Unveiling the metal-driven death: ferroptosis and cuproptosis in leukemia

Abstract

Cell death is essential for tumor cells and can occur due to damage or aging. Traditional concepts such as necrosis and apoptosis do not completely account for it. New forms, such as cuproptosis and ferroptosis, involve metal ion buildup and relate to cell metabolism, signaling, and drug resistance. These forms are particularly relevant in leukemia development. This review discusses the advancements in understanding the mechanisms of ferroptosis and cuproptosis and their impact on leukemia, opportunities and challenges in leukemia treatment are explored, emphasizing the potential therapeutic direction of ferroptosis and cuproptosis, to provide new theoretical basis and strategies for the treatment of clinical leukemia diseases.

Introduction

The maintenance of normal tissue function and structure heavily relies on the process of cell death. Programmed cell death (PCD), or regulated cell death (RCD), involves cell death that is influenced by various biomacromolecules, unlike accidental cell death (ACD) [1]. This discussion mainly focuses on two new types of regulated cell death: ferroptosis and cuproptosis. Both iron and copper are essential nutrients, and any imbalance, either in surplus or shortage, can disrupt cellular functions and result in cell death.

Essential nutrients such as iron and copper are crucial, but their excess or deficiency can result in impaired cellular functions and cell death. Diseases can arise from disruptions in the balance of iron or copper [2], which are vital for tumorigenesis and cancer progression [3, 4]. The term 'ferroptosis' was created when researchers conducted screens for small-molecule compounds that could stop the growth of RAS-mutant cancer cells. During the 1950s, Harry Eagle and his colleagues discovered that cells lacking cysteine exhibited a distinct pattern of cell death compared to deficiencies in other amino acids. In the 1970 s, researchers found a liver cell death dependent on cysteine and glutathione (GSH) reduction, and noted that alpha-tocopherol, which prevents lipid peroxidation, protected cells from dying due to shortages of GSH and cysteine. Glutathione peroxidase 4 (GPX4), an enzyme capable of inhibiting iron-induced lipid peroxidation, was isolated by Ursini et al. in 1982. Cell death linked to lipid peroxidation and oxidative stress is inhibited by GPX4. Dolma et al. identified in 2003 that erastin, a small molecule compound, could specifically inhibit RAS-expressing tumor cells. The cell death caused by erastin did not exhibit apoptotic characteristics and was not prevented by apoptosis inhibitors, indicating a novel form of non-apoptotic cell death. In 2012, the concept of 'ferroptosis' was established by Dixon et al. to refer to cell death triggered by erastin [5].

Since the discovery of ferroptosis, new types of cell death, such as cuproptosis, have been identified based on their inducers. Research from as early as 1989 showed that too much copper could cause cells to die, but the exact process was not understood. In 2022, Peter Tsvetkov and his team identified a new cell death mechanism induced by copper (Cu), distinct from apoptosis, necroptosis, pyroptosis, and ferroptosis, and named it 'cuproptosis' (Figs. 1, 2) [6].

Fig. 1.

Timeline of ferroptosis and cuproptosis research. The historical events contributing to the discovery of ferroptosis and cuproptopsis advances of iron and copper associated cell death are depicted in the timeline

Fig. 2.

Molecular mechanisms of ferroptosis. The buildup of lipid peroxidation results in ferroptosis, which destroys membrane structures. Polyunsaturated fatty acids-containing phospholipids (PUFA–PLs) must be synthesized and undergo peroxidation for ferroptosis to take place. The regulation of ferroptosis sensitivity involves multiple factors, including GSH, REDOX systems, such as System Xc-, GPX4, the CoQ–NAD(P) pathway, and the glutamine metabolic pathway

As a vital transition metal, copper plays a double-edged role in cellular functions. While it acts as a co-factor for numerous enzymes by transferring electrons, copper buildup can cause various cellular metabolic issues and ultimately result in cell death [7]. The 2019 study by Tsvetkov et al. focused on Cu-dependent death as they examined the anticancer properties of elesclomol (ES), known as a Cu ionophore [8]. The study revealed that ES treatment in a multiple myeloma mouse model lowered the cancer cells' resistance to toxicity from proteasome inhibitors. From a mechanistic perspective, Cu(II) bound to ES interacts with the mitochondrial enzyme ferredoxin 1 (FDX1) and is reduced to Cu(I), resulting in elevated reactive oxygen species (ROS) levels (Fig. 1). Analyses from recent studies have shown a potential association between ferroptosis and cuproptosis [9, 10]. The swift progress in understanding ferroptosis and cuproptosis, two emerging cell death pathways, has led to more research on their effects on leukemia. These pathways offer new perspectives for leukemia treatment. In the future, addressing the relationship between them could be an effective cancer treatment strategy. This review serves to provide a comprehensive introduction to the specific molecular mechanisms of both ferroptosis and cuproptosis, shedding light on the relationship between these two forms of RCD, and provides new targets and new ideas for the diagnosis and treatment of cancer.

Mechanism of ferroptosis and cuproptosis

Ferroptosis

The buildup of lipid peroxidation results in ferroptosis, which destroys membrane structures. Polyunsaturated fatty acids-containing phospholipids (PUFA–PLs) must be synthesized and undergo peroxidation for ferroptosis to take place. The regulation of ferroptosis sensitivity involves multiple factors, including GSH, REDOX systems, such as the cystine glutamate transporter (System Xc-), GPX4, the CoQ–NAD(P) pathway, and the glutamine metabolic pathway (Fig. 2).

PUFA–PL synthesis and peroxidation: Ferroptosis is primarily driven by the synthesis and peroxidation of PUFA–PLs. Ferroptosis is initiated by the catalytic oxidation of phospholipids with PUFA into polyunsaturated fatty acids, resulting in a deadly buildup of lipid peroxides on the cell membrane and eventual membrane rupture. This is the essential condition for ferroptosis [11]. Acyl-coenzyme A (CoA) synthetase long chain family member 4 (ACSL4) and lysophosphatidylcholine acyltransferase 3 (LPCAT3) play essential roles in the synthesis of PUFA–PL [12]. ACSL4 and LPCAT3 are crucial in the synthesis and modification of arachidonic acid (AA), which can activate polyunsaturated fatty acids (PUFAs) and influence membrane characteristics [13]. The enzyme ACSL4 aids in connecting free PUFAs, which leads to the esterification of AA and Adrenic acid (AdA) into Phosphatidylethanolamine (PE). The Fenton reaction (an advanced oxidation treatment method based on hydroxyl radical reaction) induced oxidative stress is heightened by excess AA, which also causes an increase in anti-inflammatory lipoxinA4 (LXA4) and a decrease in prostaglandin E2 (PGE2), substances that are suggested to promote and inhibit cell growth, respectively, which is required for synthesis of some PUFAs [14]. The enzyme human cytochrome P450 redox reductase (POR) moves electrons from NAD(P)H to oxygen, creating hydrogen peroxide, that later combines with iron to form reactive hydroxyl radicals, causing peroxidation of the PUFA chains in membrane phospholipids and disrupting membrane integrity during ferroptosis [15].

Iron metabolism: As a crucial nutrient, iron is involved in ATP production through the mitochondrial chain complex, DNA synthesis in ribonucleic acid reductase, oxygen transport, and factors sensitive to oxygen, such as hypoxia-inducible factor (HIF) and proline hydroxylase, and many other enzymes. The equilibrium of iron absorption, recycling, and loss sustains systemic iron homeostasis. Iron is primarily obtained from dietary sources and the breakdown of old red blood cells, existing in the forms of Fe2 + and Fe3 +  [16]. Ferrous ions are absorbed by intestinal cells via active transport in the gastrointestinal tract. Once they exit enterocytes, Fe3 + attaches to transferrin (TF) and is transported through the bloodstream. Located on the cell membrane, the transferrin receptor 1 (TFR1) recognizes and brings in this complex. Through the basolateral membrane, iron is internalized into the blood via ferroportin 1 (FPN1), the only recognized iron exporter, by attaching to ferriferous carriers with lipidin-2 (LCN2) and subsequent endocytosis (Figs. 1, 2) [17]. After being absorbed, the iron attached to transferrin is converted from Fe3 + to Fe2 + by the STEAP3 metalloreductase within the endosome and is subsequently moved to the cytosol through solute carrier family 11 member 2 (SLC11A2). Cells become more sensitive to ferroptosis when iron is enriched [14].

A variety of redox-based metabolic processes, essential for generating cellular ROS, also require iron. This type of necrosis, known as ferroptosis, is regulated and relies on ROS [18]. The onset of ferroptosis occurs when there is an imbalance between the detoxification of lipid hydroperoxides (LOOH) and the accumulation of iron-dependent lipid reactive oxygen species (L-ROS). These oxidative activities of iron are significant as they can facilitate tumor formation and are considered vital for cancer progression [19]. Many cellular activities might influence how sensitive cells are to ferroptosis by adjusting the amount of labile iron they contain [20–22].

The GPX4–GSH system: The defense against ferroptosis involves cellular antioxidant systems that directly counteract lipid peroxides. GPX4 is a member of the GPX protein family and acts as a phospholipid hydroperoxidase, converting phospholipid hydroperoxides (AA/AdA-PE-OOH) into phospholipid alcohols (PLOH) [23]. There are three subtypes of GPX4, each found in distinct cellular locations: cytoplasmic, mitochondrial, and nuclear GPX4 [24]. The specific functions of GPX4 isoforms are determined by their localization in various subcellular organelles. mGPX4 acts as a mitochondrial anti-apoptosis enzyme and a structural protein in sperm, while nGPX4 is dedicated to safeguarding chromatin condensation, genetic integrity, and fertility. cGPX4 is the only enzyme that provides protection against ferroptosis [25]. As a major regulator of ferroptosis, GPX4 uniquely converts lipid hydroperoxides into non-toxic lipid alcohols, which helps to inhibit lipid peroxidation. Selenium and GSH regulate the expression or activity of GPX4 [26]. In mammalian cells, GSH is the most common reducing agent and acts as a cofactor for many enzymes. It is a thiol-containing tripeptide composed of glycine, glutamic acid, and cysteine, with cysteine being the rate-limiting precursor [27]. To maintain cellular and organismal balance, the oxidative system, which includes iron ions, Fenton reactions, and ROS, primarily counteracts the antioxidant system made up of System Xc-, GPX4, and GSH (System Xc-/GSH/GPX4 axis).

Widely present in the phospholipid bilayer, System Xc- functions as an amino acid reverse transporter and is vital to the cellular antioxidant system. SLC7A11/xCT/System Xc-, an amino acid antiporter, is made up of two essential components: the light-chain subunit SLC7A11 and the heavy-chain subunit SLC3A2 [28] (Fig. 2). Cysteine and glutamic acid are moved in and out of the cell via system Xc-, where they are involved in GSH production [29]. Inhibiting cysteine uptake can impair system Xc-, which influences GSH synthesis and eventually diminishes GPX activity, leading to a reduction in cellular antioxidant capacity, lipid ROS accumulation, and inducing ferroptosis [24]. In addition, many factors such as TP53 [30], NRF2/NFE2L2 [31], BRCA1-associated protein 1 (BAP1) [32], BECN1 [33], and peroxiredoxin 6 (PRDX6) [26, 34] regulate the expression or activity of SLC7A11, forming a complex network to manage GSH levels in ferroptosis.

The CoQH2 system: CoQH2 acts as a natural inhibitor of ferroptosis and functions as a lipophilic antioxidant that traps free radical-trapping antioxidant (RTA). Although CoQ is primarily produced in the mitochondria, it is also present in non-mitochondrial membranes, such as the plasma membrane [35]. Later, ferroptosis suppressor protein 1 (FSP1) converts CoQ into CoQH2 using its oxidoreductase function, providing antioxidant benefits [36]. Through the CoQ-mediated blockade of ferroptosis, the FSP1–CoQ–NAD(P)H axis exerts a protective effect on cells. FSP1, which is also referred to as AIFM2, is found in the plasma membrane. The study by Li et al. [36]. reveals that the carboxy-terminal domain is key to FSP1's catalytic activity and ferroptosis prevention through its role in functional dimerization, and the creation of two active sites on either side of FAD, each responsible for reducing ubiquinone and uniquely hydroxylating FAD. In addition, CoQ was found to elucidate the connection between the GSH–GPX4 pathway and the FSP1–CoQ–NAD(P)H-axis, boosting the ability to capture free radicals and protect cells [37]. DHODH is capable of controlling the de novo synthesis of pyrimidine. Disabling DHODH leads to significant mitochondrial lipid peroxidation and ferroptosis in cancer cells with GPX4^low levels, and works together with ferroptosis inducers to cause these effects in cancer cells with GPX4^high levels [5]. Research [38] suggests that DHODH–CoQ, together with mitochondrial GPX4, contributes to defending against the extraction of iron from mitochondria. Li et al. [39]. target HCC tissues with multi-siRNA, boost sorafenib-induced ferroptosis by suppressing GPX4 and DHODH. There are still unanswered questions regarding the potential involvement of other mitochondrial enzymes that produce CoQH2 in the regulation of ferroptosis (Fig. 2). Ferroptosis is described as a distinct form of cell death that unifies previously separate aspects of cell metabolism into a cohesive framework. The involvement of ferroptosis in a particular process cannot be confirmed solely by the suppression of cell death with a single ferroptosis inhibitor. Although there has been substantial progress in comprehending the mechanisms governing ferroptosis, the specific molecular event causing cell death via ferroptosis is still unclear. Additional research data will be necessary to confirm this in the future.

Cuproptosis

Cuproptosis happens when copper directly binds to lipoylated components in the TCA cycle, leading to the clumping of lipoylated proteins and the loss of Fe–S cluster proteins, causing proteotoxic stress and eventually resulting in cuproptosis (Fig. 3).

Fig. 3.

Molecular mechanisms of cuproptosis. Cuproptosis happens when copper directly binds to lipoylated components in the TCA cycle, leading to the clumping of lipoylated proteins and the loss of Fe–S cluster proteins, causing proteotoxic stress and eventually resulting in cuproptosis

Copper in cuproptosis: Copper absorption primarily happens in the small intestine, where dietary Cu(II) must first be reduced to Cu(I) by cell-surface metalloreductases of the six-transmembrane epithelial antigen of the prostate (STEAP) family before enterocytes can absorb it. Copper ions were absorbed by the small intestine epithelium through copper transporter 1 (CTR1), also known as solute carrier family 31 member 1 (SLC31A1), which is encoded by SLC31A1 on the cell surface. The body's distribution of copper happens in two phases. First, copper from the diet is transported from the intestines to the liver and kidneys via the blood, where it is bound to albumin and transcuprein. Subsequently, copper is transported from the liver to various tissues with the help of the circulating carrier protein ceruloplasmin [40]. Antioxidant 1 (ATOX1) can transport copper ions to the trans-Golgi network and also deliver copper to the nucleus. Transport proteins are responsible for actively exporting excess copper ions from cells. It was thought that the storage of copper was facilitated by metallothionein1/2 (MT1/2), two proteins rich in thiol groups, which bind copper ions through their cystine residues in a pH-dependent way. However, their precise capability to bind and transfer copper remains unclear. Excess copper is expelled into the bile and exits the body through the action of ATPase copper transporting beta (ATP7B). Once transported to the cell surface via the bloodstream, divalent copper ions are converted into monovalent copper ions with the help of STEAP proteins, which are attached and kept in a reduced state by two His–Met–Asp clusters at the nitrogen end of CTR, and consequently moved into the cell [41]. ATPase copper transporting alpha (ATP7A) and ATP7B, which are copper-transporting ATPases, are crucial for exporting copper ions outside the cell. Through the assistance of the copper chaperone ATOX1, copper was transferred across the epithelium and then exported into the bloodstream by ATP7A [42] (Fig. 3).

As a metal involved in redox reactions, copper ions contribute to the Fenton reaction, leading to the formation of ROS. These ROS, induced by copper, enhance lipid peroxidation and diminish GSH, increasing cellular vulnerability to oxidative damage [43]. The presence of copper boosted mitochondrial protein lipoylation and directly attached to dihydrolipoamide S-acetyltransferase (DLAT), facilitating the aggregation of lipoylated DLAT through disulfide bonds. Significantly, FDX1 was identified as a new factor in lipoylation, leading to the buildup of harmful lipoylated DLAT and resulting in cuproptotic cell death. Furthermore, mass spectrometric proteomics indicated that the degradation of Fe–S cluster proteins dependent on FDX1 could promote cuproptosis [6]. Copper concentrations showed a notable increase in tumor tissues and serum [44, 45]. The copper transport system releases cupric ions in oxidative environments, the protein p97, also referred to as valosin-containing protein (VCP), is crucial for maintaining cellular protein balance and is disrupted by interference with the zinc finger motifs of Npl4, a p97 cofactor, which eventually causes cell death [46].

Mitochondrial apoptosis: The main source of ROS is intracellular redox reactions, where mitochondria are essential [47], which corresponds to the relationship between cuproptosis and mitochondrial metabolism. In studies on ES-induced cell death, it is widely accepted that elevated ROS levels, influenced by various mitochondrial factors, mediate the cell death caused by ES. In 2019, Tsvetkov et al. found that Hi-Mitocondition, characterized by enhanced mitochondrial respiration through the replacement of Glucose with Galactose, leads to proteasome inhibitor (PI) resistance but also heightens vulnerability to ES, the copper ionophore [8]. Studies conducted in 2021 on glioblastoma stem-like cells demonstrated that ES–Cu can interact directly with the mitochondrial membrane, resulting in changes to the mitochondrial membrane potential [48].

Cuproptosis is significantly influenced by the mitochondrial apoptosis pathway, where the release of mitochondrial proteins depends on the mitochondrial membrane potential, a process controlled by the BCL2 protein family [43]. Cuproptosis primarily affects the mitochondrion, causing oxidative harm to its membrane and disrupting the function of TCA cycle enzymes. In vitro studies have demonstrated that Cu can prevent the formation of Fe–S clusters by hindering the function of mitochondrial assembly proteins [49]. Eliminating either FDX1 or lipoyl synthase (LIAS) results in a buildup of pyruvate and α-ketoglutarate, which decreases protein lipoylation and hinders cuproptosis [8, 50]. Besides increasing ROS levels, the interaction between DSF–Cu and Npl4 was believed to be strongly linked to cuproptosis [43]. Exposure to high doses of Cu can lead to oxidative stress by raising ROS levels. Furthermore, its exposure triggered liver cell apoptosis through the mitochondrial apoptotic pathway, markedly elevating the mRNA and protein expression levels of cytosolic cytochrome (Cyt c), apoptosis-inducing factor (AIF), endonuclease G (Endo G), apoptosis protease-activating factor-1 (Apaf-1) [51]. Copper-depleting nanoparticle (CDN) preferentially remove copper from the mitochondria in cancer cells rather than causing a systemic depletion, resulting in reduced oxygen consumption and oxidative phosphorylation, which led to a disruption in mitochondrial membrane potential and increased oxidative stress, triggering a shift to glycolysis and decreasing ATP production in TNBC cells, ultimately causing apoptosis [52]. The depletion of mitochondrial energy triggers AMP-activated protein kinase (AMPK), which enhances cuproptosis in liver and pancreatic cancer cells [53].

Cuproptosis key genes: Through whole genome knockout, Tsvetkov et al. [6]. discovered ten genes, the removal of which could modify the risk of cuproptosis. Cuproptosis-related key (CKGs) genes are essential for cellular functions and are commonly associated with energy metabolism and the regulation of metal homeostasis.

The gene FDX1 encodes Ferredoxin1, which is an iron–sulfur protein involved in numerous redox reactions. FDX1 and FDX2 are two isoforms found in human mitochondria, playing roles in both cytochrome P450 (play a pivotal role in the detoxification of xenobiotics) steroid transformation and Fe–S protein biogenesis [54]. The way ES transports copper is different from other copper-transporting drugs used in clinical settings [55]. Due to its significant role in cancer formation and immune function, FDX1 can be a potential target for therapy and a prognostic marker in human cancer cells [56].

Lipoic acid (LA) is an essential compound necessary for enzymes that participate in the oxidative decarboxylation of intermediates in mitochondrial metabolism. The proteins produced by Lipoyltransferase 1 (LIPT1) and LIAS are part of the LA pathway, which facilitates the post-transcriptional lipoic modification of proteins, such as PDC, playing a vital role in normal cellular functions and cuproptosis [57]. LIAS mutations play a role in altering epigenetic mechanisms and the development of cancer. LIAS has the ability to bind directly to FDX1, which influences the lipoylation of proteins within cells [50]. LIAS might play an important role in the development of different cancers. High LIAS levels in lung cancer are linked to a poor prognosis, whereas in KIRC and ovarian cancer, they are associated with a better prognosis. Hypoxia, angiogenesis, and DNA repair were linked to LIAS expression [58]. The suppression of LIPT1 gene expression inhibited the proliferation and invasion of cancer cells [59]. Furthermore, LIPT1 expression demonstrated a positive correlation with PD-L1 expression and a negative association with the infiltration of regulatory T cells (Tregs) [60].

DLAT, dihydrolipoamide dehydrogenase (DLD), pyruvate dehydrogenase A1 (PDHA1) and pyruvate dehydrogenase beta subunit (PDHB) functioned as three essential subunits of pyruvate dehydrogenase complex (PDC), a crucial part of the mitochondrial aerobic respiration process, and played a significant role in the cuproptosis process, with its expression levels thought to be linked to tumor prognosis [6]. PDHA1 and PDHB constitute the α1 and β subunits of the E1 component of PDC, respectively, and together they mediate pyruvate decarboxylation as pyruvate dehydrogenase. By binding to the PDHA1 gene promoter, AP2α suppressed PDHA1, which facilitated malignant activities in cervical cancer (CC) cells [61]. By stabilizing PDHA1 mRNA, the m6A-mediated circRBM33–FMR1 complex can boost mitochondrial metabolism, which aids in the progression of prostate cancer and diminishes the enhanced effectiveness of ARSI in treating the disease [62]. Deletion of the deglycase DJ-1 also hinders the differentiation of inducible Treg cells, especially in aged mice, and this impairment is mediated by PDHB regulation [63]. The elimination of PDHB caused a metabolic shift in the TCA cycle, impairing mitochondrial function and reducing HCC cell growth when glutamine is scarce [64]. As a common element, DLD is part of four multienzyme complexes that aid in the oxidation of carbohydrates, lipids, or amino acids. In melanoma cells, the suppression of DLD expression resulted in increased intracellular ROS and decreased mitochondrial membrane potential, which induced autophagy cell death [65]. DLAT is an essential enzyme within the pyruvate dehydrogenase (PDH) complex that facilitates the conversion of pyruvate into acetyl-CoA. High DLAT expression in LIHC, excluding cuproptosis, could facilitate tumor growth by triggering autophagy and hindering anti-tumor immunity [66].

Research has demonstrated that cyclin-dependent kinase inhibitor 2 A (CDKN2A), glutaminase (GLS), and metal-regulatory transcription factor 1 (MTF1) are associated with cell sensitivity to cuproptosis. CDKN2A is highly expressed in the majority of cancer patients and is linked to poor prognostic results. It has the highest mutation rate (49%) among all genes related to cuproptosis in cancer [67]. The proliferation, migration, and suppression of cuproptosis in HCC cells are facilitated by CDKN2A and GLS [68]. As a crucial enzyme in glutamine metabolism, GLS has been extensively linked to human cancers. GLS-driven glutaminolysis is both a prognostic marker and a therapeutic target for improving prostate cancer treatment with radiation. MTF1 is a crucial transcription factor that senses metals and can bind to conserved DNA sequences known as metal response elements. By affecting the levels of GSH and MT within cells, GLS and MTF-1 may alter the cells' sensitivity to cuproptosis. Metal-specific transcription activation can be controlled by a single nucleotide within the MTF1 binding region. PiC2 (SLC25A3), a mitochondrial Cu + transporter, is regulated by MTF1 and plays a key role in Cu delivery to the mitochondria [69] (Table 1).

Table 1.

Roles and functions of ferroptosis and cuproptosis regulators

Mechanism	Roles and functions	Refs.
PUFA–PL synthesis and peroxidation	Leading to a lethal accumulation of lipid peroxides on the cell membrane and ultimately causing the membrane to rupture	[11–15]
Iron metabolism	Iron plays a role in ATP production via the mitochondrial chain complex and is crucial for producing cellular ROS	[16–18]
The GPX4–GSH system	Transforms lipid hydroperoxides into harmless lipid alcohols, aiding in the prevention of lipid peroxidation	[23–28]
The CoQH2 system	Enhancing the capacity to trap free radicals and safeguard cells	[35–38]
Copper in cuproptosis	Copper ions play a role in the Fenton reaction, resulting in the production of ROS and heightening cellular susceptibility to oxidative harm	[40–44]
Mitochondrial apoptosis	Intracellular redox reactions, primarily occurring in mitochondria, are the main source of ROS	[47–49]
Cuproptosis key genes	Crucial for cell activities and often linked to energy metabolism and metal balance regulation	[54–68]

Correlation between cuproptosis and ferroptosis

Researchers have discovered a connection between cuproptosis and ferroptosis in cancer. The aggregation of copper-dependent lipoylated proteins in primary liver cancer cells can be increased by ferroptosis inducers sorafenib and erastin, thereby enhancing cuproptosis. The mechanism by which sorafenib and erastin function involves boosting protein lipoylation by hindering FDX1 protein degradation via mitochondrial matrix-related proteases, and lowering GSH synthesis by restricting cystine import [70]. The role of copper in promoting ferroptotic cell death involves the autophagic degradation of GPX4, while cuproptosis remains unaffected. In a mouse model of pancreatic cancer, copper amplifies tumor suppression through ferroptosis, whereas copper chelators mitigate experimental acute pancreatitis related to ferroptosis [71]. In vitro experiments with HGL5 cells revealed that melatonin lowered markers of oxidative stress, boosted mitochondrial function, normalized the expression of genes linked to glycolysis and the TCA cycle, and adjusted the expression of genes related to cuproptosis and ferroptosis [72].

The processes of ferroptosis and cuproptosis are notably associated with mitochondrial metabolism, with GSH serving as a mutual hub, albeit with varying functions, alongside the mitochondrial TCA cycle. The interaction between the two processes in cancer, whether cooperative or conflicting, cannot be generalized. Future studies should aim to investigate the interactions between cuproptosis and ferroptosis. Consequently, a promising cancer treatment could involve using a ferroptosis inducer alongside a copper ionophore to target both processes.

The role of ferroptosis and cuproptosis in leukemia

Leukemia is a collection of diverse blood stem/progenitor cell cancers marked by the unusual growth of immature cells in the bone marrow, disrupting normal blood cell formation. Chemotherapy, immunotherapy, and hematopoietic stem cell transplantation (HSCT) remain the main therapeutic approaches for leukemia at this time. Even with improvements in treatment, the outcomes are still disappointing. The primary causes of treatment failure are relapse, refractory disease, and resistance to chemotherapy. Leukemia patients currently face a shortage of new treatment methods. Emerging therapies such as ferroptosis and cuproptosis-induced cell death are currently being widely researched in leukemia treatment, presenting new approaches for managing leukemia patients.

Acute myeloid leukemia

Acute myeloid leukemia (AML) is a clonal blood disorder resulting from various genetic and epigenetic defects, marked by disrupted differentiation and unchecked cell growth, leading to different outcomes. Ferroptosis and cuproptosis offer a novel approach for treating AML, with several drugs demonstrated to trigger these processes.

Sorafenib, known as a tyrosine kinase inhibitor, has been found to be effective in treating AML patients with FLT3–ITD mutations [73]. Potential therapeutic agents for targeting cuproptosis in AML, including Sorafenib, were suggested by drug sensitivity analysis [74]. Involved in chromatin remodeling, DNA recombination, and repair, high mobility base Box 1 (HMGB1) is a transcription factor. The capacity of HMGB1-deficient cuproptotic cells to trigger inflammatory cytokine production through receptors specific to advanced glycosylation end products is substantially reduced [53]. The study by Zheng et al. demonstrated that BMAL1 inhibits ferroptosis in AML cells through the BMAL1–HMGB1–GPX4 pathway, and reducing BMAL1 can increase sorafenib's effectiveness [75]. New approaches for clinical AML patients with resistance to sorafenib are suggested by these studies.

The novel drug APR-246 targets TP53-mutant AML by increasing oxidative stress through GSH depletion and thioredoxin reductase inhibition, causing ROS accumulation and promoting the death of tumor cells [76, 77]. The early death of AML cells after being exposed to APR-246 is inhibited by iron chelators, lipophilic antioxidants, and lipid peroxidation inhibitors. APR-246, when associated with the induction of ferroptosis, had a synergistic impact on increasing cell death, both in live models and in experimental conditions [78]. Cuproptosis has been the subject of limited studies. TP53 is responsible for regulating the synthesis of iron–sulfur clusters and the copper chelator GSH, key elements of the cuproptotic pathway, hinting that this tumor suppressor could participate in cuproptosis [79]. This offers novel insights for the investigation of cuproptosis.

NRF2, or nuclear factor erythroid 2-related factor 2, plays a key role in managing cellular antioxidative responses, inflammation, and maintaining redox balance. Ferroptosis is selectively initiated in AML due to the excessive activation of the NRF2/HO-1 pathway by Z-LIG, and the antitumor effect is partially diminished by NRF2 knockout, which inhibits ferroptosis [80]. According to Yu et al. [81], erastin, which induces ferroptosis, heightened the anti-AML effects of venetoclax, and blocking NRF2 could further enhance AML cell death caused by venetoclax via the ferroptosis mechanism. Du and colleagues [82] discovered that circSpna2 interacts with the ubiquitin ligase Keap1, affecting the NRF2–Atp7b signaling pathway and impacting cuproptosis. Simultaneously, Qiao et al. created copper carriers that self-destruct to induce cuproptosis by interfering with the antioxidant defense mechanism of tumor cells, specifically by blocking the NRF2–NQO1 signaling pathway [83]. New mechanisms are emerging to address the gaps in clinical treatment, offering a theoretical foundation for future precise targeted therapies.

NEAT1 interacts with cytoplasmic disheveled 2 (DVL2) and tripartite motif containing 56 (TRIM56), leading to the breakdown of DVL2 and suppression of Wnt signaling, thereby hindering the self-renewal of AML stem cells. Erastin, known as a ferroptosis inducer, boosted NEAT1 expression by promoting the interaction of p53 with the NEAT1 promoter [84]. The enzyme acetaldehyde dehydrogenase 3a2 (Aldh3a2) depends on l-gmp and is not present in n-gmp. Its inhibition, along with GPX4 inhibition, which triggers ferroptosis, was synthetically lethal [85]. The CRISPR–Cas9 loss-of-function screening indicated that a lack of iron–sulfur clusters (ISC) boosts cuproptosis, with the loss of the mitochondrial ISC transporter ABCB7 being synthetically lethal to UM4118. The SF3B1 mutation in AML results in the missplicing and decreased expression of ABCB7, making it vulnerable to copper ionophores [86]. Amplifying the effects of ferroptosis and cuproptosis as a new form of RCD could be a novel approach for drug development and disease treatment, but extensive studies are lacking, necessitating further research. Treating leukemia continues to present numerous challenges.

Acute lymphoblastic leukemia

ALL, or acute lymphoblastic leukemia, is a frequent blood system malignancy that presents as the abnormal clonal expansion of naive or immature T and B lymphocytes.

Vincristine (VCR) is commonly utilized to treat ALL. By boosting lipid ROS and iron levels, LINC00618 hastens ferroptosis and lowers SLC7A11 expression, thereby promoting VCR-induced ferroptosis and apoptosis [87].

RSL3 attaches to GPX4 and deactivates it, leading to ferroptosis and cuproptosis controlled by GPX4. Studies found that LCN2 was significantly expressed in T-ALL, and its suppression increased RSL3-triggered ferroptotic cell death in T-ALL cells [88]. The proliferation of cell lines was not suppressed by RSL3 (ferroptosis inducers); however, they did impede MYC and cyclin D3 expression and signaling in T-ALL cells. MYC and cyclin D3 expression was interrupted by GPX4 knockdown and RSL3 treatment [89]. The comparison of experimental and calculated electronic circular dichroism (ECD) spectra revealed that Penicitrinol B (6) significantly hindered RSL3-induced ferroptosis by reducing lipid peroxidation, and Penicitrinol A (7) was effective in inhibiting [90]. They might be linked to each other.

The viability of T-ALL cell lines was greatly reduced by poricoic acid A (PAA), which also caused G2 cycle arrest and apoptosis in vitro, with these actions being dependent on ROS. Ferroptosis was initiated in T-ALL cells by PAA treatments, which also reduced GSH levels [91]. Lalonde et al. [92]. discovered through genome-wide CRISPR screens that ferroptosis is a new therapeutic target in ALL, highlighting its important role in Ph-neg B-ALL [93]. It may shed new light on the progression of ferroptosis in ALL.

Chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by varying genetic traits and responses to treatment. CLL involves the cloning and growth of mature CD5-positive B cells in the blood, bone marrow, lymph nodes, and spleen, leading to a weakened immune system, organ malfunction, and gradual systemic failure and depletion.

In the CLL field, ferroptosis and cuproptosis are not as thoroughly explored. Transcriptomic analysis of CLL cell lines resistant to ibrutinib or venetoclax indicated that SpiD3 treatment prominently influenced pathways, such as ferroptosis and oxidative stress [94]. This represents a novel approach in inducing apoptosis in tumor cells using 'ROS-Based' therapies in CLL [95]. Treating CLL cells with Apolipoprotein E (ApoE) leads to lipid peroxidation and ferroptosis, supporting the idea of targeting ferroptosis as a therapy for CLL. Intracellular copper, which binds to this protein, regulates ApoE toxicity, possibly providing insight into how cuproptosis affects CLL [96].

Chronic myelogenous leukemia

Chronic myelogenous leukemia (CML) is a blood cancer resulting from the exchange of genetic material between Philadelphia chromosomes 9 and 22. The roles of ferroptosis and cuproptosis in CML have not been extensively researched.

Alterations in cellular iron metabolism and increased GPX4 expression are induced by BCR–ABL expression. DSF's ability to destabilize GPX4, increase the labile iron pool, and enhance lipid peroxidation results in ferroptotic cell death. The combination of DSF and TKIs successfully targets BCR–ABL + blast cells as well as drug-insensitive LSCs [97]. According to Wei et al. [98], hyperoside can induce ferroptotic cell death in CML by targeting the NRF2/SLC7A11/GPX4 pathway. Studies have also shown that reducing cysteine levels can trigger ferroptosis in CML cells in vitro, with thioredoxin reductase 1 (TXNRD1), linked to cellular redox metabolism, playing a crucial role in controlling ferroptosis [99]. Researchers in this study focused on leukemia cells, HeLa cells, and MEF cells, discovering that overexpressing SFXN3 led to a shortage of iron in the cytosol and an excess of Fe(II) in the mitochondria, making HeLa cells more susceptible to ferroptosis induced by RSL3 [100]. Sun et al. [101]. suggest that in mouse xenograft models, blocking both Trx1 and GCL leads to increased hydrogen peroxide and reduced GPX4 expression in CML cells, causing ferroptosis in cancer cells. At this time, investigations into ferroptosis and cuproptosis in leukemia are still in the beginning phases. We hope to incorporate more clinical studies in the future to thoroughly investigate their association, paving the way for innovative precision treatment ideas.

Conclusion and outlook

Ferroptosis and cuproptosis, newly discovered types of PCD, offer great promise for progress in cancer treatment. Our research has thoroughly clarified the connection between ferroptosis, cuproptosis, and leukemia, showing that these mechanisms are vital in the advancement of the disease. Recognizing ferroptosis and cuproptosis marks a crucial advancement in studying cell death processes. Cellular sensitivity to ferroptosis in blood cells can be affected by factors, such as PUFA–PL synthesis and peroxidation, intracellular ROS levels, and the balance of different metabolic pathways. Cuproptosis begins when copper ions directly interact with lipoylated elements of the TCA cycle, causing proteotoxic stress and resulting in cell death through cuproptosis. The experimental confirmation of cuproptosis in different cancer types is still mostly uncharted, with most current knowledge coming from bioinformatic studies. Specific mechanisms allow leukemia cells to escape oxidative stress. However, the study of ferroptosis and cuproptosis in leukemia is still in its early stages, one possible reason is that leukemia is an uncommon disease, requiring more research to clarify their exact mechanisms. Upcoming studies should aim to improve our understanding of the processes behind ferroptosis and cuproptosis, investigate their involvement in the onset, prognosis, and treatment resistance of leukemia and enhancing clinical efforts by overcoming leukemia's resistance to treatment. Investigating novel inhibitors targeting ferroptosis and cuproptosis, either alone or in combination with existing cytotoxic agents, could potentially augment the efficacy of current therapies, delay the onset of drug resistance, and improve patient prognosis. In the future, precision medicine will be essential. This context highlights the potential of nanomedicine as a promising development. Nanomaterials, because of their distinct physicochemical characteristics and biological roles, show significant potential in cancer treatment. The introduction of copper or iron-loaded nanomaterials has made it possible to precisely control copper or iron levels, turning it into a practical approach for managing tumor growth. Despite this, comprehensive studies on the two-way impact of copper or iron on tumor formation and the role of copper or iron-based nanomaterials in influencing tumor progression are still lacking.

In summary, the areas of ferroptosis and cuproptosis are currently experiencing a significant stage of growth. Nonetheless, there is a lack of extensive research investigating the impact of ferroptosis and cuproptosis inducers on leukemia treatment. We expect that future studies, using animal models and clinical trials, will reveal additional results. Considering the present research landscape, we highly recommend thorough studies on the relationship between ferroptosis, cuproptosis, and cancer. This research might provide new perspectives for diagnosing and treating blood cancers in a clinical setting. Innovative therapies targeting ferroptosis and cuproptosis are expected to be created and implemented in clinical settings shortly, with guidance from specific biomarkers and an accurate evaluation of a patient's history.

Abbreviations

AA

Arachidonic acid

ACD

Accidental cell death

AdA

Adrenic acid

AIF

Apoptosis-inducing factor

Apaf-1

Apoptosis protease-activating factor-1

ATOX1

Antioxidant 1

ATP7A

ATPase copper transporting alpha

ATP7B

ATPase copper transporting beta

BAP1

BRCA1-associated protein 1

CDN

Copper-depleting nanoparticle

CoA

Coenzyme A

CTR1

Copper transporter 1

Cu

Copper

Cyt c

Cytosolic cytochrome

DHODH

Dihydroorotate dehydrogenase

DLAT

Dihydrolipoamide S-acetyltransferase

Endo G

Endonuclease G

ES

Elesclomol

FDX1

Ferredoxin 1

FSP1

Ferroptosis suppressor protein 1

GPX4

Glutathione peroxidase 4

GSH

Glutathione

LA

Lipoic acid

LPCAT3

Lysophosphatidylcholine acyltransferase 3

LXA4

LipoxinA4

MT1/2

Metallothionein1/2

PCD

Programmed cell death

PE

Phosphatidylethanolamine

PGE2

Prostaglandin E2

PI

Proteasome inhibitor

PLOH

Phospholipid alcohol

PRDX6

Peroxiredoxin 6

PUFA–PLs

Polyunsaturated fatty acids-containing phospholipids

RCD

Regulated cell death

ROS

Reactive oxygen species

RTA

Radical-trapping antioxidant

SLC11A2

Solute carrier family 11 member 2

SLC31A1

Solute carrier family 31 member 1

SLC3A2

Solute carrier family 3 member 2

SLC7A11

Solute carrier family 7 member 11

STEAP

Six-transmembrane epithelial antigen of the prostate

System Xc-

Cystine glutamate transporter

TF

Transferrin

TFR1

Transferrin receptor 1

VCP

Valosin-containing protein

Author contributions

Zhe Chen: Study conception and design, drafting of article, critical review of article. Jieni Yu, Leihua Fu: Drafting of article and analysis and interpretation of data, Jiaping Fu, Drafting of article and analysis and interpretation of data, Zhijian Zhang, Drafting of article and analysis and interpretation of data, Pan Hong, Drafting of article and analysis and interpretation of data, Weiying Feng, Study conception, drafting of article and analysis and interpretation of data.

Funding

Sponsored by Zhejiang Provincial Natural Science Foundation of China (LBY23H080002), the Zhejiang Provincial Program for the Cultivation of High-level Innovative Health Talents.

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Competing interests

The authors declare no competing interests.