319. SIGNIFICATIONS OF EXPRESSION OF TOLL-LIKE RECEPTORS IN ESOPHAGEAL SQUAMOUS CELL CARCINOMA CELLS

Abstract Well known risk factors of Esophageal squamous cell carcinoma (ESCC) are habit of alcoholic drinking, smoking and poor diet. Moreover, recent reports showed that poor oral health is associated with upper aerodigestive tract malignancies including ESCC. We previously reported that among 232 ESCC patients who had preoperative assessment of oral function by dentist, about 70% of patients were diagnosed with periodontitis and about half of those patients were needed dental extraction. Toll-like receptors (TLRs), a family of pattern recognition receptors, are able to recognize pathogen-associated molecular patterns (PAMPs) associated with a wide range of viruses, bacteria, fungi and parasites and thus play key roles in innate immune responses. Among these TLRs, TLR4 recognizes LPS, which construct the cell wall of gram-negative bacteria. Based on these findings, it is supposed that continuous exposure of LPS from gram-negative periodontal bacteria induces chronic inflammation caused by inflammatory cytokines from TLR4 signals, then carcinogenesis and progression of ESCC occurs. Among these TLRs, TLR4 recognizes LPS, which construct the cell wall of gram-negative bacteria. We reported that ESCC patients who had higher TLR4 expression status in resected main tumor specimen showed significantly poor overall survival compared to lower patients after esophagectomy. (Sato Y, et al. Esophagus 2020) On the other hand, TLR3 recognizes dsRNA released form cell invading viruses. We previously reported that ESCC patients who had higher TLR3 expression status in resected main tumor specimen showed significantly better overall survival compared to lower patients after esophagectomy. (Sato Y, et al. Am J Surg. 2018). Though TLR3 and TLR4 are in the same TLR family, those functional mechanism and relationships to prognosis in ESCC are totally different. Because TLR4 signaling is stimulatory on proliferative ability of ESCC, it is supposed that improvement of oral health inhibits carcinogenesis and progression of ESCC. On the other hand, because TLR3 signaling is suppressive, TLR3 agonist should be a possible candidate of therapeutic agent.