In the metabolic pathway of H+-transporting ATPase and futalosine hydrolase, SCFAs and its associated receptor (FFAR2) were found significantly down-regulated in the comparison between cancer and control group (p < 0.001) (Figure 3d,e) Subsequently, we explored the associations between six genera and three KOs based on Spearman’s rank correlation coefficients. This evidence concerns the gene FFAR2 and cancer.