Mechanism of breast cancer centrosome regulatory protein SEC23B on tumor invasion and metastasis

Abstract

Background and purpose: The novel centrosomal regulatory protein Sec23 homolog B (SEC23B) regulates autophagy in cells, thereby providing energy and nutrients that contribute to tumor growth and distant metastasis. However, whether this role is involved in the mechanism of infiltrative metastasis in breast cancer is unclear. The aim of this study was to investigate the molecular mechanism by which SEC23B promotes breast cancer infiltration and metastasis. Methods: The association between SEC23B expression and breast cancer prognosis and metastasis was analyzed using Kaplan-Meier Plotter database and HCMDB database. MCF-7 cells were divided into vector group (control) and SEC23B overexpression plasmid group (SEC23B), and MDA231-LM2 cells were divided into SEC23B knockdown group (sh-SEC23B) and control group (sh-NC). Western blot was used to detect the expressions of SEC23B, autophagy-associated proteins [dead bone fragment 1 (SQSTM1, p62), microtubule-associated-protein light-chain-3 (LC3)] and extracellular-regulated protein kinases (ERK)/mammalian target of rapamycin (mTOR) pathway proteins in breast cancer cells. Cell migration was assessed by transwell assay and wound healing assay, and autophagic granules in cells were detected by immunofluorescence staining. In addition, an in vivo intraperitoneal tumor model was constructed to study the effect of SEC23B on breast cancer cell metastasis in vivo. Results: The overall survival of breast cancer patients with high SEC23B expression was significantly shorter than that of patients with low SEC23B expression. The expression of SEC23B in metastatic breast cancer was significantly higher than that in breast cancer without metastasis. SEC23B protein levels were lower in primary breast cancer cells (MCF-7, BT-549, MDA-MB-468 and MDA-MB-453) than in metastatic breast cancer cells (MDA231-LM2 and ZR-75-30). Compared with the control group, the SEC23B group significantly accelerated cell migration (P<0.001). Compared with the sh-NC group, the sh-SEC23B group significantly reduced cell migration (P<0.001). Compared with the control group, the expression level of LC3A/B and the formation of autophagy particles in the SEC23B group were significantly increased, while the expression of p62 protein and the phosphorylation levels of mTOR and ERK were decreased. Compared with the sh-NC group, the LC3A/B expression level and the formation of autophagy particles were significantly decreased in the sh-SEC23B group, and the phosphorylation levels of mTOR and ERK were increased, especially under starvation conditions. In in vivo experiments, tumor weight was significantly lower in the sh-SEC23B group compared with the sh-NC group (P<0.01), and there was an increase in necrotic tissue and a decrease in tumor metastasis in lung tissue in mice. sh-SEC23B group mice had a significantly lower number of lung metastatic tumors and LC3 immunohistochemical staining than the sh-NC group (P<0.01). Conclusions: SEC23B induces breast cancer autophagy and promotes cancer cell metastasis by inhibiting ERK/mTOR signaling pathway.

Keywords

• |sec23 homolog b|breast cancer|autophagy|metastasis|erk/mtor signaling pathway