Combination of RAGE Inhibitors and Gemcitabine Impedes Tumor Growth by Reducing Autophagy and Facilitating Apoptosis in Pancreatic Cancer

Abstract

Pancreatic cancer (PC) is a lethal disease with the current 5-year survival of only about 8%. Despite decades of research, gemcitabine remains the standard of therapy for PC. However, after an initial good response, eventual development of chemo-resistance is a major challenge faced by gemcitabine therapy. One principal cause of chemo-resistance is the release of high mobility group box 1 (HMGB1) protein from dying tumor cells, upon treatment with gemcitabine. When released, HMGB1 interacts with the receptor for advanced glycation end-products (RAGE), stimulating distinct signaling pathways leading to increased autophagy and tumor cell proliferation along with a reduction in apoptosis. RAGE activation by HMGB1 thereby supports tumor cell survival, making the tumor less sensitive towards gemcitabine. We hypothesized that inhibiting RAGE-HMGB1 interaction, in combination with gemcitabine therapy could reduce autophagy and tumor cell proliferation as well as facilitate apoptosis. This would ultimately reduce chemo-resistance and make pancreatic tumor more sensitive towards gemcitabine therapy. In our study, we intended to determine the efficacy of RAGE inhibitors (anti-RAGE antibody IgG2A11 and small molecule RAGE inhibitor FPS-ZM1) in combination with gemcitabine in PC. We employed an orthotopic mouse model of PC to test our hypothesis. In this model, the murine #5508 KPC pancreatic cancer cell line was implanted in the pancreas of C57BL/6 mice. The implanted mice received different treatments (saline, RAGE inhibitor, gemcitabine or gemcitabine with RAGE inhibitor). At the end of the study, tumors obtained from different treatment groups were assessed for their weight. Additionally, these tumors were analyzed for the expression of markers of autophagy, cell proliferation and apoptosis by western blot. We observed smaller tumors in mice treated with the combination of anti-RAGE antibody IgG2A11 & gemcitabine as well as lower levels of phosphorylated ERK in the combination treated group. This data was presented at “EB 2018” conference. We now show that the smaller tumors in the combination group are also associated with an increase in p62 levels, supporting a reduction in autophagy. In addition, we observed higher levels of cleaved PARP in this combination group suggesting higher levels of apoptosis in tumor cells. In our second study where we used the small molecule RAGE inhibitor FPS-ZM1 in combination with gemcitabine, we also observed significantly smaller tumors in the combination group as compared to the gemcitabine alone treatment group. In conclusion, our data strongly suggests that inhibiting RAGE in combination with gemcitabine could be a valid therapeutic approach for the treatment of pancreatic adenocarcinoma. Support or Funding Information This work was in part supported by the College of Health Professions at NDSU and by the NIH Grant Number P20GM109024 from the National Institute of General Medicine (NIGMS). This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.