Histone methyltransferase KMT2D cooperates with MEF2A to promote the stem-like properties of oral squamous cell carcinoma

Evolving role of deubiquitinating enzymes in oral cancer (Review)

Oral cancer affects the mucosal epithelium located within the oral cavity. The prevalence of oral cancer is projected to increase by ~40% by 2040, leading to a subsequent rise in mortality rates. Oral carcinogenesis is complex and multifactorial and numerous signaling pathways are involved in disease development. Deubiquitination is commonly involved in the post-translational process of proteins, and serves a key role in tumorigenesis and cancer development. The present review aims to discuss the function of deubiquitinating enzymes (DUBs) in oral cancer, with a particular focus on oral squamous cell carcinoma (OSCC). The present review also aims to investigate the functional mechanisms, tumorigenic regulation and therapeutic targets of DUBs in OSCC, which may potentially provide a novel theoretical basis for the utilization of DUBs as molecular targets in the treatment of OSCC in the future.

KMT2D: A key emerging epigenetic regulator in head and neck diseases and tumors

Histone modifications are critical determinants of chromatin accessibility and gene expression, both of which are intrinsically linked to human development and disease. Lysine methyltransferase 2D (KMT2D), a prominent member of the H3K4 methyltransferase family, is ubiquitously expressed across human tissues. Recent studies have found that it can regulate gene expression and signal pathway opening and closing in more than one way, playing an important role in cell proliferation and cell cycle homeostasis. Although previous studies have identified KMT2D as a potentially pivotal factor in the development and pathology of head and neck tissues, the regulatory networks associated with KMT2D in various complex head and neck diseases remain incompletely elucidated. This review seeks to consolidate recent findings on KMT2D's involvement in head and neck diseases, thereby laying the groundwork for future research into its mechanistic role in disease progression. A deeper understanding of KMT2D's functions and regulatory mechanisms is essential for advancing our comprehension of histone modifications and for the development of diagnostic tools and targeted therapeutic strategies for head and neck diseases.

Targeting Epigenetic Dysregulations in Head and Neck Squamous Cell Carcinoma

Head and neck squamous cell carcinoma (HNSCC) is one of the deadliest human cancers, with the overall 5-year survival rate stagnating in recent decades due to the lack of innovative treatment approaches. Apart from the recently Food and Drug Administration-approved epidermal growth factor receptor inhibitor and immune checkpoint inhibitor, alternative therapeutic strategies that target epigenetic abnormalities, an emerging cancer hallmark, remain to be fully explored. A pathological epigenetic landscape, characterized by widespread reprogramming of chromatin modifications such as DNA methylation and histone modifications, which drives transcription deregulation and genome reorganization, has been extensively documented in numerous cancers, including HNSCC. Growing evidence indicates that these frequent epigenomic alterations play pivotal roles in regulating malignant transformation, promoting metastasis and invasion, and reshaping the tumor microenvironment. Furthermore, these epigenetic changes also present unique vulnerabilities that open new avenues for identifying novel prognostic biomarkers and developing targeted antitumor therapies. In this review, we summarize recent discoveries of epigenetic dysregulations in HNSCC, with a focus on deregulated chromatin modifications, which include aberrant DNA methylation, oncohistone H3 lysine 36 to methionine (H3K36M) mutation, as well as recurrent mutations or altered expression of chromatin-modifying enzymes such as NSD1, EZH2, and KMT2C/D. Importantly, we discuss the various molecular mechanisms underlying the contributions of these epigenetic alterations to HNSCC development, particularly their involvement in deregulated cell proliferation and cell death, metabolic reprogramming, tumor immune evasion, and phenotypic plasticity. Finally, we conclude by highlighting the translational and clinical implications of targeting the epigenetic machinery, which offers promising prospects for overcoming resistance to conventional radiotherapy/chemotherapy and enhancing the response to immunotherapy in HNSCC.

Molecular insight into histone methylation as a novel target for oral squamous cell carcinoma: future hope in personalised medicine

Oral squamous cell carcinoma (OSCC) is the most prevalent type of malignant epithelial neoplasm that affects the oral cavity. It has been a significant health concern in many countries for a long time since it was usually treated with surgery, radiation, and/or chemotherapy. Drug resistance is the primary issue in patient populations and scientific research, which promotes OSCC tumour cell invasion and migration. Thus, identifying highly specific therapeutic targets could be the potential approach for more successful treatment of OSCC. It is still challenging to understand the genetic causes of oral carcinogenesis due to its highly varied clinic-pathological parameters. It is important to remember that signaling channels and complexes that affect chromatin accessibility control gene expression, which in turn affects cell development and differentiation. Histones undergo post-translational alteration to give this platform. Understanding the processes of gene regulation through histone methylation and its modifications could enhance the early detection, prognostic prediction, and therapy of OSCC. To be properly used as a therapeutic target, histone methylation in OSCC requires more investigation. This review details the dysregulated histone methylation and the modifying enzymes linked to the development and aetiology of OSCC. Furthermore, the part that lysine methylation plays in cell migration, chemo-resistance, and OSCC invasion is also investigated.

MEF2A, a gene associated with mitochondrial biogenesis, promotes drug resistance in gastric cancer

Chemotherapeutic resistance is a major obstacle to the effectiveness of cisplatin-based chemotherapy for gastric cancer (GC), leading to treatment failure and poor survival rates. However, the underlying mechanisms are not fully understood. Our study demonstrated that the transcription factor myocyte enhancer factor 2A (MEF2A) plays a role in chemotherapeutic drug resistance by regulating the transcription of PGC1α and KEAP1, promoting mitochondrial biogenesis. It was found that increased MEF2A expression is linked with poor prognosis, cisplatin insensitivity, and mitochondrial function in GC. MEF2A overexpression significantly decreases GC cell sensitivity in vitro and in vivo, while MEF2A knockdown enhances the sensitivity to cisplatin. Mechanistically, MEF2A activates the transcription of PGC1α, leading to increased mitochondrial biogenesis. In addition, MEF2A inhibits KEAP1 transcription, reduces NRF2 ubiquitination degradation, and activates the KEAP1/NRF2 signaling pathway, which modulates the reactive oxygen species level. The present study identifies MEF2A as a new critical oncogene involved in GC chemoresistance, suggesting a novel therapeutic target for GC.

MEF2A restrains cisplatin resistance in gastric cancer cells by modulating NFKBIA/NF-κB signaling pathway

Cisplatin (DDP) resistance represents a pivotal contributing factor to chemotherapy failure and adverse patient outcomes in gastric cancer (GC). The objective of the present study was to investigate the roles and underlying mechanisms of myocyte enhancer factor 2A (MEF2A) in DDP resistance in GC. GC cell line AGS and MKN-45 cells were applied to construct DDP-resistant cells. CCK-8, colony formation, and flow cytometry methods were validated for determining the IC50 value of DDP and cell survival of GC cells. qRT-PCR and western blotting analysis quantified the molecular levels at mRNA and protein, respectively. Chromatin immunoprecipitation and dual-luciferase assays validated the molecular relationship between MEF2A and NF-κB inhibitor alpha (NFKBIA). Roles of MEF2A in in vivo were performed employing a xenograft model. The results showed that NFKBIA was greatly decreased in DDP-resistant AGS and MKN-45 cells compared to their respective parental cells. Increasing NFKBIA expression impaired the IC50 value of DDP and cell survival in DDP-resistant cells, while these alterations were rescued upon TNF-α treatment. Mechanistically, MEF2A acts as a transcriptional activator of NFKBIA, which led to the reduction of phosphorylation of p65 and cytoplasmic retention. Moreover, MEF2A overexpression promoted the sensitivity of GC cells to DDP and tumor growth, whereas these effects were partially reversed by NFKBIA silence. Collectively, MEF2A mitigated the DDP resistance in GC cells by modulatory actions on the NFKBIA/NF-κB signaling, shedding light on MEF2A/NFKBIA might be a promising intervention target for improving DDP resistance in GC.

The biomarkers for maintenance Cancer stem cell features can be applicable in precision medicine of head and neck squamous cell carcinoma

Cancer stem cells (CSCs) play a crucial role in tumor relapse, proliferation, invasion, and drug resistance in head and neck squamous cell carcinoma (HNSCC). This narrative review aims to synthesize data from articles published between 2019 and 2023 on biomarkers for detecting CSCs in HNSCC and changes in molecular pathways, genetics, epigenetics, and non-coding RNAs (ncRNAs) in CSCs relevant to precision medicine approaches in HNSCC management. The search encompassed 41 in vitro studies and 22 clinical studies. CSCs exhibit diverse molecular profiles and unique biomarker expression patterns, offering significant potential for HNSCC diagnosis, treatment, and prognosis, thereby enhancing patient survival. Their remarkable self-renewal ability and adaptability are closely linked to tumorigenicity development and maintenance. Assessing biomarkers before and after therapy can aid in identifying various cell types associated with cancer progression and relapse. Screening for CSCs, senescent tumor cells, and cells correlated with the senescence process post-treatment has proven highly beneficial. However, the clinical application of precision medicine in HNSCC management is hindered by the lack of specific and definitive CSC biomarkers. Furthermore, our limited understanding of CSC plasticity, governed by genomic, transcriptomic, and epigenomic alterations during tumorigenesis, as well as the bidirectional interaction of CSCs with the tumor microenvironment, underscores the need for further research. Well-designed studies involving large patient cohorts are, therefore, essential to establish a standardized protocol and address these unresolved queries.

Histone-methyltransferase KMT2D deficiency impairs the Fanconi anemia/BRCA pathway upon glycolytic inhibition in squamous cell carcinoma

Histone lysine methyltransferase 2D (KMT2D) is the most frequently mutated epigenetic modifier in head and neck squamous cell carcinoma (HNSCC). However, the role of KMT2D in HNSCC tumorigenesis and whether its mutations confer any therapeutic vulnerabilities remain unknown. Here we show that KMT2D deficiency promotes HNSCC growth through increasing glycolysis. Additionally, KMT2D loss decreases the expression of Fanconi Anemia (FA)/BRCA pathway genes under glycolytic inhibition. Mechanistically, glycolytic inhibition facilitates the occupancy of KMT2D to the promoter/enhancer regions of FA genes. KMT2D loss reprograms the epigenomic landscapes of FA genes by transiting their promoter/enhancer states from active to inactive under glycolytic inhibition. Therefore, combining the glycolysis inhibitor 2-DG with DNA crosslinking agents or poly (ADP-ribose) polymerase (PARP) inhibitors preferentially inhibits tumor growth of KMT2D-deficient mouse HNSCC and patient-derived xenografts (PDXs) harboring KMT2D-inactivating mutations. These findings provide an epigenomic basis for developing targeted therapies for HNSCC patients with KMT2D-inactivating mutations.

Knockdown of Kmt2d leads to growth impairment by activating the Akt/β-catenin signaling pathway

The KMT2D variant-caused Kabuki syndrome (KS) is characterized by short stature as a prominent clinical characteristic. The initiation and progression of body growth are fundamentally influenced by chondrocyte proliferation. Uncertainty persists regarding the possibility that KMT2D deficiency affects growth by impairing chondrocyte proliferation. In this study, we used the CRISPR/Cas13d technique to knockdown kmt2d in zebrafish embryos and lentivirus to create a stable Kmt2d gene knockdown cell line in chondrocytes (ATDC5 cells). We also used CCK8 and flow cytometric studies, respectively, to determine proliferation and cell cycle state. The relative concentrations of phosphorylated Akt (ser473), phosphorylated β-catenin (ser552), and cyclin D1 proteins in chondrocytes and zebrafish embryos were determined by using western blots. In addition, Akt inhibition was used to rescue the phenotypes caused by kmt2d deficiency in chondrocytes, as well as a zebrafish model that was generated. The results showed that a knockdown of kmt2d significantly decreased body length and resulted in aberrant cartilage development in zebrafish embryos. Furthermore, the knockdown of Kmt2d in ATDC5 cells markedly increased proliferation and accelerated the G1/S transition. In addition, the knockdown of Kmt2d resulted in the activation of the Akt/β-catenin signaling pathway in ATDC5 cells. Finally, Akt inhibition could partly rescue body length and chondrocyte development in the zebrafish model. Our study demonstrated that KMT2D modulates bone growth conceivably via regulation of the Akt/β-catenin pathway.

Exploring Potential Epigenetic Biomarkers for Colorectal Cancer Metastasis

Metastatic progression is a complex, multistep process and the leading cause of cancer mortality. There is growing evidence that emphasises the significance of epigenetic modification, specifically DNA methylation and histone modifications, in influencing colorectal (CRC) metastasis. Epigenetic modifications influence the expression of genes involved in various cellular processes, including the pathways associated with metastasis. These modifications could contribute to metastatic progression by enhancing oncogenes and silencing tumour suppressor genes. Moreover, specific epigenetic alterations enable cancer cells to acquire invasive and metastatic characteristics by altering cell adhesion, migration, and invasion-related pathways. Exploring the involvement of DNA methylation and histone modification is crucial for identifying biomarkers that impact cancer prediction for metastasis in CRC. This review provides a summary of the potential epigenetic biomarkers associated with metastasis in CRC, particularly DNA methylation and histone modifications, and examines the pathways associated with these biomarkers.

The repertoire of mutational signatures in tobacco- and non-tobacco-induced oral cancer

The use of tobacco products is one of the established contributors toward the development and spread of oral cancer. Additionally, recent research has indicated oral microbiome, infections with Human papilloma virus (HPV), Epstein-Barr virus (EBV), Candida as significant contributing factors to this disease along with lifestyle habits. Deregulation of cellular pathways envisaging metabolism, transcription, translation, and epigenetics caused by these risk factors either individually or in unison is manifold, resulting in the increased risk of oral cancer. Globally, this cancer continues to exist as one of the major causes of cancer-related mortalities; the numbers in the developing South Asian countries clearly indicate yearly escalation. This review encompasses the variety of genetic modifications, including adduct formation, mutation (duplication, deletion, and translocation), and epigenetic changes evident in oral squamous cell carcinoma (OSCC). In addition, it highlights the interference caused by tobacco products in Wnt signaling, PI3K/Akt/mTOR, JAK-STAT, and other important pathways. The information provided also ensures a comprehensive and critical revisit to non-tobacco-induced OSCC. Extensive literature survey and analysis has been conducted to generate the chromosome maps specifically highlighting OSCC-related mutations with the potential to act as spectacles for the early diagnosis and targeted treatment of this disease cancer.

Oral squamous cell carcinomas: state of the field and emerging directions

Oral squamous cell carcinoma (OSCC) develops on the mucosal epithelium of the oral cavity. It accounts for approximately 90% of oral malignancies and impairs appearance, pronunciation, swallowing, and flavor perception. In 2020, 377,713 OSCC cases were reported globally. According to the Global Cancer Observatory (GCO), the incidence of OSCC will rise by approximately 40% by 2040, accompanied by a growth in mortality. Persistent exposure to various risk factors, including tobacco, alcohol, betel quid (BQ), and human papillomavirus (HPV), will lead to the development of oral potentially malignant disorders (OPMDs), which are oral mucosal lesions with an increased risk of developing into OSCC. Complex and multifactorial, the oncogenesis process involves genetic alteration, epigenetic modification, and a dysregulated tumor microenvironment. Although various therapeutic interventions, such as chemotherapy, radiation, immunotherapy, and nanomedicine, have been proposed to prevent or treat OSCC and OPMDs, understanding the mechanism of malignancies will facilitate the identification of therapeutic and prognostic factors, thereby improving the efficacy of treatment for OSCC patients. This review summarizes the mechanisms involved in OSCC. Moreover, the current therapeutic interventions and prognostic methods for OSCC and OPMDs are discussed to facilitate comprehension and provide several prospective outlooks for the fields.

Histone modifications in drug-resistant cancers: From a cancer stem cell and immune evasion perspective

The development and immune evasion of cancer stem cells (CSCs) limit the efficacy of currently available anticancer therapies. Recent studies have shown that epigenetic reprogramming regulates the expression of characteristic marker proteins and tumor plasticity associated with cancer cell survival and metastasis in CSCs. CSCs also possess unique mechanisms to evade external attacks by immune cells. Hence, the development of new strategies to restore dysregulated histone modifications to overcome cancer resistance to chemotherapy and immunotherapy has recently attracted attention. Restoring abnormal histone modifications can be an effective anticancer strategy to increase the therapeutic effect of conventional chemotherapeutic and immunotherapeutic drugs by weakening CSCs or by rendering them in a naïve state with increased sensitivity to immune responses. In this review, we summarize recent findings regarding the role of histone modifiers in the development of drug-resistant cancer cells from the perspectives of CSCs and immune evasion. In addition, we discuss attempts to combine currently available histone modification inhibitors with conventional chemotherapy or immunotherapy.

The expression and methylation of PITX genes is associated with the prognosis of head and neck squamous cell carcinoma

Background: The PITX gene family, comprising PITX1, PITX2, and PITX3, is critical in organogenesis and has been evolutionary conserved in animals. PITX genes are associated with the advanced progression and poor prognosis of multiple cancers. However, the relationship between the PITX genes and head and neck squamous cell carcinoma (HNSC) has not been reported.

Methods: We used data from The Cancer Genome Atlas (TCGA) to analyze the association between PITX mRNA expression and clinicopathological parameters of patients with HNSC. The prognostic value of PITX genes was evaluated using the Kaplan-Meier plotter. Multivariate Cox analysis was used to screen out prognosis-associated genes to identify better prognostic indicators. The potential roles of PITX1 and PITX2 in HNSC prognosis were investigated using the protein-protein interaction (PPI) network, Gene Ontology (GO) analysis, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The correlation between PITX1 and PITX2 expression or methylation and immune cell infiltration was evaluated using the tumor-immune system interaction database (TISIDB). MethSurv was used to identify DNA methylation and its effect on HNSC prognosis.

Results:PITX genes expression was correlated with different cancers. PITX1 and PITX2 expression was lower in the patients with HNSC. In HNSC, PITX1 expression was significantly related to the clinical stage, histologic grade, and N stage, while PITX2 expression was only significantly related to the histologic grade. The high expression of PITX3 was significantly related to the histologic grade, T stage, and N stage. Survival analysis revealed that PITX genes had prognostic value in HNSC, which was supported by multivariate Cox analysis. PPI network and enrichment analysis showed that the genes interacting with PITX1 and PITX2 belonged predominantly to signaling pathways associated with DNA binding and transcription. Of the CpG DNA methylation sites in PITX1 and PITX2, 28 and 22 were related to the prognosis of HNSC, respectively. Additionally, PITX1 and PITX2 expression and methylation was associated with tumor-infiltrating lymphocytes (TILs).

Conclusion: The PITX genes were differentially expressed in patients with HNSC, highlighting their essential role in DNA methylation and tumor-infiltrating immune cell regulation, as well as overall prognostic value in HNSC.