We first co-cultured wild-type pancreatic cancer cells with U937-derived macrophages, and found that compared with U937-derived macrophages, mRNA levels of M1-type markers (IL-8, TNF-α and IL-1β) in U937-derived macrophages were significantly decreased after co-cultured with PANC-1 cells (P < 0.001) (Figure 5B). This evidence concerns the gene CXCL8 and pancreatic neoplasm.