Abstract 3300: Gal-GalNAc overexpressed in colorectal carcinoma mediates attachment and colonization of Fusobacterium nucleatum utilizing the Fap2 lectin

Abstract

Abstract Recent reports revealed overabundance of oral Fusobacterium nucleatum (Fn) in colorectal carcinoma (CRC) compared to adjacent healthy tissue. This study aims to investigate the molecular mechanisms that mediate CRC colonization by Fn. Using the orthotopic Colon-26 colorectal cancer model, we found that intravascular injected Fn colonizes CRC more than adjacent healthy tissue. Fusobacterial localization in the colon is tumor-dependent, as injected fusobacteria were undetected in the colons of tumor-free mice. CRC colonization is species specific as the gram-negative, anaerobe and periodontitis-related pathogen Prophyromonas gingivalis, which was shown to be abundant in oral tumors failed to colonize CRC. Higher levels of D-galactose-β(1-3)-N-acetyl-D-galactosamine (Gal-GalNAc) are known to be detected in CRC. We recently identified the fusobacterial Fap2 outer-surface protein as a galactose binding lectin, suggesting that it might promote binding of fusobacteria to CRC. A fluorescent-labeled Peanut Agglutinin lectin (PNA) detected more Gal-GalNAc in human and mouse CRC compared to adjacent healthy tissues. Binding of FITC-labeled Fn corresponded with the levels of Gal-GalNAc and colocalized with Gal-GalNAc in the tumor. Flow cytometry revealed that Fap2-deficient Fn mutants are impaired in binding to CRC cell lines compared with their WT parent. Soluble GalNAc inhibited the binding of PNA and WT Fn to CRC cells in a dose-dependent manner, but did not affect the residual CRC binding of fap2 mutated Fn. Furthermore, in the colorectal cancer murine model, tumor colonization by Fap2-deficient Fn mutants was significantly lower than that of the Fap2 sufficient parental strain. Our results demonstrate that the fusobacterial Fap2 lectin binds to Gal-GalNAc on CRC and mediates the tumor-specific attachment of Fn. Understanding the interaction of Fn with CRC, may enable future development of novel diagnostic and therapeutic agents for this disease. Citation Format: Jawad H. Abed, Johanna Emgård, Stella Chaushu, Wendy Garrett, Gilad Bachrach. Gal-GalNAc overexpressed in colorectal carcinoma mediates attachment and colonization of Fusobacterium nucleatum utilizing the Fap2 lectin. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3300.