As shown in Figure 2E, the concentration of secreted PTX3 protein from HTB135 cells (5.62 ± 0.26 ng/ml, P <0.05) was much higher than that from other cells (0.44 ± 0.16 ng/ml), suggesting a relationship of the elevated expression levels of PTX3 and the BDNF/TrkB axis with the bone metastatic status in patients with advanced gastric cancer. Here, NTRK2 is linked to gastric cancer.