Induction of ferroptosis by natural products in non-small cell lung cancer: a comprehensive systematic review

Lung cancer is one of the leading causes of cancer-related deaths worldwide that presents a substantial peril to human health. Non-Small Cell Lung Cancer (NSCLC) is a main subtype of lung cancer with heightened metastasis and invasion ability. The predominant treatment approaches currently comprise surgical interventions, chemotherapy regimens, and radiotherapeutic procedures. However, it poses significant clinical challenges due to its tumor heterogeneity and drug resistance, resulting in diminished patient survival rates. Therefore, the development of novel treatment strategies for NSCLC is necessary. Ferroptosis was characterized by iron-dependent lipid peroxidation and the accumulation of lipid reactive oxygen species (ROS), leading to oxidative damage of cells and eventually cell death. An increasing number of studies have found that exploiting the induction of ferroptosis may be a potential therapeutic approach in NSCLC. Recent investigations have underscored the remarkable potential of natural products in the cancer treatment, owing to their potent activity and high safety profiles. Notably, accumulating evidences have shown that targeting ferroptosis through natural compounds as a novel strategy for combating NSCLC holds considerable promise. Nevertheless, the existing literature on comprehensive reviews elucidating the role of natural products inducing the ferroptosis for NSCLC therapy remains relatively sparse. In order to furnish a valuable reference and support for the identification of natural products inducing ferroptosis in anti-NSCLC therapeutics, this article provided a comprehensive review explaining the mechanisms by which natural products selectively target ferroptosis and modulate the pathogenesis of NSCLC.


Introduction
According to the latest data from the Global Cancer Observatory (GCO) (Cancer Today (iarc.fr)), in 2020, lung cancer ranked as the third most common cancer globally, with an incidence rate of approximately 22.4 cases per 100,000 population and a mortality rate of around 18% per 100,000 population (Sung et al., 2021) (Figure 1).Non-Small Cell Lung Cancer (NSCLC) represents the predominant subtype of lung cancer, accounting for approximately 85% of cases, and it is characterized by a poor prognosis, with a 5-year survival rate of only 19% (Rodríguez-Abreu et al., 2021;Mithoowani and Febbraro, 2022).Over the past few decades, various treatment modalities, including surgery, chemotherapy, radiation therapy, targeted therapy, and immunotherapy, have been employed in the clinical management of NSCLC (Hopstaken et al., 2021;Miller and Hanna, 2021;Wang et al., 2021;Alduais et al., 2023).Despite the significant advances achieved for these treatment strategies, the development of therapy resistance in NSCLC remains a considerable challenge (Brown et al., 2019;Patel and Weiss, 2020;Muthusamy et al., 2022), thus necessitating the exploration of novel therapeutic approaches for NSCLC.
Ferroptosis is a novel form of programmed cell death (PCD) that has been recently discovered and differs morphologically, biochemically, and genetically from apoptosis, autophagy, and necrotic (Mou et al., 2019;Chen et al., 2021b;Yuan et al., 2021).The presence of ferroptosis in cells is commonly linked to the accumulation of iron, disturbances in fatty acid metabolism, and lipid peroxidation (Ursini and Maiorino, 2020;Xu et al., 2021;Yao et al., 2021), which play crucial roles in initiating ferroptosis (Li and Li, 2020;Zhang et al., 2022).Previous studies have highlighted the significant role of ferroptosis in the pathogenesis of NSCLC, suggesting ferroptosis maybe a potential and novel approach for NSCLC treatment (Liu et al., 2021;Liu et al., 2022).The mediators or signal pathways regarding to ferroptosis in the pathological progression of NSCLC were presented in Table 1.
In recent years, natural products from traditional herbal medicine have emerged as an increasingly important therapy in the prevention and treatment of NSCLC (Zhang et al., 2018;Wan et al., 2019;Li et al., 2021).Furthermore, there is a growing body of research focusing on the modulation of ferroptosis by natural products for the prevention and treatment of NSCLC (Batbold and Liu, 2021).This article discusses the molecular mechanisms underlying ferroptosis and highlights the mechanisms by which different types of natural products induce ferroptosis to exert anti-cancer effects on NSCLC.The aim is to further provide theoretical support for drug development and treatment strategies in NSCLC.

Mechanism of ferroptosis
Ferroptosis represents a distinct form of cell death, which was first proposed by Dixon et al., in 2012(Dixon et al., 2012).Morphologically, ferroptosis is characterized by mitochondrial shrinkage, mitochondrial membrane rupture, increased membrane density, and reduced or vanished mitochondrial cristae (Xie et al., 2016).Biochemically, lipid peroxidation, iron metabolism, redox homeostasis and fatty acid supply are currently thought to be pivotal to the induction of ferroptosis.(Li et al., 2020;Chen et al., 2021c).The following part provides an overview of the extensively studied mechanisms underlying ferroptosis (Figure 2).
2.1 Inhibition of the cysteine-glutamate transporter system Xc − induces ferroptosis It is composed of two subunits: the light chain, known as xCT (SLC7A11), and the heavy chain, known as solute carrier family 3 member 2 (SLC3A2) (Tu et al., 2021).xCT is responsible for the transport of cystine (oxidized form of cysteine) into the cell, while SLC3A2 acts as a chaperone and stabilizes the expression of xCT on the cell surface (Wang et al., 2022).The function of system Xc -is to transport cystine into the cell in exchange for glutamate (Glu) export.Cystine is a disulfide form of the cysteine, which is essential for the synthesis of the antioxidant GSH.GSH helps to neutralize reactive oxygen species (ROS) and protects cells from oxidative damage (Albrecht et al., 2010).In the context of ferroptosis, system Xc -plays a central role in maintaining intracellular redox homeostasis.It imports cystine into the cell, which is subsequently reduced to cysteine.By promoting the availability of cystine, system Xc -supports the synthesis of GSH by catalyzing glutathione synthetase (GSS) and glycine (Gly).Throughout this process, GSH undergoes oxidation to form oxidized glutathione (GSSG).However, GSSG is subsequently converted back to its reduced form, GSH, with the assistance of an enzyme called glutathione reductase (GR).Therefore, inhibition or genetic depletion of system Xc -leads to impaired cystine uptake, reduced GSH synthesis, and increased vulnerability to lipid peroxidation, ultimately promoting ferroptosis (Li F. J. et al., 2022).

Inhibition of GPX4 induce ferroptosis
GPX4, a crucial antioxidant enzyme predominantly localized within cellular organelle membranes, plays a significant role in the elimination of lipid peroxides (Miao et al., 2022).Specifically, it exhibits the capacity to catalyze the reaction between GSH and lipid peroxidation during the process of ferroptosis.This enzyme facilitates the reduction of lipid peroxidation into benign alcohol forms, thereby impeding the buildup of lipid peroxidation (Sui et al., 2018).However, under conditions of inadequate intracellular GSH levels, the functionality of GPX4 becomes hindered, impeding the effective clearance of lipid peroxidation (Xu et al., 2021).During ferroptosis, the inhibition of system Xc -leads to a reduction in GSH Regulatory mechanism of ferroptosis.General mechanism of ferroptosis associated with System Xc − , GPX4, accumulation of iron, and lipid peroxidation.
synthesis, diminishes the substrate availability for GPX4 and reduces the elimination of lipid peroxidation, ultimately provokes the initiation of ferroptosis (Seibt et al., 2019).

Accumulation of iron
Iron is an essential bio-element within cells, participating in various physiological processes, including oxygen transport (Lipper et al., 2019), DNA synthesis (Lane et al., 2015), and energy production (Hentze et al., 2004).Under certain conditions, iron can also act as catalysts for cell death, promoting the occurrence of ferroptosis (Ma et al., 2022;Anandhan et al., 2023).Ferric ions (Fe 3+ ) are imported into the cell from the extracellular space through their binding to transferrin (TF), forming the complex "TF-Fe 3+ -TfR1" with transferrin receptor 1 (TfR1) (Hadzhieva et al., 2014;Basuli et al., 2017).This process involving TF and TfR1 is crucial for the intracellular accumulation of lipid peroxides and the occurrence of ferroptosis.Within the endosome, Fe 3+ are converted to ferrous ions (Fe 2+ ) by ferric reductases such as STEAP3 metalloreductase (Ye et al., 2022).Subsequently, Fe 2+ are transported from the endosome to the labile iron pool (LIP) via the divalent metal transporter 1 (DMT1) (Aschner et al., 2022).In the cytosol, Fe 2+ reacts with hydrogen peroxide (H 2 O 2 ) through the Fenton reaction, leading to lipid peroxidation and the generation of ROS (Liu et al., 2022).Importantly, various cellular processes that influence iron uptake, storage, utilization, and release can impact cell sensitivity to ferroptosis.For instance, the degradation of ferritin induced by nuclear receptor coactivator 4 (NCOA4) also contributes to ferroptosis promotion (Santana-Codina et al., 2021).Conversely, reduced expression of solute carrier family 40 member 1 (SLC40A1) may result in intracellular Fe 2+ accumulation, subsequently increase irondependent oxidative stress and facilitate ferroptosis (Hao et al., 2021).

Lipid peroxidation
Lipid metabolism plays a vital role in the occurrence of ferroptosis, which is characterized by the accumulation of lipid peroxides resulting from the oxidation of polyunsaturated fatty acids (PUFAs), a class of fatty acids characterized by the presence of multiple double bonds, including omega-3 and omega-6 fatty acids (Christie and Harwood, 2020), which plays essential roles in the composition of cell membranes and participate in numerous physiological processes within cells (Wiktorowska-Owczarek et al., 2015).During the process of lipid peroxidation, several enzymes involved in lipid metabolism act as positive regulators of ferroptosis.One such enzyme is Acyl-CoA synthetase long chain family member 4 (ACSL4), which participates in phospholipid metabolism and facilitates the synthesis of PUFA-CoA from PUFAs like arachidonoyl (AA) and adrenal (AdA), thereby activating PUFAs (Doll et al., 2017).Following ACSL4-driven esterification, lysophosphatidic transferase 3 (LPCAT3) incorporates PUFAs into phospholipids, forming phospholipids containing PUFAs (Reed et al., 2022).Subsequently, ALOX15 oxidizes these PUFA-PLs, generating lipid peroxides and ultimately leading to ferroptosis (Ma et al., 2022).

Others
Ferroptosis can also be regulated by several another protein.
Recent publications are summarized in Table 2.

Natural products modulating ferroptosis for intervention in NSCLC
Natural products possess multiple pharmacological activities, particular in the treatment of tumors.Recently, researchers have identified certain natural products that can modulate ferroptosis to exert anti-tumor potential (Yang et al., 2022).Figure 3 provides a compilation of natural products with their sources and chemical formulas, which induce ferroptosis to treat NSCLC.The regulatory targets and mechanisms of these natural products are illustrated in Figure 4 and presented in Table 3.

Timosaponin AIII
Timosaponin AIII(TA III) is a steroidal saponin and major active component derived from the traditional Chinese medicinal herb Schisandra chinensis (Wang et al., 2023).Timosaponin AIII exhibits various pharmacological activities, including antiinflammatory (Yuan et al., 2016), anti-oxidant (Jiang et al., 2014), and anti-cancer effects (Chien et al., 2022).Zhou (Zhou et al., 2023) discovered that Timosaponin AIII can inhibit the proliferation and migration of NSCLC cells, induce cell cycle arrest at the G2/M phase, and trigger ROS release and iron accumulation.This process is accompanied by the generation of malondialdehyde (MDA) and the depletion of GSH.Furthermore, it was confirmed that heat shock protein 90 (HSP90) is a direct target of Timosaponin AIII.Timosaponin AIII forms a complex with HSP90, leading to the ubiquitination and degradation of GPX4, ultimately inducing ferroptosis.This study confirms that Timosaponin AIII can play a therapeutic role in NSCLC by inducing ferroptosis.

Curcumin
Curcumin is a naturally occurring compound derived from turmeric (Anand et al., 2007).The curcumin possesses pharmacological properties such as immunomodulation (Gautam et al., 2007), anti-inflammatory (Peng et al., 2021), and anti-cancer activity (Gouda and Bhandary, 2019).In a study conducted by Tang (Tang et al., 2021), characteristic changes associated with ferroptosis were observed in response to curcumin treatment in NSCLC cells.These changes included increased intracellular accumulation of iron and MDA, depletion of GSH, downregulation of SLC7A11 and GPX4 protein levels, negative regulators of ferroptosis, accumulation of lipid peroxidation, curcumin-induced mitochondrial membrane rupture, and reduction of mitochondrial cristae.Furthermore, the curcumin-treated group exhibited increased accumulation of autolysosomes, along with elevated levels of autophagy biomarkers, such as Beclin1 and microtubule-associated protein 1 light chain 3 alpha (LC3).The study also demonstrated that the characteristic changes of ferroptosis were partially reversed when the curcumin-treated NSCLC cells group was treated with CQ (an inhibitor of autophagosome-lysosome fusion) or when the Beclin1 was silenced.In summary, these findings suggest that autophagy contributes to curcumin-induced ferroptosis in NSCLC cells, and inhibiting autophagy can alleviate cellular sensitivity to ferroptosis.

Sanguinarine
Sanguinarine is a natural small-molecule compound isolated from the bloodroot plant (Lou et al., 2021), which possesses antibacterial (Zhang et al., 2020), anti-inflammatory (Niu et al., 2012), and anti-cancer properties (Gaziano et al., 2016).Xu (Xu et al., 2022).conducted a study and found that sanguinarine inhibited the proliferation of NSCLC cells in a dose-dependent and timedependent manner.In xenograft tumor animal models, sanguinarine effectively suppressed the growth and metastasis of NSCLC cells.Furthermore, it was discovered that sanguinarine induced intracellular accumulation of iron, increased levels of ROS and MDA, and reduced GSH levels.Sanguinarine mediated the ubiquitination and degradation of GPX4 through stress induced phosphoprotein 1 (STIP1) and U-Box containing protein 1 (Stub1), thereby triggering ferroptosis in NSCLC cells.Furthermore, overexpression of GPX4 partially restored the proliferative and invasive inhibitory effects of sanguinarine on NSCLC cells by suppressing ferroptosis.In conclusion, sanguinarine inhibits the growth and metastasis of NSCLC cells by regulating the Stub1/GPX4-dependent iron-dependent cell death pathway.

Erianin
Erianin, a natural benzylisoquinoline compound extracted from Dendrobium (Li et al., 2023), exhibits anti-cancer activity by inhibiting cell proliferation, inducing apoptosis (Xu et al., 2021), and autophagy (Chen et al., 2020) in various cancers such as cervical cancer (Li et al., 2018), colorectal cancer (Miao et al., 2023), prostate cancer (Trapika et al., 2021), and breast cancer (Xie et al., 2021).Chen (Chen et al., 2020) found that erianin arrested NSCLC cells in the G2/M phase, thereby inhibiting cell proliferation and metastasis.Further investigations revealed that erianin treatment induced accumulation of ROS, consumption of GSH, and occurrence of lipid peroxidation in NSCLC cells.However, the results were reversed by ferroptosis inhibitor.Calmodulin (CaM), a major endogenous calciumregulating protein, plays a crucial role in regulating L-type voltagedependent calcium channels, which are important for calcium and iron transport (Zeng et al., 2023).This study confirmed that erianin targeted the CaM signaling pathway, leading to ROS accumulation and upregulation of iron by modulating the calcium-CaM pathway, thereby inducing ferroptosis in NSCLC cells.

Ginkgetin
Ginkgetin is a natural flavonoid compound derived from the Ginkgo biloba.It exhibits pharmacological activities such as neuroprotection (Singh et al., 2019), cardiovascular protection (Silva and Martins, 2022), anti-oxidant (Li et al., 2022d), and anti-inflammatory effects (Li et al., 2022b).Additionally, research has shown that it exerts anti-cancer effects by inhibiting cell proliferation, angiogenesis, and inducing apoptosis in tumor cells (DeFeudis et al., 2003;Ye et al., 2007;Bai et al., 2015;Han et al., 2016;Kim et al., 2021).Lou (Lou J. S. et al., 2021) conducted a study and found that the combination of Ginkgetin with cisplatin enhanced the cytotoxicity against NSCLC cells.This combination treatment increasesthe accumulation of iron and the occurrence of lipid peroxidation.Further investigations revealed that Ginkgetin reduced the expression of SLC7A11 and GPX4, decreased the GSH/GSSG ratio, increased ROS formation, and reduced the activity of the Nrf-2/HO-1 signaling pathway.These actions collectively induced ferroptosis in NSCLC cells.These results

FIGURE 4
The mechanism of natural products inducing ferroptosis in NSCLC.The activation of ROS or the inhibition of GPX4, GSH, SLC7A11 and transferrin by different natural products can induce ferroptosis to treat NSCLC.
suggest that the combination of Ginkgetin and cisplatin reduces NSCLC development by inducing ferroptosis.

Hederin
Hederin belongs to a class of saponin compounds found in the Ginkgo biloba plant, which belongs to the family Ginkgoaceae (Jeong et al., 2019).Numerous studies have indicated that α-Hederin has anti-tumor functions (Belmehdi et al., 2023).For instance, in colorectal cancer cells (Sun et al., 2019), α-Hederin inhibits the epithelial-mesenchymal transition induced by interleukin-6 and the activity of the JAK2/STAT3 signaling pathway, thereby suppressing cell migration and invasion.In gastric cancer cells (Wang et al., 2020), the combination of α-Hederin and cisplatin promotes apoptosis in gastric cancer cells through mitochondria-related apoptotic pathways.Wu (Wu et al., 2022) discovered that α-Hederin inhibits the proliferation and invasion of NSCLC cells in a dose-dependent manner both in vitro and in vivo.Subsequent proteomics, metabolomics, and high-throughput sequencing confirmed that α-Hederin treatment reduces the expression of GSH peroxidase 2 (GPX2) and GSS, inhibits the synthesis of GSH, disrupts the GSH redox system.After the administration of the ferroptosis inhibitor of ferrostatin-1, the study observed a partial restoration of α-Hederin-induced cell death.Meanwhile, ferrostatin-1 treatment recovered α-Hederin-induced disturbance in mitochondrial membrane potential.In summary, α-Hederin could induces ferroptosis in the treatment of NSCLC.

Dihydroisotanshinone I
Dihydroisotanshinone I (DTI), a diterpenoid compound belonging to the tanshinone class, is extracted from the medicinal herb Salvia miltiorrhiza (Hsu et al., 2021).Salvia miltiorrhiza has been widely used in traditional Chinese medicine and possess diverse pharmacological activities and therapeutic potential (XD et al., 2019;He et al., 2024).Research studies have demonstrated that DTIDTI exhibits anti-oxidant (Ip et al., 2002), and anti-cancer properties (Wu et al., 2017;Lin et al.,  2019).Wu (Wu et al., 2021)have shown that DTI inhibits the growth of A549 cells and H460 cells via inducing ferroptosis.The underlying mechanism involves the downregulation of GPX4 protein and GSH levels, accumulation of MDA,ROS, leading toand lipid peroxidation and finally induction of ferroptosis in NSCLC.

Sulforaphane
Sulforaphane belongs to the class of compounds known as isothiocyanates and is predominantly found in vegetables of the Brassicaceae family, particularly in cruciferous vegetables such as cauliflower, cabbage, and broccoli (Vanduchova et al., 2019).Extensive research has demonstrated that sulforaphane exerts its beneficial effects through multiple mechanisms, including the activation of intracellular antioxidant enzymes (Ishida et al., 2021), modulation of cellular signaling pathways (Zhang et al., 2022c), and anti-cancer activities (Russo et al., 2018).Studies conducted by Yuko Iida (Iida et al., 2021) have shown that sulforaphane significantly inhibits the growth of NSCLC cells, and this growth inhibition can be reversed by ferroptosis inhibitors offerrostatin-1.Furthermore, treatment of NSCLC cells with sulforaphane leads to an increase in iron and ROS levels, as well as collection of lipid peroxidation products, all of which can be attenuated by ferroptosis inhibitors.Subsequent investigations revealed that sulforaphane specifically downregulates the expression of the SLC7A11, resulting in a reduction in GSH accumulation.Collectively, Sulforaphane inhibits the growth of NSCLC cells via inducing ferroptosis.

Cryptotanshinone
Cryptotanshinone (CTN) is a diterpenoid monomer and a lipophilic component extracted from the dried roots and rhizomes of the traditional Chinese herb S. miltiorrhiza (Li et al., 2021;Zhang et al., 2023).CTN has been proven to possess various biological activities, including antioxidant (Guo et al., 2022), anti-tumor (Dalil et al., 2022), antibacterial (Zhong et al., 2021), and anti-inflammatory effects (Wu et al., 2020).Li (Popa et al., 2021) discovered that CTN effectively suppresses NSCLC cells invasion, proliferation and tumorigenesis.The treatment of CTN resulted in increased iron accumulation within the cells and decreased the expression levelof GPX4 protein.Furthermore, CTN elicited an upregulation of Cytoglobin, a protein known to induce ferroptosis, while downregulats ferroportin expression.Moreover, study demonstrated that CTN induces iron-dependent lipid peroxidation by inhibiting the function of TfR1.These data suggest that the induction of ferroptosis in NSCLC cells, achieved by increasing iron accumulation, Cytoglobin, and iron-dependent lipid peroxidation, or by downregulating the expression levels of ferroportin and GPX4, may be an important mechanism through which CTN attenuates NSCLC.

Artemisinin
Artemisinin is a sesquiterpene lactone isolated from the Artemisia annual (Ma et al., 2020).It is widely used for the treatment of malaria (Talman et al., 2019).Apart from its wellknown role in treating malaria, artemisinin has been reported in numerous studies to possess additional pharmacological activities, including anti-schistosomiasis (Pérez del Villar et al., 2012),anticancer (Kiani et al., 2020),anti-inflammation (Yuan et al., 2019),anti-virus (Wani et al., 2021).Zhang (Zhang et al., 2021) discovered that artemisinin downregulates the protein and mRNA levels of xCT.Furthermore, artemisinin upregulates the mRNA level of TfR1, Therefore, Zhang hypothesis that Artemisinin may induces ferroptosis in NSCLC.Consequently, the cell death caused by artemisinin can be partially reversed by N-Acetyl-L-cysteine (NAC), a ROS scavenger, and ferrostatin-1, a ferroptosis inhibitor.The findings demonstrate that the inhibitory effect of artemisinin on NSCLC cells is at least partially attributed to the induction of ferroptosis.

Sinapine
Sinapine belongs to the class of compounds known as phenethylamines particularly in abundance in sources such as barley, mustard seeds, peas, and rapeseeds (Dang et al., 2023).It exhibits numerous pharmacological activities, such like antioxidant (Yates et al., 2019), anti-inflammatory (Li et al., 2019), and anti-cancer activities (Guo et al., 2014).In the realm of cancer research, Sinapine has shown promise as an anti-cancer agent, displaying inhibitory effects on various cancer cells, including breast cancer (Guo et al., 2016) and colorectal cancer (Yang et al., 2023).Notably, Shao (Shao et al., 2022) found that Sinapine play the anti-tumor effects on NSCLC cells.Induce ferroptosis by increasing intracellular ferrous iron, lipid peroxidation, and ROS in NSCLC cells.Also, treatment with Sinapine upregulates transferrin and transferrin receptor, and inhibits either of them attenuated the ferroptosis induced by Sinapine.Additionally, Sinapine treatment led to a p53-dependent downregulation of SLC7A11.Furthermore, Sinapine also play the inhibition role in the growth of NSCLC in vivo.In conclusion, the findings highlight that Sinapine could be a promising therapeutic approach via triggers ferroptosis in NSCLC.

Dihydroartemisinin
Dihydroartemisinin (DHA) is a derivative of artemisinin, which is a compound extracted from the Artemisia annua plant (Dai et al., 2021).DHA exhibits its antimalarial activity by rapidly and effectively clearing the malaria parasite from the bloodstream (Hanboonkunupakarn and White, 2022).In addition to its antimalarial properties, DHA has been demonstrated antiinflammatory (Yang et al., 2022),anti-cancer (Bai et al., 2021) and immunomodulatory (Gao et al., 2020) properties.In DNA replication, the protein encoded by the DNA primase subunit 2 (PRIM2) gene plays a critical role.PRIM2 functions by catalyzing the synthesis of RNA primers, which act as the starting points for DNA synthesis (Wei and Lozano-Durán, 2023).Yuan's study (Yuan et al., 2020) revealed that DHA reduced the expression of PRIM2, and silencing PRIM2 mimicked the inhibitory effects of DHA on cell proliferation and colony formation, while promoting cell death in NCSLC cells.Additionally, the study found that DHA treatment and the absence of PRIM2 led to a series of ferroptosis characteristic in NSCLC cells.Mechanistically, the combination of DHA treatment and the absence of PRIM2 decrease the level of GSH, increasecellular lipid ROS and MDA levels, as well as downregulats SLC7A11 and βcatenin expressions in NCSLC cells.

Celastrol
Celastrol is a prominent bioactive compound extracted from the root bark of Tripterygium wilfordii, a plant belonging to the Celastraceae family (Xu et al., 2021).It falls within the class of pentacyclic triterpenoids, possessing a triterpene framework and exhibiting noteworthy biological activity (Li et al., 2022f), such like anti-cancer (Xu et al., 2023), anti-inflammatory effect in liver fibrosis (Wang et al., 2020), and potential pharmacological treatment of obesity (Liu et al., 2015).In a study conducted by Liu (Liu et al., 2021), it was observed that the combination of erastin,a ferroptosis inducer, and celastrol induced cell death in NSCLC cells at concentrations that were not toxic individually.The co-treatment with celastrol and erastin resulted in promotion of ROS generation, disturbance of mitochondrial membrane potential, augmentation of the interaction between dynamin-related protein 1 (DRP1) and mitochondrial fission, mitochondrial 1 (FIS1), and stimulation of mitochondrial fission.Of these, the above results suggest that Celastrol may be a natural compound that effectively induces ferroptosis.

Betulin
Betulin is a natural triterpene compound that occurs in the bark of specific tree species, including white and silver birch trees (Demets et al., 2022).The emerging evidence has shown that Betulinpossesses various advantageous properties, including anti-inflammatory (Tuli et al., 2021), anti-oxidant (Günther et al., 2021), and anti-cancer (Wang et al., 2017).Yan (Yan et al., 2022) found that betulin in combination with Gefitinib exhibited antagonistic effects on cellular viability on NSCLC cells of A549 and H460.However, the ferroptosis inhibitors of ferrostatin-1, liproxstatin-1 and deferoxamine can completely rescue the viability of A549 and H460 after treatment of betulin in combination with Gefitinib.Moreover, in order to confirm whether ferroptosis contributes to the death under the treatment of betulin in combination with gefetinib, the author performed a series of experiments and found that combination induced ROS accumulation, lipid peroxidation, and GSH depletion.The expression of SLC7A11, GPX4 and ferritin heavy chain 1 (FTH1), negative regulators of ferroptosis, was decreased under the combination treatment of betulin and gefetinib.Whereas, the positive regulatory protein of ferroptosis heme oxygenase 1(HO-1) was increased., Therefore, Betulin may be a potential therapeutic agent for NSCLC via inducing ferroptosis.

Capsaicin
Capsaicin, a natural compound present in chili peppers, in fruits of the capsicum genus like cayenne peppers and jalapenos (Chapa-Oliver and Mejía-Teniente, 2016), has attracted attention for its potential health benefits (Sharma et al., 2013).Research suggests that capsaicin may contributes to improved cardiovascular health (Munjuluri et al., 2021) and possess anti-microbial properties (Goci et al., 2021).In a study conducted by Liu (Liu et al., 2022), it was observed that capsaicin exhibited significant inhibitory effects on the proliferation of NSCLC cells.Mechanismlly, capsaicin increased the levels of total iron and ferrous ions, while reducing GSH levels in the treated cells compared to the control group.Additionally, both mRNA and protein levels of SLC7A11 and GPX4 showed significant decreases in NSCLC cells treated with capsaicin compared to the control group.In summary, the treatment potential of capsaicin in NSCLC cells lies in its ability to induce ferroptosis.

Chinese medicine and preparations
In addition, several studies have indicated that certain Chinese medicine and preparations possess the potential therapeutic ability to stimulate ferroptosis to exhibit potential benefits in the treatment of NSCLC.Hedyotis diffusa (HD), a species of flowering plant in the family Rubiaceae, is a traditional Chinese herbal medicine, which exhibits numerous pharmacological activities, including antioxidant (Lu et al., 2000), anti-inflammatory (Hung et al., 2022), and anti-cancer (Wu et al., 2022).It contains various bioactive compounds, including iridoids, flavonoids, triterpenoids, and phenolic acids, which are believed to contribute to its medicinal effects (Zhang et al., 2021).Huang (Huang et al., 2022)found that HD can inhibit NSCLC cells growth and induce characteristics of ferroptosis, including increase in mitochondrial membrane density, shrunken mitochondria, and decline of cristae.Moreover, HD increase cellular Lipid ROS, the Fe 2+ fluorescence intensity and MDA levels.Mechanically, HD-induced ferroptosis in lung adenocarcinoma cells may be related to the voltage dependent anion channel 2/3(VDAC2/3) pathway, (Yang et al., 2020),a group of specific channel proteins, facilitates the exchange of metabolites and ions across the outer mitochondrial membrane and may regulate mitochondrial functions.Furthermore, HD exerts its regulatory effects on the BCL2 apoptosis regulator (Bcl2)/ BCL2 associated X, apoptosis regulator (Bax) protein complex, thereby modulating the functional dynamics of VDAC2/3.This modulation results in the activation of VDAC2/3 channels, facilitating the translocation of ions and facilitating the intracellular accumulation of ROS.Above all, HD could induce ferroptosis via Bcl2 inhibition to promote Bax regulation of VDAC2/3 to attentus the NSCLC cells growth.Zhao (Zhao et al., 2022) showed that Fuzheng Kang'ai (FZKA) decoction significantly suppressed the expression of GPX4 and system Xc − and conducted a reduction in the GSH/GSSG ratio to induce ferroptosis in NSCLC treatment.Importantly, the induction of ferroptosis in NSCLC cells by FZKA decoction was significantly reversed when GPX4 was overexpressed.These findings were further confirmed in vivo animal model, validating the observed effects of FZKA on ferroptosis in NSCLC cells.

Conclusion and prospects
Ferroptosis is a novel form of cell death that distinguishes itself from apoptosis, necroptosis, and autophagy.Multiple Frontiers in Pharmacology frontiersin.org10 evidences have indicated the significant role of ferroptosis in regulating tumor cell growth and drug resistance, making it a potential new target for anti-tumor interventions (Chen et al., 2021a;Song et al., 2021;Wang et al., 2022).Therefore, ferroptosis inducers hold great promise as highly prospective agents for cancer diagnosis and therapeutic intervention, and they are also of significant importance in the development of anti-cancer drugs (Lei et al., 2022).Here, we have summarized the characteristic ferroptosis inducers and their main anticancer mechanisms in Supplementary Table, aiming to provide support for the clinical development of anticancer drugs.
The current study summarized the introduction and mechanism of ferroptosis.The mechanism of ferroptosis mainly involves four processes: GPX4, system Xc − , iron metabolism, and lipid peroxidation.In the field of NCSLC research, the ferroptosis as a novel cellular death mechanism has gathered significant attention in recent years (Zhang et al., 2022b;Zhao et al., 2023).We summarized relevant targets or pathways of ferroptosis in NCSLC therapy as shown in Table 1.Additionally, natural products have made certain progress in the prevention and treatment of NCSLC by regulating ferroptosis process.However, the investigation into the modulation of ferroptosis in NSCLC using natural products is currently in its initial exploratory phase, with certain limitations evident in existing research studies.Firstly, most studies have only explored the molecular mechanisms by which natural product from traditional Chinese medicine induces ferroptosis through a single pathway.Nevertheless, traditional Chinese medicine formulas and patent medicines widely used in clinical practice possess the characteristics of "multiple components, multiple targets, and multiple effects" (Yan et al., 2022).In future research, we should explore the molecular mechanisms of traditional Chinese medicine in regulating ferroptosis from multiple pathways and perspectives, construct "components-targets/ pathways-disease" pharmacological network, and conduct relevant clinical trials.
Secondly, natural products are typically complex mixtures with diverse chemical structures and compositions, which increases the complexity of studying their pharmacological activities and tissue specificity (Xia et al., 2022).These complexities may make it difficult to accurately assess the absorption, distribution, metabolism, and excretion properties of drugs.Based on this, we need to strengthen the exploration of the potential of nanotechnology (Kaur et al., 2022), encapsulation (Linh et al., 2022), and targeted delivery systems (Gorain et al., 2022) to improve the pharmacokinetics and tissue specificity of natural products.
Thirdly, certain natural products may cause adverse reactions in the digestive system, such as nausea, vomiting, diarrhea, gastrointestinal discomfort, etc. (Menniti-Ippolito et al., 2008;Vasudeva et al., 2012;Zorzela et al., 2021;Andrade et al., 2022).Therefore, the importance of conducting controlled clinical trials should be emphasized to evaluate the safety of treatment methods based on natural products for NSCLC patients.
Finally, it is also necessary to consider combining natural products with other treatment modalities, including chemotherapy drugs such as sulfasalazine (Lay et al., 2007), sorafenib (Groenendijk et al., 2015), zalcitabine (McNeill and Wilson, 2007), and cisplatin (Kryczka et al., 2021), which all can be purposed to induce ferroptosis, to improve the efficiency of natural product-based treatments for NSCLC.We believe that with the progress ferroptosis of research, new effective strategies for the treatment of NSCLC can be provided.

FIGURE 3
FIGURE 3Chemical structures of natural products from traditional Chinese herbal medicine.

TABLE 1
The mediators or signal pathways regarding to ferroptosis in the pathological progression of NSCLC.
(Continued on following page)

TABLE 1 (
Continued) The mediators or signal pathways regarding to ferroptosis in the pathological progression of NSCLC.

TABLE 2
Mediators or modulators of ferroptosis.

TABLE 3
Natural products inducing ferroptosis in NSCLC.