The pathogenicity of vancomycin-resistant Enterococcus faecalis to colon cancer cells

Background The aim of this study was to investigate the pathogenicity of vancomycin-resistant Enterococcus faecalis (VREs) to human colon cells in vitro. Methods Three E. faecalis isolates (2 VREs and E. faecalis ATCC 29212) were cocultured with NCM460, HT-29 and HCT116 cells. Changes in cell morphology and bacterial adhesion were assessed at different time points. Interleukin-8 (IL-8) and vascular endothelial growth factor A (VEGFA) expression were measured via RT-qPCR and enzyme-linked immunosorbent assay (ELISA), respectively. Cell migration and human umbilical vein endothelial cells (HUVECs) tube formation assays were used for angiogenesis studies. The activity of PI3K/AKT/mTOR signaling pathway was measured by Western blotting. Results The growth and adhesion of E. faecalis at a multiplicity of infection (MOI) of 1:1 were greater than those at a MOI of 100:1( p < 0.05). Compared to E. faecalis ATCC 29212, VREs showed less invasive effect on NCM460 and HT-29 cells. E. faecalis promoted angiogenesis by secreting IL-8 and VEGFA in colon cells, and the cells infected with VREs produced more than those infected with the standard strain ( p < 0.05). Additionally, the PI3K/AKT/mTOR signaling pathway was activated in E. faecalis infected cells, with VREs demonstrating a greater activation compared to E. faecalis ATCC 29212 ( p < 0.05). Conclusion VREs contribute to the occurrence and development of CRC by promoting angiogenesis and activating the PI3K/AKT/mTOR signaling pathway.