Expression and clinical significance of absent in melanoma 2 in colorectal cancer

Pan-cancer analysis of AIM2 inflammasomes with potential implications for immunotherapy in human cancer: A bulk omics research and single cell sequencing validation

Background

The absent in melanoma 2 (AIM2) inflammasome is a multi-protein platform that recognizes aberrant cytoplasmic double-stranded DNA(dsDNA) and induces cytokine maturation, release, and pyroptosis. Some studies found that the AIM2 inflammasome was a double-edged sword in many cancers. However, there have been fewer studies on AIM2 inflammasomes in pan-cancer.

Methods

Gene expression was analyzed using The Cancer Genome Atlas (TCGA) database and The Genotype-Tissue Expression (GTEx) database. Immunohistochemistry (IHC) was used to validate the expression of the AIM2. We used the survival curve to explore the prognostic significance of the AIM2 inflammasomes in pan-cancer. Mutations and methylation of AIM2 inflammasome-related genes (AIM2i-RGs) were also comprehensively analyzed. Single sample gene set enrichment analysis was used to calculate the AIM2 inflammasomes score and explore the correlation of the AIM2 inflammasomes score with immune-related genes and immune infiltrations. The function of AIM2 inflammasomes in pan-cancer was analyzed at the single-cell level. Single-cell transcriptome sequencing (scRNA-seq) data was used to assess the activation state of the AIM2 inflammasomes in the tumor microenvironment.

Results

We found that AIM2i-RGs were aberrantly expressed in tumors and were strongly associated with prognosis. In pan-cancer, the expression of AIM2i-RGs was positively associated with copy number variation and negatively associated with methylation. In AIM2i-RGs, missense mutations were the predominant type of single nucleotide polymorphism. Moreover, we found that the drugs dimethyloxallyl glycine (DMOG) and Z-LNle-CHO may be sensitive to the AIM2 inflammasomes. The AIM2 inflammasomes score was significantly and positively correlated with the tumor immunity score and the stroma score. In most tumors, the AIM2 inflammasomes score was significantly and positively correlated with CD8+ T cell abundance in the tumor microenvironment. Additionally, the AIM2 inflammasomes score was significantly correlated with immune checkpoint genes in pan-cancer as well as immune checkpoint therapy-related markers including tumor mutational burden (TMB), microsatellite instability(MSI), and tumor immune dysfunction and exclusion(TIDE). scRNA-seq analysis suggested that AIM2 inflammasomes differ significantly among different cells in the tumor microenvironment. IHC confirmed low expression of AIM2 in colorectal cancer.

Discussion

AIM2 inflammasomes may be a new target for future tumor therapy It is likely involved in tumor development, and its high expression may serve as a predictor of tumor immunotherapy efficacy.

Roles of AIM2 Gene and AIM2 Inflammasome in the Pathogenesis and Treatment of Psoriasis

Psoriasis is an immune-mediated chronic inflammatory skin disease caused by a combination of environmental incentives, polygenic genetic control, and immune regulation. The inflammation-related gene absent in melanoma 2 (AIM2) was identified as a susceptibility gene for psoriasis. AIM2 inflammasome formed from the combination of AIM2, PYD-linked apoptosis-associated speck-like protein (ASC) and Caspase-1 promotes the maturation and release of inflammatory cytokines such as IL-1β and IL-18, and triggers an inflammatory response. Studies showed the genetic and epigenetic associations between AIM2 gene and psoriasis. AIM2 gene has an essential role in the occurrence and development of psoriasis, and the inhibitors of AIM2 inflammasome will be new therapeutic targets for psoriasis. In this review, we summarized the roles of the AIM2 gene and AIM2 inflammasome in pathogenesis and treatment of psoriasis, hopefully providing a better understanding and new insight into the roles of AIM2 gene and AIM2 inflammasome in psoriasis.

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.

Absent in melanoma 2 suppresses gastric cancer cell proliferation and migration via inactivation of AKT signaling pathway

Gastric cancer (GC) is the third leading cause of cancer-related mortality worldwide, and poses a great threat to public health. Absent in melanoma 2 (AIM2), a member of the pyrin-HIN family proteins, plays various roles across different types of cancers. However, the possible role of AIM2 in GC, as well as the underling mechanisms, are equivocal and need to be further explored. Herein, we identified that AIM2 expression was significantly down-regulated in GC tissues. Furthermore, loss of AIM2 was significantly associated with tumor size, lymph node metastasis (LNM) and tumor, node, metastases (TNM) staging, as well as poor prognosis in GC patients. Knockdown of AIM2 in GC cells significantly promoted cellular proliferation and migration, whereas AIM2 overexpression did the opposite. Mechanistically, we discovered that AIM2 regulates the AKT signaling pathway. In fact, the enhanced proliferation and migration ability induced by AIM2 knockdown was partially impaired in cells treated with the AKT inhibitor. Overall, our findings suggests that AIM2 is an independent prognostic marker and highlights a new entry point for targeting the AIM2/AKT signaling axis for GC treatment.

AIM2 Inhibits BRAF-Mutant Colorectal Cancer Growth in a Caspase-1-Dependent Manner

Absent in melanoma 2 (AIM2), a DNA sensor that plays an important role in natural immunity system, has been reported to participate in colorectal cancer (CRC) development. However, the functional role of AIM2 in BRAF-mutant CRC remains unclear. In this study, we first investigated AIM2 expression level in BRAF-mutant CRC tumor tissues. Overexpression of AIM2 in CRC cells was performed to investigate the effect of AIM2 on CRC cell viability, and cell death detection and caspase activity assay were performed to explore the mechanism that AIM2 impacts the growth of BRAF-mutant CRC cells. Moreover, we confirmed the antitumor effect of AIM2 in BRAF-mutant CRC cell-derived tumor xenograft (CDX) models as well as patient-derived organoids (PDOs). Herein, we reported that AIM2 expression was lower in BRAF-mutant than that in BRAF wild-type CRC tumor tissues. Restoring the expression of AIM2 in BRAF-mutant CRC cells greatly inhibits the tumor cell growth by inducing necrotic cell death. Mechanism studies revealed that AIM2-induced cell death is in a caspase-1-dependent manner. Additionally, overexpression of AIM2 significantly inhibits tumor growth and metastasis in BRAF-mutant CRC in vivo, which was further confirmed in BRAF-mutant CRC PDOs. Taken together, our data suggested that AIM2 inhibits BRAF-mutant colon cancer growth in a caspase-1-dependent manner, which may provide evidence to understand the pathogenesis of CRC with BRAF-mutant, as well as new strategies for manipulation of CRC.

ENO1 Acts as a Prognostic Biomarker Candidate and Promotes Tumor Growth and Migration Ability Through the Regulation of Rab1A in Colorectal Cancer

Background

Colorectal carcinoma (CRC) is one of the most common malignancies with a dismal 5‐year survival rate. The glycolytic enzyme α-enolase (ENO1) is overexpressed in multiple cancers and is involved in tumor cell proliferation and metastasis. However, its clinical significance, biological role, and underlying molecular mechanisms in CRC are still unclear. The aim of the present study was to investigate the potential role of ENO1 in the initiation and development of CRC.

Patients and methods

The in situ expression of ENO1 in CRC and adjacent normal tissues was examined by immunohistochemistry. The effects of ENO1 on the in vitro proliferation and migration of CRC cell lines were investigated by MTT, colony formation, and Transwell assays. Finally, the in vivo tumorigenic capacity of ENO1 was assessed in a mouse model.

Results

ENO1 was overexpressed in CRC tissues and significantly correlated with the clinicopathological parameters. Furthermore, Rab1A was also overexpressed in CRC tissues and was positively correlated to that of ENO1. The high expression levels of both ENO1 and Rab1A led to significantly worse prognosis of CRC patients compared to either alone. Furthermore, knockdown of ENO1 significantly inhibited CRC cells proliferation and migration in vitro and reduced xenograft growth in vivo via the concomitant downregulation of Rab1A.

Conclusion

The ENO1/Rab1A signaling axis is involved in CRC progression and is a potential biomarker for the treatment of CRC.

The Multifaceted Roles of Pyroptotic Cell Death Pathways in Cancer

Cancer is a category of diseases involving abnormal cell growth with the potential to invade other parts of the body. Chemotherapy is the most widely used first-line treatment for multiple forms of cancer. Chemotherapeutic agents act via targeting the cellular apoptotic pathway. However, cancer cells usually acquire chemoresistance, leading to poor outcomes in cancer patients. For that reason, it is imperative to discover other cell death pathways for improved cancer intervention. Pyroptosis is a new form of programmed cell death that commonly occurs upon pathogen invasion. Pyroptosis is marked by cell swelling and plasma membrane rupture, which results in the release of cytosolic contents into the extracellular space. Currently, pyroptosis is proposed to be an alternative mode of cell death in cancer treatment. Accumulating evidence shows that the key components of pyroptotic cell death pathways, including inflammasomes, gasdermins and pro-inflammatory cytokines, are involved in the initiation and progression of cancer. Interfering with pyroptotic cell death pathways may represent a promising therapeutic option for cancer management. In this review, we describe the current knowledge regarding the biological significance of pyroptotic cell death pathways in cancer pathogenesis and also discuss their potential therapeutic utility.

Absent in melanoma 2 suppresses epithelial-mesenchymal transition via Akt and inflammasome pathways in human colorectal cancer cells

Absent in melanoma 2 (AIM2) is a critical component in natural immunity system and is closely related to cancer initiation and development. It has been shown that AIM2 inhibited colorectal cancer (CRC) development and cell proliferation. It remains unresolved how AIM2 acts on CRC metastasis. In this study, we assessed migration, invasion ability, and epithelial-mesenchymal transition (EMT) program upon AIM2 overexpression or knockdown in human CRC cells. Transwell assay demonstrated that upregulation of AIM2 reduced cell migration and invasion. Epithelial marker E-cadherin was augmented and mesenchymal markers vimentin, as well as Snail, were examined decreased by Western blot, real-time polymerase chain reaction, and immunofluorescence. Correspondingly, knockdown of AIM2 led to a reverse consequence. In addition, AIM2 regulated Akt phosphorylation and effects of AIM2 on cell invasion and EMT were recovered after administration of Akt inhibitor, suggesting that AIM2 suppressed EMT dependent on Akt pathway. In addition, caspase-1 inhibitor exposure indicated that AIM2 abrogated EMT through the inflammasome pathway as well. In summary, AIM2 suppressed EMT via Akt and inflammasome pathways in human CRC cells.

Rab1A promotes proliferation and migration abilities via regulation of the HER2/AKT-independent mTOR/S6K1 pathway in colorectal cancer

Colorectal carcinoma (CRC) is one of the most common malignancies worldwide and the second leading cause of cancer-related deaths in the US. Recently, Rab1A has been reported to be an activator of mTORC1 and p-S6K1, which is downstream of mTORC1. However, the association between Rab1A and p-S6K1 in CRC remains elusive. In the present study, we first demonstrated that Rab1A was overexpressed in CRC tissues and Rab1A overexpression was positively related to lymph node invasion, degree of differentiation, venous invasion and tumor-node-metastasis (TNM) stage. In both TNM stage I–II and III–IV patients, Rab1A-positive patients had a shorter survival time than Rab1A-negative patients. Furthermore, in univariate and multivariate analyses, only Rab1A expression was verified as an independent prognostic factor for survival in CRC patients. The level of p-S6K1 was markedly high in CRC tissues and Rab1A expression level had a positive association with p-S6K1 level. In addition, high levels of both Rab1A and p-S6K1 were associated with a poorer prognosis compared with low expression of either Rab1A or p-S6K1 level. Moreover, high levels of both Rab1A and p-S6K1 were associated with a poorer prognosis than patients with high levels of either Rab1A or p-S6K1 alone. Finally, knockdown of Rab1A expression inhibited migration and proliferation of SW480 and HCT116 cell lines by targeting regulation of p-S6K1. Thus, our findings indicate that Rab1A plays an important role in CRC and may provide a therapeutic target for CRC, particularly for mTORC1-targeted therapy-resistant cancers.

Cytosolic DNA Sensing in Organismal Tumor Control

Besides constituting a first layer of defense against microbial challenges, the detection of cytosolic DNA is fundamental for mammalian organisms to control malignant transformation and tumor progression. The accumulation of DNA in the cytoplasm can initiate the proliferative inactivation (via cellular senescence) or elimination (via regulated cell death) of neoplastic cell precursors. Moreover, cytosolic DNA sensing is intimately connected to the secretion of cytokines that support innate and adaptive antitumor immunity. Here, we discuss the molecular mechanisms whereby cytosolic DNA enables cell-intrinsic and -extrinsic oncosuppression, and their relevance for the development of novel therapeutic approaches that reinstate anticancer immunosurveillance.

Yes-associated protein enhances proliferation and attenuates sensitivity to cisplatin in human gastric cancer cells

BACKGROUND

Yes-associated protein (YAP) is upregulated in many cancer types, and its overexpression is involved in tumor cell proliferation, metastasis and resistance to chemotherapy. In the present study, we aimed to investigate the potential role of YAP in the development and progression of gastric cancer.

METHODS

YAP levels were analyzed in human gastric cancer and adjacent normal tissues by Western blotting and immunohistochemistry. Potential roles of YAP in regulating gastric cancer cell proliferation and sensitivity to cisplatin were examined by genetic manipulation in vitro. The molecular signaling was determined to understand the mechanisms of observed YAP effects.

RESULTS

YAP level was higher in gastric cancer tissues as compared to paired normal tissues. Knockdown of YAP attenuated gastric cancer cell proliferation and enhanced sensitivity to cisplatin in vitro while YAP overexpression possessed the opposite effects. YAP regulated Epidermal growth factor receptor (EGFR) expression and its downstream AKT and extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway in gastric cancer cells.

CONCLUSION

YAP enhances gastric cancer cell proliferation and attenuates sensitivity to cisplatin potentially through targeting the EGFR signaling, indicating that YAP/EGFR signaling axis may serve as a potential target for treatment of gastric cancer.