In pancreatic ductal adenocarcinoma, the FoxP3 expression was demonstrated in pancreatic cancer cells with tumor-infiltrating Tregs through the FoxP3/C-C motif chemokine ligand 5 (CCL5)/C-C motif chemokine receptor 5 (CCR5) pathway [27]. This evidence concerns the gene CCL5 and pancreatic ductal adenocarcinoma.