Hepatic RIG-I predicts survival and interferon-α therapeutic response in hepatocellular carcinoma

Astroglial membrane camouflaged Ptbp1 siRNA delivery hinders glutamate homeostasis via SDH/Nrf2 pathway

Polypyrimidine tract-binding protein 1 (PTBP1) regulates numerous alternative splicing events during tumor progression and neurogenesis. Previously, PTBP1 downregulation was reported to convert astrocytes into functional neurons; however, how PTBP1 regulates astrocytic physiology remains unclear. In this study, we revealed that PTBP1 modulated glutamate uptake via ATP1a2, a member of Na+/K+-ATPases, and glutamate transporters in astrocytes. Ptbp1 knockdown altered mitochondrial function and energy metabolism, which involved PTBP1 regulating mitochondrial redox homeostasis via the succinate dehydrogenase (SDH)/Nrf2 pathway. The malfunction of glutamate transporters following Ptbp1 knockdown resulted in enhanced excitatory synaptic transmission in the cortex. Notably, we developed a biomimetic cationic triblock polypeptide system, i.e., polyethylene glycol44-polylysine30-polyleucine10 (PEG44-PLL30-PLLeu10) with astrocytic membrane coating to deliver Ptbp1 siRNA in vitro and in vivo, which approach allowed Ptbp1 siRNA to efficiently cross the blood-brain barrier and target astrocytes in the brain. Collectively, our findings suggest a framework whereby PTBP1 serves as a modulator in glutamate transport machinery, and indicate that biomimetic methodology is a promising route for in vivo siRNA delivery.

UBXN9 inhibits the RNA exosome function to promote T cell control of liver tumorigenesis

BACKGROUND AND AIMS

Liver tumorigenesis encompasses oncogenic activation and self-adaptation of various biological processes in premalignant hepatocytes to circumvent the pressure of cellular stress and host immune control. Ubiquitin regulatory X domain-containing proteins (UBXNs) participate in the regulation of certain signaling pathways. However, whether UBXN proteins function in the development of liver cancer remains unclear.

APPROACH AND RESULTS

Here, we demonstrated that UBXN9 (Alveolar Soft Part Sarcoma Chromosomal Region Candidate Gene 1 Protein/Alveolar Soft Part Sarcoma Locus) expression was decreased in autochthonous oncogene-induced mouse liver tumors and ~47.7% of human HCCs, and associated with poor prognosis in patients with HCC. UBXN9 attenuated liver tumorigenesis induced by different oncogenic factors and tumor growth of transplanted liver tumor cells in immuno-competent mice. Mechanistically, UBXN9 significantly inhibited the function of the RNA exosome, resulting in increased expression of RLR-stimulatory RNAs and activation of the retinoic acid-inducible gene-I-IFN-Ι signaling in tumor cells, and hence potentiated T cell recruitment and immune control of tumor growth. Abrogation of the CD8 + T cell response or inhibition of tumor cell retinoic acid-inducible gene-I signaling efficiently counteracted the UBXN9-mediated suppression of liver tumor growth.

CONCLUSIONS

Our results reveal a modality in which UBXN9 promotes the stimulatory RNA-induced retinoic acid-inducible gene-I-interferon signaling that induces anti-tumor T cell response in liver tumorigenesis. Targeted manipulation of the UBXN9-RNA exosome circuit may have the potential to reinstate the immune control of liver tumor growth.

Homosalate and ERK Knockdown in the Modulation of Aurelia coerulea Metamorphosis by Regulating the PI3K Pathway and ERK Pathway

Metamorphosis control is pivotal in preventing the outbreak of jellyfish, and it is often studied using common model organisms. The widespread use of the ultraviolet blocking agent homosalate in cosmetics poses a threat to marine ecosystems. Although the impact of homosalate on marine organisms has been extensively examined, there is a notable absence of research on its effects on jellyfish metamorphosis and the underlying mechanisms, warranting further investigation. In this study, we first established a study model by using 5-methoxy-2-methylindole to induce Aurelia coerulea metamorphosis, and selected homosalate as a PI3K agonist and an ERK agonist, while we used YS-49 as a specific PI3K agonist, as well as ERK knockdown, to observe their effect on the metamorphosis of Aurelia coerulea. The results showed that an Aurelia coerulea metamorphosis model was established successfully, and the PI3K agonist homosalate, YS-49, and the knockdown of ERK molecules could significantly delay the metamorphosis development of Aurelia coerulea. We propose that activating PI3K/Akt and inhibiting the ERK pathway are involved in the delayed development of Aurelia coerulea, which provides a new strategy for the prevention and control of jellyfish blooms.

Emerging roles of liquid-liquid phase separation in liver innate immunity

Biomolecular condensates formed by liquid-liquid phase separation (LLPS) have become an extensive mechanism of macromolecular metabolism and biochemical reactions in cells. Large molecules like proteins and nucleic acids will spontaneously aggregate and assemble into droplet-like structures driven by LLPS when the physical and chemical properties of cells are altered. LLPS provides a mature molecular platform for innate immune response, which tightly regulates key signaling in liver immune response spatially and physically, including DNA and RNA sensing pathways, inflammasome activation, and autophagy. Take this, LLPS plays a promoting or protecting role in a range of liver diseases, such as viral hepatitis, non-alcoholic fatty liver disease, liver fibrosis, hepatic ischemia-reperfusion injury, autoimmune liver disease, and liver cancer. This review systematically describes the whole landscape of LLPS in liver innate immunity. It will help us to guide a better-personalized approach to LLPS-targeted immunotherapy for liver diseases.

RNA m5C methylation: a potential modulator of innate immune pathways in hepatocellular carcinoma

RNA 5-methylcytosine (m5C) methylation plays a crucial role in hepatocellular carcinoma (HCC). As reported, aberrant m5C methylation is closely associated with the progression, therapeutic efficacy, and prognosis of HCC. The innate immune system functions as the primary defense mechanism in the body against pathogenic infections and tumors since it can activate innate immune pathways through pattern recognition receptors to exert anti-infection and anti-tumor effects. Recently, m5C methylation has been demonstrated to affect the activation of innate immune pathways including TLR, cGAS-STING, and RIG-I pathways by modulating RNA function, unveiling new mechanisms underlying the regulation of innate immune responses by tumor cells. However, research on m5C methylation and its interplay with innate immune pathways is still in its infancy. Therefore, this review details the biological significance of RNA m5C methylation in HCC and discusses its potential regulatory relationship with TLR, cGAS-STING, and RIG-I pathways, thereby providing fresh insights into the role of RNA methylation in the innate immune mechanisms and treatment of HCC.

Interferon-α stimulates DExH-box helicase 58 to prevent hepatocyte ferroptosis

BACKGROUND

Liver ischemia/reperfusion (I/R) injury is usually caused by hepatic inflow occlusion during liver surgery, and is frequently observed during war wounds and trauma. Hepatocyte ferroptosis plays a critical role in liver I/R injury, however, it remains unclear whether this process is controlled or regulated by members of the DEAD/DExH-box helicase (DDX/DHX) family.

METHODS

The expression of DDX/DHX family members during liver I/R injury was screened using transcriptome analysis. Hepatocyte-specific Dhx58 knockout mice were constructed, and a partial liver I/R operation was performed. Single-cell RNA sequencing (scRNA-seq) in the liver post I/R suggested enhanced ferroptosis by Dhx58hep-/-. The mRNAs and proteins associated with DExH-box helicase 58 (DHX58) were screened using RNA immunoprecipitation-sequencing (RIP-seq) and IP-mass spectrometry (IP-MS).

RESULTS

Excessive production of reactive oxygen species (ROS) decreased the expression of the IFN-stimulated gene Dhx58 in hepatocytes and promoted hepatic ferroptosis, while treatment using IFN-α increased DHX58 expression and prevented ferroptosis during liver I/R injury. Mechanistically, DHX58 with RNA-binding activity constitutively associates with the mRNA of glutathione peroxidase 4 (GPX4), a central ferroptosis suppressor, and recruits the m6A reader YT521-B homology domain containing 2 (YTHDC2) to promote the translation of Gpx4 mRNA in an m6A-dependent manner, thus enhancing GPX4 protein levels and preventing hepatic ferroptosis.

CONCLUSIONS

This study provides mechanistic evidence that IFN-α stimulates DHX58 to promote the translation of m6A-modified Gpx4 mRNA, suggesting the potential clinical application of IFN-α in the prevention of hepatic ferroptosis during liver I/R injury.

Harnessing innate immune pathways for therapeutic advancement in cancer

The innate immune pathway is receiving increasing attention in cancer therapy. This pathway is ubiquitous across various cell types, not only in innate immune cells but also in adaptive immune cells, tumor cells, and stromal cells. Agonists targeting the innate immune pathway have shown profound changes in the tumor microenvironment (TME) and improved tumor prognosis in preclinical studies. However, to date, the clinical success of drugs targeting the innate immune pathway remains limited. Interestingly, recent studies have shown that activation of the innate immune pathway can paradoxically promote tumor progression. The uncertainty surrounding the therapeutic effectiveness of targeted drugs for the innate immune pathway is a critical issue that needs immediate investigation. In this review, we observe that the role of the innate immune pathway demonstrates heterogeneity, linked to the tumor development stage, pathway status, and specific cell types. We propose that within the TME, the innate immune pathway exhibits multidimensional diversity. This diversity is fundamentally rooted in cellular heterogeneity and is manifested as a variety of signaling networks. The pro-tumor effect of innate immune pathway activation essentially reflects the suppression of classical pathways and the activation of potential pro-tumor alternative pathways. Refining our understanding of the tumor's innate immune pathway network and employing appropriate targeting strategies can enhance our ability to harness the anti-tumor potential of the innate immune pathway and ultimately bridge the gap from preclinical to clinical application.

A tumor suppressor protein encoded by circKEAP1 inhibits osteosarcoma cell stemness and metastasis by promoting vimentin proteasome degradation and activating anti-tumor immunity

BACKGROUND

Osteosarcoma (OS) is one of most commonly diagnosed bone cancer. Circular RNAs (circRNAs) are a class of highly stable non-coding RNA, the majority of which have not been characterized functionally. The underlying function and molecular mechanisms of circRNAs in OS have not been fully demonstrated.

METHOD

Microarray analysis was performed to identify circRNAs that are differentially-expressed between OS and corresponding normal tissues. The biological function of circKEAP1 was confirmed in vitro and in vivo. Mass spectrometry and western blot assays were used to identify the circKEAP1-encoded protein KEAP1-259aa. The molecular mechanism of circKEAP1 was investigated by RNA sequencing and RNA immunoprecipitation analyses.

RESULTS

Here, we identified a tumor suppressor circKEAP1, originating from the back-splicing of exon2 of the KEAP1 gene. Clinically, circKEAP1 is downregulated in OS tumors and associated with better survival in cancer patients. N6-methyladenosine (m6A) at a specific adenosine leads to low expression of circKEAP1. Further analysis revealed that circKEAP1 contained a 777 nt long ORF and encoded a truncated protein KEAP1-259aa that reduces cell proliferation, invasion and tumorsphere formation of OS cells. Mechanistically, KEAP1-259aa bound to vimentin in the cytoplasm to promote vimentin proteasome degradation by interacting with the E3 ligase ARIH1. Moreover, circKEAP1 interacted with RIG-I to activate anti-tumor immunity via the IFN-γ pathway.

CONCLUSION

Taken together, our findings characterize a tumor suppressor circKEAP1 as a key tumor suppressor regulating of OS cell stemness, proliferation and migration, providing potential therapeutic targets for treatment of OS.

Integrating innate and adaptive immunity in oncolytic virus therapy

Oncolytic viruses (OVs), viruses engineered to lyse tumor cells, work hand in hand with the immune response. While for decades the field isolated lytic capability and viral spread to increase response to virotherapy, there is now a wealth of research that demonstrates the importance of immunity in the OV mechanism of action. In this review, we will cover how OVs interact with the innate immune system to fully activate the adaptive immune system and yield exceptional tumor clearances as well as look forward at combination therapies which can improve clinical responses.

Harnessing the innate immune system by revolutionizing macrophage-mediated cancer immunotherapy

Immunotherapy is a promising and safer alternative to conventional cancer therapies. It involves adaptive T-cell therapy, cancer vaccines, monoclonal antibodies, immune checkpoint blockade (ICB), and chimeric antigen receptor (CAR) based therapies. However, most of these modalities encounter restrictions in solid tumours owing to a dense, highly hypoxic and immune-suppressive microenvironment as well as the heterogeneity of tumour antigens. The elevated intra-tumoural pressure and mutational rates within fastgrowing solid tumours present challenges in efficient drug targeting and delivery. The tumour microenvironment is a dynamic niche infiltrated by a variety of immune cells, most of which are macrophages. Since they form a part of the innate immune system, targeting macrophages has become a plausible immunotherapeutic approach. In this review, we discuss several versatile approaches (both at pre-clinical and clinical stages) such as the direct killing of tumour-associated macrophages, reprogramming pro-tumour macrophages to anti-tumour phenotypes, inhibition of macrophage recruitment into the tumour microenvironment, novel CAR macrophages, and genetically engineered macrophages that have been devised thus far. These strategies comprise a strong and adaptable macrophage-toolkit in the ongoing fight against cancer and by understanding their significance, we may unlock the full potential of these immune cells in cancer therapy.

UBE2O reduces the effectiveness of interferon-α via degradation of IFIT3 in hepatocellular carcinoma

Interferon (IFN) exerts its effects through interferon-stimulated genes (ISGs), but its efficacy is limited by interferon resistance, which can be caused by the ubiquitination of key proteins. UBE2O was initially identified as a promising therapeutic target based on data from the TCGA and iUUCD 2.0 databases. Through the inhibition of UBE2O, interferon α/β signaling and overall interferon signaling were activated. Integrating data from proteomic, mass spectrometry, and survival analyses led to the identification of IFIT3, a mediator of interferon signaling, as a ubiquitination substrate of UBE2O. The results of in vitro and in vivo experiments demonstrated that the knockdown of UBE2O can enhance the efficacy of interferon-α by upregulating IFIT3 expression. K236 was identified as a ubiquitination site in IFIT3, and the results of rescue experiments confirmed that the effect of UBE2O on interferon-α sensitivity is dependent on IFIT3 activity. ATO treatment inhibited UBE2O and increased IFIT3 expression, thereby increasing the effectiveness of interferon-α. In conclusion, these findings suggest that UBE2O worsens the therapeutic effect of interferon-α by targeting IFIT3 for ubiquitination and degradation.

PTIR1 acts as an isoform of DDX58 and promotes tumor immune resistance through activation of UCHL5

Cancer evades host immune surveillance by virtue of poor immunogenicity. Here, we report an immune suppressor, designated as PTIR1, that acts as a promotor of tumor immune resistance. PTIR1 is selectively induced in human cancers via alternative splicing of DDX58 (RIG-I), and its induction is closely related to poor outcome in patients with cancer. Through blocking the recruitment of leukocytes, PTIR1 facilitates cancer immune escape and tumor-intrinsic resistance to immunotherapeutic treatments. Unlike RIG-I, PTIR1 is capable of binding to the C terminus of UCHL5 and activates its ubiquitinating function, which in turn inhibits immunoproteasome activity and limits neoantigen processing and presentation, consequently blocking T cell recognition and attack against cancer. Moreover, we find that the adenosine deaminase ADAR1 induces A-to-I RNA editing on DDX58 transcript, thus triggering PTIR1 production. Collectively, our data uncover the immunosuppressive role of PTIR1 in tumorigenesis and propose that ADAR1-PTIR1-UCHL5 signaling is a potential cancer immunotherapeutic target.

MFSD2A potentiates gastric cancer response to anti-PD-1 immunotherapy by reprogramming the tumor microenvironment to activate T cell response

BACKGROUND

The efficacy of anti-programmed cell death protein 1 (PD-1) immunotherapy in various cancers, including gastric cancer (GC), needs to be potentiated by more effective targeting to enhance therapeutic efficacy or identifying accurate biomarkers to predict clinical responses. Here, we attempted to identify molecules predicting or/and promoting anti-PD-1 therapeutic response in advanced GC (AGC).

METHODS

The transcriptome of AGC tissues from patients with different clinical responses to anti-PD-1 immunotherapy and GC cells was analyzed by RNA sequencing. The protein and mRNA levels of the major facilitator superfamily domain containing 2A (MFSD2A) in GC cells were assessed via quantitative real-time polymerase chain reaction, Western blotting, and immunohistochemistry. Additionally, the regulation of anti-PD-1 response by MFSD2A was studied in tumor-bearing mice. Cytometry by Time-of-Flight, multiple immunohistochemistry, and flow cytometry assays were used to explore immunological responses. The effects of MFSD2A on lipid metabolism in mice cancer tissue and GC cells was detected by metabolomics.

RESULTS

Higher expression of MFSD2A in tumor tissues of AGC patients was associated with better response to anti-PD-1 immunotherapy. Moreover, MFSD2A expression was lower in GC tissues compared to adjacent normal tissues, and its expression was inversely correlated with GC stage. The overexpression of MFSD2A in GC cells enhanced the efficacy of anti-PD-1 immunotherapy in vivo by reprogramming the tumor microenvironment (TME), characterized by increased CD8+ T cell activation and reduced its exhaustion. MFSD2A inhibited transforming growth factor β1 (TGFβ1) release from GC cells by suppressing cyclooxygenase 2 (COX2)-prostaglandin synthesis, which consequently reprogrammed TME to promote anti-tumor T cell activation.

CONCLUSIONS

MFSD2A potentially serves as a predictive biomarker for anti-PD-1 immunotherapy response in AGC patients. MFSD2A may be a promising therapeutic target to potentiate the efficacy of anti-PD-1 immunotherapy by reprogramming the TME to promote T cells activation.

Immune landscape and immunotherapy of hepatocellular carcinoma: focus on innate and adaptive immune cells

Hepatocellular carcinoma (HCC) is responsible for roughly 90% of all cases of primary liver cancer, and the cases are on the rise. The treatment of advanced HCC is a serious challenge. Immune checkpoint inhibitor (ICI) therapy has marked a watershed moment in the history of HCC systemic treatment. Atezolizumab in combination with bevacizumab has been approved as a first-line treatment for advanced HCC since 2020; however, the combination therapy is only effective in a limited percentage of patients. Considering that the tumor immune microenvironment (TIME) has a great impact on immunotherapies for HCC, an in-depth understanding of the immune landscape in tumors and the current immunotherapeutic approaches is extremely necessary. We elaborate on the features, functions, and cross talk of the innate and adaptive immune cells in HCC and highlight the benefits and drawbacks of various immunotherapies for advanced HCC, as well as future projections. HCC consists of a heterogeneous group of cancers with distinct etiologies and immune microenvironments. Almost all the components of innate and adaptive immune cells in HCC have altered, showing a decreasing trend in the number of tumor suppressor cells and an increasing trend in the pro-cancer cells, and there is also cross talk between various cell types. Various immunotherapies for HCC have also shown promising efficacy and application prospect. There are multilayered interwoven webs among various immune cell types in HCC, and emerging evidence demonstrates the promising prospect of immunotherapeutic approaches for HCC.

Mitochondrial IRG1 traps MCL-1 to induce hepatocyte apoptosis and promote carcinogenesis

Hepatocarcinogenesis is initiated by repeated hepatocyte death and liver damage, and the underlying mechanisms mediating cell death and the subsequent carcinogenesis remain to be fully investigated. Immunoresponsive gene 1 (IRG1) and its enzymatic metabolite itaconate are known to suppress inflammation in myeloid cells, and its expression in liver parenchymal hepatocytes is currently determined. However, the potential roles of IRG1 in hepatocarcinogenesis are still unknown. Here, using the diethylnitrosamine (DEN)-induced hepatocarcinogenesis mouse model, we found that IRG1 expression in hepatocytes was markedly induced upon DEN administration. The DEN-induced IRG1 was then determined to promote the intrinsic mitochondrial apoptosis of hepatocytes and liver damage, thus enhancing the subsequent hepatocarcinogenesis. Mechanistically, the mitochondrial IRG1 could associate and trap anti-apoptotic MCL-1 to inhibit the interaction between MCL-1 and pro-apoptotic Bim, thus promoting Bim activation and downstream Bax mitochondrial translocation, and then releasing cytochrome c and initiating apoptosis. Thus, the inducible mitochondrial IRG1 promotes hepatocyte apoptosis and the following hepatocarcinogenesis, which provides mechanistic insight and a potential target for preventing liver injury and HCC.

Innate immune response restarts adaptive immune response in tumors

The imbalance of immune response plays a crucial role in the development of diseases, including glioblastoma. It is essential to comprehend how the innate immune system detects tumors and pathogens. Endosomal and cytoplasmic sensors can identify diverse cancer cell antigens, triggering the production of type I interferon and pro-inflammatory cytokines. This, in turn, stimulates interferon stimulating genes, enhancing the presentation of cancer antigens, and promoting T cell recognition and destruction of cancer cells. While RNA and DNA sensing of tumors and pathogens typically involve different receptors and adapters, their interaction can activate adaptive immune response mechanisms. This review highlights the similarity in RNA and DNA sensing mechanisms in the innate immunity of both tumors and pathogens. The aim is to enhance the anti-tumor innate immune response, identify regions of the tumor that are not responsive to treatment, and explore new targets to improve the response to conventional tumor therapy and immunotherapy.

MicroRNAs in the Regulation of RIG-I-like Receptor Signaling Pathway: Possible Strategy for Viral Infection and Cancer

The retinoic acid-inducible gene I (RIG-I)-like receptors (RLRs) play a crucial role as pattern-recognition receptors within the innate immune system. These receptors, present in various cell and tissue types, serve as essential sensors for viral infections, enhancing the immune system's capacity to combat infections through the induction of type I interferons (IFN-I) and inflammatory cytokines. RLRs are involved in a variety of physiological and pathological processes, including viral infections, autoimmune disorders, and cancer. An increasing body of research has examined the possibility of RLRs or microRNAs as therapeutic targets for antiviral infections and malignancies, despite the fact that few studies have focused on the regulatory function of microRNAs on RLR signaling. Consequently, our main emphasis in this review is on elucidating the role of microRNAs in modulating the signaling pathways of RLRs in the context of cancer and viral infections. The aim is to establish a robust knowledge base that can serve as a basis for future comprehensive investigations into the interplay between microRNAs and RIG-I, while also facilitating the advancement of therapeutic drug development.

RIG-I promotes immune evasion of colon cancer by modulating PD-L1 ubiquitination

Colon cancer is one of the most prevalent cancers and exhibits high mortality worldwide. Despite the certain success in the immunotherapy of many tumor types, the limited response of colon cancer to immunotherapy remains a difficult problem. Retinoic acid-inducible gene-I (RIG-I) is a crucial component in innate antiviral immunity, but its role in antitumor immunity remains unclear. Here, in this report, we found that silencing RIG-I decreased resistance to tumor cells killed by T cells and attenuated colon tumor growth in immunocompetent mice. Meanwhile, overexpressing RIG-I promoted tumor progression, and high expression of RIG-I sensitized cells to anti-programmed cell death protein-1 (PD-1) therapy in vivo. Interestingly, we found that RIG-I influenced programmed cell death ligand 1 (PD-L1) expression to promote colon cancer immune evasion without relying on type I interferon stimulation. Mechanistically, RIG-I could compete with Speckle Type POZ protein (SPOP) to bind PD-L1, leading to attenuation of the polyubiquitination and proteasomal degradation of PD-L1. Collectively, our work reveals new insights into the contribution of RIG-I to driving immune evasion by maintaining the stability of PD-L1 through post-translational modification and provides a promising biomarker of the efficacy of immunotherapy in colon cancer.

RIG-I promotes cell proliferation in esophageal squamous cell carcinoma by facilitating p21 degradation

Retinoic acid-inducible gene-I (RIG-I) is considered a key sensor for host recognition of RNA virus infections. Recent studies have shown that RIG-I also regulates carcinogenesis. However, the role of RIG-I in esophageal squamous cell carcinoma (ESCC) remains unclear. We investigated the RIG-I expression in ESCC cells using a public database, immunohistochemistry, and Western blotting. We evaluated the proliferative activity of ESCC cells using CCK-8, colony formation, and EdU staining assays. Further, we determined the ESCC cell-cycle changes using flow cytometry and the ubiquitination of p21 in the cells using cycloheximide chase and ubiquitination assays. Finally, we verified the in vivo effects of RIG-I on ESCC cells by constructing xenograft models. RIG-I was highly expressed in ESCC cells and significantly promoted their proliferation and cell-cycle. Moreover, RIG-I knockdown inhibited xenograft growth in nude mice. Furthermore, RIG-I accelerated the cell-cycle by promoting the ubiquitination and degradation of p21. Overall, this study revealed that the increased expression of RIG-I due to ESCC accelerated the progression of esophageal cancer by promoting the ubiquitination and degradation of p21, which is related to the prognosis of ESCC. Thus, RIG-I may be a novel therapeutic target for ESCC treatment.

Exploiting RIG-I-like receptor pathway for cancer immunotherapy

RIG-I-like receptors (RLRs) are intracellular pattern recognition receptors that detect viral or bacterial infection and induce host innate immune responses. The RLRs family comprises retinoic acid-inducible gene 1 (RIG-I), melanoma differentiation-associated gene 5 (MDA5) and laboratory of genetics and physiology 2 (LGP2) that have distinctive features. These receptors not only recognize RNA intermediates from viruses and bacteria, but also interact with endogenous RNA such as the mislocalized mitochondrial RNA, the aberrantly reactivated repetitive or transposable elements in the human genome. Evasion of RLRs-mediated immune response may lead to sustained infection, defective host immunity and carcinogenesis. Therapeutic targeting RLRs may not only provoke anti-infection effects, but also induce anticancer immunity or sensitize "immune-cold" tumors to immune checkpoint blockade. In this review, we summarize the current knowledge of RLRs signaling and discuss the rationale for therapeutic targeting RLRs in cancer. We describe how RLRs can be activated by synthetic RNA, oncolytic viruses, viral mimicry and radio-chemotherapy, and how the RNA agonists of RLRs can be systemically delivered in vivo. The integration of RLRs agonism with RNA interference or CAR-T cells provides new dimensions that complement cancer immunotherapy. Moreover, we update the progress of recent clinical trials for cancer therapy involving RLRs activation and immune modulation. Further studies of the mechanisms underlying RLRs signaling will shed new light on the development of cancer therapeutics. Manipulation of RLRs signaling represents an opportunity for clinically relevant cancer therapy. Addressing the challenges in this field will help develop future generations of cancer immunotherapy.

Hepatic interferon regulatory factor 8 expression suppresses hepatocellular carcinoma progression and enhances the response to anti-programmed cell death protein-1 therapy

BACKGROUND AND AIMS

Therapeutic blockade of the programmed cell death protein-1 (PD-1) immune checkpoint pathways has resulted in significant reactivation of T cell-mediated antitumor immunity and is a promising clinical anticancer treatment modality in several tumor types, but the durable response rate remains relatively low (15%-20%) in most patients with HCC for unknown reasons. Evidence reveals that the interferon signaling pathway plays a critical role in modulating the efficacy and sensitivity of anti-PD-1 therapy against multiple tumor types, but the mechanisms are unclear.

APPROACH AND RESULTS

Using Kaplan-Meier survival analysis based on HCC databases, we found that deceased expression of interferon regulatory factor (IRF) 8 in HCC, among all the nine IRF members that regulate interferon signals, was associated with poor prognosis of patients with HCC. Moreover, gene set enrichment analysis identified the interferon-gamma and PD-1 signaling signatures as the top suppressed pathways in patients with IRF8-low HCC. Contrarily, overexpression of IRF8 in HCC cells significantly enhanced antitumor effects in immune-competent mice, modulating infiltration of tumor-associated macrophages (TAMs) and T cell exhaustion in tumor microenvironment. We further demonstrated that IRF8 regulated recruitment of TAMs by inhibiting the expression of chemokine (C-C motif) ligand 20 (CCL20). Mechanically, IRF8-mediated repression of c-fos transcription resulted in decreased expression of CCL20, rather than directly bound to CCL20 promoter region. Importantly, adeno-associated virus 8-mediated hepatic IRF8 rescue significantly suppressed HCC progression and enhanced the response to anti-PD-1 therapy.

CONCLUSIONS

This work identified IRF8 as an important prognostic biomarker in patients with HCC that predicted the response and sensitivity to anti-PD-1 therapy and uncovered it as a therapeutic target for enhancing the efficacy of immune therapy.

Mutant RIG-I enhances cancer-related inflammation through activation of circRIG-I signaling

RIG-I/DDX58 plays a key role in host innate immunity. However, its therapeutic potential for inflammation-related cancers remains to be explored. Here we identify frameshift germline mutations of RIG-I occurring in patients with colon cancer. Accordingly, Rig-i^fs/fs mice bearing a frameshift mutant Rig-i exhibit increased susceptibility to colitis-related colon cancer as well as enhanced inflammatory response to chemical, virus or bacteria. In addition to interruption of Rig-i mRNA translation, the Rig-i mutation changes the secondary structure of Rig-i pre-mRNA and impairs its association with DHX9, consequently inducing a circular RNA generation from Rig-i transcript, thereby, designated as circRIG-I. CircRIG-I is frequently upregulated in colon cancers and its upregulation predicts poor outcome of colon cancer. Mechanistically, circRIG-I interacts with DDX3X, which in turn stimulates MAVS/TRAF5/TBK1 signaling cascade, eventually activating IRF3-mediated type I IFN transcription and aggravating inflammatory damage. Reciprocally, all-trans retinoic acid acts as a DHX9 agonist, ameliorates immunopathology through suppression of circRIG-I biogenesis. Collectively, our results provide insight into mutant RIG-I action and propose a potential strategy for the treatment of colon cancer.

The lncRNAs involved in regulating the RIG-I signaling pathway

Understanding the targets and interactions of long non-coding RNAs (lncRNAs) related to the retinoic acid-inducible gene-I (RIG-I) signaling pathway is essential for developing interventions, which would enable directing the host inflammatory response regulation toward protective immunity. In the RIG-I signaling pathway, lncRNAs are involved in the important processes of ubiquitination, phosphorylation, and glycolysis, thus promoting the transport of the interferon regulatory factors 3 and 7 (IRF3 and IRF7) and the nuclear factor kappa B (NF-κB) into the nucleus, and activating recruitment of type I interferons (IFN-I) and inflammatory factors to the antiviral action site. In addition, the RIG-I signaling pathway has recently been reported to contain the targets of coronavirus disease-19 (COVID-19)-related lncRNAs. The molecules in the RIG-I signaling pathway are directly regulated by the lncRNA-microRNAs (miRNAs)-messenger RNA (mRNA) axis. Therefore, targeting this axis has become a novel strategy for the diagnosis and treatment of cancer. In this paper, the studies on the regulation of the RIG-I signaling pathway by lncRNAs during viral infections and cancer are comprehensively analyzed. The aim is to provide a solid foundation of information for conducting further detailed studies on lncRNAs and RIG-I in the future and also contribute to clinical drug development.

JMJD4-demethylated RIG-I prevents hepatic steatosis and carcinogenesis

Background

Hepatocarcinogenesis is driven by necroinflammation or metabolic disorders, and the underlying mechanisms remain largely elusive. We previously found that retinoic acid-inducible gene-I (RIG-I), a sensor for recognizing RNA virus in innate immune cells, is mainly expressed by parenchymal hepatocytes in the liver. However, its roles in hepatocarcinogenesis are unknown, which is intensively investigated in this study.

Methods

DEN-induced necroinflammation-driven hepatocarcinogenesis and STAM NASH-hepatocarcinogenesis were carried out in hepatocyte-specific RIG-I knockout mice. The post-translational modification of RIG-I was determined by mass spectrometry, and specific antibodies against methylated lysine sites and the RIG-I lysine mutant mice were constructed to identify the functions of RIG-I methylation.

Results

We interestingly found that DEN-induced hepatocarcinogenesis was enhanced, while NASH-induced hepatocarcinogenesis was suppressed by hepatocyte-specific RIG-I deficiency. Further, IL-6 decreased RIG-I expression in HCC progenitor cells (HcPCs), which then viciously promoted IL-6 effector signaling and drove HcPCs to fully established HCC. RIG-I expression was increased by HFD, which then enhanced cholesterol synthesis and steatosis, and the in-turn NASH and NASH-induced hepatocarcinogenesis. Mechanistically, RIG-I was constitutively mono-methylated at K18 and K146, and demethylase JMJD4-mediated RIG-I demethylation suppressed IL-6-STAT3 signaling. The constitutive methylated RIG-I associated with AMPKα to inhibit HMGCR phosphorylation, thus promoting HMGCR enzymatic activity and cholesterol synthesis. Clinically, RIG-I was decreased in human hepatic precancerous dysplastic nodules while increased in NAFLD livers, which were in accordance with the data in mouse models.

Conclusions

Decreased RIG-I in HcPCs promotes necroinflammation-induced hepatocarcinogenesis, while increased constitutive methylated RIG-I enhances steatosis and NASH-induced hepatocarcinogenesis. JMJD4-demethylated RIG-I prevents both necroinflammation and NASH-induced hepatocarcinogenesis, which provides mechanistic insight and potential target for preventing HCC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13045-022-01381-6.

Strategies for improving the efficacy of immunotherapy in hepatocellular carcinoma

Primary liver cancer, mainly hepatocellular carcinoma (HCC), is the sixth most diagnosed cancer and third leading cause of cancer-related death globally. Recently, immunotherapies such as immune checkpoint inhibitors (ICIs) have made great progress in the systemic treatment of HCC. However, anti-PD-1 therapy with pembrolizumab or nivolumab as a single agent did not meet their predefined end points of overall survival in the KEYNOTE-240 and CheckMate 459 trials. It is urgent to understand the immunological rationale and explore novel ways to improve the efficacy of immunotherapy. The combination of ICIs with other therapies, such as tyrosine kinase inhibitors (TKIs), monoclonal antibodies, or local therapy, has been demonstrated to improve overall response rate and survival. In addition, modulating tumor microenvironment is a potential way to overcome the primary and secondary resistance to immunotherapies. In this review, we summarized the latest findings in the immune microenvironment, the mechanisms of their synergistic effects when combined with anti-VEGF agents or TKIs, as well as other kinds of immune treatment.

High RIG-I and EFTUD2 expression predicts poor survival in endometrial cancer

PURPOSE

Endometrial cancer is the most common gynecological malignancy. The helicase RIG-I, a part of the innate immune system, and EFTUD2, a splicing factor which can upregulate RIG-I expression, are shown to influence tumor growth and disease progression in several malignancies. For endometrial cancer, an immunogenic cancer, data about RIG-I and EFTUD2 are still missing. The aim of this study was to examine the expression of RIG-I and EFTUD2 in endometrial cancer.

METHODS

225 specimen of endometrial cancer were immunohistochemically stained for RIG-I and EFTUD2. The results were correlated to clinicopathological data, overall survival (OS) and progression-free survival (PFS).

RESULTS

High RIG-I expression correlated with advanced tumor stages (FIGO: p = 0.027; pT: p = 0.010) and worse survival rates (OS: p = 0.009; PFS: p = 0.022). High EFTUD2 expression correlated to worse survival rates (OS: p = 0.026; PFS: p < 0.001) and was determined to be an independent marker for progression-free survival.

CONCLUSION

Our data suggest that the expression of RIG-I and EFTUD2 correlates with survival data, which makes both a possible therapeutic target in the future.

Yin Yang 1 promotes aggressive cell growth in high-grade breast cancer by directly transactivating kinectin 1

Invasive cancer growth and metastasis account for the poor prognosis of high-grade breast cancer. Recently, we reported that kinectin 1 (KTN1), a member of the kinesin-binding protein family, promotes cell invasion of triple-negative breast cancer and high-grade breast cancer cells by augmenting the NF-κB signaling pathway. However, the upstream mechanism regulating KTN1 is unknown. Therefore, this functional study was performed to decipher the regulatory cohort of KTN1 in high-grade breast cancer. Bioinformatic analysis indicated that transcription factor Yin Yang 1 (YY1) was a potential transactivator of KTN1. High YY1 expression correlated positively with pathological progression and poor prognosis of high-grade breast cancer. Additionally, YY1 promoted cell invasive growth both in vitro and in vivo, in a KTN1-dependent manner. Mechanistically, YY1 could transactivate the KTN1 gene promoter. Alternatively, YY1 could directly interact with a co-factor, DEAD-box helicase 3 X-linked (DDX3X), which significantly co-activated YY1-mediated transcriptional expression of KTN1. Moreover, DDX3X augmented YY1-KTN1 signaling-promoted invasive cell growth of breast cancer. Importantly, overexpression of YY1 enhanced tumor aggressive growth in a mouse breast cancer model. Our findings established a novel DDX3X-assisted YY1-KTN1 regulatory axis in breast cancer progression, which could lead to the development novel therapeutic targets for breast cancer.

RIG-I acts as a tumor suppressor in melanoma via regulating the activation of the MKK/p38MAPK signaling pathway

Studies have indicated that RIG-I may act as a tumor suppressor and participate in the tumorigenesis of some malignant diseases. However, RIG-I induces distinct cellular responses via different downstream signaling pathways depending on the cell type. To investigate the biological function and underlying molecular mechanism of RIG-I in the tumorigenesis of melanoma, we constructed RIG-I knockout, RIG-I-overexpressing B16-F10 and RIG-I knockdown A375 melanoma cell lines, and analyzed the RIG-I-mediated change in the biological behavior of tumor cells in spontaneous and poly (I:C)-induced RIG-I activation. Cell proliferation, cell cycling, apoptosis and migration were detected by CCK-8 assay, BrdU incorporation assay, Annexin V-PI staining assay and Transwell assay, respectively. In vivo tumorigenicity was evaluated by tumor xenograft growth in nude mice and subsequently by Ki67 staining and TUNEL assays. Furthermore, Western blotting was utilized to explore the underlying mechanism of RIG-I in melanoma cells. Our data showed that RIG-I promotes apoptosis and inhibits proliferation by G1 phase cell cycle arrest in the melanoma cell lines. Mechanistically, RIG-I induced the phosphorylation of p38 MAPK and MAPK kinases MKK3 and MKK4. In conclusion, the current study demonstrated that RIG-I suppressed the development of melanoma by regulating the activity of the MKK/p38 MAPK signaling pathway, which is relevant to research on novel therapeutic targets for this malignant disease.

Leukocyte cell-derived chemotaxin 2 is an antiviral regulator acting through the proto-oncogene MET

Retinoic acid-inducible gene (RIG)-I is an essential innate immune sensor that recognises pathogen RNAs and induces interferon (IFN) production. However, little is known about how host proteins regulate RIG-I activation. Here, we show that leukocyte cell-derived chemotaxin 2 (LECT2), a hepatokine and ligand of the MET receptor tyrosine kinase is an antiviral regulator that promotes the RIG-I-mediated innate immune response. Upon binding to MET, LECT2 induces the recruitment of the phosphatase PTP4A1 to MET and facilitates the dissociation and dephosphorylation of phosphorylated SHP2 from MET, thereby protecting RIG-I from SHP2/c-Cbl-mediated degradation. In vivo, LECT2 overexpression enhances RIG-I-dependent IFN production and inhibits lymphocytic choriomeningitis virus (LCMV) replication in the liver, whereas these changes are reversed in LECT2 knockout mice. Forced suppression of MET abolishes IFN production and antiviral activity in vitro and in vivo. Interestingly, hepatocyte growth factor (HGF), an original MET ligand, inhibits LECT2-mediated anti-viral signalling; conversely, LECT2-MET signalling competes with HGF-MET signalling. Our findings reveal previously unrecognized crosstalk between MET-mediated proliferation and innate immunity and suggest that targeting LECT2 may have therapeutic value in infectious diseases and cancer.

The innate antiviral immune response is an important defense against infection. Here, the authors show that leukocyte cell-derived chemotaxin 2 (LECT2) promotes RIG-I-mediated innate immune responses by preventing its degradation, and inhibits lymphocytic choriomeningitis virus replication in the liver.

Immune Regulator Retinoic Acid-Inducible Gene I (RIG-I) in the Pathogenesis of Cardiovascular Disease

Retinoic acid-inducible gene I (RIG-I) is a cytosolic pattern recognition receptor that contains two CARD domains, an RNA helicase domain, and a C-terminal domain. RIG-I initiates antiviral innate immunity by recognizing exogenous viral RNAs/DNAs. However, some studies have reported that RIG-I activation leads to damage in various organs and tissues in diverse circumstances. Recent studies have shown that RIG-I is involved in cancer, lupus nephritis, immunoglobulin A nephropathy, Crohn’s disease, and atherosclerosis. These reports indicate that RIG-I not only participates in antiviral signaling pathways but also exerts an influence on non-viral infectious diseases. RIG-I is widely expressed in immune and non-immune cells including smooth muscle cells, endothelial cells, and cardiomyocytes. A succinct overview of RIG-I and its signaling pathways, with respect to the cardiovascular system, will aid in the development of novel therapeutics for cardiovascular diseases. In this review, we summarize the structure, activation, signaling pathways, and role of RIG-I in cardiovascular diseases.

Tumor-associated fibroblasts derived exosomes induce the proliferation and cisplatin resistance in esophageal squamous cell carcinoma cells through RIG-I/IFN-β signaling

Esophageal squamous cell carcinoma (ESCC) is a common type of malignant cancer. There is growing evidence suggesting that exosomes may participate in the cellular communication of tumor-associated fibroblasts (TAFs). However, the cisplatin resistance of TAF-derived exosomes to ESCC cells remains to be further studied. Exosomes were isolated from TAFs and characterized with Western blot and TEM assays. ESCC cell lines (TE-1 and KYSE-150) were incubated with TAFs-derived exosomes. To explore the biological function of TAF-derived exosomes in ESCC cell proliferation, apoptosis, and chemosensitivity, we conducted MTT assays and Flow Cytometry. The effects in vivo were also verified via Xenograft mice models. We found that TAFs-derived exosomes led to enhanced cell proliferation and reduced apoptosis of cells, accompanied by increased expression of RIG-I/IFN-β, and TAFs derived exosomes may affect the chemosensitivity to cisplatin via RIG-I/IFN-β signaling in ESCC. Taken together, ESCC cells could communicate with TAFs cells via TAFs-derived exosomes. Our findings might represent a novel mechanism involved in ESCC and may provide a potential biomarker for ESCC.

Robust delivery of RIG-I agonists using extracellular vesicles for anti-cancer immunotherapy

The RIG-I pathway can be activated by RNA containing 5' triphosphate, leading to type I interferon release and immune activation. Hence, RIG-I agonists have been used to induce immune responses against cancer as potential immunotherapy. However, delivery of 5' triphosphorylated RNA molecules as RIG-I agonists to tumour cells in vivo is challenging due to the susceptibility of these molecules to degradation. In this study, we demonstrate the use of extracellular vesicles (EVs) from red blood cells (RBCs), which are highly amenable for RNA loading and taken up robustly by cancer cells, for RIG-I agonist delivery. We evaluate the anti-cancer activity of two novel RIG-I agonists, the immunomodulatory RNA (immRNA) with a unique secondary structure for efficient RIG-I activation, and a 5' triphosphorylated antisense oligonucleotide with dual function of RIG-I activation and miR-125b inhibition (3p-125b-ASO). We find that RBCEV-delivered immRNA and 3p-125b-ASO trigger the RIG-I pathway, and induce cell death in both mouse and human breast cancer cells. Furthermore, we observe a significant suppression of tumour growth coupled with increased immune cell infiltration mediated by the activation of RIG-I cascade after multiple intratumoral injections of RBCEVs loaded with immRNA or 3p-125b-ASO. Targeted delivery of immRNA using RBCEVs with EGFR-binding nanobody administrated via intrapulmonary delivery facilitates the accumulation of RBCEVs in metastatic cancer cells, leading to potent tumour-specific CD8+ T cells immune response. This contributes to prominent suppression of breast cancer metastasis in the lung. Hence, this study provides a new strategy for efficient RIG-I agonist delivery using RBCEVs for immunotherapy against cancer and cancer metastasis.

Gender-specific development of experimental autoimmune cholangitis induced by double-stranded RNA

Here we investigated the gender difference in murine cholangitis resembling human primary biliary cholangitis (PBC) caused by synthetic double-stranded RNA, and underlying hepatic innate immune responses. Female C57Bl/6 mice given repeated injections of polyinosinic-polycytidylic acid (poly I:C) for 24 weeks developed overt cholangitis with positive serum anti-mitochondria-M2 antibody, whereas male mice showed minimal pathological changes without induction in autoantibody. Poly I:C induced hepatic inflammatory cytokines and type-I interferons predominantly in females. Hepatic expression levels of toll-like receptor (TLR) 3 and melanoma differentiation-associated protein (MDA) 5 were equivalent in both genders; however, both mRNA and protein levels of retinoic acid-inducible gene (RIG)-I were nearly doubled in female livers. Following 4-week injections of poly I:C, not only hepatic RIG-I, but also TLR3 and MDA5 showed female-predominance. Moreover, hepatic RIG-I levels were 25% lower in ovariectomized mice, whereas supplementation of 17 β-estradiol enhanced hepatic RIG-I expression, as well as cytokine induction. These results clearly indicate that hepatic RIG-I expression is potentiated by estrogen, and triggers gender-dependent hepatic innate immune response against double-stranded RNA, which most likely play a pivotal role in the pathogenesis of autoimmune cholangiopathies including PBC.

MXD3 as an Immunological and Prognostic Factor From Pancancer Analysis

MAX dimerization protein 3 (MXD3), a transcriptional regulator of the MXD3 superfamily, is a part of the MYC–MAX–MXD network. However, its role in tumors has been reported in several cancers, such as B-cell acute lymphoblastic leukemia, medulloblastoma, neuroblastoma, and glioblastoma. Based on TCGA and GEO data, our first pancancer study of MXD3 confirmed the high expression of MXD3 in cancer tissues. Our results revealed that patients suffering from cancers with higher MXD3 expression had poor OS, DSS, DFI, and PFI. We further explored the methylation status of the MXD3 gene body and gene promoter in cancer. Patients with a higher MXD3 gene body have better OS, while the prognosis of patients with a high MXD3 promoter is more complex. We also verified the differential expression of three clinical phenotypes of MXD3: age, sex, and tumor stage, in a variety of tumors, suggesting a correlation between MXD3 and clinical characteristics. We explored the negative relationship between MXD3 and TMB and MSI in most types of cancer, indicating the poor prognosis of patients with high MXD3 expression. We further investigated the relationship between MXD3 and immune infiltrating cells and identified the relationship between MXD3 and immune genes, immunosuppressive genes, and antigen-presenting genes. All of the above findings established a solid relationship between MXD3 and the immune environment and immune cells. These results demonstrated that MXD3 might also be a potential immune factor. We also found a higher expression of MXD3 and promoter according to the increasing glioma WHO grade or histologic types. Glioma patients with high MXD3 or MXD3 promoter expression had poor survival. Finally, we used IHC to verify the higher expression of MXD3 in glioma samples compared to normal samples. Our study shows that MXD3, as a poor prognostic factor, plays a significant role in many cancers, especially glioma. Although more clinical evidence for MXD3 as a clinical therapeutic target and an immunotherapy site is needed, MXD3 can play an important guiding role in multiple clinical treatments, including immunotherapy and demethylation therapy.

Pattern Recognition Receptors (PRRs) in Macrophages Possess Prognosis and Immunotherapy Potential for Melanoma

Background

Pattern recognition receptors (PRRs) family plays a vital role in the initial stage of innate immune response and the subsequent activation of adaptive immunity. Increasing evidences have indicated that several PRRs play critical roles in the progress of inflammation and tumorigenesis. However, the comprehensive significance of PRRs family in clinical prognosis of different cancers is still elusive.

Methods

We analyzed expression of 20 canonical PRRs in tumor samples from 9502 patients of 33 tumor types. Next, we used expression profiles of PRRs in skin cutaneous melanoma (SKCM) to build a Cox prognosis model. Then, we analyzed immune infiltration features and immune activity of high risk score and low risk score patients. Finally, we analyzed the single-cell sequencing data of different cancers and detected the expression of PRRs in mouse melanoma model to identify PRRs-expressing cell types.

Results

We found PRRs had a significantly positive correlation with prognosis in SKCM rather than other tumors, and PRR-based Cox model had a much better prognosis potential than any single PRR. Further analysis shows risk score could indicate immunocyte infiltration and immune activity in SKCM. We also found the expressions of some PRR genes were highly correlated with the expression of immune checkpoints molecules in SKCM, indicating they could be indicators for clinical immune therapy. Finally, we found only in SKCM samples, the expression of PRRs is especially high in a subpopulation of macrophages with a trait of CD206 low expression, probably explaining why PRRs have prognosis potential in melanoma.

Conclusions

Our study reveals PRR family in macrophages has a positive prognosis potential in melanoma and could be valuable for clinical prognosis and immune therapy.

Deficiency of GFRα1 promotes hepatocellular carcinoma progression but enhances oxaliplatin-mediated anti-tumor efficacy

Neurotrophic factors and their receptors have been identified to promote tumor progression. GFRα1, the receptor for glial cell line-derived neurotrophic factor (GDNF), has been demonstrated to be predominantly expressed in adult liver tissue. Our preliminary data showed that GFRα1 is significantly downregulated in hepatocellular carcinoma (HCC) tissue, compared to the matched non-neoplastic tissue. However, the role of GFRα1 in HCC progression remains unknown. Here we found that the expression of GFRα1 in HCC tissue is inversely correlated with the poorer prognosis of HCC patients. Silencing of GFRα1 expression markedly enhances HCC cell growth, tumor metastasis, as well as shortens the survival of HCC tumor-bearing mice. Forced expression of GFRα1 in HCC cells significantly reverses the tumor-promoting effects of GFRα1 silencing, and AAV8-mediated GFRα1 transfection in HCC tumor tissues significantly impedes tumor growth and prolongs the survival of HCC tumor-bearing mice. These results are also verified in vivo in GFRα1 knock-out mice model, with increased DEN-induced HCC carcinogenesis. Mechanistically, GFRα1 could inhibit epithelial-to-mesenchymal transition (EMT) of HCC cells, by upregulating expression of Claudin-1 and ZO-1. Of note, silencing of GFRα1 expression promotes oxaliplatin-mediated HCC cell apoptosis resulting in prolonged survival of HCC-bearing mice, and forced expression of GFRα1 markedly increased oxaliplatin resistance of HCC cells. These results demonstrate that deficiency of GFRα1 promotes HCC progression but enhances chemotherapeutic anti-tumor efficacy, suggesting that GFRα1 may be a candidate prognostic biomarker and a potential therapeutic target in HCC.

Curcumin inhibited hepatitis B viral entry through NTCP binding

Hepatitis B virus (HBV) has been implicated in hepatitis and hepatocellular carcinoma. Current agents (nucleos(t)ide analogs and interferons) could only attenuate HBV infection. A combination of agents targeting different stages of viral life cycle (e.g., entry, replication, and cccDNA stability) was expected to eradicate the infection. Curcumin (CCM) was investigated for inhibitory action toward HBV attachment and internalization. Immortalized hepatocyte-like cells (imHCs), HepaRG and non-hepatic cells served as host cells for binding study with CCM. CCM decreased viral load, HBeAg, HBcAg (infectivity), intracellular HBV DNA, and cccDNA levels. The CCM-induced suppression of HBV entry was directly correlated with the density of sodium-taurocholate co-transporting polypeptide (NTCP), a known host receptor for HBV entry. The site of action of CCM was confirmed using TCA uptake assay. The affinity between CCM and NTCP was measured using isothermal titration calorimetry (ITC). These results demonstrated that CCM interrupted HBV entry and would therefore suppress HBV re-infection.

MAVS: A Two-Sided CARD Mediating Antiviral Innate Immune Signaling and Regulating Immune Homeostasis

Mitochondrial antiviral signaling protein (MAVS) functions as a "switch" in the immune signal transduction against most RNA viruses. Upon viral infection, MAVS forms prion-like aggregates by receiving the cytosolic RNA sensor retinoic acid-inducible gene I-activated signaling and further activates/switches on the type I interferon signaling. While under resting state, MAVS is prevented from spontaneously aggregating to switch off the signal transduction and maintain immune homeostasis. Due to the dual role in antiviral signal transduction and immune homeostasis, MAVS has emerged as the central regulation target by both viruses and hosts. Recently, researchers show increasing interest in viral evasion strategies and immune homeostasis regulations targeting MAVS, especially focusing on the post-translational modifications of MAVS, such as ubiquitination and phosphorylation. This review summarizes the regulations of MAVS in antiviral innate immune signaling transduction and immune homeostasis maintenance.

RNA sequencing analysis reveals the competing endogenous RNAs interplay in resected hepatocellular carcinoma patients who received interferon-alpha therapy

BACKGROUND

Interferon-alpha (IFN-α) is a general therapeutic regimen to be utilized in hepatocellular carcinoma (HCC). However, regulatory mechanisms of IFN-α on competing endogenous RNAs (ceRNAs) level in anti-HCC relapse are rarely understood.

METHODS

HCC patients with and without IFN-α treatment were calculated to analyze the expression profile of mRNA, long non-coding RNA (lncRNA), microRNA (miRNA), and circular RNA (circRNA) by RNA sequence, and significant differential expression (DE) of these types of RNAs were selected for further analysis. A ceRNA regulatory network was constructed to explore the potential mechanisms of IFN-α intervention on anti-HCC relapse. Finally, the potential prognostic associated genes among these DE RNAs were identified.

RESULTS

Totally, 556 mRNAs, 120 circRNAs, 87 lncRNAs, and 96 miRNAs were differentially expressed in patients who received IFN-α treatment. A ceRNA regulatory network including a circRNA-miRNA-mRNA network which composed of 4 up- and 10 down-regulated circRNAs, 8 up- and 5 down-regulated miRNAs, 28 up- and 9 down-regulated mRNAs, and a lncRNA-miRNA-mRNA network which composed of 10 up- and 3 down-regulated lncRNAs, 11 up- and 5 down-regulated miRNAs, 28 up- and 10 down-regulated mRNAs was constructed. Gene enrichment and pathway analysis revealed that the ceRNA network was associated with immune-related pathway and corresponding molecular function in patients who accepted IFN-α treatment. Next, we identified 3 most relevant to IFN-α treatment to HCC among these DE RNAs, namely FAM20A, IGFBP4 and MARCH3, as the prognostic associated genes for HCC. Furthermore, MARCH3 expression correlated with infiltrating levels of tumor infiltrating immune cells (TICCs) in HCC. MARCH3 expression also showed strong correlations with the gene markers of diverse immune cells in HCC.

CONCLUSION

Our data discovered a novel ceRNA network in HCC patients receiving IFN-α therapy, which might lay the foundation for better understand the regulatory mechanism of IFN-α treatment.

CCDC65 as a new potential tumor suppressor induced by metformin inhibits activation of AKT1 via ubiquitination of ENO1 in gastric cancer

The coiled-coil domain containing protein members have been well documented for their roles in many diseases including cancers. However, the function of the coiled-coil domain containing 65 (CCDC65) remains unknown in tumorigenesis including gastric cancer. Methods: CCDC65 expression and its correlation with clinical features and prognosis of gastric cancer were analyzed in tissue. The biological role and molecular basis of CCDC65 were performed via in vitro and in vivo assays and a various of experimental methods including co-immunoprecipitation (Co-IP), GST-pull down and ubiquitination analysis et al. Finally, whether metformin affects the pathogenesis of gastric cancer by regulating CCDC65 and its-mediated signaling was investigated. Results: Here, we found that downregulated CCDC65 level was showed as an unfavourable factor in gastric cancer patients. Subsequently, CCDC65 or its domain (a.a. 130-484) was identified as a significant suppressor in GC growth and metastasis in vitro and in vivo. Molecular basis showed that CCDC65 bound to ENO1, an oncogenic factor has been widely reported to promote the tumor pathogenesis, by its domain (a.a. 130-484) and further promoted ubiquitylation and degradation of ENO1 by recruiting E3 ubiquitin ligase FBXW7. The downregulated ENO1 decreased the binding with AKT1 and further inactivated AKT1, which led to the loss of cell proliferation and EMT signal. Finally, we observed that metformin, a new anti-cancer drug, can significantly induce CCDC65 to suppress ENO1-AKT1 complex-mediated cell proliferation and EMT signals and finally suppresses the malignant phenotypes of gastric cancer cells. Conclusion: These results firstly highlight a critical role of CCDC65 in suppressing ENO1-AKT1 pathway to reduce the progression of gastric cancer and reveals a new molecular mechanism for metformin in suppressing gastric cancer. Our present study provides a new insight into the mechanism and therapy for gastric cancer.

Upregulation of HOXC9 generates interferon-gamma resistance in gastric cancer by inhibiting the DAPK1/RIG1/STAT1 axis

Clinical reports indicate that gastric cancer (GC) has a high mortality rate, but its pathological mechanism remains poorly understood. This work integrated bioinformatics analysis with experimental verification to explore novel biomarkers of gastric cancer. First, weighted gene coexpression network analysis was applied to screen significant genes correlated with GC development. Gene set enrichment analysis was also used to unearth the most relevant biological functions of significant genes. As a result, we discovered homeobox C9 (HOXC9) as a novel oncogene in GC, primarily through negatively regulating immune response. High expression of HOXC9 predicted a poor prognosis in GC patients, and knocking down HOXC9 efficiently enhanced the interferon‐gamma (IFNγ)‐dependent apoptosis in two GC cell lines as well as organoids from patients. Furthermore, cleaved caspase‐3/7 and phosphorylated signal transducer and activator of transcription 1 (p‐STAT1) were also significantly enhanced in HOXC9 knockdown cells and organoids treated with IFNγ. Mechanistically, we found that HOXC9 inhibited the death‐associated protein kinase 1 (DAPK1) and its downstream retinoic acid‐inducible gene‐I (RIG1) to generate GC IFNγ resistance. In summary, we identified and confirmed that HOXC9 generates IFNγ resistance in GC by inhibiting the DAPK1/RIG1/p‐STAT1 axis.

SARS-CoV-2 Spike protein enhances ACE2 expression via facilitating Interferon effects in bronchial epithelium

Objective

In this study, we focused on the interaction between SARS-CoV-2 and host Type I Interferon (IFN) response, so as to identify whether IFN effects could be influenced by the products of SARS-CoV-2.

Methods

All the structural and non-structural proteins of SARS-CoV-2 were transfected and overexpressed in the bronchial epithelial cell line BEAS-2B respectively, and typical antiviral IFN-stimulated gene (ISG) ISG15 expression was detected by qRT-PCR. RNA-seq based transcriptome analysis was performed between control and Spike (S) protein-overexpressed BEAS-2B cells. The expression of ACE2 and IFN effector JAK-STAT signaling activation were detected in control and S protein-overexpressed BEAS-2B cells by qRT-PCR or/and Western blot respectively. The interaction between S protein with STAT1 and STAT2, and the association between JAK1 with downstream STAT1 and STAT2 were measured in BEAS-2B cells by co-immunoprecipitation (co-IP).

Results

S protein could activate IFN effects and downstream ISGs expression. By transcriptome analysis, overexpression of S protein induced a set of genes expression, including series of ISGs and the SARS-CoV-2 receptor ACE2. Mechanistically, S protein enhanced the association between the upstream JAK1 and downstream STAT1 and STAT2, so as to promote STAT1 and STAT2 phosphorylation and ACE2 expression.

Conclusion

SARS-CoV-2 S protein enhances ACE2 expression via facilitating IFN effects, which may help its infection.

Lipotoxicity reduces DDX58/Rig-1 expression and activity leading to impaired autophagy and cell death

Nonalcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease globally. NAFLD is a consequence of fat accumulation in the liver leading to lipotoxicity. Increasing evidence has demonstrated the critical role of autophagy in NAFLD. This study uncovers the unexpected role of immune surveillance protein DDX58/Rig-1 (DExD/H box helicase 58) in activating macroautophagy/autophagy and protecting from lipotoxicity associated with NAFLD. Here we show for the first time that DDX58 protein is significantly reduced in nonalcoholic steatohepatitis (NASH) mouse model, an aggressive form of NAFLD characterized by inflammation and fibrosis of the liver. In addition to decreased expression of DDX58, we found that DDX58 activity can be attenuated by treatments with palmitic acid (PA), a saturated fatty acid. To investigate whether PA inhibition of DDX58 is harmful to the cell, we characterized DDX58 function in hepatocytes when exposed to high doses of PA in the presence and/or absence of DDX58. We show that siRNA knockdown of DDX58 promotes apoptosis. Importantly, we show that stable overexpression of DDX58 is protective against toxic levels of PA and stimulates autophagy. This study begins to demonstrate the regulation of the autophagy receptor protein SQSTM1/p62 through DDX58. DDX58 expression directly influences SQSTM1 mRNA and protein levels. This work proposes a model in which activating DDX58 increases an autophagic response and this aids in clearing toxic lipid inclusion bodies, which leads to inflammation and apoptosis. Activating a DDX58-induced autophagy response may be a strategy for treating NAFLD.Abbreviations:5'pppdsRNA: 5' triphosphate double-stranded RNA; CDAHFD: choline-deficient, L-amino acid defined high-fat diet; CEBPB: CCAAT/enhancer binding protein (C/EBP), beta; CQ: chloroquine; DDX58/retinoic acid inducible gene 1/Rig-1: DExD/H box helicase 58; h: hours; IFIH1/MDA5: interferon induced with helicase C domain 1; IFNB/IFN-β: interferon beta 1, fibroblast; KO: knockout; MAVS: mitochondrial antiviral signaling protein; NAFLD: nonalcoholic fatty liver disease; NASH: nonalcoholic steatohepatitis; NFKB/NF-κB: nuclear factor of kappa light polypeptide gene enhancer in B cells; PA: palmitic acid; poly:IC: polyinosinic:polycytidylic acid; PRR: pattern recognition receptors; PSR: picrosirus red; RAP: rapamycin; RLR: RIG-I-like receptor; SQSTM1/p62: sequestosome 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK-binding kinase 1.

Signal-transducing innate receptors in tumor immunity

The signal‐transducing innate receptors represent classes of pattern recognition receptors (PRRs) that play crucial roles in the first line of the host defense against infections by the recognition of pathogen‐derived molecules. Because of their poorly discriminative nature compared with antigen receptors of the adaptive immune system, they also recognize endogenous molecules and evoke immune responses without infection, resulting in the regulation of tumor immunity. Therefore, PRRs may be promising targets for effective cancer immunotherapy, either by activating or inhibiting them. Here, we summarize our current knowledge of signal‐transducing PRRs in the regulation of tumor immunity.

Aldehyde Dehydrogenase 2 Mediates Alcohol-Induced Colorectal Cancer Immune Escape through Stabilizing PD-L1 Expression

Despite the great success of immunotherapy in a small subset of cancer patients, most colorectal cancer (CRC) patients do not respond to programmed cell death receptor 1 (PD-1) blockade immunotherapy. There is an urgent medical need to elucidate how cancer cells evade immune response and to develop novel means to boost the efficacy of immune checkpoint inhibitors. In this study, alcohol induces ligand programmed cell death receptor 1 (PD-L1) expression of CRC cells in vitro and in vivo. Alcohol exposure is shown to induce aldehyde dehydrogenase 2 (ALDH2) expression that is a crucial enzyme involved in alcohol metabolism, and low level of lymphocytes infiltration in the murine CRC model and patients. Intriguingly, ALDH2 and PD-L1 protein expression are positively correlated in tumor tissues from the CRC patients. Mechanistically, ALDH2 stabilizes PD-L1 protein expression by physically interacting with the intracellular segment of PD-L1 and inhibiting its proteasome-dependent degradation mediated by an E3 ubiquitin ligase Speckle Type POZ Protein (SPOP). Importantly, inhibition of ALDH2 reduces PD-L1 protein in CRC cells and promotes tumor-infiltrating T cells (TILs) infiltration, presumably leading to the significant potentiation of anti-PD-1 antibody efficacy in a mouse CT26 CRC model. The findings highlight a crucial role played by ALDH2 to facilitate alcohol-mediated tumor escape from immunity surveillance and promote tumor progression.

Bioinformatics analysis of mRNA and miRNA microarray to identify the key miRNA-mRNA pairs in cisplatin-resistant ovarian cancer

Background

Ovarian cancer (OC) is a gynecological malignancy with the highest mortality rate. Cisplatin (DDP) based chemotherapy is a standard strategy for ovarian cancer. Despite good response rates for initial chemotherapy, almost 80% of the patients treated with DDP based chemotherapy will experience recurrence due to drug-resistant, which will ultimately result in fatality. The aim of the present study was to examine the pathogenesis and potential molecular markers of cisplatin-resistant OC by studying the differential expression of mRNAs and miRNAs between cisplatin resistant OC cell lines and normal cell lines.

Methods

Two mRNA datasets (GSE58470 and GSE45553) and two miRNA sequence datasets (GSE58469 and GSE148251) were downloaded from the Gene expression omnibus (GEO) database. Differentially expressed genes (DEGs) and differentially expressed miRNAs (DEMs) were screened by the NetworkAnalyst. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted to analyze the biological functions of DEGs. The protein-protein interaction network was constructed using STRING and Cytoscape software to identify the molecular mechanisms of key signaling pathways and cellular activities. FunRich and MiRNATip databases were used to identify the target genes of the DEMs.

Results

A total of 380 DEGs, and 5 DEMs were identified. Protein–protein interaction (PPI) network of DEGs containing 379 nodes and 1049 edges was constructed, and 4 key modules and 24 hub genes related to cisplatin-resistant OC were screened. Two hundred ninety-nine target genes of the 5 DEMs were found out. Subsequently, one of these 299 target genes (UBB) belonging to the hub genes of GSE58470 and GSE45553 was identified by MCODE and CytoHubba,which was regulated by one miRNA (mir-454).

Conclusions

One miRNA–mRNA regulatory pairs (mir-454-UBB) was established. Taken together, our study provided evidence concerning the alteration genes involved in cisplatin-resistant OC, which will help to unravel the mechanisms underlying drug resistant.

The Mitochondrial Protein MAVS Stabilizes p53 to Suppress Tumorigenesis

Recent reports have shown the critical role of the mitochondrial antiviral signaling (MAVS) protein in virus-induced apoptosis, but the involvement of MAVS in tumorigenesis is still poorly understood. Herein, we report that MAVS is a key regulator of p53 activation and is critical for protecting against tumorigenesis. We find that MAVS promotes p53-dependent cell death in response to DNA damage. MAVS interacts with p53 and mediates p53 mitochondrial recruitment under genotoxic stress. Mechanistically, MAVS inhibits p53 ubiquitination by blocking the formation of the p53-murine double-minute 2 (MDM2) complex, leading to the stabilization of p53. Notably, compared with their wild-type littermates, MAVS knockout mice display decreased resistance to azoxymethane (AOM) or AOM/dextran sulfate sodium salt (DSS)-induced colon cancer. MAVS expression is significantly downregulated in human colon cancer tissues. These results unveil roles for MAVS in DNA damage response and tumor suppression.

A hexokinase isoenzyme switch in human liver cancer cells promotes lipogenesis and enhances innate immunity

During the cancerous transformation of normal hepatocytes into hepatocellular carcinoma (HCC), the enzyme catalyzing the first rate-limiting step of glycolysis, namely the glucokinase (GCK), is replaced by the higher affinity isoenzyme, hexokinase 2 (HK2). Here, we show that in HCC tumors the highest expression level of HK2 is inversely correlated to GCK expression, and is associated to poor prognosis for patient survival. To further explore functional consequences of the GCK-to-HK2 isoenzyme switch occurring during carcinogenesis, HK2 was knocked-out in the HCC cell line Huh7 and replaced by GCK, to generate the Huh7-GCK⁺/HK2⁻ cell line. HK2 knockdown and GCK expression rewired central carbon metabolism, stimulated mitochondrial respiration and restored essential metabolic functions of normal hepatocytes such as lipogenesis, VLDL secretion, glycogen storage. It also reactivated innate immune responses and sensitivity to natural killer cells, showing that consequences of the HK switch extend beyond metabolic reprogramming.

Many cancers fuel their rapid growth by replacing glucokinase with its higher affinity isoenzyme, hexokinase 2 (HK2), making HK2 an attractive drug target. In this study, Perrin-Cocon and Vidalain et al. use CRISPR/Cas-9 gene editing to reverse this enzymatic switch in human liver cancer cells, and find this restores innate immune function as well as reversing cancer-associated metabolic reprogramming.