microRNA-34a-Upregulated Retinoic Acid-Inducible Gene-I Promotes Apoptosis and Delays Cell Cycle Transition in Cervical Cancer Cells

RIG-I-like receptors: Molecular mechanism of activation and signaling

During RNA viral infection, RIG-I-like receptors (RLRs) recognize the intracellular pathogenic RNA species derived from viral replication and activate antiviral innate immune response by stimulating type 1 interferon expression. Three RLR members, namely, RIG-I, MDA5, and LGP2 are homologous and belong to a subgroup of superfamily 2 Helicase/ATPase that is preferably activated by double-stranded RNA. RLRs are significantly different in gene architecture, RNA ligand preference, activation, and molecular functions. As switchable macromolecular sensors, RLRs' activities are tightly regulated by RNA ligands, ATP, posttranslational modifications, and cellular cofactors. We provide a comprehensive review of the structure and function of the RLRs and summarize the molecular understanding of sensing and signaling events during the RLR activation process. The key roles RLR signaling play in both anti-infection and immune disease conditions highlight the therapeutic potential in targeting this important molecular pathway.

The Innate Immune Signalling Pathways: Turning RIG-I Sensor Activation Against Cancer

Over the last 15 years, the ability to harness a patient's own immune system has led to significant progress in cancer therapy. For instance, immunotherapeutic strategies, including checkpoint inhibitors or adoptive cell therapy using chimeric antigen receptor T-cell (CAR-T), are specifically aimed at enhancing adaptive anti-tumour immunity. Several research groups demonstrated that adaptive anti-tumour immunity is highly sustained by innate immune responses. Host innate immunity provides the first line of defence and mediates recognition of danger signals through pattern recognition receptors (PRRs), such as cytosolic sensors of pathogen-associated molecular patterns (PAMPs) and damage-associated molecular pattern (DAMP) signals. The retinoic acid-inducible gene I (RIG-I) is a cytosolic RNA helicase, which detects viral double-strand RNA and, once activated, triggers signalling pathways, converging on the production of type I interferons, proinflammatory cytokines, and programmed cell death. Approaches aimed at activating RIG-I within cancers are being explored as novel therapeutic treatments to generate an inflammatory tumour microenvironment and to facilitate cytotoxic T-cell cross-priming and infiltration. Here, we provide an overview of studies regarding the role of RIG-I signalling in the tumour microenvironment, and the most recent preclinical studies that employ RIG-I agonists. Lastly, we present a selection of clinical trials designed to prove the antitumour role of RIG I and that may result in improved therapeutic outcomes for cancer patients.

Human Papillomavirus Infections, Cervical Cancer and MicroRNAs: An Overview and Implications for Public Health

Human Papillomavirus (HPV) is among the most common sexually transmitted infections in both females and males across the world that generally do not cause symptoms and are characterized by high rates of clearance. Persistent infections due at least to twelve well-recognized High-Risk (HR) or oncogenic genotypes, although less frequent, can occur, leading to diseases and malignancies, principally cervical cancer. Three vaccination strategies are currently available for preventing certain HR HPVs-associated diseases, infections due to HPV6 and HPV11 low-risk types, as well as for providing cross-protection against non-vaccine genotypes. Nevertheless, the limited vaccine coverage hampers reducing the burden of HPV-related diseases globally. For HR HPV types, especially HPV16 and HPV18, the E6 and E7 oncoproteins are needed for cancer development. As for other tumors, even in cervical cancer, non-coding microRNAs (miRNAs) are involved in posttranscriptional regulation, resulting in aberrant expression profiles. In this study, we provide a summary of the epidemiological background for HPV occurrence and available immunization programs. In addition, we present an overview of the most relevant evidence of miRNAs deregulation in cervical cancer, underlining that targeting these biomolecules could lead to wide translational perspectives, allowing better diagnosis, prognosis and therapeutics, and with valuable applications in the field of prevention. The literature on this topic is rapidly growing, but advanced investigations are required to achieve more consistent findings on the up-regulated and down-regulated miRNAs in cervical carcinogenesis. Because the expression of miRNAs is heterogeneously reported, it may be valuable to assess factors and risks related to individual susceptibility.

miR-639 Expression Is Silenced by DNMT3A-Mediated Hypermethylation and Functions as a Tumor Suppressor in Liver Cancer Cells

Emerging evidence has indicated that abnormal methylation of DNA contributes to hepatocarcinogenesis. However, the regulatory mechanisms are not well known. Here, we revealed that microRNA-639 (miR-639) expression is downregulated in liver cancer tissues and cells. The repression of miR-639 expression was attributed to hypermethylation in its promoter region, and DNA methyltransferase (DNMT3A) was found to mediate this hypermethylation. Repression of miR-639 expression promoted cell growth and migration/invasion in vitro and the growth of tumors in xenograft mouse models. Furthermore, miR-639 bound to the 3' UTR of both MYST2 and ZEB1 and suppressed their expression. MYST2 promoted the growth of liver cancer cells and ZEB1 facilitated the migration/invasion of liver cancer cells. Ectopic expression of MYST2 and ZEB1 counteracted the repression of malignancy induced by miR-639, which coincided with the reciprocal correlation between miR-639 and MYST2 and ZEB1 expression in clinical hepatocellular carcinoma (HCC) tissues. Thus, DNMT3A-mediated hypermethylation suppressed miR-639 expression, derepressing the expression of MSYT2 and ZEB1, which promoted tumorigenesis of liver cancer. These findings may shed light on the mechanism of abnormal expression of miRNAs involved in the malignancy of liver cancer and provide new biomarkers for liver cancer.

The RIG-I pathway is involved in peripheral T cell lymphopenia in patients with dermatomyositis

BACKGROUND

Peripheral T cell lymphopenia is a clinical phenomenon in some patients with dermatomyositis (DM). Patients with T cell lymphopenia are more susceptible to life-threatening infections. However, the pathogenesis of T cell lymphopenia remains unclear. In this study, we aimed to determine retinoic acid-inducible gene I (RIG-I) expression in peripheral T lymphocytes and explore the correlation between RIG-I and T cell lymphopenia in DM.

METHODS

The mRNA and protein expression levels of RIG-I were determined in peripheral T lymphocytes of 26 treatment-naive DM patients by q-PCR and Western blot. The apoptosis of peripheral T lymphocytes was detected by flow cytometry. The associations between RIG-I expression levels and clinical characteristics were investigated. In Jurkat cell, we examined the relationship between RIG-I and cell apoptosis following RIG-I overexpression or activation by specific ligand (pppRNA). The CRISPR/Cas9 gene editing system was used for RIG-I knockout. Fas and caspase 3 were identified by Western blot. CCK8 colorimeter was performed to monitor cell proliferation.

RESULTS

In DM patients, we observed the peripheral T lymphocyte count decreased notably while the apoptosis of T lymphocytes increased significantly compared with healthy control. RIG-I expression levels in peripheral T cell correlated negatively with T cell count in DM patients. RIG-I protein expression decreased significantly, and the number of T cell increased when disease was improved. In Jurkat cells, increased apoptosis and elevated expression of Fas and cleaved-caspase 3 protein were observed following RIG-I overexpression or RIG-I-specific ligand (pppRNA) activation. Meanwhile, the proliferation of Jurkat cells was markedly reduced. Whereas, neither cell apoptosis nor the cell viability of the RIG-I knockout clones exhibited significant changes following pppRNA activation.

CONCLUSION

Our study showed for the first time that negative correlation between the increased RIG-I expression in peripheral T lymphocyte and T cell count in some patients with DM. We demonstrated that highly expressed RIG-I played a critical role in inducing apoptosis and inhibiting proliferation of T lymphocyte in vitro. Therefore, RIG-I-mediated apoptosis may be one of the possible mechanisms of T cell lymphopenia in some patients with DM. These findings expand our existing knowledge on the mechanisms of innate immunity in pathogenesis and provide new therapeutic avenues for DM.

Competing endogenous RNA networks in cervical cancer: function, mechanism and perspective

In the past several years, competing endogenous RNAs (ceRNAs) have emerged as a potential class of post-transcriptional regulators that alter gene expression through a microRNA (miRNA)-mediated mechanism. An increasing number of studies have found that ceRNAs play important roles in tumorigenesis. Cervical cancer is one of the most common cancers in female malignancies. Despite advances in our understanding of this neoplasm, patients with advanced cervical cancer still have poor prognosis. There is an urgent need to provide a new insight on the mechanism of cervical cancer development and may be acted as new anticancer therapeutic strategies. Here, we review the ceRNA studies and coherent researches in cervical cancer, especially in long non-coding RNA (lncRNA) and miRNAs in order to broaden horizons into mechanisms, selection biomarkers for diagnosis as well as predicting prognosis, and targeting treatment for cervical cancer in the future.

MicroRNAs in gynecological cancers: Small molecules with big implications

Gynecological cancers (GCs) are often diagnosed at advanced stages, limiting the efficacy of available therapeutic options. Thus, there remains an urgent and unmet need for innovative research for the efficient clinical management of GC patients. Research over past several years has revealed the enormous promise of miRNAs. These small non-coding RNAs can aid in the diagnosis, prognosis and therapy of all major GCs, viz., ovarian cancers, cervical cancers and endometrial cancers. Mechanistic details of the miRNAs-mediated regulation of multiple biological functions are under constant investigation, and a number of miRNAs are now believed to influence growth, proliferation, invasion, metastasis, chemoresistance and the relapse of different GCs. Modulation of tumor microenvironment by miRNAs can possibly explain some of their reported biological effects. miRNA signatures have been proposed as biomarkers for the early detection of GCs, even the various subtypes of individual GCs. miRNA signatures are also being pursued as predictors of response to therapies. This review catalogs the knowledge gained from collective studies, so as to assess the progress made so far. It is time to ponder over the knowledge gained, so that more meaningful pre-clinical and translational studies can be designed to better realize the potential that miRNAs have to offer.

Maspin suppresses growth, proliferation and invasion in cutaneous squamous cell carcinoma cells

Cutaneous squamous cell carcinoma (cSCC) is a common malignant tumor. Mammary serine protease inhibitor (Maspin), a member of serpin family, has been reported as a tumor suppressor in various carcinomas. In this study, we detected the expression level of Maspin in cSCC tissues by real-time PCR and western blotting, and found that Maspin was downregulated in the cSCC tissues compared with the adjacent normal tissues. Moreover, Maspin was stably overexpressed in A431 cells, and CCK-8 assay, colony formation assay, Transwell assay, Hoechst staining and western blotting were carried out to detect the growth, proliferation, invasion, cell cycle and apoptosis of A431 cells. The results revealed that overexpression of Maspin inhibited growth, proliferation, invasion and cell cycle G1/S/G2 transition and enhanced apoptosis of A431 cells. The pro-apoptotic protein cleaved caspase-3, poly(ADP-ribose) polymerase (PARP) and Bax increased, and the anti-apoptotic protein Bcl-2 decreased after Maspin overexpression. Therefore, we demonstrated that Maspin suppressed growth, proliferation and invasion by delaying cell cycle transition and promoting apoptosis in cSCC cells, which may provide new insights for the clinical diagnosis and therapy of cSCC.

Crosstalk between Cytoplasmic RIG-I and STING Sensing Pathways

Detection of evolutionarily conserved molecules on microbial pathogens by host immune sensors represents the initial trigger of the immune response against infection. Cytosolic receptors sense viral and intracellular bacterial genomes, as well as nucleic acids produced during replication. Once activated, these sensors trigger multiple signaling cascades, converging on the production of type I interferons and proinflammatory cytokines. Although distinct classes of receptors are responsible for the RNA and DNA sensing, the downstream signaling components are physically and functionally interconnected. This review highlights the importance of the crosstalk between retinoic acid inducible gene-I (RIG-I)-mitochondrial antiviral-signaling protein (MAVS) RNA sensing and the cyclic GMP-AMP synthase (cGAS)- stimulator of interferon genes (STING) DNA sensing pathways in potentiating efficient antiviral responses. The potential of cGAS-STING manipulation as a component of cancer immunotherapy is also reviewed.

Use of Mature miRNA Strand Selection in miRNAs Families in Cervical Cancer Development

Aberrant miRNA expression is well recognized as a cancer hallmark, nevertheless miRNA function and expression does not always correlate in patients tissues and cell lines studies. In addition to this issue, miRNA strand usage conduces to increased cell signaling pathways modulation diversifying cellular processes regulation. In cervical cancer, 20 miRNA families are involved in carcinogenesis induction and development to this moment. These families have 5p and 3p strands with different nucleotide (nt) chain sizes. In general, mature 5p strands are larger: two miRNAs of 24 nt, 24 miRNAs of 23 nt, 35 miRNAs of 22 nt and three miRNAs of 21 nt. On the other hand, the 3p strands lengths observed are: seven miRNAs of 23 nt, 50 miRNAs of 22 nt, six miRNAs of 21 nt and four miRNAs of 20 nt. Based on the analysis of the 20 miRNA families associated with cervical cancer, 67 3p strands and 65 5p strands are selected suggesting selectivity and specificity mechanisms regulating cell processes like proliferation, apoptosis, migration, invasion, metabolism and Warburg effect. The insight reviewed here could be used in the miRNA based therapy, diagnosis and prognosis approaches.