-PDE4 isoforms exhibit diverse, context-dependent roles in cancer -Acting as tumor suppressors (e.g., suppressing migration in glioma via cAMP-p53)-Act as an oncogene (e.g., driving proliferation in lung cancer via cAMP-PKA/EPAC-HIF, and in other cancers through pathways like PI3K/AKT/MYC, β-catenin, and FAK/RACK1/PDE4D5/Rap1),- PDE4 inhibition can induce apoptosis in CLL and colorectal cancer. Here, RACK1 is linked to central nervous system cancer.