Al-MPS Obstructs EMT in Breast Cancer by Inhibiting Lipid Metabolism via miR-215-5p/SREBP1.

Alkali-extractable mycelial polysaccharide (Al-MPS) is a natural macromolecular polymer that has shown anti-hyperlipidemic and antitumor abilities. This study investigates the mechanism by which Al-MPS inhibits lipid metabolism and epithelial-mesenchymal transition (EMT) in breast cancer (BC). BC cells (MCF-7 and MDA-MB-231) were transfected and/or treated with Al-MPS. CCK-8, Transwell, and scratch assays were used to evaluate the tumorigenic behaviors of BC cells. The expression levels of SREBP1, E-cadherin, N-cadherin, Snail, vimentin, FASN, ACLY, and ACECS1 in BC cells were detected by Western blotting. Dual-luciferase reporter and RNA pull-down assays were performed to verify the binding between miR-215-5p and SREBP1 mRNA. Nude mice were injected with MDA-MB-231 cells and treated with Al-MPS. The changes in tumor volume and protein expression were monitored. miR-215-5p was downregulated and SREBP1 was upregulated in BC. Al-MPS increased miR-215-5p expression and inhibited SREBP1 expression, lipid metabolism, and EMT in BC. Inhibition of miR-215-5p or overexpression of SREBP1 promoted the tumorigenic behaviors of BC cells by stimulating lipid metabolism and counteracted the antitumor effect of Al-MPS. SREBP1 was a downstream target of miR-215-5p. In conclusion, Al-MPS inhibits lipid metabolism and EMT in BC via the miR-215-5p/SREBP1 axis. This study supports the application of polysaccharides in cancer treatment and the molecules regulated by Al-MPS may be used as biomarkers or therapeutic targets for BC.