Expression of Toll Like Receptors in Lung Cancer and Investigating Their Effect on Apoptosis

Abstract

Members of the Toll like receptors (TLRs) family play key roles in both innate and adoptive immune responses. TLRs proteins enable host to recognize a large number of pathogen associated molecular patterns such as bacterial lipopolysaccharides (LPS), viral RNA, CpG containing DNA. TLRs are also able to mediate responses against host molecules including breakdown products of tissue matrix, heat shock proteins and reactive oxigene species. Therefore, TLRs are involved in the development of many pathological conditions including cancer and infectious disease. Lung carcinoma is one of the leading causes of death worldwide. It is a non-immunogenic cancer, resistant to immune surveillance. Given that cancerous cells evade the immune system, the activation of TLRs could represent a potential target for cancer therapy. The aim of our study, is to investigate the expression of TLRs and the effects of TLRs agonists on proliferation, apoptosis and cell cycle in SCLC-21H and NCI-H82 human small cell lung carcinoma cell lines. The expression of TLR2, TLR3, TLR4, TLR5, TLR6, TLR7 SCLC-21H and NCI-H82 small cell lung cancer cell lines were assessed by using flow cytometry. Cell cycle analysis and apoptosis were detected by flow cytometry. We found high TLR2, TLR5 and TLR6 expression in SCLC-21H and NCI-H82 small cell lung cancer cell lines. In contrast to this SCLC-21H and NCI-H82 small cell lung cancer cell lines were showed TLR3, TLR4, TLR7 weak expression. Incubation of SCLC-21H and NCI-H82 small cell lung cancer cell lines with TLR 2 (P. gingivalis LPS-TLR2 ligand), TLR 5 (Flagellin from B subtilis, TLR 5 ligand) and TLR6 (Diacylated lipoprotein FSL-1 TLR6 ligand) ligands induced apoptosis. We showed that ligands of TLR2, 5 and 6 did not affect cell cycle proliferation in small cell lung cancer cells. We found TLRs ligands as inducer of cytokines secretion, and these secreted cytokines can be showed as a result of activated TLRs. We showed, TLR2, TLR5 and TLR6 ligation can stimulate immune cells to secrete many kinds of TLR incuded cytokines such as TNFα, IL1b, IL6, IL12, IL17A, IL8, MCP-1, RANTES, MIP-1a, MIP-1b, MDC, Eotaxin. The expression of TLR 2, TLR5 and TLR 6 in SCLC-21H and NCI-H82 small cell lung cancer cell lines might affect treatment approaches using TLRs agonists and shows that lung cancer cells can be regarded as active players in tumor-immunology.