Combined Bacterial Antigen Lipopolysaccharide and Lipoteichoic Acid Increase Cal 27 Oral Cancer Cell Proliferation

Abstract

Oral biofilms harbour gram-negative bacterial antigen lipopolysaccharide (LPS) involved in oral cancer progression and gram-positive bacterial surface-associated adhesive, lipoteichoic acid (LTA). Thus, we hypothesised that LPS and LTA together would increase the proliferation of cancer cells compared to stimulation by LPS alone. Oral cancer cell lines SCC4, SCC9, SCC25, Cal 27 and the normal oral cell line, OKF6, were studied. The bacterial antigen stimulation indices were determined using the MT Glo assay. Cell proliferation after bacterial antigen stimulation was validated by clonogenic assays. Phosphokinase array, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and Western blot were employed to study proliferative and apoptotic pathways in bacterial antigen-stimulated cells. Bacterial antigens significantly stimulated Cal 27 (p ≤ 0.001) alone. SCC4 and SCC9 showed negligible stimulation with either antigen, while SCC25 results were comparable to OKF6. The combined antigen stimulation of Cal 27 led to a decrease in phosphorylated p53 and β-catenin and higher PI3K compared to LPS only stimulated cells (p ≤ 0.001). Combined bacterial antigen stimulation results in increased proliferation of Cal 27 cells due to lowering of tumor suppressor proteins and increased tumor proliferation-related proteins.