New Ref-1/APE1 targeted inhibitors demonstrating improved potency for clinical applications in multiple cancer types

Ref-1 redox activity modulates canonical Wnt signaling in endothelial cells

Ischemic retinopathies, including proliferative diabetic retinopathy (PDR) and retinopathy of prematurity (ROP), are characterized by abnormal retinal neovascularization and can lead to blindness in children and adults. Current treatments, such as intravitreal anti-VEGF injections, face limitations due to high treatment burden and variable efficacy, as multiple signaling pathways, beyond VEGF, contribute to retinal neovascularization. Previous studies demonstrate that targeting the redox-mediated transcriptional regulatory function of APE1/Ref-1 reduces pathological neovascularization. We aimed to identify novel signaling pathways regulated by Ref-1 redox activity utilizing RNA sequencing of human retinal endothelial cells (HRECs) treated with a Ref-1 redox inhibitor. We found that Wnt/β-catenin signaling was significantly downregulated after Ref-1 inhibition. Given the role of Wnt signaling in vascular pathologies, we investigated how Ref-1 regulates Wnt/β-catenin signaling. Ref-1 inhibition downregulated Wnt co-receptors LRP5/6 at both the mRNA and protein levels in endothelial cells, suggesting transcriptional regulation. Ref-1 redox inhibitors APX3330 and APX2009 reduced Wnt3a-induced nuclear β-catenin levels, decreased Wnt transcriptional activity by TOPFlash luciferase assay, and blocked hypoxia-induced Wnt/β-catenin activation in HRECs. In the oxygen-induced retinopathy mouse model of retinal neovascularization, Ref-1 specific inhibitor APX2009 reduced the expression of Wnt-related genes at sites of neovascularization. These findings reveal a novel role for Ref-1 redox activity in modulating Wnt/β-catenin signaling in endothelial cells and highlight the potential of Ref-1 redox activity targeted inhibitors as a novel therapeutic approach for retinal neovascular diseases by modulating multiple disease-relevant pathways.

DLK1 Distinguishes Subsets of NF1-Associated Malignant Peripheral Nerve Sheath Tumors with Divergent Molecular Signatures

PURPOSE

Malignant peripheral nerve sheath tumor (MPNST) is the leading cause of premature death among individuals with neurofibromatosis type 1 (NF1), and the transcriptional aberrations that precede malignant transformation and contribute to MPNST tumorigenesis remain poorly defined. Alterations involving CDKN2A and components of PRC2 have been implicated as early drivers of peripheral nerve sheath tumor (PNST) evolution, but these events do not occur in all MPNST. Accordingly, emerging data have begun to highlight the importance of molecular-based stratification to improve outcomes in patients with NF1-PNST.

EXPERIMENTAL DESIGN

In this study, we perform an integrated analysis of multiple, independent datasets obtained from human patients with NF1 to gain critical insights into PNST evolution and MPNST heterogeneity.

RESULTS

We show that delta-like noncanonical Notch ligand 1 (DLK1) is significantly increased in MPNST and provide evidence that DLK1 overexpression may precede histologic changes consistent with malignancy. In complementary analyses, we find that serum levels of DLK1 are significantly higher in both mice and humans harboring MPNST compared with those without malignancy. Importantly, although DLK1 expression is increased in MPNST overall, through the integration of multiple, independent datasets, we demonstrate that divergent levels of DLK1 expression distinguish MPNST subsets characterized by unique molecular programs and potential therapeutic vulnerabilities. Specifically, we show that overexpression of DLK1 is associated with the reactivation of embryonic signatures, an immunosuppressive microenvironment, and a worse overall survival in patients with NF1-MPNST.

CONCLUSIONS

Collectively, our findings provide critical insights into MPNST tumorigenesis and support prospective studies evaluating the utility of DLK1 tissue and serum levels in augmenting diagnosis, risk assessment, and therapeutic stratification in the setting of NF1-PNST.

L-741626 inhibits hepatocellular carcinoma progression by targeting Ref-1 to suppress MAPK/ERK signalling pathway activity

Hepatocellular carcinoma (HCC) is a common and challenging malignancy of the digestive tract. Unfortunately, patients with advanced HCC frequently experience limited long-term benefits from current treatments, highlighting the critical need for innovative therapeutic agents. The discovery and development of new small-molecule compounds that target tumours have become crucial aspects of cancer research. In this study, we report on L-741626, a compound that has significant inhibitory effects on HCC. Both in vivo and in vitro experiments confirmed that L-741626 inhibited the growth of HCC by suppressing the MAPK/ERK signalling pathway. Molecular docking simulations and drug affinity responsive target stability assays further identified redox Factor 1 (Ref-1) as a target of L-741626. Ref-1 is overexpressed in HCC and is correlated with poor prognosis and high stage. Further studies demonstrated that Ref-1 interacts with CRAF, a crucial component of the MAPK/ERK signalling pathway. Knockdown of Ref-1 in HCC cells led to inhibition of the MAPK/ERK pathway. Sorafenib is a well-established targeted therapy for the treatment of HCC, with its primary antitumor mechanism being the inhibition of the MAPK/ERK signalling pathway. However, the presence of tumor stem cells is a key factor contributing to resistance to sorafenib. Our study demonstrates that L-741626 can suppress tumor stemness in HCC. The combination of L-741626 and sorafenib significantly enhances the sensitivity of HCC, resulting in increased tumoricidal effects. Our findings reveal a novel pharmacological effect of L-741626, which inhibits MAPK/ERK signalling activity in HCC by targeting Ref-1. Furthermore, L-741626 exhibits a synergistic effect when combined with sorafenib, suggesting a new potential approach for HCC treatment.

A Phase I study targeting the APE1/Ref-1 redox signaling protein with APX3330: First clinical agent targeting APE1/Ref-1 in Cancer

Purpose

APX3330 is an oral agent targeting the redox signaling activity of Ape1/Ref-1 (Ref-1), a key regulator of transcription factors involved in inflammation and tumorigenesis. APX3330 selectively inhibits Ref-1's redox function without affecting its DNA repair role. This Phase 1, multicenter, open-label, dose-escalation study in advanced solid tumor was aimed at determining the recommended Phase 2 dose (RP2D) while assessing safety, pharmacokinetics, and biomarker evidence of target engagement. Clinical trial: NCT03375086 .

Patients and Methods

Nineteen cancer patients were treated, with eight completing follow-up. Subjects received APX3330 orally twice daily in 21-day cycles, starting at 240 mg/day and escalating in 120 mg/day increments. Adverse event (AE) monitoring followed a 1 pt/cohort approach until a >G2 toxicity event, after which a 3+3 design was implemented. Treatment continued until disease progression, consent withdrawal, or intolerable toxicity. Antitumor activity was assessed using RECIST 1.1, and pharmacodynamic markers included serum Ref-1 levels and circulating tumor cells.

Results

Six subjects had stable disease for >4 cycles, with four remaining on study for 252- 421 days. No treatment-related serious adverse events occurred. One subject (720 mg cohort) withdrew due to Grade 3 maculopapular rash (dose-limiting toxicity). Laboratory assessments and ECGs showed no clinically significant abnormalities.

Conclusions

APX3330 demonstrated clinical benefit by stabilizing disease in ∼33% of subjects. Ref-1 target engagement was confirmed via biomarker analyses, with reduced serum Ref-1 and circulating tumor cells. The RP2D is 600 mg daily, with APX3330 showing a favorable safety profile and target-mediated effects.

Interface-driven structural evolution on diltiazem as novel uPAR inhibitors: from in silico design to in vitro evaluation

The urokinase-type plasminogen activator receptor (uPAR) emerges as a key target for anti-metastasis owing to its pivotal role in facilitating the invasive and migratory processes of cancer cells. Recently, we identified the uPAR-targeting anti-metastatic ability of diltiazem (22), a commonly used antihypertensive agent. Fine-tuning the chemical structures of known hits represents a vital branch of drug development. To develop novel anti-metastatic drugs, we performed an interface-driven structural evolution strategy on 22. The uPAR-targeting and anti-cancer abilities of this antihypertensive drug wereidentified by us recently. Based on in silico strategy, including extensive molecular dynamics (MD) simulations, hierarchical binding free energy predictions, and ADMET profilings, we designed, synthesized, and identified three new diltiazem derivatives (221-8, 221-57, and 221-68) as uPAR inhibitors. Indeed, all of these three derivatives exhibited uPAR-depending inhibitory activity against PC-3 cell line invasion at micromolar level. Particularly, derivatives 221-68 and 221-8 showed enhanced uPAR-dependent inhibitory activity against the tumor cell invasion compared to the original compound. Microsecond timesclae MD simulations demonstrated the optimized moiety of 221-68 and 221-8 forming more comprehensive interactions with the uPAR, highlighting the reasonability of our strategy. This work introduces three novel uPAR inhibitors, which not only pave the way for the development of effective anti-metastatic therapeutics, but also emphasize the efficacy and robustness of an in silico-based lead compound optimization strategy in drug design.

Ref-1 redox activity regulates retinal neovascularization by modulating transcriptional activation of HIF-1α

Retinal neovascularization impairs visual function and is a hallmark of several neovascular eye diseases, including retinopathy of prematurity (ROP) and proliferative diabetic retinopathy (PDR). Current treatments include intravitreal injections of anti-vascular endothelial growth factor (VEGF) biologics, but these therapeutics are often accompanied by high treatment burden and resistance to therapy. Prior studies indicate that APE1/Ref-1, a multifunctional protein with both endonuclease (APE1) and redox-mediated transcriptional regulatory activity (Ref-1), activates multiple pro-angiogenic and pro-inflammatory signaling pathways by chemically reducing key cysteine residues in transcription factors, thereby activating them. Here, we investigated the previously unexplored role of Ref-1 in retinal neovascularization. We demonstrate that Ref-1 is highly expressed in endothelial cells in human PDR and in the oxygen-induced retinopathy (OIR) mouse model of retinal neovascularization. Ref-1 is also highly expressed in microglia and astrocytes in OIR. A small molecule Ref-1 redox inhibitor, APX2009, decreased retinal neovascularization in OIR after systemic delivery. In vitro, hypoxic endothelial cells did not exhibit upregulation of Ref-1 but rather increased Ref-1 nuclear localization. APX2009 decreased hypoxic endothelial cell proliferation and HIF-1α transcriptional activation. Thus, Ref-1 redox activity may be a novel therapeutic target for the treatment of retinal neovascularization, making APX2009 a promising systemic therapeutic approach for the treatment of vascular retinopathies such as ROP and PDR.

Ref-1 is overexpressed in neovascular eye disease and targetable with a novel inhibitor

Reduction-oxidation factor-1 or apurinic/apyrimidinic endonuclease 1 (Ref-1/APE1) is a crucial redox-sensitive activator of transcription factors such as NF-κB, HIF-1α, STAT-3 and others. It could contribute to key features of ocular neovascularization including inflammation and angiogenesis; these underlie diseases like neovascular age-related macular degeneration (nAMD). We previously revealed a role for Ref-1 in the growth of ocular endothelial cells and in choroidal neovascularization (CNV). Here, we set out to further explore Ref-1 in neovascular eye disease. Ref-1 was highly expressed in human nAMD, murine laser-induced CNV and Vldlr-/- mouse subretinal neovascularization (SRN). Ref-1's interaction with a redox-specific small molecule inhibitor, APX2009, was shown by NMR and docking. This compound blocks crucial angiogenic features in multiple endothelial cell types. APX2009 also ameliorated murine laser-induced choroidal neovascularization (L-CNV) when delivered intravitreally. Moreover, systemic APX2009 reduced murine SRN and downregulated the expression of Ref-1 redox regulated HIF-1α target carbonic anhydrase 9 (CA9) in the Vldlr-/- mouse model. Our data validate the redox function of Ref-1 as a critical regulator of ocular angiogenesis, indicating that inhibition of Ref-1 holds therapeutic potential for treating nAMD.

Apex1 safeguards genomic stability to ensure a cytopathic T cell fate in autoimmune disease models

T cells have a remarkable capacity to clonally expand, a process that is intricately linked to their effector activities. As vigorously proliferating T cell also incur substantial DNA lesions, how the dividing T cells safeguard their genomic integrity to allow the generation of T effector cells remains largely unknown. Here we report the identification of the apurinic/apyrimidinic endonuclease-1 (Apex1) as an indispensable molecule for the induction of cytopathic T effectors in mouse models. We demonstrate that conditional deletion of Apex1 in T cells resulted in a remarkable accumulation of baseless DNA sites in the genome of proliferating T cells, which further led to genomic instability and apoptotic cell death. Consequently, Apex1-deleted T cells failed to acquire any effector features after activation and failed to mediate autoimmune diseases and allergic tissue damages. Detailed mutational analyses pinpointed the importance of its endonuclease domain in the generation of T effector cells. We provide further evidence that inhibiting the base repair activities of Apex1 with chemical inhibitors similarly abrogated the induction of autoimmune diseases. Collectively, our study suggests that Apex1 serves as a gatekeeper for the generation of cytopathic T cells and that therapeutically targeting Apex1 may have important clinical implications in the treatment of autoimmune diseases.

[Analysis of clinical features, treatment methods, and prognostic influence factors in patients with malignant peripheral nerve sheath tumor]

Objective

To investigate the clinical features, treatment methods, and prognostic influence factors of patients with malignant peripheral nerve sheath tumor (MPNST).

Methods

A retrospective analysis was conducted on 96 MPNST patients treated between January 1, 2015 and December 31, 2021. There were 46 males and 50 females, aged between 15 and 87 years (mean, 48.2 years). The tumors were located in the trunk in 50 cases, extremities in 39 cases, and head and neck in 7 cases. The maximum tumor diameter was <5 cm in 49 cases, ≥5 cm in 32 cases, with 15 cases missing data. Tumor depth was deep in 77 cases and superficial in 19 cases. The Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC) histological grading was G1 in 9 cases, G2 in 12 cases, and G3 in 34 cases, with 41 cases missing data. There were 37 recurrent MPNST cases, 32 cases with neurofibromatosis type 1 (NF1), and 26 cases in stage Ⅳ. Postoperative adjuvant radiotherapy was administered to 25 patients, perioperative chemotherapy to 45 patients, and anlotinib-targeted therapy to 30 patients. R 0 resection was achieved in 73 cases. Patients were divided into groups based on the presence or absence of NF1, and baseline data between the two groups were compared. Kaplan-Meier curves were generated to assess disease-free survival (DFS) and overall survival (OS) based on various factors (age, gender, presence of NF1, recurrent MPNST, stage Ⅳ MPNST, FNCLCC grade, R 0 resection, tumor location, tumor size, tumor depth, perioperative chemotherapy, postoperative adjuvant radiotherapy, and anlotinib-targeted therapy), and differences between survival curves were analyzed using the Log-Rank test. Multivariate COX proportional hazards regression was used to identify independent prognostic factors for MPNST.

Results

Patients with NF1 had a significantly higher proportion of superficial tumors and lower FNCLCC grade compared to those without NF1 ( P<0.05); no significant difference was found for other variables ( P<0.05). Kaplan-Meier analysis showed that recurrent MPNST, stage Ⅳ MPNST, FNCLCC grade, R 0 resection, perioperative chemotherapy, and anlotinib-targeted therapy were factors influencing 1-year DFS ( P<0.05), while stage Ⅳ MPNST, FNCLCC grade, and perioperative chemotherapy were factors affecting 3-year OS ( P<0.05). Multivariate COX proportional hazards regression analysis revealed that recurrent MPNST and high-grade FNCLCC (G3) were independent prognostic factors for 1-year DFS ( P<0.05), while stage Ⅳ MPNST, superficial tumor depth, age over 60 years, postoperative adjuvant radiotherapy, and anlotinib-targeted therapy were independent prognostic factors for 3-year OS ( P<0.05).

Conclusion

MPNST patients with NF1 tend to have more superficial tumors and lower FNCLCC grades. FNCLCC grade, R 0 resection, and adjuvant therapies, including radiotherapy and anlotinib-targeted therapy, are closely associated with MPNST prognosis. Complete surgical resection should be prioritized in clinical management, along with adjuvant treatments such as radiotherapy and targeted therapy of anlotinib to improve patient outcomes.

Advancements in a novel model of autophagy and immune network regulation in radioresistance of cancer stem cells

Radiotherapy, a precise modality for treating malignant tumors, has undergone rapid advancements in primary and clinical research. The mechanisms underlying tumor radioresistance have become significant research. With the introduction and in-depth study of cancer stem cells (CSCs) theory, CSCs have been identified as the primary factor contributing to the development of tumor radioresistance. The "stemness" of CSCs is a biological characteristic of a small subset of cells within tumor tissues, characterized by self-renewal solid ability. This characteristic leads to resistance to radiotherapy, chemotherapy, and targeted therapies, driving tumor recurrence and metastasis. Another study revealed that cellular autophagy plays a pivotal role in maintaining the "stemness" of CSCs. Autophagy is a cellular mechanism that degrades proteins and organelles to generate nutrients and energy in response to stress. This process maintains cellular homeostasis and contributes to CSCs radioresistance. Furthermore, ionizing radiation (IR) facilitates epithelial-to-mesenchymal transition (EMT), vascular regeneration, and other tumor processes by influencing the infiltration of M2-type tumor-associated macrophages (TAMs). IR promotes the activation of the classical immunosuppressive "switch," PD-1/PD-L1, which diminishes T-cell secretion, leading to immune evasion and promoting radioresistance. Interestingly, recent studies have found that the immune pathway PD-1/PD-L1 is closely related to cellular autophagy. However, the interrelationships between immunity, autophagy, and radioresistance of CSCs and the regulatory mechanisms involved remain unclear. Consequently, this paper reviews recent research to summarize these potential connections, aiming to establish a theoretical foundation for future studies and propose a new model for the network regulation of immunity, autophagy, and radioresistance of tumor cells.

AP endonuclease 1: Biological updates and advances in activity analysis

Apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1, APEX1, REF1, HAP1) is an abasic site-specific endonuclease holding critical roles in numerous biological functions including base excision repair, the DNA damage response, redox regulation of transcription factors, RNA processing, and gene regulation. Pathologically, APE1 expression and function is linked with numerous human diseases including cancer, highlighting the importance of sensitive and quantitative assays to measure APE1 activity. Here, we summarize biochemical and biological roles for APE1 and expand on the discovery of APE1 inhibitors. Finally, we highlight the development of assays to monitor APE1 activity, detailing a recently improved and stabilized DNA Repair Molecular Beacon assay to analyze APE1 activity. The assay is amenable to analysis of purified protein, to measure changes in APE1 activity in cell lysates, to monitor human patient samples for defects in APE1 function, or the cellular and biochemical response to APE1 inhibitors.

Fast-relaxing hydrogels with reversibly tunable mechanics for dynamic cancer cell culture

The mechanics of the tumor microenvironment (TME) significantly impact disease progression and the efficacy of anti-cancer therapeutics. While it is recognized that advanced in vitro cancer models will benefit cancer research, none of the current engineered extracellular matrices (ECM) adequately recapitulate the highly dynamic TME. Through integrating reversible boronate-ester bonding and dithiolane ring-opening polymerization, we fabricated synthetic polymer hydrogels with tumor-mimetic fast relaxation and reversibly tunable elastic moduli. Importantly, the crosslinking and dynamic stiffening of matrix mechanics were achieved in the absence of a photoinitiator, often the source of cytotoxicity. Central to this strategy was Poly(PEGA-co-LAA-co-AAPBA) (PELA), a highly defined polymer synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. PELA contains dithiolane for initiator-free gel crosslinking, stiffening, and softening, as well as boronic acid for complexation with diol-containing polymers to give rise to tunable viscoelasticity. PELA hydrogels were highly cytocompatible for dynamic culture of patient-derived pancreatic cancer cells. It was found that the fast-relaxing matrix induced mesenchymal phenotype of cancer cells, and dynamic matrix stiffening restricted tumor spheroid growth. Moreover, this new dynamic viscoelastic hydrogel system permitted sequential stiffening and softening to mimic the physical changes of TME.

Combating PDAC Drug Resistance: The Role of Ref-1 Inhibitors in Accelerating Progress in Pancreatic Cancer Research

Pancreatic Ductal Adenocarcinoma (PDAC) remains one of the most lethal solid tumor diagnoses given its limited treatment options and dismal prognosis. Its complex tumor microenvironment (TME), heterogeneity, and high propensity for drug resistance are major obstacles in developing effective therapies. Here, we highlight the critical role of Redox effector 1 (Ref-1) in PDAC progression and drug resistance, focusing on its redox regulation of key transcription factors (TFs) such as STAT3, HIF1α, and NF-κB, which are pivotal for tumor survival, proliferation, and immune evasion. We discuss the development of novel Ref-1 inhibitors, including second-generation compounds with enhanced potency and improved pharmacokinetic profiles, which have shown significant promise in preclinical models. These inhibitors disrupt Ref-1's redox function, leading to decreased TF activity and increased chemosensitivity in PDAC cells. We further detail our utilization of advanced preclinical models, such as 3D spheroids, organoids, and Tumor-Microenvironment-on-Chip (T-MOC) systems, which better simulate the complex conditions of the PDAC TME and improve the predictive power of therapeutic responses. By targeting Ref-1 and its associated pathways, in conjunction with improved models, more replicative of PDAC's TME, we are focused on approaches which hold the potential to overcome current therapeutic limitations and advance the development of more effective treatments for PDAC. Our findings suggest that integrating Ref-1 inhibitors into combination therapies could disrupt multiple survival mechanisms within the tumor, offering new hope for improving outcomes in this challenging cancer.