D-penicillamine and other low molecular weight thiols: review of anticancer effects and related mechanisms

Cuproptosis in cancers: Function and implications from bench to bedside

Copper, an indispensable micronutrient, is implicated in numerous vital biological processes and is essential for all physiological activities. Recently, the discovery of a novel type of copper-dependent cell death, known as cuproptosis, has shed light on its role in cancer development. Extensive research is currently underway to unravel the mechanisms underlying cuproptosis and its correlation with various cancer types. In this review, we summarize the findings regarding the roles and mechanisms of cuproptosis in various cancer types, including colorectal cancer, lung cancer, gastric cancer, breast cancer, liver cancer and cutaneous melanoma. Furthermore, the effects of copper-related agents such as copper chelators and copper ionophores on cell proliferation, apoptosis, angiogenesis, tumor immunity, and chemotherapy resistance have been explored in cancer preclinical and clinical trials. These insights provide promising avenues for the development of prospective anticancer drugs aimed at inducing cuproptosis.

Constructing "smart" chelators by using an activatable prochelator strategy for the treatment of Wilson's disease

Wilson's disease (WD) is a genetic disorder that primarily leads to the pathological accumulation of copper (Cu) in the liver, causing an abnormal increase in reactive oxygen species (ROS). The prevailing clinical therapy for WD involves lifelong use of Cu chelation drugs to facilitate Cu excretion in patients. However, most available drugs exert severely side-effects due to their non-specific excretion of Cu, unsuitable for long-term use. In this study, we construct a prochelator that enables precise and controlled delivery of Cu chelator drugs to the liver in WD model, circumventing toxic side effects on other organs and normal tissues. This innovative prochelator rapidly releases the chelator and the fluorescent molecule methylene blue (MB) upon activation by ROS highly expressed in the liver of WD. The released chelator coordinates with Cu, efficiently aiding in Cu removal from the body and effectively inhibiting the pathological progression of WD.

Phenanthroline and Schiff Base associated Cu(II)-coordinated compounds containing N, O as donor atoms for potent anticancer activity

As an inherent metal ion, copper has been the subject of investigation for developing a novel antitumoral compound that exhibits fewer adverse effects. Copper serves as a cofactor in multiple enzymes, generates reactive oxygen species (ROS), facilitates tumour evolution, metastasis and angiogenesis and has been detected at elevated concentrations in the serum and tissues of various human cancer types. In the given setting, utilising two methodologies in developing novel Copper-based pharmaceuticals for anti-cancer applications is standard practice. These approaches involve either the sequestration of unbound Copper ions or the synthesis of Copper complexes that induce cellular apoptosis. In the past four decades, the latter system has been used, leading to numerous reviews that have examined the anticancer characteristics of a wide range of Copper complexes. These analyses have consistently demonstrated that multiple factors frequently influence the efficacy of these compounds. This review examines the possible anticancer properties of copper and Cu(II) complexes that incorporate Schiff base ligands containing 1,10-phenanthroline. The present study will comprehensively analyse the examined cell lines and mechanistic research associated with each complex.

Cuproptosis: A novel therapeutic target for overcoming cancer drug resistance

Cuproptosis is a newly identified form of cell death driven by copper. Recently, the role of copper and copper triggered cell death in the pathogenesis of cancers have attracted attentions. Cuproptosis has garnered enormous interest in cancer research communities because of its great potential for cancer therapy. Copper-based treatment exerts an inhibiting role in tumor growth and may open the door for the treatment of chemotherapy-insensitive tumors. In this review, we provide a critical analysis on copper homeostasis and the role of copper dysregulation in the development and progression of cancers. Then the core molecular mechanisms of cuproptosis and its role in cancer is discussed, followed by summarizing the current understanding of copper-based agents (copper chelators, copper ionophores, and copper complexes-based dynamic therapy) for cancer treatment. Additionally, we summarize the emerging data on copper complexes-based agents and copper ionophores to subdue tumor chemotherapy resistance in different types of cancers. We also review the small-molecule compounds and nanoparticles (NPs) that may kill cancer cells by inducing cuproptosis, which will shed new light on the development of anticancer drugs through inducing cuproptosis in the future. Finally, the important concepts and pressing questions of cuproptosis in future research that should be focused on were discussed. This review article suggests that targeting cuproptosis could be a novel antitumor therapy and treatment strategy to overcome cancer drug resistance.

A Peptoid-Chelator Selective to Cu2+ That Can Extract Copper from Metallothionein-2 and Lead to the Production of ROS

Copper is an essential metal ion that is involved in critical cellular processes, but which can also exhibit toxic effects through its ability to catalyze reactive oxygen species (ROS) formation. Dysregulation of copper homeostasis has been implicated in the progression of several diseases, including cancer. A novel therapeutic approach, extensively studied in recent years, is to capitalize on the increased copper uptake and dependency exhibited by cancer cells and to promote copper-associated ROS production within the tumor microenvironment, leading to the apoptosis of cancer cells. Such an effect can be achieved by selectively chelating copper from copper-bearing metalloproteins in cancer cells, thereby forming a copper-chelator complex that produces ROS and, through this, induces oxidative stress and initiates apoptosis. Herein, we describe a peptoid chelator, TB, that is highly suitable to carry this task. Peptoids are N-substituted glycine oligomers that can be efficiently synthesized on a solid support and are also biocompatible; thus, they are considered promising drug candidates. We show, by rigorous spectroscopic techniques, that TB is not only selective for Cu(II) ions, but can also effectively extract copper from metallothionein-2, and the formed complex CuTB can promote ROS production. Our findings present a promising first example for the future development of peptoid-based chelators for applications in anti-cancer chelation therapy, highlighting the potential for the prospect of peptoid chelators as therapeutics.

WR1065 conjugated to thiol-PEG polymers as novel anticancer prodrugs: broad spectrum efficacy, synergism, and drug resistance reversal

The lack of anticancer agents that overcome innate/acquired drug resistance is the single biggest barrier to achieving a durable complete response to cancer therapy. To address this issue, a new drug family was developed for intracellular delivery of the bioactive aminothiol WR1065 by conjugating it to discrete thiol-PEG polymers: 4-star-PEG-S-S-WR1065 (4SP65) delivers four WR1065s/molecule and m-PEG6-S-S-WR1065 (1LP65) delivers one. Infrequently, WR1065 has exhibited anticancer effects when delivered via the FDA-approved cytoprotectant amifostine, which provides one WR1065/molecule extracellularly. The relative anticancer effectiveness of 4SP65, 1LP65, and amifostine was evaluated in a panel of 15 human cancer cell lines derived from seven tissues. Additional experiments assessed the capacity of 4SP65 co-treatments to potentiate the anticancer effectiveness and overcome drug resistance to cisplatin, a chemotherapeutic, or gefitinib, a tyrosine kinase inhibitor (TKI) targeting oncogenic EGFR mutations. The CyQUANT®-NF proliferation assay was used to assess cell viability after 48-h drug treatments, with the National Cancer Institute COMPARE methodology employed to characterize dose-response metrics. In normal human epithelial cells, 4SP65 or 1LP65 enhanced or inhibited cell growth but was not cytotoxic. In cancer cell lines, 4SP65 and 1LP65 induced dose-dependent cytostasis and cytolysis achieving 99% cell death at drug concentrations of 11.2 ± 1.2 µM and 126 ± 15.8 µM, respectively. Amifostine had limited cytostatic effects in 11/14 cancer cell lines and no cytolytic effects. Binary pairs of 4SP65 plus cisplatin or gefitinib increased the efficacy of each partner drug and surmounted resistance to cytolysis by cisplatin and gefitinib in relevant cancer cell lines. 4SP65 and 1LP65 were significantly more effective against TP53-mutant than TP53-wild-type cell lines, consistent with WR1065-mediated reactivation of mutant p53. Thus, 4SP65 and 1LP65 represent a unique prodrug family for innovative applications as broad-spectrum anticancer agents that target p53 and synergize with a chemotherapeutic and an EGFR-TKI to prevent or overcome drug resistance.

Water-soluble copper pyrithione complexes with cytotoxic and antibacterial activity

Copper Pyrithione, [Cu(PyS)₂] has shown excellent biological activity against cancer cells and bacterial cells, however, it has extremely low aqueous solubility, limiting its applicability. Herein, we report a series of PEG-substituted pyrithione copper(II) complexes with significantly increased aqueous solubility. While long PEG chains lead to a decrease in bioactivity, the addition of short PEG chains leads to improved aqueous solubility with retention of activity. One novel complex, [Cu(PyS1)₂], has particularly impressive anticancer activity, surpassing that of the parent complex.

A Cerium Organic Framework with {Cu2I2} Cluster and {Cu2I2}n Chain Modules: Structure and Fluorescence Sensing Properties

In this work, a copper iodine module bearing a coordination polymer (CP) with a formula of [(Cu₂I₂)₂Ce₂(INA)₆(DMF)₃]·DMF (1, HINA = isonicotinic acid, DMF = N,N'-dimethyl formamide) is presented. The title compound features a three dimensional (3D) structure, in which the {Cu₂I₂} cluster and {Cu₂I₂}_n chain modules are coordinated by N atoms from a pyridine ring in INA^- ligands, while the Ce³⁺ ions are bridged by the carboxylic groups of INA^- ligands. More importantly, compound 1 exhibits an uncommon red fluorescence (FL) with a single emission band maximized at 650 nm belonging to near infrared (NIR) luminescence. The temperature dependent FL measurement was applied to investigate the FL mechanism. Remarkably, 1 could be used as a FL sensor to cysteine and the nitro-bearing explosive molecule of trinitropheno (TNP) with high sensitivity, demonstrating its potential FL sensing applications for biothiol and explosive molecules.

The huge potential of targeting copper status in the treatment of colorectal cancer

Colorectal cancer (CRC) commonly leads to cancer deaths and is often diagnosed at advanced stages. It also faces difficulties due to the poor results of conventional treatments such as surgery, chemotherapy, and radiotherapy. Copper is a mineral nutrient whose intrinsic properties have a two-way effect on the production and treatment of cancer. Copper's redox properties allow it to be used in developing anti-cancer drugs, while its potential toxicity leads to oxidative stress and even cancer. Copper status is closely related to colorectal tumors' proliferation and metastasis. The study of the mechanisms of copper homeostasis, cuproplasia, and cuproptosis due to altered copper status plays a crucial role in developing anticancer drugs. Therefore, targeting alteration of copper status becomes a potential option for treating colorectal cancer. This review summarizes the mechanisms by which altered copper status causes CRC progression and emphasizes the potential of regulating copper status in treating CRC.

Regulatory roles of copper metabolism and cuproptosis in human cancers

Copper is an essential micronutrient for human body and plays a vital role in various biological processes including cellular respiration and free radical detoxification. Generally, copper metabolism in the body is in a stable state, and there are specific mechanisms to regulate copper metabolism and maintain copper homeostasis. Dysregulation of copper metabolism may have a great connection with various types of diseases, such as Wilson disease causing copper overload and Menkes disease causing copper deficiency. Cancer presents high mortality rates in the world due to the unlimited proliferation potential, apoptosis escape and immune escape properties to induce organ failure. Copper is thought to have a great connection with cancer, such as elevated levels in cancer tissue and serum. Copper also affects tumor progression by affecting angiogenesis, metastasis and other processes. Notably, cuproptosis is a novel form of cell death that may provide novel targeting strategies for developing cancer therapy. Copper chelators and copper ionophores are two copper coordinating compounds for the treatment of cancer. This review will explore the relationship between copper metabolism and cancers, and clarify copper metabolism and cuproptosis for cancer targeted therapy.

Inspecting the structural characteristics of chiral drug penicillamine under different pH conditions using Raman optical activity spectroscopy and DFT calculations

The investigation of the structural characteristics of chiral drugs in physiological environments is a challenging research topic, which may lead to a better understanding of how the drugs work. Raman optical activity (ROA) spectroscopy in combination with density functional theory (DFT) calculations was exploited to inspect the structural changes in penicillamine under different acid-base states in aqueous solutions. The B3LYP/aug-cc-PVDZ method was employed and the implicit solvation model density (SMD) was considered for describing the solvation effect in H₂O. The conformations of penicillamine varied with pH, but penicillamine was liable to stabilize in the form of the P_C conformation (the sulfur atom is in a trans orientation with respect to carboxylate) in most cases for both D- and L-isomers. The relationship between the conformations of penicillamine and the ROA peaks, as well as peak assignments, were comprehensively studied and elucidated. In the fingerprint region, two ROA couplets and one ROA triplet with different patterns were recognized. The intensity, sign and frequency of the corresponding peaks also changed with varying pH. Deuteration was carried out to identify the vibrational modes, and the ROA peaks of the deuterated amino group in particular are sensitive to change in the ambient environment. The results are expected not only to serve as a reference for the interpretation of the ROA spectra of penicillamine and other chiral drugs with analogous structures but also to evaluate the structural changes of chiral molecules in physiological environments, which will form the basis of further exploration of the effects of structural characteristics on the pharmacological and toxicological properties of chiral drugs.

Disulfiram Chelated with Copper Promotes Apoptosis in Osteosarcoma via ROS/Mitochondria Pathway

Disulfiram (DSF) chelated with copper has been confirmed to have a strong anti-tumor ability. In this study, we determined that DSF-Cu induced mitochondria-dependent apoptosis in osteosarcoma (OS), reflecting in DSF-Cu induces mitochondrial membrane potential decline, the production of reactive oxygen species (ROS), and inhibiting cells migration and invasion along with decreasing the concentration of intracellular glutathione (GSH) and facilitating the opening of mitochondrial permeability transition pore (PT) in osteosarcoma cells. These anti-tumor activities can be reversed by Cyclosporine A (CsA, PT inhibitors) and N-acetyl-L-cysteine (NAC, antioxidants). Our results suggested that DSF-Cu exerts its anti-tumor effects in OS via regulation of the ROS/Mitochondria pathway. Our findings provide the basis for DSF-Cu to treat osteosarcoma, even might develop as a potential therapy for other tumors.

Recent Advances in Repurposing Disulfiram and Disulfiram Derivatives as Copper-Dependent Anticancer Agents

Copper (Cu) plays a pivotal role in cancer progression by acting as a co-factor that regulates the activity of many enzymes and structural proteins in cancer cells. Therefore, Cu-based complexes have been investigated as novel anticancer metallodrugs and are considered as a complementary strategy for currently used platinum agents with undesirable general toxicity. Due to the high failure rate and increased cost of new drugs, there is a global drive towards the repositioning of known drugs for cancer treatment in recent years. Disulfiram (DSF) is a first-line antialcoholism drug used in clinics for more than 65 yr. In combination with Cu, it has shown great potential as an anticancer drug by targeting a wide range of cancers. The reaction between DSF and Cu ions forms a copper diethyldithiocarbamate complex (Cu(DDC)₂ also known as CuET) which is the active, potent anticancer ingredient through inhibition of NF-κB and ubiquitin-proteasome system as well as alteration of the intracellular reactive oxygen species (ROS). Importantly, DSF/Cu inhibits several molecular targets related to drug resistance, stemness, angiogenesis and metastasis and is thus considered as a novel strategy for overcoming tumour recurrence and relapse in patients. Despite its excellent anticancer efficacy, DSF has proven unsuccessful in several cancer clinical trials. This is likely due to the poor stability, rapid metabolism and/or short plasma half-life of the currently used oral version of DSF and the inability to form Cu(DDC)₂ at relevant concentrations in tumour tissues. Here, we summarize the scientific rationale, molecular targets, and mechanisms of action of DSF/Cu in cancer cells and the outcomes of oral DSF ± Cu in cancer clinical trials. We will focus on the novel insights on harnessing the immune system and hypoxic microenvironment using DSF/Cu complex and discuss the emerging delivery strategies that can overcome the shortcomings of DSF-based anticancer therapies and provide opportunities for translation of DSF/Cu or its Cu(DDC)₂ complex into cancer therapeutics.

D-Penicillamine: The State of the Art in Humans and in Dogs from a Pharmacological and Regulatory Perspective

Chelant agents are the mainstay of treatment in copper-associated hepatitis in humans, where D-penicillamine is the chelant agent of first choice. In veterinary medicine, the use of D-penicillamine has increased with the recent recognition of copper-associated hepatopathies that occur in several breeds of dogs. Although the different regulatory authorities in the world (United States Food and Drugs Administration-U.S. FDA, European Medicines Agency-EMEA, etc.) do not approve D-penicillamine for use in dogs, it has been used to treat copper-associated hepatitis in dogs since the 1970s, and is prescribed legally by veterinarians as an extra-label drug to treat this disease and alleviate suffering. The present study aims to: (a) address the pharmacological features; (b) outline the clinical scenario underlying the increased interest in D-penicillamine by overviewing the evolution of its main therapeutic goals in humans and dogs; and finally, (c) provide a discussion on its use and prescription in veterinary medicine from a regulatory perspective.

Roles of Ion Fluxes, Metabolism, and Redox Balance in Cancer Therapy

Recent Advances: The 2019 Nobel Prize awarded to the mechanisms for oxygen sensing and adaptation according to oxygen availability, highlighting the fundamental importance of gaseous molecules. Gaseous molecules, including reactive oxygen species (ROS), can interact with different cations generated during metabolic and redox dysregulation in cancer cells. Cross talk between calcium signaling and metabolic/redox pathways leads to network-based dyregulation in cancer. Significance: Recent discovery on using small molecules targeting the ion channels, redox signaling, and protein modification on metabolic enzymes can effectively inhibit cancer growth. Several FDA-approved drugs and clinical trials are ongoing to target the calcium channels, such as TRPV6 and TRPM8. Multiple small molecules from natural products target metablic and redox enzymes to exert an anticancer effect. Critical Issues: Small molecules targeting key ion channels, metabolic enzymes that control key aspects of metabolism, and redox proteins are promising, but their action mechanisms of the target are needed to be elucidated with advanced-omic technologies, which can give network-based and highly dimensioal data. In addition, small molecules that can directly modify the protein residues have emerged as a novel anticancer strategy. Future Directions: Advanced technology accelerates the detection of ions and metabolic and redox changes in clinical samples for diagnosis and informs the decision of cancer treatment. The improvement of ROS detection, ROS target identification, and computational-aid drug discovery also improves clincal outcome.Overall, network-based or holistic regulations of cancer via ion therapy and metabolic and redox intervention are promising as new anticancer strategies. Antioxid. Redox Signal. 34, 1108-1127.

Small molecules regulating reactive oxygen species homeostasis for cancer therapy

Elevated intracellular reactive oxygen species (ROS) and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. Compared with normal cells, cancer cells exhibit increased ROS to maintain their malignant phenotypes and are more dependent on the "redox adaptation" mechanism. Thus, there are two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to prevent or treat cancer. The first strategy, that is, chemoprevention, is to prevent or reduce intracellular ROS either by suppressing ROS production pathways or by employing antioxidants to enhance ROS clearance, which protects normal cells from malignant transformation and inhibits the early stage of tumorigenesis. The second strategy is the ROS-mediated anticancer therapy, which stimulates intracellular ROS to a toxicity threshold to activate ROS-induced cell death pathways. Therefore, targeting the regulation of intracellular ROS-related pathways by small-molecule candidates is considered to be a promising treatment for tumors. We herein first briefly introduce the source and regulation of ROS, and then focus on small molecules that regulate ROS-related pathways and show efficacy in cancer therapy from the perspective of pharmacophores. Finally, we discuss several challenges in developing cancer therapeutic agents based on ROS regulation and propose the direction of future development.

D-Penicillamine prolongs survival and lessens copper-induced toxicity in Drosophila melanogaster

D-penicillamine (DPA) is an amino-thiol that has been established as a copper chelating agent for the treatment of Wilson's disease. DPA reacts with metals to form complexes and/or chelates. Here, we investigated the survival rate extension capacity and modulatory role of DPA on Cu²⁺-induced toxicity in Drosophila melanogaster. Adult Wild type (Harwich strain) flies were exposed to Cu²⁺ (1 mM) and/or DPA (50 μM) in the diet for 7 days. Additionally, flies were exposed to acute Cu²⁺ (10 mM) for 24 h, followed by DPA (50 μM) treatment for 4 days. Thereafter, the antioxidant status [total thiol (T-SH) and glutathione (GSH) levels and glutathione S-transferase and catalase activities] as well as hydrogen peroxide (H₂O₂) level and acetylcholinesterase activity were evaluated. The results showed that DPA treatment prolongs the survival rate of D. melanogaster by protecting against Cu²⁺-induced lethality. Further, DPA restored Cu²⁺-induced depletion of T-SH level compared to the control (P < 0.05). DPA also protected against Cu²⁺ (1 mM)-induced inhibition of catalase activity. In addition, DPA ameliorated Cu²⁺-induced elevation of acetylcholinesterase activity in the flies. The study may therefore have health implications in neurodegenerative diseases involving oxidative stress such as Alzheimer's disease.

Copper homeostasis: Emerging target for cancer treatment

Copper (Cu) is an essential micronutrient involved in a variety of fundamental biological processes. Recently, disorder of Cu homeostasis can be observed in many malignancies. Elevated Cu levels in serum and tissue are correlated with cancer progression. Hence, targeting Cu has emerged as a novel strategy in cancer treatment. This review provides an overview of physiological Cu metabolism and its homeostasis, followed by a discussion of the dysregulation of Cu homeostasis in cancer and the effects of Cu on cancer progression. Finally, recent therapeutic advances using Cu coordination complexes as anticancer agents, as well as the mechanisms of their anti-cancer action are discussed. This review contributes full comprehension to the role of Cu in cancer and demonstrates the broad application prospect of Cu coordination compounds as potential therapeutic agents.

The combination of disulfiram and copper for cancer treatment

Disulfiram (DSF) is a thiuram derivative that was developed to treat alcoholism but was also found to have antitumor activity. Copper (Cu), as a trace metal, has important roles in the body. Numerous studies have shown that the combination of DSF and copper (DSF/Cu) greatly enhances its antitumor efficacy. Given that the efficacy of DSF is well established and its safety profile is understood, repurposing DSF as a new anticancer drug is a promising strategy. Here, we summarize the pharmacological effects of DSF and the role of Cu in cancer, and focus on the antitumor effect of DSF/Cu, especially the mechanisms involved in enhancing drug sensibility by targeting specific molecules. We also provide rational strategies for using DSF as a cancer therapy.

Transition metal chelators, pro-chelators, and ionophores as small molecule cancer chemotherapeutic agents

Transition metal chelators and ionophores have shown promise as alternative chemotherapeutic strategies by selectively altering the concentrations of iron, copper, and zinc in cancer cells.

Inhibiting eukaryotic ribosome biogenesis

BACKGROUND

Ribosome biogenesis is a central process in every growing cell. In eukaryotes, it requires more than 250 non-ribosomal assembly factors, most of which are essential. Despite this large repertoire of potential targets, only very few chemical inhibitors of ribosome biogenesis are known so far. Such inhibitors are valuable tools to study this highly dynamic process and elucidate mechanistic details of individual maturation steps. Moreover, ribosome biogenesis is of particular importance for fast proliferating cells, suggesting its inhibition could be a valid strategy for treatment of tumors or infections.

RESULTS

We systematically screened ~ 1000 substances for inhibitory effects on ribosome biogenesis using a microscopy-based screen scoring ribosomal subunit export defects. We identified 128 compounds inhibiting maturation of either the small or the large ribosomal subunit or both. Northern blot analysis demonstrates that these inhibitors cause a broad spectrum of different rRNA processing defects.

CONCLUSIONS

Our findings show that the individual inhibitors affect a wide range of different maturation steps within the ribosome biogenesis pathway. Our results provide for the first time a comprehensive set of inhibitors to study ribosome biogenesis by chemical inhibition of individual maturation steps and establish the process as promising druggable pathway for chemical intervention.

Redox Control of Angiogenesis

SIGNIFICANCE

Angiogenesis is the formation of new vessels that sprout from existing vessels. This process is highly complex and requires a coordinated shift of the endothelial phenotype from a quiescent cell in the vessel wall into a migrating or proliferating cell. Such change in the life of the endothelial cell is induced by a variety of factors such as hypoxia, metabolic changes, or cytokines. Recent Advances: Within the last years, it became clear that the cellular redox state and oxidation of signaling molecules or phosphatases are critical modulators in angiogenesis.

CRITICAL ISSUES

According to the wide variety of stimuli that induce angiogenesis, a complex signaling network is needed to support a coordinated response of the endothelial cell. Reactive oxygen species (ROS) now are second messengers that either directly oxidize a target molecule or initiate a cascade of redox sensitive steps that transmit the signal. Further Directions: For the understanding of redox signaling, it is essential to recognize and accept that ROS do not represent master regulators of angiogenetic processes. They rather modulate existing signal cascades. This review summarizes some current findings on redox signaling in angiogenesis.

Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy

A very promising direction in the development of anticancer drugs is inhibiting the molecular pathways that keep cancer cells alive and able to metastasize. Copper and iron are two essential metals that play significant roles in the rapid proliferation of cancer cells and several chelators have been studied to suppress the bioavailability of these metals in the cells. This review discusses the major contributions that Cu and Fe play in the progression and spreading of cancer and evaluates select Cu and Fe chelators that demonstrate great promise as anticancer drugs. Efforts to improve the cellular delivery, efficacy, and tumor responsiveness of these chelators are also presented including a transmetallation strategy for dual targeting of Cu and Fe. To elucidate the effectiveness and specificity of Cu and Fe chelators for treating cancer, analytical tools are described for measuring Cu and Fe levels and for tracking the metals in cells, tissue, and the body.

Iron and Copper Intracellular Chelation as an Anticancer Drug Strategy

A very promising direction in the development of anticancer drugs is inhibiting the molecular pathways that keep cancer cells alive and able to metastasize. Copper and iron are two essential metals that play significant roles in the rapid proliferation of cancer cells and several chelators have been studied to suppress the bioavailability of these metals in the cells. This review discusses the major contributions that Cu and Fe play in the progression and spreading of cancer and evaluates select Cu and Fe chelators that demonstrate great promise as anticancer drugs. Efforts to improve the cellular delivery, efficacy, and tumor responsiveness of these chelators are also presented including a transmetallation strategy for dual targeting of Cu and Fe. To elucidate the effectiveness and specificity of Cu and Fe chelators for treating cancer, analytical tools are described for measuring Cu and Fe levels and for tracking the metals in cells, tissue, and the body.

Oxidative/nitrative stress in the pathogenesis of systemic sclerosis: are antioxidants beneficial?

Systemic sclerosis (SSc) is a multisystem autoimmune disease: characterised from the clinical side by progressive vasculopathy and fibrosis of the skin and different organs and from the biochemical side by fibroblast deregulation with excessive production of collagen and increased expression of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). The latter contributes to an overproduction of reactive oxygen species that through an autocrine loop maintains NOX4 in a state of activation. Reactive oxygen and nitrogen species are implicated in the origin and perpetuation of several clinical manifestations of SSc having vascular damage in common; attempts to dampen oxidative and nitrative stress through different agents with antioxidant properties have not translated into a sustained clinical benefit. Objective of this narrative review is to describe the origin and clinical implications of oxidative and nitrative stress in SSc, with particular focus on the central role of NOX4 and its interactions, to re-evaluate the antioxidant approaches so far used to limit disease progression, to appraise the complexity of antioxidant treatment and to touch on novel pathways elements of which may represent specific treatment targets in the not so distant future.

Combination Therapy with Low Copper Diet, Penicillamine and Gamma Knife Radiosurgery Reduces VEGF and IL-8 In Patients with Recurrent Glioblastoma

Purpose:

Vascular Endothelial Growth Factor (VEGF) and interleukin-8 (IL-8) appear important in tumor growth. In this study, we have investigated the effect of copper reduction along with gamma knife radiosurgery on IL-8 and VEGF in patients with recurrent glioblastoma multiforme (GBM).

Materials and Methods:

In a 3-month randomized clinical trial, patients with recurrent GBM were allocated randomly between intervention and placebo groups. Radiosurgery was performed for both groups (Reference dose: 16-18 Gray, in one fraction). The intervention group received low copper diet and penicillamine while the patients in the placebo group continued with their usual diet. VEGF and IL-8 were measured at baseline and the end of intervention.

Results:

VEGF in intervention group significantly reduced compared to placebo group (Mean ± SD, 4.5±1.91 vs. 7.8±3.21; P<0.001). IL-8 in intervention group decreased compared to placebo group but not significant (2.7±1.91 vs. 3.2±3.20; P=0.49). We also detected a significant positive correlation between serum copper and VEGF (r=0.57; P<0.05) and a negative correlation between KPS and serum copper.

Discussion:

Our results could reflect that low copper diet and penicillamine may decrease serum VEGF in patients who underwent gamma knife radiosurgery for recurrent glioblastoma multiforme.

Documenting and harnessing the biological potential of molecules in Distributed Drug Discovery (D3) virtual catalogs

Virtual molecular catalogs have limited utility if member compounds are (i) difficult to synthesize or (ii) unlikely to have biological activity. The Distributed Drug Discovery (D3) program addresses the synthesis challenge by providing scientists with a free virtual D3 catalog of 73,024 easy-to-synthesize N-acyl unnatural α-amino acids, their methyl esters, and primary amides. The remaining challenge is to document and exploit the bioactivity potential of these compounds. In the current work, a search process is described that retrospectively identifies all virtual D3 compounds classified as bioactive hits in PubChem-cataloged experimental assays. The results provide insight into the broad range of drug-target classes amenable to inhibition and/or agonism by D3-accessible molecules. To encourage computer-aided drug discovery centered on these compounds, a publicly available virtual database of D3 molecules prepared for use with popular computer docking programs is also presented.

Subacute alcohol and/or disulfiram intake affects bioelements and redox status in rat testes

The aim of the study was to investigate if alcohol and disulfiram (DSF) individually and in combination affect bioelements' and red-ox homeostasis in testes of the exposed rats. The animals were divided into groups according to the duration of treatments (21 and/or 42 days): C₂₁/C₄₂ groups (controls); OL₂₁ and OL_22-42 groups (0.5 mL olive oil intake); A_1-21 groups (3 mL 20% ethanol intake); DSF_1-21 groups (178.5 mg DSF/kg/day intake); and A₂₁+DSF_22-42 groups (the DSF ingestion followed previous 21 days' treatment with alcohol). The measured parameters in testes included metals: zinc (Zn), copper (Cu), iron (Fe), magnesium (Mg) and selenium (Se); as well as oxidative stress (OS) parameters: superoxide anion radical (O₂^•-), glutathione reduced (GSH) and oxidized (GSSG), malondialdehyde (MDA), hydrogen peroxide (H₂O₂) decomposition and activities of total superoxide dismutase (tSOD), glutathione-S-transferase (GST) and glutathione reductase (GR). Metal status was changed in all experimental groups (Fe rose, Zn fell, while Cu increased in A₂₁+DSF_24-32 groups). Development of OS was demonstrated in A_1-21 groups, but not in DSF_1-21 groups. In A₂₁+DSF_22-42 groups, OS was partially reduced compared to A groups (A_1-21>MDA>C; A_1-21<GSH<C). High metal-binding affinity of DSF/DDTC changes red-ox homeostasis in rat testes.

Fourteen Years of Experience of Liver Transplantation for Wilson's Disease; a Report on 107 Cases from Shiraz, Iran

BACKGROUND AND AIM

Liver transplantation is a potential cure for liver damage from Wilson's disease but the course of neuropsychiatric manifestations after transplantation remains undetermined.

MATERIAL AND METHODS

In this study, data on all patients who'd received a liver transplant for Wilson's disease at the Shiraz Organ Transplantation Center between December 2000 and March 2014 were reviewed and compared to data on a control group who'd received a liver transplant over the same period but due to other causes.

RESULTS

Out of 2198 patients who'd received a liver transplant in the period; 107 patients were diagnosed with Wilson's disease (21 with fulminant hepatic failure); age of patient ranged from 5 to 59 years; 56.07% of patients in this series had some type of neuropsychiatric manifestation before transplantation, of which 66.67% showed improvement after the procedure. 18 patients had aggravation of neuropsychiatric symptoms after transplantation. These neuropsychiatric symptoms were mostly for anxiety, tremor and depression but there were four cases of new onset dysarthria, rigidity and ataxia in various combinations. Survival rates of 1-month, 1-year, and 5-years for patients with Wilson's disease were 88%, 86%, 82%, respectively, evaluations were not statistically different from that of the control group.

CONCLUSIONS

Liver transplantation showed good long-term results in patients with Wilson's disease, even in those presenting fulminant hepatic failure. Neuropsychiatric manifestations normally show improvement after transplantation but in some cases new onset of manifestations occurred after successful liver transplantation.

Effects of Copper Reduction on Angiogenesis-Related Factors in Recurrent Glioblastoma Cases

Purposeː To evaluate the therapeutic effects of copper reduction on angiogenesis-related factors in patients with glioblastoma multiforme treated by gamma knife radiosurgery. Materials and Methodsː In the present block randomized, placebo-controlled trial, fifty eligible patients with a diagnosis of glioblastoma multiforme who were candidates for gamma knife radiosurgery were randomly assigned into two groups to receive daily either 1gr penicillamine and a low copper diet or placebo for three months. The intervention started on the same day as gamma knife radiosurgery. Serum interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), vascular endothelial growth factor (VEGF) and copper levels were measured at baseline and after the intervention. The serum copper level was used as the final index of compliance with the diet. In order to control probable side effects of intervention, laboratory tests were conducted at the beginning, middle and end of the study. Resultsː The patients had a mean age and Karnofsky Performance Scale of 43.7 years and 75 respectively. Mean serum copper levels were significantly reduced in intervention group. Mean survival time was 18.5 months in intervention group vs. 14.9 in placebo group. VEGF and IL-6 levels in the intervention group were also significantly reduced compared to the placebo group and TNF-α increased less. Conclusionsː It seems that reducing the level of copper in the diet and dosing with penicillamine leads to decline of angiogenesis-related factors such as VEGF, IL-6 and TNF-α. Approaches targeting angiogenesis may improve survival and can be used as a future therapeutic strategy.

Lysyl oxidase isoforms in gastric cancer

Gastric cancer (GC) is the fifth most frequent cancer in the world and shows the highest incidence in Latin America and Asia. An increasing amount of evidence demonstrates that lysyl oxidase isoforms, a group of extracellular matrix crosslinking enzymes, should be considered as potential biomarkers and therapeutic targets in GC. In this review, we focus on the expression levels of lysyl oxidase isoforms, its functions and the clinical implications in GC. Finding novel proteins related to the processing of these extracellular matrix enzymes might be helpful in the design of new therapies, which, in combination with classic pharmacology, could be used to delay the progress of this aggressive cancer and offer a wider temporal window for clinical intervention.

Extracellular Cysteine in Connexins: Role as Redox Sensors

Connexin-based channels comprise hemichannels and gap junction channels. The opening of hemichannels allow for the flux of ions and molecules from the extracellular space into the cell and vice versa. Similarly, the opening of gap junction channels permits the diffusional exchange of ions and molecules between the cytoplasm and contacting cells. The controlled opening of hemichannels has been associated with several physiological cellular processes; thereby unregulated hemichannel activity may induce loss of cellular homeostasis and cell death. Hemichannel activity can be regulated through several mechanisms, such as phosphorylation, divalent cations and changes in membrane potential. Additionally, it was recently postulated that redox molecules could modify hemichannels properties in vitro. However, the molecular mechanism by which redox molecules interact with hemichannels is poorly understood. In this work, we discuss the current knowledge on connexin redox regulation and we propose the hypothesis that extracellular cysteines could be important for sensing changes in redox potential. Future studies on this topic will offer new insight into hemichannel function, thereby expanding the understanding of the contribution of hemichannels to disease progression.

Kinetics and Mechanism of Oxidation of d-Penicillamine in Acidified Bromate and Aqueous Bromine

The oxidation of the biologically active compound d-penicillamine (Depen) by acidic bromate has been studied. The stoichiometry of the reaction is strictly 1 : 1, in which Depen is oxidized only as far as the sulfonic acid with no cleavage of the C–S bond to yield sulfate. Electrospray ionization spectroscopy shows that Depen is oxidized through addition of oxygen atoms on the sulfur centre to successively yield sulfenic and sulfinic acids before the product sulfonic acid. In conditions of excess Depen over the oxidant, sulfenic acid was not observed. Instead, nearly quantitative formation of the dimer was obtained. The dimer, which is the d-penicillamine disulfide species, was formed from a reaction of the putative highly electrophilic sulfenic acid with unreacted Depen in a condensation-type reaction and not through a radical-mediated pathway. Further oxidation of the dimer is slow because it is the most stable intermediate in the oxidation of Depen. In excess oxidant conditions, negligible dimer formation is observed. The reaction of bromine with Depen gives a stoichiometry of 3 : 1 with the same sulfonic acid product. This reaction is so fast that it is essentially diffusion controlled. Our stopped-flow instrument could not capture the oxidation by the first 2 moles of bromine, only the section of the reaction in which the sulfinic acid is oxidized to sulfonic acid.

Targeting copper in cancer therapy: 'Copper That Cancer'

Copper is an essential micronutrient involved in fundamental life processes that are conserved throughout all forms of life. The ability of copper to catalyze oxidation-reduction (redox) reactions, which can inadvertently lead to the production of reactive oxygen species (ROS), necessitates the tight homeostatic regulation of copper within the body. Many cancer types exhibit increased intratumoral copper and/or altered systemic copper distribution. The realization that copper serves as a limiting factor for multiple aspects of tumor progression, including growth, angiogenesis and metastasis, has prompted the development of copper-specific chelators as therapies to inhibit these processes. Another therapeutic approach utilizes specific ionophores that deliver copper to cells to increase intracellular copper levels. The therapeutic window between normal and cancerous cells when intracellular copper is forcibly increased, is the premise for the development of copper-ionophores endowed with anticancer properties. Also under investigation is the use of copper to replace platinum in coordination complexes currently used as mainstream chemotherapies. In comparison to platinum-based drugs, these promising copper coordination complexes may be more potent anticancer agents, with reduced toxicity toward normal cells and they may potentially circumvent the chemoresistance associated with recurrent platinum treatment. In addition, cancerous cells can adapt their copper homeostatic mechanisms to acquire resistance to conventional platinum-based drugs and certain copper coordination complexes can re-sensitize cancer cells to these drugs. This review will outline the biological importance of copper and copper homeostasis in mammalian cells, followed by a discussion of our current understanding of copper dysregulation in cancer, and the recent therapeutic advances using copper coordination complexes as anticancer agents.

Copper improves the anti-angiogenic activity of disulfiram through the EGFR/Src/VEGF pathway in gliomas

Disulfiram (DSF) possesses anticancer activity by inducing apoptosis in vitro and in vivo in a copper (Cu)-dependent manner. DSF also potently inhibits angiogenesis, but the effect of Cu on this anti-angiogenic activity is unknown. Here we show that DSF inhibits the proliferation, migration, invasion, adhesion and complex tube formation of human umbilical vascular endothelial cells (HUVECs). Aortic ring assays and Matrigel plug assays revealed that DSF significantly inhibited the formation of microvessels. Importantly, Cu improved the anti-angiogenic activity of DSF in all these assays, while copper alone had no effect. DSF/Cu treatment of U87 human glioblastoma cells resulted in suppression of VEGF secretion through the EGFR/c-Src/VEGF pathway. Reduction of EGFR phosphorylation disables recruitment of multiple Src homology 2 (SH2) domains, resulting in transcriptional down-regulation of VEGF. The role of EGFR/c-Src/VEGF pathway was further confirmed by using specific inhibitor, which significantly improved the anti-angiogenic activity of DSF/Cu. DSF/Cu also exerted increased anti-tumor effects on subcutaneous and intracerebral U87 xenograft models by reducing microvessel density (MVD) and VEGF expression. These results indicate that Cu improves the anti-angiogenic activity of DSF by targeting the EGFR/Src/VEGF signaling pathway, thus providing a rationale for the use of DSF/Cu rather than DSF alone as an angiogenesis inhibitor in clinical applications.

Antileishmanial Activity of Disulfiram and Thiuram Disulfide Analogs in an Ex Vivo Model System Is Selectively Enhanced by the Addition of Divalent Metal Ions

Current treatments for cutaneous and visceral leishmaniasis are toxic, expensive, difficult to administer, and limited in efficacy and availability. Disulfiram has primarily been used to treat alcoholism. More recently, it has shown some efficacy as therapy against protozoan pathogens and certain cancers, suggesting a wide range of biological activities. We used an ex vivo system to screen several thiuram disulfide compounds for antileishmanial activity. We found five compounds (compound identifier [CID] 7188, 5455, 95876, 12892, and 3117 [disulfiram]) with anti-Leishmania activity at nanomolar concentrations. We further evaluated these compounds with the addition of divalent metal salts based on studies that indicated these salts could potentiate the action of disulfiram. In addition, clinical studies suggested that zinc has some efficacy in treating cutaneous leishmaniasis. Several divalent metal salts were evaluated at 1 μM, which is lower than the normal levels of copper and zinc in plasma of healthy individuals. The leishmanicidal activity of disulfiram and CID 7188 were enhanced by several divalent metal salts at 1 μM. The in vitro therapeutic index (IVTI) of disulfiram and CID 7188 increased 12- and 2.3-fold, respectively, against L. major when combined with ZnCl2. The combination of disulfiram with ZnSO4 resulted in a 1.8-fold increase in IVTI against L. donovani. This novel combination of thiuram disulfides and divalent metal ions salts could have application as topical and/or oral therapies for treatment of cutaneous and visceral leishmaniasis.

Liquid storage of equine semen: Assessing the effect of d-penicillamine on longevity of ejaculated and epididymal stallion sperm

Short-term storage of equine sperm at 5°C in an extender containing milk and/or egg yolk components is common practice in the equine breeding industry. Sperm motility, viability, DNA integrity and, consequently, fertilizing ability decline over time, partly due to reactive oxygen species (ROS) generation. We investigated whether adding the anti-oxidant d-penicillamine to a commercial milk/egg yolk extender delayed the decrease in semen quality. Semen was recovered on four consecutive days from eight 3-year old Warmblood stallions. On day 5, seven of the stallions were castrated and sperm recovered from the caudae epididymides. Ejaculated samples were split, and one portion was centrifuged and re-suspended to reduce seminal plasma content. All samples were diluted to 50millionsperm/ml and divided into two portions, one of which was supplemented with 0.5mM d-penicillamine. After 48h, 96h, 144h and 192h storage, sperm motility was assessed by computer-assisted semen analysis (CASA), viability by SYBR14/PI staining, and DNA integrity using the sperm chromatin structure assay (SCSA). d-Penicillamine had no effect on motility of ejaculated sperm (P>0.05) but reduced total and progressive motility of epididymal sperm. Sperm chromatin integrity was not influenced by storage time, seminal plasma or d-penicillamine. In short, adding d-penicillamine to a commercial semen extender was neither beneficial nor detrimental to the maintenance of quality in ejaculated semen stored at 5°C. The negative effect on motility of epididymal sperm may reflect differences in (membrane) physiology of spermatozoa that have not been exposed to seminal plasma.

"Turn-on" fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules

A "turn-on" thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future.

Cracking the cytotoxicity code: apoptotic induction of 10-acetylirciformonin B is mediated through ROS generation and mitochondrial dysfunction

A marine furanoterpenoid derivative, 10-acetylirciformonin B (10AB), was found to inhibit the proliferation of leukemia, hepatoma, and colon cancer cell lines, with selective and significant potency against leukemia cells. It induced DNA damage and apoptosis in leukemia HL 60 cells. To fully understand the mechanism behind the 10AB apoptotic induction against HL 60 cells, we extended our previous findings and further explored the precise molecular targets of 10AB. We found that the use of 10AB increased apoptosis by 8.9%-87.6% and caused disruption of mitochondrial membrane potential (MMP) by 15.2%-95.2% in a dose-dependent manner, as demonstrated by annexin-V/PI and JC-1 staining assays, respectively. Moreover, our findings indicated that the pretreatment of HL 60 cells with N-acetyl-l-cysteine (NAC), a reactive oxygen species (ROS) scavenger, diminished MMP disruption and apoptosis induced by 10AB, suggesting that ROS overproduction plays a crucial rule in the cytotoxic activity of 10AB. The results of a cell-free system assay indicated that 10AB could act as a topoisomerase catalytic inhibitor through the inhibition of topoisomerase IIα. On the protein level, the expression of the anti-apoptotic proteins Bcl-xL and Bcl-2, caspase inhibitors XIAP and survivin, as well as hexokinase II were inhibited by the use of 10AB. On the other hand, the expression of the pro-apoptotic protein Bax was increased after 10AB treatment. Taken together, our results suggest that 10AB-induced apoptosis is mediated through the overproduction of ROS and the disruption of mitochondrial metabolism.

Oxygen-Mediated Enzymatic Polymerization of Thiol-Ene Hydrogels

Materials that solidify in response to an initiation stimulus are currently utilized in several biomedical and surgical applications; however, their clinical adoption would be more widespread with improved physical properties and biocompatibility. One chemistry that is particularly promising is based on the thiol-ene addition reaction, a radical-mediated step-growth polymerization that is resistant to oxygen inhibition and thus is an excellent candidate for materials that polymerize upon exposure to aerobic conditions. Here, thiol-ene-based hydrogels are polymerized by exposing aqueous solutions of multi-functional thiol and allyl ether PEG monomers, in combination with enzymatic radical initiating systems, to air. An initiating system based on glucose oxidase, glucose, and Fe²⁺ is initially investigated where, in the presence of glucose, the glucose oxidase reduces oxygen to hydrogen peroxide which is then further reduced by Fe²⁺ to yield hydroxyl radicals capable of initiating thiol-ene polymerization. While this system is shown to effectively initiate polymerization after exposure to oxygen, the polymerization rate does not monotonically increase with raised Fe²⁺ concentration owing to inhibitory reactions that retard polymerization at higher Fe²⁺ concentrations. Conversely, replacing the Fe²⁺ with horseradish peroxidase affords an initiating system is that is not subject to the iron-mediated inhibitory reactions and enables increased polymerization rates to be attained.