Overexpression of absent in melanoma 2 in oral squamous cell carcinoma contributes to tumor progression

Molecular characteristics of oligomeric protein complexes AIM2 and TM4SF19 and their association with the pathogenesis of oral squamous cell carcinoma: Potential biomarkers

The aim of this study was to reveal the molecular characteristics of AIM 2 and TM4SF19 oligomeric protein complexes in oral squamous cell carcinoma (OSCC) and to evaluate their potential as potential biomarkers. The expression levels of AIM 2 and TM4SF19 in tumor and normal oral mucosa tissues were determined by immunohistochemistry, and their mRNA and protein levels were quantified by quantitative real-time PCR (qRT-PCR) and Western blot. Cell models for overexpression and knockdown of AIM 2 and TM4SF19 were constructed to investigate their effects on the proliferation, migration and invasion of OSCC cells. Finally, the function of AIM 2 and TM4SF19 in OSCC cells was further investigated by the apoptosis assay and cell cycle analysis. It was found that compared with normal oral mucosa, the expression of AIM2 in OSCC was significantly down-regulated, while the expression of TM4SF19 showed the opposite trend, that is, it was up-regulated in tumor tissues. qRT-PCR and Western blot results further confirmed this finding and showed that AIM2 and TM4SF19 expression levels were closely correlated with clinical stage and lymph node metastasis in OSCC patients. The overexpression of TM4SF19 promoted the malignant behavior of tumor cells. In contrast, the knock down of AIM2 and the knock down of TM4SF19 produced the opposite effect. Therefore, AIM2 and TM4SF19 are expected to be potential biomarkers for OSCC, providing new ideas for the early diagnosis and treatment of OSCC.

Role of the AIM2 Inflammasome in Cancer: Potential Therapeutic Strategies

Absent in melanoma 2 (AIM2) is a member of the innate immune sensors that recognizes cytosolic nucleic acids, leading to inflammasome assembly. In recent years, several studies in the oncology field have highlighted the presence of cytoplasmic double-stranded DNA (dsDNA) following necrosis and/or genomic instability, which is typical of malignant transformation. The recognition of dsDNA by the AIM2 inflammasome either in cancer cells or in immune cells can further exacerbate inflammatory processes on the basis of cancer progression. In this context, the role of AIM2 in cancer is still controversial in that some authors assume that AIM2 activation has pro-tumor activities, while others define it as anti-tumor. This discrepancy may be due to the nature of the cells where AIM2 is expressed or the histology of the tumor. This review aims to provide an overview of the controversial role of AIM2 in cancer, taking into consideration the pharmacological tools currently available to modulate AIM2 activity in cancer.

DNA hypermethylation of tumor suppressor genes among oral squamous cell carcinoma patients: a prominent diagnostic biomarker

Oral Squamous Cell Carcinoma is a globally revealing form of oral malignancy. Epigenetics, which studies genetic modifications in gene expression without altering the sequence of DNA, is crucial for understanding OSCC. Key epigenetic modifications such as histone modifications, DNA methylation, and microRNA regulation play significant roles in Oral carcinoma. Aberrant methylation of DNA of tumor suppressor genes which leads to their inactivation, promoting cancer development, and specific methylation patterns are emerging as biomarkers for early OSCC detection.Current treatments like surgery, radiotherapy, and chemotherapy often fall short, prompting research into epigenetic therapies. Agents like DNMT and HDAC inhibitors demonstrate the potential for reversing aberrant epigenetic patterns, perhaps reactivating silenced TSGs, and suppressing oncogenes. Despite early promise, the development of effective combination medicines and the identification of reliable biomarkers continue to present challenges.In OSCC, resistance to therapy is also influenced by epigenetic processes. Aberrant DNA methylation and changes in histone modifications impact genes involved in medication metabolism and the survival of cells. Enhancing treatment efficacy and overcoming medication resistance may be possible by recognizing and focusing on these processes. This review explores the interplay between epigenetic changes and OSCC, their role in the disease's initiation and progression, and their impact on diagnosis and treatment. It also discusses the potential of epigenetic drugs (epi-drugs) to improve diagnostic precision and treatment outcomes.

The Role of Inflammasome-Associated Innate Immune Receptors in Cancer

Dysregulated activation of the innate immune system is a critical driver of chronic inflammation that is associated with at least 30% of all cancers. Innate immunity can also exert tumour-promoting effects (e.g. proliferation) directly on cancer cells in an intrinsic manner. Conversely, innate immunity can influence adaptive immunity-based anti-tumour immune responses via Ag-presenting dendritic cells that activate natural killer and cytotoxic T cells to eradicate tumours. While adaptive anti-tumour immunity has underpinned immunotherapy approaches with immune checkpoint inhibitors and chimeric Ag receptor-T cells, the clinical utility of innate immunity in cancer is underexplored. Innate immune responses are governed by pattern recognition receptors, which comprise several families, including Toll-like, nucleotide-binding oligomerization domain-containing (NOD)-like and absent-in-melanoma 2 (AIM2)-like receptors. Notably, a subset of NOD-like and AIM2-like receptors can form large multiprotein "inflammasome" complexes which control maturation of biologically active IL-1β and IL-18 cytokines. Over the last decade, it has emerged that inflammasomes can coordinate contrasting pro- and anti-tumour responses in cancer and non-cancer (e.g. immune, stromal) cells. Considering the importance of inflammasomes to the net output of innate immune responses, here we provide an overview and discuss recent advancements on the diverse role of inflammasomes in cancer that have underpinned their potential targeting in diverse malignancies.

AIM2 promotes irradiation resistance, migration ability and PD-L1 expression through STAT1/NF-κB activation in oral squamous cell carcinoma

BACKGROUND

Radioresistance and lymph node metastasis are common phenotypes of refractory oral squamous cell carcinoma (OSCC). As a result, understanding the mechanism for radioresistance and metastatic progression is urgently needed for the precise management of refractory OSCC. Recently, immunotherapies, e.g. immune checkpoint inhibitors (ICIs), were employed to treat refractory OSCC; however, the lack of predictive biomarkers still limited their therapeutic effectiveness.

METHODS

The Cancer Genome Atlas (TCGA)/Gene Expression Omnibus (GEO) databases and RT-PCR analysis were used to determine absent in melanoma 2 (AIM2) expression in OSCC samples. Colony-forming assay and trans-well cultivation was established for estimating AIM2 function in modulating the irradiation resistance and migration ability of OSCC cells, respectively. RT-PCR, Western blot and flow-cytometric analyses were performed to examine AIM2 effects on the expression of programmed death-ligand 1 (PD-L1) expression. Luciferase-based reporter assay and site-directed mutagenesis were employed to determine the transcriptional regulatory activity of Signal Transducer and Activator of Transcription 1 (STAT1) and NF-κB towards the AIM2-triggered PD-L1 expression.

RESULTS

Here, we found that AIM2 is extensively upregulated in primary tumors compared to the normal adjacent tissues and acts as a poor prognostic marker in OSCC. AIM2 knockdown mitigated, but overexpression promoted, radioresistance, migration and PD-L1 expression via modulating the activity of STAT1/NF-κB in OSCC cell variants. AIM2 upregulation significantly predicted a favorable response in patients receiving ICI treatments.

CONCLUSIONS

Our data unveil AIM2 as a critical factor for promoting radioresistance, metastasis and PD-L1 expression and as a potential biomarker for predicting ICI effectiveness on the refractory OSCC.

Regulatory Cues in Pulmonary Fibrosis-With Emphasis on the AIM2 Inflammasome

Pulmonary fibrosis (PF) is a chronic lung disorder characterized by the presence of scarred and thickened lung tissues. Although the Food and Drug Administration approved two antifibrotic drugs, pirfenidone, and nintedanib, that are currently utilized for treating idiopathic PF (IPF), the clinical therapeutic efficacy remains unsatisfactory. It is crucial to develop new drugs or treatment schemes that combine pirfenidone or nintedanib to achieve more effective outcomes for PF patients. Understanding the complex mechanisms underlying PF could potentially facilitate drug discovery. Previous studies have found that the activation of inflammasomes, including nucleotide-binding and oligomerization domain (NOD)-like receptor protein (NLRP)1, NLRP3, NOD-like receptor C4, and absent in melanoma (AIM)2, contributes to lung inflammation and fibrosis. This article aims to summarize the cellular and molecular regulatory cues that contribute to PF with a particular emphasis on the role of AIM2 inflammasome in mediating pathophysiologic events during PF development. The insights gained from this research may pave the way for the development of more effective strategies for the prevention and treatment of PF.

Context-dependent functions of pattern recognition receptors in cancer

The immune system plays a critical role in shaping all facets of cancer, from the early initiation stage through to metastatic disease and resistance to therapy. Our understanding of the importance of the adaptive arm of the immune system in antitumour immunity has led to the implementation of immunotherapy with immune checkpoint inhibitors in numerous cancers, albeit with differing efficacy. By contrast, the clinical utility of innate immunity in cancer has not been exploited, despite dysregulated innate immunity being a feature of at least one-third of all cancers associated with tumour-promoting chronic inflammation. The past two decades have seen innate immune pattern recognition receptors (PRRs) emerge as critical regulators of the immune response to microbial infection and host tissue damage. More recently, it has become apparent that in many cancer types, PRRs play a central role in modulating a vast array of tumour-inhibiting and tumour-promoting cellular responses both in immune cells within the tumour microenvironment and directly in cancer cells. Herein, we provide a comprehensive overview of the fast-evolving field of PRRs in cancer, and discuss the potential to target PRRs for drug development and biomarker discovery in a wide range of oncology settings.

Interferon-inducible protein, IFIX, has tumor-suppressive effects in oral squamous cell carcinoma

IFIX, a newly discovered member of the interferon-inducible HIN-200 family, has been identified as a tumor suppressor in breast cancer; however, the involvement of IFIX in oral cancer are poorly understood. Here, we demonstrate a relationship between the level of IFIX expression and the invasive or migratory abilities of oral squamous cell carcinoma. Higher IFIX expression significantly correlated with clinicopathological parameters such as the histopathological grade of clinical samples. In vitro, IFIX overexpression suppressed the invasiveness of human tongue squamous cell carcinoma CAL-27 cells, and this inhibitory effect was mediated by stabilization of the cytoskeleton through various cytokeratins along with downregulation of paxillin, an intracellular adaptor protein that promotes tumor invasion. This inhibitory effect does not appear to affect the transformation of cancer stem-like cells in this cell culture model. Altogether, these data provide novel insights into the tumor-suppressive function of IFIX, namely, stabilization of the cancer cell cytoskeleton.

The complex role of AIM2 in autoimmune diseases and cancers

Absent in melanoma 2 (AIM2) is a novel member of interferon (IFN)-inducible PYHIN proteins. In innate immune cells, AIM2 servers as a cytoplasmic double-stranded DNA sensor, playing a crucial role in the initiation of the innate immune response as a component of the inflammasome. AIM2 expression is increased in patients with systemic lupus erythematosus (SLE), psoriasis, and primary Sjogren's syndrome, indicating that AIM2 might be involved in the pathogenesis of autoimmune diseases. Meanwhile, AIM2 also plays an antitumorigenesis role in an inflammasome independent-manner. In melanoma, AIM2 is initially identified as a tumor suppressor factor. However, AIM2 is also found to contribute to lung tumorigenesis via the inflammasome-dependent release of interleukin 1β and regulation of mitochondrial dynamics. Additionally, AIM2 reciprocally dampening the cGAS-STING pathway causes immunosuppression of macrophages and evasion of antitumor immunity during antibody treatment. To summarize the complicated effect and role of AIM2 in autoimmune diseases and cancers, herein, we provide an overview of the emerging research progress on the function and regulatory pathway of AIM2 in innate and adaptive immune cells, as well as tumor cells, and discuss its pathogenic role in autoimmune diseases, such as SLE, psoriasis, primary Sjogren's syndrome, and cancers, such as melanomas, non-small-cell lung cancer, colon cancer, hepatocellular carcinoma, renal carcinoma, and so on, hopefully providing potential therapeutic and diagnostic strategies for clinical use.

The regulation of long non-coding RNA 00958 (LINC00958) for oral squamous cell carcinoma (OSCC) cells death through absent in melanoma 2 (AIM2) depending on microRNA-4306 and Sirtuin1 (SIRT1) in vitro

Long non-coding RNAs (lncRNAs) have been proposed as potential targets in OSCC gene therapy. Thus, the study aims to analyze how they exert functions in OSCC. LINC00958, AIM2, Gasdermin D (GSDMD) and tumor protein p53 (TP53) expression levels are analyzed by Quantitative Real-time PCR (qPCR) or Western blotting (WB) in OSCC cells lines. The roles of LINC00958 in cell proliferation, cell death, and GSDMD expression respectively were analyzed by Cell Counting Kit-8 (CCK8) assay, flow cytometry and Immunofluorescence (IF) assay. In addition, expressions of pyroptosis- and autophagy-related proteins are evaluated by WB detection. The targeted binding of LINC00958 and miR-4306 or AIM2 mRNA is predicted by bioinformatics analysis and detected by biodual luciferase system. RIP and qPCR assays analyze whether LINC00958 interacts with SIRT1. We found that LINC00958 showed upregulation in OSCC cells compared to normal oral epithelial cells. LINC00958 silencing significantly suppressed OSCC cell proliferation, induced cell death and reduced autophagy. LINC00958 regulated the levels of miR-4306 which binds to the 3'UTR of AIM2, and interacts with and modulates SIRT1 protein expression. LINC00958 regulated GSDMD and AIM2 levels, as well as p53 and SIRT1 levels. SIRT1 overexpression markedly reversed aforementioned effects of LINC00958. LINC00958 not only downregulated miR-4306 levels to activate the pyroptosis pathway mediated by AIM2 and promoted cancer cell survival but also induced a decrease in SIRT protein expression to further reduce p53 levels.

Inflammasomes in cancer: Effect of epigenetic and autophagic modulations

Tumour-promoting inflammation is a critical hallmark in cancer development, and inflammasomes are well-known regulators of inflammatory processes within the tumour microenvironment. Different inflammasome components along with the adaptor, apoptosis-associated speck-like protein containing caspase activation and recruitment domain (ASC), and the effector, caspase-1, have a significant influence on tumorigenesis but in a tissue-specific and stage-dependent manner. The downstream products of inflammasome activation, that is the proinflammatory cytokines such as IL-1β and IL-18, regulate tissue homeostasis and induce antitumour immune responses, but in contrast, they can also favour cancer growth and proliferation by directing various oncogenic signalling pathways in cancer cells. Moreover, different epigenetic mechanisms, including DNA methylation, histone modification and noncoding RNAs, control inflammasomes and their components by regulating gene expression during cancer progression. Furthermore, autophagy, a master controller of cellular homeostasis, targets inflammasome-induced carcinogenesis by maintaining cellular homeostasis and removing potential cancer risk factors that promote inflammasome activation in support of tumorigenesis. Here, in this review, we summarize the effect of inflammasome activation in cancers and discuss the role of epigenetic and autophagic regulatory mechanisms in controlling inflammasomes. A proper understanding of the interactions among these key processes will be useful for developing novel therapeutic regimens for targeting inflammasomes in cancer.

AIM2 Inflammasome's First Decade of Discovery: Focus on Oral Diseases

A common feature of many acute and chronic oral diseases is microbial-induced inflammation. Innate immune responses are the first line of defense against pathogenic microorganisms and are initiated by pattern recognition receptors (PRRs) that specifically recognize pathogen-associated molecular patterns and danger-associated molecular patterns. The activation of certain PRRs can lead to the assembly of macromolecular oligomers termed inflammasomes, which are responsible for pro-inflammatory cytokine maturation and secretion and thus activate host inflammatory responses. About 10 years ago, the absent in melanoma 2 (AIM2) was independently discovered by four research groups, and among the “canonical” inflammasomes [including AIM2, NLR family pyrin domain (NLRP)1, NLRP3, NLR family apoptosis inhibitory protein (NAIP)/NLR family, caspase activation and recruitment domain (CARD) containing (NLRC)4, and pyrin], AIM2 so far is the only one that simultaneously acts as a cytosolic DNA sensor due to its DNA-binding ability. Undoubtedly, such a double-faceted role gives AIM2 greater mission and more potential in the mediation of innate immune responses. Therefore, AIM2 has garnered much attention from the broad scientific community during its first 10 years of discovery (2009–2019). How the AIM2 inflammasome is related to oral diseases has aroused debate over the past few years and is under active investigation. AIM2 inflammasome may potentially be a key link between oral diseases and innate immunity. In this review, we highlight the current knowledge of the AIM2 inflammasome and its critical role in the pathogenesis of various oral diseases, which might offer future possibilities for disease prevention and targeted therapy utilizing this continued understanding.