1 Head and Neck Surgery, The Third Affiliated Hospital of Kunming Medical University, 650118 Kunming, Yunnan, China
2 Medical School, Kunming University of Science and Technology, 650500 Kunming, Yunnan, China
†These authors contributed equally.
Abstract
Nasopharyngeal carcinoma (NPC) is a kind of malignant tumour originating from the mucosal epithelium of the nasopharynx, which has apparent regional distribution characteristics, and its incidence is increasing yearly. At present, the primary treatment method for nasopharyngeal carcinoma is radiotherapy, but radioresistance has become a complex problem to overcome to improve the therapeutic effect. Recently, ferroptosis has been proposed as a new type of iron-dependent programmed cell death, distinct from apoptosis, cell necrosis and autophagy. Many studies have shown that ferroptosis is involved in the occurrence, development, invasion and metastasis of nasopharyngeal carcinoma cells, and promoting the occurrence of ferroptosis of the same cells is a promising treatment method that should be written in the prospect. Therefore, this paper summarizes the mechanism of action of ferroptosis and its role in treating the same as above.
Keywords
- nasopharyngeal carcinoma
- ferroptosis
- treatment
- diagnosis
- prognosis
As mentioned above, nasopharyngeal carcinoma is a malignant tumour originating from the mucosal epithelium of the nasopharynx and often occurs in the pharyngeal recess. At present, its incidence is gradually on the rise [1]. Although the overall incidence of nasopharyngeal cancer is not high in the world, it is more common in some parts of Southeast Asia and North Africa, especially southern China [2]. The incidence of nasopharyngeal carcinoma may be related to genetics, Epstein-Barr virus infection, chronic nasopharyngeal infection for a long time and other factors [3]. Since most patients are diagnosed at an advanced stage and the current treatment strategies are difficult to achieve the expected therapeutic effect, early diagnosis and treatment of nasopharyngeal carcinoma can improve its survival rate [4]. At present, the treatment methods for nasopharyngeal carcinoma include radiotherapy, chemotherapy, surgery, biological therapy, etc. Radiotherapy is the main treatment method [5]. In recent years, it has been found that radioresistance can lead to local tumour recurrence, which is the main reason for the treatment failure of nasopharyngeal carcinoma [6]. Therefore, it is particularly significant to find advanced therapeutic method and directions to reduce the disease burden of nasopharyngeal carcinoma, improve patients’ standard of living, and provide a new scheme for the treatment of nasopharyngeal carcinoma. Ferroptosis treatment differs from the traditional treatment proposed in the New Year. Ferroptosis is a new type of cell death that has been proposed in recent years. Different from other classical programmed cell death modes, ferroptosis is regulated by iron content dependence and shows the main characteristics of death due to excessive accumulation of lipid peroxides, which has broad prospects in cancer treatment [7]. The study of ferroptosis in the treatment of nasopharyngeal carcinoma is still controversial. This paper reviews the relevant studies on the relationship between nasopharyngeal carcinoma and ferroptosis.
Nasopharyngeal carcinoma is a malignant tumor with low incidence and is affected by many factors. There are considerable regional differences in the incidence of nasopharyngeal carcinoma globally, among which is relatively high in Southeast Asia, North Africa, southern China and other regions. This is related to local eating habits, smoking rate and Epstein-Barr virus infection rate [8]. Long-term intake of unhealthy foods high in salt, oil and smoke can increase the risk of nasopharyngeal cancer. Long-term smoking and excessive alcohol consumption are major risk factors for nasopharyngeal cancer and can significantly increase the likelihood of developing the disease; Epstein-Barr virus (EBV) infection is considered to be an essential factor in nasopharyngeal carcinoma, especially in southern China. Family genetic predisposition may also increase the risk of nasopharyngeal cancer [9]. In general, various factors affect the incidence of nasopharyngeal cancer, including environmental factors, lifestyle, genetic factors, and so on; early detection and change of risk factors can reduce the risk of disease. China is one of the countries with the most significant number of nasopharyngeal cancer patients, and the incidence and mortality are higher than the global level. In recent years, the death rate of nasopharyngeal cancer among Chinese residents has decreased, but the incidence is still on the rise. With the aging of Chinese society, the disease burden of nasopharyngeal cancer will further increase, and it is urgent to formulate effective prevention and treatment programs [10].
According to the Union for International Cancer Control (UICC/American Joint Committee on Cancer/AJCC), TNM (Tumor - Lymph node - metastasis) staging The eighth edition of the staging system, which was updated in 2017, nasopharyngeal cancer is clinically divided into five stages, including stage 0, I, II, III and IV, of which stage IV includes stage IVA and stage IVB. Stage 0 is the primary tumour and cannot be evaluated. Stage I and II were confined to the nasopharynx and adjacent soft tissues (including parapharyngeal space, intralygoid muscle, and lateral pterygoid muscle), with or without a few proximal lymph node metastases. The boundary between stage III and stage III was mainly whether the nasopharyngeal cancer had bone invasion and destruction, including the skull base, cervical spine, pterygoid plate, paranasal sinuses, and cervical spine, and whether the lymph node metastases further expanded to bilateral cervical lymph nodes at the lower margin of cartilage. Stage IV developed distant metastases that further invaded the intracranial, cranial nerves, hypopharynx, orbit, parotid glands, and extensive soft tissues outside the lateral pterygoid muscle with or without it. According to the different scopes of tumour invasion and distant metastasis, it can be further divided into IVA and IVB stages, and the progression is gradually aggravated.
The early symptoms of nasopharyngeal carcinoma patients are not typical, and the individual differences are significant; it is not easy to pay attention to patients and doctors in the early stages of the tumour, and early detection and diagnosis are very difficult. In the areas with a high incidence of nasopharyngeal carcinoma, the overall situation presents the characteristics of high incidence, poor prognosis and low survival rate. More than 70% of nasopharyngeal carcinoma patients are in the advanced stage upon diagnosis, resulting in poor treatment effects and poor prognosis for most patients [11]. Therefore, given nasopharyngeal cancer, we should take adequate measures to achieve early detection, diagnosis, and treatment of the prevention and control effects. For people with high incidence, the commonly used early detection methods include nasal endoscopy, imaging examination and detection of Epstein-Barr (EB) virus-associated antigens and antibodies, which are quite significant for the early diagnosis of nasopharyngeal carcinoma [12]. Over the years, with the rapid development of medical imaging technology, computed tomography (CT) imaging technology, multi-modal magnetic resonance imaging (MRI) technology, and positron emission computed tomography (PET) technology, 99Tcm-HL91 anoxic imaging technology has been gradually widely used in the diagnosis and evaluation of the curative effect after treatment of nasopharyngeal carcinoma, providing solid help for the diagnosis and treatment of nasopharyngeal carcinoma patients. Pathological examination emphasizes the nasopharyngeal biopsy, which can be used as the gold standard for the diagnosis of nasopharyngeal carcinoma. Sometimes, clinical symptoms and imaging examinations support pathological diagnosis, but they do not. Immunohistochemistry or in situ hybridization can be used to assist in pathological biopsy for suspicious masses that cannot be biopsied, or the results are not ideal. Nasopharyngeal carcinoma cells are susceptible to ionizing radiation, so intensity-modulated radiotherapy (IMRT) is recommended for the treatment of non-metastatic nasopharyngeal carcinoma. In contrast, IMRT can be used for metastatic nasopharyngeal carcinoma. Tumor immunotherapy is also a promising therapeutic approach [1].
Ferroptosis is a novel form of programmed cell death through the process of phospholipid peroxidation, which relies on the metabolites reactive oxygen species (ROS), polyunsaturated fatty acid chain containing phospholipids (PUFA-PL), and transition metal iron and is affected by cell signal transduction to regulate cell metabolism and ROS levels [13]. Morphologically, unlike other classical cell death, ferroptosis does not show typical cell death features, such as nuclear and cytoplasmic changes and apoptotic body formation, but is characterized by mitochondrial atrophy and reduction in the number of mitochondrial cristae. Technologically, ferroptosis is characterized by the inability of antioxidant capacity to resist reactive lipid oxides, which leads to cell death, in contrast to other cell death mediated by cell death executive proteins [14]. Many cancer cells have expressed specific sensitivity to ferroptosis, including breast, pancreatic, lymphatic, and renal cancer cells [15]. It is worth mentioning that ferroptosis is inhibited in several cancer cells, such as breast cancer, thereby contributing to cancer cell proliferation and metastasis. Therefore, increasing the degree of ferroptosis in cells benefits chemotherapy and radiotherapy resistance [16]. An increasing number of signalling pathways, regulatory genes, and small molecule inducers have been demonstrated to achieve the therapeutic effect of cancer through the ferroptosis mechanism. For nasopharyngeal carcinoma, it has been clarified that the effects of inducers Erastin and sulfasalidine promote glutathione depletion [17], the related regulator p53 acts on Solute Carrier Family 7 Member 11 (SLC7A11) to cause the inhibition of cysteine-glutamate reverse transport system (Xc- system) [18], and miRNA regulates ferroptosis to affect the proliferation, invasion and differentiation of nasopharyngeal carcinoma cells [19]. Among them, it is worth noting that SLC7A11 is a solute transporter that participates in the extracellular uptake of cystine and glutamate release, promotes the synthesis of glutathione, protects cells from oxidative stress damage, and thus prevents cell death caused by lipid peroxidation, which plays a crucial role in ferroptosis [20]. Here, we discuss the possible therapeutic value and clinical significance of some regulatory factors and molecular inducers in nasopharyngeal carcinoma (NPC) cells (Table 1, Ref.[21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41], Table 2, Ref. [21, 22, 23, 24, 25, 26, 27, 28, 29, 32, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49]).
| Proteins/medicine/genes | Detection methods | Cohort size/subtype | Sample source | Ref |
| GSTM3 | qRT-PCR, western blot | tumor tissues (n = 36), normal tissues | Tissues | [26] |
| MIF | qRT-PCR, Immunohistochemistry, western blot | tumor tissues (n = 30), normal tissues | Tissues | [28] |
| ASCL4 | qRT-PCR, western blot | tumor tissues (n = 20), normal tissues | Tissues | [27] |
| PKC |
qRT-PCR, western blot | tumor tissues (n = 49), normal tissues | Tissues | [30] |
| SOD2 | western blot | - | Tissues | [35] |
| DHODH | western blot | - | Tissues | [34] |
| ATG5 | qRT-PCR | tumor tissues (n = 504), normal tissues (n = 44) | Tissues | [38] |
| P4HA1 | qRT-PCR, western blot | tumor tissues (n = 103), normal tissues (n = 6) | Tissues | [24] |
| CAPRIN2 | qRT-PCR, western blot | tumor tissues (n = 54), normal tissues (n = 59) | Tissues | [39] |
| SLC7A11 | qRT-PCR, western blot | tumor tissues (n = 6), normal tissues (n = 6) | Tissues | [40] |
| BBR | western blot, qRT-PC | - | Tissues | [21] |
| CuB | western blot | tumor tissues (n = 20), normal tissues | Tissues | [22] |
| Icaritin | western blot | tumor tissues (n = 24), normal tissues | Tissues | [23] |
| DSF/Cu | qRT-PCR, western blot | tumor tissues (n = 20), normal tissues | Tissues | [31] |
| Ent-halimane diterpenoid | qRT-PCR, western blot | tumor tissues, normal tissues | Tissues | [41] |
| MTDH | qRT-PCR, western blot | tumor tissues (n = 291), normal tissues | Tissues | [29] |
| HMOX1 | qRT-PCR, western blot | tumor tissues (n = 45), normal tissues | Tissues | [33] |
| lncRNAs | qRT-PCR, western blot | tumor tissues (n = 535), normal tissues (n = 59) | Tissues | [36, 37] |
| Others | Detection methods | Cohort size/subtype | Sample source | Ref |
| EVs | qRT-PCR | tumor tissues, normal tissues | Tissues | [32] |
| EBV | qRT-PCR, immunoblotting | tumor tissues (n = 181), normal tissues | Tissues | [25] |
GSTM3, Glutathione S-transferase mu 3; MIF, Macrophage migration inhibitory
factor; ACSL4, Acyl-CoA Synthetase Long Chain Family Member 4; PKC, protein
kinase; SOD2, Superoxide dismutase 2; DHODH, dihydroorate dehydrogenase; ATG5,
autophagy-related gene 5; P4HA1, Prolyl 4-hydroxylase; CAPRIN2, Caprin family
member 2; SLC7A11, Solute Carrier Family 7 Member 11; BBR, Berberine; CuB,
Cucurbatacin B; DSF, Disulfiram; MTDH, metadherin; HMOX1, heme
oxygenase 1; lnRNAs, long noncoding RNAs; EVs, extracellular vesicles; EBV,
Epstein-Barr virus; NPC, nasopharyngeal carcinoma; PKC
| Proteins/medicine/genes | Functions | Molecular mechanisms | Refs |
| GSTM3 | in vivo: ↓ tumor progrssion | USP14, FASN, GPX4 | [26] |
| MIF | in vivo: ↑ immune cell infiltration (TMB/TME/HLA), ↑ prolifera | JAB1/JNK, ERK, PI3K/Akt, p53 | [28] |
| ASCL4 | in vivo: ↓ prolifera/invasion/migration abilities | PUFA/Acyl-CoA | [27] |
| SOD2 | in vitro: ↓ tumor growth, ROS accumulation | ROS, ATP | [35] |
| DHODH | in vitro: ↓ tumor growth, ROS accumulation | GPX4, ROS | [34] |
| FTH1 | in vivo: ↓ prognostic survival | - | [46] |
| in vitro: ↑ tumor growth | |||
| FTO | in vivo: ↓ prognostic survival | OTUB1/SCL7A11 | [47] |
| in vitro: ↑radioresistance | |||
| ATG5 | in vitro: ↓ prognostic survival | PD-L1/PD-L2, G2M | [38] |
| P4HA1 | in vitro: ↑ tumor growth | MVA/HMGCR/HMGCS1 | [24] |
| CAPRIN2 | in vivo: ↑ prolifera/invasion/migration abilities | LINC00941/CAPRIN2/HMGCR | [39] |
| SLC7A11 | in vitro: ↑ tumor growth | MAPK, GSH, p38, ERK | [40] |
| in vivo: ↑ prolifera | |||
| BBR | in vivo: ↓ prolifera/invasion/migration abilities | HIF-1 |
[21] |
| CuB | in vitro: ↓ tumor growth, cell cycle progression | STAT3, Raf/MEK/ERK | [22] |
| in vivo: ↓ prolifera/invasion/migration abilities | |||
| Icaritin | in vitro: ↓ tumor growth, cell cycle progression | ROS, |
[23] |
| Cephalosporins | in vitro: ↓ tumor growth | ErbB-MAPK-p53, HMOX1 | [49] |
| in vivo: ↓ prolifera | |||
| Itraconazole | in vitro: ↓radioresistance | Fe, GSH, LPO | [48] |
| Isoquercetin | in vitro: ↓ tumor growth | NF-κB, AMPK, IL-1 |
[43, 44] |
| in vivo: ↓ prolifera/invasion/migration abilities | |||
| DSF/Cu | in vitro: ↑necroptosis | ROS, MAPK, p53, ROS-JNK | [42] |
| Lupeol | in vitro: ↑necroptosis | AMPK, p-IκB |
[45] |
| Ent-halimane diterpenoid | in vivo: ↓ prolifera/invasion/migration abilities | JAK2/STAT3 | [41] |
| MTDH | in vivo: ↑ prolifera/invasion/migration abilities | - | [29] |
| lncRNAs | in vivo: ↑ immune cell infiltration (TMB/TME/HLA) | - | [36, 37] |
| Others | Functions | Molecular mechanisms | Refs |
| EVs | in vivo: ↑ prolifera/invasion/migration abilities | ITGB3 and MAPK/ERK/ATF4/Nrf2 | [32] |
| EBV | in vivo: ↑ tumor progrssion | p62-Keap1-Nrf2/MAPK-JNK/NFκB | [25] |
↑ means the corresponding protein, gene, or medicine promotes a certain process, whereas ↓ represents inhibition/suppression. USP14, Ubiquitin-specific proteases14; FASN, Fatty acid synthase; GPX4,
Glutathione Peroxidase 4; JAB1, c-Jun activation domain binding protein-1; JNK,
c-Jun N-terminal kinase; ERK, extracellular regulated protein kinases; PI3K,
Phosphatidylinositide 3-kinases; Akt, protein kinase B; PUFA, polyunsaturated
fatty acid; Acyl-CoA, Acetyl-CoA; ATP, Adenosine triphosphate; OTUB1, OTU
Deubiquitinase, Ubiquitin Aldehyde Binding 1; PD-L1, Programmed cell death ligand
1; PD-L2, Programmed cell death ligand 2; ROS, Reactive oxygen species; FTH1,
Ferritin Heavy Chain 1; FTO, Fat mass and obesity-associated protein; MVA,
Mevalonate pathway; VEGF, vascular endothelial growth factor; STAT3, signal
transducer and activator of transcription 3; HMGCR, HMG-CoA reductase; GSH,
glutathione; ITGB3, Integrin Subunit Beta 3; ERK, extracellular regulated protein
kinases; HIF-1
Glutathione Peroxidase 4 (GPX4) is considered to be an essential regulator of ferroptosis and has the function of transforming lipid peroxides [50]. The ferroptosis propensity of cells is affected by the expression level of GPX4 in tumor cells, which in turn affects tumor progression by promoting radiation resistance and metastasis. High expression of GPX4 is associated with poor clinical outcomes in nasopharyngeal carcinoma and other cancer types. Currently, several well-studied and commonly used ferroptosis inducers, such as RAS synthetic lethal 3 (RSL3) and Sorafenib, are direct GPX4 inhibitors, which regulate the glutathione (GSH)/GPX4 axis to target cell ferroptosis. These drugs have shown great potential in cancer cell therapy [51, 52]. In addition, there are also newly identified ferroptosis inducers, such as Tubastatin A, which also acts on GPX4. However, the clinical therapeutic effects of cancer need to be further investigated [53]. Recently, many studies have tried to clarify the mechanism of action of some new drug-active molecules, cytokines, and gene loci on tumor progression by exploring the level of GPX4 expression, such as berberine (BBR), cucurbitacin B (CuB), icaritin, Glutathione S-transferase mu 3 (GSTM3), macrophage migration inhibitory factor (MIF), oncogene MTDH and so on (Fig. 1).
Fig. 1.
Possible mechanism of targeting Glutathione Peroxidase 4 (GPX4) pathway in the treatment of nasopharyngeal carcinoma. GSTM3, Glutathione S-transferase mu 3; IR, Ionizing radiation; GSSG, glutathione (oxidized form); GSH, glutathione; GPX4, Glutathione Peroxidase 4; BBR, berberine; CuB, cucurbitacin B; ROS, reactive oxygen species; MDTH, Methylenetetrahydromethanopterin dehydrogenase; MIF, migration inhibitory factor.
Berberine (BBR) is a natural isoquinoline alkaloid derived from protoberberine, which has various pharmacological effects, including the inhibition of distant metastasis of nasopharyngeal carcinoma cells. However, the mechanism is still unclear [21]. Recently, Wu et al. [54] suggested that BBR exerted its anti-metastatic effect on NPC by inhibiting the systemic Xc/GSH/GPX4 axis. BBR induces ferroptosis in nasopharyngeal carcinoma cells by increasing reactive oxygen species, lipid peroxidation, and iron content in cells and significantly inhibits the expression of GPX4, a key inhibitor of lipid peroxidation, at the protein and mRNA levels. At the same time, overexpression of GPX4 can reverse BBR induced ferroptosis [55].
Cucurbitacin B (CuB) is a tetracyclic triterpenoid natural product and active
ingredient in natural herbal medicine with an antitumor pharmacological effect
[22]. CuB was found to induce extensive lipid peroxidation, down-regulate GPX4
expression, and initiate ferroptosis. Alternatively, CuB showed antitumor effects
in vitro by inhibiting cell microtubule polymerization, arresting the
cell cycle, and inhibiting migration and invasion. In conclusion, CuB can be used
as a promising therapeutic agent for nasopharyngeal carcinoma by inducing
ferroptosis [56]. Icaritin is the active ingredient of the traditional Chinese
medicine Epimedium, which has inhibitory effects on a variety of tumor cells,
such as lung cancer, breast cancer, and ovarian cancer [57, 58, 59]. Studies have
shown that icaritin treatment can significantly promote reactive oxygen species
(ROS) production and Gamma H2AX (
Recently, it has been found that prolyl 4-hydroxylase (P4HA1) is a novel regulator of ferroptosis. PAHA1 protects NPC cells from ferroptosis inducer Erastin by activating 3-Hydroxy-3-Methylglutaryl-CoA Synthase 1 (HMGCS1), a key enzyme in the mevalonate pathway. The P4HA1/HMGCS1 axis promotes the proliferation of nasopharyngeal carcinoma cells in vitro. Knockdown of the P4HA1/HMGCS1 axis inhibited the xenograft growth of NPC cells and enhanced the inhibitory effect of Erastin on tumor growth. Up-regulation of the P4HA1/HMGCS1 axis promotes NPC cells’ resistance and survival rate to ferroptosis [24].
In addition to these drugs and genetic loci that can achieve therapeutic effects
through ferroptosis, Epstein-Barr Virus (EBV) has also been shown to achieve
ferroptosis escape mechanism of NPC through the SLC7A211-GPX4 pathway, resulting
in a worse prognosis of EBV-infected NPC. It is involved in the Nuclear erythroid
2-related factor 2 (Nrf2)/kelch-like ECH-associated protein 1 (Keap1) signaling
pathway. This signaling pathway plays a crucial role in cancerous and
non-cancerous cells, such as non-alcoholic liver disease and non-small cell lung
cancer. By over-activating the Nrf2/Keap1 pathway, cancer and non-cancer cells
enhance antioxidant defense mechanisms and regulatory cell death resistance,
thereby promoting their proliferation and survival [60, 61, 62]. EBV enhances the
resistance of NPC cells to ferroptosis by activating the p62-Keap1-NRF2
signaling pathway and increasing the expression of SLC7A11 and GPX4. GPX4 further
interacts with the transforming growth factor-
Glutathione S-transferase mu 3 (GSTM3), a member of the glutathione S-transferase family, plays a vital role in the progression of various malignant tumors [63]. Ionizing radiation (IR) promotes lipid peroxidation and induces ferroptosis in nasopharyngeal carcinoma cells. The expression of GSTM3 is increased after IR treatment, which is related to IR-induced ferroptosis and can reduce the radioresistance of nasopharyngeal carcinoma. Further studies have shown that GSTM3 inhibits ubiquitination and subsequent fatty acid synthase (FASN) decomposition by stabilizing ubiquitin-specific peptidase 14 (USP14), interacts with GPX4, inhibits GPX4 expression, and eventually leads to ferroptosis of cells to achieve radiosensitization (Tables 1,2) [26]. Macrophage migration inhibitory factor (MIF) is an inflammatory factor that inhibits macrophage migration and is involved in the progression of various cancers [27]. However, MIF tightly links various cells together in the tumour microenvironment (TME). It was found that GPX4 expression was decreased with inhibition of MIF function in M0, M1, or M2 macrophages. MIF is highly expressed in nasopharyngeal carcinoma cells. MIF secreted by nasopharyngeal carcinoma cells can be absorbed by macrophages, thereby inhibiting macrophage ferroptosis and promoting the metastasis of nasopharyngeal carcinoma [28].
The oncogene Metadherin (MTDH), also known as AEG-1, is considered an oncogene because of its association with promoting cancer progression, invasion and enhancing radioresistance [42, 64]. Recently, Cao et al. [29] constructed ferroptosis-related features, including IL6, NCF2, metadherin (MTDH), and CBS. MTDH, which promotes ferroptosis by inhibiting GPX4, has a very potent effect on ionizing radiation-induced ferroptosis, thereby increasing radiosensitivity, and has been identified as a potential therapeutic target for radioresistant HNSCC patients [29].
Excessive accumulation of lipid peroxides is the most important inducer of ferroptosis, which involves the regulation of many enzymes, including long-chain acyl-coa synthetase 4 (ACSL4) and lysophosphatidylcholine acyltransferase 3 (LPCAT3) (Fig. 2). ASCL4 is a lipid metabolic enzyme that can cause ROS accumulation leading to ferroptosis [27]. Photosynthesis microcapsules (PMCs), a novel ferroptosis inducer, directly lead to the excessive production of ROS by constructing a hyperoxic environment to achieve ferroptosis of tumour cells and achieve therapeutic effects [65]. The ferroptosis regulated by ACSL4 plays an essential role in the progression of nasopharyngeal carcinoma and is considered as a therapeutic target for ferroptosis induction [66]. ACSL4 inhibits cancer cell growth in NPC by ferroptosis and regulates tumour-associated macrophage (TAM) polarization. The expression level of ACSL4 is low in NPC patients and CNE-2 and 5-8F cells. Using ferroptosis inducers Erastin and ACSL4 increased lipid peroxidation, reduced cell viability, colony formation, cell proliferation, migration, and invasion, and inhibited epithelial-mesenchymal transition (EMT). In addition, Erastin and ACSL4 also promoted the polarization of M2 macrophages to M1 macrophages and inhibited the growth of cancer cells [55].
Fig. 2.
Possible mechansim of promoting lipid peroxide accumulation in ferroptosis in nasopharyngeal carcinoma. LPCAT3, lysophosphatidylcholine acyltransferase 3; ACSL 4, acyl-CoA synthetase long chain family member 4.
Protein kinase C (PKC), as a protein kinase, contains a variety of isoforms,
including
Isoquercetin (quercetin-3-O-
Disulfiram (DSF) is an anti-alcoholic drug that inhibits aldehyde dehydrogenase
and can even treat some cancers [67, 68]. DSF/Cu has a strong cytotoxic effect on
nasopharyngeal carcinoma cells, irreversibly reducing the activity of
nasopharyngeal carcinoma cells and promoting cell apoptosis and necrosis through
an aldehyde dehydrogenase (ALDH) independent pathway. In addition, DSF/Cu showed
anti-tumour activity on nasopharyngeal carcinoma cells by producing reactive
oxygen species (ROS), activating MAPK and p53 signalling pathways, and
mediating ferroptosis (Fig. 2). The combination of DSF/Cu with cisplatin could
significantly inhibit the growth of nasopharyngeal carcinoma tissues [31]. In
addition, lupeol significantly increased the phosphorylation of AMPK
Extracellular vesicles (EVs) are essential membrane-wrapped transport carriers
for transporting various cellular substances. A study has proved that
extracellular vesicles are involved in tumour progression, incredibly distant
metastasis [69]. Platelet-derived extracellular vesicles can inhibit ferroptosis
and promote distant metastasis of nasopharyngeal carcinoma by up-regulating the
integrin subunit
As mentioned above, radiotherapy remains the primary treatment for nasopharyngeal carcinoma, but overcoming radioresistance is essential for enhancing therapeutic outcomes [33]. Notably, ferroptosis plays a significant role in the radiosensitivity of nasopharyngeal carcinoma cells. Antioxidant enzymes that mitigate the accumulation of reactive oxygen species (ROS) or reduce phospholipids in the peroxidized membrane can effectively inhibit ferroptosis [71]. Two critical enzymes in this context are superoxide dismutase 2 (SOD2) and dihydroorotate dehydrogenase (DHODH) [34, 72]. When SOD2 is depleted, the balance of intracellular ROS is disrupted, resulting in an accumulation of superoxide that induces ferroptosis. This depletion also impairs the cells’ ability to form colonies in both ionizing and non-ionizing radiation settings.
In contrast, the DHODH inhibitor reduced the fluorescence intensity of malondialdehyde and oxidized C11 BODIPY, adenosine triphosphate (ATP) levels, and mitochondrial oxygen consumption (Tables 1,2). Cell viability and colony formation were also rescued. Therefore, SOD2 depletion can enhance the radiosensitivity of NPC cells, and the whole process is also regulated by DHODH inhibitors [35].
Recent research has indicated that elevated levels of ferritin heavy chain (FTH1) are linked to poor survival outcomes in head and neck squamous cell carcinomas (HNSCCs). Additionally, reducing FTH1 expression can enhance cell death in these cancers. FTH1 is a key component of ferritin, which is involved in regulating iron metabolism [46, 51]. In nasopharyngeal carcinoma cells (CNE-2), which exhibit high FTH1 levels and low epidermal growth factor receptor (EGFR) levels, there is a lack of sensitivity to ferroptosis induction and EGFR inhibition. The ferroptosis inducer RSL3 is combined with the EGFR monoclonal antibody cetuximab to disrupt cell survival, with FTH1 playing a critical role in this process [73]. N6-methyladenosine (m6A) is a prevalent modification of mRNA that influences gene expression within cells, and its dysregulation is associated with cancer. In tissues and cells of radiation-resistant nasopharyngeal carcinoma (NPC), the mRNA demethylase fat mass and obesity-associated protein (FTO) was found to be upregulated. FTO removes the m6A modification from the OTU deubiquitinase, ubiquitin aldehyde binding 1 (OTUB1) transcript, which subsequently enhances OTUB1 expression. This mechanism inhibits radiation-induced ferroptosis, ultimately contributing to the radioresistance observed in NPC. However, the FTO inhibitor FB23-2 and the ferroptosis activator Erastin modified the sensitivity of NPC cell lines and patient-derived xenografts to radiotherapy [47].
In addition to radiotherapy, chemotherapy alone or in combination is an additional therapeutic modality for NPC patients [74]. Anticancer antibiotics are considered an important chemotherapy modality. It has been reported that cephalosporin antibiotics can achieve a radiosensitizing effect by causing mitochondrial dysfunction and increasing intracellular ROS accumulation resulting in DNA damage. Research has demonstrated that cephalosporin antibiotics possess a highly specific and selective anticancer effect against nasopharyngeal carcinoma CNE2 cells, exhibiting lower toxicity. Cefotaxime sodium notably modulated 11 genes associated with cancer in CNE2 cells in a concentration-dependent manner. Notably, the apoptosis and ErbB-MAPK-p53 signaling pathways were significantly enriched, and the HMOX1 gene was markedly upregulated, leading to the induction of ferroptosis in nasopharyngeal carcinoma cells and enhancing radiosensitivity as a therapeutic outcome [49].
In addition to cephalosporin antibiotics, itraconazole also has some therapeutic
effects on NPC cells. Itraconazole is a triazole antifungal medication that
targets a crucial enzyme involved in the production of ergosterol—specifically,
lanosterol 14
It cannot be ignored that ferroptosis-related genes, regulators, lncRNAs, and metabolic markers are involved in the progression and prognosis of nasopharyngeal carcinoma, which provides an essential reference for the diagnosis and treatment of nasopharyngeal carcinoma. Among them, the relationship between ferroptosis-related genes (FRGs) and the prognosis of NPC still needs to be fully understood. A recent study has screened and identified some FRGs different from normal tissues in nasopharyngeal carcinoma tissues, including ABCC1, GLS2, CS, and HMG-CoA reductase (HMGCR) [79]. ABCC1 is involved in poor prognosis and radiosensitivity, GLS2 is involved in glutamine catabolism and is a direct target gene of P53. These mechanisms are involved in the ferroptosis process to varying degrees [36, 37]. These FRGs are associated with poor prognosis of NPC patients, which may be related to the regulation of the tumour microenvironment (TME) [79]. Other studies have shown that ATG5 is a critical ferroptosis-related gene in NPC cells. The expression level is high in nasopharyngeal carcinoma cells and is positively correlated with overall survival and the expression of programmed cell death ligand 1/programmed cell death ligand 2 (PD-L1/PD-L2). Patients with high ATG5 expression showed poor response and shorter survival after immune checkpoint blockade. In addition, ATG5 is closely related to the G2M checkpoint pathway, and patients with high ATG5 expression have a lower IC50 with G2M checkpoint inhibitor drugs. Therefore, ATG5 can be an essential target for treating ferroptosis in NPC cells [38].
Liu et al. [80] evaluated the ferroptosis regulation mode of nasopharyngeal carcinoma samples based on 113 ferroptosis regulators, identified three different ferroptosis subtypes, and used a Gaussian mixture finite model to make ferroptosis regulatory factor-related scoring system to predict the prognosis and immunotherapy effect of nasopharyngeal carcinoma. Subtypes 1 and 3 are consistent with the immune activation phenotype, which has the immune-activated tumour microenvironment (TME) phenotype and has better progression-free survival (PFS) and lower risk of recurrence and metastasis. However, subtype 2 is consistent with the immunosuppressive phenotype, and the tumour microenvironment phenotype is immunosuppressive with a poor survival rate [80].
Based on the biological information analysis of ferroptosis-related lncRNAs, Dai and Zhong [81] constructed a prediction model for the prognosis of nasopharyngeal carcinoma after clinical treatment. The researchers identified 14 differential long non-coding Rnas (lncrnas) associated with ferroptosis prognosis. These include ALOX15, ATP5MC3, CISD1, DPP4, FANCD2, GCLC, GLS2, GSS, SCL7A11, PHKG2, ACSL3, PEBP1, ABCC1 and PGD. Based on these findings, the prognostic model can effectively predict the prognosis of NPC patients. These ferroptosis-related lncrnas may be associated with the level of immune infiltration in model construction, suggesting their potential as therapeutic targets [81].
In the metabolomic study by Liao et al. [82], 1230 metabolites were found in serum and urine of NPC patients, of which 181 showed significant changes. These 181 metabolites were mainly concentrated in 16 metabolic pathways, including unsaturated fatty acid biosynthesis, cholesterol metabolism and ferroptosis. Among them, 179 metabolites were significantly changed, mainly involving 8 pathways, including tricarboxylic acid (TCA) cycle and caffeine metabolism. In addition, seven metabolites, such as creatinine and paraxanthine, were found to exhibit significant changes in both serum and urine samples. The changes of these metabolites provide important reference for the diagnosis and treatment of nasopharyngeal carcinoma [82].
Distant metastasis is the leading cause of death in patients with nasopharyngeal carcinoma, and inhibition of nasopharyngeal carcinoma cell proliferation and distant metastasis is an effective treatment [83]. Recently, a study has demonstrated that specific protein molecules and compounds exert undiscovered anticancer effects. In previous studies, Caprin family member 2 (CAPRIN2) was only shown to be an RNA-binding protein that plays a role in central defence and eye development [84]. Recently, CAPRIN2 was found to play a role in anti-ferroptosis and survival promotion in ECM-isolated NPC cells and is a positive regulator of migration and invasion of NPC cells. Under the upstream regulator LINC00941 regulation, CAPRIN2 is abnormally activated in NPC. HMGCR is a critical downstream molecule of CAPRIN2 and mediates CAPRIN2 regulation of ferroptosis, survival, migration, and invasion of NPC cells. Therefore, CAPRIN2/HMGCR can be a potential clinical therapeutic target for nasopharyngeal carcinoma cells (Tables 1,2) [39]. SLC7A11 is a transporter on the cell membrane and plays a vital role in glutathione synthesis [27]. NPC cells depend on SLC7A11 for cystine import for glutathione biosynthesis and maintenance of intracellular REDOX balance. Targeting SLC7A11 limits glutathione biosynthesis, leading to intracellular reactive oxygen species accumulation, lipid peroxidation, ferroptosis, and apoptosis. As a commonly used ferroptosis inducer, elastin can induce ferroptosis in various ways, including inhibiting SLC7A11 and GSH depletion [17]. Moreover, targeting SLC7A11 altered the cellular mitogen-activated protein kinase pathway, including activation of p38 and inhibition of extracellular regulated protein kinases (ERK), limiting the proliferation of NPC cells [40].
Wang et al. [41] discovered an enhalane diterpenoid that exhibits sensitivity in CNE cells. This compound inhibits the activation of the JAK2/STAT3 signaling pathway by binding to Gln326 of STAT3 in CNE cells, thereby reducing cell migration, invasion, and epithelial-mesenchymal transition. Additionally, it induces ferroptosis in CNE cells in a dose-dependent manner [41].
Ferroptosis is a novel cell death mode characterized by the structural damage of the cell membrane caused by uncontrolled lipid peroxidation, which is influenced by the content of reactive oxygen species, lipid peroxidation level, antioxidant system and transcription factors. Changes in the metabolism of nasopharyngeal carcinoma cells and disruption of the REDOX balance increase their dependence on antioxidants, making nasopharyngeal carcinoma cells vulnerable to ferroptosis induction. With the deepening of the research, it is found that ferroptosis plays an essential role in the progression of nasopharyngeal carcinoma. However, the research on tumour immunity still needs to be made more explicit. Although the relationship between the two has not been fully revealed, the mechanism of ferroptosis is an excellent direction to apply in clinical treatment. Targeted therapy of ferroptosis, in particular, would offer a potentially practical approach to the limitations of current therapies. There are a few examples of Ferroptosis-related therapy used to treat nasopharyngeal cancer. In the future, we can develop targeted drugs related to ferroptosis in clinical work and study the crosstalk between ferroptosis and other types of cell death. Furthermore, in nasopharyngeal cancer, FRGs are associated with ferroptosis sensitivity and are involved in the progression and prognosis of nasopharyngeal cancer, which provides potential directions for precision medicine strategies.
RH and XL designed the research study. TL and FL performed the research. ZS and JY provided help and advice on acquiring and analyzing literature. RH and TL wrote the manuscript. EF and XY collected and sorted references. YR designed and drew the figures and tables. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.
Not applicable.
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(1) Regional Project of National Natural Science Foundation of China in 2022 (82260485). (2) Yunnan Province “Ten Thousand People Plan” Famous Medical Talents Special Project (YNWR-MY-2019-030). (3) Yunnan Province “Ten Thousand People Plan” Young Top Talent Special Project (YNWR-QNBJ-2019-056). (4) Basic Research Project of Science and Technology Department of Yunnan Province in 2020 (202001AT070056).
The authors declare no conflict of interest.
References
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