DNA damage-induced activation of ATM promotes β-TRCP-mediated ARID1A ubiquitination and destruction in gastric cancer cells

Ataxia-Telangiectasia Mutated (ATM) gene signaling pathways in human cancers and their therapeutic implications

Cancer is a multifaceted disease driven by abnormal cell growth and poses a significant global health threat. The multifactorial causes, differences in individual susceptibility to therapeutic drugs, and induced drug resistance pose major challenges in addressing cancers effectively. One of the most important aspects in making cancers highly heterogeneous in their physiology lies in the genes involved and the changes occurring to some of these genes in malignant conditions. The Genetic factors have been implicated in the oncogenesis, progression, responses to treatment, and metastasis. One such gene that plays a key role in human cancers is the mutated form of the Ataxia-telangiectasia gene (ATM). ATM gene located on chromosome 11q23, plays a vital role in maintaining genomic stability. Understanding the genetic basis of A-T is crucial for diagnosis, management, and treatment. Breast cancer, lung cancer, prostate cancer, and gastric cancer exhibit varying relationships with the ATM gene and influence their pathways. Targeting the ATM pathway proves promising for enhancing treatment effectiveness, especially in conjunction with DNA damage response pathways. Analyzing the therapeutic consequences of ATM mutations, especially in these cancer types facilitates the approaches for early detection, intervention, development of personalized treatment approaches, and improved patient outcomes. This review emphasizes the role of the ATM gene in various cancers, highlighting its impact on DNA repair pathways and therapeutic responses.

Ubiquitination and deubiquitination in cancer: from mechanisms to novel therapeutic approaches

Ubiquitination, a pivotal posttranslational modification of proteins, plays a fundamental role in regulating protein stability. The dysregulation of ubiquitinating and deubiquitinating enzymes is a common feature in various cancers, underscoring the imperative to investigate ubiquitin ligases and deubiquitinases (DUBs) for insights into oncogenic processes and the development of therapeutic interventions. In this review, we discuss the contributions of the ubiquitin-proteasome system (UPS) in all hallmarks of cancer and progress in drug discovery. We delve into the multiple functions of the UPS in oncology, including its regulation of multiple cancer-associated pathways, its role in metabolic reprogramming, its engagement with tumor immune responses, its function in phenotypic plasticity and polymorphic microbiomes, and other essential cellular functions. Furthermore, we provide a comprehensive overview of novel anticancer strategies that leverage the UPS, including the development and application of proteolysis targeting chimeras (PROTACs) and molecular glues.

Role of AT-rich interaction domain 1A in gastric cancer immunotherapy: Preclinical and clinical perspectives

The application of immune checkpoint inhibitor (ICI) using monoclonal antibodies has brought about a profound transformation in the clinical outcomes for patients grappling with advanced gastric cancer (GC). Nonetheless, despite these achievements, the quest for effective functional biomarkers for ICI therapy remains constrained. Recent research endeavours have shed light on the critical involvement of modified epigenetic regulators in the pathogenesis of gastric tumorigenesis, thus providing a glimpse into potential biomarkers. Among these regulatory factors, AT-rich interaction domain 1A (ARID1A), a pivotal constituent of the switch/sucrose non-fermentable (SWI/SNF) complex, has emerged as a promising candidate. Investigations have unveiled the pivotal role of ARID1A in bridging the gap between genome instability and the reconfiguration of the tumour immune microenvironment, culminating in an enhanced response to ICI within the landscape of gastric cancer treatment. This all-encompassing review aims to dissect the potential of ARID1A as a valuable biomarker for immunotherapeutic approaches in gastric cancer, drawing from insights garnered from both preclinical experimentation and clinical observations.

Role of F-box proteins in human upper gastrointestinal tumors

Protein ubiquitination and degradation is an essential physiological process in almost all organisms. As the key participants in this process, the E3 ubiquitin ligases have been widely studied and recognized. F-box proteins, a crucial component of E3 ubiquitin ligases that regulates diverse biological functions, including cell differentiation, proliferation, migration, and apoptosis by facilitating the degradation of substrate proteins. Currently, there is an increasing focus on studying the role of F-box proteins in cancer. In this review, we present a comprehensive overview of the significant contributions of F-box proteins to the development of upper gastrointestinal tumors, highlighting their dual roles as both carcinogens and tumor suppressors. We delve into the molecular mechanisms underlying the involvement of F-box proteins in upper gastrointestinal tumors, exploring their interactions with specific substrates and their cross-talks with other key signaling pathways. Furthermore, we discuss the implications of F-box proteins in radiotherapy resistance in the upper gastrointestinal tract, emphasizing their potential as clinical therapeutic and prognostic targets. Overall, this review provides an up-to-date understanding of the intricate involvement of F-box proteins in human upper gastrointestinal tumors, offering valuable insights for the identification of prognostic markers and the development of targeted therapeutic strategies.

miRNA/epithelial-mesenchymal axis (EMT) axis as a key player in cancer progression and metastasis: A focus on gastric and bladder cancers

The metastasis a major hallmark of tumors that its significant is not only related to the basic research, but clinical investigations have revealed that majority of cancer deaths are due to the metastasis. The metastasis of tumor cells is significantly increased due to EMT mechanism and therefore, inhibition of EMT can reduce biological behaviors of tumor cells and improve the survival rate of patients. One of the gaps related to cancer metastasis is lack of specific focus on the EMT regulation in certain types of tumor cells. The gastric and bladder cancers are considered as two main reasons of death among patients in clinical level. Herein, the role of EMT in regulation of their progression is evaluated with a focus on the function of miRNAs. The inhibition/induction of EMT in these cancers and their ability in modulation of EMT-related factors including ZEB1/2 proteins, TGF-β, Snail and cadherin proteins are discussed. Moreover, lncRNAs and circRNAs in crosstalk of miRNA/EMT regulation in these tumors are discussed and final impact on cancer metastasis and response of tumor cells to the chemotherapy is evaluated. Moreover, the impact of miRNAs transferred by exosomes in regulation of EMT in these cancers are discussed.

The effects of ARID1A mutation in gastric cancer and its significance for treatment

Gastric cancer (GC) has emerged as a significant issue in public health all worldwide as a result of its high mortality rate and dismal prognosis. AT-rich interactive domain 1 A (ARID1A) is a vital component of the switch/sucrose-non-fermentable (SWI/SNF) chromatin remodeling complex, and ARID1A mutations occur in various tumors, leading to protein loss and decreased expression; it then affects the tumor biological behavior or prognosis. More significantly, ARID1A mutations will likely be biological markers for immune checkpoint blockade (ICB) treatment and selective targeted therapy. To provide theoretical support for future research on the stratification of individuals with gastric cancer with ARID1A as a biomarker to achieve precision therapy, we have focused on the clinical significance, predictive value, underlying mechanisms, and possible treatment strategies for ARID1A mutations in gastric cancer in this review.

Cigarette smoking is a secondary cause of folliculin loss

BACKGROUND

Birt-Hogg-Dubé syndrome (BHD) is a clinical syndrome manifesting with cystic lung disease and pneumothorax. Features of BHD result from the loss-of-function mutations of the folliculin (FLCN) gene. Chronic obstructive pulmonary disease (COPD), characterised by an irreversible airflow limitation, is primarily caused by cigarette smoking.

OBJECTIVE

Given that COPD often shares structural features with BHD, we investigated the link between COPD, cigarette smoke (CS) exposure and FLCN expression.

METHODS

We measured the expression of FLCN in human COPD lungs and CS-exposed mouse lungs, as well as in CS extract (CSE)-exposed immortalised human airway epithelial cells by immunoblotting.

RESULTS

We found that the lung FLCN protein levels in smokers with COPD and CS exposure mice exhibit a marked decrease compared with smokers without COPD and room air exposure mice, respectively. We confirmed CS induced degradation of FLCN in immortalised human bronchial epithelial Beas-2B cells via ubiquitin proteasome system. Further, siRNA targeting FLCN enhanced CSE-induced cytotoxicity. By contrast, FLCN overexpression protected cells from CSE-induced cytotoxicity. We found that FBXO23, the ubiquitin E3 ligase subunit, specifically binds to and targets FLCN for degradation. Inhibition of ATM (ataxia-telangiectasia mutated) attenuated CSE induced FLCN degradation, suggesting a role of ATM in FLCN proteolysis. We further confirmed that the mutant of major FLCN phosphorylation site serine 62A is resistant to CSE-induced degradation and cytotoxicity.

CONCLUSIONS

Our study demonstrates that CS exposure is a secondary cause of FLCN deficiency due to the enhanced proteolysis, which promoted airway epithelial cell death.

ARID1A loss induces polymorphonuclear myeloid-derived suppressor cell chemotaxis and promotes prostate cancer progression

Chronic inflammation and an immunosuppressive microenvironment promote prostate cancer (PCa) progression and diminish the response to immune checkpoint blockade (ICB) therapies. However, it remains unclear how and to what extent these two events are coordinated. Here, we show that ARID1A, a subunit of the SWI/SNF chromatin remodeling complex, functions downstream of inflammation-induced IKKβ activation to shape the immunosuppressive tumor microenvironment (TME). Prostate-specific deletion of Arid1a cooperates with Pten loss to accelerate prostate tumorigenesis. We identify polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) as the major infiltrating immune cell type that causes immune evasion and reveal that neutralization of PMN-MDSCs restricts the progression of Arid1a-deficient tumors. Mechanistically, inflammatory cues activate IKKβ to phosphorylate ARID1A, leading to its degradation via β-TRCP. ARID1A downregulation in turn silences the enhancer of A20 deubiquitinase, a critical negative regulator of NF-κB signaling, and thereby unleashes CXCR2 ligand-mediated MDSC chemotaxis. Importantly, our results support the therapeutic strategy of anti-NF-κB antibody or targeting CXCR2 combined with ICB for advanced PCa. Together, our findings highlight that the IKKβ/ARID1A/NF-κB feedback axis integrates inflammation and immunosuppression to promote PCa progression.

DNA Damage Repair and Current Therapeutic Approaches in Gastric Cancer: A Comprehensive Review

DNA in cells is frequently damaged by endogenous and exogenous agents. However, comprehensive mechanisms to combat and repair DNA damage have evolved to ensure genomic stability and integrity. Improper DNA damage repair may result in various diseases, including some types of tumors and autoimmune diseases. Therefore, DNA damage repair mechanisms have been proposed as novel antitumor drug targets. To date, numerous drugs targeting DNA damage mechanisms have been developed. For example, PARP inhibitors that elicit synthetic lethality are widely used in individualized cancer therapies. In this review, we describe the latent DNA damage repair mechanisms in gastric cancer, the types of DNA damage that can contribute to the development of gastric cancer, and new therapeutic approaches for gastric cancer that target DNA damage repair pathways.

Methionine and leucine induce ARID1A degradation to promote mTOR expression and milk synthesis in mammary epithelial cells

Amino acids can activate mTOR to promote milk synthesis in mammary epithelial cells (MECs), but the underlying molecular mechanism is still largely unknown. The objective is to investigate the regulatory mechanism of amino acids (Met and Leu) in stimulating mRNA expression of mTOR in MECs. We found that the protein abundance of AT-rich interaction domain 1A (ARID1A) was poorly expressed in mouse mammary gland tissues of lactating period. ARID1A knockdown and gene activation experiments detected whether ARID1A negatively regulated milk protein and fat synthesis in bovine MECs, cell proliferation and the expression and activation of mTOR. ChIP-PCR detected that ARID1A, H3K27ac, H3K27me3 and H3K4me3 all bound to the mTOR promoter at -548∼-793 nt. Knockdown or gene activation of ARID1A enhanced or weakened the binding of H3K27ac on the mTOR promoter, respectively. The stimulation of Met and Leu on mTOR expression and phosphorylation were eliminated by ARID1A gene activation. Furthermore, Met and Leu decreased the protein level of ARID1A through ubiquitination and proteasomal degradation. TRIM21 bound to ARID1A, and TRIM21 knockdown blocked the stimulation of Met and Leu on ARID1A degradation. In summary, these data reveal that ARID1A blocks Met and Leu signaling to mTOR gene transcription through inhibiting H3K27ac deposition on its promoter, and Met and Leu decrease ARID1A protein level through TRIM21-mediated ubiquitination and proteasomal degradation. Our findings uncover that Met and Leu promote mTOR expression for milk synthesis through the TRIM21-ARID1A signaling pathway, providing a novel theoretical basis for the application of amino acids in milk production.

mTORC1 Promotes ARID1A Degradation and Oncogenic Chromatin Remodeling in Hepatocellular Carcinoma

The SWI/SNF chromatin remodeling complexes control accessibility of chromatin to transcriptional and coregulatory machineries. Chromatin remodeling plays important roles in normal physiology and diseases, particularly cancer. The ARID1A-containing SWI/SNF complex is commonly mutated and thought to be a key tumor suppressor in hepatocellular carcinoma (HCC), but its regulation in response to oncogenic signals remains poorly understood. mTOR is a conserved central controller of cell growth and an oncogenic driver of HCC. Remarkably, cancer mutations in mTOR and SWI/SNF complex are mutually exclusive in human HCC tumors, suggesting that they share a common oncogenic function. Here, we report that mTOR complex 1 (mTORC1) interact with ARID1A and regulates ubiquitination and proteasomal degradation of ARID1A protein. The mTORC1-ARID1A axis promoted oncogenic chromatin remodeling and YAP-dependent transcription, thereby enhancing liver cancer cell growth in vitro and tumor development in vivo. Conversely, excessive ARID1A expression counteracted AKT-driven liver tumorigenesis in vivo. Moreover, dysregulation of this axis conferred resistance to mTOR-targeted therapies. These findings demonstrate that the ARID1A-SWI/SNF complex is a regulatory target for oncogenic mTOR signaling, which is important for mTORC1-driven hepatocarcinogenesis, with implications for therapeutic interventions in HCC. SIGNIFICANCE: mTOR promotes oncogenic chromatin remodeling by controlling ARID1A degradation, which is important for liver tumorigenesis and response to mTOR- and YAP-targeted therapies in hepatocellular carcinoma.See related commentary by Pease and Fernandez-Zapico, p. 5608.

TRIM32/USP11 Balances ARID1A Stability and the Oncogenic/Tumor-Suppressive Status of Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is an aggressive epithelial malignancy, yet the molecular mechanisms underlying SCC development are elusive. ARID1A is frequently mutated in various cancer types, but both mutation rates and expression levels of ARID1A are ubiquitously low in SCCs. Here, we reveal that excessive protein degradation mediated by the ubiquitin-proteasome system (UPS) contributes to the loss of ARID1A expression in SCC. We identify that the E3 ligase TRIM32 and the deubiquitinase USP11 play key roles in controlling ARID1A stability. TRIM32 depletion inhibits SCC cell proliferation, metastasis, and chemoresistance by stabilizing ARID1A, while USP11 depletion promotes SCC development by promoting ARID1A degradation. We show that syndecan-2 (SDC2) is the downstream target of both ARID1A and USP11 and that SDC2 depletion abolishes the oncogenic function of ARID1A loss. In summary, our data reveal UPS-mediated protein degradation as a mechanism underlying ARID1A loss and propose an important role for the TRIM32/USP11-ARID1A-SDC2 axis in SCC.

Remodeling of the ARID1A tumor suppressor

In recent years, AT-rich interactive domain-containing protein 1A (ARID1A) has been widely accepted as a bona fide tumor suppressor due to its essential role in preventing tumorigenesis and tumor progression in both mouse and human contexts. ARID1A shows high mutation frequencies in both cancers and preneoplastic lesions. The loss of ARID1A expression in cancer cells leads to increases in cell proliferation, invasion and migration and reductions in cell apoptosis and chemosensitivity. The tumor-suppressive role of ARID1A is mainly attributed to its regulation of gene transcription, which can be induced either directly by chromatin remodeling or indirectly by affecting histone modifications. ARID1A also acts independently of its cardinal transcription-regulating mechanisms, which include interfering with protein-protein interactions. Interestingly, nonmutational mechanisms, such as regulation by DNA hypermethylation, microRNAs, and ubiquitinases/deubiquitinases, have provided another perspective on ARID1A inactivation in cancer. Since the critical tumor-suppressive role of ARID1A has been revealed, several studies have attempted to identify synthetic lethal targets with ARID1A mutation/inactivation as an alternative strategy for cancer treatment.

The characteristics and roles of β-TrCP1/2 in carcinogenesis

β-transducin repeat-containing protein (β-TrCP), one of the well-characterized F-box proteins, acts as a substrate receptor and constitutes an active SCF^β-TrCP E3 ligase with a scaffold protein CUL1, a RING protein RBX1, and an adaptor protein SKP1. β-TrCP plays a critical role in the regulation of various physiological and pathological processes, including signal transduction, cell cycle progression, cell migration, DNA damage response, and tumorigenesis, by governing burgeoning amounts of key regulators for ubiquitination and proteasomal degradation. Given that a variety of β-TrCP substrates are well-known oncoproteins and tumor suppressors, and dysregulation of β-TrCP is frequently identified in human cancers, β-TrCP plays a vital role in carcinogenesis. In this review, we first briefly introduce the characteristics of β-TrCP1, β-TrCP2, and SCF^β-TrCP ubiquitin ligase, and then discuss SCF^β-TrCP ubiquitin ligase regulated biological processes by targeting its substrates for degradation. Moreover, we summarize the regulation of β-TrCP1 and β-TrCP2 at multiple layers and further discuss the various roles of β-TrCP1 and β-TrCP2 in human cancer, functioning as either an oncoprotein or a tumor suppressor in a manner dependent of cellular context. Finally, we provide novel insights for future perspectives on the potential of targeting β-TrCP1 and β-TrCP2 for cancer therapy.

Downregulation of ARID1A in gastric cancer cells: a putative protective molecular mechanism against the Harakiri-mediated apoptosis pathway

This study was designed to unravel the pathobiological role of impaired ARID1A expression in gastric carcinogenesis. We examined ARID1A expression immunohistochemically in 98 gastric cancer tissue specimens with regard to the clinicopathological features. Based on the proportion and intensity of ARID1A immunoreactivity at the cancer invasion front, we subdivided the specimens into low- and high-expression ARID1A groups. Notably, low ARID1A expression was significantly correlated with overall survival of the patients. Subsequently, we determined the molecular signature that distinguished ARID1A low/poor prognosis from ARID1A high/good prognosis gastric cancers. A comprehensive gene profiling analysis followed by immunoblotting revealed that a mitochondrial apoptosis mediator, Harakiri, was less expressed in ARID1A low/poor prognosis than ARID1A high/good prognosis gastric cancers. siRNA-mediated ARID1A downregulation significantly reduced expression of the Harakiri molecule in cultured gastric cancer cells. Interestingly, downregulation of ARID1A conferred resistance to apoptosis induced by the mitochondrial metabolism inhibitor, devimistat. In contrast, enforced Harakiri expression restored sensitivity to devimistat-induced apoptosis in ARID1A downregulated gastric cancer cells. The present findings indicate that impaired ARID1A expression might lead to gastric carcinogenesis, putatively through gaining resistance to the Harakiri-mediated apoptosis pathway.

Functional roles of E3 ubiquitin ligases in gastric cancer

To date, >650 E3 ubiquitin ligases have been described in humans, including >600 really interesting new genes (RINGs), 28 homologous to E6-associated protein C-terminus (HECTs) and several RING-in-between-RINGs. They are considered key regulators and therapeutic targets of many types of human cancers, including gastric cancer (GC). Among them, some RING and HECT E3 ligases are closely related to the proliferation, infiltration and prognosis of GC. During the past few years, abnormal expressions and functions of many E3 ligases have been identified in GC. However, the functional roles of E3 ligases in GC have not been fully elucidated. The present article focuses on the functional roles of E3 ligases related to the proteasome in GC. In this comprehensive review, the latest research progress on E3 ligases involved in GC and elaborate their structure, classification, functional roles and therapeutic value in GC was summarized. Finally, 30 E3 ligases that serve essential roles in regulating the development of GC were described. Some of these ligases may serve as oncogenes or tumor suppressors in GC, whereas the pathological mechanism of others needs further study; for example, constitutive photomorphogenic 1. In conclusion, the present review demonstrated that E3 ligases are crucial tumor regulatory factors and potential therapeutic targets in GC. Therefore, more studies should focus on the therapeutic targeting of E3 ligases in GC.

The roles of mutated SWI/SNF complexes in the initiation and development of hepatocellular carcinoma and its regulatory effect on the immune system: A review

Hepatocellular carcinoma (HCC) is a primary liver malignancy with a high global prevalence and a dismal prognosis. Studies are urgently needed to examine the molecular pathogenesis and biological characteristics of HCC. Chromatin remodelling, an integral component of the DNA damage response, protects against DNA damage‐induced genome instability and tumorigenesis by triggering the signalling events that activate the interconnected DNA repair pathways. The SWI/SNF complexes are one of the most extensively investigated adenosine triphosphate‐dependent chromatin remodelling complexes, and mutations in genes encoding SWI/SNF subunits are frequently observed in various human cancers, including HCC. The mutated SWI/SNF complex subunits exert dual functions by accelerating or inhibiting HCC initiation and progression. Furthermore, the abnormal SWI/SNF complexes influence the transcription of interferon‐stimulated genes, as well as the differentiation, activation and recruitment of several immune cell types. In addition, they exhibit synergistic effects with immune checkpoint inhibitors in the treatment of diverse tumour types. Therefore, understanding the mutations and deficiencies of the SMI/SNF complexes, together with the associated functional mechanisms, may provide a novel strategy to treat HCC through targeting the related genes or modulating the tumour microenvironment.