Lentinus edodes polysaccharide MPSSS suppresses pancreatic cancer-associated fibroblast migration via HMGXB3

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a highly fibrotic tumour microenvironment (TME), which is dominated by cancer-associated fibroblasts (CAFs) that actively promote tumour progression and therapeutic resistance. Although the effects of MPSSS, a Lentinus edodes polysaccharide extract, on CAF immunosuppressive function and lymphangiogenesis have been reported, its impact on CAF migration and the role of HMGXB3 remain unknown. This study investigated the effects of MPSSS on CAF viability and migration and examined the potential involvement of HMGXB3. An in vitro CAF model was created by treating human pancreatic stellate cells with PANC-1-conditioned medium. The CAF phenotype was validated by the expression of α-smooth muscle actin (α-SMA), fibroblast activation protein-α (FAP) and interleukin-6 (IL-6). CAF viability was assessed using an MTT assay. HMGXB3 mRNA and protein expression were quantified using quantitative real-time PCR (qRT-PCR) and western blot analysis. CAF migration was evaluated using a Transwell assay. Normal fibroblasts served as controls. MPSSS reduced CAF viability in a dose-dependent manner (IC₅₀ ≈ 0.95 mg/ml), with significant inhibition occurring at concentrations of ≥0.8 mg/ml (P < 0.05). MPSSS significantly down-regulated HMGXB3 expression in CAFs at both the mRNA and protein levels, with no significant effect on normal fibroblasts. The Transwell assay showed that MPSSS markedly inhibited CAF migration, with a ~70% reduction observed at a concentration of 0.5 mg/ml (P < 0.01), which is below the cytotoxic threshold. HMGXB3 knockdown using small interfering RNA (siRNA) significantly inhibited CAF migration to a degree comparable to MPSSS treatment, and combined HMGXB3 knockdown with MPSSS exposure produced no additive effect, indicating that HMGXB3 is functionally required for CAF migration and mediates MPSSS-induced migratory inhibition. In conclusion, MPSSS suppresses CAF migration and viability through HMGXB3 downregulation. This suggests a novel strategy for TME remodelling in pancreatic cancer.