Bladder cancer (BC) is predominantly a disease of older adults–over 90% of cases in the United States occur in men above 45 years of age (Godlewski et al., 2024). Advanced age is one of the strongest risk factors for BC incidence and is associated with worse clinical outcomes; patients diagnosed after age 60 have significantly lower long-term survival than younger patients (Lin et al., 2023; Lenis et al., 2020). Several biological phenomena accompanying aging may contribute to this increased risk. Immunosenescence, the age-related decline in immune surveillance coupled with chronic low-grade inflammation (often termed “inflammaging”), is thought to create a pro-tumorigenic milieu in the elderly (Martin et al., 2022). Indeed, older individuals exhibit elevated systemic levels of inflammatory cytokines and an impaired anti-tumor immune response, which can facilitate cancer initiation and progression (Rentschler et al., 2022). At the same time, epigenetic drift, a process by which DNA methylation levels at thousands of CpG sites gradually shift from the pattern seen in young adults, occurs with aging (Issa, 2014). This progressive and stochastic deviation in methylation is driven by imperfect maintenance methylation and long-term environmental exposures. These epigenetic alterations can lead to the silencing of tumor-suppressor genes or activation of oncogenes, essentially “pre-setting” the stage for malignant transformation in aging tissues. Consistent with this, recent evidence indicates that biological age acceleration, as measured by DNA methylation “epigenetic clocks,” correlates with higher BC risk and poorer outcomes independent of chronological age (Deng et al., 2024).

Critically, many of the molecular hallmarks of aging–such as genomic instability, telomere attrition, and cellular senescence (López-Otín et al., 2013) – are closely interwoven with epigenetic regulatory changes. In bladder urothelium, age-related transcriptional shifts include increased expression of cell-cycle inhibitors (e.g., CDKN2A/p16-INK4A) and pro-inflammatory genes, reflecting an accumulation of senescent cells and inflammatory signals (Evangelou et al., 2023). However, bladder tumors frequently circumvent these aging defenses. For example, the CDKN2A gene (normally upregulated in aging cells to restrain proliferation) is often inactivated by promoter hypermethylation in BC, allowing tumor cells to bypass senescence (Jiao et al., 2018). To understand BC in the context of aging, it is therefore crucial to examine the epigenetic alterations that characterize bladder tumors–including changes in DNA methylation, histone modifications/chromatin remodeling, and non-coding RNA dysregulation alongside age-related processes like immunosenescence and epigenetic drift. Figure 1 provides a schematic overview of the key epigenetic mechanisms driving BC and illustrates how aging may modulate them, ultimately influencing tumor behavior and therapeutic responses in elderly patients. The figure also highlights emerging implications for epigenetic therapies, which may be especially beneficial for older individuals with BC.

Aberrant DNA methylation patterns are a well-established feature of bladder carcinogenesis and may be exacerbated by aging. In normal cells, aging is accompanied by cumulative DNA methylation changes–a phenomenon of epigenetic drift–including global hypomethylation and site-specific hypermethylation at certain gene promoters (Ciccarone et al., 2018). Bladder tumors display these alterations to an extreme degree. On one hand, cancer genomes undergo global hypomethylation with age and tumor progression, which can activate transposable elements and oncogenes, contributing to genomic instability. On the other hand, there is often focal hypermethylation of tumor-suppressor gene promoters in BC, leading to their transcriptional silencing. Researchers have identified hypermethylation in the promoters of over 50 genes in bladder tumors, providing an alternate route to gene inactivation beyond mutations. For instance, the CDKN2A gene (which encodes the p16INK4A protein) is frequently methylated in superficial (early-stage) bladder cancers, an event that likely occurs early in tumorigenesis (Gilyazova, et al., 2023b). This epigenetic silencing of CDKN2A is especially noteworthy in the context of aging: while normal elderly cells rely on CDKN2A upregulation to enforce senescence, bladder tumor cells can epigenetically shut down CDKN2A expression, thus evading an age-imposed growth arrest (Safwan-Zaiter et al., 2022).

Several other tumor suppressors and DNA repair genes are commonly silenced by DNA methylation in bladder cancer. Examples include TP53, RB1, E-cadherin (CDH1), among others, which have all been found to be hypermethylated in a subset of bladder tumors (Tran et al., 2021). In addition to these well-known cancer-related genes, other methylation targets such as SFRP1, LAMC2, and SOX9 have been associated with higher tumor grade, stage, and poorer survival in bladder cancer patients (Ye et al., 2021). Collectively, these findings suggest that age-related epigenetic lesions in the tumor (acquired over decades) can drive a more aggressive phenotype. Notably, one study stratified bladder tumors into molecular subgroups based on DNA methylation profiles and found that the subgroup with the highest burden of promoter hypermethylation had the worst prognosis (Luo and Vögeli, 2020). These findings support the concept that an accumulation of DNA methylation abnormalities–which can be viewed as an epigenetic “memory” of aging and carcinogenic exposures–contributes to tumor progression.

Aging not only induces static promoter hyper- and hypomethylation in BC but also reshapes systemic immunity through cumulative DNA-methylation drift captured by “epigenetic clocks.” When methylation-derived biological age is regressed on chronological age, the residual—epigenetic-age acceleration (EAA)—quantifies the speed of epigenetic aging. In 601 non-muscle-invasive BC patients, each 1-year increment in peripheral-blood PhenoAge-EAA raised the 10-year overall-mortality risk by 6% (multivariable-adjusted HR = 1.06, 95% CI 1.03–1.08) and coincided with a neutrophil-rich, memory-T-cell–poor immune profile (Chen et al., 2023b). CpGs that receive high weights in several epigenetic clocks—ranging from five-site forensic models to the PhenoAge and Horvath algorithms—tend to cluster near ELOVL2, FHL2, KLF14, TRIM59, RCAN1, CD46—genes implicated in lipid metabolism, T-cell signaling, and complement control—suggesting a mechanistic bridge between systemic epigenetic aging and impaired anti-tumor immunity (McCartney et al., 2021; Jung et al., 2019). Comparable EAA–prognosis associations have been reported in colorectal, hepatocellular, and breast carcinomas (Horvath, 2013), indicating that systemic epigenetic aging is a pan-cancer modifier whose quantitative impact depends on tumor context. Mechanistically, age-related hypermethylation of cytotoxic T-lymphocyte genes or antigen presentation machinery can blunt immune surveillance (Chen et al., 2023b). Consistent with this, loss of MHC class I expression is frequently observed in recurrent tumors and BCG-unresponsive disease (Wieczorek and Garstka, 2021), and while genetic loss can be one cause, there is evidence that epigenetic mechanisms (like promoter methylation of antigen-processing genes) contribute to immune escape. Indeed, demethylating agents can upregulate MHC and antigen presentation in some cancers, making tumor cells more visible to the immune system (Jongsma et al., 2021). Although this strategy is still under investigation in BC, it underscores how age-associated epigenetic repression of immune-related genes might be reversed for therapeutic benefit.

From a diagnostic and therapeutic standpoint, DNA methylation changes offer attractive biomarkers in the aging population with BC. Methylated DNA can be detected in urine sediments as a noninvasive test, which is especially useful for older patients who may not tolerate frequent invasive cystoscopies. Several urine DNA methylation assays (targeting panels of genes like GHSR, SST, PRDM14, and others) have shown high sensitivity for bladder cancer detection (Hentschel et al., 2022). Moreover, epigenetic biomarkers could help predict which older patients are at risk of aggressive disease. For example, an elevated “methylation age” or hypermethylation of certain promoters may indicate tumors with more aggressive behavior, independent of the patient’s chronological age. Clinically, epigenetic therapy using DNMTi is an area of interest. Hypomethylating agents such as decitabine and azacitidine, which are already used in myelodysplastic syndromes (another disease of the elderly) (Zhou et al., 2024), could in theory “rejuvenate” the epigenome of bladder cancer cells–reactivating silenced tumor suppressors and immune genes. While these agents are not yet standard for BC, preclinical studies suggest they can slow tumor growth and enhance immune recognition of bladder tumor cells (Hu et al., 2021; Nunes et al., 2020). Thus, reversing age-related DNA methylation changes holds promise as a therapeutic avenue, particularly for older BC patients who may derive dual benefit from tumor suppression and improved immunogenicity (Pereira et al., 2024).

Bladder cancer incidence is four times higher in men, yet women who develop the disease often present with more advanced stage and poorer stage-adjusted survival (Doshi et al., 2023). Recent population studies using DNA-methylation “clocks” reveal that peripheral-blood EAA is on average ≈ 1.5 years higher in men than in women, even after correcting for smoking and body-mass index (Kankaanpää et al., 2021). In cancer cohorts, the adverse prognostic impact of high EAA is likewise stronger in males, suggesting that sex modifies the biological consequences of methylation drift (Yu et al., 2021).

A principal driver of this asymmetry is androgen-receptor (AR) signaling. AR recruits DNMT1 and the histone-methyltransferase EZH2 to target promoters, accelerating hyper-methylation and H3K27me3 deposition on tumor-suppressor genes (Zimmerman et al., 2023); pharmacological or genetic AR blockade in the N-butyl-N-(4-hydroxybutyl) -nitrosamine (BBN) mouse model attenuates both methylation drift and tumor incidence (Doshi et al., 2023). Conversely, predominantly via Erβ, estrogen signaling upregulates DNA-repair genes such as BRCA1 and MGMT and slows clock-CpG drift (Zach et al., 2022; Paranjpe et al., 2016); post-menopausal estrogen decline is accompanied by an abrupt 6–8-year jump in the PhenoAge-EAA in large female cohorts (Levine et al., 2016). These hormonal effects intersect with chromatin architecture: AR activation promotes EZH2 overexpression, whereas ERβ can suppress EZH2 transcription, partially explaining the higher prevalence of EZH2-high, immune-cold tumors in older men.

Sex chromosomes add a further layer. KDM6A, an X-chromosome escapee histone-demethylase, is expressed from both alleles in females but from a single allele in males; functional loss abolishes the female survival advantage in murine urothelial carcinogenesis and correlates with reduced CD8⁺ infiltration in human BC(Kaneko and Xue, 2018; Chen et al., 2021a). Because KDM6A counteracts EZH2, its hemizygous state in men may sensitize the male epigenome to AR-EZH2-driven repression, reinforcing the cascade from systemic EAA to local immune evasion (Ramakrishnan et al., 2019; Villanueva, 2017).

Clinical ramifications are two-fold. First, sex-stratified EAA cut-offs could sharpen prognostic models; a 1-year PhenoAge-EAA carries a greater hazard in men than in women. Second, therapy choices might be sex-specific: AR antagonists or EZH2i combined with checkpoint blockade warrant prioritization in EAA-high male patients, whereas estrogen-supplemented PARP- or DNMT-inhibitor regimens could be explored in post-menopausal females with accelerated EAA (Doshi et al., 2023). Taken together, these sexually dimorphic pathways link systemic epigenetic ageing to chromatin-level repression and immune escape—mechanisms that segue directly into the next section on histone modifications and chromatin remodeling.

Beyond DNA methylation, histone modifications and chromatin remodeling are key epigenetic regulators that are frequently perturbed in BC–often through mutations in histone-modifying enzymes or chromatin regulators. Notably, some of the most commonly mutated genes in bladder tumors encode epigenetic modifiers, indicating how central these epigenetic regulatory processes are to disease pathogenesis (Knowles and Hurst, 2015). For example, the histone methyltransferase gene KMT2D (also known as MLL2) and the histone demethylase gene KDM6A (UTX) are mutated in approximately 20%–30% of bladder cancers, as reported by The Cancer Genome Atlas (TCGA) analyses (Schulz et al., 2019). These loss-of-function mutations have significant epigenetic consequences: KDM6A normally removes repressive H3K27 methylation marks, so its loss can lead to an increase in the repressive H3K27me3 mark on tumor suppressor gene promoters (Tran et al., 2020). Meanwhile, KMT2D is an ‘epigenetic writer’ of the activating H3K4me mark; its mutation might reduce expression of genes needed for maintaining differentiated urothelial cell identity (Wang et al., 2025). The net effect of these mutations is an epigenetic shift toward a more primitive, proliferative, and invasive transcriptional program in the cancer cells.

Importantly, the impact of such mutations may be modulated by patient age. Older patients, by virtue of longer exposure to carcinogens and a lifetime of cell divisions, are more likely to accumulate multiple hits in these chromatin regulators. There is also evidence that the consequences of losing certain epigenetic regulators might be more pronounced in the aging context. For instance, ARID1A–a component of the SWI/SNF chromatin remodeling complex–is another frequently mutated gene (∼20% of BC) whose loss can destabilize chromatin structure. In an older cell, which already may have heterochromatin decrease and more transcriptional noise, loss of ARID1A could further promote genomic chaos and dedifferentiation (Zhang et al., 2020; Braga et al., 2020). Moreover, these ARID1A alterations frequently coincide with high tumor mutational burden (TMB) subtypes of bladder cancer (Conde and Frew, 2022). This suggests an interplay in which aging-associated exposures induce these mutations, thereby confer selective advantages in the context of an aged (and perhaps inflammation-rich) tissue microenvironment.

Apart from mutations, dysregulation of histone-modifying enzymes also occurs in bladder cancer and can relate to aging processes. One prominent example is EZH2, the catalytic subunit of Polycomb Repressive Complex 2 (PRC2) that trimethylates histone H3 on lysine 27 (H3K27me3) to silence genes. EZH2 levels increase in many cancers, including aggressive bladder carcinomas (Thompson et al., 2023). Intriguingly, age-related changes in tissue often involve shifts in PRC2 activity–for instance, stem cells in older organisms exhibit altered PRC2 targets - which may help explain why EZH2 is frequently overexpressed in high-grade, muscle-invasive bladder tumors and is correlated with shorter time to recurrence (Piunti et al., 2022). This overexpression might be partly driven by the loss of antagonistic regulators like KDM6A (since KDM6A normally opposes EZH2’s mark) (Taylor-Papadimitriou and Burchell, 2022). Functionally, EZH2 overactivity in tumors leads to silencing of differentiation genes (e.g., E-cadherin) and immune-related genes, contributing to a more malignant and immune-evasive phenotype (Martínez-Fernández et al., 2015b). From the aging perspective, an older patient’s immune system is already less responsive; if a tumor upregulates EZH2 and thereby suppresses antigen presentation or chemokine production, the immunosurveillance might be especially ineffective. Notably, recent studies demonstrated that EZH2-mediated repression plays a direct role in immune escape in bladder cancer. In a carcinogen-induced bladder cancer model, inhibition of EZH2 resulted in significantly reduced tumor progression only when the adaptive immune system was intact–in mice lacking T-cells, EZH2 inhibitors had little effect. EZH2 inhibition was found to activate the immune response by upregulating MHC class II and other immune genes in the tumor microenvironment, effectively reversing an epigenetically enforced immunosuppressive state (Piunti et al., 2022). These findings are highly relevant to older patients: they imply that epigenetic therapies targeting repressive histone marks (like H3K27me3 via EZH2i) could rejuvenate anti-tumor immunity, counteracting immunosenescence (Allegra et al., 2023).

Another layer of evidence linking histone modifiers to immune regulation is provided by KDM6A (UTX) mutations. Beyond its general tumor-suppressive role, KDM6A loss in BC has been shown to attenuate the anti-tumor immune response. Tumors with KDM6A mutations tend to have fewer tumor-infiltrating lymphocytes (especially CD8⁺ T cells) and a microenvironment skewed toward immune tolerance (Chen et al., 2021a). Transcriptomic analyses indicate that KDM6A-mutant bladder cancers have downregulation of multiple interferon and chemokine signaling pathways required for effective tumor immunity (Kobatake et al., 2020). Clinically, low KDM6A expression in tumors is associated with worse outcomes in BC patients (Alessandrino et al., 2020). One can surmise that in an elderly patient with an already waning immune system, the loss of KDM6A could be a double blow–epigenetically silencing immune-response genes in the tumor and thus further reducing immune cell recruitment to the tumor site. This synergy between aging and epigenetic mutation may partly explain why older BC patients often do not mount strong anti-tumor immune reactions, and why they might respond differently to therapies. It also opens the door to potential combination therapies: for example, using EZH2i or HDACi to epigenetically reprogram “cold” tumors into “hot” (T-cell inflamed) tumors, thereby improving the efficacy of immunotherapies like PD-1 checkpoint inhibitors (Kalbasi and Ribas, 2020). Currently, early-phase clinical trials are exploring this concept–a combination of the EZH2 inhibitor tazemetostat with the PD-1 immunotherapy pembrolizumab was found to be tolerable in advanced urothelial carcinoma, with hints of enhanced immune activation​(Shin et al., 2022). Such epigenetic-immunotherapy combos may be especially relevant for older patients, who often have immunosenescent T cells that need extra stimulation to attack cancer.

In summary, bladder cancer’s alterations in histone modification pathways–whether via mutation (KDM6A, ARID1A, KMT2D) or overexpression (EZH2, HDACs) – are a central component of its biology and interact with aging. The aged epigenome already undergoes shifts like loss of heterochromatin and redistribution of histone marks; bladder tumors build on this by manipulating histone modifiers to promote uncontrolled growth and immune evasion. Recognizing these changes has direct clinical significance. Epidrugs (epigenetic drugs) that target histone-modifying enzymes (e.g., EZH2i, HDACi) could potentially reverse some age-related epigenetic advantages that tumors possess. In preclinical models, targeting these enzymes not only slows tumor proliferation but also unmasks the tumor to the immune system (Yu et al., 2024). Therefore, therapies aimed at the “histone code” may turn out to be particularly impactful in older bladder cancer patients, converting their immunologically silent tumors into ones that can be cleared by the patient’s immune system or by immunotherapy.

Non-coding RNAs, including miRNAs, lncRNAs, and other types (e.g., circular RNAs), play critical roles in the epigenetic regulation of gene expression (Nemeth et al., 2024). Dysregulation of these RNAs is a hallmark of bladder cancer, and contributes to its development and progression (Zou et al., 2024). Moreover, the expression profiles of certain non-coding RNAs change with age (sometimes called “gero-miRNAs”), which can influence cellular senescence, chronic inflammation, and tumorigenesis (Wagner et al., 2024). In BC, many tumor-suppressive miRNAs are downregulated, while oncogenic miRNAs are upregulated. This imbalance often creates a gene expression pattern that promotes malignancy. Aging can exacerbate these patterns by altering miRNA biogenesis and turnover mechanisms (Sanz-Ros et al., 2023).

Aging profoundly shapes the epigenetic landscape of bladder cancer. As outlined, older patients with BC often exhibit tumors with widespread DNA methylation abnormalities, mutations in chromatin-modifying genes, and altered non-coding RNA profiles. These changes are not merely passive bystanders but actively drive tumor initiation, progression, and immune evasion. An emerging theme is that bladder tumors effectively co-opt age-related epigenetic processes to their advantage–for instance, silencing senescence regulators (such as p16-INK4A and miR-34a), upregulating immune-suppressive factors (like EZH2 and HOTAIR), and exploiting the chronic inflammatory microenvironment of aged tissues (Balaraman et al., 2025; Nutt et al., 2020). Understanding these interactions between aging and epigenetics opens up new avenues to improve management of BC in older adults. Key future directions include the following.