MTH1 Inhibitor TH1579 Induces Oxidative DNA Damage and Mitotic Arrest in Acute Myeloid Leukemia

MTH1 inhibition synergizes with ROS-inducing agents to trigger cervical cancer cells undergoing parthanatos

Cervical cancer cells possess high levels of reactive oxygen species (ROS); thus, increasing oxidative stress above the toxicity threshold to induce cell death is a promising chemotherapeutic strategy. However, the underlying mechanisms of cell death are elusive, and efficacy and toxicity issues remain. Within DNA, 8-oxo-7,8-dihydroguanine (8-oxoG) is the most frequent base lesion repaired by 8-oxoguanine glycosylase 1 (OGG1)-initiated base excision repair. Cancer cells also express high levels of MutT homolog 1 (MTH1), which prevents DNA replication-induced incorporation of 8-oxoG into the genome by hydrolyzing 8-oxo-7,8-dihydro-2'-deoxyguanosine 5'-triphosphate (8-oxo-dGTP). Here, we revealed that ROS-inducing agents triggered cervical cancer to undergo parthanatos, which was mainly induced by massive DNA strand breaks resulting from overwhelming 8-oxoG excision by OGG1. Furthermore, the MTH1 inhibitor synergized with a relatively low dose of ROS-inducing agents by enhancing 8-oxoG loading in the DNA. In vivo, this drug combination suppressed the growth of tumor xenografts, and this inhibitory effect was significantly decreased in the absence of OGG1. Hence, the present study highlights the roles of base repair enzymes in cell death induction and suggests that the combination of lower doses of ROS-inducing agents with MTH1 inhibitors may be a more selective and safer strategy for cervical cancer chemotherapy.

Mitotic MTH1 inhibitor TH1579 induces PD-L1 expression and inflammatory response through the cGAS-STING pathway

The mitotic MTH1 inhibitor TH1579 is a dual inhibitor that inhibits mitosis and incorporation of oxidative DNA damage and leads to cancer-specific cell death. The response to immune checkpoint inhibitor (ICI) treatment is often augmented by DNA damaging agents through the cGAS-STING pathway. This study investigates whether TH1579 can improve the efficacy of immune checkpoint blockades through its immunomodulatory properties. Various human and murine cancer cell lines were treated with mitotic MTH1i TH1579, and the expression of PD-L1 and T-cell infiltration-related chemokines was analysed by flow cytometry and real-time qPCR. Syngeneic mouse models were established to examine the combined effect of TH1579 and PD-L1 blockade. In our investigation, we found that TH1579 upregulates PD-L1 expression at both the protein and mRNA levels in human cancer cell lines. However, in murine cell lines, the increase was less pronounced. An in vivo experiment in a syngeneic mouse melanoma model showed that TH1579 treatment significantly increased the efficacy of atezolizumab, an anti-PD-L1 antibody, compared to vehicle or atezolizumab monotherapy. Furthermore, TH1579 exhibited immune-modulatory properties, elevating cytokines such as IFN-β and chemokines including CCL5 and CXCL10, in a cGAS-STING pathway-dependent manner. In conclusion, TH1579 has the potential to improve ICI treatment by modulating immune checkpoint-related proteins and pathways.

Oxidative stress is two-sided in the treatment of acute myeloid leukemia

INTRODUCTION

Oxidative stress caused by elevated ROS, as a novel therapeutic mechanism, has been implicated in various tumors including AML. AML cells are chronically under oxidative stress, yet overreliance on ROS production makes tumor cells increasingly vulnerable to further damage. Reducing the cytotoxic effect of ROS on normal cells while killing leukemia stem cell (LSC) with high levels of reactive oxygen species is a new challenge for oxidative stress therapy in leukemia.

METHODS

By searching literature databases, we summarized recent relevant studies. The relationship of ROS on AML genes, signaling pathways, and transcription factors, and the correlation of ROS with AML bone marrow microenvironment and autophagy were summarized. In addition, we summarize the current status of research on ROS and AML therapeutics. Finally, we discuss the research progress on redox resistance in AML.

RESULTS

This review discusses the evidence showing the link between redox reactions and the progression of AML and compiles the latest research findings that will facilitate future biological studies of redox effects associated with AML treatment.

CONCLUSION

We believe that exploiting this unique oxidative stress property of AML cells may provide a new way to prevent relapse and drug resistance.

Role of reactive oxygen species in myelodysplastic syndromes

Reactive oxygen species (ROS) serve as typical metabolic byproducts of aerobic life and play a pivotal role in redox reactions and signal transduction pathways. Contingent upon their concentration, ROS production not only initiates or stimulates tumorigenesis but also causes oxidative stress (OS) and triggers cellular apoptosis. Mounting literature supports the view that ROS are closely interwoven with the pathogenesis of a cluster of diseases, particularly those involving cell proliferation and differentiation, such as myelodysplastic syndromes (MDS) and chronic/acute myeloid leukemia (CML/AML). OS caused by excessive ROS at physiological levels is likely to affect the functions of hematopoietic stem cells, such as cell growth and self-renewal, which may contribute to defective hematopoiesis. We review herein the eminent role of ROS in the hematological niche and their profound influence on the progress of MDS. We also highlight that targeting ROS is a practical and reliable tactic for MDS therapy.

Cepharanthine synergizes with photodynamic therapy for boosting ROS-driven DNA damage and suppressing MTH1 as a potential anti-cancer strategy

OBJECTIVE

Photodynamic therapy (PDT) primarily treats skin diseases or cancer by generating reactive oxygen species (ROS) to damage cellular DNA, yet drug resistance limits its application. To tackle this problem, the present study was carried out to improve the efficacy of chlorin e6 (Ce6)-PDT using Cepharanthine (CEP) as well as to reveal the potential molecular mechanism.

MATERIALS AND METHODS

Lewis lung cancer cell line (LLC) was utilized as the cancer cell model. chlorin e6 (Ce6) acted as the photosensitizer to induce PDT. The in vitro anti-cancer efficacy was measured by CCK-8, Annexin-V/PI staining, and migration assay. The Ce6 uptake was observed using flow cytometry and confocal microscopy. The ROS generation was detected by the DCFH-DA probe. The analysis of MutT Homolog 1 (MTH1) expression, correlation, and prognosis in databases was conducted by bioinformatic. The MTH1 expression was detected through western blots (WB). DNA damage was assayed by WB, immunofluorescent staining, and comet assay.

RESULTS

Ce6-PDT showed robust resistance in lung cancer cells under certain conditions, as evidenced by the unchanged cell viability and apoptosis. The subsequent findings confirmed that the uptake of Ce6 and MTH1 expression was enhanced, but ROS generation with laser irradiation was not increased in LLC, which indicated that the ROS scavenge may be the critical reason for resistance. Surprisingly, bioinformatic and in vitro experiments identified that MTH1, which could prevent the DNA from damage of ROS, was highly expressed in lung cancer and thereby led to the poor prognosis and could be further up-regulated by Ce6 PDT. CEP exhibited a dose-dependent suppressive effect on the lung cancer cells. Further investigations presented that CEP treatment boosted ROS production, thereby resulting in DNA double-strand breakage (DDSB) with activation of MTH1, indicating that CEP facilitated Ce6-PDT-mediated DNA damage. Finally, the combination of CEP and Ce6-PDT exhibited prominent ROS accumulation, MTH1 inhibition, and anti-lung cancer efficacy, which had synergistic pro-DNA damage properties.

CONCLUSION

Collectively, highly expressed MTH1 and the failure of ROS generation lead to PDT resistance in lung cancer cells. CEP facilitates ROS generation of PDT, thereby promoting vigorous DNA damage, inactivating MTH1, alleviating PDT resistance, and ameliorating the anti-cancer efficacy of Ce6-PDT, provides a novel approach for augmented PDT.

Targeting the nucleic acid oxidative damage repair enzyme MTH1: a promising therapeutic option

The accumulation of reactive oxygen species (ROS) plays a pivotal role in the development of various diseases, including cancer. Elevated ROS levels cause oxidative stress, resulting in detrimental effects on organisms and enabling tumors to develop adaptive responses. Targeting these enhanced oxidative stress protection mechanisms could offer therapeutic benefits with high specificity, as normal cells exhibit lower dependency on these pathways. MTH1 (mutT homolog 1), a homolog of Escherichia coli's MutT, is crucial in this context. It sanitizes the nucleotide pool, preventing incorporation of oxidized nucleotides, thus safeguarding DNA integrity. This study explores MTH1's potential as a therapeutic target, particularly in cancer treatment, providing insights into its structure, function, and role in disease progression.

Chromosome 8p engineering reveals increased metastatic potential targetable by patient-specific synthetic lethality in liver cancer

Large-scale chromosomal aberrations are prevalent in human cancer, but their function remains poorly understood. We established chromosome-engineered hepatocellular carcinoma cell lines using CRISPR-Cas9 genome editing. A 33-mega-base pair region on chromosome 8p (chr8p) was heterozygously deleted, mimicking a frequently observed chromosomal deletion. Using this isogenic model system, we delineated the functional consequences of chr8p loss and its impact on metastatic behavior and patient survival. We found that metastasis-associated genes on chr8p act in concert to induce an aggressive and invasive phenotype characteristic for chr8p-deleted tumors. Genome-wide CRISPR-Cas9 viability screening in isogenic chr8p-deleted cells served as a powerful tool to find previously unidentified synthetic lethal targets and vulnerabilities accompanying patient-specific chromosomal alterations. Using this target identification strategy, we showed that chr8p deletion sensitizes tumor cells to targeting of the reactive oxygen sanitizing enzyme Nudix hydrolase 17. Thus, chromosomal engineering allowed for the identification of novel synthetic lethalities specific to chr8p loss of heterozygosity.

GNF-7, a novel FLT3 inhibitor, overcomes drug resistance for the treatment of FLT3‑ITD acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) with FMS-like tyrosine kinase 3 internal tandem duplication (FLT3-ITD) mutation accounts for a large proportion of AML patients and diagnosed with poor prognosis. Although the prognosis of FLT3-ITD AML has been greatly improved, the drug resistance frequently occurred in the treatment of FLT3 targeting drugs. GNF-7, a multitargeted kinase inhibitor, which provided a novel therapeutic strategy for overriding leukemia. In this study, we explored the antitumor activity of GNF-7 against FLT3-ITD and clinically-relevant drug resistance in FLT3 mutant AML.

METHODS

Growth inhibitory assays were performed in AML cell lines and Ba/F3 cells expressing various FLT3 mutants to evaluate the antitumor activity of GNF-7 in vitro. Western blotting was used to examine the inhibitory  effect of GNF-7 on FLT3 and its downstream pathways. Molecular docking and cellular thermal shift assay (CETSA) were performed to demonstrate the binding of FLT3 to GNF-7. The survival benefit of GNF-7 in vivo was assessed in mouse models of transformed Ba/F3 cells harboring FLT3-ITD and FLT3-ITD/F691L mutation. Primary patient samples and a patient-derived xenograft (PDX) model were also used to determine the efficacy of GNF-7.

RESULTS

GNF-7 inhibited the cell proliferation of Ba/F3 cells expressing FLT3-ITD and exhibited potently anti-leukemia activity on primary FLT3-ITD AML samples. Moreover, GNF-7 could bind to FLT3 protein and inhibit the downstream signaling pathway activated by FLT3 including STAT5, PI3K/AKT and MAPK/ERK. In vitro and in vivo studies showed that GNF-7 exhibited potent inhibitory activity against FLT3-ITD/F691L that confers resistant to quizartinib (AC220) or gilteritinib. Importantly, GNF-7 showed potent cytotoxic effect on leukemic stem cells, significantly extend the survival of PDX model and exhibited similar therapy effect compared with gilteritinib.

CONCLUSIONS

Our results show that GNF-7 is a potent FLT3-ITD inhibitor and may become a promising lead compound applied for treating some of the clinically drug resistant patients.

Targeting chemoresistance and mitochondria-dependent metabolic reprogramming in acute myeloid leukemia

Chemoresistance often complicates the management of cancer, as noted in the instance of acute myeloid leukemia (AML). Mitochondrial function is considered important for the viability of AML blasts and appears to also modulate chemoresistance. As mitochondrial metabolism is aberrant in AML, any distinct pathways could be directly targeted to impact both cell viability and chemoresistance. Therefore, identifying and targeting those precise rogue elements of mitochondrial metabolism could be a valid therapeutic strategy in leukemia. Here, we review the evidence for abnormalities in mitochondria metabolic processes in AML cells, that likely impact chemoresistance. We further address several therapeutic approaches targeting isocitrate dehydrogenase 2 (IDH2), CD39, nicotinamide phosphoribosyl transferase (NAMPT), electron transport chain (ETC) complex in AML and also consider the roles of mesenchymal stromal cells. We propose the term "mitotherapy" to collectively refer to such regimens that attempt to override mitochondria-mediated metabolic reprogramming, as used by cancer cells. Mounting evidence suggests that mitotherapy could provide a complementary strategy to overcome chemoresistance in liquid cancers, as well as in solid tumors.

Light-Elicited and Oxygen-Saved Iridium Nanocapsule for Oxidative Damage Intensified Oncotherapy

Regulating redox homeostasis in tumor cells and exploiting oxidative stress to damage tumors is an efficacious strategy for cancer therapy. However, the strengths of organic nanomaterials within this strategy are often ignored. In this work, a light-triggered reactive oxygen species (ROS) damaging nanoamplifier (IrP-T) was developed for enhanced photodynamic therapy (PDT). The IrP-T was fabricated with an amphiphilic iridium complex and a MTH1 inhibitor (TH287). Under green light stimulation, IrP-T catalyzed the oxygen in cells to generate ROS for realizing oxidative damage; meanwhile, TH287 increased the accumulation of 8-oxo-dGTP, further strengthening oxidative stress and inducing cell death. IrP-T could maximize the use of a small amount of oxygen, thus further boosting the efficacy of PDT in hypoxic tumors. The construction of nanocapsules provided a valuable therapeutic strategy for oxidative damage and synergizing PDT.

Emerging drugs targeting cellular redox homeostasis to eliminate acute myeloid leukemia stem cells

Acute myeloid leukemia (AML) is a very heterogeneous group of disorders with large differences in the percentage of immature blasts that presently are classified according to the specific mutations that trigger malignant proliferation among thousands of mutations reported thus far. It is an aggressive disease for which few targeted therapies are available and still has a high recurrence rate and low overall survival. The main reason for AML relapse is believed to be due to leukemic stem cells (LSCs) that have unlimited self-renewal capacity and long residence in a quiescent state, which promote greater resistance to traditional therapies for this cancer. AML LSCs have low oxidative stress levels, which appear to be caused by a combination of low mitochondrial activity and high activity of ROS-removing pathways. In this sense, oxidative stress has been thought to be an important new potential target for the treatment of AML patients, targeting the eradication of AML LSCs. The aim of this review is to discuss some drugs that induce oxidative stress to direct new goals for future research focusing on redox imbalance as an effective strategy to eliminate AML LSCs.

OGG1 competitive inhibitors show important off-target effects by directly inhibiting efflux pumps and disturbing mitotic progression

One of the most abundant DNA lesions induced by Reactive oxygen species (ROS) is 8-oxoG, a highly mutagenic lesion that compromises genetic instability when not efficiently repaired. 8-oxoG is specifically recognized by the DNA-glycosylase OGG1 that excises the base and initiates the Base Excision Repair pathway (BER). Furthermore, OGG1 has not only a major role in DNA repair but it is also involved in transcriptional regulation. Cancer cells are particularly exposed to ROS, thus challenging their capacity to process oxidative DNA damage has been proposed as a promising therapeutic strategy for cancer treatment. Two competitive inhibitors of OGG1 (OGG1i) have been identified, TH5487 and SU0268, which bind to the OGG1 catalytic pocket preventing its fixation to the DNA. Early studies with these inhibitors show an enhanced cellular sensitivity to cytotoxic drugs and a reduction in the inflammatory response. Our study uncovers two unreported off-targets effects of these OGG1i that are independent of OGG1. In vitro and in cellulo approaches have unveiled that OGG1i TH5487 and SU0268, despite an unrelated molecular structure, are able to inhibit some members of the ABC family transporters, in particular ABC B1 (MDR1) and ABC G2 (BCRP). The inhibition of these efflux pumps by OGG1 inhibitors results in a higher intra-cellular accumulation of various fluorescent probes and drugs, and largely contributes to the enhanced cytotoxicity observed when the inhibitors are combined with cytotoxic agents. Furthermore, we found that SU0268 has an OGG1-independent anti-mitotic activity-by interfering with metaphase completion-resulting in a high cellular toxicity. These two off-target activities are observed at concentrations of OGG1i that are normally used for in vivo studies. It is thus critical to consider these previously unreported non-specific effects when interpreting studies using TH5487 and SU0268 in the context of OGG1 inhibition. Additionally, our work highlights the persistent need for new specific inhibitors of the enzymatic activity of OGG1.

Mitotic MTH1 Inhibitors in Treatment of Cancer

The DNA damage response (DDR) protein MTH1 is sanitising the oxidized dNTP pool and preventing incorporation of oxidative damage into DNA and has an emerging role in mitosis. It is a stress-induced protein and often found to be overexpressed in cancer. Mitotic MTH1 inhibitors arrest cells in mitosis and result in incorporation of oxidative damage into DNA and selective killing of cancer cells. Here, I discuss the leading mitotic MTH1 inhibitor TH1579 (OXC-101, karonudib), now being evaluated in clinical trials, and describe its dual effect on mitosis and incorporation of oxidative DNA damage in cancer cells. I describe why MTH1 inhibitors that solely inhibits the enzyme activity fail to kill cancer cells and discuss if MTH1 is a valid target for cancer treatment. I discuss emerging roles of MTH1 in regulating tubulin polymerisation and mitosis and the necessity of developing the basic science insights along with translational efforts. I also give a perspective on how edgetic perturbation is making target validation difficult in the DDR field.

Targeting the DNA damage response and repair in cancer through nucleotide metabolism

The exploitation of the DNA damage response and DNA repair proficiency of cancer cells is an important anticancer strategy. The replication and repair of DNA are dependent upon the supply of deoxynucleoside triphosphate (dNTP) building blocks, which are produced and maintained by nucleotide metabolic pathways. Enzymes within these pathways can be promising targets to selectively induce toxic DNA lesions in cancer cells. These same pathways also activate antimetabolites, an important group of chemotherapies that disrupt both nucleotide and DNA metabolism to induce DNA damage in cancer cells. Thus, dNTP metabolic enzymes can also be targeted to refine the use of these chemotherapeutics, many of which remain standard of care in common cancers. In this review article, we will discuss both these approaches exemplified by the enzymes MTH1, MTHFD2 and SAMHD1. © 2022 The Authors. Molecular Oncology published by John Wiley & Sons Ltd on behalf of Federation of European Biochemical Societies.

Inhibition of Oxidized Nucleotide Sanitation By TH1579 and Conventional Chemotherapy Cooperatively Enhance Oxidative DNA Damage and Survival in AML

Currently, the majority of patients with acute myeloid leukemia (AML) still die of their disease due to primary resistance or relapse toward conventional reactive oxygen species (ROS)- and DNA damage-inducing chemotherapy regimens. Herein, we explored the therapeutic potential to enhance chemotherapy response in AML, by targeting the ROS scavenger enzyme MutT homolog 1 (MTH1, NUDT1), which protects cellular integrity through prevention of fatal chemotherapy-induced oxidative DNA damage. We demonstrate that MTH1 is a potential druggable target expressed by the majority of patients with AML and the inv(16)/KITD816Y AML mouse model mimicking the genetics of patients with AML exhibiting poor response to standard chemotherapy (i.e., anthracycline & cytarabine). Strikingly, combinatorial treatment of inv(16)/KITD816Y AML cells with the MTH1 inhibitor TH1579 and ROS- and DNA damage-inducing standard chemotherapy induced growth arrest and incorporated oxidized nucleotides into DNA leading to significantly increased DNA damage. Consistently, TH1579 and chemotherapy synergistically inhibited growth of clonogenic inv(16)/KITD816Y AML cells without substantially inhibiting normal clonogenic bone marrow cells. In addition, combinatorial treatment of inv(16)/KITD816Y AML mice with TH1579 and chemotherapy significantly reduced AML burden and prolonged survival compared with untreated or single treated mice. In conclusion, our study provides a rationale for future clinical studies combining standard AML chemotherapy with TH1579 to boost standard chemotherapy response in patients with AML. Moreover, other cancer entities treated with ROS- and DNA damage-inducing chemo- or radiotherapies might benefit therapeutically from complementary treatment with TH1579.

TH588 and Low-Dose Nocodazole Impair Chromosome Congression by Suppressing Microtubule Turnover within the Mitotic Spindle

Simple Summary

A promising anti-cancer compound TH588 has been recently identified as a microtubule-targeting agent that inhibits tubulin polymerization in vitro and interferes with microtubule dynamics in interphase cells. Although it was shown to arrest cells in mitosis, its effect on microtubule dynamics in dividing cells remained unknown. By analyzing microtubule dynamics in living cells treated with either TH588 or low-dose nocodazole, we revealed that both of these drugs stabilize microtubules within the mitotic spindle, leading to premature formation of kinetochore-microtubule end-on attachments on uncongressed chromosomes. This causes mitotic arrest, ultimately resulting in cell death or cell division with uncongressed chromosomes. Both of these cell fates could contribute to the selective effect associated with the activity of TH588 in cancer cells.

Abstract

Microtubule-targeting agents (MTAs) have been used for decades to treat different hematologic and solid cancers. The mode of action of these drugs mainly relies on their ability to bind tubulin subunits and/or microtubules and interfere with microtubule dynamics. In addition to its MTH1-inhibiting activity, TH588 has been recently identified as an MTA, whose anticancer properties were shown to largely depend on its microtubule-targeting ability. Although TH588 inhibited tubulin polymerization in vitro and reduced microtubule plus-end mobility in interphase cells, its effect on microtubule dynamics within the mitotic spindle of dividing cells remained unknown. Here, we performed an in-depth analysis of the impact of TH588 on spindle-associated microtubules and compared it to the effect of low-dose nocodazole. We show that both treatments reduce microtubule turnover within the mitotic spindle. This microtubule-stabilizing effect leads to premature formation of kinetochore-microtubule end-on attachments on uncongressed chromosomes, which consequently cannot be transported to the cell equator, thereby delaying cell division and leading to cell death or division with uncongressed chromosomes.