BDNF and central nervous system cancer: For example, in our analyses PI3K-Akt signaling pathway was highlighted due to the involvement of the large number of target genes identified, of which we highlight the AKT1, AKT3, BDNF, CCND2, CDK4, CDK6, COL4A1 and PIK3R1. These genes are directly affected by circHIPK3 in gastric cancer [miR-124/miR-29b/COL4A1/CDK6 (33), miR-876-5p/PIK3R1 (35) and miR-637/AKT1 (36)], gallbladder cancer [miR-124/CDK6 (28)], breast cancer [circHIPK3/AKT (11)], glioma [miR-124/CCND2 (40)], lung cancer [miR-124/CDK4 (48) and miR-107/BDNF (50)] and oral squamous cell carcinoma [miR-637/AKT (58)].