regulated Prostate Cancer Progression and Metastasis

Background/Objectives: Rho small GTPases (RSG), which regulates metastasis, constitute eight subfamilies—“classical” Rho, Rac, cdc42, and “atypical” Rif, Rnd, Wrch, RhoH, and RhoBTB. Their downstream signaling requires switching between GTP-bound active and GDP-bound inactive forms. Classical RSGs, but not atypical RSGs, require regulation by guanine nucleotide exchange factors (GEF), GTPase-activating proteins (GAP) and guanine nucleotide dissociation inhibitors (GDI) to achieve this switch. The objective of this review is to summarize the roles of RSGs in metastatic prostate cancer (mPCa) and their interaction with the androgen receptor (AR), which regulates this disease. Methods: We summarize the literature that describes the role of RSGs in mPCa, and their interaction with the AR. Results: Classical RSGs mostly promote metastasis (except RhoB), whereas atypical RSGs, with exceptions, mostly prevent it. Their role, however, is context-dependent—e.g. RhoB is tumor-suppressive in AR-null PCa but oncogenic in AR-positive tumors. The AR modulates RSG expression transcriptionally, but also affects their function through modulation of GEFs, GAPs, and GDIs. In turn, RSGs also regulate AR transcriptional activity. Interestingly, RSGs and the AR have non-genomic interactions via membrane-localized AR (mAR) not affected by AR inhibitors. Conclusions: Drugs that target RSGs are needed along with AR inhibitors to prevent mPCa progression.