The review, authored by researchers at National Chung Cheng University and Ditmanson Medical Foundation Chiayi Christian Hospital in Taiwan, synthesizes current evidence on how chemical tags on DNA and histone proteins shape the battle between tumor cells and the innate immune system, and how drugs that rewrite those tags could make immunotherapy work in patients who currently resist it.
Natural killer cells, or NK cells, are a specialized branch of the innate immune system. Unlike T cells, which require prior exposure to a specific antigen before they can attack, NK cells can recognize and destroy transformed cells without any priming. They are characterized molecularly as CD56-positive, CD16-positive and CD3-negative, and they kill tumor cells in two main ways: direct lysis and the secretion of interferon-gamma, an inflammatory signaling molecule that rallies further immune activity. Their activity is governed by a delicate balance between activating and inhibitory receptors on their surface, and among the activating receptors, one stands out for tumor surveillance: NKG2D.
NKG2D recognizes stress-induced ligands displayed on the surface of distressed or malignant cells, including the UL16-binding proteins and the MHC class I chain-related proteins MICA and MICB. When NKG2D engages these ligands, it triggers a signaling cascade through the adaptor protein DAP10, recruiting downstream effectors such as PI3K and the Grb2-Vav1 complex. This leads to cytoskeletal reorganization and the polarization of cytotoxic granules toward the immunological synapse, the narrow junction where the NK cell meets its target. The granules then release perforin and granzyme B, molecules that punch holes in the tumor cell membrane and shred it from within. It is an elegant, fast-acting killing mechanism, and cancer cells know exactly how to sabotage it.
The central problem, according to the review, is that urothelial carcinoma cells frequently evade this surveillance by downregulating the very ligands NKG2D needs to see. This downregulation is often mediated by the hostile tumor microenvironment and by complex epigenetic changes. Aberrant DNA methylation and histone modifications can suppress the expression of ULBPs and MICA/B on the tumor surface, effectively cloaking the cancer from NK recognition. In parallel, epigenetic dysregulation within the NK cells themselves can impair their cytotoxic capacity by silencing key effector molecules such as granzyme B and perforin. At the molecular level, the repression of MICA/B and ULBP1-6 involves multiple epigenetic regulators, including the DNA methyltransferases DNMT1, DNMT3A and DNMT3B, class I and II histone deacetylases, and the polycomb protein EZH2, which deposits the repressive histone mark H3K27me3.
Urothelial carcinoma is particularly susceptible to this kind of epigenetic hijacking. Large-scale sequencing efforts such as The Cancer Genome Atlas have revealed that muscle-invasive bladder cancer is profoundly shaped by epigenetic dysregulation, with recurrent mutations in chromatin remodeling and histone-modifying genes such as ARID1A, KDM6A, CREBBP, EP300 and SMARCB1. These mutations coexist with alterations in the PI3K/AKT/mTOR and DNA damage repair pathways, and together they disrupt chromatin accessibility and transcriptional regulation, affecting tumor suppression, DNA repair and immune responses. Loss of ARID1A, for example, alters immune-related transcription and DNA repair, while KDM6A mutations rank among the most frequent epigenetic alterations in bladder cancer. Beyond mutations, promoter DNA hypermethylation at genes including ZNF671, IRF6, RARB2 and GSTP1, together with repressive histone marks such as H3K27me3 and H3K9me3, can silence tumor suppressor genes and reshape chromatin architecture.
Some of these molecular alterations carry direct clinical weight. ZNF671 promoter methylation has been associated with an increased risk of recurrence, and mutations in ARID1A have been proposed as potential biomarkers of response to immune checkpoint inhibitors. DNA methylation at promoter CpG islands also serves as a promising biomarker for cancer detection in urine samples, specifically for genes such as ZNF671, IRF6 and GSTP1. MicroRNAs add yet another layer of regulation, post-transcriptionally modulating gene expression by binding to the 3-prime untranslated regions of target messenger RNAs and triggering their degradation or blocking their translation. The review’s authors argue that understanding this multilayered epigenetic machinery is essential for moving beyond one-size-fits-all surgery toward precision immunotherapy.
The therapeutic implication is that epigenetic drugs could reverse the escape mechanisms tumors rely on. DNA methyltransferase inhibitors such as decitabine and azacitidine can demethylate the promoters of NK-activating ligands, restoring their expression on tumor cells. Histone deacetylase inhibitors such as entinostat and vorinostat have been shown to upregulate NKG2D ligands and enhance NK-cell cytotoxicity. By reprogramming the tumor microenvironment in this way, these agents may sensitize urothelial tumors to immune checkpoint inhibitors, creating synergistic effects that position epigenetic modulation as a promising frontier for personalized immunotherapy. The authors’ own recent publication demonstrated that entinostat enhances NK cell-mediated cytotoxicity by promoting the expression of epigenetically suppressed ULBPs and other NKG2D ligands.
These ideas have already moved beyond preclinical work. Early-phase clinical trials have investigated decitabine and azacitidine, demonstrating their ability to demethylate tumor suppressor genes and restore immune recognition, while HDAC inhibitors including vorinostat and entinostat have shown potential to upregulate NK-cell activating ligands and sensitize tumors to immune checkpoint blockade. However, the review is candid about the limits: while toxicity profiles were manageable, clinical efficacy was often limited when these agents were used as monotherapy, underscoring the need for rational combinations. Ongoing phase II and III trials are now evaluating DNMT inhibitors or HDAC inhibitors alongside PD-1 inhibitors such as pembrolizumab, aiming to overcome resistance and improve durable responses in advanced urothelial carcinoma. The authors describe this as a paradigm shift in which epigenetic agents are repositioned from cytotoxic modifiers to immune-sensitizing therapies capable of reprogramming the tumor microenvironment.
Significant obstacles remain before epigenetic-NK combinations can change clinical practice. The immunosuppressive tumor microenvironment impairs NK-cell infiltration, persistence and cytotoxicity, and promotes functional exhaustion. A recent study highlighted in the review showed that the BET family protein BRD4 cooperates with SMAD3 to promote transcription of the inhibitory receptors and immune checkpoints associated with NK-cell exhaustion, and that BET inhibition downregulated these receptors and restored NK-cell cytotoxicity against non-small cell lung cancer, a finding that may inform approaches in other solid tumors. Manufacturing is another bottleneck: Good Manufacturing Practice production of NK cell therapies demands stringent quality control, and the authors call for academic-industry partnerships, advances in cryopreservation and automation to produce off-the-shelf, cost-effective NK cell products. Engineered CAR-NK cells are also emerging, with CD24-directed CAR-NK-92 cells already demonstrating preclinical antitumor activity in bladder cancer models, and CD70-targeted CAR-NK approaches being pursued in renal cell carcinoma, although registered CAR-NK trials specifically for urothelial carcinoma remain lacking. Potential UC targets include Nectin-4, HER2, EGFR and CD24.
Looking ahead, the authors expect epigenetic profiling to become a stratification tool, with DNA methylation and histone modification patterns used as biomarkers to select patients, and with epigenetic modulators integrated with immune checkpoint inhibitors and antibody-drug conjugates such as enfortumab vedotin to enhance durable responses in advanced disease. Epigenetic preconditioning may also complement CAR-NK therapy, since DNMT and HDAC inhibitors can increase expression of ULBPs and MICA/B, and entinostat has been shown in preclinical models to sustain CAR expression and improve the persistence and antitumor activity of CAR-NK cells. Whether epigenetic preconditioning can overcome stromal barriers and improve CAR-NK homing, infiltration and persistence specifically in urothelial carcinoma, however, remains to be established. The review ultimately frames the combination of epigenetic agents with NK cell-based immunotherapy as a promising strategy to overcome resistance, while emphasizing that personalized, biomarker-driven treatment design will be essential to translate this molecular insight into real clinical benefit.
Subject of Research: Epigenetic regulation of natural killer cell-mediated antitumor immunity in urothelial carcinoma and the therapeutic potential of epigenetic drugs
Article Title: Epigenetic reprogramming of NK cell-mediated antitumor immunity in urothelial carcinoma: a mini-review
Article References: Kumari, H., Chou, C.-C., Lee, Y.-T., Shen, C.-H., & Chan, M. W. Y. (2026). Epigenetic reprogramming of NK cell-mediated antitumor immunity in urothelial carcinoma: a mini-review. Experimental Biology and Medicine, 251, Article 11373. https://doi.org/10.3389/ebm.2026.11373
Image Credits: AI Generated
Keywords: urothelial carcinoma, natural killer cells, epigenetics, DNA methylation, histone modification, NKG2D, HDAC inhibitors, DNMT inhibitors, immunotherapy, tumor microenvironment, CAR-NK cells, immune evasion
News Source: Nathaniel Bowman. (October 28, 2026). Epigenetic drugs may restore natural killer cell power against bladder cancer. Scienmag.
