Liver metastasis studies using PaCa tumor-bearing mice have demonstrated that LIN28B-positive exosomes produced by PaCa cells may reach target cells and activate the LIN28B/let-7/HMGA2/PDGFB signaling axis to further promote PaCa metastasis after injection via caudal vein [115]. This evidence concerns the gene PDGFB and permanent neonatal diabetes mellitus-pancreatic and cerebellar agenesis syndrome.