Abstract 5794: TrkB-mediated signaling contributes to malignant phenotypes of gallbladder cancer
Authors: Makoto Kawamoto, Hideya Onishi, Keigo Ozono, Akio Yamasaki, Akira Imaizumi, Masafumi Nakamura
Journal: Cancer Research (2017)

Abstract Background: Brain derived neurotrophic factor (BDNF)/ Tropomyosin-related kinase B (TrkB) signaling has been shown to be associated with aggressive phenotype in some cancers. However, the contribution of BDNF/TrkB signaling to gallbladder cancer (GBC), one of refractory malignancies, still remains unclear. This study aims to analyze the biological significance of BDNF/TrkB signaling in GBC. Methods: 1) Clinical experiment: 69 patients with primary GBC who underwent curative surgical resection were enrolled in this study. We investigated TrkB expression by immunohistochemistry and analyzed the correlation between TrkB expression and clinicopathological findings. 2) In vitro experiment: BDNF/TrkB signaling was inhibited using k252a or siRNA, and was activated by recombinant human BDNF (rhBDNF). Then, whether BDNF/TrkB signaling contributes to the biological function was estimated by proliferation assay and Matrigel invasion assay, using TrkB-expressing 5 GBC cell lines (NOZ, TGBC2TKB, GBd15, TYGBK-1, TYGBK-8). Furthermore, we determined the mechanisms of invasion in terms of epithelial mesenchymal transition (EMT) and matrix metalloproteinases (MMPs). We also examined the relationship between TrkB expression and the level of vascular endothelial growth factors (VEGFs) and hypoxia-inducible factor-1α (HIF-1α) in GBC. 3) In vivo experiment: Tumorigenesis and tumor growth of TrkB siRNA-transfected GBC cells were analyzed, using xenograft mice model. Results: 1) Clinical results; TrkB expression was detected in 63 (91.3%) GBC specimens. TrkB expression in the invasive front correlated with T factor (p=0.0391) and clinical staging (p=0.0391). Overall survival was lower in patients with high TrkB expression in the invasive front than in those with low TrkB expression (p=0.0363). 2) In vitro results; Proliferation was unaffected by rhBDNF treatment; however, K252a treatment and TrkB siRNA transfection decreased proliferation. rhBDNF treatment increased invasiveness by inducing EMT and activating MMP-2/MMP-9, whereas K252a treatment abrogated these effects. TrkB or BDNF siRNA transfection suppressed invasiveness. TrkB siRNA transfection decreased HIF-1α, VEGF-A, and VEGF-C/-D expressions. 3) In vivo results; TrkB siRNA transfection decreased tumorigenicity and tumor growth in NOZ and TYGBK-1. Conclusion: These findings demonstrate that TrkB-mediated signaling contributes to the induction of malignant phenotypes (proliferation, invasiveness, angiogenesis, lymphangiogenesis, and tumorigenesis) in GBC. Citation Format: Makoto Kawamoto, Hideya Onishi, Keigo Ozono, Akio Yamasaki, Akira Imaizumi, Masafumi Nakamura. TrkB-mediated signaling contributes to malignant phenotypes of gallbladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5794. doi:10.1158/1538-7445.AM2017-5794