Dextran Sulfate Inhibits Angiogenesis and Invasion of Gastric Cancer by Interfering with M2-type Macrophages Polarization

Purpose: To explore the effect of dextran sulfate (DS) on the angiogenesis, invasion, and migration of gastric cancer cells by interfering with the polarization of M2-type macrophages. Methods: The infiltration of M2-type macrophages and microvascular density in gastric cancer and paracancerous tissues were analyzed using immunohistochemistry and immunofluorescence. The effects of DS on M2-type macrophages and the angiogenesis in metastatic tumors were investigated in the nude mice intraperitoneal metastasis model using immunohistochemistry and western blot. The differentiation and polarization of macrophages, immunocytochemistry, western blot, ELISA, and transwell migration assay were used to evaluate the effect of DS on the polarization of macrophages, immunocytochemistry, western blot, ELISA, and transwell migration assay were used to evaluate the effect of DS on the polarization and recruitment capacity of macrophages. Immunocytofluorescence, tube formation assay, transwell invasion assay, wound healing assay, and western blot were used to investigate the effect of DS on the angiogenesis, invasion, and migration-promoting phenotype of M2- type macrophage in a co-culture system of macrophages and gastric cancer cells. Results: The infiltration of M2-type macrophages and the microvascular density were highly expressed and positively correlated in the human gastric cancer tissue. DS can significantly inhibit the intraperitoneal metastases of gastric cancer in nude mice, and reduce the infiltration of M2-type macrophages and the angiogenesis in intraperitoneal metastatic tumors. Moreover, DS can prevent the polarization of M0-type macrophages to M2 type, reduce the expression of M2-type macrophage markers (CD206, CD163, IL-10, and Arg-1), down-regulate the IL-6-STAT3 pathway, and inhibit the recruitment capability of M2-type macrophages. Finally, the co-culture experiment showed that DS significantly reduced the enhancing effects of M2-type macrophages on the angiogenesis, invasion, and migration of gastric cancer cells, as well as down-regulated the related expressions of proteins (VEGF, N-cadherin, MMP-2 and Vimentin) in gastric cancer cells. Conclusion: DS can reduce the infiltration of M2-type macrophages and the microvascular density in intraperitoneal metastases of gastric cancer in nude mice, and inhibit the angiogenesis, invasion, and migration of gastric cancer cells by interfering with the polarization of M2-type macrophages through repression of the IL-6/STAT3 signaling pathway.