Abstract 1791: Immunochemotherapy with 5-Fluorouracil and Interferon-α enhances the recognition of pancreatic cancer cells by NK and CD8+ T cells via increasing the expression of NKG2D ligands and MHC Class-I

Abstract

Abstract Pancreatic cancer has the poorest prognosis of all cancers urging the necessity of new therapeutic approaches. Recent clinical data show encouraging results for combining Interferon-α (IFN-α) immunotherapy with 5-Fluorouacil (5-FU) chemotherapy. However, the role of IFN-α in this immunochemotherapy scheme is still elusive. Here we investigate in vivo the relevance of different immune cells in the anti-cancer immune response mediated by IFN-α in combination with 5-FU using an orthotopic mouse model of pancreatic carcinoma. Luciferase-transfected Panc02 cells were implanted in the pancreas of C57BL/6 mice. Five days later, mice were treated with 5-FU alone, 5-FU + IFN-α or with a vehicle control. In parallel, CD4+ T cells, CD8+ T cells, and NK cells were depleted by neutralizing antibodies. Depletion of CD11c+ dendritic cells (CD11c+ DCs) and regulatory T cells (T regs) was performed using transgenic mice based on the diphtheria toxin receptor-mediated conditional and targeted cell ablation. On day 21, tumor volume was measured and NK cells were isolated and enriched from spleens of mice then used as effectors against Panc02 cells in a standard chromium release assay. Tumors were frozen for further immunohistochemistry analysis to evaluate the immune cells infiltration. In parallel, we performed flow cytometry analysis to evaluate the effects of different treatments on the expression of MHC Class-I and NKG2D ligands (MULT-1 and Rae-1) in Panc02 cells in vitro and in the pancreatic tumors in vivo. Our data show that treatment with 5-FU + IFN-α has significantly decreased tumor volume in comparison with control or 5-FU treatments. This decrease in tumor volume was remarkably abolished by depleting CD8+ T cells or NK cells. The tumors of 5-FU + IFN-α treated mice harbor higher numbers of infiltrating NK cells in comparison with control mice. Furthermore, NK cells isolated from spleens of 5-FU + IFN-α treated mice showed enhanced cytotoxicity towards Panc02 cells. Moreover, 5-FU + IFN-α treatment increased the expression of MHC Class-I and NKG2D-ligands: MULT-1 and Rae-1 in Panc02 cells both in vitro and in vivo that could be the key for the enhanced recognition and per se killing by CD8+ T cells and NK cells respectively. Depletion of CD11c+ DCs did also abrogate the anti-cancer effects mediated by the combination therapy. The ongoing work will give more information about the role of CD11c+ DCs, CD4+ T cells and Tregs in orchestrating the immune response mediated by 5-FU + IFN-α. To conclude, this study gives more insight about the mechanism of action of INF-α in combination with 5-FU and introduces CD8+ T cells and NK cells as main players in the observed anti-cancer immune response. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1791. doi:10.1158/1538-7445.AM2011-1791