Disulfiram, an old drug with new potential therapeutic uses for human hematological malignancies

Unveiling the potential of HKUST-1: synthesis, activation, advantages and biomedical applications

Metal-organic frameworks (MOFs) have emerged as a unique class of nanostructured materials, resulting from the self-assembly of metal ions or clusters with organic ligands, offering a wide range of applications in fields such as drug delivery, gas catalysis, and electrochemical sensing. Among them, HKUST-1, a copper-based MOF, has gained substantial attention due to its remarkable three-dimensional porous structure. Comprising copper ions and benzene-1,3,5-tricarboxylic acid, HKUST-1 exhibits an extraordinary specific surface area and pronounced porosity, making it a promising candidate in biomedicine. Notably, the incorporation of copper ions endows HKUST-1 with noteworthy activities, including antitumor, antibacterial, and wound healing-promoting properties. In this comprehensive review, we delve into the various synthesis methods and activation pathways employed in the preparation of HKUST-1. We also explore the distinct advantages of HKUST-1 in terms of its structural properties and functionalities. Furthermore, we investigate the exciting and rapidly evolving biomedical applications of HKUST-1. From its role in tumor treatment to its antibacterial effects and its ability to promote wound healing, we showcase the multifaceted potential of HKUST-1 in addressing critical challenges in biomedicine.

ALDEFLUOR activity, ALDH isoforms, and their clinical significance in cancers

High aldehyde dehydrogenase (ALDH) activity is a metabolic feature of adult stem cells and various cancer stem cells (CSCs). The ALDEFLUOR system is currently the most commonly used method for evaluating ALDH enzyme activity in viable cells. This system is applied extensively in the isolation of normal stem cells and CSCs from heterogeneous cell populations. For many years, ALDH1A1 has been considered the most important subtype among the 19 ALDH family members in determining ALDEFLUOR activity. However, in recent years, studies of many types of normal and tumour tissues have demonstrated that other ALDH subtypes can also significantly influence ALDEFLUOR activity. In this article, we briefly review the relationships between various members of the ALDH family and ALDEFLUOR activity. The clinical significance of these ALDH isoforms in different cancers and possible directions for future studies are also summarised.

Subcutaneous Rapid Dissolution Microneedle Patch Integrated with CuO2 and Disulfiram for Augmented Antimelanoma Efficacy through Multimodal Synergy of Photothermal Therapy, Chemodynamic Therapy, and Chemotherapy

Melanoma is a malignancy of the skin that is resistant to conventional treatment, necessitating the development of effective and safe new therapies. The percutaneous microneedle (MN) system has garnered increasing interest as a viable treatment option due to its high efficacy, minimal invasiveness, painlessness, and secure benefits. In this investigation, a sensitive MN system with multiple functions was created to combat melanoma effectively. This MN system utilized polyvinylpyrrolidone (PVP) as microneedle substrates and biocompatibility panax notoginseng polysaccharide (PNPS) as microneedle tips, which encapsulated PVP-stabilized CuO2 nanoparticles as a therapeutic agent and disulfiram-containing F127 micelles to enhance the tumor treatment effect. The MN system had sufficient mechanical properties to pierce the skin, and the excellent water solubility of PNPS brought high-speed dissolution properties under the bio conditions, allowing the MNs to effectively penetrate the skin and deliver the CuO2 nanoparticles as well as the drug-loaded micelles to the melanoma site. CuO2 nanoparticles released by the MN system generated Cu2+ and H2O2 in the tumor acidic environment to achieve self-supply of hydrogen peroxide to chemodynamic therapy (CDT). In addition, Cu2+ was chelated with disulfiram to produce CuET, which killed tumor cells. And the MN system had excellent near-infrared (NIR) photothermal properties due to the loading of CuO2 nanoparticles and induced localized thermotherapy in the melanoma region to further inhibit tumor growth. Thus, the designed MN system accomplished effective tumor suppression and minimal side effects in vivo via combined therapy, offering patients a safe and effective option for melanoma treatment.

Co-delivery of a tumor microenvironment-responsive disulfiram prodrug and CuO2 nanoparticles for efficient cancer treatment

Disulfiram (DSF) has been used as a hangover drug for more than seven decades and was found to have potential in cancer treatment, especially mediated by copper. However, the uncoordinated delivery of disulfiram with copper and the instability of disulfiram limit its further applications. Herein, we synthesize a DSF prodrug using a simple strategy that could be activated in a specific tumor microenvironment. Poly amino acids are used as a platform to bind the DSF prodrug through the B-N interaction and encapsulate CuO2 nanoparticles (NPs), obtaining a functional nanoplatform Cu@P-B. In the acidic tumor microenvironment, the loaded CuO2 NPs will produce Cu2+ and cause oxidative stress in cells. At the same time, the increased reactive oxygen species (ROS) will accelerate the release and activation of the DSF prodrug and further chelate the released Cu2+ to produce the noxious copper diethyldithiocarbamate complex, which causes cell apoptosis effectively. Cytotoxicity tests show that the DSF prodrug could effectively kill cancer cells with only a small amount of Cu2+ (0.18 μg mL-1), inhibiting the migration and invasion of tumor cells. In vitro and in vivo experiments have demonstrated that this functional nanoplatform could kill tumor cells effectively with limited toxic side effects, showing a new perspective in DSF prodrug design and cancer treatment.

High-capacity glycol chitosan-based nanoemulsion for efficient delivery of disulfiram

Disulfiram (DS) is an anti-alcoholism drug capable of acting against important and hard-to-treat cancers. The drug's relative instability and variable absorption/distribution have led to its variable pharmacokinetics and suboptimal exposure. Hence, it was hypothesised that a nano-enabled form of DS might be able to overcome such limitations. Encapsulation of the labile DS was achieved with quaternary ammonium palmitoyl glycol chitosan (GCPQ) to form a high-capacity, soybean oil-based DS-GCPQ nanoemulsion. DS-GCPQ showed capability of oil-loading up to 50% v/v for a stable entrapment of high drug content. With increasing oil content (10 to 50% v/v), the mean particle size and polydispersity index were also increased (166 to 351 nm and 0.14 to 0.22, respectively) for a given amount of GCPQ. Formulations showed a highly positive particle surface charge (50.9 ± 1.3 mV), contributing to the colloidal stability of the individual particles. DS-GCPQ showed marked cytotoxicity against pancreatic cancer cell lines with enhanced activity in the presence of copper. An intravenous pharmacokinetic study of DS-GCPQ in vivo showed improved plasma drug stability with a DS half-life of 17 min. Prolonged survival was seen in tumour-bearing animals treated with DS-GCPQ supplemented with copper. In conclusion, DS-GCPQ nanoemulsion has the potential to be developed further for cancer therapeutic purposes.

The Molecular Context of Oxidant Stress Response in Cancer Establishes ALDH1A1 as a Critical Target: What This Means for Acute Myeloid Leukemia

The protein family of aldehyde dehydrogenases (ALDH) encompasses nineteen members. The ALDH1 subfamily consists of enzymes with similar activity, having the capacity to neutralize lipid peroxidation products and to generate retinoic acid; however, only ALDH1A1 emerges as a significant risk factor in acute myeloid leukemia. Not only is the gene ALDH1A1 on average significantly overexpressed in the poor prognosis group at the RNA level, but its protein product, ALDH1A1 protects acute myeloid leukemia cells from lipid peroxidation byproducts. This capacity to protect cells can be ascribed to the stability of the enzyme under conditions of oxidant stress. The capacity to protect cells is evident both in vitro, as well as in mouse xenografts of those cells, shielding cells effectively from a number of potent antineoplastic agents. However, the role of ALDH1A1 in acute myeloid leukemia has been unclear in the past due to evidence that normal cells often have higher aldehyde dehydrogenase activity than leukemic cells. This being true, ALDH1A1 RNA expression is significantly associated with poor prognosis. It is hence imperative that ALDH1A1 is methodically targeted, particularly for the acute myeloid leukemia patients of the poor prognosis risk group that overexpress ALDH1A1 RNA.

In Situ Synthesis of a Tumor-Microenvironment-Responsive Chemotherapy Drug

Current chemotherapy still suffers from unsatisfactory therapeutic efficacy, multi-drug resistance, and severe adverse effects, thus necessitating the development of techniques to confine chemotherapy drugs in the tumor microenvironment. Herein, we fabricated nanospheres of mesoporous silica (MS) doped with Cu (MS-Cu) and polyethylene glycol (PEG)-coated MS-Cu (PEG-MS-Cu) as exogenous copper supply systems to tumors. The synthesized MS-Cu nanospheres showed diameters of 30-150 nm with Cu/Si molar ratios of 0.041-0.069. Only disulfiram (DSF) and only MS-Cu nanospheres showed little cytotoxicity in vitro, whereas the combination of DSF and MS-Cu nanospheres showed significant cytotoxicity against MOC1 and MOC2 cells at concentrations of 0.2-1 μg/mL. Oral DSF administration in combination with MS-Cu nanospheres intratumoral or PEG-MS-Cu nanospheres intravenous administration showed significant antitumor efficacy against MOC2 cells in vivo. In contrast to traditional drug delivery systems, we herein propose a system for the in situ synthesis of chemotherapy drugs by converting nontoxic substances into antitumor chemotherapy drugs in a specific tumor microenvironment.

Disulfiram in glioma: Literature review of drug repurposing

Gliomas are the most common malignant brain tumors. High-grade gliomas, represented by glioblastoma multiforme (GBM), have a poor prognosis and are prone to recurrence. The standard treatment strategy is tumor removal combined with radiotherapy and chemotherapy, such as temozolomide (TMZ). However, even after conventional treatment, they still have a high recurrence rate, resulting in an increasing demand for effective anti-glioma drugs. Drug repurposing is a method of reusing drugs that have already been widely approved for new indication. It has the advantages of reduced research cost, safety, and increased efficiency. Disulfiram (DSF), originally approved for alcohol dependence, has been repurposed for adjuvant chemotherapy in glioma. This article reviews the drug repurposing method and the progress of research on disulfiram reuse for glioma treatment.

Progress in the drug encapsulation of poly(lactic-co-glycolic acid) and folate-decorated poly(ethylene glycol)-poly(lactic-co-glycolic acid) conjugates for selective cancer treatment

Poly(lactic-co-glycolic acid) (PLGA) is a US Food and Drug Administration (FDA)-approved polymer used in humans in the forms of resorbable sutures, drug carriers, and bone regeneration materials. Recently, PLGA-based conjugates have been extensively investigated for cancer, which is the second leading cause of death globally. This article presents an account of the literature on PLGA-based conjugates, focusing on their chemistries, biological activity, and functions as targeted drug carriers or sustained drug controllers for common cancers (e.g., breast, prostate, and lung cancers). The preparation and drug encapsulation of PLGA nanoparticles and folate-decorated poly(ethylene glycol)-poly(lactic-co-glycolic acid) (FA-PEG-PLGA) conjugates are discussed, along with several representative examples. Particularly, the reactions used for preparing drug-conjugated PLGA and FA-PEG-PLGA are emphasized, with the associated chemistries involved in the formation of structures and their biocompatibility with internal organs. This review provides a deeper understanding of the constituents and interactions of PLGA-conjugated materials to ensure successful conjugation in PLGA material design and the subsequent biomedical applications.

A drug repurposing strategy for overcoming human multiple myeloma resistance to standard-of-care treatment

Despite several approved therapeutic modalities, multiple myeloma (MM) remains an incurable blood malignancy and only a small fraction of patients achieves prolonged disease control. The common anti-MM treatment targets proteasome with specific inhibitors (PI). The resulting interference with protein degradation is particularly toxic to MM cells as they typically accumulate large amounts of toxic proteins. However, MM cells often acquire resistance to PIs through aberrant expression or mutations of proteasome subunits such as PSMB5, resulting in disease recurrence and further treatment failure. Here we propose CuET—a proteasome-like inhibitor agent that is spontaneously formed in-vivo and in-vitro from the approved alcohol-abuse drug disulfiram (DSF), as a readily available treatment effective against diverse resistant forms of MM. We show that CuET efficiently kills also resistant MM cells adapted to proliferate under exposure to common anti-myeloma drugs such as bortezomib and carfilzomib used as the first-line therapy, as well as to other experimental drugs targeting protein degradation upstream of the proteasome. Furthermore, CuET can overcome also the adaptation mechanism based on reduced proteasome load, another clinically relevant form of treatment resistance. Data obtained from experimental treatment-resistant cellular models of human MM are further corroborated using rather unique advanced cytotoxicity experiments on myeloma and normal blood cells obtained from fresh patient biopsies including newly diagnosed as well as relapsed and treatment-resistant MM. Overall our findings suggest that disulfiram repurposing particularly if combined with copper supplementation may offer a promising and readily available treatment option for patients suffering from relapsed and/or therapy-resistant multiple myeloma.

Redox-Related Proteins in Melanoma Progression

Melanoma is the most aggressive type of skin cancer. Despite the available therapies, the minimum residual disease is still refractory. Reactive oxygen and nitrogen species (ROS and RNS) play a dual role in melanoma, where redox imbalance is involved from initiation to metastasis and resistance. Redox proteins modulate the disease by controlling ROS/RNS levels in immune response, proliferation, invasion, and relapse. Chemotherapeutics such as BRAF and MEK inhibitors promote oxidative stress, but high ROS/RNS amounts with a robust antioxidant system allow cells to be adaptive and cooperate to non-toxic levels. These proteins could act as biomarkers and possible targets. By understanding the complex mechanisms involved in adaptation and searching for new targets to make cells more susceptible to treatment, the disease might be overcome. Therefore, exploring the role of redox-sensitive proteins and the modulation of redox homeostasis may provide clues to new therapies. This study analyzes information obtained from a public cohort of melanoma patients about the expression of redox-generating and detoxifying proteins in melanoma during the disease stages, genetic alterations, and overall patient survival status. According to our analysis, 66% of the isoforms presented differential expression on melanoma progression: NOS2, SOD1, NOX4, PRX3, PXDN and GPX1 are increased during melanoma progression, while CAT, GPX3, TXNIP, and PRX2 are decreased. Besides, the stage of the disease could influence the result as well. The levels of PRX1, PRX5 and PRX6 can be increased or decreased depending on the stage. We showed that all analyzed isoforms presented some genetic alteration on the gene, most of them (78%) for increased mRNA expression. Interestingly, 34% of all melanoma patients showed genetic alterations on TRX1, most for decreased mRNA expression. Additionally, 15% of the isoforms showed a significant reduction in overall patient survival status for an altered group (PRX3, PRX5, TR2, and GR) and the unaltered group (NOX4). Although no such specific antioxidant therapy is approved for melanoma yet, inhibitors or mimetics of these redox-sensitive proteins have achieved very promising results. We foresee that forthcoming investigations on the modulation of these proteins will bring significant advances for cancer therapy.

Glutathione-responsive copper-disulfiram nanoparticles for enhanced tumor chemotherapy

Disulfiram (DSF), a familiar FDA-approved drug used for alcohol withdrawal, has recently been verified with potent antitumor therapeutic effect by generating Cu(DTC)₂, which is the complex of its metabolite diethyldithiocarbamate (DTC) and copper. However, its poor tumor selectivity and insufficient endogenous Cu²⁺ concentration within tumor site largely hinders the application of DSF-based antitumor therapy. Therefore, a GSH-responsive coordination nanoparticles (Cu-IXZ@DSF) was established as a copper carrier to achieve synchronous but separate delivery of Cu²⁺ and DSF without antitumor ability, further to realize selectively triggered tumor in situ Cu(DTC)₂ generation for antitumor therapy. A widely-used proteasome inhibitor ixazomib (IXZ) was chosen as ligands and Cu²⁺ was used as coordination nodes to form nanosized Cu-IXZ@DSF. The DSF encapsulated in Cu-IXZ@DSF could be reduced to DTC by intracellular GSH, which could contend for Cu²⁺ and realize in situ high toxic Cu(DTC)₂ generation. Meanwhile, the chelation could lead to the disassembly of Cu-IXZ@DSF and release of IXZ to eventually achieve tumor specific "transformation from low toxicity to high toxicity" chemotherapy. The results of in vitro and in vivo experiments demonstrated that the as-prepared nanoplatform Cu-IXZ@DSF showed good biosafety and excellent antitumor effect via endoplasmic reticulum stress (ERS) as well as reactive oxygen species (ROS) generation pathway. Therefore, this nanocarrier provides an inspiring strategy with specific-triggered antitumor Cu(DTC)₂ generation for DSF-based chemotherapy with high therapeutic effect and biosafety and showing great potential of treating cancer.

Exploiting the reactive oxygen species imbalance in high-risk paediatric acute lymphoblastic leukaemia through auranofin

BACKGROUND

The prognosis for high-risk childhood acute leukaemias remains dismal and established treatment protocols often cause long-term side effects in survivors. This study aims to identify more effective and safer therapeutics for these patients.

METHODS

A high-throughput phenotypic screen of a library of 3707 approved drugs and pharmacologically active compounds was performed to identify compounds with selective cytotoxicity against leukaemia cells followed by further preclinical evaluation in patient-derived xenograft models.

RESULTS

Auranofin, an FDA-approved agent for the treatment of rheumatoid arthritis, was identified as exerting selective anti-cancer activity against leukaemia cells, including patient-derived xenograft cells from children with high-risk ALL, versus solid tumour and non-cancerous cells. It induced apoptosis in leukaemia cells by increasing reactive oxygen species (ROS) and potentiated the activity of the chemotherapeutic cytarabine against highly aggressive models of infant MLL-rearranged ALL by enhancing DNA damage accumulation. The enhanced sensitivity of leukaemia cells towards auranofin was associated with lower basal levels of the antioxidant glutathione and higher baseline ROS levels compared to solid tumour cells.

CONCLUSIONS

Our study highlights auranofin as a well-tolerated drug candidate for high-risk paediatric leukaemias that warrants further preclinical investigation for application in high-risk paediatric and adult acute leukaemias.

Possible Therapeutic Potential of Disulfiram for Multiple Myeloma

Multiple myeloma (MM) is a malignant disease of the plasma cells representing approximately 10% of all hemato-oncological diseases. Detection of the disease is most probable at around 65 years of age, and the average survival of patients is estimated to be 5–10 years, specifically due to frequent relapses and resistance to the therapy used. Thus, the search for new therapeutic approaches is becoming a big challenge. Disulfiram (DSF), a substance primarily known as a medication against alcoholism, has often been mentioned in recent years in relation to cancer treatment for its secondary anti-cancer effects. Recent studies performed on myeloma cell lines confirm high inhibition of the cell growth activity if a complex of disulfiram and copper is used. Its significant potential is now being seen in the cure of haematological malignities.

Transitional Metal-Based Noncatalytic Medicine for Tumor Therapy

Nanocatalytic medicine has been emerging as a highly promising strategy for cancer therapeutics since it enables tumor suppression by in situ generating toxic agents within tumors through catalytic reactions without using conventional highly toxic and nonselective chemodrugs. In the last several years, a number of nanocatalytic medicines have been used to steer catalytic reactions in endogenous or exogenous stimuli-activated cancer therapy, such as chemodynamic therapy, photodynamic therapy, and sonodynamic therapy. In particular, transitional metal-based nanocatalytic medicines with excellent catalytic activity and selectivity show significant clinical potentials, and significant progress has been achieved very recently. In this review, three types of typical transitional metal (Fe, Mn, and Cu)-based nanocatalytic medicines are summarized, followed by detailed discussions on their catalytic mechanisms. Of note, the obstacles and challenges that will be encountered in the design and further clinical conversion of transitional metal-based nanocatalytic medicine in the future are also outlooked.

Differential Cytotoxicity Mechanisms of Copper Complexed with Disulfiram in Oral Cancer Cells

Disulfiram (DSF), an irreversible aldehyde dehydrogenase inhibitor, is being used in anticancer therapy, as its effects in humans are known and less adverse than conventional chemotherapy. We explored the potential mechanism behind the cytotoxicity of DSF-Cu⁺/Cu²⁺ complexes in oral epidermoid carcinoma meng-1 (OECM-1) and human gingival epithelial Smulow-Glickman (SG) cells. Exposure to CuCl₂ or CuCl slightly but concentration-dependently decreased cell viability, while DSF-Cu⁺/Cu²⁺ induced cell death in OECM-1 cells, but not SG cells. DSF-Cu⁺/Cu²⁺ also increased the subG1 population and decreased the G1, S, and G2/M populations in OECM-1 cells, but not SG cells, and suppressed cell proliferation in both OECM-1 and SG cells. ALDH enzyme activity was inhibited by CuCl and DSF-Cu⁺/Cu²⁺ in SG cells, but not OECM-1 cells. ROS levels and cellular senescence were increased in DSF-Cu⁺/Cu²⁺-treated OECM-1 cells, whereas they were suppressed in SG cells. DSF-Cu⁺/Cu²⁺ induced mitochondrial fission in OECM-1 cells and reduced mitochondrial membrane potential. CuCl₂ increased but DSF- Cu²⁺ impaired oxygen consumption rates and extracellular acidification rates in OECM-1 cells. CuCl₂ stabilized HIF-1α expression under normoxia in OECM-1 cells, and complex with DSF enhanced that effect. Levels of c-Myc protein and its phosphorylation at Tyr58 and Ser62 were increased, while levels of the N-terminal truncated form (Myc-nick) were decreased in DSF-Cu⁺/Cu²-treated OECM-1 cells. These effects were all suppressed by pretreatment with the ROS scavenger NAC. Overexpression of c-Myc failed to induce HIF-1α expression. These findings provide novel insight into the potential application of DSF-CuCl₂ complex as a repurposed agent for OSCC cancer therapy.

The disulfiram/copper complex induces apoptosis and inhibits tumor growth in human osteosarcoma by activating the ROS/JNK signaling pathway

Given the huge cost, long research and development (R&D) time and uncertain side effects of discovering new drugs, drug repositioning of those approved to treat diseases clinically as new drugs for other pathological conditions, especially cancers, is a potential alternative strategy. Disulfiram (DSF), an old drug used to treat alcoholism, has been found to exhibit anticancer activity and improve chemotherapeutic efficacy in cancers by an increasing number of studies. In addition, the combination of DSF and copper may be a more effective therapeutic strategy. In this study, we report the toxicity of the DSF/Cu complex to human osteosarcoma both in vitro and in vivo. DSF/Cu significantly inhibited the proliferation and clonogenicity of osteosarcoma cell lines. Furthermore, the generation of ROS was triggered by DSF/Cu, and cell arrest, autophagy and apoptosis were induced in a ROS-dependent manner. The underlying mechanism of this process was explored, and DSF/Cu may mainly inhibit osteosarcoma by inducing apoptosis by activating the ROS/JNK pathway. DSF/Cu also inhibited osteosarcoma growth in a xenograft model with low levels of organ-related toxicities. These results suggest that the DSF/Cu complex could be an efficient and safe option for the treatment of osteosarcoma in the clinic.

Co-treatment with disulfiram and glycyrrhizic acid suppresses the inflammatory response of chondrocytes

Background

Osteoarthritis (OA) is a kind of systemic musculoskeletal disorder and a most important factor for causing disability and physical painfulness. Nevertheless, due to the fact that OA can be triggered by multiple etiological factors, this disease is hard to be cured. Therefore, it is of great necessity for us to find novel targets or drugs for OA treatment.

Materials and methods

The chondrocytes were treated with lipopolysaccharide (LPS) and adenosine triphosphate (ATP) to induce pyroptosis in OA. The cell proliferation was detected by Cell Counting Kit-8 assay (CCK-8 assay). Enzyme-linked immunosorbent assay (ELISA) was used for the detection of pyroptosis-related inflammatory factors. Then, the antagonists for gasdermin D (GSDMD) (disulfiram) and high mobility group box 1 (HMGB1) (glycyrrhizic acid) were used to treat the cell model to observe the effects of disulfiram and glycyrrhizic acid on the proliferation of chondrocytes in OA. The protein levels of pyroptosis-related inflammatory factors were measured by western blot, and the levels of aldehyde dehydrogenase (ALDH) and reactive oxygen species (ROS) were measured by corresponding commercial kits.

Results

After chondrocytes were induced by LPS and ATP, the cell proliferation was decreased and the expressions of pyroptosis-related inflammatory factors were increased. Disulfiram and glycyrrhizic acid treatment led to enhanced cell proliferation and increased expressions of pyroptosis-related inflammatory factors, while disulfiram showed better alleviative effects on the inflammation in chondrocytes in OA. However, co-treatment with disulfiram at a high concentration and glycyrrhizic acid did not result in higher proliferation of chondrocytes and alleviated inflammation, but led to oxidative stress.

Conclusion

In conclusion, co-treatment with disulfiram and glycyrrhizic acid at a standard concentration suppresses the inflammatory response of chondrocytes, which may provide guidance for the use of the drugs in the treatment of OA.

Disulfiram: a novel repurposed drug for cancer therapy

Cancer is a major health issue worldwide and the global burden of cancer is expected to reduce the costs of treatment as well as prolong the survival time. One of the promising approaches is drug repurposing, because it reduces costs and shortens the production cycle of research and development. Disulfiram (DSF), which was originally approved as an anti-alcoholism drug, has been proven safe and shows the potential to target tumours. Its anti-tumour effect has been reported in many preclinical studies and recently on seven types of cancer in humans: non-small cell lung cancer (NSCLC), liver cancer, breast cancer, prostate cancer, pancreatic cancer, glioblastoma (GBM) and melanoma and has a successful breakthrough in the treatment of NSCLC and GBM. The mechanisms, particularly the intracellular signalling pathways, still remain to be completely elucidated. As shown in our previous study, DSF inhibits NF-kB signalling, proteasome activity, and aldehyde dehydrogenase (ALDH) activity. It induces endoplasmic reticulum (ER) stress and autophagy and has been used as an adjuvant therapy with irradiation or chemotherapy drugs. On the other hand, DSF not only kills the normal cancer cells but also has the ability to target cancer stem cells, which provides a new approach to prevent tumour recurrence and metastasis. Furthermore, other researchers have reported the ability of DSF to bind to nuclear protein localization protein 4 (NPL4), induce its immobilization and dysfunction, ultimately leading to cell death. Here, we provide an overview of DSF repurposing as a treatment in preclinical studies and clinical trials, and review studies describing the mechanisms underlying its anti-neoplastic effects.

Diethyldithiocarbamate-copper nanocomplex reinforces disulfiram chemotherapeutic efficacy through light-triggered nuclear targeting

To circumvent the huge cost, long R&D time and the difficulty to identify the targets of new drugs, repurposing the ones that have been clinically approved has been considered as a viable strategy to treat different diseases. In the current study, we outlined the rationale for repurposing disulfiram (DSF, an old alcohol-aversion drug) to treat primary breast cancer and its metastases.

Methods: To overcome a few shortcomings of the individual administration of DSF, such as the dependence on copper ions (Cu²⁺) and limited capability in selective targeting, we here artificially synthesized the active form of DSF, diethyldithiocarbamate (DTC)-Cu complex (CuET) for cancer therapeutics. To achieve a greater efficacy in vivo, smart nanomedicines were devised through a one-step self-assembly of three functional components including a chemically stable and biocompatible phase-change material (PCM), the robust anticancer drug (CuET) and a near-infrared (NIR) dye (DIR), namely CuET/DIR NPs. A number of in vitro assays were performed including the photothermal efficacy, light-triggered drug release behavior, nuclear localization, DNA damage and induction of apoptosis of CuET/DIR NPs and molecular mechanisms underlying CuET-induced repression on cancer metastatic behaviors. Meanwhile, the mice bearing 4T1-LG12-drived orthotopic tumors were employed to evaluate in vivo biodistribution and anti-tumor effect of CuET/DIR NPs. The intravenous injection model was employed to reflect the changes of the intrinsic metastatic propensity of 4T1-LG12 cells responding to CuET/DIR NPs.

Results: The rationally designed nanomedicines have self-traceability for bioimaging, long blood circulation time for enhanced drug accumulation in the tumor site and photo-responsive release of the anticancer drugs. Moreover, our data unearthed that CuET/DIR nanomedicines behave like “Trojan horse” to transport CuET into the cytoplasm, realizing substantial intracellular accumulation. Upon NIR laser irradiation, massive CuET would be triggered to release from the nanomedicines and reach a high local concentration towards the nucleus, where the pro-apoptotic effects were conducted. Importantly, our CuET/DIR nanomedicines revealed a pronounced capability to leash breast cancer metastases through inhibition on EMT. Additionally, these nanomedicines showed great biocompatibility in animals.

Conclusion: These combined data unearthed a remarkably enhanced tumor-killing efficacy of our CuET nanomedicines through nuclear targeting. This work may open a new research area of repurposing DSF as innovative therapeutic agents to treat breast cancer and its metastases.

Disulfiram-gold-nanorod integrate for effective tumor targeting and photothermal-chemical synergistic therapy

Herein, we successfully constructed a combination therapeutic nanoplatform with high tumor targeting for cancer treatment by integrating gold nanorods with disulfiram (denoted Au-DSF). The Au-DSF integrates possess a uniform length (70 nm), excellent photothermal conversion ability and a high DSF loading content (23.2%), and the loaded DSFs show glutathione-, acid-, and laser-responsive release properties. The Au-DSF integrates show significantly enhanced cellular uptake efficiency in breast cancer cells due to the ability of DSF to chelate to the intracellular copper (Cu) which is present at high concentrations. Furthermore, the Au-DSF exhibits improved circulation time (mean residence time = 28.4 h) and increased tumor accumulation (12.0%), due to the targeting of DSF to the abundant Cu ions at the tumor site. Moreover, the DSF/Cu complexes potently elevate reactive oxygen species, which effectively induce cancer cell apoptosis. In vivo experiments show that the Au-DSF integrates dramatically decrease tumor size via photothermal therapy and chemotherapy. Hematoxylin-eosin and TUNEL staining show that the Au-DSF integrates induce necrosis and apoptosis in cancer cells. The high therapeutic efficiency of the Au-DSF integrates for breast cancer is further demonstrated by the reduced elasticity seen in ultrasound elastography, and the absence of perfusion of the contrast agent in contrast-enhanced ultrasound imaging in tumors.

Copper-Enriched Prussian Blue Nanomedicine for In Situ Disulfiram Toxification and Photothermal Antitumor Amplification

In situ toxification of less toxic substance for the generation of effective anticarcinogens at the specific tumor tissue has been a novel paradigm for combating cancer. Significant efforts have been recently dedicated to turning clinical-approved drugs into anticancer agents in specific tumor microenvironment by chemical reactions. Herein, a hollow mesoporous Prussian blue (HMPB)-based therapeutic nanoplatform, denoted as DSF@PVP/Cu-HMPB, is constructed by encapsulating alcohol-abuse drug disulfiram (DSF) into the copper-enriched and polyvinylpyrrolidone (PVP)-decorated HMPB nanoparticles to achieve in situ chemical reaction-activated and hyperthermia-amplified chemotherapy of DSF. Upon tumor accumulation of DSF@PVP/Cu-HMPB, the endogenous mild acidity in tumor condition triggers the biodegradation of the HMPB nanoparticle and the concurrent co-releases of DSF and Cu²⁺ , thus forming cytotoxic bis(N,N-diethyl dithiocarbamato)copper(II) complexes (CuL₂ ) via DSF-Cu²⁺ chelating reaction. Moreover, by the intrinsic photothermal-conversion effect of PVP/Cu-HMPBs, the anticancer effect of DSF is augmented by the hyperthermia generated upon near-infrared irradiation, thus inducing remarkable cell apoptosis in vitro and tumor elimination in vivo on both subcutaneous and orthotopic tumor-bearing models. This strategy of in situ drug transition by chemical chelation reaction and photothermal-augmentation provides a promising paradigm for designing novel cancer-therapeutic nanoplatforms.

Disulfiram/cytarabine eradicates a subset of acute myeloid leukemia stem cells with high aldehyde dehydrogenase expression

Most patients with acute myeloid leukemia (AML) achieve complete remission (CR) after induction chemotherapy, however, in some patients, the disease subsequently relapses and may lead to death. Leukemia stem cells (LSC) have been identified as the main cause for recurrence. Increased aldehyde dehydrogenase (ALDHhigh) activity in a variety of cancer stem cells prevents effective action of chemotherapeutic drugs. In this study, we found that approximately 50.7% of AML patients had ALDHhigh, and the presence of ALDHhigh stem cells was associated with poor cytogenetic prognosis. Lentiviral vector transduced ALDHhigh leukemia cell lines are insensitive to the conventional chemotherapy drug cytarabine, and inhibition of ALDH activity by disulfiram (DSF) can increase the sensitivity of ALDHhigh leukemia cells to cytarabine. Unlike traditional chemotherapy drugs, DSF is not toxic to healthy umbilical cord blood stem cells. An ALDHhigh leukemia cell xenograft model was established using immunodeficient mice to mimic the disease environment, and DSF and cytarabine were found to eliminate the ALDHhigh leukemia cells in transplanted mice while not affecting the healthy blood cells of mice. These findings suggest that DSF may have therapeutic potential by inhibiting ALDH activity and thereby increasing chemosensitivity.

N-Oxide polymer-cupric ion nanogels potentiate disulfiram for cancer therapy

Disulfiram (DSF) exerts potent anticancer activity via the formation of chelates with copper or zinc ions in tumor tissues, but the low abundance of these ions in the tumor cannot sustain its antitumor activity. Herein, we show that a zwitterionic water-soluble N-oxide polymer, poly[2-(N-oxide-N,N-dimethylamino)ethyl methacrylate] (OPDMA), can complex cupric ions and form nanogels (OPDMA/Cu), which efficiently deliver copper ions to tumor tissue to potentiate DSF significantly for effective antitumor therapy.

Disulfiram/copper markedly induced myeloma cell apoptosis through activation of JNK and intrinsic and extrinsic apoptosis pathways

Disulfiram (DSF) is an FDA approved anti-alcoholism drug in use for more than 60 years. Recently, antitumor activity of the DSF/copper (DSF/Cu) complex has been identified. Its anti-multiple myeloma activity, however, has barely been investigated. In the present study, our results demonstrated that the DSF/Cu complex induced apoptosis of MM cells and MM primary cells. The results indicated that DSF/Cu significantly induced cell cycle arrest at the G2/M phase in MM.1S and RPMI8226 cells. Moreover, JC-1 and Western blot results showed that DSF/Cu disrupted mitochondrial membrane integrity and cleaved caspase-8 in MM cells, respectively, suggesting that it induced activation of extrinsic and intrinsic apoptosis pathways. Interestingly, DSF/Cu induced caspase-3 activation was partly blocked by Z-VAD-FMK (zVAD), a pan-caspase inhibitor, indicating at caspase-dependent and -independent paths involved in DSF/Cu induced myeloma cell apoptosis machinery. Additionally, activation of the c-Jun N-terminal kinase (JNK) signaling pathway was observed in DSF/Cu treated MM cells. More importantly, our results demonstrated that DSF/Cu significantly reduced tumor volumes and prolonged overall survival of MM bearing mice when compared with the controls. Taken together, our novel findings showed that DSF/Cu has potent anti-myeloma activity in vitro and in vivo highlighting valuable clinical potential of DSF/Cu in MM treatment.

Approaches to Targeting Cancer Stem Cells in Solid Tumors

CSCs are a population of self-renewing and tumor repopulating cells that have been observed in hematologic and solid tumors and their presence contributes to the development of drug resistance. The failure to eliminate CSCs with conventional therapy is one of major obstacles in the successful treatment of cancer. Several mechanisms have been described to contribute to CSCs chemoresistance properties that include the adoption of drug-efflux pumps, drug detoxification pathways, changes in metabolism, improved DNA repair mechanisms, and deregulated survival and pro-apoptotic pathways. Thus, CSCs are therefore an attractive target to develop new anti-cancer therapies.

Natural Sesquiterpene Lactones Enhance Chemosensitivity of Tumor Cells through Redox Regulation of STAT3 Signaling

STAT3 is a nuclear transcription factor that regulates genes involved in cell cycle, cell survival, and immune response. Although STAT3 activation drives cells to physiological response, its deregulation is often associated with the development and progression of many solid and hematological tumors as well as with drug resistance. STAT3 is a redox-sensitive protein, and its activation state is related to intracellular GSH levels. Under oxidative conditions, STAT3 activity is regulated by S-glutathionylation, a reversible posttranslational modification of cysteine residues. Compounds able to suppress STAT3 activation and, on the other hand, to modulate intracellular redox homeostasis may potentially improve cancer treatment outcome. Nowadays, about 35% of commercial drugs are natural compounds that derive from plant extracts used in phytotherapy and traditional medicine. Sesquiterpene lactones are an interesting chemical group of plant-derived compounds often employed in traditional medicine against inflammation and cancer. This review focuses on sesquiterpene lactones able to downmodulate STAT3 signaling leading to an antitumor effect and correlates the anti-STAT3 activity with their ability to decrease GSH levels in cancer cells. These properties make them lead compounds for the development of a new therapeutic strategy for cancer treatment.

Proteomic profiling identifies outcome-predictive markers in patients with peripheral T-cell lymphoma, not otherwise specified

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) constitutes a heterogeneous category of lymphomas, which do not fit into any of the specifically defined T-cell lymphoma entities. Both the pathogenesis and tumor biology in PTCL-NOS are poorly understood. Protein expression in pretherapeutic PTCL-NOS tumors was analyzed by proteomics. Differentially expressed proteins were compared in 3 distinct scenarios: (A) PTCL-NOS tumor tissue (n = 18) vs benign lymphoid tissue (n = 8), (B) clusters defined by principal component analysis (PCA), and (C) tumors from patients with chemosensitive vs refractory PTCL-NOS. Selected differentially expressed proteins identified by proteomics were correlated with clinico-pathological features and outcome in a larger cohort of patients with PTCL-NOS (n = 87) by immunohistochemistry (IHC). Most proteins with altered expression were identified comparing PTCL-NOS vs benign lymphoid tissue. PCA of the protein profile defined 3 distinct clusters. All benign samples clustered together, whereas PTCL-NOS tumors separated into 2 clusters with different patient overall survival rates (P = .001). Differentially expressed proteins reflected large biological diversity among PTCL-NOS, particularly associated with alterations of "immunological" pathways. The 2 PTCL-NOS subclusters defined by PCA showed disturbance of "stress-related" and "protein metabolic" pathways. α-Enolase 1 (ENO1) was found differentially expressed in all 3 analyses, and high intratumoral ENO1 expression evaluated by IHC correlated with poor outcome (hazard ratio, 2.09; 95% confidence interval, 1.17-3.73; P = .013). High expression of triosephosphate isomerase (TPI1) also showed a tendency to correlate with poor survival (P = .057). In conclusion, proteomic profiling of PTCL-NOS provided evidence of markedly altered protein expression and identified ENO1 as a novel potential prognostic marker.

ALDH2 Repression Promotes Lung Tumor Progression via Accumulated Acetaldehyde and DNA Damage

The major role of aldehyde dehydrogenase 2 family (ALDH2) is to detoxify acetaldehyde (ACE) to non-toxic acetic acid. Many evidences suggest that ALDH2 dysfunction contributes to a variety of human diseases including cancer. However, the biological function and molecular mechanism of ALDH2 in tumor progression remain elusive. In this study, we found that ALDH2 repression was associated with poor prognosis in lung adenocarcinoma. Overexpression of ALDH2 inhibited malignant features of lung adenocarcinoma cells, such as proliferation, stemness and migration, whereas ALDH2 knockdown increased these features. Mechanistically, ALDH2 repression led to accumulation of ACE; whereas ACE enhanced the migration features of lung adenocarcinoma cells, which was associated with increased DNA damage. Importantly, accumulated ACE and increased DNA damage were identified in Aldh2-knockout (KO) mouse lung tissues in vivo. Consistent with this concept, treatment of lung adenocarcinoma cells with ALDH2 agonist Alda-1 suppressed the proliferation, stemness and migration features of lung adenocarcinoma cells. Thus, activating ALDH2, such as via its agonist, may provide a novel strategy for treatment of lung cancer.

Reading Cancer: Chromatin Readers as Druggable Targets for Cancer Treatment

The epigenetic machinery deputed to control histone post-translational modifications is frequently dysregulated in cancer cells. With epigenetics being naturally reversible, it represents a good target for therapies directed to restore normal gene expression. Since the discovery of Bromodomain and Extra Terminal (BET) inhibitors, a great effort has been spent investigating the effects of chromatin readers’ inhibition, specifically the class of proteins assigned to bind acetylated and methylated residues. So far, focused studies have been produced on epigenetic regulation, dissecting a specific class of epigenetic-related proteins or investigating epigenetic therapy in a specific tumor type. In this review, recent steps toward drug discovery on the different classes of chromatin readers have been outlined, highlighting the pros and cons of current therapeutic approaches.

Hydroxycobalamin catalyzes the oxidation of diethyldithiocarbamate and increases its cytotoxicity independently of copper ions

It is known that some metals (Cu, Zn, Cd, Au) markedly increase the toxic effect of thiocarbamates. It was shown in the present study that hydroxycobalamin (a form of vitamin B12, HOCbl), which incorporates cobalt, significantly enhances the cytotoxicity of diethyldithiocarbamate (DDC), decreasing its IC50 value in tumor cells three to five times. The addition of HOCbl to aqueous DDC solutions accelerated the reduction of oxygen. No hydrogen peroxide accumulation was observed in DDC + HOCbl solutions; however, catalase slowed down the oxygen reduction rate. Catalase as well as the antioxidants N-acetylcysteine (NAC) and glutathione (GSH) partially inhibited the cytotoxic effect of DDC + HOCbl, whereas ascorbate, pyruvate, and tiron, a scavenger of superoxide anion, had no cytoprotective effect. The administration of HOCbl into DDC solutions (> 1 mM) resulted in the formation of a crystalline precipitate, which was inhibited in the presence of GSH. The data of UV and NMR spectroscopy and HPLC and Mass Spectrometry (LC/MS) indicated that the main products of the reaction of DDC with HOCbl are disulfiram (DSF) and its oxidized forms, sulfones and sulfoxides. The increase in the cytotoxicity of DDC combined with HOCbl occurred both in the presence of Cu2+ in culture medium and in nominally Cu-free solutions, as well as in growth medium containing the copper chelator bathocuproine disulfonate (BCS). The results indicate that HOCbl accelerates the oxidation of DDC with the formation of DSF and its oxidized forms. Presumably, the main cause of the synergistic increase in the toxic effect of DDC + HOCbl is the formation of sulfones and sulfoxides of DSF.

Leveraging γ-Glutamyl Transferase To Direct Cytotoxicity of Copper Dithiocarbamates against Prostate Cancer Cells

A prodrug approach is presented to direct copper-dependent cytotoxicity to prostate cancer cells. The prochelator GGTDTC requires activation by γ-glutamyl transferase (GGT) to release the metal chelator diethyldithiocarbamate from a linker that masks its thiol reactivity and metal binding properties. In vitro studies demonstrated successful masking of copper binding as well as clean liberation of the chelator by GGT. GGTDTC was stable to non-specific degradation when incubated with a series of prostate cancer and normal cell lines, with selective release of diethyldithiocarbamate only occurring in cells with measurable GGT activity. The antiproliferative efficacy of the prochelator correlated with cellular GGT activity, with 24 h inhibitory concentrations ranging from 800 nm in prostate cancer lines 22Rv1 and LNCaP to over 15 μm in normal prostate PWR-1E cells. These findings underscore a new strategy to leverage the amplified copper metabolism of prostate cancer by conditional activation of a metal-binding pharmacophore.

Glutathione metabolism in cancer progression and treatment resistance

Bansal and Simon discuss strategies to block glutathione synthesis and utilization pathways to inhibit tumor propagation and treatment resistance.

Glutathione (GSH) is the most abundant antioxidant found in living organisms and has multiple functions, most of which maintain cellular redox homeostasis. GSH preserves sufficient levels of cysteine and detoxifies xenobiotics while also conferring therapeutic resistance to cancer cells. However, GSH metabolism plays both beneficial and pathogenic roles in a variety of malignancies. It is crucial to the removal and detoxification of carcinogens, and alterations in this pathway can have a profound effect on cell survival. Excess GSH promotes tumor progression, where elevated levels correlate with increased metastasis. In this review, we discuss recent studies that focus on deciphering the role of GSH in tumor initiation and progression as well as mechanisms underlying how GSH imparts treatment resistance to growing cancers. Targeting GSH synthesis/utilization therefore represents a potential means of rendering tumor cells more susceptible to different treatment options such as chemotherapy and radiotherapy.

Disulfiram/copper targets stem cell-like ALDH+ population of multiple myeloma by inhibition of ALDH1A1 and Hedgehog pathway

Multiple myeloma stem cells (MMSCs) have been considered as the major cause resulting in relapse. Eradicating MMSCs may be an effective strategy to improve the outcome of multiple myeloma (MM). Increased activity of aldehyde dehydrogenase (ALDH) has been found in MMSCs, but whether inhibiting ALDH activity can eliminate MMSCs remains unknown. Disulfiram (DS) has been reported as an inhibitor of ALDH, and increasing studies showed it has anti-cancer effects in a copper (Cu)-dependent manner. In this study, we isolated ALDH⁺ cells of MM by Aldefluor assay and demonstrated they possessed tumorigenesis capacities in vitro and in vivo. Next, we investigated the effects of DS with or without Cu on suppressing the stemness of MM both in vitro and in vivo. We found that DS/Cu eliminated the stem cell-like ALDH⁺ cells. Furthermore, we demonstrated that DS/Cu inhibited the expression of stem cell transcription factors NANOG and OCT4, and abolished the clonogenicity of MM. We also showed that DS/Cu reduced the tumor growth and inhibited stemness of MM in xenograft model. We further found the specific target of DS/Cu is ALDH1A1 and DS/Cu inhibited the Hedgehog (Hh) pathway transcription factors Gli1 and Gli2 regulated by ALDH1A1 at least in part. Our data suggest that DS/Cu can inhibit the ALDH⁺ stem cell-like cells through ALDH1A1 and Hh pathway, which may be a promising therapeutic agent in eradicating stem cell-like cells of MM.

Recent Advances in Antabuse (Disulfiram): The Importance of its Metal-binding Ability to its Anticancer Activity

BACKGROUND

Considerable evidence demonstrates the importance of dithiocarbamates especially disulfiram as anticancer drugs. However there are no systematic reviews outlining how their metal-binding ability is related to their anticancer activity. This review aims to summarize chemical features and metal-binding activity of disulfiram and its metabolite DEDTC, and discuss different mechanisms of action of disulfiram and their contributions to the drug's anticancer activity.

METHODS

We undertook a disulfiram-related search on bibliographic databases of peerreviewed research literature, including many historic papers and in vitro, in vivo, preclinical and clinical studies. The selected papers were carefully reviewed and summarized.

RESULTS

More than five hundreds of papers were obtained in the initial search and one hundred eighteen (118) papers were included in the review, most of which deal with chemical and biological aspects of Disulfiram and the relationship of its chemical and biological properties. Eighty one (81) papers outline biological aspects of dithiocarbamates, and fifty seven (57) papers report biological activity of Disulfiram as an inhibitor of proteasomes or inhibitor of aldehyde dehydrogenase enzymes, interaction with other anticancer drugs, or mechanism of action related to reactive oxygen species. Other papers reviewed focus on chemical aspects of dithiocarbamates.

CONCLUSION

This review confirms the importance of chemical features of compounds such as Disulfiram to their biological activities, and supports repurposing DSF as a potential anticancer agent.

Effective elimination of adult B-lineage acute lymphoblastic leukemia by disulfiram/copper complex in vitro and in vivo in patient-derived xenograft models

Disulfiram (DS), a clinically used drug to control alcoholism, has displayed promising anti-cancer activity against a wide range of tumors. Here, we demonstrated that DS/copper (Cu) complex effectively eliminated adult B-ALL cells in vitro and in vivo in patient-derived xenograft (PDX) humanized mouse models, reflected by inhibition of cell proliferation, induction of apoptosis, suppression of colony formation, and reduction of PDX tumor growth, while sparing normal peripheral blood mononuclear cells. Mechanistically, these events were associated with disruption of mitochondrial membrane potential and down-regulation of the anti-apoptotic proteins Bcl-2 and Bcl-xL. Further analysis on B-ALL patients' clinical characteristics revealed that the ex vivo efficacy of DS/Cu in primary samples was significantly correlated to p16 gene deletion and peripheral blood WBC counts at diagnosis, while age, LDH level, extramedullary infiltration, status post intensive induction therapy, immune phenotype, risk category, and Ph chromosome had no effect. Together, these findings indicate that disulfiram, particularly when administrated in combination with copper, might represent a potential repurposing agent for treatment of adult B-ALL patients, including those clinically characterized by one or more adverse prognostic factors.

Update of ALDH as a Potential Biomarker and Therapeutic Target for AML

Studies employing mouse transplantation have illustrated the role of aldehyde dehydrogenase (ALDH) defining hematopoietic stem cells (HSCs) and leukemia stem cells (LSCs). Besides being a molecular marker, ALDH mediates drug resistance in AML, which induces poor prognosis of the patients. In AML patients, either CD34⁺ALDH^br population or CD34⁺CD38^-ALDH^int population was found to denote LSCs and minimal residual disease (MRD). A bunch of reagents targeting ALDH directly or indirectly have been evaluated. ATRA, disulfiram, and dimethyl ampal thiolester (DIMATE) are all shown to be potential candidates to open new perspective for AML treatment. However, inconsistent results have been shown for markers of LSCs, which makes it even more difficult to differentiate LSCs and HSCs. In this review, we elevated the role of ALDH to be a potential marker to define and distinguish HSCs and LSCs and its importance in prognosis and target therapy in AML patients. In addition to immunophenotypical markers, ALDH is also functionally active in defining and distinguishing HSCs and LSCs and offers intracellular protections against cytotoxic drugs. Targeting ALDH may be a potential strategy to improve AML treatment. Additional studies concerning specific targeting ALDH and mechanisms of its roles in LSCs are warranted.

Disulfiram is a slow-binding partial noncompetitive inhibitor of 20S proteasome activity

The alcohol abuse drug disulfiram has also been shown to exhibit potent cell growth inhibitory and anticancer activity. While a number of cellular and animal studies have suggested that disulfiram exhibits its anticancer activity through interaction with the proteasome, direct evidence for inhibition of proteasome activity is lacking. In this study we show that disulfiram potently inhibits the chymotrypsin-like activity of purified human 20S proteasome at low micromolar pharmacological concentrations. The enzyme progress curves displayed characteristics of a slow-binding reaction, similar to that observed for the FDA-approved proteasomal-targeted anticancer drugs bortezomib and carfilzomib. The apparent second order rate constant for reaction with 20s proteasome that was derived from an analysis of the progress curves was about 250-fold smaller than for bortezomib and carfilzomib. The concentration dependence of the enzyme kinetics was consistent with partial noncompetitive inhibition, whereby the putative disulfiram-proteasome adduct retains, partial but decreased enzyme activity. Disulfiram, which is known to have a high affinity for protein thiols, likely reacted with a non-critical cysteine residue, and not at the proteasome substrate binding site.

Disulfiram/copper selectively eradicates AML leukemia stem cells in vitro and in vivo by simultaneous induction of ROS-JNK and inhibition of NF-κB and Nrf2

Acute myeloid leukemia (AML) is a heterogeneous malignancy. Despite the advances in past decades, the clinical outcomes of AML patients remain poor. Leukemia stem cells (LSCs) is the major cause of the recurrence of AML even after aggressive treatment making, promoting development of LSC-targeted agents is an urgent clinical need. Although the antitumor activity of disulfiram (DS), an approved anti-alcoholism drug, has been demonstrated in multiple types of tumors including hematological malignancies such as AML, it remains unknown whether this agent would also be able to target cancer stem cells like LSCs. Here, we report the in vitro and in vivo activity of DS in combination with copper (Cu) against CD34⁺/CD38⁺ leukemia stem-like cells sorted from KG1α and Kasumi-1 AML cell lines, as well as primary CD34⁺ AML samples. DS plus Cu (DS/Cu) displayed marked inhibition of proliferation, induction of apoptosis, and suppression of colony formation in cultured AML cells while sparing the normal counterparts. DS/Cu also significantly inhibited the growth of human CD34⁺/CD38⁺ leukemic cell-derived xenografts in NOD/SCID mice. Mechanistically, DS/Cu-induced cytotoxicity was closely associated with activation of the stress-related ROS-JNK pathway as well as simultaneous inactivation of the pro-survival Nrf2 and nuclear factor-κB pathways. In summary, our findings indicate that DS/Cu selectively targets leukemia stem-like cells both in vitro and in vivo, thus suggesting a promising LSC-targeted activity of this repurposed agent for treatment of relapsed and refractory AML.

Disulfiram overcomes bortezomib and cytarabine resistance in Down-syndrome-associated acute myeloid leukemia cells

Background

Children with Down syndrome (DS) have increased risk for developing AML (DS-AMKL), and they usually experience severe therapy-related toxicities compared to non DS-AMKL. Refractory/relapsed disease has very poor outcome, and patients would benefit from novel, less toxic, therapeutic strategies that overcome resistance. Relapse/resistance are linked to cancer stem cells with high aldehyde dehydrogenase (ALDH) activity. The purpose of the present work was to study less toxic alternative therapeutic agents for relapsed/refractory DS-AMKL.

Methods

Fourteen AML cell lines including the DS-AMKL CMY and CMK from relapsed/refractory AML were used. Cytarabine (Ara-C), bortezomib (BTZ), disulfiram/copper (DSF/Cu²⁺) were evaluated for cytotoxicity, depletion of ALDH-positive cells, and resistance. BTZ-resistant CMY and CMK variants were generated by continuous BTZ treatment. Cell viability was assessed using CellTiter-Glo®, ALDH activity by ALDELUOR^TM, and proteasome inhibition by western blot of ubiquitinated proteins and the Proteasome-Glo™ Chymotrypsin-Like (CT-like) assay, apoptosis by Annexin V Fluos/Propidium iodide staining, and mutations were detected using PCR, cloning and sequencing.

Results

Ara-C-resistant AML cell lines were sensitive to BTZ and DSF/Cu²⁺. The Ara-C-resistant DS-AMKL CMY cells had a high percentage of ALDH^bright “stem-like” populations that may underlie Ara-C resistance. One percent of these cells were still resistant to BTZ but sensitive to DSF/Cu²⁺. To understand the mechanism of BTZ resistance, BTZ resistant (CMY-BR) and (CMK-BR) were generated. A novel mutation PSMB5 Q62P underlied BTZ resistance, and was associated with an overexpression of the β5 proteasome subunit. BTZ-resistance conferred increased resistance to Ara-C due to G1 arrest in the CMY-BR cells, which protected the cells from S-phase damage by Ara-C. CMY-BR and CMK-BR cells were cross-resistant to CFZ and MG-132 but sensitive to DSF/Cu²⁺. In this setting, DSF/Cu²⁺ induced apoptosis and proteasome inhibition independent of CT-like activity inhibition.

Conclusions

We provide evidence that DSF/Cu²⁺ overcomes Ara-C and BTZ resistance in cell lines from DS-AMKL patients. A novel mutation underlying BTZ resistance was detected that may identify BTZ-resistant patients, who may not benefit from treatment with CFZ or Ara-C, but may be responsive to DSF/Cu²⁺. Our findings support the clinical development of DSF/Cu²⁺ as a less toxic efficacious treatment approach in patients with relapsed/refractory DS-AMKL.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0493-5) contains supplementary material, which is available to authorized users.

Combining disulfiram and poly(l-glutamic acid)-cisplatin conjugates for combating cisplatin resistance

A poly(l-glutamic acid) graft polyethylene glycol-cisplatin complex (PGA-CisPt) performs well in reducing the toxicity of free cisplatin and greatly enhances the accumulation and retention of cisplatin in solid tumors. However, there is a lack of effective treatment options for cisplatin-resistant tumors. A major reason for this is the dense PEG shell, which ensures that the PGA-CisPt maintains a long retention time in the blood that may result in it bypassing the tumor cells or failing to be endocytosed within the tumor microenvironment. Consequently, the cisplatin from PGA-CisPt is released to the extracellular space in the presence of cisplatin-resistant tumor cells and the resistant problem to free cisplatin still valid. Therefore, we devised a strategy to combat the resistance of cisplatin in the tumor microenvironment using nanoparticles-loaded disulfiram (NPs-DSF) as a modulator. In vitro, cisplatin, in combination with DSF, had a synergistic effect and decreased cell survival rate of cisplatin-resistant A549DDP cells. This effect was also observed when combining PGA-CisPt with NPs-DSF. Similarly, in Balb/C nude mice with A549DDP xenografts, NPs-DSF improved PGA-CisPt effectiveness in inhibiting tumor growth while maintaining low toxicity. Our data demonstrate that DSF reduces intracellular glutathione (GSH) levels, inhibits NFκB activity, and modulates the expression of apoptosis-related proteins Bcl-2 and Bax, thereby improves the effectiveness of cisplatin in resistant cell lines. Here, we provide a promising method for overcoming cisplatin resistance in tumors, while maintaining the in vivo benefits of the PGA-CisPt complex.

Delivery of disulfiram into breast cancer cells using folate-receptor-targeted PLGA-PEG nanoparticles: in vitro and in vivo investigations

Background

A folate-receptor-targeted poly (lactide-co-Glycolide) (PLGA)-Polyethylene glycol (PEG) nanoparticle is developed for encapsulation and delivery of disulfiram into breast cancer cells. After a comprehensive characterization of nanoparticles, cell cytotoxicity, apoptosis induction, cellular uptake and intracellular level of reactive oxygen species are analyzed. In vivo acute and chronic toxicity of nanoparticles and their efficacy on inhibition of breast cancer tumor growth is studied.

Results

The folate-receptor-targeted nanoparticles are internalized into the cells, induce reactive oxygen species formation, induce apoptosis and inhibit cell proliferation more efficiently compared to the untargeted nanoparticles. The acute and toxicity test show the maximum dose of disulfiram equivalent of nanoparticles for intra-venous injection is 6 mg/kg while show significant decrease in the breast cancer tumor growth rate.

Conclusion

It is believed that the developed formulation could be used as a potential vehicle for successful delivery of disulfiram, an old and inexpensive drug, into breast cancer cells and other solid tumors.Graphical abstract

Disulfiram when Combined with Copper Enhances the Therapeutic Effects of Temozolomide for the Treatment of Glioblastoma

PURPOSE

Glioblastoma is one of the most lethal cancers in humans, and with existing therapy, survival remains at 14.6 months. Current barriers to successful treatment include their infiltrative behavior, extensive tumor heterogeneity, and the presence of a stem-like population of cells, termed brain tumor-initiating cells (BTIC) that confer resistance to conventional therapies.

EXPERIMENTAL DESIGN

To develop therapeutic strategies that target BTICs, we focused on a repurposing approach that explored already-marketed (clinically approved) drugs for therapeutic potential against patient-derived BTICs that encompass the genetic and phenotypic heterogeneity of glioblastoma observed clinically.

RESULTS

Using a high-throughput in vitro drug screen, we found that montelukast, clioquinol, and disulfiram (DSF) were cytotoxic against a large panel of patient-derived BTICs. Of these compounds, disulfiram, an off-patent drug previously used to treat alcoholism, in the presence of a copper supplement, showed low nanomolar efficacy in BTICs including those resistant to temozolomide and the highly infiltrative quiescent stem-like population. Low dose DSF-Cu significantly augmented temozolomide activity in vitro, and importantly, prolonged in vivo survival in patient-derived BTIC models established from both newly diagnosed and recurrent tumors. Moreover, we found that in addition to acting as a potent proteasome inhibitor, DSF-Cu functionally impairs DNA repair pathways and enhances the effects of DNA alkylating agents and radiation. These observations suggest that DSF-Cu inhibits proteasome activity and augments the therapeutic effects of DNA-damaging agents (temozolomide and radiation).

CONCLUSIONS

DSF-Cu should be considered as an adjuvant therapy for the treatment of patients with glioblastoma in both newly diagnosed and recurrent settings. Clin Cancer Res; 22(15); 3860-75. ©2016 AACR.