Matrix metalloproteinase-driven epithelial-mesenchymal transition: implications in health and disease.

Epithelial carcinoma cells that experience EMT lose their apical–basal polarity and reorganize the actin cytoskeleton, adopting a spindle-like mesenchymal morphology. This shift, triggered by both stromal and tumor-derived growth factors, dismantles tight junctions, adherens junctions, and desmosomes, thereby enhancing invasive capacity. Once tumor cells overexpress MMPs, they can degrade basement membranes and surrounding stroma, facilitating intravasation into the bloodstream as circulating tumor cells (CTCs) [ 153 – 155 ]. Signals from platelets, including TGF-β, help preserve the mesenchymal phenotype while CTCs travel through the circulation. Upon reaching distant sites, tumor cells may extravasate and undergo MET, aided by fibroblasts, endothelial cells, and myeloid progenitors in the new microenvironment. This final MET step is often necessary for the establishment of overt metastases [ 156 ]. The molecular control of cancer EMT hinges on a set of core transcription factors (Snail, Twist, Zeb) and epigenetic modifications. Downregulation of E-cadherin, for instance, corresponds to upregulation of mesenchymal markers (e.g., N-cadherin, vimentin), a hallmark of metastatic capability [ 157 – 160 ]. Snail1 disrupts apical–basal polarity by inhibiting Crumbs3 and PAR complexes, while non-canonical TGF-β signaling contributes to cytoskeletal alterations by degrading PAR3 and RhoA [ 159 , 161 , 162 ]. Additional polarity regulators, including lethal giant larvae 2 (LGL2) and Crumbs3, are suppressed as EMT progresses, eliminating typical epithelial architecture and driving cells toward a motile, invasive phenotype [ 163 , 164 ]. Concurrently, tumor cells often rewire core metabolic pathways to sustain rapid proliferation and survival under EMT conditions [ 165 , 166 ]. A prominent feature is the Warburg effect, wherein cells favor glycolysis over mitochondrial respiration, generating lactate even when oxygen is abundant [ 167 ]. Heightened expression of glycolytic enzymes like hexokinase 2 (HK2) and phosphoglucose isomerase (PGI) correlates with more aggressive cancers, including pancreatic ductal adenocarcinoma and breast cancer [ 168 – 170 ]. Similarly, transcription factors such as Snail1 can silence fructose-1,6-bisphosphatase 1 (FBP1), boosting glucose uptake and lowering reactive oxygen species (ROS), thereby rendering cells resistant to anoikis [ 171 , 172 ]. Enhanced expression of glucose transporters (Glut1, Glut3) complements these metabolic changes by increasing cellular glucose influx. In hypoxic settings, Glut1 levels rise alongside mesenchymal markers like N-cadherin and vimentin, correlating with poorer clinical prognosis [ 173 , 174 ]. By modulating both morphology and metabolism, EMT confers a survival advantage, enabling cancer cells to persist under stringent microenvironmental conditions. EMT also bestows tumor cells with stem-like features, giving rise to cancer stem cells (CSCs) that drive metastasis, resist conventional therapies, and promote tumor recurrence [ 175 , 176 ]. Transcription factors like Snail1, Twist, Zeb1, and mediators like TGF-β orchestrate this conversion, often accompanied by characteristic cell surface expression phenotypes such as CD44 high /CD24 low in breast carcinoma [ 177 ]. CTCs isolated from pancreatic cancer patients and metastatic breast cancer xenografts display both mesenchymal and stem cell markers, underscoring the functional overlap between EMT-driven plasticity and CSC formation [ 154 , 178 , 179 ]. CTCs constitute a transient but critical intermediary in the metastatic cascade [ 180 ]. Although epithelial cell adhesion molecule (EpCAM)-based assays initially targeted cells retaining epithelial traits, EMT-activated CTCs commonly exhibit reduced EpCAM and elevated mesenchymal proteins, rendering them more elusive to detection [ 181 , 182 ]. Various markers—including cell surface vimentin (CSV), Plastin3 (PLS3), and transcription factors such as Snail and Twist—have been employed to identify these populations across multiple malignancies [ 183 – 186 ]. Monitoring E-cadherin levels on prostate cancer CTCs, for example, can predict relapse or metastatic spread before imaging findings confirm disease progression [ 187 ]. Angiogenesis, vital for supplying nutrients and oxygen to expanding tumors, intersects with EMT in several ways. Mesenchymal-like tumor cells frequently upregulate pro-angiogenic factors (e.g., VEGF) while downregulating anti-angiogenic molecules, thereby fueling neovascularization [ 81 , 188 ]. Upregulation of vascular endothelial growth factor (VEGF) and stimulation of tumor angiogenesis also contribute to the acquisition of stem-like characteristics by cancer cells undergoing EMT [ 189 ]. The relationship between VEGF expression and EMT can be complex and reciprocal; in a model of progression to invasive prostate carcinoma, VEGF signaling stimulated EMT through TGF-β, promoting tumor cell invasion and motility [ 190 ]. Proteins like Ephrin-A2 can further induce EMT and stimulate angiogenesis, reinforcing a cyclical relationship between EMT, angiogenesis, and tumor invasion [ 191 ]. The intersection of these factors can lead to important clinical consequences; in cervical carcinomas, for example, elevated co-expression of epidermal growth factor receptor (EGFR), VEGF, and mesenchymal marker TWIST2 with loss of E-cadherin was associated with locally advanced cancers and poorer survival [ 192 ]. EMT thus plays critical roles in cancer progression, from invasion and metabolic reprogramming to stemness and angiogenesis, shaping tumor biology and clinical outcomes. Strategies aimed at inhibiting EMT, restoring E-cadherin function, or targeting metabolic vulnerabilities may thus hold significant promise for reducing metastatic burden and improving patient prognoses. The following sections will explore how these insights are translating into biomarker discovery, clinical interventions, and next-generation therapeutic strategies.

Efforts to develop therapies targeting EMT have been hampered by the complexity of EMT pathways and their integration with essential physiological processes [ 264 ]. Identifying the specific factors that drive EMT in pathological settings—while sparing normal tissue remodeling—requires advanced tools that allow precise and systematic discovery of disease-relevant regulators. In this section, we highlight how two emerging technological platforms, CRISPR-based genetic screens and three-dimensional (3D) culture systems, are reshaping our understanding of EMT biology and accelerating the search for novel therapeutic strategies. Small molecules have played a crucial role in drug development, accounting for approximately 74% of FDA-approved drugs between 1981 and 2019 [ 265 ]. Several small molecules targeting epithelial–mesenchymal transition (EMT) have shown promise in slowing both tissue fibrosis and cancer progression under experimental conditions. Compounds such as nintedanib, trametinib, tivantinib, linsitinib, and binimetinib, have been investigated in clinical trials for tumor treatment [ 266 , 267 ]. Among these agents, nintedanib specifically inhibits EMT triggered by TGF-β2 and TNF-α in alveolar epithelial cells. Ihara et al. demonstrated that nintedanib significantly downregulated gene expression linked to EMT-related pathways and TGF-β signaling, with no noticeable effect on TNF-α–mediated pathways [ 268 ]. Hierarchical cluster analysis confirmed that nintedanib markedly reduced EMT-related gene expression, and additional assays revealed suppression of Smad2/3 phosphorylation. Collectively, these findings highlight the ability of nintedanib to interfere with TGF-β–induced EMT processes. Trametinib has also drawn attention for its role in combination therapies. In EGFR-TKI–resistant NSCLC cell lines, Sato et al. tested trametinib (a MEK inhibitor) in combination with taselisib (a PI3K inhibitor) and observed marked suppression of compensatory signaling pathways [ 269 ]. This dual kinase inhibition overcame multiple resistance mechanisms, including MET amplification, EMT, and the EGFR T790M mutation. Further analysis revealed that the treatment activated p38 MAPK signaling, triggering apoptosis. Notably, prolonged drug exposure reversed EMT and restored tumor sensitivity to EGFR-TKIs, suggesting that combined MEK and PI3K blockade may overcome acquired resistance in NSCLC. Tivantinib is a non-ATP-competitive inhibitor of the receptor tyrosine kinase Met, an oncogene and regulator of EMT via multiple signaling pathways [ 270 ]. In a Phase II trial for hepatocellular carcinoma (HCC), tivantinib improved progression-free survival (PFS) but did not enhance overall survival (OS) [ 271 ]. A subsequent Phase III trial comparing tivantinib plus erlotinib to erlotinib monotherapy in EGFR tyrosine kinase inhibitor–naive NSCLC patients similarly showed limited clinical benefit [ 272 ]. Despite these mixed outcomes, ongoing research into Met-targeting strategies underscores the broader potential of small molecules to disrupt EMT and reverse therapy resistance in cancer. CRISPR/Cas systems offer a powerful means of introducing precise genetic perturbations on a genome-wide scale, enabling the unbiased identification of genes that promote or suppress EMT phenotypes [ 273 , 274 ]. While CRISPR approaches are already ubiquitous for functional genomics, the design of pooled screens that couple CRISPR-induced mutations with readouts of cell migration, invasion, or drug resistance has provided new insights into the multifaceted regulation of EMT. Forward genetic screens have uncovered both known EMT mediators (e.g., members of the TGF-β pathway) and less characterized factors implicated in EMT-associated behaviors. Recent work using CRISPR activation libraries in melanoma cells identified SMAD3 , BIRC3 , and SLC9A5 as inducers of a mesenchymal-like, therapy-resistant state [ 275 ]. Similarly, a pooled CRISPR knockout screen in colon cancer cells highlighted core P-body components ( DDX6 , EDC4 ) as negative EMT regulators, showing how post-transcriptional regulation can restrain the EMT program [ 276 ]. Epigenetic control of EMT has also emerged as a key focus. A comprehensive CRISPR screen pinpointed the polycomb repressive complex polycomb repressive complex 2 (PRC2) and the lysine methyltransferase 2D (KMT2D)-COMPASS complex as critical for maintaining epithelial phenotypes or for permitting distinct EMT trajectories in breast cancer models [ 277 ]. Such findings broaden the scope of potential EMT-targeting strategies, suggesting that epigenome modulation may be a promising therapeutic approach. Collectively, these CRISPR-based screens provide a clearer map of the molecular networks that drive EMT, revealing potential targets—such as RNA-binding proteins, epigenetic regulators, and noncanonical signaling molecules—that had not been fully appreciated before. In doing so, they establish a foundation for the next phase of therapeutic discovery. Beyond genetic modifications, novel 3D culture systems (e.g., spheroids, organoids, and microfluidic platforms) are yielding deeper insights into EMT biology and becoming indispensable for the early testing of candidate therapeutics [ 278 ]. These models replicate more physiologically relevant cell–cell and cell–matrix interactions than traditional 2D cultures, enhancing the study of how EMT influences tumor invasiveness, drug responses, and metastatic potential. In ovarian cancer, for example, TGF-β–driven EMT in 3D spheroids sharply increases invasiveness, but pharmacological blockade of TGF-β signaling restores epithelial features [ 279 ]. Comparable findings in cholangiocarcinoma, glioma, and hepatic stem cell models suggest that 3D approaches may facilitate more accurate drug screening and toxicity assessments by capturing EMT’s dynamic influence on cancer cell behavior [ 280 – 282 ]. Importantly, phenotypic assays in 3D contexts enable can enable high-throughput screening offering accurate predictions of how potential EMT-targeting agents will perform in vivo. For example, a recent study employed morphological screening of mesenchymal mammary tumor organoids as a platform to screen for drugs that reverse EMT, identifying multiple class I histone deacetylases (HDACs) inhibitors and Bromodomain inhibitors [ 283 ]. Notably, one of the inhibitors identified was shown to sensitize mesenchymal, chemotherapy resistant tumors to chemotherapy in a mouse model, demonstrating the predictive potential of the organoid platform. Emerging evidence suggests that epigenetic regulators can profoundly influence EMT states and plasticity, rendering them attractive therapeutic targets. CRISPR-based screens have revealed essential roles for chromatin modifiers such as PRC2 and KMT2D-COMPASS in controlling distinct EMT trajectories in breast cancer [ 277 ]. Complementary approaches using 3D organoid systems have further highlighted the promise of epigenetic drug interventions; for example, the drug screen in mesenchymal mammary tumor organoids, described above, identified several families of modulators capable of reversing EMT, including HDAC and Bromodomain inhibitors [ 283 ]. The promising results seen thus far in preclinical models underscore the potential of epigenetic agents to reprogram EMT in clinically meaningful ways. Another emerging frontier focuses on targeting EMT-associated proteolysis. Traditional broad-spectrum MMP inhibitors have shown limited success in clinical trials, partly because they disrupt homeostatic metalloprotease functions with consequent off-target toxicity. However, high-throughput protein engineering strategies such as yeast surface display (YSD) library screening [ 284 , 285 ] enable the development of finely tuned TIMP variants that selectively target pathogenic MMP isoforms. By optimizing TIMP domains for enhanced binding affinity interactions (e.g., achieving a 900-fold increase in MMP-14 binding), researchers can inhibit MMP-3, MMP-9, MMP-14 or other proteases implicated in EMT-driven metastasis with far greater specificity [ 286 – 292 ]. Technologies have also been developed to modify engineered TIMPs for improved pharmacokinetic parameters, facilitating translation as biologic therapies [ 293 , 294 ]. Such precision paves the way for more personalized anti-EMT therapeutics, minimizing off-target effects that hamper conventional MMP-inhibitor regimens. Taken together, these advances in epigenetic targeting and MMP/TIMP engineering exemplify the growing push toward selective interventions that disrupt pathologic EMT while minimizing harm to normal biological processes. Further integrating these approaches with CRISPR-based discovery, 3D organoid screening, and combination therapy design will accelerate progress toward novel, more precise strategies for mitigating EMT-driven disease. By expanding our mechanistic understanding of EMT and refining how we target its key effectors, we can begin to envision therapies that not only halt metastatic spread and fibrotic damage but also preserve or even restore healthy tissue function.

Biomarkers can provide quantifiable indicators that enable earlier detection, more accurate prognosis, and better patient stratification for targeted therapies [ 193 , 194 ]. They can be categorized broadly as diagnostic (for early disease identification and monitoring), prognostic (for assessing outcomes or disease progression), and predictive (for estimating therapeutic responses). In the context of EMT, a range of biomarkers have emerged that help clinicians gauge the degree of epithelial–mesenchymal plasticity within a tumor and thus the likelihood of metastasis, resistance to therapy, or overall clinical aggressiveness. E-cadherin is among the best-characterized of EMT biomarkers. High levels of membrane-bound E-cadherin support epithelial adhesion, whereas soluble E-cadherin (sE-cadherin) produced by proteolytic cleavage reduces cellular adherence and heightens invasive capacity [ 195 , 196 ]. Numerous clinical studies report elevated sE-cadherin as a diagnostic or prognostic indicator in many malignancies, including bladder, kidney, and lung cancers [ 197 – 199 ]. Conversely, low tissue levels of membrane-bound E-cadherin correlate with advanced tumor stages and a higher propensity for metastasis. In colorectal cancer, combining sE-cadherin with classic tumor markers like carcinoembryonic antigen (CEA) enhances diagnostic specificity [ 200 ], and reduced E-cadherin expression is frequently linked to aggressive phenotypes, for example in esophageal and pancreatic malignancies [ 201 , 202 ]. N-cadherin, a canonical mesenchymal cadherin, often rises as E-cadherin falls, underscoring the transition from an epithelial to a mesenchymal state [ 203 ]. Elevated N-cadherin frequently portends increased invasiveness and metastasis in multiple tumors, including those of the prostate, colon, and ovary [ 204 ]. High serum soluble N-cadherin (sN-cadherin) may forecast aggressive disease and modify FGF-receptor and endothelial cell signaling [ 205 ]. Preclinical data suggest that inhibiting N-cadherin can restore chemosensitivity and lessen metastatic burden, especially in resistant tumor models [ 206 ]. Additional mesenchymal markers such as vimentin and fibronectin also correlate strongly with poor prognosis and metastasis in lung, colon, and esophageal cancers, among others [ 207 – 211 ]. Vimentin may also reflect immune evasion when coupled with elevated PD-1/PD-L1 signaling [ 212 ], while fibronectin and other ECM proteins can create pro-invasive niches. Targeting these structural components through small interfering RNA (siRNA) or combination therapy has shown promise in restricting tumor cell migration and bolstering drug responses [ 213 ]. MMPs and their inhibitors (TIMPs) also function as pivotal biomarkers in EMT-related cancers. Elevated MMP-7, MMP-8, MMP-9, TIMP-1, and TIMP-2 levels have each been associated with unfavorable outcomes in colorectal and gastric cancers, as well as in breast carcinoma [ 214 – 218 ]. In breast cancer, for instance, high circulating MMP-9 and TIMP-1 levels, especially when combined with cancer antigen 15-3 (CA 15-3), can refine diagnostic accuracy [ 219 ]. Some of these molecules exhibit context-dependent roles: while increased TIMP-1 or TIMP-2 often correlates with therapy resistance, diminished TIMP-3—due to hypermethylation or underexpression—can foster more aggressive tumor growth in breast and lung malignancies [ 220 – 222 ]. Emerging strategies to upregulate TIMP-3, such as MPT0G013, have shown preclinical efficacy in halting tumor progression and angiogenesis [ 223 , 224 ]. Taken together, these biomarker advances illustrate how EMT profiling has transitioned from a purely research-driven endeavor into a potential clinical toolset. By quantifying key EMT markers, clinicians and researchers can gain insight into a tumor’s invasive capacity, metastatic risk, and treatment responsiveness. In the next section, we discuss various therapeutic strategies aimed at modulating EMT, highlighting how certain biomarkers guide the selection or refinement of anti-EMT treatments.

MMP inhibitors are broadly categorized into classical inhibitors and more recently explored novel approaches, including small molecules and antibody-based therapeutics. Classical inhibitors typically target the MMP catalytic domain, either by directly blocking the active site or by engaging an adjacent allosteric pocket. While some covalent inhibitors have been described, most classical MMP inhibitors act through non-covalent mechanisms. Over the past few decades, intensive research has led to the discovery of numerous small-molecule MMP inhibitors exhibiting varying degrees of potency and selectivity [ 251 , 252 ]. Researchers initially capitalized on the ability of MMPs to degrade both native and denatured collagen. By analyzing enzyme–substrate interactions, they identified a minimal substrate sequence, Ac-Pro-Leu/Gln-Gly-Leu/Ile-Leu/Ala-Gly-OEt, recognized and cleaved by many MMPs at the central amide bond. Early synthetic MMP inhibitors were designed based on this minimal substrate, using the α-chain of collagen as a structural template and replacing the scissile amide bond with a non-cleavable isosteric group. Hydroxamic acid, a potent zinc chelator, quickly emerged as a key structural motif because it bidentately binds the catalytic zinc(II) ion conserved across MMPs. These inhibitors often incorporate specific amino acid sequences to engage the substrate-recognizing groove at either the N- or C-terminal region [ 253 ]. Two prominent hydroxamate-based inhibitors, marimastat and batimastat, advanced into clinical trials but ultimately proved unsuccessful. Batimastat reached phase III trials for malignant pleural effusions but was discontinued owing to poor oral bioavailability and complications such as peritonitis [ 254 , 255 ]. The broader failure of hydroxamic acid-based MMP inhibitors in clinical trials raised concerns about their suitability as strong zinc-binding groups, with issues including low selectivity among MMP isoforms, poor bioavailability, and off-target toxicity due to interference with other metal-dependent enzymes [ 256 ]. To mitigate these drawbacks, researchers have explored alternative zinc-binding groups that reduce excessive metal chelation, facilitating more selective non-covalent interactions between inhibitor and enzyme. Since MMPs in their zymogen form feature a cysteine residue coordinating the catalytic zinc, thiol-based inhibitors also emerged as potential “weak” zinc-binders. One example is rebimastat (Bristol-Myers Squibb), an inhibitor of MMP-2 and MMP-9 that showed promise in Phase I and II trials for early breast cancer. However, it failed to improve survival in Phase III non-small-cell lung cancer studies and led to adverse effects [ 257 , 258 ]. Additional metal-binding groups, including barbiturates and hydantoins, have been investigated for their ability to enhance specificity [ 259 , 260 ]. Overall, MMP inhibitor development has faced significant challenges. Early broad-spectrum inhibitors were unsuccessful due to intolerable side effects stemming from simultaneous inhibition of non-target metalloproteases. The ubiquitous hydroxamate group in first-generation inhibitors strongly chelated zinc(II) across all MMPs, yielding low selectivity and poor bioavailability [ 256 ]. Attempts to develop highly selective inhibitors for individual MMP isoforms have also been hindered by high substrate promiscuity, wherein multiple MMPs can cleave the same substrate. Moreover, many clinical trials have enrolled patients with advanced disease, limiting the apparent effectiveness of MMP-targeting strategies. Complicating matters further, MMPs can play opposing roles depending on the disease context; for instance, MMP-9 may correlate with negative outcomes in colorectal cancer but appear protective in colitis. Moving forward, a deeper understanding of the biological and clinical nuances of MMP function—and more selective pharmacological tools—will be crucial for successful MMP inhibitor therapy [ 261 – 263 ].

Type 3 EMT arises in epithelial tumor cells through genetic and epigenetic alterations that promote malignant transformation and progression [ 140 , 141 ]. In this context, cells within the tumor microenvironment—comprising stromal cells, immune infiltrates, and cancer-associated fibroblasts—release hypoxia-driven factors, pro-inflammatory cytokines, and growth mediators that converge on EMT-related signaling cascades. As the epithelial phenotype is suppressed, master regulatory transcription factors including Snail, Slug, Twist, and Zeb can become upregulated, leading to diminished E-cadherin expression, disruption of intercellular adhesions, and concomitant increases in mesenchymal markers (e.g., vimentin, fibronectin, N-cadherin) [ 142 ]. These molecular shifts not only alter cytoskeletal organization and cell polarity but also enhance proteolytic capabilities, creating an environment conducive to invasion. The resulting EMT phenotype can give rise to cancer stem cells that resist chemotherapy and radiotherapy while evading immune surveillance, thereby fostering tumor aggressiveness [ 143 ]. A central driver of EMT in solid tumors is hypoxia, which often prevails in poorly vascularized tumor regions where oxygen levels can drop considerably below normal tissue levels. Hypoxia inactivates prolyl hydroxylases, stabilizing HIF-α. Stabilized HIF-α in turn activates signal transduction pathways such as TGF-β, Wnt/β-catenin, Hedgehog, and PI3K/Akt, leading to increased expression of pivotal EMT regulators such as Zeb, Snail1, and B-cell-specific Moloney murine leukemia virus integration site 1 (BMI1) [ 77 , 144 – 148 ]. Moreover, hypoxia profoundly reshapes the tumor immune landscape by inhibiting T- and NK-cell infiltration while recruiting immunosuppressive cell types—myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), and T-regulatory cells—to these low-oxygen niches [ 77 , 149 ]. In response to hypoxia, TAMs can secrete cytokines that amplify EMT, including TNFα, IL-1, IL-6, and CCL2, thereby fostering tumor cell dissemination [ 82 , 150 , 151 ]. HIF-1 signaling also drives the expression of PD-L1 in both tumor cells and infiltrating immune cells, establishing a more immunosuppressive microenvironment and fueling tumor proliferation [ 152 ]. Thus, EMT induction in cancer depends critically on microenvironmental cues, notably hypoxia and inflammatory signals. Because Type 3 EMT drives local tissue invasion, dissemination, and therapy resistance, understanding its molecular underpinnings is critical for developing strategies that halt tumor progression at earlier, more treatable stages. The next section examines how this EMT program transitions into the processes of cancer progression, metastasis, metabolic reprogramming, and acquisition of stemness, all of which further complicate effective treatment.

MMPs directly drive EMT by reshaping the microenvironment and activating pro-EMT signaling networks (Fig.  3 ) [ 16 ]. Their ability to degrade collagen and laminin remodels basement membranes [ 83 ], which allows epithelial cells to detach and assume mesenchymal attributes. The liberation of embedded signaling factors, such as TGF-β, furthers this transition by binding to epithelial receptors and triggering SMAD-dependent transcription of EMT-related genes [ 84 ]. Similarly, MMP cleavage of membrane-bound Epidermal growth factor (EGF) precursors augments mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Protein kinase B (AKT) pathways, reinforcing the cells’ shift toward a migratory phenotype [ 85 , 86 ]. Fig. 3 Principal extracellular stimuli and intracellular pathways that drive epithelial–mesenchymal transition (EMT). Hypoxia, inflammatory cytokines (e.g., IL-6), and growth factors (e.g., TGF-β, EGF) converge on multiple signaling cascades, including RhoA/ROCK, Smad-dependent transcription, Ras/MAPK/ERK, PI3K/Akt, Wnt/β-catenin, Notch, and Sonic Hedgehog (SHH). These pathways coordinate the upregulation of EMT-inducing transcription factors (Zeb, Snail1/2, Slug, Twist), which repress epithelial genes (E-cadherin, Occludin, Claudin) and induce mesenchymal genes (N-cadherin, Vimentin, Fibronectin). The resulting loss of cell–cell junctions, cytoskeletal reorganization, and acquisition of migratory properties enables cells to transition from a polarized epithelial state to an invasive mesenchymal state. Additionally, integrin-mediated signals and NF-κB activation reinforce pro-EMT transcriptional programs, while hypoxia-inducible factor 1α (HIF-1α) further modulates EMT under low-oxygen conditions. Collectively, these interactions establish a dynamic process that can be reversed (MET) under specific conditions, underscoring the plasticity of epithelial and mesenchymal phenotypes in both normal development and disease. (Illustration created with BioRender.com) Principal extracellular stimuli and intracellular pathways that drive epithelial–mesenchymal transition (EMT). Hypoxia, inflammatory cytokines (e.g., IL-6), and growth factors (e.g., TGF-β, EGF) converge on multiple signaling cascades, including RhoA/ROCK, Smad-dependent transcription, Ras/MAPK/ERK, PI3K/Akt, Wnt/β-catenin, Notch, and Sonic Hedgehog (SHH). These pathways coordinate the upregulation of EMT-inducing transcription factors (Zeb, Snail1/2, Slug, Twist), which repress epithelial genes (E-cadherin, Occludin, Claudin) and induce mesenchymal genes (N-cadherin, Vimentin, Fibronectin). The resulting loss of cell–cell junctions, cytoskeletal reorganization, and acquisition of migratory properties enables cells to transition from a polarized epithelial state to an invasive mesenchymal state. Additionally, integrin-mediated signals and NF-κB activation reinforce pro-EMT transcriptional programs, while hypoxia-inducible factor 1α (HIF-1α) further modulates EMT under low-oxygen conditions. Collectively, these interactions establish a dynamic process that can be reversed (MET) under specific conditions, underscoring the plasticity of epithelial and mesenchymal phenotypes in both normal development and disease. (Illustration created with BioRender.com) These proteolytic effects converge on master regulators including ZEB, Snail, and Twist, which repress epithelial markers like E-cadherin while inducing mesenchymal markers such as N-cadherin and vimentin [ 67 ]. MMP-mediated cleavage of E-cadherin can disrupt epithelial adherens junctions and produce fragments that themselves enhance mesenchymal behaviors [ 87 – 89 ]. Concurrently, the degradation of ECM components alters integrin engagement, activates focal adhesion kinases (FAK) and SRC, and amplifies pro-EMT feedback loops [ 24 ]. Under hypoxic conditions, stabilized hypoxia-inducible factors (HIFs) can upregulate MMP expression, further accelerating EMT by potentiating Snail and other transcription factors that dismantle epithelial polarity [ 77 ]. Inflammatory mediators such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) can also boost MMP production, thereby linking chronic inflammation to tumor invasiveness and fibrogenesis [ 90 , 91 ]. Distinct MMPs may exhibit specialized functions in different cancer types or stages of disease progression. For example, MMP-13 degrades collagen types I and IV, facilitating invasive growth in metastasis [ 92 – 94 ], while MMP-15 can break down E-cadherin and zonula occludens-1 (ZO-1), enabling colorectal cancer cells to dissociate [ 95 ]. MMP-14 not only cleaves basement membrane constituents but also upregulates Twist and ZEB in oral squamous cell carcinoma, contributing to the downregulation of E-cadherin (CDH1) [ 96 ]. In breast and lung cancer, MMP-3 and MMP-9 stimulate Snail and Vimentin expression, while MMP-3 may further enhance EMT by promoting NF-κB subunit binding to the Snail promoter [ 97 – 99 ]. Finally, pathways such as Wnt/β-catenin and TGF-β are themselves modulated by MMPs. MMP-3 can act as both a target and an effector of Wnt signaling, freeing β-catenin from adherens junctions and promoting its transcriptional activities [ 100 ]. MMP-2, MMP-9, and MMP-14 can similarly amplify TGF-β signaling in prostate cancer, lung cancer, and glioblastoma cells, creating a positive feedback loop that drives metastatic spread [ 101 – 103 ]. By either upregulating or cleaving these growth factors and their receptors, MMPs integrate multiple signaling axes essential for the acquisition of mesenchymal phenotypes. This centrality underscores the potential benefit of targeting the MMP–EMT axis to combat cancer metastasis and fibrotic diseases, a theme explored in subsequent sections on emerging therapeutic strategies.

The ECM is a highly dynamic and complex network of macromolecules that provides both structural and biochemical support to surrounding cells [ 17 ]. It consists of a diverse array of proteins, glycoproteins, proteoglycans, and glycosaminoglycans, collectively orchestrating fundamental cellular behaviors including proliferation, differentiation, migration, and survival [ 18 ]. Key structural components of ECM include fibrillar proteins such as collagen, elastin, and fibronectin, along with proteoglycans and glycosaminoglycans like hyaluronan and heparan sulfate, which modulate ECM viscosity, hydration, and bioactivity [ 19 ]. Structurally, the ECM is organized into two main compartments: the basement membrane and the interstitial matrix [ 20 ]. The basement membrane, predominantly composed of collagen type IV, laminins, nidogen, and proteoglycans, supports epithelial and endothelial cell layers, maintains cell polarity, and acts as a barrier to cell migration [ 21 ]. The interstitial matrix, largely consisting of fibrillar collagens (types I, III), fibronectin, elastin, and various proteoglycans, provides structural integrity and regulates cell migration, proliferation, and differentiation [ 22 ]. Controlled remodeling of the ECM is essential for tissue repair, morphogenesis, and cell signaling. Dysregulated ECM turnover, however, contributes significantly to pathologies such as fibrosis, inflammation, and cancer [ 23 ]. In cancer specifically, ECM remodeling facilitates tumor cell invasion, metastasis, and therapy resistance, in part by creating a permissive microenvironment for EMT [ 24 ]. Moreover, ECM components can directly influence cell behavior through integrin receptors and growth factor signaling pathways. Alterations in ECM stiffness, composition, and architecture profoundly affect cancer cell behavior by promoting EMT, angiogenesis, and metastasis [ 25 ]. Consequently, understanding ECM structure and biology provides valuable insights into tumor progression and potential therapeutic targets aimed at modulating ECM dynamics. EMT is a dynamic process in which epithelial cells, normally exhibiting apical–basal polarity and stable cell–cell contacts, undergo profound morphological and molecular changes to acquire mesenchymal attributes that promote motility and invasiveness [ 26 , 27 ]. In physiological contexts such as embryonic development and tissue repair, these events are tightly orchestrated to ensure proper morphogenesis [ 8 , 28 ]. When abnormally activated, however, EMT drives pathological phenomena including fibrosis and metastatic spread. During EMT, epithelial junctional complexes, including tight and adherens junctions, are downregulated or reorganized, ultimately disrupting apical–basal polarity [ 29 , 30 ]. Concomitantly, cells adopt spindle-like morphologies, upregulate mesenchymal markers (e.g., N-cadherin, vimentin, fibronectin), and gain both heightened motility and resistance to cell death [ 31 – 33 ]. These phenotypic shifts are largely governed by transcription factors such as Snail, Slug, Twist, and the ZEB family, which repress epithelial genes and induce mesenchymal programs, often in response to dysregulated signals like TGF-β, Wnt, or Notch [ 4 , 34 , 35 ]. EMT has been categorized into three main subtypes, each shaped by distinct stimuli and outcomes (Fig.  1 ). In embryonic development, exemplified by gastrulation and neural crest cell migration, the transient loss of epithelial characteristics permits cell delamination and differentiation into diverse lineages [ 2 , 27 ]. During wound healing and tissue repair, a partial form of EMT enables epithelial cells to migrate over injury sites and facilitate tissue regeneration; when prolonged, this process can lead to pathological scarring [ 28 , 36 ]. In fibrotic conditions like pulmonary fibrosis or cirrhosis, this form of EMT persists and generates large populations of fibroblast-like cells that secrete excessive extracellular matrix, ultimately compromising organ structure and function [ 37 , 38 ]. Finally, cancer-associated EMT drives tumor progression and metastasis, conferring to tumor cells the ability to invade, resist apoptosis, and evade standard therapies [ 39 , 40 ]. A thorough understanding of these EMT subtypes not only elucidates fundamental developmental events but also guides the development of therapeutic strategies in disease contexts. Fig. 1 Overview of the three major EMT subtypes—Type 1 (embryogenesis), Type 2 (wound healing), and Type 3 (cancer metastasis)—and how each relies on a dynamic balance between epithelial–mesenchymal transition (EMT) and mesenchymal–epithelial transition (MET). In Type 1 EMT, shown in the upper panels, epithelial cells in the early embryo undergo EMT during gastrulation to form the three germ layers (ectoderm, mesoderm, endoderm). Further rounds of EMT–MET underlie critical morphogenetic events, such as neural crest cell formation, enabling the development of tissues including craniofacial structures and peripheral nerves. In Type 2 EMT, depicted in the middle panels, epithelial cells participate in wound repair, briefly adopting a mesenchymal phenotype to migrate into the injury site and facilitate inflammation, proliferation, and remodeling. Dysregulation at this stage can promote pathological scarring or fibrosis. Finally, Type 3 EMT (bottom panels) illustrates the metastatic cascade in cancer. Epithelial tumor cells lose cell–cell junctions and apical–basal polarity, acquire invasive properties (EMT), intravasate into the bloodstream as circulating tumor cells (CTCs), and survive hematogenous or lymphatic transit. Upon reaching distant organs, they typically undergo MET to colonize the new microenvironment and form secondary tumors. Ultimately, each subtype of EMT utilizes similar molecular machinery—transcription factors, signaling pathways, and ECM remodeling—but serves distinct biological ends, from normal development and tissue homeostasis to malignant progression and metastasis. (Illustration created with BioRender.com) Overview of the three major EMT subtypes—Type 1 (embryogenesis), Type 2 (wound healing), and Type 3 (cancer metastasis)—and how each relies on a dynamic balance between epithelial–mesenchymal transition (EMT) and mesenchymal–epithelial transition (MET). In Type 1 EMT, shown in the upper panels, epithelial cells in the early embryo undergo EMT during gastrulation to form the three germ layers (ectoderm, mesoderm, endoderm). Further rounds of EMT–MET underlie critical morphogenetic events, such as neural crest cell formation, enabling the development of tissues including craniofacial structures and peripheral nerves. In Type 2 EMT, depicted in the middle panels, epithelial cells participate in wound repair, briefly adopting a mesenchymal phenotype to migrate into the injury site and facilitate inflammation, proliferation, and remodeling. Dysregulation at this stage can promote pathological scarring or fibrosis. Finally, Type 3 EMT (bottom panels) illustrates the metastatic cascade in cancer. Epithelial tumor cells lose cell–cell junctions and apical–basal polarity, acquire invasive properties (EMT), intravasate into the bloodstream as circulating tumor cells (CTCs), and survive hematogenous or lymphatic transit. Upon reaching distant organs, they typically undergo MET to colonize the new microenvironment and form secondary tumors. Ultimately, each subtype of EMT utilizes similar molecular machinery—transcription factors, signaling pathways, and ECM remodeling—but serves distinct biological ends, from normal development and tissue homeostasis to malignant progression and metastasis. (Illustration created with BioRender.com) MMPs are zinc-dependent endopeptidases indispensable for remodeling the ECM in both healthy and diseased states [ 41 , 42 ]. They are produced as inactive zymogens, where the propeptide domain blocks the active site through a cysteine switch mechanism; disruption of this mechanism leads to enzyme activation. The catalytic domain, which contains a highly conserved zinc-binding motif (HEXGHXXGXXH), mediates substrate cleavage and ECM degradation. Many MMPs also possess a hinge region that provides flexibility between domains, influencing substrate recognition and activity. Most MMPs (except matrilysins) contain a hemopexin-like domain that regulates substrate binding and protein–protein interactions, while membrane-type MMPs (MT-MMPs) feature an additional transmembrane or glycosylphosphatidylinositol anchor domain for localization to the cell surface. Some MMPs, notably the gelatinases (MMP-2 and MMP-9), also have fibronectin-like repeats to enhance binding to gelatin and collagen fragments [ 43 , 44 ]. Beyond degrading collagens, fibronectin, and laminins, MMPs can cleave non-matrix substrates such as bound growth factors, integrins, and cadherins [ 45 – 49 ]. By modulating these molecules, MMPs influence cell proliferation, differentiation, adhesion, and tissue architecture. They also cleave certain cytokines and chemokines, thus shaping inflammatory responses and immune cell recruitment [ 50 ]. Under normal conditions, MMP activity is highly restricted by transcriptional control, compartmentalization, zymogen activation, and inhibition by TIMPs [ 51 , 52 ]. Disruption of this regulatory balance can initiate or exacerbate pathologies such as metastatic cancer, arthritis, cardiovascular disease, and neurodegenerative disorders (Table  1 and Fig.  2 ). Table 1 Major MMP isoforms, their key substrates, and roles in EMT-related pathologies MMP isoform Key substrates Roles in EMT Representative pathologies/References MMP-1 Collagen types I, II, III; fibrin; fibronectin Degrades interstitial collagens; remodels ECM to facilitate epithelial cell detachment and fibroblast activation; can contribute to wound-healing EMT but also to pathological scarring Fibrosis (Skin, Keloids): [ 135 , 136 , 295 ] Cancer Invasion: [ 70 , 218 , 296 – 299 ] MMP-2 Collagen IV, gelatin, laminin, fibronectin Degrades basement membranes; releases latent TGF-β; upregulated in cells undergoing EMT; crucial in basement membrane breakdown Kidney Fibrosis: [ 121 , 300 ] Lung Fibrosis: [ 123 , 125 , 301 , 302 ] Cardiac Remodeling: [ 131 , 303 , 304 ] Cancer Invasion: [ 61 , 62 , 302 , 305 – 308 ] MMP-3 Casein, laminin, fibronectin, E-cadherin Cleaves E-cadherin, enhancing mesenchymal traits; activates Rac1b and induces oxidative stress, driving Snail/Vimentin expression; can potentiate NF-κB binding to Snail promoter Breast Cancer: [ 97 – 99 , 309 – 311 ] Lung Fibrosis: [ 98 , 312 , 313 ] Branching Morphogenesis: [ 314 ] EMT in Wnt Signaling: [ 100 , 315 ] Cancer Cell Invasion: [ 99 , 289 , 316 – 324 ] MMP-7 Proteoglycans, elastin, casein, E-cadherin Known as matrilysin; can cleave E-cadherin, promoting loss of cell–cell contacts; implicated in tumor progression and fibrotic tissue remodeling Lung Fibrosis (IPF): [ 126 , 128 , 325 – 327 ] Liver Cirrhosis/Biliary Atresia: [ 328 , 329 ] [ 330 , 331 ] CRC Detection (with CEA): [ 332 ] Cancer Invasion [ 215 , 333 – 335 ]: MMP-8 Collagen type I, casein, fibrinogen Primarily degrades type I collagen; can influence inflammatory cell infiltration; plays a context-dependent and sometimes protective role in both fibrosis and cancer invasion Cystic Fibrosis: [ 125 ] Liver Cirrhosis: [137{Hu, 2023 #448]} Cancer Invasion [ 336 , 337 ] MMP-9 Collagen IV, gelatin, elastin, osteopontin Degrades basement membrane collagen; liberates TGF-β; critical in inflammatory cell recruitment; implicated in tumor invasion and fibrotic changes Kidney Fibrosis: [ 122 , 338 – 340 ] Lung Fibrosis: [ 301 , 341 – 345 ] Cardiac Remodeling: [ 132 ] Cancer (Breast, CRC): [ 219 , 291 , 332 , 346 – 348 ] MMP-10 Elastin, fibronectin, casein Sometimes called stromelysin-2; degrades ECM proteins, facilitating remodeling; implicated in fibroproliferative processes and tumor invasion Lung Fibrosis (IPF): [ 127 ] Lung Cancer: [ 349 – 354 ] MMP-12 Elastin, fibronectin, laminin Macrophage elastase; particularly important in inflammatory processes and macrophage infiltration; can degrade elastin in granulomatous lesions Fibrosis: [ 355 – 358 ] Atherosclerosis: [ 359 – 362 ] MMP-13 Collagen types I, II, IV; fibronectin Cleaves interstitial collagen; overexpressed in multiple cancers, supporting invasive growth and metastasis; enhances mesenchymal phenotype Cancer Progression (Breast, Prostate): [ 92 – 94 ] EMT Induction: [ 363 ] MMP-14 (MT1-MMP) Collagen I, II, III; laminin, fibronectin, proMMP-2 activation Membrane-type MMP; cleaves various ECM components and activates proMMP-2; promotes cell migration and invasion by targeting junctional proteins (E-cadherin, integrins); upregulates EMT-TFs (Twist, ZEB) Breast Cancer Migration: [ 101 ] Oral Squamous Carcinoma: [ 96 , 364 ] Fibrosis (Myocardial, Hepatic): [ 365 , 366 ] MMP-15 (MT2-MMP) Collagen, gelatin, ZO-1, E-cadherin A membrane-type MMP capable of degrading junctional proteins (e.g., ZO-1, E-cadherin), thus facilitating EMT and local invasion Colorectal Cancer: [ 95 , 101 ] IPF: Idiopathic pulmonary fibrosis; CF: Cystic fibrosis; MI: Myocardial infarction; EMT-TFs: Epithelial–mesenchymal transition transcription factors Fig. 2 Matrix Metalloproteinases (MMPs) and Their Roles in Human Disease. In cancer, MMPs drive tumor invasion, metastasis, and immune evasion by degrading ECM components and activating growth factors, with MMP-1, MMP-2, MMP-3, MMP-9, and MMP-14 playing key roles. In cardiovascular diseases, MMP-2 and MMP-9 contribute to arterial ECM breakdown, fibrosis, and ventricular remodeling, increasing the risk of aneurysms and rupture. In neurodegenerative disorders, MMP-2, MMP-3, MMP-8, and MMP-9 disrupt the blood–brain barrier, induce neuroinflammation, and facilitate immune cell infiltration, contributing to conditions like Alzheimer’s disease and multiple sclerosis. In lung diseases, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-12, and MMP-13 promote ECM remodeling, fibrosis, and alveolar destruction, leading to COPD and pulmonary fibrosis. MMPs also play a role in diabetes mellitus by degrading pancreatic islet ECM and promoting β-cell apoptosis, impairing insulin production. In gynecological diseases, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, and MMP-13 contribute to ovarian cancer metastasis, tumor angiogenesis, and endometriosis progression. MMPs further contribute to autoimmune diseases by driving joint cartilage breakdown in rheumatoid arthritis and worsening inflammation. In ophthalmic diseases, they facilitate ECM degradation and neovascularization, leading to conditions such as diabetic retinopathy and age-related macular degeneration. (Illustration created with BioRender.com) Major MMP isoforms, their key substrates, and roles in EMT-related pathologies Fibrosis (Skin, Keloids): [ 135 , 136 , 295 ] Cancer Invasion: [ 70 , 218 , 296 – 299 ] Kidney Fibrosis: [ 121 , 300 ] Lung Fibrosis: [ 123 , 125 , 301 , 302 ] Cardiac Remodeling: [ 131 , 303 , 304 ] Cancer Invasion: [ 61 , 62 , 302 , 305 – 308 ] Breast Cancer: [ 97 – 99 , 309 – 311 ] Lung Fibrosis: [ 98 , 312 , 313 ] Branching Morphogenesis: [ 314 ] EMT in Wnt Signaling: [ 100 , 315 ] Cancer Cell Invasion: [ 99 , 289 , 316 – 324 ] Lung Fibrosis (IPF): [ 126 , 128 , 325 – 327 ] Liver Cirrhosis/Biliary Atresia: [ 328 , 329 ] [ 330 , 331 ] CRC Detection (with CEA): [ 332 ] Cancer Invasion [ 215 , 333 – 335 ]: Cystic Fibrosis: [ 125 ] Liver Cirrhosis: [137{Hu, 2023 #448]} Cancer Invasion [ 336 , 337 ] Kidney Fibrosis: [ 122 , 338 – 340 ] Lung Fibrosis: [ 301 , 341 – 345 ] Cardiac Remodeling: [ 132 ] Cancer (Breast, CRC): [ 219 , 291 , 332 , 346 – 348 ] Lung Fibrosis (IPF): [ 127 ] Lung Cancer: [ 349 – 354 ] Fibrosis: [ 355 – 358 ] Atherosclerosis: [ 359 – 362 ] Cancer Progression (Breast, Prostate): [ 92 – 94 ] EMT Induction: [ 363 ] MMP-14 (MT1-MMP) Collagen I, II, III; laminin, fibronectin, proMMP-2 activation Membrane-type MMP; cleaves various ECM components and activates proMMP-2; promotes cell migration and invasion by targeting junctional proteins (E-cadherin, integrins); upregulates EMT-TFs (Twist, ZEB) Breast Cancer Migration: [ 101 ] Oral Squamous Carcinoma: [ 96 , 364 ] Fibrosis (Myocardial, Hepatic): [ 365 , 366 ] MMP-15 (MT2-MMP) IPF: Idiopathic pulmonary fibrosis; CF: Cystic fibrosis; MI: Myocardial infarction; EMT-TFs: Epithelial–mesenchymal transition transcription factors Matrix Metalloproteinases (MMPs) and Their Roles in Human Disease. In cancer, MMPs drive tumor invasion, metastasis, and immune evasion by degrading ECM components and activating growth factors, with MMP-1, MMP-2, MMP-3, MMP-9, and MMP-14 playing key roles. In cardiovascular diseases, MMP-2 and MMP-9 contribute to arterial ECM breakdown, fibrosis, and ventricular remodeling, increasing the risk of aneurysms and rupture. In neurodegenerative disorders, MMP-2, MMP-3, MMP-8, and MMP-9 disrupt the blood–brain barrier, induce neuroinflammation, and facilitate immune cell infiltration, contributing to conditions like Alzheimer’s disease and multiple sclerosis. In lung diseases, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, MMP-12, and MMP-13 promote ECM remodeling, fibrosis, and alveolar destruction, leading to COPD and pulmonary fibrosis. MMPs also play a role in diabetes mellitus by degrading pancreatic islet ECM and promoting β-cell apoptosis, impairing insulin production. In gynecological diseases, MMP-1, MMP-2, MMP-3, MMP-7, MMP-9, and MMP-13 contribute to ovarian cancer metastasis, tumor angiogenesis, and endometriosis progression. MMPs further contribute to autoimmune diseases by driving joint cartilage breakdown in rheumatoid arthritis and worsening inflammation. In ophthalmic diseases, they facilitate ECM degradation and neovascularization, leading to conditions such as diabetic retinopathy and age-related macular degeneration. (Illustration created with BioRender.com) MMPs are classified into subgroups based on their structural domains and substrate preferences [ 53 ]. Collagenases (MMP-1, -8, -13) primarily degrade fibrillar collagen types I, II, and III [ 54 ], whereas gelatinases (MMP-2 and MMP-9) target gelatin and collagen type IV [ 55 ]. Stromelysins (MMP-3, -10, -11) exhibit broader substrate specificity, acting upon diverse ECM components including proteoglycans and laminins [ 56 ]. Matrilysins (MMP-7, -26) lack the hemopexin-like domain and display unique substrate profiles [ 57 ], while MT-MMPs (e.g., MMP-14, -15, -16, -17) anchor to the cell surface and facilitate pericellular ECM degradation and activation of other pro-MMPs [ 58 ]. In cancer, specific MMP isoforms facilitate tumor cell invasion, metastasis, and resistance to therapy through ECM remodeling, release of sequestered growth factors, and modulation of cell signaling pathways [ 59 ]. Within the EMT program, MMPs act by altering the extracellular environment and directly modulating cell–cell and cell–matrix adhesions. By degrading collagen, fibronectin, and other basement membrane components, MMPs enable epithelial cells to dissociate from their basal attachments and adopt mesenchymal traits [ 15 , 60 – 62 ]. Beyond ECM degradation, MMPs enhance EMT signaling by freeing latent growth factors such as TGF-β [ 63 – 66 ], which intensify the transcriptional cascades driving mesenchymal gene expression. MMP-mediated cleavage of E-cadherin and integrins further disrupts epithelial architecture and fosters increased motility [ 67 , 68 ]. Consequently, MMPs stand at the intersection of structural ECM remodeling and the biochemical pathways that orchestrate EMT in both developmental and disease contexts [ 69 ]. EMT is a critical biological process during which epithelial cells lose their characteristic polarity, tight junctions, and cell–cell adhesion properties, adopting a mesenchymal phenotype characterized by enhanced migratory and invasive abilities [ 1 , 70 ]. During EMT, epithelial cells undergo profound morphological changes, characterized by transformation into spindle-shaped mesenchymal cells [ 70 ]. This transition involves the downregulation of epithelial markers such as E-cadherin, occludin, and cytokeratins, alongside the simultaneous upregulation of mesenchymal markers including N-cadherin, vimentin, and fibronectin, often accompanied by profound morphological changes such as the formation of spindle-shaped cells [ 2 , 71 ]. Key transcription factors orchestrating these changes include Snail, Slug, Twist, and Zeb proteins, which repress epithelial gene expression and promote mesenchymal phenotypes [ 72 ]. Multiple signaling pathways, notably TGF-β, Wnt/β-catenin, and Notch pathways, drive EMT initiation and maintenance across various cancer types [ 73 – 75 ]. TGF-β signaling, often through SMAD-dependent pathways, is a potent inducer of EMT, suppressing epithelial markers and activating mesenchymal gene expression [ 76 ]. Additionally, hypoxic conditions commonly found within tumor microenvironments stabilize HIFs, further reinforcing EMT through increased transcriptional activation of mesenchymal genes [ 77 ]. Mesenchymal-to-epithelial transition (MET), the reverse of EMT, is crucial for metastatic colonization: mesenchymal tumor cells revert to an epithelial state, re-expressing epithelial markers, regaining polarity, and reducing mesenchymal markers, thereby facilitating outgrowth at distant sites [ 78 – 80 ]. Clinically, the extent of EMT in tumors correlates with aggressive tumor behavior, increased metastatic potential, resistance to chemotherapy and radiation, and poor overall prognosis [ 81 ]. Tumors displaying significant EMT characteristics are often associated with advanced disease stages, greater invasiveness, and reduced therapeutic responsiveness [ 82 ]. By elucidating the dynamic interplay between EMT and MET, researchers aim to develop therapies that limit metastasis, enhance treatment efficacy, and overcome therapy resistance in diverse cancer types.

EMT embodies a tightly regulated program that underpins pivotal developmental and regenerative events yet becomes deleterious when aberrantly activated, contributing to pathological fibrosis, chronic inflammation, and cancer metastasis. Throughout this review, we have highlighted the indispensable role of MMPs in catalyzing and sustaining EMT by remodeling the extracellular matrix and amplifying pro-EMT signaling cascades. Excessive MMP activity, particularly from isoforms such as MMP-2, MMP-9, and MMP-14 (MT1-MMP), can tip the balance from beneficial tissue renewal to disruptive tissue transformation. A growing understanding of the nuanced interplay between EMT and MMPs has led to the identification of numerous therapeutic opportunities. Targeted modulation of MMP expression or activity has shown promise in reducing fibrotic progression and bolstering the effectiveness of conventional anticancer therapies. Innovations including protein engineering of novel biologics are driving an era of precision interventions, while advanced 3D culture models and CRISPR screening technologies are providing unprecedented clarity on the spatiotemporal dynamics of EMT and complex interplay of mediators involved, in both physiological and pathological contexts. Despite these gains, significant gaps persist. MMP inhibitor specificity remains challenging, as broad-spectrum approaches risk off-target toxicity. Moreover, the exact contribution of MMPs to EMT plasticity—particularly during MET—is still poorly understood. Equally critical is defining how immune cells, stromal components, and other tumor microenvironmental factors influence MMP-driven EMT. Addressing these issues will require integrative multi-omics analyses, high-resolution imaging to capture EMT in real time, and the use of organoid models that accurately reflect tumor–stroma interactions. Furthermore, CRISPR-based manipulation of MMP genes and customized protease engineering could yield next-generation inhibitors with refined selectivity, ultimately improving clinical outcomes. These developments provide the possibility of designing novel, minimally invasive treatments capable of halting EMT-driven disease at its root cause. Achieving this goal will require continued exploration of MMP–EMT interactions, a deeper appreciation for the distinct microenvironmental factors that govern pathological versus physiological EMT, and careful validation of emerging strategies in preclinical and clinical settings. If successful, these efforts hold the potential to transform care for a wide range of conditions—from organ fibrosis to metastatic cancers—while preserving the essential functions of EMT in normal tissue development and repair.

Mounting evidence points to EMT as a driving force behind metastatic spread, therapy resistance, and negative clinical outcomes in cancer. Consequently, interventions designed to block or reverse EMT are gaining traction, offering new avenues for improving patient survival [ 225 , 226 ]. Traditional cytotoxic therapies—chemotherapy, radiation, immunotherapy—often prove less effective when EMT accelerates, because mesenchymal-like cells demonstrate heightened drug efflux, suppressed apoptosis, and capacity for immune evasion. Multiple approaches focus on inhibiting transcription factors and signaling pathways essential to EMT. Blocking Zeb1, for instance, can restore E-cadherin levels in chemoresistant ovarian cancer cells and restore sensitivity to taxanes. Epigenetic modulators, including histone deacetylase inhibitors, have shown promise in non-small cell lung cancer NSCLC by reinstating E-cadherin expression and boosting gefitinib efficacy [ 227 ]. Meanwhile, natural compounds like thymoquinone, resveratrol, and piperlongumine inhibit transcriptional drivers like Snail, Twist, and Zeb, reducing cell invasion and metastasis in preclinical models [ 228 – 232 ]. Because MMPs and TIMPs can modulate both ECM remodeling and EMT, therapies targeting these molecules can be potent complements to traditional regimens. Elevated TIMP-1 in some tumors correlates with reduced chemotherapy response; conversely, downregulation of TIMP-1 or TIMP-2 in specific contexts heightens drug sensitivity [ 233 – 236 ]. Moreover, inhibiting key MMPs (e.g., MMP-2, MMP-14) can enhance the cytotoxic effectiveness of chemotherapies by mitigating ECM-driven resistance mechanisms [ 237 , 238 ]. MMPs can also impact the toxicity of radiation therapy. In breast cancer patients, high MMP-3 and MMP-9 levels were found to correlate with radiation-induced toxicities [ 239 ]. Studies in preclinical models likewise find upregulation of certain MMPs by animal irradiation; among these, MMP-2 appeared to play a role in the pathobiology of gastrointestinal toxicities [ 240 ]. These studies suggest the possibility that modulating MMPs may have the capability to simultaneously alleviate adverse effects of therapy and improve therapeutic outcomes [ 241 , 242 ]. EMT-linked drug resistance frequently involves augmented ATP-binding cassette (ABC) transporter activity, activated survival pathways, or inhibited apoptosis. Common chemotherapy agents like paclitaxel or doxorubicin can select for cells that overexpress ABC transporters (ABCB1, ABCC1, ABCC2), drastically diminishing intracellular drug accumulation [ 243 – 245 ]. Genes like Hairy and enhancer of split-1 (HES1) and laminin subunit gamma 2 (LAMC2) drive chemotherapy resistance by upregulating transporters and shielding cells from apoptosis [ 246 , 247 ]. In ovarian cancer cells, Snail and Slug promote both radioresistance and chemoresistance by inhibiting p53-mediated apoptosis and conferring a stem-like phenotype; interference with either factor can restore sensitivity to killing [ 248 ]. In breast cancer, populations of tumor cells undergoing EMT enhance resistance to cyclophosphamide, and reverting these cells to a more epithelial state, such as by miR-200 overexpression, can abrogate this effect [ 249 ]. Additionally, in NSCLC models, blocking Myeloid cell leukemia-1 (MCL-1), a B-cell lymphoma 2 (Bcl-2) family member induced by TGF-β–mediated EMT, has reversed drug resistance, highlighting how targeting EMT-related survival pathways can improve therapeutic outcomes [ 250 ]. Collectively, these findings underscore that effective anti-EMT therapies must target not only the transcriptional machinery driving mesenchymal transitions but also the proteolytic and metabolic pathways that confer chemoresistance. The interplay among signaling cascades, ECM remodeling, and drug efflux mechanisms demands a multifaceted strategy. In the subsequent sections, we examine the newest approaches for defining EMT targets and developing targeted therapies, and how they may refine our ability to block pathologic EMT while preserving its physiologically indispensable roles.

Epithelial–mesenchymal transition (EMT) is a coordinated cellular reprogramming event in which epithelial cells, characteristically polarized and tightly adherent, adopt the migratory and invasive behavior of mesenchymal cells [ 1 ]. This transformation involves extensive changes in cell morphology and signaling networks, ultimately driving shifts in gene expression and cytoskeletal dynamics [ 2 , 3 ]. Although the core features of EMT can be broadly categorized as loss of cell–cell adhesion, acquisition of mesenchymal markers, and cytoskeletal remodeling, these processes arise through an interplay of molecular pathways that converge on key transcription factors such as Snail, Slug, Twist, and ZEB proteins [ 4 – 7 ]. Under physiological conditions, EMT underlies essential developmental steps—most notably during embryogenesis, when tissues and organs form through controlled cycles of epithelial–mesenchymal plasticity [ 8 ]. It also contributes to wound healing and tissue regeneration, where partial and reversible forms of EMT enable epithelial cells to migrate and repair damaged areas [ 9 ]. When improperly regulated, however, this same program can promote a range of diseases. Excessive or persistent EMT has been implicated in tumor progression and metastasis, where malignant epithelial cells dismantle their cell–cell contacts and acquire the capacity to invade, intravasate, and colonize distant tissues [ 10 ]. Similarly, in fibrotic disorders, prolonged EMT leads to an overabundance of fibroblast-like cells that deposit excessive extracellular matrix (ECM), ultimately impairing organ function [ 11 ]. Chronic obstructive pulmonary disease further demonstrates how aberrant EMT contributes to pathological remodeling in the lungs [ 12 ]. Because EMT underlies so many diverse pathologies, there is increasing interest in modulating or reversing this process to limit disease progression and improve clinical outcomes. Matrix metalloproteinases (MMPs) play a critical role in mediating the transition between epithelial and mesenchymal phenotypes and these zinc-dependent proteases are key regulators of ECM homeostasis, as they degrade collagens, fibronectin, laminin, and other structural proteins [ 13 ]. In healthy tissues, MMPs work in concert with their endogenous inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), thereby maintaining a tightly balanced ECM turnover essential for physiological processes such as development and wound healing [ 14 ]. In the context of EMT, MMPs facilitate the breakdown of basement membranes, a critical event that allows cells to detach and migrate and they also activate latent growth factors, including transforming growth factor-beta (TGF-β), and cleave junctional proteins such as E-cadherin, further dismantling epithelial polarity [ 15 ]. Consequently, dysregulated MMPs activity promotes pathological forms of EMT observed in cancer invasion, metastasis, and fibrotic diseases [ 16 ]. In this review, we will outline the different types of EMT, review fundamental MMP biology, summarize the molecular mechanisms by which MMPs regulate EMT in both physiological and pathological contexts, and examine how MMP-mediated EMT drives conditions such as organ fibrosis, chronic inflammation, and cancer. We also discuss emerging therapeutic strategies aimed at rebalancing MMP activity or selectively inhibiting the most detrimental proteolytic events. These include CRISPR/Cas-based gene editing approaches that target pro-EMT genes, as well as engineered TIMPs designed to provide highly specific MMP inhibition. By exploring these interventions alongside ongoing controversies about MMP inhibitors and their clinical efficacy, we aim to highlight how selective control of MMP activity can mitigate EMT-driven disease while preserving essential functions in normal development and healing.