SMAD4 and pancreatic ductal adenocarcinoma: Pancreatic ductal adenocarcinoma (PDAC)-secreted exosomes from cells without the expression of SMAD4 could create an immunosuppressive myeloid cells background by increasing glycolysis and calcium flux through transferring differentially expressed miRNA and protein associated with SMAD4.136 These results suggested that immunosuppression induced by exosome-mediated metabolic reprogramming could be a potential inducer of tumor progression.