Reduction-oxidation factor 1-apurinic/apyrimidinic endonuclease (Ref-1/APE1) is a critical node in tumor cells, both as a redox regulator of transcription factor activation and as part of the DNA damage response. As a redox signaling protein, Ref-1/APE1 enhances the transcriptional activity of STAT3, HIF-1α, nuclear factor kappa B, and other transcription factors to promote growth, migration, and survival in tumor cells as well as inflammation and angiogenesis in the tumor microenvironment. Ref-1/APE1 is activated in a variety of cancers, including prostate, colon, pancreatic, ovarian, lung and leukemias, leading to increased aggressiveness. Transcription factors downstream of Ref-1/APE1 are key contributors to many cancers, and Ref-1/APE1 redox signaling inhibition slows growth and progression in a number of tumor types. Ref-1/APE1 inhibition is also highly effective when paired with other drugs, including standard-of-care therapies and therapies targeting pathways affected by Ref-1/APE1 redox signaling. Additionally, Ref-1/APE1 plays a role in a variety of other indications, such as retinopathy, inflammation, and neuropathy. In this review, we discuss the functional consequences of activation of the Ref-1/APE1 node in cancer and other diseases, as well as potential therapies targeting Ref-1/APE1 and related pathways in relevant diseases. APX3330, a novel oral anticancer agent and the first drug to target Ref-1/APE1 for cancer is entering clinical trials and will be explored in various cancers and other diseases bringing bench discoveries to the clinic.

The cellular transduction mechanisms underlying the response of blood vessels to mechanical forces such as pressure or stretch are largely unknown. In this report we test the hypothesis that myogenic tone in the cerebral circulation is coupled to activation of phospholipase C (PLC) and G proteins. Rat posterior cerebral arteries (luminal diam 189 +/- 4 microns) were cannulated in an arteriograph and allowed to develop myogenic tone at 75 mmHg (122 +/- 6 microns; P < 0.01). Exposure to U-73122, an inhibitor of PLC, produced concentration-dependent vasodilation, with near-maximal (> 90%) inhibition at concentrations > 3 microM (50% inhibitory concentration = 0.8 +/- 0.04 microM). The action of U-73122 was confirmed by demonstrating that constrictor responses to serotonin (PLC mediated) could be significantly attenuated or abolished at concentrations (0.5-1 microM) that were ineffective in antagonizing potassium depolarization or indolactam-induced constrictions (both PLC independent). Incubation in pertussis toxin (100 ng/ml, 2-2.5 h), an inhibitor of some G protein subtypes, reduced myogenic tone by 74 +/- 12%, with luminal diameters increasing from 129 +/- 7 to 160 +/- 7 microns. Conversely, nonspecific G protein activation using AlF-4 (NaF+AlCl3, 0.5-5 mM) significantly increased myogenic tone by 86 +/- 9%, reducing luminal diameters from 132 +/- 6 to 88 +/- 8 microns (P < 0.01). Together, these findings suggest that 1) PLC is activated in arteries that possess myogenic tone, 2) pharmacological inhibition of PLC results in a virtual loss of pressure-induced constriction, and 3) G proteins may modulate mechanotransduction through pathways superimposed on basal myogenic tone.

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Ocular neovascular diseases like wet age-related macular degeneration are a major cause of blindness. Novel therapies are greatly needed for these diseases. One appealing antiangiogenic target is reduction-oxidation factor 1-apurinic/apyrimidinic endonuclease 1 (Ref-1/APE1). This protein can act as a redox-sensitive transcriptional activator for nuclear factor (NF)-B and other proangiogenic transcription factors. An existing inhibitor of Ref-1's function, APX3330, previously showed antiangiogenic effects. Here, we developed improved APX3330 derivatives and assessed their antiangiogenic activity. We synthesized APX2009 and APX2014 and demonstrated enhanced inhibition of Ref-1 function in a DNA-binding assay compared with APX3330. Both compounds were antiproliferative against human retinal microvascular endothelial cells (HRECs; GI APX2009: 1.1 M, APX2014: 110 nM) and macaque choroidal endothelial cells (Rf/6a; GI APX2009: 26 M, APX2014: 5.0M). Both compounds significantly reduced the ability of HRECs and Rf/6a cells to form tubes at mid-nanomolar concentrations compared with control, and both significantly inhibited HREC and Rf/6a cell migration in a scratch wound assay, reducing NF-B activation and downstream targets. Ex vivo, APX2009 and APX2014 inhibited choroidal sprouting at low micromolar and high nanomolar concentrations, respectively. In the laser-induced choroidal neovascularization mouse model, intraperitoneal APX2009 treatment significantly decreased lesion volume by 4-fold compared with vehicle ( < 0.0001, ANOVA with Dunnett's post-hoc tests), without obvious intraocular or systemic toxicity. Thus, Ref-1 inhibition with APX2009 and APX2014 blocks ocular angiogenesis in vitro and ex vivo, and APX2009 is an effective systemic therapy for choroidal neovascularization in vivo, establishing Ref-1 inhibition as a promising therapeutic approach for ocular neovascularization.