Macrophage-derived cathepsin L promotes epithelial-mesenchymal transition and M2 polarization in gastric cancer

BACKGROUND Advanced gastric tumors are extremely prone to metastasize the in 20%–30% of gastric cancer, and patients have a poor prognosis despite systemic chemotherapy. Peritoneal metastases from gastric cancer usually indicate the end stage of the disease without curative treatment. AIM To peritoneal metastasis for facilitating clinical therapy are urgently needed. METHODS Immunohistochemical staining and immunofluorescence staining were used to demonstrate the high expression of cathepsin L (CTSL) in human gastric cancer tissues and its localization in cells. Lentivirus transfection was used to construct stable cell lines. Transwell invasion assays, wound healing assays, and animal tests were used to determine the relationships between CTSL and epithelial-mesenchymal transition (EMT) and tumorigenic potential in vivo . RESULTS We observed that macrophage-derived CTSL promoted gastric cancer cell migration and metastasis via the EMT pathway in vitro and in vivo , which involved macrophage polarization. Our findings suggest that macrophages improve extracellular matrix remodeling and hence facilitate tumor metastasis. Ablation of CTSL in macrophages within the tumor microenvironment may improve tumor therapy and the prognosis of patients with gastric cancer peritoneal metastasis. CONCLUSION In consideration of our findings, tumor-associated macrophage-derived CTSL is an important factor that promotes the metastasis and invasion of gastric cancer cells, and the targeting of CTSL may potentially improve the prognosis of patients with gastric cancer with peritoneal metastasis.