P06.11 Exploration of the involvement of receptor for advanced glycation end-products (RAGE) signaling in the regulation of tumor immunity by isoliquiritigenin in pancreatic cancer cells

Background We have recently confirmed that the novel autophagy regulator isoliquiritigenin (ISL) could act as inhibitor of the KRAS downstream executor Rac1 in treating pancreatic cancer. Receptor of Advanced Glycation End production (RAGE), another upstream regulator of Rac1, is a member of the immunoglobulin superfamily that is overexpressed during cancer development in the tumor microenvironment (TME). In this study, we have investigated the involvement of RAGE in the anti-neoplastic activity of ISL in association with regulation of the tumor immunity in pancreatic ductal adenocarcinoma (PDAC) cells.Materials and methods Cell migratory activity was determined in PANC1 PDAC cells by using Wound healing assay. Protein expression of various tumor immunity biomarkers and metastatic mediators were determined by Western immunoblotting.Results We recently reported that ISL inhibited the protein expression of Rac1 and EMT/pro-migratory biomarkers in PDAC cells. Molecular docking and dynamic simulation tests had confirmed that ISL has a strong covalent binding and active interaction with RAGE. In both PANC and MIA-PaCa2 PDAC cells, ISL downregulated both gene and protein expression of RAGE and its ligand HMGB1, with concurrent upregulation of PTEN and mTOR (in PI3K-Akt pathway). ISL also decreased the protein expression of JAK1, STAT3, STAT1, p-STAT1 as well as the anti-apoptotic factor BCL-xL in PANC-1 cells. RAGE and JAK-STAT signaling work together to affect T-cell infiltration and is involved in tumor immunosuppression in the TME. Here, we discovered that ISL reduced the protein expression of CD63 (critical for mediating KRAS-mutated PDAC cell response to macrophage induction) and CD68 (known to regulate tumor immunity including CD4+ and CD8+ T cells in the TME as immune checkpoint in cancer treatments to enhance cell proliferation and migration). Alternatively, CD26 protein expression was increased only modestly by ISL. Since serum CD26 level was proposed to be associated with favorable clinicopathological features in pancreatic cancer patients, its gene expression level in tumor and serum of xenografted animals following ISL treatment needs to be measured to verify its implication. Our preliminary studies have indicated that CD9 (expressed in tumor-initiating cells or cancer stem cells of pancreatic cancer) and CD98 (transmembrane protein acting as driver of integrin-dependent metastasis) levels were found to be reduced slightly by ISL. We will detect their gene expression levels to confirm our findings.Conclusion Our results have revealed that ISL suppressed EMT and migratory activity in PDAC cells by inhibition of RAGE involving restoration of apoptosis through modulation of JAK-STAT and PI3K-Akt-mTOR signaling. ISL may also act by regulation of tumor immunity, directly or via RAGE inhibition, as inhibitor that neutralizes CD63 and CD68 in the TME of PDAC, providing a new direction for tumor immunotherapy.