Activation of BDNF/TrkB pathway promotes prostate cancer progression via induction of epithelial-mesenchymal transition and anoikis resistance

Prostate cancer (PCa) is one of the most common malignant diseases in male worldwide, yet, the molecular mechanisms involved in PCa progression are still poorly understood. This study aimed to investigate the roles of the brain-derived neurotrophic factor/tropomyosin receptor kinase B (BDNF/TrkB) pathway in PCa progression. It was demonstrated by immunohistochemical analysis that both BDNF and TrkB were overexpressed in PCa tissues and elevated TrkB expression was tightly related with lymph node metastasis and advanced stage of PCa. In vitro studies showed that stimulation with rhBDNF or overexpression of TrkB in PCa cells promoted cell migration, invasion, and anoikis resistance. Overexpression of TrkB also resulted in epithelial-mesenchymal transition (EMT)-like transformation in cell morphology, whereas RNA interference-mediated TrkB depletion caused reversion of EMT. Further investigation demonstrated that protein kinase B (AKT) was responsible for BDNF/TrkB signaling-induced pro-migratory and pro-invasive effects, EMT, and anoikis resistance. Finally, in vivo studies confirmed that enhanced TrkB expression facilitated tumor growth, whereas downregulation of TrkB suppressed tumor growth. Our findings illustrate that BDNF/TrkB pathway is crucial for PCa progression, which may provide a novel therapeutic strategy for the treatment of advanced PCa.