DMXAA Causes Tumor Site-Specific Vascular Disruption in Murine Non-Small Cell Lung Cancer, and like the Endogenous Non-Canonical Cyclic Dinucleotide STING Agonist, 2′3′-cGAMP, Induces M2 Macrophage Repolarization

Abstract

The vascular disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a murine agonist of the stimulator of interferon genes (STING), appears to target the tumor vasculature primarily as a result of stimulating pro-inflammatory cytokine production from tumor-associated macrophages (TAMs). Since there were relatively few reports of DMXAA effects in genetically-engineered mutant mice (GEMM), and models of non-small cell lung cancer (NSCLC) in particular, we examined both the effectiveness and macrophage dependence of DMXAA in various NSCLC models. The DMXAA responses of primary adenocarcinomas in K-rasLA1/+ transgenic mice, as well as syngeneic subcutaneous and metastatic tumors, generated by a p53R172HΔg/+; K-rasLA1/+ NSCLC line (344SQ-ELuc), were assessed both by in vivo bioluminescence imaging as well as by histopathology. Macrophage-dependence of DMXAA effects was explored by clodronate liposome-mediated TAM depletion. Furthermore, a comparison of the vascular structure between subcutaneous tumors and metastases was carried out using micro-computed tomography (micro-CT). Interestingly, in contrast to the characteristic hemorrhagic necrosis produced by DMXAA in 344SQ-ELuc subcutaneous tumors, this agent failed to cause hemorrhagic necrosis of either 344SQ-ELuc-derived metastases or autochthonous K-rasLA1/+ NSCLCs. In addition, we found that clodronate liposome-mediated depletion of TAMs in 344SQ-ELuc subcutaneous tumors led to non-hemorrhagic necrosis due to tumor feeding-vessel occlusion. Since NSCLC were comprised exclusively of TAMs with anti-inflammatory M2-like phenotype, the ability of DMXAA to re-educate M2-polarized macrophages was examined. Using various macrophage phenotypic markers, we found that the STING agonists, DMXAA and the non-canonical endogenous cyclic dinucleotide, 2′3′-cGAMP, were both capable of re-educating M2 cells towards an M1 phenotype. Our findings demonstrate that the choice of preclinical model and the anatomical site of a tumor can determine the vascular disrupting effectiveness of DMXAA, and they also support the idea of STING agonists having therapeutic utility as TAM repolarizing agents.

Stimulating Innate Immunity to Enhance Radiation Therapy–Induced Tumor Control

“…In addition, TNFα can induce cancer cell apoptosis. As described above, TNFα-mediated hemorrhagic necrosis of tumors has been described following administration of STING ligands, LPS, poly(I:C) and CpG 119,130,161,162 . However, the lower levels of endogenous TNFα produced by macrophages in the tumor environment has been shown to promote tumor regrowth following radiation therapy 163 .…”

“…In addition, direct injection of CDN into tumors has been shown to cause dramatic regression in a range of tumor models 126 . Interestingly, STING was recently found to be the gene activated by DMXAA 129 , which is a highly active vascular disrupting agent resulting in hemorrhagic necrosis of tumors, though with variable results depending on the tumor model 130 . DMXAA activates mouse, but not human STING 131 , potentially explaining the failure in clinical translation of DMXAA.…”

“…This contrasts with type II IFN, or IFNγ, which signals through IFNGR1 and IFNGR2, and type III IFN, that includes IFN-lambda and IL-10 136,137 and signals through two α subunits and two β subunits. The ability to produce and respond to type I IFN is shared by almost all cell types, though plasmacytoid dendritic cells are able to secrete higher levels of type I IFN than any other cell type 130,139 . Activation of IFN receptors leads to a multifaceted response.…”

Synthesis and anticancer activities of 3-arylflavone-8-acetic acid derivatives

“…As a consequence, some flavonoids have been screened in clinical trials for the treatment of cancers [6][7][8]. For example, it has been reported that 5, 6-dimethylxanthenone-4-acetic acid (DMXAA, 1, Figure 1), an analogue of flavone acetic acid (FAA, 2) is a vascular disrupting agent which specifically targets immature and unstable vasculature of solid tumors, leading to thrombosis, hemorrhage and necrosis [9][10][11]. In addition, it has been shown that DMXAA 1 is safe and well-tolerated in humans [6,7,12].…”

A High Content Screen in Macrophages Identifies Small Molecule Modulators of STING-IRF3 and NFkB Signaling

“…Direct STING agonists are currently in clinical trial in cancer, based on the hypothesis that activation of the STING pathway will trigger anti-tumor innate immune responses (11,12,13,14). Inappropriate activation of the STING pathway has been implicated in sterile inflammatory disease, notably the inherited condition “STING-associated vasculopathy with onset in Infancy (SAVI)” (4).…”