植化素對致癌腸道核梭桿菌表面黏附蛋白FadA與腸道細胞間的交互作用及其引發大腸直腸癌的分子機轉

Gut microorganism Fusobacterium nucleatum (F. nucleatum) is associated with colorectal adenomas and advanced-stage colorectal cancer. FadA is a surface adhesin protein of F. nucleatum. In the present study, FadA gene was subcloned into bacterial expression vector in frame with an N-terminal His-Sumo tag as to express as His-Sumo tagged proteins. The constructs and the sequence of FadA were confirmed by DNA sequencing. The His-Sumo tagged FadA protein was purified by the Ni2+-NTA column. The His-Sumo tag was further digested with Sumo-specific protease to remove the His-Sumo tag, and the tag free protein was purified. In addition, the outer membrane vesicles secreted by the bacteria containing FadA was also isolated. It is noteworthy that our purified His-Sumo tagged FadA and isolated vesicle indeed increased the growth of human colorectal cancer CTNNB1 mutant HCT 116 cells. In addition, among all tested phytochemicals (justicidin A, formosanin C, resveratrol, and pterotilbene), justicidin A not only suppressed the growth of human colorectal CTNNB1 mutant HCT 116 and Caco-2 cell lines but also the CTNNB1 wild-type (APC mutant) HT-29 cell line. It is noteworthy that justicidin A inhibited β-catenin expression of all these three tested cell lines, and reversed FadA-activated Wnt signaling in HT-29 cells. Our results suggest the anticancer therapeutic potential of justicidin A.