PIK3CA and colorectal cancer: Consistent with a continuous change in the intestinal microbiota and luminal contents along the bowel subsites, host immunity against colorectal tumors and proportions of colorectal cancers with specific molecular features of colorectal cancer such as microsatellite instability (MSI), high-level CpG island methylator phenotype (CIMP), and BRAF and PIK3CA mutations change along the bowel subsites [7–12].