Effect of macrophages on pancreatic cancer.

Abstract

324 Background: Pancreatic Ductal Adenocarcinoma (PDAC) is expected to be the second leading cause of cancer related deaths by 2030. TGF-β is a well-studied PDAC mediator with a context dependent role as initially a tumor suppressor with potential to convert to a tumor promoter in later stages. Tumor associated macrophages and interleukins, such as the pro-inflammatory interleukin, IL23, are not well studied regarding PDAC. We hypothesized PDAC treated with TGF-β and macrophages would induce a more aggressive phenotype. Methods: We investigated aggressive behavior with a primary PDAC cell line in vivo and a metastatic PDAC cell line in vitro. A primary pancreatic cell line, Panc-1 cells, were pre-treated with PBS, IL23, macrophages (10:1 ratio of Panc-1 cells to macrophages), IL23 + macrophages, TGF-ß, TGF-ß + macrophages, or TGF-ß + macrophages + IL23. After treatment, cells were orthotopically implanted into the pancreas of NOD SCID gamma mice with 5 mice per group. Mice weights were recorded twice weekly for 4-weeks. Primary lesions and metastasis were investigated with ANOVA. AsPC-1 cells, a metastatic pancreatic cell line, were pre-treated with the same seven treatments. We investigated pSTAT3 expression and the streak closure in vitro. Results: Panc-1 cells treated with macrophages had the largest pancreatic tumor weight and diameter compared to PBS control, IL23 alone, and TGF-β alone (P < 0.001). When macrophages treatment included TGF-β, pancreatic tumor weights and diameters decreased as compared to macrophages alone and macrophages + IL23 (P < 0.001). Macrophage treatment induced higher liver weights and higher number of surface liver metastatic lesions suggesting higher metastatic disease burden (P < 0.03). AsPC-1 cells treated with combinations of macrophages and TGF-β increased pSTAT3 expression compared to PBS control. AsPC-1 cells treated with macrophages closed the gap in the scratch assay faster than PBS control 24 hours after treatment (P < 0.001). Conclusions: We demonstrated macrophages have a key role in converting primary pancreatic cancer into a more aggressive phenotype in vivo whereas they have less effect on metastatic pancreatic cancer in vitro.