OCLN and colorectal carcinoma: Several beneficial bacteria (Lactobacillus rhamnosus GG, Lactobacillus plantarum, Lactobacillus reuteri, Bifidobacterium breve, Bifidobacterium longum, Bifidobacterium bifidum, Akkermansia muciniphila, and Faecalibacterium prausnitzii) play a significant role in improving the integrity of the intestinal epithelial barrier by upregulating the expression of tight junction proteins (occludin, claudins, and zonula occludens) and preventing CRC progression (Figure 4).