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Abstract 1237: Down-regulation of chemokine receptor CXCR4 by gambogic acid suppresses metastasis of pancreatic cancer in an orthotopic mouse model

More than 90% of patients die of pancreatic cancer due to metastasis. Among the cytokines, CXCL12 and its CXC chemokine receptor 4 (CXCR4) are known to play a role in invasion and metastasis in many types of cancer. Thus, agents that can interrupt the CXCR4/CXCL12 signaling cascade have the potential to suppress cancer metastasis. In the present study, we demonstrate that gambogic acid (GA), a xanthone from Gamboge hanburyi, down-regulated CXCR4 expression in pancreatic cancer cells in a dose- and time-dependent manner. We found that the decrease in CXCR4 by GA was not specific to cell type since its expression was abrogated in multiple myeloma cell lines and in colorectal, head and neck, prostate, and breast cancer cell lines. Furthermore, down-regulation of CXCR4 was not due to proteolytic degradation since proteasome inhibitors had no effect. Instead, the down-regulation of CXCR4 was due to transcriptional regulation, as indicated by the corresponding down-regulation of mRNA expression. This xanthone also inhibited the invasion of pancreatic tumor cells in vitro. Down-regulation of CXCR4 and prevention of cell invasion by the xanthone were both found to be mediated through the reactive oxygen species (ROS) as N-acetylcysteine, a ROS quencher, abolished these effects. When examined in an orthotopic nude mouse model of human pancreatic cancer, intraperitoneal administration of GA suppressed both tumor growth and metastasis. Immunohistochemical analysis of tumor tissue showed that besides decreasing the level of CXCR4, GA also reduced the expression of VEGF and MMP-9, which are also linked to invasion and metastasis. Thus, our results demonstrate gambogic acid’s potential in suppressing tumor invasion and metastasis through down-modulation of CXCR4/CXCL12 signaling pathways. Citation Format: Sahdeo Prasad, Sanjay Srivastava. Down-regulation of chemokine receptor CXCR4 by gambogic acid suppresses metastasis of pancreatic cancer in an orthotopic mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1237.