IADR Abstract Archives
Fusobacterium Nucleatum Induces PD-L1 Expression in Colon Cancer Cells
Objectives: Fusobacterium nucleatum (F. nucleatum), a Gram-negative obligate anaerobic bacterium, is one of the most abundant species in the oral cavity and gut. It has been reported that a higher load of F. nucleatum was found in tumor tissues and feces of colorectal cancer patients. The programmed death-ligand 1 (PD-L1), also known as the immuno-regulatory B7-H1 receptor, plays an important role in the cell-mediated immune response. The study aimed to analyze in vitro the potential of F. nucleatum in PD-L1 up-regulation.
Methods: F. nucleatum strains ATCC 49256, and ATCC 10953 were cultured in Brain Heart Infusion (BHI) broth and incubated anaerobically. Bacteria that were heat-killed at 100°C for 10 min were used for infection of a human colon cancer cell line (CL-11) with multiplicity of infection (MOI) of 10, 50,100, and 200 for 4h, 8h, 24h, and 48h. Non-infected cells were used as negative control. IFN- γ was applied as positive control. The PD-L1 expression was analyzed using the Western blot method.
Results: All strains of F. nucleatum induced up-regulation of the PD-L1 expression. After infection with both strains for 24h and 48h, PD-L1 expression significantly altered. Infection with F. nucleatum ATCC 10953 for 24h caused a 1.5-fold induction of PD-L1 at MOI of 50, 100, and 200. For 48h, using strain ATCC 49625 increased 1.5-fold at MOI 100 and 200, infection with F. nucleatum ATCC 10953 caused a 2-fold induction of PD-L1 (MOI of 100 and 200).
Conclusions: These findings suggest that heat-killed F. nucleatum can also up-regulate the expression of PD-L1 in CL-11 cells, which might contribute to the immune evasion of colon cancer. Further studies are still warranted to investigate different mechanisms of F. nucleatum in PD-L1 induction.
Methods: F. nucleatum strains ATCC 49256, and ATCC 10953 were cultured in Brain Heart Infusion (BHI) broth and incubated anaerobically. Bacteria that were heat-killed at 100°C for 10 min were used for infection of a human colon cancer cell line (CL-11) with multiplicity of infection (MOI) of 10, 50,100, and 200 for 4h, 8h, 24h, and 48h. Non-infected cells were used as negative control. IFN- γ was applied as positive control. The PD-L1 expression was analyzed using the Western blot method.
Results: All strains of F. nucleatum induced up-regulation of the PD-L1 expression. After infection with both strains for 24h and 48h, PD-L1 expression significantly altered. Infection with F. nucleatum ATCC 10953 for 24h caused a 1.5-fold induction of PD-L1 at MOI of 50, 100, and 200. For 48h, using strain ATCC 49625 increased 1.5-fold at MOI 100 and 200, infection with F. nucleatum ATCC 10953 caused a 2-fold induction of PD-L1 (MOI of 100 and 200).
Conclusions: These findings suggest that heat-killed F. nucleatum can also up-regulate the expression of PD-L1 in CL-11 cells, which might contribute to the immune evasion of colon cancer. Further studies are still warranted to investigate different mechanisms of F. nucleatum in PD-L1 induction.