Abstract: Objective To explore the synergistic inhibitory effect of polysaccharide from Trichoderma pseudokoningii (EPS) and oxaliplatin (Oxa) on colorectal cancer (CRC) HCT116 cells. Methods HCT116 cells were treated with 8 μg/mL Oxa and 100 μg/mL EPS alone or in combination, and the changes in cell viability was assessed with CCK-8 assay. CompuSyn software was used for fitting the Fa-CI curve to evaluate the combined effect of the two agents. Flow cytometry was performed to analyze cell apoptosis and cell cycle changes, and wound healing assay and Transwell assay were used to examine the migration ability of the treated cells. Oxa- and EPS-related genes and CRC-related genes were intersected for protein-protein interaction (PPI) analysis and GO and KEGG enrichment analyses. Results Treatment with Oxa alone or in combination with EPS significantly inhibited the viability of HCT116 cells in a dose- and time-dependent manner, and the two agents exhibited a significant synergistic effect (CI<1). The combined treatment with Oxa and EPS resulted in a significantly higher total cell apoptosis rate and a higher percentage of cells in S phase than Oxa alone and the control treatment (P<0.05). EPS and Oxa alone both inhibited the migration of HCT116 cells, and their combination produced a stronger inhibitory effect. GO enrichment analysis of the key genes related with Oxa, EPS and CRC suggested that these genes were involved mainly in such biological processes as exogenous apoptosis signaling, cell response to chemical stress, and reactive oxygen metabolism; KEGG analysis showed that these genes were involved in the pathways of drug resistance, apoptosis and angiogenesis. Conclusion EPS and Oxa can synergistically inhibit the proliferation of HCT116 cells possibly through the PI3K-Akt, MAPK, VEGF, and p53 signaling pathways.

Key words: polysaccharide; oxaliplatin; colorectal cancer; synergy; Trichoderma pseudokoningii