Redox signaling-mediated tumor extracellular matrix remodeling: pleiotropic regulatory mechanisms

Abstract

Background

The extracellular matrix (ECM), a fundamental constituent of all tissues and organs, is crucial for shaping the tumor microenvironment. Dysregulation of ECM remodeling has been closely linked to tumor initiation and progression, where specific signaling pathways, including redox signaling, play essential roles. Reactive oxygen species (ROS) are risk factors for carcinogenesis whose excess can facilitate the oxidative damage of biomacromolecules, such as DNA and proteins. Emerging evidence suggests that redox effects can aid the modification, stimulation, and degradation of ECM, thus affecting ECM remodeling. These alterations in both the density and components of the ECM subsequently act as critical drivers for tumorigenesis. In this review, we provide an overview of the functions and primary traits of the ECM, and it delves into our current understanding of how redox reactions participate in ECM remodeling during cancer progression. We also discuss the opportunities and challenges presented by clinical strategies targeting redox-controlled ECM remodeling to overcome cancer.

Conclusions

The redox-mediated ECM remodeling contributes importantly to tumor survival, progression, metastasis, and poor prognosis. A comprehensive investigation of the concrete mechanism of redox-mediated tumor ECM remodeling and the combination usage of redox-targeted drugs with existing treatment means may reveal new therapeutic strategy for future antitumor therapies.

Introduction

The ECM is a widespread, dynamic acellular structure existing in almost all tissues and organs. Typically, the ECM is secreted by cells, which carry out support and protection functions and regulate various biological processes, such as cell proliferation and differentiation, cell invasion, and metastasis, and the maintenance of tissue homeostasis [1, 2]. The primary building blocks of ECM are water, proteins, and polysaccharides. These compounds can assemble to form a unique niche, specific to the parenchyma of that particular tissue type to help it survive, differentiate, and perform its characteristic functions [3]. Furthermore, posttranscriptional mRNA splicing and posttranslational modifications of the matrix can produce abundant cellular matrix components [4, 5]. Generally, ECM- and ECM-associated proteins are collectively known as the ‘matrisome’ encoded by the genome [6]. The construction and components of collagens vary across different tissues, and certain biological phenomena of collagens, such as deposition, degradation, and posttranslational modification, are prone to alterations in tumor cells [4]. The deposit and retention of collagens in the ECM often rely on the polymerization of fibronectin, a form of glycoprotein commonly binding to cell transmembrane receptors such as integrins, which are required for cell adhesion and reciprocal ECM-cell interaction [7, 8]. The mutual interaction termed “dynamic reciprocity” between cells and ECM means that cells can resolve and remodel the structure and elements of the matrix; in turn, the matrix can also affect cell physiological activity, such as gene expression [9, 10]. Thus, the ECM can be considered an indispensable module for tissues and organs to perform various key biological activities.

With increasing number of studies devoted to probing and validating the underlying functions and mechanisms of ECM, the irrefutable role of matrix remodeling in cancer onset and progression is gradually becoming clear. It has been found that ECM remodeling is tightly associated with angiogenesis, signal transduction, the microenvironment, and cancer niche formation [3]. In tumors, the dynamic equilibrium between matrix expression and degradation is disrupted, allowing tumor cells to take control of the ECM and induce aberrant changes in ECM components. A series of enzymes, including, but not limited to, matrix metalloproteinases (MMPs), adamalysins, and cathepsins, are involved in orchestrating degradation and turnover processes. Apart from the degradation of the matrix, tumor “desmoplasia”, the growth of fibrous or connective tissue, also universally appears in diverse solid tumors, which contributes to the crosslink and stiffness of the ECM. It has been observed that matrix crosslinking in the tumor microenvironment is driven by enzymatic and nonenzymatic processes [11, 12]. Elevated matrix crosslinking often results in the stiffness of stroma, which stimulates cellular signaling cascades and the transformation from resident fibroblasts and macrophages to CAFs and tumor-associated macrophages (TAMs), respectively [11, 13], thus facilitating tumor metastasis [14]. Collectively, ECM remodeling acts as a driver and catalyst of cancer progression with the potential to be a therapeutic target and diagnostic marker for cancer treatment.

ROS, which serve as both oxygen derivatives and intracellular second messengers, are predominantly generated by mitochondria and specific enzymes, such as monooxygenases, cytochrome P450, xanthine oxidase, cyclooxygenase, and NADPH oxidases (Nox) [15]. ROS are regarded as essential signaling molecules participating in redox signaling. It is demonstrated that biological redox reactions induced by H₂O₂ are generally associated with the oxidation of cysteine residues on proteins [16]. Cysteine residues often exist in the form of thiolate anion (Cys-S-), which are more susceptible to H₂O₂ compared to protonated cysteine thiol (Cys-SH). In redox signaling, H2O2 catalyzes the transformation of Cys-S- into sulfenic form (Cys-SOH), resulting in conformational changes in protein conformation and affecting their functions. This oxidation process can be reversed by enzymes like glutaredoxin (Grx), thioredoxin (Trx), and disulfide reductases [17]. However, excessive accumulation of H₂O₂ can promote the oxidation of thiolate anions to sulfinic (SO₂H) and sulfonic (SO₃H) species, leading to permanent damage of proteins. Hence, cells need various professional enzymes to prevent the buildup of intracellular ROS. Generally, ROS at physiological levels take part in diverse cellular processes and can suppress oncogenesis [18]. However, upon exposure to certain exogenous stimuli, such as UV radiation [19], the balance between ROS generation and elimination is disrupted, leading to ROS accumulation, genomic instability, and malignant transformation by destroying macromolecules [20].

Emerging evidence has elucidated that redox can manipulate ECM remodeling in diverse ways, including stimulating ECM expression, accelerating ECM modification, and inducing ECM degradation [21]. These abnormal changes further confer cells with hallmarks of cancer cells, such as invasion and metastasis [22]. However, there is currently a lack of systematic reviews in the literature regarding the regulation of the extracellular matrix through redox mechanisms. In this review, we systematically elucidate the molecular mechanisms by which redox signaling regulates the extracellular matrix from three perspectives: generation, modification, and degradation of the extracellular matrix (Fig. 1). Additionally, we summarize the key redox proteins involved in these processes and discuss their potential clinical applications.

Fig. 1.

The contribution of redox signaling to ECM remodeling in cancer progression. ROS can stimulate the extracellular stroma and result in ECM remodeling, thus aiding tumorigenesis and development. ROS induces (a) TGFβ-mediated ECM fibrosis and (b) active ECM expression-related transcription factors, finally promoting ECM expression. Moreover, (c) ROS are also involved in the activation of MMPs, which are essential for ECM degradation and cancer progression. Meanwhile, (d) oxidized modification of ECM caused by redox reactions also plays an important role in carcinogenesis

Redox-dependent ECM expression contributes to cancer progression

Redox signaling induces profibrotic properties of TGF-β to promote tumorigenesis

Excessive deposition of extracellular matrix components (or ECM fibrosis) is a common characteristic of solid tumors and is tightly associated with tumorigenesis and development [23]. ECM fibrosis is primarily caused by the synthesis and accumulation of fibrillar collagen [24]. The deposition of fibrillar collagen creates a compact network of fibrillar proteins, resulting in ECM stiffness [3]. It is able to induce normal epithelial cells to transform into malignant tumor cells [25, 26]. Moreover, stiffened ECM is considered the major barrier to drug treatment and can restrain the infiltration and uptake of chemotherapy drugs to the tumor site [27]. Apart from drug resistance, ECM stiffness is closely associated with tumor cell migration, invasion, and metastasis. For instance, ECM stiffness-mediated intracellular contraction can promote the stiffness of the actin cytoskeleton, contributing to tumor cell migration [28]. Emerging studies have indicated that ECM stiffness activates specific signaling pathways related to epithelial-to-mesenchymal transition (EMT) [8], such as transforming growth factor-β (TGF-β) signaling and the Rho-ROCK-MLC pathway, thereby inducing cancer invasiveness [29, 30]. Meanwhile, the TGF-β signaling pathway is also a key mediator driving fibrogenesis, and redox signaling can induce profibrotic effects [31]. It can induce the expression and deposition of ECM by triggering Smad signaling pathways and creating the proper microenvironment [32]. The activated TGF-β, capable of chemotaxis, can promote the recruitment of macrophages and fibroblasts, which induces high levels of fibrogenic cytokine expression to amplify the fibrotic response [33]. In addition, TGF-β also induces the production of certain growth factors, such as connective tissue growth factor (CTGF), which is deemed a profibrotic marker enhancing profibrotic activities [34]. Importantly, mounting evidence has suggested that the profibrotic property of TGF-β in cancer progression heavily depends on redox signaling. Specifically, ROS can promote the conversion of latent TGF-β into its activated state by oxidizing the latency associated peptide-β (LAP-β) at methionine 253, facilitating the activation of NADPH oxidase 4 (Nox-4) and leading to the production of ROS [35]. These ROS, in turn, regulate downstream protein kinases. For instance, H₂O₂ can oxidize certain cysteine residues of p38 mitogen-activated protein kinase (MAPK), such as Cys39, Cys119, Cys162, and Cys211 in C. elegans [16]. Activation of the p38 MAPK pathway is necessary for TGF-β-mediated fibrosis in cultured human endothelial cells and results in the upregulation of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of ECM degradation [36, 37] (Fig. 2). It is indicated that decreased expression of PAI-1 takes part in the degradation of ECM surrounding cervical cancer stem cells, promoting cancer invasion and metastasis. In particular, tumor cells adhered to the basal membrane produce a mass of PAI-1. In contrast, cancer cells distant from the basal membrane generate less PAI-1, leading to the degradation of ECM surrounding cervical cancer stem cells [38]. In addition, Nox4/ROS is essential for TGF-β-mediated transformation of fibroblasts into myofibroblasts. Myofibroblasts contribute to ECM fibrosis by excessively producing ECM proteins, such as collagens and fibronectin, while simultaneously inhibiting ECM degradation by suppressing the effect of matrix metalloproteases [39] (Fig. 2). Myofibroblastic differentiation is crucial in activating hepatic stellate cells (HSCs), which is important for liver fibrosis and tumorigenesis [40]. Activated HSCs are able to create a conducive environment for hepatocyte proliferation by releasing certain growth factors such as HGF and Wnt ligands [41]. Furthermore, activated HSCs secrete abundant angiopoietin 1 to promote an angiogenic milieu, thereby supporting tumor survival and growth [42]. It has been reported that TGF-β-mediated p38/ROCK/JNK signaling pathways participate in the phosphorylation of Smad2 (Ser250 and Ser255) and Samd3 (Ser204, Ser208, andSer213), which contributes to the conversion process from fibroblasts to myofibroblasts and the invasion and metastasis of endometrial cancer [43]. In addition, certain redox modifications on certain cysteine sites (such as Cys38, Cys159, Cys161, Cys183, and Cys214) involved in the control of extracellular regulated protein kinase 1/2 (ERK1/2) cascade can influence the activation of transcription factor activator protein-1 (AP-1), which can control the expression of the CD44 variant containing exon 6 (CD44V6) [44–46]. CD44V6 is an essential determinant for fibroblast transdifferentiation into myofibroblasts and positively contributes to Nox4/ROS feedback regulation, further amplifying its effect on myofibroblast conversion [47]. Notably, de novo expression of CD44V6 is widespread in gastric cancer (GC). Overexpression of CD44v6 conducive to the desmoplastic response of GC and enhances the malignant behaviors of cancer by controlling stromal cell-mediated ECM remodeling. Mechanically, soluble factors from CD44v6-expressing GC cells dramatically elevate adipose stromal cells (ASC) myofibroblast differentiation and proliferation, promoting ECM fibrosis and tumorigenesis in gastric cancer cells [48].

Fig. 2.

ROS-induced profibrotic properties of TGFβ facilitate tumorigenesis and development. ROS lead to the transformation from latent TGFβ to activated TGFβ, which result in NOX-4 activation and further ROS generation. On the one hand, produced ROS activate downstream protein kinases, such as JNK and p38, consequently facilitating PAI-1-induced ECM degradation and cancer metastasis. On the other hand, NOX-4/ROS are involved in the conversion of fibroblasts to myofibroblasts, which promote ECM fibrosis and tumor metastasis via repressing the function of MMPs and excessively generating ECM proteins

In conclusion, these data strongly illustrate the importance of redox signaling for TGF-β-induced ECM fibrosis in cancer progression. These mechanisms have also been verified in animal models. For instance, in Nox4-deficient mice, bleomycin-induced fibrosis and alveolar epithelial cell apoptosis are prominently decreased compared to wild-type (WT) mice. Epithelial cell death is a key phase during the process of fibrosis [49]. In addition, a lack of collagen deposition and an increase in MMPs/tissue inhibitors of MMPs (TIMPs) have been observed in Nox-4 knockout mice treated with bleomycin [50].

Redox signaling contributes to cancer progression by affecting ECM expression-related transcription factors

Apart from inducing TGF-β-mediated ECM fibrosis, redox reactions also regulate ECM expression by activating transcription factors. Redox signaling can control Fos-Jun heterodimer binding to DNA. This heterodimeric complex also interacts with the transcription factor AP-1, which is necessary to generate collagens in various stages of cancer progression [51, 52]. Almost all types of collagens are associated with tumor growth, cell proliferation and metastasis, however collagen VI is the most active and multifunctional. It was confirmed that collagen VI acts as an antiapoptotic factor that can promote cell proliferation and prevent cell apoptosis in vitro [53]. This finding was also demonstrated in animal models. For example, in the mammary tumor virus-polyoma middle T antigen (MMTV-PyMT) transgenic mouse model, depletion of collagen VI markedly impairs cell proliferative capacity and facilitates cell apoptosis [54]. A similar phenomenon is observed in xenograft breast tumor models and B16F10 melanoma allograft models [55, 56]. Furthermore, collagen VI plays a crucial role in tumor metastasis. A classic example is that collagen VI can contribute to the invasion and metastasis of glioblastoma cells by promoting cell adhesion and diffusion [57]. Collagen VI treatment can significantly elevate the motility of Calu-1 human lung epithelial carcinoma cells [58]. In addition to assisting cell metastasis, collagen VI is widely distributed around or within blood vessels in tumor tissues [59, 60]. Certain angiogenic regulators derived from collagen IV and XVIII, such as endostatin, canstatin, and tumstatin, are essential for stimulating or repressing angiogenesis [61]. The absence of collagen VI negatively impacts the maturation of pericytes and the survival of endothelial cells, thereby reducing vascular permeability and increasing vessel leakiness [56]. These works strongly suggest the significance of collagen VI for angiogenesis. Simultaneously, collagen VI exerts a potent effect in facilitating tumor inflammation. Collagen VI can reinforce the adhesion of macrophages, implying its underlying capacity for recruiting macrophages [62]. Indeed, endotrophin (ETP), a cleavage product of the collagen α3 (VI) chain, can enhance tumor inflammation by augmenting macrophage recruitment and elevating inflammatory cytokines [54]. As mentioned above, redox reactions may induce collagen expression by manipulating the AP-1 transcription factor, further contributing to tumor cell proliferation, metastasis, and angiogenesis.

In addition, the redox reaction also affects MMPs through an identical mechanism. MMPs have long been associated with cancer and are involved in the regulation of the tumor microenvironment, cancer cell metastasis, inflammation, and angiogenesis. Solid evidence has shown that MMPs are implicated in the formation of the premetastatic niche. The augmented MMPs in the premetastatic niche can release certain soluble factors responsible for recruiting cells, such as bone marrow-derived cells (BMDCs) to the premetastatic niche [63]. In addition, MMPs can influence specific growth signals, such as TGF-β signaling, to drive the invasion and metastasis of different tumors including ovarian carcinoma [64, 65]. MMP-1 has been demonstrated to be a valuable prognostic marker in certain cancer types (e.g., breast cancer, colorectal cancer), tightly correlating with tumor invasion and metastasis [66–68]. Its effect on cancer progression relies on ROS-mediated activation of transcription factors. The overexpression of superoxide dismutase (SOD2) can increase the metastatic potential of fibrosarcoma cells by elevating DNA-binding activity of some transcription factors related to MMP-1 expression. These changes can be reversed through catalase, indicating that redox-controlled MMP-1 expression is H₂O₂-dependent [69, 70]. Moreover, the aggregation of c-Jun and other transcription factors, such as c-Fos and Ets-1, to the MMP-1 promoter also relies on histone deacetylase-2 (HDAC-2) inactivation caused by H₂O₂ [48]. Apart from MMP-1, ROS also promote cancer progression by affecting other MMPs-related transcription factors. For instance, H₂O₂ is capable of triggering MMP-7 generation through the activation of JNK/c-Jun and ERK/c-Fos in an AP-1-dependent manner, further accelerating the invasion and metastasis of SW620 human colon cancer cells [71]. Moreover, as a crucial downstream transcriptional mediator of ROS generation, Est-1 can be controlled by H₂O₂ via antioxidant response element (ARE) and the phosphorylation of forkhead box class O4 (FOXO4) on threonine 447 and threonine 451 [72]. Est-1-mediated MMP-9 production is demonstrated to be closely associated with the elevated aggressiveness and metastatic trait of breast cancer cells. MMP-9 gene promoter contains an Est-1 binding site that involves the transactivation of Ets-1 and EMT markers [73]. In addition, Est-1-dependent MMP-2 expression is also critical to boosting various cancer progressions, such as pancreatic cancer [74]. In conclusion, the expression of MMPs is strongly modulated by redox biological reactions in cancer.

The activation of these transcription factors is likely attributed to redox-response pathways. For instance, ERK and p38 MAPK induce the phosphorylation of Foxo1a, further controlling the transcriptional activity of Ets-1 [75], Likewise, ERK and p38 MAPK signaling is utilized by H₂O₂ to increase the transcription of c-Fos and c-Jun [76]. Collectively, these studies adequately illustrate the profound effect of redox signaling on MMP-related transcription factors. These effects also play an essential role in various phases of cancer progression.

Redox-regulated ECM remodeling acts as an essential driver for tumorigenesis and development

Oxidation-related enzymatic digestion is conducive to tumor growth and metastasis by activating MMPs

In addition to redox-mediated ECM expression, redox reactions can also modulate the modification of the stroma, which promotes cancer progression. There are two main mechanisms of ECM modification, namely enzymatic digestion and oxidation. The typical example of enzymatic digestion is the activation of MMPs. The majority of MMPs produced by cells generally exist in the form of ‘proenzymes’, and their activation is dependent on the proteolysis of the ‘cysteine switch’, which is a cysteine-zinc domain [77]. Activated MMPs can affect numerous ECM components, including collagens, fibronectin and certain basement membrane constituents. MMP-dependent ECM proteolysis can be repressed by tissue inhibitors of metalloproteinases (TIMPs), and TIMPs control the activity of MMPs in a 1:1 stoichiometric manner. Elevated TIMPs lead to the deposition of ECM, which also accelerates tumorigenesis [78]. Emerging evidence has shown that enzymatic digestion is linked to oxidant reactions due to the activation and cleavage of MMPs relying on reactive oxidant species. For example, oxidized glutathione can aid the oxidation of MMPs, thus promoting their activation and simultaneously suppressing the expression of the TIMP gene [21] (Fig. 3). Similarly, oxidized glutathione can induce the activation of myocardial MMPs during end-stage heart failure [79]. Importantly, ROS-mediated MMP activation is also tightly associated with cancer progression. In human renal cancer, augmented ROS can upregulate MMP-2 and MMP-9, promoting tumorigenesis [80]. Moreover, a molecular axis consisting of hydrogen peroxide-inducible clone-5 (HIC-5), NOX4, and mitochondria-associated reactive oxygen species (mtROS) that control MMP9 expression and cancer metastasis. Specifically, HIC-5 represses the production of NOX4 through RAS signaling, thus reducing the levels of mtROS and the stability of MMP9 mRNA [81]. This testifying NOX4-mediated mtROS signaling is conducive to stabilizing MMPs mRNA and involves tumor metastasis. Moreover, the catalytic activity of protein kinase Cα (PKCα) on MMP-9 expression in lung cancer cell A549 relies on the generation of NOX-2/ROS and the phosphorylation of activating transcription factor-2 (ATF-2), indicating that the PKCα/Nox-2/ROS/ATF-2/MMP-9 signaling pathway is involved in cancer progression [82]. Binker-Cosen MJ et al. found that the risk of pancreatic cancer cells AsPC-1 were strongly related to saturated fat, especially saturated palmitic acid (PA) from animal food sources. They demonstrated that PA triggered the TLR4-mediated tumor cell invasion. Mechanically, TLR4 promotes the production of ROS, therefore exciting NF-κB activation and MMP-9 secretion [83]. Analogously, blocking intracellular ROS and ERK pathway can decrease the expression of MMP-9 and MMP-2 in pancreatic cancer [84]. Typically, the MMP family is classified into six groups, including collagenases, stromelysins, gelatinases, matrilysins, membrane-type MMPs, and other nonclassified MMPs. MMPs play a crucial role in shaping the tumor microenvironment. On one hand, they facilitate tumor growth by eliminating physical obstacles. MMP-1 and MMP-13 are responsible for the degradation of Type I, II, and III collagen, while MMP-3 can also degrade Type III collagen [85]. MMP-3 and MMP-10 directly break down non-collagen connective tissues such as fibronectin, proteoglycans (PGs), and laminin. Moreover, matrilysin MMP-7 has a broad specificity to degrade ECM components such as fibronectin, collagen-IV, vitronectin, elastin, aggrecan and laminin [86]. On the other hand, MMPs control the release of numerous growth factors attached to the cell membrane, manipulating their bioavailability by degrading ECM. For instance, MMP-1 and MMP-3 degrade endothelial-derived perlecan, releasing basic fibroblast growth factor (bFGF) and contributing to angiogenesis during cancer invasion and metastasis [87]. In addition, MMPs also degrade insulin-like growth factor binding protein-3 (IGFBP-3) and release insulin-like growth factors (IGFs), which can bind to cell surface receptors and promote cell proliferation [88]. TGF-β is one of the major growth factors released by MMPs mediated ECM degradation. The release of TGF-β is associated with fibronectin degradation by the connection of MMP-9 and CD44. Similarly, the MMP (MMP-1, -2, -3, -7, and -9)-mediated decorin degradation can also release this factor (Fig. 3). Interestingly, TGF-β is often regarded as an inhibitor of proliferation in normal and tumor cells at an early stage of tumor cell growth. However, most cancer cells have been found to develop resistance to tumor suppressive effects and simultaneously elevate the generation of TGF-β to promote tumor invasion and metastasis [89]. MMPs are also connected with the release of the proinflammatory cytokine TNF-α, whose excessive accumulation maintains tumor cell survival in an NF-κB-dependent fashion [64]. Mechanically, MMPs promote the conversion of precursor TNFα into a soluble 17.5-kDa cytokine by processing proper cleavage sites. For example, MMP-7 processes the precursor TNFα polypeptide between Ala76 and Val77, and MMP-1 cleaves pro-TNFα between Ala76 and Val77 as well as between Ala74 and Gln75. MMP-9 is found to cleave substrate between Ala74 and Gln75, finally converting pro-TNFα to a 17 kDa band [90]. In addition, MMP17 can hydrolyze glutathione S-transferase-pro-TNFα fusion protein, which contains pro-TNFαcleavage site [91] (Fig. 3).

Fig. 3.

Oxidation-mediated MMPs activation contributes to tumor growth and metastasis. (A) Oxidative stress facilitates MMPs activation. Glutathione can be oxidized under oxidative stress conditions and oxidized glutathiones activate MMPs through proteolysis. (B) Activated MMPs maintain survival and growth of cancer cells. MMPs accelerate the degradation of specific ECM components such as fibronectin, decorin, perlecan, further releasing numerous growth factors such as TGF-β and bFGF to aid tumor growth. Moreover, MMPs also sustain tumor survival and growth by releasing the proinflammatory cytokine TNF-α. (C) Activated MMPs promote the migration, invasion, and metastasis of tumor cells. On the one hand, MMPs are implicated in connecting and disconnecting stages during cell migration. On the other hand, MMPs activate TGF-β, consequently inducing EMT and cancer metastasis

MMPs are also implicated in multiple stages of tumor metastasis, including the deficiency of intercellular junctions, the release of tumor single cells by preventing anoikis and degrading extracellular stroma, the penetration of cancer cells into blood vessels, and the colonization of distant organs [92]. Anoikis typically arise from the lack of a connection between cells and the ECM, but cancer cells are not susceptible to this mechanism. An essential method of tumor cells overcoming anoikis is epithelial to mesenchymal transition (EMT), which aids in cancer invasion and metastasis. MMP-28 has been demonstrated to activate TGF-β through proteolysis, thus promoting the induction of EMT in lung carcinoma cells [93] (Fig. 3). Intriguingly, mesenchymal cells can generate many MMPs and rely less on the MMPs arising from normal host cells. Furthermore, MMPs are involved in the processes of tumor cell migration, which is indispensable for the localization of cancer cells. Cell migration is commonly divided into two categories, comprising the movement of a single cell or a group of cells. In the latter pattern of movement, cell junctions are preserved, yet when cells move solely, they migrate in the manner termed ‘mesenchymal’ or ‘amoeboidal’. MMPs participate in the connecting and disconnecting stages during mesenchymal cell migration in these processes. Moreover, in the process of migration, MMPs can affect specific adhesion molecules attached to the cell surface. Meanwhile, the digestion of ECM components through MMPs is beneficial for the movement of tumor cells. Due to the mechanic-sensory system, tumor cells are able to choose migration strategies according to their microenvironment [94]. For example, when ECM is degraded by CAFs, neoplastic cells can move through pre-existing paths using amoeboid migration type [95]. MMP-14 is required for amoeboid type migration [96]. Similarly, MMP-9 maintains rounded form of tumor cells through CD44 receptor [97]. Therefore, the shape and motility of tumor cells are partially regulated by the ECM stiffness and MMPs-induced ECM degradation.

Thus, this information suggests that oxidation-mediated enzymatic digestion can facilitate cancer cell survival, growth, proliferation, and metastasis by activating MMPs. In addition, ROS-mediated MMPs can also impact apoptosis and angiogenesis, indirectly regulating tumorigenic cell survival and dissemination [98–100].

Oxidation reactions affect cancer onset and development by modifying ECM components

Generally, the extracellular components are more susceptible to oxidative stress than the intracellular environment. There are fewer antioxidants and repair enzymes in the extracellular stroma [101]. Oxidants generated by cells can exert oxidative stress primarily in the intracellular environment, there are mechanisms by which oxidants can also impact the extracellular components. These mechanisms include the release of reactive oxygen species (ROS) from cells, which can diffuse into the extracellular space and affect the extracellular matrix (ECM) and its components. These processes are primarily associated with inflammatory dysregulation manifested as the activation and aggregation of neutrophils and leucocytes, which leads to the formation of Nox complexes and generates superoxide radicals [101]. Superoxide radicals can diffuse into the extracellular space and yield hydrogen peroxide by dismutation, subsequently producing more oxidants [102, 103]. Furthermore, activated leukocytes, monocytes, and macrophages can release myeloperoxidase and eosinophil peroxidase, which can exacerbate damage at specific sites of ECM proteins and react with hydrogen peroxide, subsequently producing oxidants such as hypohalous acids [104, 105]. For instance, monocyte-derived myeloperoxidase (MPO) catalyzed the nitrotyrosine formation of ECM proteins, especially fibronectin, in the presence of substrates H2O2 and NO2- [106]. Elevated nitrotyrosine is broadly associated with various cancers, including but not limited to esophageal cancer, breast cancer, and gastric cancer [107, 108]. In addition, hypohalous acids produced by myeloperoxidase and eosinophil can react with amine groups of amino sugars in proteoglycans, leading to the production of halamides, mono- and dihalamines, which possess potential arcinogenic hazards [109, 110].

The aforementioned series of oxidation reactions can modify a plethora of ECM components, such as collagens, fibronectin and glycosaminoglycans (GAGs). Among these ECM materials, the heparan sulfate chains on GAGs are especially susceptible to oxidized by peroxynitrite, which is a presumptive oxidant involved in the initiation of ECM modification, finally resulting in the degradation of GAGs [111–113]. GAGs are the primary structural and functional ECM macromolecules expressed in almost all mammalian cells [114, 115]. They play a well-known role in cell survival and stromal properties and widely affect tumorigenesis and development, such as the regulation of metabolic reprogramming, cell proliferation, angiogenesis, cell metastasis, and immune surveillance [114]. The interactions between hyaluronan (HA) and its receptor CD44 have been demonstrated to aid cancer stem cell (CSC) self-renewal and sustain stemness, further acquiring resistance to oxidative stress [116]. It has been demonstrated that the oxidation of HA can decrease the binding free energy between HA and CD44, indicating that oxidation negatively affects the disturbance of CD44-HA interaction. These influences result in the repression of proliferative signaling pathways inside cancer cells to promote cell death [117]. Furthermore, nitrogen dioxide radical, generated by the interactions between nitric oxide (•NO) and O₂, can react with HA to promote the fragmentation of the polymeric chains, which decreases the migration of breast cancer cells [118]. Thus, oxidative modifications of HA play a potential role in cancer initiation and progression.

In addition, ECM modification caused by oxidation appears to alter the structure and stability of fibrillary collagens. For instance, collagen type III is generally considered a homotrimer cross-linked by an interchain cystine knot composed of three disulfide bridges. The formation of proper interchain cysteine pairings stems from the processes of protein oxidative folding [119]. Interestingly, cystine-knot miniproteins have been deemed prospective candidates for the development of antitumor drugs due to their drug-like properties and the underlying capacity to selectively bind clinical targets [120, 121]. Furthermore, due to their excellent stability and distinctive structural characteristics, they are expected to address intractable drug development goals, such as oral administration and binding to specific drug targets [122]. Apart from the impact on ECM components, oxidative reactions can also perturb the mutual interaction between ECM and growth factors. For instance, fibroblast growth factor 2 (FGF2) often combines with perlecan through its heparan sulfate chains. The oxidative modification of perlecan is likely to control the sensitivity of FGF2 to proteolysis [123]. FGF2 is a crucial regulator of ECM remodeling and cancer progression. It can increase the levels of plasmin-plasminogen activator (uPA) and MMPs, which result in ECM degradation, angiogenesis and tumor metastasis [124]. ECM-FGF2 also facilitates tumor growth by inducing Cyclin D1, which can prevent G1 arrest in breast cancer cells [125]. In addition, the nuclear translocation of FGF2 in pancreatic stellate cells can promote the invasion of tumor cells, and the abrogation of nuclear FGF2 represses pancreatic cancer cell invasion [126]. In breast cancer, FGF2/ERK signaling mediates KIF26B-induced cancer cell proliferation and migration [127]. Hence, the oxidative modification of perlecan may influence cancer progression by regulating the activation of FGF2.

Oxidants also function to cleave the matrix, leading to the shedding of ECM components. For instance, superoxides can cleave hyaluronan and heparan sulfates (HS), leading to redox reactions that regulate the distribution of syndecan-1 [128, 129]. During carcinogenesis, syndecan-1 is released from the basement membrane and translocates into the cytoplasm or nucleus. Its nuclear localization of syndecan-1 regulates intracellular signaling via protein phosphorylation and other posttranslational modifications [130]. In mesothelioma, intranuclear syndecan-1 is associated with the cell cycle and appears to function by interacting with microtubule structures [131]. Furthermore, shed syndecan-1 has been shown to facilitate the proliferation of breast cancer cells and promote tumor growth of lymphoblastoid cells in vitro [132, 133]. And overexpressed soluble syndecan-1 and mimetic regions of syndecan-1 enhance the invasive phenotype of breast cancer cell lines [134].

Therapeutic intervention of redox-controlled ECM remodeling for treating cancer

The above studies suggest that redox-regulated ECM remodeling plays critical roles in cancer cell survival, proliferation, migration, invasion, and metastasis. It is rational that targeting redox homeostasis holds promise for overcoming redox-mediated ECM remodeling to treat cancer. For instance, N-acetylcysteine (NAC), an essential antioxidant, significantly attenuates the production of mitochondria-derived ROS, thus suppressing EMT and the metastatic phenotype in pancreatic cancer cells [135, 136]. The scavenger activity of NAC has been proven against hydrogen peroxide, hydroxyl radicals, and hypochlorous acid, which play essential roles in ECM remodeling [137]. It is also reported that NAC can markedly repress the levels of collagen types I, II, III, and aggrecan and inhibit the gene expression of certain ECM-destructive enzymes such as MMP-1, -2, -3, -13 and ADAMTS-4 [138–140]. Furthermore, NAC suppresses the proteolytic activity of MMPs and decreases the release of PG [140]. Analogously, certain natural antioxidant agents, such as galangin and apigenin, are also able to repress cell migration and invasion [141]. Treatment with galangin can induce superoxide dismutase and glutathione peroxidase activities and simultaneously decrease the expression of TGF-β that contributes to ECM fibrosis [142]. Apigenin can restrain the expression of transcription factors c-Jun and c-Fos, as well as inhibit collagenolytic MMP-1 generation via interfering with AP-1 signaling (Fig. 4) [143]. Interestingly, dietary interventions have also been shown to have an antioxidant function. Vitamin C is able to promote cell apoptosis in multiple cancers [144, 145]. The phosphorylated Vitamin C can eliminate a majority of intracellular ROS and down-regulate MMPs generation (Fig. 4). Moreover, treatment of melanoma cells with Vitamin C can result in changes in genome-wide transcriptions, predominantly in genes associated with ECM remodeling [146].

Fig. 4.

Therapeutic strategies of cancer targeting redox-regulated ECM remodeling. Antioxidant NAC can inhibit the generation of hydrogen peroxide, hydroxyl radicals, and hypochlorous acid, simultaneously decreasing collagen levels and the gene expression of MMPs. Meanwhile, galangin can stimulate the activation of superoxide dismutase and glutathione peroxidase. Apigenin is found to restrain the expression of transcription factors c-Jun and c-Fos. In addition, Vitamin C is able to promote tumor cell apoptosis and eliminate a majority of intracellular ROS. DHB and 1,4-DPCA can repress nitric oxide synthesis and CP4H-mediated collagen generation

Anoikis is a unique type of cell apoptosis resulting from ECM detachment [147, 148]. The redox signaling-mediated remodeling of ECM can induce anoikis resistance in various cancer types. Specifically, anoikis resistance elevates the production of perlecan αv, β3, α5, laminin, HA, and metalloproteinases 2 and 9, and displays the down-regulation of fibronectin and collagen IV [149]. Notably, emerging evidence has proved that ROS generated by NOX are involved in anoikis resistance. For example, in prostate cancer cells, leukotriene B4 receptor-2 (BLT2) can mediate anoikis resistance by promoting the accumulation of NOX-induced ROS [150]. NOX4/ROS can activate specific pro-survival signaling pathways, such as TGF-β signaling, to endow tumor cells with anoikis resistance [22]. Thus, Nox4 may emerge as an underlying target to prevent redox-induced carcinogenesis. It has been reported that 4-Me, an efficient amino endoperoxide, can selectively facilitate cell apoptosis of metastatic breast tumor cells with high Nox4 levels. The mechanism of this amino endoperoxide is related to the increase in the ·OH level and the decrease in the O₂(-):H₂O₂ ratio [151]. Moreover, targeting redox-regulated anoikis may also be a potential therapeutic strategy for blocking the effects of anoikis on ECM remodeling in cancer progression. For instance, LTB2 can promote anoikis resistance by accumulating ROS and activating NF-κB, and the treatment with diphenyleneiodonium (DPI) can dramatically impair B4 receptor-2 (BLT2)-induced anoikis resistance in prostate cancer cells [150].

As mentioned above, redox reactions can accelerate ECM fibrosis by inducing the profibrotic properties of TGF-β, thereby promoting cancer progression. ECM fibrosis mainly results from the synthesis and accumulation of fibrillar collagens. Therefore, intervention with collagen synthesis has been proposed as a prospective therapeutic avenue to prevent the redox-induced deposition of collagens. Collagen prolyl-4-hydroxylase (CP4H) is often considered a vital enzyme in the biosynthesis of collagens. It can facilitate the transformation from proline to hydroxyproline and induce the formation of the procollagen triple helix by assembling procollagen proteins [24]. Remarkably, its expression can result in breast cancer cell alignment along collagen fibrils, inducing the deposition of collagens [152]. 3,4-dihydroxybenzoate (DHB), an inhibitor of prolyl hydroxylase, can reversibly suppress the differentiation of myoblasts, prominently reducing the generation of procollagen and collagen-binding glycoprotein (gp46) (Fig. 4) [153]. Synchronously, DHB remarkably alleviates the induction of nitric oxide synthase, cooperating with the reduction of ROS levels and the activation of MAPK and NF-κB pathways [154]. In addition, 1,4 dihydrophenonthrolin-4-one-3-carboxylic acid (1,4-DPCA) was also verified as a crucial inhibitor of CP4H to retard excessive accumulation of collagens (Fig. 4) [155]. As well as CP4H, LOX is a potential target since it is an essential mediator of collagen crosslinking. Disturbing the posttranslational crosslinking of collagens through LOX has an obvious tumor suppressive effect in preclinical trials [156]. Moreover, there exists a positive correlation between LOX and ROS in cancer. LOX is able to facilitate ROS formation, further resulting in oxidative DNA damage [157]. ROS accumulation, in turn, directly increases the transcriptional induction of LOX [158, 159]. Furthermore, a LOXL2-targeting monoclonal antibody (AB0023) has significantly reduced fibroblasts, desmoplasia, and endothelial cells. Meanwhile, specific signaling pathways, such as TGF-β signaling, were also repressed [160]. Furthermore, preclinical studies have indicated that LOX inhibition used in combination with gemcitabine can effectively inhibit tumor cells and prolong the tumor-free survival of mice. Specifically, this synergy is closely correlated with ECM changes, such as reducing the formation of fibrillar collagens and augmenting the infiltration of macrophages into tumor tissue [161].

These findings provide potential treatment strategies to address carcinogenesis and cancer progression driven by redox-mediated ECM remodeling. One approach involves utilizing specific antioxidants to target redox homeostasis and prevent ECM remodeling caused by the excessive accumulation of ROS. Synchronously, by targeting key enzymes in redox reactions, such as Nox4, it becomes possible to inhibit the TGF-β-induced ECM fibrosis and anoikis resistance, thus suppressing tumorigenesis and development. Another promising approach is to target ECM alterations resulting from redox signaling, particularly excessive fibrosis, as this can effectively prevent the life-threatening diffusion of tumor cells. However, it is essential to note that therapeutic strategies for redox-mediated ECM remodeling in tumors are still in the early stages of development. Due to the high dependence of redox regulatory mechanisms on redox levels, further research is needed to explore appropriate administration and dose methods for redox-targeted treatment strategies. Additionally, the lack of specific molecules that target redox modification poses a challenge in implementing effective treatment strategies. Therefore, conducting in-depth research into regulating redox-modified ECM proteins is crucial to understanding intricate physiopathological processes and developing more efficient therapeutic approaches.

Perspective and discussion

It is universally recognized that with increasing age, oxidative damage can result in abnormal alterations of the ECM by controlling the expression and modification of the matrix, thus giving rise to disordered ECM homeostasis and tumorigenesis (Table 1). Solid tumors are not purely composed of cancer cells; they can be considered organs that possess specific cells within the extracellular matrix, blood vascular systems, and ECM morphology [162]. However, distinct from normal organs, tumor tissues do not respect the laws controlling normal tissues and continually override restrictions aimed at sustaining the cooperative balance of our body. How ECM fail to block the development of cancer is not completely clear. However, in order to target and restore control of tissue homeostasis from tumor tissues, a comprehensive understanding of how redox reactions affect cancer onset and progression via ECM remodeling is essential.

Table 1.

Representative redox sensor in the regulation of ECM remodeling in cancer

Source of ROS	Protein	Site	Function	ECM remodeling	Cancers	Ref
			Increasing the expressionof PAI-1	Fibrosis	Cervical cancer	[70, 72, 73]
			Promoting the productionof collagen	Fibrosis	Breast cancer, Lung cancer, Glioblastoma	[93–96]
	p38 MAPK	Cys39, Cys119, Cys162, Cys211	Manipulating MMP-1 and MMP-7 production by theregulatingc-Junandc-Fos	Degradation	Fibrosarcoma, Coloncancer	[109–111]
			Controlling Ets-1 activity via the phosphory lation of FoXO	Degradation	Breastcancer, Pancreaticcancer, Bladdercancer	[115–122]
			Increasing the expressionof CD44V 6through AP-1	Fibrosis	Gastric cancer	[80–83, 85]
NOX-4	ERK	Cys38, Cys159, Cys161, Cys183, Cys214	Promoting the generation of collagen byAP-1	Fibrosis	Breastcancer, Lungepithelial carcinoma, Glioblastoma	[93–96]
			Increasing MMP-1 and MMP-7 production by there gulating c-Jun and c-Fos	Degradation	Fibrosarcoma, Coloncancer	[109–111]
			Regulating Ets-1 activity via the phosphorylation of FoXO	Degradation	Ovariancancer, Squamouscarcinoma, Meningiomas	[117, 120–122]
	LAP-β	Met253	Activating TGF-β1	Fibrosis	Prostate cancer	[68, 69, 71]
	Smad2/3	Ser204, Ser208, Ser213, Ser250, Ser255	Converting fibrolaststo myofibrolasts	Fibrosis	Endometrial cancer	[78, 79]
	FoXO4	Thr447, Thr451	Promoting the generationof MMP-2, MMP-9 and MMP-13 by regulating transcriptionalactivity of Ets-1	Degradation	Breastcancer, Pancreaticcancer, Bladder cancer, Ovarian cancer, Squamouscarcinoma, Meningiomas	[114–121]
NOX-2	PKCα	/	Elevating the expression of MMP-9 expression	Degradation	Lung cancer	[129]
	HA	Unit monosaccharides and glycosidic substituents	Regulating the distributionof syndecan-1	Degradation	Breastcancer, Mesothelioma	[179, 181, 182]
Mitochondria	Perlecan	/	Regulating the sensitivity of FGF2 to proteolysis	Degradation	Pancreaticcancer, Breastcancer	[172, 176]
	HS	/	Regulating the distribution of syndecan-1	Degradation	Breastcancer, Mesothelioma	[181, 182]

In this review, we have indicated how redox reactions facilitate the expression, modification, and degradation of the matrix, contributing to various phases of cancer progression, such as cell survival, proliferation, angiogenesis, invasion, and metastasis. Excessive ROS generation can regulate ECM remodeling and promote carcinogenesis. Interestingly, the absence of ROS can also lead to tumorigenesis [18]. However, whether the shortage of ROS is associated with ECM remodeling still requires further investigation. Moreover, the mechanisms discussed above suggest that ECM is an essential medium by which redox signaling is conducive to cancer progression. Numerous biomarkers in the extracellular stroma could be conducive to the initial diagnosis and subsequent treatment of cancer. For instance, the levels of circulating ECM-related proteins, such as SPARC, have been used to distinguish lung cancer patients from healthy heavy smokers [163]. In addition, certain MMPs and TIMPs can be considered candidate biomarkers for tumor diagnosis and prognosis, including MMP-2, -9, -7 and TIMP-1, -2 in renal cell carcinoma, MMP-7 and -12 in pancreatic cancer, MMP-8 and TIMP-1 in colorectal cancer, and MMP-2, -9 and MMP degradation products of collagens -1, -3 and -4 in breast cancer [164, 165]. Importantly, it was demonstrated that redox reactions are tightly associated with the expression and activation of MMPs, and the activity of MMPs is potently regulated by TIMPs. Thus, it is plausible that MMPs and TIMPs may function as biomarkers of various cancers. They are promising potential targets for diagnosing and treating cancers mediated by redox-induced ECM remodeling.

In terms of therapeutic strategies, overcoming cancers induced by redox signaling-mediated ECM remodeling by inhibiting oxidation reactions and the critical enzymes in this process or targeting the aberrant changes in the ECM such as fibrosis, cannot be over emphasized. Additionally, pro-oxidant therapies also play vital roles in cancer treatment. Certain chemotherapy drugs [166], such as daunorubicin, procarbazine, and paclitaxel, can suppress tumor cells and act partly by aggravating oxidative stress [167, 168]. Moreover, numerous small molecule drugs have been tested in clinical research [169]. For instance, Imexon, a cyanoaziridine derivative, exerts antitumor effects by exhausting glutathione and elevating ROS levels and has been used in the treatment of some types of cancer, including pancreatic, lung, breast, prostate, melanoma, and multiple myeloma [170]. Similarly, arsenic trioxide can result in electron leakage and superoxide formation, thus contributing to the treatment of acute promyelocytic leukemia [171]. However, whether excessive ROS produced by these pro-oxidant therapies are associated with ECM remodeling is uncertain. Taken together, the extensive studies to date have provided a tremendous impetus to further explore how redox signaling affects the extracellular stroma, facilitating cancer progression and will impact on improved cancer treatment in the future.

Author Contributions

Conceptualization, J.Y., L.Y., C.H. and G.L; investigation, J.Y., L.Y. and C.H.; writing—original draft preparation, G.L., B.L. and S.Q.; writing—review and editing, B.L. and S.Q.; literature searching, B.L. and E.C.N; polishing the manuscript, E.C.N.; visualization, G.L. and B.L; supervision, J.Y., L.Y., C.H.; funding acquisition, C.H. and J.Y.; All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by grants from 1·3·5 project for disciplines of excellence, West China Hospital, Sichuan University (ZYGD22007) and the Sichuan Province Science and Technology Support Program (No. 2022YFH0003).

Data Availability

Not applicable.

Declarations

Competing interests

The authors declare no competing interests.

Conflicts of Interest

The authors declare no conflict of interest.