In colorectal cancer, inhibitors of DNA-binding protein 4 (ID4) can promote tumorigenesis by targeting brain-derived neurotrophic factor (BDNF) (37), and can also inhibit tumor growth and metastasis by inhibiting PI3K/AKT pathway and inhibiting epithelial-mesenchymal transition (EMT) in a CK18-Related manner (38). Here, BDNF is linked to colorectal cancer.