Survay on carcinogenic risks by oral bacteria and their measures

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K10087
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 57020:Oral pathobiological science-related
• Research Institution: Okayama University
• Principal Investigator: Kokeguchi Susumu 岡山大学, 医歯薬学域, 准教授 (10144776)
• Co-Investigator(Kenkyū-buntansha): 横田 憲治 岡山大学, 保健学域, 教授 (00243460) ; 村上 純 岡山大学, 歯学部, 博士研究員 (40362983) ; 有元 佐賀惠 岡山大学, 医歯薬学域, 准教授 (90212654) ; 渡辺 朱理 徳島大学, 大学院医歯薬学研究部(歯学域), 講師 (80585026)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 口腔細菌 / 変異原性

Outline of Final Research Achievements

Helicobacter pylori is a well-known bacterial carcinogen in gastric cancer. The possible association between intestinal bacterial flora and colorectal cancer has been also most studied. The several oral bacteria species such as Fusobacterium nucleatum etc. have been frequently isolated from various cancer regions. However, the relationship between oral bacteria and cancer development remains inadequate. The aim of this study is to reveal direct or indirect carcinogenic potential in oral bacteria. The extracts of F. nucteatum was not mutagenic in the Ames test. Several Nitrate-reducing oral bacteria, including Actinomyces and Streptococcus were isolated from the Gastroscopy samples in the gastric precancerous state, which produce the main carcinogenic N-nitroso compounds. These bacteria showed the potential production of inflammatory mediators such as IL-8 and TNF-α with THP cells in the relation to mutagenesis. The genome analyses of oral bacteria to find oncoprotein CagA are ongoing.

Free Research Field

口腔細菌学

Academic Significance and Societal Importance of the Research Achievements

現在、超高齢化社会へ進む我が国の死亡原因の第１位である癌への対策が急務である。胃癌はピロリ菌の持続感染がその発生リスク要因であり、大腸癌は腸内細菌叢が関わることが明らかとなった。各種の癌病巣からFusobacterium nucleatumをはじめ様々な口腔細菌種が分離されているが、発癌との関わりは今だ不明である。本研究は近年増加している食道や咽頭また消化器系の癌発生における口腔細菌の直接的あるいは間接的な関わり、さらには発生メカニズムの解明を目指した。また最新の細菌ゲノム解析を用いてピロリ菌の発癌蛋白CagA類似遺伝子を口腔細菌種で探索した。ピロリ菌発見以来その学術的、社会的な意義は大きい。