WWOX (WW domain-containing oxidoreductase) is a critical tumour suppressor gene implicated in various cancers, located in the chromosomal region 16q23.3-24.1. The WWOX gene encodes a protein that contains two WW domains and a short-chain dehydrogenase/reductase (SDR) domain, which facilitates interactions with multiple protein partners. These structural components enable it to interact with multiple protein partners (Taouis et al. 2021). The protein product of WWOX features two N-terminal WW domains and a C-terminal SDR domain that enables it to engage with various partner proteins and modulate their activities—essential for maintaining cellular homeostasis and inhibiting tumour development (Khawaled et al. 2020).

One of the key functions of WWOX is its role in DNA damage repair. The protein interacts with molecules involved in repairing DNA lesions, which is essential for maintaining genomic stability. By preserving the integrity of the genome, WWOX plays a significant role in cancer prevention (Del Mare et al. 2009; McBride et al. 2019). This highlights its multifaceted role in cellular processes (Khawaled et al. 2020). Furthermore, WWOX regulates key signalling pathways such as TGF-β and Wnt, which are vital for cell adhesion, motility, and invasion. These interactions underscore its role in preventing metastasis and tumour progression (Khawaled et al. 2020). This extensive network of interactions allows WWOX to influence essential cellular processes, including apoptosis, cell growth, and metabolism (Taouis et al. 2021). By modulating these signalling cascades, WWOX influences critical cellular processes including apoptosis, cell growth, and metabolism.

In addition to its role in DNA repair, WWOX is intricately linked to metabolic regulation. It has been shown to influence glucose metabolism by interacting with hypoxia-inducible factor 1α (HIF1α), thereby inhibiting aerobic glycolysis and preventing the Warburg effect—a phenomenon where cancer cells increase glucose uptake and lactate production even in the presence of oxygen. Furthermore, WWOX affects lipid metabolism by regulating high-density lipoprotein (HDL) levels and cholesterol homeostasis, which are crucial for overall metabolic health (Richards et al. 2015).

The importance of WWOX extends beyond cancer biology to other physiological processes. Dysregulation of WW domain-mediated signalling can disrupt normal physiological functions, leading to various diseases, including neurological disorders (Chang et al. 2019). For example, its deficiency in newborns can result in neurological symptoms, prompting investigations into the mechanisms of WWOX downregulation and its implications for neurodegeneration (Chang et al. 2019).

The discovery of WWOX originated from studies on loss of heterozygosity (LOH), where a single allele deletion was observed in about 70% of very early-stage cancers such as ductal carcinoma in situ (DCIS) (Xiong et al. 2010). Interestingly, despite this deletion, no other WWOX mutations in the second allele were found, which is atypical for tumour suppressor genes (Xie et al. 2016). Moreover, the WW domains of WWOX are known to facilitate protein-protein interactions, playing a crucial role in transmitting various signalling cascades by recognizing proline-rich peptide motifs and phosphorylated serine/threonine-proline sites. Recent analyses of the human proteome identified at least 52 WW domain-containing proteins, with over 10,000 such proteins across all species, each playing critical roles in essential cellular functions (Huang and Chang 2018). Genetic variations in WWOX, including polymorphisms, have been linked to an increased risk of chronic obstructive pulmonary disease (COPD) (Xie et al. 2016), and metabolic syndrome disorders (Lee et al. 2008; Abu-Remaileh et al. 2019).

Environmental factors can also influence WWOX expression. For instance, in vitro studies indicate that exposure to cigarette smoke extract silences WWOX in bladder cancer cells by adding methyl groups to its DNA (Yang et al. 2012). In mouse models, knockdown of WWOX using siRNA resulted in alveolar protein leakage, neutrophil influx, and increased inflammatory cytokine production, exacerbating lung injury caused by lipopolysaccharides (LPS) (Singla et al. 2017). Similarly, knockdown experiments in human alveolar epithelial cells demonstrated enhanced neutrophil chemotaxis upon reduced WWOX expression. These findings highlight the protective role of WWOX against environmental stressors (Tanimura and Nyunoya 2021).

In summary, the diverse roles of WWOX in regulating both glucose and lipid metabolism highlight its potential as a therapeutic target in metabolic disorders and cancer (Fig. 1). To fully appreciate the complexities of this issue, it is crucial to explore the intricate mechanisms by which WWOX operates within various signalling pathways. This review aims to focus on the central role of WWOX in cancer, while also providing a concise overview of its structural features and functional mechanisms that contribute to tumour suppression. We would also like to note that throughout the text cancers are abbreviated according to The Cancer Genome Atlas (TCGA) nomenclature where applicable.

A graphical illustration of some of the diverse mechanisms through which the WW domain-containing oxidoreductase (WWOX) functions as a tumour suppressor in various cancer types. This figure was created using images from Servier Medical Art (https://smart.servier.com), which are licensed under a Creative Commons Attribution 3.0 Unported License

The history of WWOX research began with the mapping of this gene in the DNA region frequently affected in breast cancer (BRCA) (Bednarek et al. 2000). Currently, it is well-established that a significant reduction or complete absence of WWOX gene expression is observed predominantly in BRCA cases and the advanced role of WWOX alterations in BRCA is the best known (Pospiech et al. 2018). Nevertheless, BRCA is a genetically and clinically heterogeneous disease encompassing multiple subtypes, which differ in the WWOX expression. The widely accepted classification approach for BRCA is based on the results of immunohistochemical analysis, focusing on the expression of three key hormone receptors: oestrogen (ER), progesterone (PR), and human epidermal growth factor (HER2). This immunohistochemical approach helps identify four main subtypes: Luminal A, Luminal B, HER2-positive and Triple-negative breast cancer (TNBC) (Orrantia-Borunda et al. 2022). Although WWOX is implicated in all BRCA subtypes, its expression and functional implications vary significantly across them (Baryła et al. 2015; Pospiech et al. 2018). Still, a significant reduction or complete absence of WWOX expression, in many subtypes of BRCA tissues is observed (Iliopoulos et al. 2007); which correlates with several aggressive biological properties in BRCA, including epithelial-to-mesenchymal transition (EMT), tumour metastasis, and chemoresistance (Ludes-Meyers et al. 2003; Li et al. 2018).

While the loss of WWOX expression in BRCA is well documented, its regulatory effects are less understood. Nevertheless, new research deepens our understanding of the molecular basis of breast cancer, pointing to an increasingly clear role for the WWOX gene. Recent studies indicate that WWOX’s role in breast carcinogenesis is closely linked to ER presence (Nunez et al. 2005; Pospiech et al. 2022). Specifically, WWOX influences gene expression regulated by oestrogen receptors (ERα and ERβ), affecting proliferation and apoptosis differently based on ER status. For example, downregulation of WWOX in ER-positive MCF7 cells decreases adhesion, whereas it increases adhesion in ER-negative BT-20 cells. Following oestrogen treatment, WWOX transduction significantly alters adhesion properties in oestrogen-responsive cell lines. Additionally, differences in the expression of TGFα-EGFR pathway genes were noted in response to changes in WWOX expression in breast cancer cell lines. TGFα-EGFR signalling is primarily regulated by oestradiol, but reduced WWOX expression may enhance the carcinogenic effects of this pathway, contributing to increased tumour aggressiveness (Pospiech et al. 2022).

Above all, however, research emphasises WWOX’s role as a vital tumour suppressor that interacts with p53, which is commonly mutated in BRCA (Marvalim et al. 2023). The loss of WWOX disrupts TP53 function, facilitating BRCA development. In a mouse model with Wwox inactivation, 76% of subjects developed invasive ductal carcinomas, some with lung metastases, resembling human TNBC and basal-like breast cancers, which are characterized by the absence of WWOX and hormone receptors (Abdeen et al. 2018). Tumours from Wwox-deficient mice exhibited gene expression patterns and genomic instability similar to those found in TP53 knockout mice. Notably, while TP53 knockout tumours showed low levels of WWOX protein, they had increased WWOX RNA levels, suggesting a compensatory mechanism. What is more, all tumours exhibiting LOH for WWOX demonstrated reduced TP53 expression due to deletions in exons 2–10, indicating that WWOX inactivation may lead to the loss of the TP53 region. Additionally, patient data revealed co-occurrence of homozygous deletions in both WWOX and TP53 (Abdeen et al. 2018). These data underscore the importance of WWOX loss as an equally important and related factor to TP53, the most frequently mutated gene in breast cancer.

Additionally, WWOX regulates various signalling pathways related to cancer; such as suppressing STAT3 activity, inhibiting BRCA cell proliferation and migration (Chang et al. 2018). STAT3 is known to promote breast cancer malignancy (Ma et al. 2020), so mainly TNBC is characterized by low WWOX expression and activated STAT3. Thus, restoring WWOX inhibits metastasis, while its depletion promotes it (Khawaled et al. 2019). WWOX interacts with STAT3 via its WW1 domain, affecting STAT3’s DNA-binding ability and inhibiting its phosphorylation—thereby reducing transcriptional activity. This interaction also decreases JAK2 phosphorylation and its binding to STAT3; without WWOX, JAK2/STAT3 activation increases, promoting metastasis in TNBC. Therefore, targeting the JAK2/STAT3 signalling pathway is considered a promising therapeutic strategy for TNBC (Chang et al. 2018). It is also important to note that, it is not a single pathway, which is disturbed by WWOX absence and related with breast cancer metastasis. Some of the newest reports indicate that knocking down WWOX in MCF7 BRCA cells leads to the upregulation of HIF1α glycolytic genes under normoxic conditions—a phenomenon known as the Warburg effect. Importantly, WWOX-deficient cells lacking HIF1α do not form tumours in mice; additionally, WWOX inversely regulates GLUT1 expression- a direct target of HIF1α - in human BRCA patients (Abu-Remaileh and Aqeilan 2014; Pospiech et al. 2018). In vitro studies demonstrate that restoring WWOX suppresses motility and invasive ability in BRCA cells. In mouse models, cells expressing WWOX formed 95% fewer metastatic lesions compared to controls, indicating that WWOX suppresses metastasis from the mammary gland by inhibiting local invasion and potentially reducing proliferation at secondary sites like the lungs (Khawaled et al. 2019; Do et al. 2020).

On top of that, the anti-metastatic effects of WWOX stem from its regulation of different processes involved in metastatic dissemination, including through microRNAs (miRNAs) modulation (Khawaled et al. 2019; Do et al. 2020). WWOX modulates the expression of at least several dozen miRNAs in breast cancer cell lines. The most significant seems to be regulation of miR-146a, which is associated with breast cancer risk, and has suppressive effects on EMT as well as on the metastatic potential. Notably, WWOX promotes the accumulation of miR-146a by suppressing the MYC oncoprotein—highly expressed in TNBC (Fallah et al. 2017; Khawaled et al. 2019). In TNBC cases, WWOX binds to the MYC promoter to reduce its expression, which in turn increases the levels of miR-146a. Then, miR-146a blocks fibronectin, helping cells maintain an epithelial state and preventing EMT and metastasis. The WW1 domain of WWOX is crucial for its interaction with MYC promoter and suppression of TNBC metastasis by inhibiting invasion [31]. Restoration of WWOX in WWOX-deficient TNBC cell lines suppresses proliferation, migration, and invasion, whereas its ablation in WWOX-sufficient TNBC cells promotes tumorigenic traits and metastatic potential. WWOX restoration in these cell lines leads also to the downregulation of the miRNAs which are known onco-miRNAs (Khawaled et al. 2019). Additionally, the expression of miR-182, known onco-miRNA, is significantly upregulated in the WWOX-deficient MDA-MB-231 cells. Moreover, high levels of miR-182 in WWOX-deficient MDA-MB-231 cells make them resistant to cisplatin by disrupting key pathways involved in DNA repair, apoptosis, and AKT signalling (Batar et al. 2024). Thus, miRNA regulation by WWOX in TNBC is associated with both metastasis and drug resistance. Entirely additionally, downregulation of WWOX in BRCA stem cells also induces EMT and chemoresistance (Li et al. 2018).

Furthermore, WWOX is essential for maintaining genome integrity and regulating DNA repair mechanisms to prevent genetic alterations that can lead to cancer (Schrock et al. 2017; Hussain et al. 2019; Taouis et al. 2021, 2023). Recent studies highlight its interaction with BRCA1 which is crucial for homologous recombination (HR) repair of double-strand breaks (DSBs). Mutations in BRCA1 are often linked to TNBC (Chen et al. 2018a). In BRCA cells lacking WWOX, reduced interaction between WWOX and BRCA1 may enhance HR efficiency—allowing cancer cells to survive DNA-damaging treatments (Schrock et al. 2017). Whereas loss of WWOX expression correlates with resistance to radiation and cisplatin in MDA-MB-231 cells, thus suggesting that levels of WWOX could predict treatment responses. On top of that, WWOX not only influences HR but also enhances non-homologous end joining (NHEJ) repair mechanisms—acting as a genome caretaker (Schrock et al. 2017). While most DNA repair proteins are localized within the nucleus, WWOX is primarily cytoplasmic; however, it possesses a nuclear localization signal located between its N-terminal WW domains (47PKTGKRKRVAG57). Importantly, phosphorylation at Tyr-33 is essential for activating WWOX and facilitating its nuclear translocation—allowing it to bind other proteins such as p53 and translocate into the nucleus to exert its tumour-suppressive functions (Aldaz and Hussain 2020; Park et al. 2022). Additionally, WWOX is recruited to DSBs through direct interaction with BRCA1 (Park et al. 2022), which regulates the choice between DSB repair pathways by favouring NHEJ over HR repair mechanisms. Additionally, WWOX interacts with MERIT40—a positive regulator of DNA damage repair, thereby inhibiting excessive HR activity and maintaining genome stability (Silver and Livingston 2012; Her et al. 2016; Taouis et al. 2023). Overexpression of MERIT40 in BC induces excessive HR activity that is counteracted by WWOX through its interaction with the N-terminal part of MERIT40’s SDR domain. Altered expression levels of both WWOX and MERIT40 correlate with increased genomic instability and poor clinical outcomes in breast cancer patients (Taouis et al. 2023).

Although most studies have focused on genes and pathways regulated by WWOX or disrupted by WWOX reduction in cancer, attention has been drawn to the existence of genes responsible for WWOX regulation. VOPP1 has emerged as a significant regulator of WWOX, interacting through the WW1 domain of WWOX and the PPPY motif in VOPP1. Overexpression of VOPP1, frequently observed in breast tumours, diminishes the tumour-suppressive functions of WWOX and is associated with shorter metastasis-free survival. WWOX, when co-expressed with VOPP1, abandons its typical Golgi distribution. Instead, it is punctate localised in lysosomal structures, with VOPP1 sequestering WWOX within lysosomal vesicles. Additionally, VOPP1 inhibited WWOX-dependent apoptosis by preventing the WWOX-p73α interaction. This suggests that VOPP1 may play a role in breast cancer by interfering with WWOX’s function as a tumour suppressor (Bonin et al. 2018).

The mentioned findings suggest that WWOX not only influences tumour progression but also impacts patient prognosis. WWOX interacts with critical proteins such as p53 and BRCA1, playing essential roles in apoptosis and DNA repair mechanisms. The loss of WWOX disrupts these interactions, contributing to cancer development and treatment resistance. Additionally, WWOX regulates signalling pathways like JAK2/STAT3, which are particularly relevant in TNBC, where WWOX expression is low. Its ability to modulate microRNA expression further highlights its multifaceted role in maintaining cellular integrity and preventing metastasis.

The involvement of the WWOX gene in hormone-dependent cancers was additionally studied in ovarian tumours. Ovarian tumours encompass a diverse range of malignant conditions, each characterized by distinct pathogenesis and molecular profiles. The 2020 World Health Organization (WHO) classification categorizes ovarian cancer into three primary types: epithelial ovarian cancer (EOC), which constitutes approximately 90% of cases, germ cell tumours, and sex cord-stromal tumours (Tavares et al. 2024). Expression levels of WWOX vary among molecular subtypes of ovarian cancer, with lower levels linked to poorer outcomes and aggressive tumour behaviour (Janczar et al. 2017). Additionally, WWOX expression correlates with key clinical parameters, including histological stage, International Federation of Gynaecology and Obstetrics (FIGO) stage, pathological grade, lymph node metastasis, and recurrence rates (Cai et al. 2016; Hu et al. 2019). EOC patients with WWOX protein expression had significantly longer survival times compared to those without WWOX expression (Yu et al. 2019).

EMT is key process during ovarian carcinoma oncogenesis and development. In ovarian cancer tissue samples, WWOX expression significantly differs from that of mesenchymal markers such as N-cadherin, vimentin, and Snail1, which are highly expressed in cancer tissues compared to their lower levels in normal tissues (Hu et al. 2019). Conversely, WWOX, along with the EMT inhibitor Elf5 and the epithelial marker E-cadherin, shows reduced expression in ovarian cancer tissues. Notably, WWOX interacts with Elf5, and patients with positive expression of both proteins have a significantly higher five-year survival rate—42.5% for those positive compared to only 15.5% for those negative. This suggests that WWOX and Elf5 may serve as protective factors and prognostic markers in ovarian cancer. The loss of WWOX and Elf5 may facilitate Snail1-mediated EMT, contributing to tumour progression. Restoring WWOX expression in ovarian carcinoma cell lines enhanced E-cadherin levels and Elf5 activity while decreased N-cadherin and Snail1 activity. Consequently, WWOX overexpression reduces the migratory and invasive capabilities of ovarian cancer cells by regulating key EMT factors. In contrast, silencing WWOX lead to the opposite effects (Xu et al. 2020).

Furthermore, WWOX likely regulates tumour angiogenesis through the VEGF pathway via Wnt/β-catenin signalling; increased angiogenesis correlates with poorer survival outcomes in ovarian cancer patients. In epithelial ovarian cancer, WWOX negatively correlates with LGR5 and vasohibin-1—both implicated in tumour development and angiogenesis regulation (Du et al. 2017; Liu et al. 2018; Yu et al. 2019; Xu et al. 2019b). Introducing WWOX expression into ovarian cancer stem cells significantly reduces their proliferation and alters the cell cycle dynamics, causing an arrest in the G0/G1 phase and a reduction in the S phase population (Yan et al. 2015a, b). Additionally, WWOX downregulates cyclin E-CDK2 and cyclin D1-CDK4 expression, impacting cell cycle progression while inhibiting self-renewal abilities of these stem cells (Yan et al. 2015b). Moreover, WWOX promotes apoptosis in ovarian cancer stem cells by activating the Wnt/JNK/caspase-3 signalling pathway, enhancing apoptosis nearly fourfold (Yan et al. 2015a). Interestingly, while it promotes apoptosis, WWOX inhibits autophagy in EOC cells by interacting with mTOR, a negative regulator of autophagy; loss or inactivation of WWOX may lead to increased autophagy in chemotherapy-resistant cells (Yan et al. 2015a; Zhao et al. 2020).

In terms of treatment response, WWOX also confers sensitivity to chemotherapeutic drugs like cisplatin and paclitaxel by inducing apoptosis in ovarian cancer cells (Yan et al. 2015b; Janczar et al.