Tumor immune resistance is recognized as a contributor to low survivorship in pancreatic ductal adenocarcinoma (PDAC). We developed a novel murine model of spontaneous PDAC clearance, generated by overexpressing interleukin-6 (IL-6) in orthotopically implanted PDAC cancer cells (OT-PDACIL6). Circulating IL-6 was 100-fold higher in OT-PDACIL6 than in OT-PDACparental mice. OT-PDACIL6 tumors were present at 5 days post-implantation, and undetectable by 10 days post implantation. Flow cytometry revealed increased T cells and NK cells, and decreased T regulatory cells in OT-PDACIL6 as compared to OT-PDACparental tumors. Increased lymphoid aggregates were apparent by histological assessment and may account for elevated T cell content. Antibody-based depletion of CD4+ and CD8+ T cells prevented tumor clearance and significantly reduced survival of OT-PDACIL6 mice. The anti-tumor immune response to OT-PDACIL6 rendered mice immune to re-challenge with OT-PDACparental tumors. In high concentrations, IL-6 acts in opposition to previously described pro-tumorigenic effects by enhancing the T cell-mediated anti-tumor response to PDAC.
Keywords: Interleukin 6; Pancreatic Ductal Adenocarcinoma; T-cell response.