CXCL12 and pancreatic neoplasm: In pancreatic microenvironment, pancreatic stellate cells (PSCs), a subset of pancreatic cancer-associated fibroblasts, promote myeloid cells to differentiate into MDSCs and induce MDSCs to aggregate into TME by producing IL-6, vascular endothelial growth factor (VEGF), macrophage colony-stimulating factor (M-CSF), SDF-1 and MCP-1 in a STAT3-dependent manner (14).