Vagus nerve signal has an inhibitory influence on the development of peritoneal metastasis in murine gastric cancer.

The vagus nerve is the only pathway for transmitting parasympathetic signals between the brain and thoracoabdominal organs, thereby exhibiting anti-inflammatory functions through the cholinergic anti-inflammatory pathway. Despite often being resected during lymph node dissection in upper gastrointestinal cancer surgery, the impact of vagotomy on postoperative outcomes in gastric cancer patients remains unclear. Sub-diaphragmatic vagotomy was performed on C57BL/6 mice. Three weeks later, syngeneic murine gastric cancer cell line YTN16P was injected into the peritoneal cavity, and the number of peritoneal metastases (PM) on the mesentery and omentum compared with control mice. The phenotypes of immune cells in peritoneal lavage and omental milky spots one day after tumor inoculation were analyzed using flow cytometry and immunohistochemistry. Intraperitoneal transfer of 3 × 105 YTN16P significantly increased the number of metastatic nodules on the mesentery in the vagotomy group compared to the control group. The omental metastasis grade was also significantly higher in the vagotomy group. Phenotypic analysis of immune cells in peritoneal lavage did not reveal significant differences after vagotomy. However, vagotomized mice exhibited a notable increase in milky spot area, with a higher presence of cytokeratin(+) tumor cells, F4/80(+) macrophages, and CD3(+) T cells. Vagus nerve signaling appears to regulate the immune response dynamics within milky spots against disseminated tumor cells and inhibits the development of PM. Preserving the vagus nerve may offer advantages in advanced gastric cancer surgery to reduce peritoneal recurrence.

Splenectomy has opposite effects on the growth of primary compared with metastatic tumors in a murine colon cancer model.

The spleen is a key source of circulating and tumor-infiltrating immune cells. However, the effect of splenectomy on tumor growth remains unclear. At 3 weeks after splenectomy, we subcutaneously injected LuM1 cells into BALB/c mice and evaluated the growth of primary tumors and lung metastases at 4 weeks after tumor inoculation. In addition, we examined the phenotypes of immune cells in peripheral blood by using flow cytometry and in tumor tissue by using multiplex immunohistochemistry. The growth of primary tumors was reduced in splenectomized mice compared with the sham-operated group. Conversely, splenectomized mice had more lung metastases. Splenectomized mice had fewer CD11b+cells, especially monocytic MDSCs (CD11b+Gr-1neg-lowLy6chigh), and NK cells (CD49b+CD335+). The proportion of NK cells was inversely correlated with the number of lung metastases. In splenectomized mice, the density of CD3+ and granzyme B+ CD8+ T cells was increased, with fewer M2-type macrophages in primary tumors, but NK cells were decreased markedly in lung. Splenectomy concurrently enhances T cell-mediated acquired immunity by reducing the number of monocytic MDSCs and suppresses innate immunity by decreasing the number of NK cells. Splenectomy has opposite effects on primary and metastatic lesions through differential regulation on these two immune systems.

[Intraperitoneal Transfer of miR-29b Containing Exosome Suppresses the Development of Peritoneal Metastases from Gastric Cancer].

Although miR-29b levels in peritoneal exosomes was markedly reduced in patients with peritoneal metastases(PM), their role has not been fully clarified. Bone marrow derived mesenchymal stem cells(BMSC)were transfected with miR-29b- integrating lentivirus and exosomes isolated from culture supernatants using ultracentrifugation. The effects of the exosomes on human peritoneal mesothelial cells(HPMC)were examined in vitro. The in vivo effect of murine BMSC-derived exosomes was examined with a syngeneic PM model. Culture of HPMC with TGF-ß1 decreased expression of E-cadherin and calretinin with increased expression of vimentin, totally restored by adding miR-29b-rich exosomes. The exosomes inhibited proliferation and migration of HPMC, and inhibited adhesion of gastric cancer cells to HPMC. Intraperitoneal(IP)transfer of miR- 29b-rich exosomes every 3 days markedly reduced the number of PM of a murine gastric cancer cell, YTN16P, on the mesentery of C57/BL6 mice. IP administration of miR-29b-containing exosome suppresses the development of PM of gastric cancer.