Upregulation of brain-derived neurotrophic factor in advanced gastric cancer contributes to bone metastatic osteolysis by inducing long pentraxin 3

The brain-derived neurotrophic factor (BDNF) activates its receptor, tropomyosin receptor kinase B (TrkB; also called NTRK2) that has been shown to promote the malignant progression of several cancers. In this study, we investigated the clinical and biological significance of the BDNF/TrkB axis in the progression of human gastric cancer. The increased co-expression of the BDNF/TrkB axis was significantly correlated with bone metastatic properties in advanced gastric cancers. BDNF acting via TrkB receptors increased the levels of long pentraxin 3 (PTX3) that was related to bone metastatic status of gastric cancer by enhancing gastric cancer-osteoblastic niche interactions. In bone metastatic gastric cancer, PTX3 knockdown using small interfering RNA significantly inhibited BDNF-induced interactions of cancer cells with osteoblasts. Moreover, BDNF-derived PTX3 induction supported subsequent osteoclastogenesis, and this effect was significantly reversed by PTX3 silencing. These findings suggest that a functional interaction between BDNF/TrkB and PTX3 enhances the osteolysis of bone metastatic gastric cancer, thereby providing potential prognostic factors for the development of bone metastasis of gastric cancer.