Expression of Toll-Like Receptors on Human Rectal Adenocarcinoma Cells

The innate immune system uses Toll-like receptors (TLR) to detect the presence of pathogen patterns thus allowing for rapid host defense responses. Stimulation of TLR results in inflammatory response and regulatory cytokine production affecting acquired immunity. The aim of the study was an evaluation of TLR2 and TLR4 expression on the surface of human colon cancer cells in primary culture with or without autologous peripheral blood mononuclear cells. Surgical specimens of colon cancer were processed to obtain cancer cells. Cancer cells separation was conducted first by mechanical tissue disintegration and than by gradient centrifugation to obtain 95 % cell confluence. By staining the isolated cells the pathologist determined them as adenocarcinoma. Colon cancer cells were then co-cultured in 24 h culture alone or together with autologous lymphocytes. Reverse-transcription polymerase chain reaction was performed for detection of TLR2 and TLR4 mRNA in colon cancer and normal colon epithelial cells using commercially available primers. Resting as well as phytohemagglutinin or lipopolysaccharide (LPS) stimulated cells were tested. Receptor proteins on cancer cells were examined by immunohistochemistry. TLR4 mRNA was detected in cancer cells. Autologous lymphocytes do not exert any effect on these receptors expression. TLR4 mRNA expression was not observed in normal colon epithelial cells. TLR2 mRNA was present on LPS stimulated cancer cells as well as on resting and stimulated lymphocytes. Expression of TLR2 and TLR4 receptor proteins on colon cancer cells were confirmed by immunohistochemistry. TLR4 may be responsible for uncontrolled tumor growth under LPS stimulation in human colon environment.