Roles of DDX5 in the tumorigenesis, proliferation, differentiation, metastasis and pathway regulation of human malignancies

RNA Helicase DDX5 Maintains Cardiac Function by Regulating CamkIIδ Alternative Splicing

BACKGROUND

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. RNA-binding proteins are identified as regulators of cardiac disease; DDX5 (dead-box helicase 5) is a master regulator of many RNA processes, although its function in heart physiology remains unclear.

METHODS

We assessed DDX5 expression in human failing hearts and a mouse HF model. To study the function of DDX5 in heart, we engineered cardiomyocyte-specific Ddx5 knockout mice. We overexpressed DDX5 in cardiomyocytes using adeno-associated virus serotype 9 and performed transverse aortic constriction to establish the murine HF model. The mechanisms underlined were subsequently investigated using immunoprecipitation-mass spectrometry, RNA-sequencing, alternative splicing analysis, and RNA immunoprecipitation sequencing.

RESULTS

We screened transcriptome databases of murine HF and human dilated cardiomyopathy samples and found that DDX5 was significantly downregulated in both. Cardiomyocyte-specific deletion of Ddx5 resulted in HF with reduced cardiac function, an enlarged heart chamber, and increased fibrosis in mice. DDX5 overexpression improved cardiac function and protected against adverse cardiac remodeling in mice with transverse aortic constriction-induced HF. Furthermore, proteomics revealed that DDX5 is involved in RNA splicing in cardiomyocytes. We found that DDX5 regulated the aberrant splicing of Ca2+/calmodulin-dependent protein kinase IIδ (CamkIIδ), thus preventing the production of CaMKIIδA, which phosphorylates L-type calcium channel by serine residues of Cacna1c, leading to impaired Ca2+ homeostasis. In line with this, we found increased intracellular Ca2+ transients and increased sarcoplasmic reticulum Ca2+ content in DDX5-depleted cardiomyocytes. Using adeno-associated virus serotype 9 knockdown of CaMKIIδA partially rescued the cardiac dysfunction and HF in Ddx5 knockout mice.

CONCLUSIONS

These findings reveal a role for DDX5 in maintaining calcium homeostasis and cardiac function by regulating alternative splicing in cardiomyocytes, identifying the DDX5 as a potential target for therapeutic intervention in HF.

DDX5 promotes esophageal squamous cell carcinoma growth through sustaining VAV3 mRNA stability

Novel therapeutic targets and their inhibitors for esophageal squamous cell carcinoma (ESCC) prevention and therapy are urgently needed. This study aimed to investigate the function of DEAD-box helicase 5 (DDX5) in ESCC progression and to identify a promising inhibitor of DDX5. We verified that DDX5 was highly expressed in ESCC and played an oncogenic role, binding with vav guanine nucleotide exchange factor 3 (VAV3) mRNA and facilitating VAV3 mRNA N6-methyladenosine (m6A) modification by interacting with the m6A methyltransferase 3 (METTL3). M6A-modified VAV3 mRNA was identified by insulin-like growth factor 1 (IGF2BP1), increasing mRNA stability. Methylnissolin-3-β-D-O-glucoside (MD) inhibited ESCC progression through the DDX5-VAV3 axis. Our findings suggest that DDX5 promotes ESCC progression. MD inhibits ESCC progression by targeting DDX5.

Circular RNA IGF1R Promotes Cardiac Repair via Activating β-Catenin Signaling by Interacting with DDX5 in Mice after Ischemic Insults

The potential of circular RNAs (circRNAs) as biomarkers and therapeutic targets is becoming increasingly evident, yet their roles in cardiac regeneration and myocardial renewal remain largely unexplored. Here, we investigated the function of circIGF1R and related mechanisms in cardiac regeneration. Through analysis of circRNA sequencing data from neonatal and adult cardiomyocytes, circRNAs associated with regeneration were identified. Our data showed that circIGF1R expression was high in neonatal hearts, decreased with postnatal maturation, and up-regulated after cardiac injury. The elevation was validated in patients diagnosed with acute myocardial infarction (MI) within 1 week. In human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and myocardial tissue from mice after apical resection and MI, we observed that circIGF1R overexpression enhanced cardiomyocyte proliferation, reduced apoptosis, and mitigated cardiac dysfunction and fibrosis, while circIGF1R knockdown impeded endogenous cardiac renewal. Mechanistically, we identified circIGF1R binding proteins through circRNA precipitation followed by mass spectrometry. RNA pull-down Western blot and RNA immunoprecipitation demonstrated that circIGF1R directly interacted with DDX5 and augmented its protein level by suppressing ubiquitin-dependent degradation. This subsequently triggered the β-catenin signaling pathway, leading to the transcriptional activation of cyclin D1 and c-Myc. The roles of circIGF1R and DDX5 in cardiac regeneration were further substantiated through site-directed mutagenesis and rescue experiments. In conclusion, our study highlights the pivotal role of circIGF1R in facilitating heart regeneration and repair after ischemic insults. The circIGF1R/DDX5/β-catenin axis emerges as a novel therapeutic target for enhancing myocardial repair after MI, offering promising avenues for the development of regenerative therapies.

METTL1-modulated LSM14A facilitates proliferation and migration in glioblastoma via the stabilization of DDX5

Glioblastoma (GBM) is characterized by aggressive growth, invasiveness, and poor prognosis. Elucidating the molecular mechanisms underlying GBM is crucial. This study explores the role of Sm-like protein 14 homolog A (LSM14A) in GBM. Bioinformatics and clinical tissue samples analysis demonstrated that overexpression of LSM14A in GBM correlates with poorer prognosis. CCK8, EdU, colony formation, and transwell assays revealed that LSM14A promotes proliferation, migration, and invasion in GBM in vitro. In vivo mouse xenograft models confirmed the results of the in vitro experiments. The mechanism of LSM14A modulating GBM cell proliferation was investigated using mass spectrometry, co-immunoprecipitation (coIP), protein half-life, and methylated RNA immunoprecipitation (MeRIP) analyses. The findings indicate that during the G1/S phase, LSM14A stabilizes DDX5 in the cytoplasm, regulating CDK4 and P21 levels. Furthermore, METTL1 modulates LSM14A expression via mRNA m7G methylation. Altogether, our work highlights the METTL1-LSM14A-DDX5 pathway as a potential therapeutic target in GBM.

ZBTB16 inhibits DNA replication and induces cell cycle arrest by targeting WDHD1 transcription in lung adenocarcinoma

Lung adenocarcinoma is a malignant tumor with high morbidity and mortality. ZBTB16 plays a double role in various tumors; however, the potential mechanism of ZBTB16 in the pathophysiology of lung adenocarcinoma has yet to be elucidated. We herein observed a decreased expression of ZBTB16 mRNA and protein in lung adenocarcinoma and a significantly increased DNA methylation level of ZBTB16 in patients with lung adenocarcinoma. Analysis of public databases and patients' clinical data indicated a close association between ZBTB16 and patient survival. Ectopic expression of ZBTB16 in lung adenocarcinoma cells significantly inhibited cell proliferation, invasion, and migration. It also induced cell cycle arrest in the S phase. Meanwhile, mitotic catastrophe was induced, and DNA damage and apoptosis occurred. In line with these findings, the overexpression of ZBTB16 in xenograft mice resulted in the inhibition of tumor growth. Comprehensive analysis showed that WDHD1 was a potential target for ZBTB16. The overexpression of both isoforms of WDHD1 significantly reversed the ZBTB16-mediated inhibition of lung adenocarcinoma proliferation and cell cycle. These studies suggest that ZBTB16 impedes the progression of lung adenocarcinoma by interfering with WDHD1 transcription, making it a potential novel therapeutic target in the management of lung adenocarcinoma.

APLN promotes the proliferation, migration, and glycolysis of cervical cancer through the PI3K/AKT/mTOR pathway

Apelin (APLN) is an endogenous ligand of the G protein-coupled receptor APJ (APLNR). APLN has been implicated in the development of multiple tumours. Herein, we determined the effect of APLN on the biological behaviour and underlying mechanisms of cervical cancer. The expression and survival curves of APLN were determined using Gene Expression Profiling Interactive Analysis. The cellular functions of APLN were detected using CCK-8, clone formation, EdU, Transwell assays, flow cytometry, and seahorse metabolic analysis. The underlying mechanisms were elucidated using gene set enrichment analysis and Western blotting. APLN was upregulated in the samples of patients with cervical cancer and is associated with poor prognosis. APLN knockdown decreased the proliferation, migration, and glycolysis of cervical cancer cells. The opposite results were observed when APLN was overexpressed. Mechanistically, we determined that APLN was critical for activating the PI3K/AKT/mTOR pathway via APLNR. APLN receptor inhibitor ML221 reversed the effect of APLN overexpression on cervical cancer cells. Treatment with LY294002, the PI3K inhibitor, drastically reversed the oncological behaviour of APLN-overexpressing C-33A cells. APLN promoted the proliferation, migration, and glycolysis of cervical cancer cells via the PI3K/AKT/mTOR pathway.

Ddx5 Targeted Epigenetic Modification of Pericytes in Pulmonary Hypertension After Intrauterine Growth Restriction

Newborns with intrauterine growth restriction (IUGR) have a higher likelihood of developing pulmonary arterial hypertension (PAH) in adulthood. Although there is increasing evidence suggesting that pericytes play a role in regulating myofibroblast transdifferentiation and angiogenesis in malignant and cardiovascular diseases, their involvement in the pathogenesis of IUGR-related pulmonary hypertension and the underlying mechanisms remain incompletely understood. To address this issue, a study was conducted using a Sprague-Dawley rat model of IUGR-related pulmonary hypertension. Our investigation revealed increased proliferation and migration of pulmonary microvascular pericytes in IUGR-related pulmonary hypertension, accompanied by weakened endothelial-pericyte interactions. Through whole-transcriptome sequencing, Ddx5 (DEAD-box protein 5) was identified as one of the hub genes in pericytes. DDX5, a member of the RNA helicase family, plays a role in the regulation of ATP-dependent RNA helicase activities and cellular function. MicroRNAs have been implicated in the pathogenesis of PAH, and microRNA-205 (miR-205) regulates cell proliferation, migration, and angiogenesis. The results of dual-luciferase reporter assays confirmed the specific binding of miR-205 to Ddx5. Mechanistically, miR-205 negatively regulates Ddx5, leading to the degradation of β-catenin by inhibiting the phosphorylation of Gsk3β at serine 9. In vitro experiments showed the addition of miR-205 effectively ameliorated pericyte dysfunction. Furthermore, in vivo experiments demonstrated that miR-205 agomir could ameliorate pulmonary hypertension. Our findings indicated that the downregulation of miR-205 expression mediates pericyte dysfunction through the activation of Ddx5. Therefore, targeting the miR-205/Ddx5/p-Gsk3β/β-catenin axis could be a promising therapeutic approach for IUGR-related pulmonary hypertension.

DDX5 inhibits hyaline cartilage fibrosis and degradation in osteoarthritis via alternative splicing and G-quadruplex unwinding

Hyaline cartilage fibrosis is typically considered an end-stage pathology of osteoarthritis (OA), which results in changes to the extracellular matrix. However, the mechanism behind this is largely unclear. Here, we found that the RNA helicase DDX5 was dramatically downregulated during the progression of OA. DDX5 deficiency increased fibrosis phenotype by upregulating COL1 expression and downregulating COL2 expression. In addition, loss of DDX5 aggravated cartilage degradation by inducing the production of cartilage-degrading enzymes. Chondrocyte-specific deletion of Ddx5 led to more severe cartilage lesions in the mouse OA model. Mechanistically, weakened DDX5 resulted in abundance of the Fn1-AS-WT and Plod2-AS-WT transcripts, which promoted expression of fibrosis-related genes (Col1, Acta2) and extracellular matrix degradation genes (Mmp13, Nos2 and so on), respectively. Additionally, loss of DDX5 prevented the unfolding Col2 promoter G-quadruplex, thereby reducing COL2 production. Together, our data suggest that strategies aimed at the upregulation of DDX5 hold significant potential for the treatment of cartilage fibrosis and degradation in OA.

FL118 Is a Potent Therapeutic Agent against Chronic Myeloid Leukemia Resistant to BCR-ABL Inhibitors through Targeting RNA Helicase DDX5

Chronic myeloid leukemia (CML) is induced by the expression of the fused tyrosine kinase BCR-ABL, which is caused by a chromosomal translocation. BCR-ABL inhibitors have been used to treat CML; however, the acquisition of resistance by CML cells during treatment is a serious issue. We herein demonstrated that BCR-ABL induced the expression of the RNA helicase DDX5 in K562 cells derived from CML patients in a manner that was dependent on its kinase activity, which resulted in cell proliferation and survival. The knockout of DDX5 decreased the expression of BIRC5 (survivin) and activated caspase 3, leading to apoptosis in K562 cells. Similar results were obtained in cells treated with FL118, an inhibitor of DDX5 and a derivative compound of camptothecin (CPT). Furthermore, FL118 potently induced apoptosis not only in Ba/F3 cells expressing BCR-ABL, but also in those expressing the BCR-ABL T315I mutant, which is resistant to BCR-ABL inhibitors. Collectively, these results revealed that DDX5 is a critical therapeutic target in CML and that FL118 is an effective candidate compound for the treatment of BCR-ABL inhibitor-resistant CML.

A review of nuclear Dbf2-related kinase 1 (NDR1) protein interaction as promising new target for cancer therapy

Nuclear Dbf2-related kinase 1 (NDR1) is a nuclear Dbf2-related (NDR) protein kinase family member, which regulates cell functions and participates in cell proliferation and differentiation through kinase activity. NDR1 regulates physiological functions by interacting with different proteins. Protein-protein interactions (PPIs) are crucial for regulating biological processes and controlling cell fate, and as a result, it is beneficial to study the actions of PPIs to elucidate the pathological mechanism of diseases. The previous studies also show that the expression of NDR1 is deregulated in numerous human cancer samples and it needs the context-specific targeting strategies for NDR1. Thus, a comprehensive understanding of the direct interaction between NDR1 and varieties of proteins may provide new insights into cancer therapies. In this review, we summarize recent studies of NDR1 in solid tumors, such as prostate cancer and breast cancer, and explore the mechanism of action of PPIs of NDR1 in tumors.

DDX5 inhibits inflammation by modulating m6A levels of TLR2/4 transcripts during bacterial infection

DExD/H-box helicases are crucial regulators of RNA metabolism and antiviral innate immune responses; however, their role in bacteria-induced inflammation remains unclear. Here, we report that DDX5 interacts with METTL3 and METTL14 to form an m6A writing complex, which adds N6-methyladenosine to transcripts of toll-like receptor (TLR) 2 and TLR4, promoting their decay via YTHDF2-mediated RNA degradation, resulting in reduced expression of TLR2/4. Upon bacterial infection, DDX5 is recruited to Hrd1 at the endoplasmic reticulum in an MyD88-dependent manner and is degraded by the ubiquitin-proteasome pathway. This process disrupts the DDX5 m6A writing complex and halts m6A modification as well as degradation of TLR2/4 mRNAs, thereby promoting the expression of TLR2 and TLR4 and downstream NF-κB activation. The role of DDX5 in regulating inflammation is also validated in vivo, as DDX5- and METTL3-KO mice exhibit enhanced expression of inflammatory cytokines. Our findings show that DDX5 acts as a molecular switch to regulate inflammation during bacterial infection and shed light on mechanisms of quiescent inflammation during homeostasis.

VAMP8 suppresses the metastasis via DDX5/β-catenin signal pathway in osteosarcoma

Osteosarcoma is a highly metastatic malignant bone tumor, necessitating the development of new treatments to target its metastasis. Recent studies have revealed the significance of VAMP8 in regulating various signaling pathways in various types of cancer. However, the specific functional role of VAMP8 in osteosarcoma progression remains unclear. In this study, we observed a significant downregulation of VAMP8 in osteosarcoma cells and tissues. Low levels of VAMP8 in osteosarcoma tissues were associated with patients' poor prognosis. VAMP8 inhibited the migration and invasion capability of osteosarcoma cells. Mechanically, we identified DDX5 as a novel interacting partner of VAMP8, and the conjunction of VAMP8 and DDX5 promoted the degradation of DDX5 via the ubiquitin-proteasome system. Moreover, reduced levels of DDX5 led to the downregulation of β-catenin, thereby suppressing the epithelial-mesenchymal transition (EMT). Additionally, VAMP8 promoted autophagy flux, which may contribute to the suppression of osteosarcoma metastasis. In conclusion, our study anticipated that VAMP8 inhibits osteosarcoma metastasis by promoting the proteasomal degradation of DDX5, consequently inhibiting WNT/β-catenin signaling and EMT. Dysregulation of autophagy by VAMP8 is also implicated as a potential mechanism. These findings provide new insights into the biological nature driving osteosarcoma metastasis and highlight the modulation of VAMP8 as a potential therapeutic strategy for targeting osteosarcoma metastasis.

DDX5 Functions as a Tumor Suppressor in Tongue Cancer

DEAD-box polypeptide 5 (DDX5), a DEAD-box RNA helicase, is a multifunctional protein that plays important roles in many physiological and pathological processes. Contrary to its documented oncogenic role in a wide array of cancers, we herein demonstrate that DDX5 serves as a tumor suppressor in tongue cancer. The high expression of DDX5 is correlated with better prognosis for clinical tongue cancer patients. DDX5 downregulates the genes associated with tongue cancer progression. The knockdown of DDX5 promotes, while the overexpression of DDX5 inhibits, tongue cancer proliferation, development, and cisplatin resistance. Furthermore, the expression of DDX5 in tongue cancer is associated with immune cell infiltration in the tumor microenvironment. Specifically, the expression of DDX5 is associated with the reduced infiltration of M2 macrophages and increased infiltration of T cell clusters, which may contribute to anticancer effects in the tumor microenvironment. In this study, we establish DDX5 as a valuable prognostic biomarker and an important tumor suppressor in tongue cancer.

Single-cell transcriptomics uncover hub genes and cell-cell crosstalk in patients with hypertensive nephropathy

Hypertensive nephropathy (HTN) is one of the leading causes of end-stage renal disease, yet the molecular mechanisms are still unknown. To explore novel mechanisms and gene targets for HTN, the gene expression profiles of renal biopsy samples obtained from 2 healthy living donor controls and 5 HTN patients were determined by single-cell RNA sequencing. Key hub genes expression were validated by the Nephroseq v5 platform. The HTN endothelium upregulated cellular adhesion genes (ICAM2 and CEACAM1), inflammatory genes (ETS2 and IFI6) and apoptosis related genes (CNN3). Proximal tubules in HTN highly expressed hub genes including BBOX1, TPM1, TMSB10, SDC4, and NUP58, which might be potential novel targets for proximal tubular injury. The upregulated genes in tubules of HTN were mainly participating in inflammatory signatures including IFN-γ signature, NF-κB signaling, IL-12 signaling and Wnt signaling pathway. Receptor-ligand interaction analysis indicated potential cell-cell crosstalk between endothelial cells or mesangial cells with other renal resident cells in HTN. Together, our data identify a distinct cell-specific gene expression profile, pathogenic inflammatory signaling and potential cell-cell communications between endothelial cells or mesangial cells with other renal resident cells in HTN. These findings may provide a promising novel landscape for mechanisms and treatment of human HTN.

AURKAIP1 actuates tumor progression through stabilizing DDX5 in triple negative breast cancer

Aurora-A kinase interacting protein 1 (AURKAIP1) has been proved to take an intermediary role in cancer by functioning as a negative regulator of Aurora-A kinase. However, it remains unclear whether and how AURKAIP1 itself would directly engage in regulating malignancies. The expression levels of AURKAIP1 were detected in triple negative breast cancer (TNBC) by immunohistochemistry and western blots. The CCK8, colony formation assays and nude mouse model were conducted to determine cell proliferation whereas transwell and wound healing assays were performed to observe cell migration. The interaction of AURKAIP1 and DEAD-box helicase 5 (DDX5) were verified through co-immunoprecipitation and successively western blots. From the results, we found that AURKAIP1 was explicitly upregulated in TNBC, which was positively associated with tumor size, lymph node metastases, pathological stage and unfavorable prognosis. AURKAIP1 silencing markedly inhibited TNBC cell proliferation and migration in vitro and in vivo. AURKAIP1 directly interacted with and stabilized DDX5 protein by preventing ubiquitination and degradation, and DDX5 overexpression successfully reversed proliferation inhibition induced by knockdown of AURKAIP1. Consequently, AURKAIP1 silencing suppressed the activity of Wnt/β-catenin signaling in a DDX5-dependent manner. Our study may primarily disclose the molecular mechanism by which AURKAIP1/DDX5/β-catenin axis modulated TNBC progression, indicating that AURKAIP1 might serve as a therapeutic target as well as a TNBC-specific biomarker for prognosis.

GPR56 signaling pathway network and its dynamics in the mesenchymal transition of glioblastoma

G protein-coupled receptor 56 (GPR56/ADGRG1) is a multifunctional adhesion GPCR involved in diverse biological processes ranging from development to cancer. In our earlier study, we reported that GPR56 is expressed heterogeneously in glioblastoma (GBM) and is involved in the mesenchymal transition, making it a promising therapeutic target (Ganesh et al., 2022). Despite its important role in cancer, its mechanism of action or signaling is not completely understood. Thus, based on transcriptomic, proteomic, and phosphoproteomic differential expression data of GPR56 knockdown U373-GBM cells included in our above study along with detailed literature mining of the molecular events plausibly associated with GPR56 activity, we have constructed a signaling pathway map of GPR56 as may be applicable in mesenchymal transition in GBM. The map incorporates more than 100 molecular entities including kinases, receptors, ion channels, and others associated with Wnt, integrin, calcium signaling, growth factors, and inflammation signaling pathways. We also considered intracellular and extracellular factors that may influence the activity of the pathway entities. Here we present a curated signaling map of GPR56 in the context of GBM and discuss the relevance and plausible cross-connectivity across different axes attributable to GPR56 function. GPR56 signaling and mesenchymal transition.

Non-classical circulating monocytes expressing high levels of microsomal prostaglandin E2 synthase-1 tag an aberrant IFN-response in systemic sclerosis

Systemic sclerosis (SSc) is a complex disease that affects the connective tissue, causing fibrosis. SSc patients show altered immune cell composition and activation in the peripheral blood (PB). PB monocytes (Mos) are recruited into tissues where they differentiate into macrophages, which are directly involved in fibrosis. To understand the role of CD14+ PB Mos in SSc, a single-cell transcriptome analysis (scRNA-seq) was conducted on 8 SSc patients and 8 controls. Using unsupervised clustering methods, CD14+ cells were assigned to 11 clusters, which added granularity to the known monocyte subsets: classical (cMos), intermediate (iMos) and non-classical Mos (ncMos) or type 2 dendritic cells. NcMos were significantly overrepresented in SSc patients and showed an active IFN-signature and increased expression levels of PTGES, in addition to monocyte motility and adhesion markers. We identified a SSc-related cluster of IRF7+ STAT1+ iMos with an aberrant IFN-response. Finally, a depletion of M2 polarised cMos in SSc was observed. Our results highlighted the potential of PB Mos as biomarkers for SSc and provided new possibilities for putative drug targets for modulating the innate immune response in SSc.

RNA helicase DExD/H-box 5 modulates intestinal microbiota in mice

The RNA helicase DExD/H-box (DDX) family of proteins plays a central role in host cellular RNA metabolism, including mRNA regulation, microRNA biogenesis, and ribosomal processing. DDX5, also known as p68, promotes viral replication and tumorigenesis. However, there have been no studies on the regulation of the intestinal microbiota by DDX family proteins. We constructed DDX5 knockout mice (Ddx5+/-) using CRISPR/CAS9 technology. Subsequently, DDX5 knockout mice were analyzed for PCR products, mRNA levels, protein expression, immunohistochemistry, and histopathological lesions. Fecal (n = 12) and ileum (n = 12) samples were collected from the Ddx5+/- and wild-type (Ddx5+/+) mice. The diversity, richness, and structural separation of the intestinal microbiota of the Ddx5+/- and Ddx5+/+ mice were determined by 16S rRNA sequencing and analysis. Ddx5+/- mice were successfully established, and the ileum had normal morphology, a clear layer of tissue structures, and neatly arranged cupped cells. DDX5 knockout mice did not exhibit adverse effects on the ileal tissue. Microbial diversity and abundance were not significantly different, but the microbial structure of the intestinal microbiota was clustered separately between Ddx5+/+ and Ddx5+/- mice. Furthermore, we found that the relative abundance of Akkermansia and Clostridium_sensu_stricto_1 in the Ddx5+/- mice was significantly lower than in the Ddx5+/+ mice. These analyses indicated specific interactions between the intestinal microbiota and DDX5 protein. Our results indicate that DDX5 has a significant effect on the composition of the intestinal microbiota in mice, suggesting its potential as a promising novel target for the treatment of inflammation and tumorigenesis in the intestine.

Participation of ATM, SMG1, and DDX5 in a DNA Damage-Induced Alternative Splicing Pathway

Altered cellular responses to DNA damage can contribute to cancer development, progression, and therapeutic resistance. Mutations in key DNA damage response factors occur across many cancer types, and the DNA damage-responsive gene, TP53, is frequently mutated in a high percentage of cancers. We recently reported that an alternative splicing pathway induced by DNA damage regulates alternative splicing of TP53 RNA and further modulates cellular stress responses. Through damage-induced inhibition of the SMG1 kinase, TP53 pre-mRNA is alternatively spliced to generate TP53b mRNA and p53b protein is required for optimal induction of cellular senescence after ionizing radiation-induced DNA damage. Herein, we confirmed and extended these observations by demonstrating that the ATM protein kinase is required for repression of SMG1 kinase activity after ionizing radiation. We found that the RNA helicase and splicing factor, DDX5, interacts with SMG1, is required for alternative splicing of TP53 pre-mRNA to TP53b and TP53c mRNAs after DNA damage, and contributes to radiation-induced cellular senescence. Interestingly, the role of SMG1 in alternative splicing of p53 appears to be distinguishable from its role in regulating nonsense-mediated RNA decay. Thus, ATM, SMG1, and DDX5 participate in a DNA damage-induced alternative splicing pathway that regulates TP53 splicing and modulates radiation-induced cellular senescence.

MSC-derived extracellular vesicles as nanotherapeutics for promoting aged liver regeneration

Aging is one of the critical factors to impair liver regeneration leading to a high incidence of severe complications after hepatic surgery in the elderly population without any effective treatment for clinical administration. As cell-free nanotherapeutics, mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have been demonstrated the therapeutic potentials on liver diseases. However, the effects of MSC-EVs on the proliferation of aged hepatocytes are largely unclear. In this study, we found MSCs could reduce the expression of senescence-associated markers in the liver and stimulate its regeneration in aged mice after receiving a two-thirds partial hepatectomy (PHx) through their secreted MSC-EVs. Using RNA-Seq and AAV9 vector, we mechanistically found that these effects of UC-MSC-EVs partially attributed to inducing Atg4B-related mitophagy. This effect repairs the mitochondrial status and functions of aged hepatocytes to promote their proliferation. And protein mass spectrum analysis uncovered that DEAD-Box Helicase 5 (DDX5) enriches in UC-MSC-EVs, which interacts with E2F1 to facilitate its nuclear translocation for activating the expression of Atg4B. Collectively, our data show that MSC-EVs act nanotherapeutic potentials in anti-senescence and promoting regeneration of aged liver by transferring DDX5 to regulate E2F1-Atg4B signaling pathway that induce mitophagy, which highlights the clinical application valuation of MSC-EVs for preventing severe complications in aged population receiving liver surgery.

DDX5 mRNA-targeting antisense oligonucleotide as a new promising therapeutic in combating castration-resistant prostate cancer

The heat shock protein 27 (Hsp27) has emerged as a principal factor of the castration-resistant prostate cancer (CRPC) progression. Also, an antisense oligonucleotide (ASO) against Hsp27 (OGX-427 or apatorsen) has been assessed in different clinical trials. Here, we illustrate that Hsp27 highly regulates the expression of the human DEAD-box protein 5 (DDX5), and we define DDX5 as a novel therapeutic target for CRPC treatment. DDX5 overexpression is strongly correlated with aggressive tumor features, notably with CRPC. DDX5 downregulation using a specific ASO-based inhibitor that acts on DDX5 mRNAs inhibits cell proliferation in preclinical models, and it particularly restores the treatment sensitivity of CRPC. Interestingly, through the identification and analysis of DDX5 protein interaction networks, we have identified some specific functions of DDX5 in CRPC that could contribute actively to tumor progression and therapeutic resistance. We first present the interactions of DDX5 and the Ku70/80 heterodimer and the transcription factor IIH, thereby uncovering DDX5 roles in different DNA repair pathways. Collectively, our study highlights critical functions of DDX5 contributing to CRPC progression and provides preclinical proof of concept that a combination of ASO-directed DDX5 inhibition with a DNA damage-inducing therapy can serve as a highly potential novel strategy to treat CRPC.

Splicing factor SRSF3 promotes the progression of cervical cancer through regulating DDX5

Aberrant alternative splicing (AS) profoundly affects tumorigenesis and cancer progression. Serine/arginine-rich splicing factor 3 (SRSF3) regulates the AS of precursor mRNAs and acts as a proto-oncogene in many tumors, but its function and potential mechanisms in cervical cancer remain unclear. Here, we found that SRSF3 was highly expressed in cervical cancer tissues and that SRSF3 expression was correlated with prognosis after analyses of the The Cancer Genome Atlas and GEO databases. Furthermore, knockdown of SRSF3 reduced the proliferation, migration, and invasion abilities of HeLa cells, while overexpression of SRSF3 promoted proliferation, migration, and invasion of CaSki cells. Further studies showed that SRSF3 mediated the variable splicing of exon 12 of the transcriptional cofactor DEAD-box helicase 5 (DDX5). Specifically, overexpression of SRSF3 promoted the production of the pro-oncogenic spliceosome DDX5-L and repressed the production of the repressive spliceosome DDX5-S. Ultimately, both SRSF3 and DDX5-L were able to upregulate oncogenic AKT expression, while DDX5-S downregulated AKT expression. In conclusion, we found that SRSF3 increased the production of DDX5-L and decreased the production of DDX5-S by regulating the variable splicing of DDX5. This, in turn promoted the proliferation, migration, and invasion of cervical cancer by upregulating the expression level of AKT. These results reveal the oncogenic role of SRSF3 in cervical cancer and emphasize the importance of the SRSF3-DDX5-AKT axis in tumorigenesis. SRSF3 and DDX5 are new potential biomarkers and therapeutic targets for cervical cancer.

HNRNPU promotes the progression of triple-negative breast cancer via RNA transcription and alternative splicing mechanisms

Triple-negative breast cancer (TNBC) is a great detriment to women's health due to the lack of effective therapeutic targets. In this study, we employed an integrated genetic screen to identify a pivotal oncogenic factor, heterogeneous nuclear ribonucleoprotein U (HNRNPU), which is required for the progression of TNBC. We elucidated the pro-oncogenic role of HNRNPU, which can induce the proliferation and migration of TNBC cells via its association with DEAD box helicase 5 (DDX5) protein. Elevated levels of the HNRNPU-DDX5 complex prohibited the intron retention of minichromosome maintenance protein 10 (MCM10) pre-mRNA, decreased nonsense-mediated mRNA decay, and activated Wnt/β-catenin signalling; on the other hand, HNRNPU-DDX5 is located in the transcriptional start sites (TSS) of LIM domain only protein 4 (LMO4) and its upregulation promoted the transcription of LMO4, consequently activating PI3K-Akt-mTOR signalling. Our data highlight the synergetic effects of HNRNPU in RNA transcription and splicing in regulating cancer progression and suggest that HNRNPU may act as a potential molecular target in the treatment of TNBC.

Pan-cancer analysis of the prognostic and immunological roles of DEAD-box helicase 5 (DDX5) in human tumors

Background: Recent studies have demonstrated the significance of the DEAD-box helicase 5 (DDX5) gene, which is involved in pathways concerning the modification of RNA structures. DDX5 functions as a coregulator of cellular transcription and splicing, and participates in the processing of small noncoding RNAs. The aberrant regulation of DDX5 expression possibly plays a significant role in the genesis of cancer. However, there are no comprehensive pan-cancer studies on DDX5. This study is the first to conduct a pan-cancer analysis of DDX5 for aiding the diagnosis and treatment of cancer.

Methods: The gene expression, genetic alterations, protein phosphorylation, promoter methylation, immune infiltration, and enrichment analyses of DDX5 were performed using data retrieved from The Cancer Genome Atlas (TCGA), Genotype-tissue Expression (GTEx), Human Protein Atlas (HPA), Tumor Immunological Estimation Resource 2.0 (TIMER2.0), Gene Expression Profiling Interactive Analysis (GEPIA), DNA methylation interactive visualization database (DNMIVD), and Search Tool for the Retrieval of Interaction Genes/Proteins (STRING). Data analyses were performed with the R software and other webtools.

Results: The expression of DDX5 mRNA decreased significantly in 17 cancer types, but increased significantly in eight cancer types. The enhanced expression of DDX5 mRNA in the tumor samples was related to decreased overall survival (OS), progression-free interval (PFI), and disease-specific survival (DSS) in three cancers, but increased OS, PFI, and DSS in other cancers. The DNA promoter methylation level was significantly reduced in eight cancer types, and there were exceptions in the methylation levels of the DDX5 promoter in four cancer types. The expression of DDX5 mRNA was highly correlated with the infiltration of CD8+ T cells, cancer-associated fibroblasts, and B cells in a wide variety of malignancies. The findings revealed a strong association between DDX5 and its co-expressed genes in numerous cancer types. Enrichment analysis suggested that DDX5 was associated with multiple cellular pathways, including RNA splicing, Notch signaling pathway, and viral carcinogenesis, which was consistent with the results of previous studies.

Conclusion: The findings obtained herein provide further information on the oncogenic potential of DDX5 in diverse tumor types. We propose that DDX5 has important roles in tumor immunity and the diagnosis of cancer.

NAP1L1 promotes the growth of colon cancer by activating HDGF/DDX5

Colon cancer is a common malignant tumor. However, its pathogenesis still needs further study. In this study, we explored the role of nucleosome assembly protein 1-like 1 (NAP1L1) in colon cancer and its underlying mechanism. Based on analysis of The Cancer Genome Atlas data, we found that NAP1L1 is augmented in colorectal cancer, and the elevated NAP1L1 expression is associated with a poor prognosis in patients with colon cancer. Immunohistochemistry staining results showed that upregulated NAP1L1 protein level is an unfavorable factor that stimulates colon cancer progression. To further investigate the role of NAP1L1 in colon cancer, we established a colon cancer cell line with NAP1L1 knockdown, and found that repressing NAP1L1 expression in colon cancer cells markedly reduces cell proliferation in vivo and in vitro by MTT assay, colony formation, EdU incorporation, and subcutaneous tumorigenesis in nude mice. Furthermore, we found that NAP1L1 binds to HDGF, recruits DDX5, and induces β-catenin/CCND1 signaling, which promotes colon cancer cell proliferation. Finally, transfection with HDGF or DDX5restores cell growth in NAP1L1-knockdown colon cancer cells by upregulating DDX5/β-catenin/CCND1 signaling. Our study demonstrates that NAP1L1 functions as a potential oncogene that promotes colon cancer tumorigenesis by binding to HDGF, which stimulates DDX5/β-catenin/CCND1 signaling.

The RNA helicase DDX5 cooperates with EHMT2 to sustain alveolar rhabdomyosarcoma growth

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of childhood characterized by the inability to exit the proliferative myoblast-like stage. The alveolar fusion positive subtype (FP-RMS) is the most aggressive and is mainly caused by the expression of PAX3/7-FOXO1 oncoproteins, which are challenging pharmacological targets. Here, we show that the DEAD box RNA helicase 5 (DDX5) is overexpressed in alveolar RMS cells and that its depletion and pharmacological inhibition decrease FP-RMS viability and slow tumor growth in xenograft models. Mechanistically, we provide evidence that DDX5 functions upstream of the EHMT2/AKT survival signaling pathway, by directly interacting with EHMT2 mRNA, modulating its stability and consequent protein expression. We show that EHMT2 in turns regulates PAX3-FOXO1 activity in a methylation-dependent manner, thus sustaining FP-RMS myoblastic state. Together, our findings identify another survival-promoting loop in FP-RMS and highlight DDX5 as a potential therapeutic target to arrest RMS growth.

DDX5/METTL3-METTL14/YTHDF2 Axis Regulates Replication of Influenza A Virus

DEAD-box helicase 5 (DDX5), a member of the DEAD/H-box helicases, is known to participate in all aspects of RNA metabolism. However, its regulatory effect in antiviral innate immunity during replication of influenza virus remains unclear. Herein, we found that human DDX5 promotes replication of influenza virus in A549 cells. Moreover, our results further revealed that DDX5 relies on its N terminus to interact with the nucleoprotein (NP) of influenza virus, which is independent of RNA. Of course, we also observed colocalization of DDX5 with NP in the context of transfection or infection. However, influenza virus infection had no significant effect on the protein expression and nucleocytoplasmic distribution of DDX5. Importantly, we found that DDX5 suppresses antiviral innate immunity induced by influenza virus infection. Mechanistically, DDX5 downregulated the mRNA levels of interferon beta (IFN-β), interleukin 6 (IL-6), and DHX58 via the METTL3-METTL14/YTHDF2 axis. We revealed that DDX5 bound antiviral transcripts and regulated immune responses through YTHDF2-dependent mRNA decay. Taken together, our data demonstrate that the DDX5/METTL3-METTL14/YTHDF2 axis regulates the replication of influenza A virus. IMPORTANCE The replication and transcription of influenza virus depends on the participation of many host factors in cells. Exploring the relationship between viruses and host factors will help us fully understand the characteristics and pathogenic mechanisms of influenza viruses. In this study, we showed that DDX5 interacted with the NP of influenza virus. We demonstrated that DDX5 downregulated the expression of IFN-β and IL-6 and the transcription of antiviral genes downstream from IFN-β in influenza virus-infected A549 cells. Additionally, DDX5 downregulated the mRNA levels of antiviral transcripts via the METTL3-METTL14/YTHDF2 axis. Our findings provide a novel perspective to understand the mechanism by which DDX5 regulates antiviral immunity.

DDX5: an expectable treater for viral infection- a literature review

Background and Objective

DEAD-box protein (DDX)5 plays important roles in multiple aspects of cellular processes that require modulating RNA structure. Alongside the canonical role of DDX5 in RNA metabolism, many reports have shown that DDX5 influences viral infection by directly interacting with viral proteins. However, the functional role of DDX5 in virus-associated cancers, as well as the identity of DDX5 in virus infection-associated signaling pathways, has remained largely unexplained. Here, we further explore the precise functions of DDX5 and its potential targets for antiviral treatment.

Methods

We searched the PubMed and PMC databases to identify studies on role of DDXs, especially DDX5, during various viral infection published up to May 2022.

Key Content and Findings

DDX5 functions as both a viral infection helper and inhibitor, which depends on virus type. DDXs proteins have been identified to play roles on multiple aspects covering RNA metabolism and function.

Conclusions

DDX5 influences viral pathogenesis by participating in viral replication and multiple viral infection-related signaling pathways, it also plays a double-edge sword role under different viral infection conditions. Deep investigation into the mechanism of DDX5 modulating immune response in host cells revealed that it holds highly potential usage for future antiviral therapy. We reviewed current studies to provide a comprehensive update of the role of DDX5 in viral infection.

Advances on Innate Immune Evasion by Avian Immunosuppressive Viruses

Innate immunity is not only the first line of host defense against pathogenic infection, but also the cornerstone of adaptive immune response. Upon pathogenic infection, pattern recognition receptors (PRRs) of host engage pathogen-associated molecular patterns (PAMPs) of pathogens, which initiates IFN production by activating interferon regulatory transcription factors (IRFs), nuclear factor-kappa B (NF-κB), and/or activating protein-1 (AP-1) signal transduction pathways in host cells. In order to replicate and survive, pathogens have evolved multiple strategies to evade host innate immune responses, including IFN-I signal transduction, autophagy, apoptosis, necrosis, inflammasome and/or metabolic pathways. Some avian viruses may not be highly pathogenic but they have evolved varied strategies to evade or suppress host immune response for survival, causing huge impacts on the poultry industry worldwide. In this review, we focus on the advances on innate immune evasion by several important avian immunosuppressive viruses (infectious bursal disease virus (IBDV), Marek’s disease virus (MDV), avian leukosis virus (ALV), etc.), especially their evasion of PRRs-mediated signal transduction pathways (IFN-I signal transduction pathway) and IFNAR-JAK-STAT signal pathways. A comprehensive understanding of the mechanism by which avian viruses evade or suppress host immune responses will be of help to the development of novel vaccines and therapeutic reagents for the prevention and control of infectious diseases in chickens.

FL118, acting as a 'molecular glue degrader', binds to dephosphorylates and degrades the oncoprotein DDX5 (p68) to control c-Myc, survivin and mutant Kras against colorectal and pancreatic cancer with high efficacy

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC), a difficult-to-treat cancer, is expected to become the second-largest cause of cancer-related deaths by 2030, while colorectal cancer (CRC) is the third most common cancer and the third leading cause of cancer deaths. Currently, there is no effective treatment for PDAC patients. The development of novel agents to effectively treat these cancers remains an unmet clinical need. FL118, a novel anticancer small molecule, exhibits high efficacy against cancers; however, the direct biochemical target of FL118 is unknown.

METHODS

FL118 affinity purification, mass spectrometry, Nanosep centrifugal device and isothermal titration calorimetry were used for identifying and confirming FL118 binding to DDX5/p68 and its binding affinity. Immunoprecipitation (IP), western blots, real-time reverse transcription PCR, gene silencing, overexpression (OE) and knockout (KO) were used for analysing gene/protein function and expression. Chromatin IP was used for analysing protein-DNA interactions. The 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromid assay and human PDAC/CRC cell/tumour models were used for determining PDAC/CRC cell/tumour in vitro and in vivo growth.

RESULTS

We discovered that FL118 strongly binds to dephosphorylates and degrades the DDX5 oncoprotein via the proteasome degradation pathway without decreasing DDX5 mRNA. Silencing and OE of DDX5 indicated that DDX5 is a master regulator for controlling the expression of multiple oncogenic proteins, including survivin, Mcl-1, XIAP, cIAP2, c-Myc and mutant Kras. Genetic manipulation of DDX5 in PDAC cells affects tumour growth. PDAC cells with DDX5 KO are resistant to FL118 treatment. Our human tumour animal model studies further indicated that FL118 exhibits high efficacy to eliminate human PDAC and CRC tumours that have a high expression of DDX5, while FL118 exhibits less effectiveness in PDAC and CRC tumours with low DDX5 expression.

CONCLUSION

DDX5 is a bona fide FL118 direct target and can act as a biomarker for predicting PDAC and CRC tumour sensitivity to FL118. This would greatly impact FL118 precision medicine for patients with advanced PDAC or advanced CRC in the clinic. FL118 may act as a 'molecular glue degrader' to directly glue DDX5 and ubiquitination regulators together to degrade DDX5.

Insulin-like growth factor 2 mRNA-binding protein 2-stabilized long non-coding RNA Taurine up-regulated gene 1 (TUG1) promotes cisplatin-resistance of colorectal cancer via modulating autophagy

Long non-coding RNAs (lncRNAs) have been demonstrated to influence the chemoresistance of colorectal cancer (CRC). Therefore, the study is designed to investigate the regulatory function and mechanism of Taurine up-regulated gene 1 (TUG1) in the cisplatin resistance of CRC. qRT-PCR checked the expressions of TUG1, Insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2), and miR-195-5p in CRC tissues and cells. The TUG1 or miR-195-5p overexpression model was engineered in CRC cells, followed by treatment with DDP or the autophagy inhibitor (Chloroquine, CQ). CCK8 (Cell Counting Kit-8) and the colony formation experiment monitored cell proliferation. Flow cytometry examined apoptosis, Transwell tracked migration and invasion, and Western blot ascertained the protein profiles of autophagy proteins (LC3I/LC3II and Beclin1) and the HDGF/DDX5/β-catenin pathway. Dual-luciferase gene reporter assay and RNA immunoprecipitation confirmed the binding correlation between TUG1 and miR-195-5p and between miR-195-5p and HDGF. Furthermore, in-vivo experiments in nude mice probed the function and mechanism of IGF2BP2 in CRC cell growth. The profiles of TUG1 and IGF2BP2 were elevated in CRC tissues, and IGF2BP2 enhanced TUG1's expression in CRC cells. TUG1 activated autophagy to facilitate CRC cells' resistance to DDP. TUG1 targets miR-195-5p, and miR-195-5p targets HDGF. Overexpression of miR-195-5p abated the cancer-promoting function of TUG1 and curbed the profile of the HDGF/DDX5/β-catenin axis. TUG1 stabilized by IGF2BP2 boosted CRC cell proliferation, migration, migration, and autophagy via the miR-195-5p/HDGF/DDX5/β-catenin axis, hence enhancing CRC cell's resistance to DDP.

Knockdown of DEAD-box 51 inhibits tumor growth of esophageal squamous cell carcinoma via the PI3K/AKT pathway

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is one of the most prevalent malignancies that seriously threaten people’s health worldwide. DEAD-box helicase 51 (DDX51) is a member of the DEAD-box (DDX) RNA helicase family, and drives or inhibits tumor progression in multiple cancer types.

AIM

To determine whether DDX51 affects the biological behavior of ESCC.

METHODS

The expression of DDX51 in ESCC tumor tissues and adjacent normal tissues was detected by Immunohistochemistry (IHC) analyses and quantitative PCR (qPCR). We knocked down DDX51 in ESCC cell lines by using a small interfering RNA (siRNA) transfection. The proliferation, apoptosis, and mobility of DDX51 siRNA-transfected cells were detected. The effect of DDX51 on the phosphoinositide 3-kinase (PI3K)/AKT pathway was investigated by western blot analysis. A mouse xenograft model was established to investigate the effects of DDX51 knockdown on ESCC tumor growth.

RESULTS

DDX51 exhibited high expression in ESCC tissues compared with normal tissues and represented a poor prognosis in patients with ESCC. Knockdown of DDX51 induced inhibition of ESCC cell proliferation and promoted apoptosis. Moreover, DDX51 siRNA-expressing cells also exhibited lower migration and invasion rates. Investigations into the underlying mechanisms suggested that DDX51 knockdown induced inactivation of the PI3K/AKT pathway, including decreased phosphorylation levels of phosphate and tensin homolog, PI3K, AKT, and mammalian target of rapamycin. Rescue experiments demonstrated that the AKT activator insulin-like growth factor 1 could reverse the inhibitory effects of DDX51 on ESCC malignant development. Finally, we injected DDX51 siRNA-transfected TE-1 cells into an animal model, which resulted in slower tumor growth.

CONCLUSION

Our study suggests for the first time that DDX51 promotes cancer cell proliferation by regulating the PI3K/AKT pathway; thus, DDX51 might be a therapeutic target for ESCC.

PAK5 promotes RNA helicase DDX5 sumoylation and miRNA-10b processing in a kinase-dependent manner in breast cancer

P21-activated kinase 5 (PAK5) plays an important role in tumors. However, the functional role of PAK5 in mammary tumorigenesis in vivo remains unclear. Here, we show that PAK5 deficiency represses MMTV-PyVT-driven breast tumorigenesis. DEAD-box RNA helicase 5 (DDX5) is a substrate of PAK5, which is phosphorylated on threonine 69. PAK5-mediated DDX5 phosphorylation promotes breast cancer cell proliferation and metastasis. The increased expression levels of PAK5 and phospho-DDX5 threonine 69 are associated with metastasis and poor clinical outcomes of patients. PAK5 facilitates the phosphorylation-dependent sumoylation of DDX5 to stabilize DDX5. Both the phosphorylation and sumoylation of DDX5 enhance the formation of a DDX5/Drosha/DGCR8 complex, thus promoting microRNA-10b processing. Finally, we verify decreased expression of DDX5 phosphorylation and sumoylation and mature miR-10b in PAK5-/-/MMTV-PyVT transgenic mice. Our findings provide insights into the function of PAK5 in microRNA (miRNA) biogenesis, which might be a potential therapeutic target for breast cancer.

LncPSCA in the 8q24.3 risk locus drives gastric cancer through destabilizing DDX5

Genome-wide association studies (GWAS) have identified multiple gastric cancer risk loci and several protein-coding susceptibility genes. However, the role of long-noncoding RNAs (lncRNAs) transcribed from these risk loci in gastric cancer development and progression remains to be explored. Here, we functionally characterize a lncRNA, lncPSCA, as a novel tumor suppressor whose expression is fine-regulated by a gastric cancer risk-associated genetic variant. The rs2978980 T > G change in an intronic enhancer of lncPSCA interrupts binding of transcription factor RORA, which down-regulates lncPSCA expression in an allele-specific manner. LncPSCA interacts with DDX5 and promotes DDX5 degradation through ubiquitination. Increased expression of lncPSCA results in low levels of DDX5, less RNA polymerase II (Pol II) binding with DDX5 in the nucleus, thus activating transcription of multiple p53 signaling genes by Pol II. These findings highlight the importance of functionally annotating lncRNAs in GWAS risk loci and the great potential of modulating lncRNAs as innovative cancer therapy.

Circular RNA circEGFR regulates tumor progression via the miR-106a-5p/DDX5 axis in colorectal cancer

Recently, an increasing number of studies have reported that dysregulation of circular RNA (circRNA) expression plays critical roles in the progression of several cancers, including colorectal cancer (CRC). However, the detailed molecular mechanisms of circRNAs involvement in CRC remain largely unknown. Here, we confirmed that the level of circEGFR was significantly increased in CRC tissues compared to matched adjacent non-tumor tissues, and a high level of circEGFR was correlated with poor clinicopathological characteristics and poor prognosis in patients with CRC. Moreover, increased circEGFR expression promoted CRC cell proliferation, migration, and invasion in vitro. Mechanistically, circEGFR acted as a ceRNA for miR-106a-5p to relieve the repressive effect of miR-106a-5p on DDX5 mRNA. Moreover, circEGFR enhanced DDX5 expression, thereby upregulating p-AKT levels. Together, these findings showed that circEGFR promoted CRC cell proliferation, migration, and invasion through the miR-106a-5p/DDX5/AKT axis, and may serve as a promising diagnostic marker and therapeutic target for CRC patients.

Gastric Cancer: Identification of microRNAs Inhibiting Druggable Targets and Mediating Efficacy in Preclinical In Vivo Models

In addition to chemotherapy, targeted therapies have been approved for treatment of locally advanced and metastatic gastric cancer. The therapeutic benefit is significant but more durable responses and improvement of survival should be achieved. Therefore, the identification of new targets and new approaches for clinical treatment are of paramount importance. In this review, we searched the literature for down-regulated microRNAs which interfere with druggable targets and exhibit efficacy in preclinical in vivo efficacy models. As druggable targets, we selected transmembrane receptors, secreted factors and enzymes. We identified 38 microRNAs corresponding to the criteria as outlined. A total of 13 miRs target transmembrane receptors, nine inhibit secreted proteins and 16 attenuate enzymes. These microRNAs are targets for reconstitution therapy of gastric cancer. Further target validation experiments are mandatory for all of the identified microRNAs.

DEAD-Box RNA Helicases in Cell Cycle Control and Clinical Therapy

Cell cycle is regulated through numerous signaling pathways that determine whether cells will proliferate, remain quiescent, arrest, or undergo apoptosis. Abnormal cell cycle regulation has been linked to many diseases. Thus, there is an urgent need to understand the diverse molecular mechanisms of how the cell cycle is controlled. RNA helicases constitute a large family of proteins with functions in all aspects of RNA metabolism, including unwinding or annealing of RNA molecules to regulate pre-mRNA, rRNA and miRNA processing, clamping protein complexes on RNA, or remodeling ribonucleoprotein complexes, to regulate gene expression. RNA helicases also regulate the activity of specific proteins through direct interaction. Abnormal expression of RNA helicases has been associated with different diseases, including cancer, neurological disorders, aging, and autosomal dominant polycystic kidney disease (ADPKD) via regulation of a diverse range of cellular processes such as cell proliferation, cell cycle arrest, and apoptosis. Recent studies showed that RNA helicases participate in the regulation of the cell cycle progression at each cell cycle phase, including G1-S transition, S phase, G2-M transition, mitosis, and cytokinesis. In this review, we discuss the essential roles and mechanisms of RNA helicases in the regulation of the cell cycle at different phases. For that, RNA helicases provide a rich source of targets for the development of therapeutic or prophylactic drugs. We also discuss the different targeting strategies against RNA helicases, the different types of compounds explored, the proposed inhibitory mechanisms of the compounds on specific RNA helicases, and the therapeutic potential of these compounds in the treatment of various disorders.

LncRNA SNHG14 promotes cell proliferation and invasion in colorectal cancer through modulating miR-519b-3p/DDX5 axis

Numbers of studies suggest that long non-coding RNAs (lncRNAs) exert an important role in cancer progression. It is reported that lncRNA SNHG14 (SNHG14) promotes cell proliferation and invasion in many cancers. However, the underlying molecular mechanism of SNHG14 in colorectal cancer (CRC) remains unclear. In our study, we found that SNHG14 is highly expressed in CRC tissues and cells, especially in SW480 and HT-29 cells. In addition, sh-SNHG14 inhibits cell proliferation, cell migration and invasion, promotes cell apoptosis in CRC cell lines. Furthermore, we found that SNHG14 functions as a sponge for miR-519b-3p, while the DEAD box protein 5 (DDX5) is a downstream target gene of miR-519b-3p, and the functions of miR-519b-3p inhibitors on the CRC progression could be rescued by downregulation of DDX5. Our findings suggest that SNHG14 promotes the CRC progression by miR-519b-3p/DDX5 axis, implying the promising therapeutic target of SNHG4 for CRC patients.

DEAD/DEAH-box helicase 5 is hijacked by an avian oncogenic herpesvirus to inhibit interferon beta production and promote viral replication

DEAD-box helicase 5 (DDX5) plays a significant role in tumorigenesis and regulates viral replication of several viruses. An avian oncogenic herpesvirus, Marek's disease virus (MDV), is widely known to cause immunosuppression and lymphoma in chickens. However, the underlying mechanisms of how DDX5 plays a role in viral replication remain unclear. In this study, we show that MDV inhibits the production of interferon beta (IFN-β) in chicken embryo fibroblasts (CEFs) by increasing the expression level and promoting the nuclear aggregation of DDX5. We further reveal how DDX5 down-regulates melanoma differentiation-associated gene 5/toll-like receptor 3 signaling through the fundamental transcription factor, interferon regulatory factor 1. MDV replication is suppressed, and the production of IFN-β is promoted in the DDX5 absented CEFs. Taken together, our investigations demonstrate that MDV inhibits IFN-β production by targeting DDX5-mediated signaling to facilitate viral replication, which offers a novel insight into the mechanism by which an avian oncogenic herpesvirus replicates in chicken cells.

The RNA helicase DDX5 promotes viral infection via regulating N6-methyladenosine levels on the DHX58 and NFκB transcripts to dampen antiviral innate immunity

Multi-functional DEAD-box helicase 5 (DDX5), which is important in transcriptional regulation, is hijacked by diverse viruses to facilitate viral replication. However, its regulatory effect in antiviral innate immunity remains unclear. We found that DDX5 interacts with the N⁶-methyladenosine (m6A) writer METTL3 to regulate methylation of mRNA through affecting the m6A writer METTL3–METTL14 heterodimer complex. Meanwhile, DDX5 promoted the m6A modification and nuclear export of transcripts DHX58, p65, and IKKγ by binding conserved UGCUGCAG element in innate response after viral infection. Stable IKKγ and p65 transcripts underwent YTHDF2-dependent mRNA decay, whereas DHX58 translation was promoted, resulting in inhibited antiviral innate response by DDX5 via blocking the p65 pathway and activating the DHX58-TBK1 pathway after infection with RNA virus. Furthermore, we found that DDX5 suppresses antiviral innate immunity in vivo. Our findings reveal that DDX5 serves as a negative regulator of innate immunity by promoting RNA methylation of antiviral transcripts and consequently facilitating viral propagation.

DEAD-box helicase 5 (DDX5) greatly contributes to cancer development and facilitation of viral propagation. However, how DDX5 manipulates host cell processes to facilitate replication remains poorly understood. In this study, we found DDX5 is a negative antiviral regulator through manipulating N⁶-methyladenosine (m6A) of transcripts in innate immunity. Firstly, DDX5 recruited the RNA m6A “writer” METTL3 to control the m6A writer complex, then specifically promoted m6A modification and nuclear export of DDX5 binding transcripts by binding conserved UGCUGCAG element in innate immune response, ultimately, leading to RNA decay of antiviral transcripts in a YTHDF2-dependent manner. Consequently, DDX5 played vital roles in cellular RNA metabolisms to negatively regulate innate immune response to viral infection. It is the first time to unravel DDX5 as an important component that mediates modification of N⁶-methyladenosine of mRNA in regulating innate immunity.

LINC01207 is up-regulated in gastric cancer tissues and promotes disease progression by regulating miR-671-5p/DDX5 axis

LINC01207 is involved in the progression of some cancers. This study was designed to delve into the biological function and mechanism of LINC01207 in gastric cancer. qPCR was adopted to examine the expression levels of LINC01207, miR-671-5p, DDX5 mRNA in gastric cancer tissues and cells. After LINC01207 was overexpressed or depleted, MTT and BrdU assays were conducted to detect cell proliferation. Transwell assay was employed to detect cell migration and invasion. Western blot was used to detect the expression of DDX5 protein in cells. Bioinformatics analysis, luciferase reporter assay and RNA pull-down assay were performed to predict and validate the binding site between miR-671-5p and LINC01207 or DDX5. LINC01207, DDX5 mRNA were up-regulated in gastric cancer, while miR-671-5p was down-regulated; high expression of LINC01207 and transfection of miR-671-5p inhibitors facilitated the proliferation of gastric cancer cells; however, knocking down LINC01207 and the overexpression of miR-671-5p mimics had opposite biological effects. LINC01207 and miR-671-5p were interacted and miR-671-5p was negatively regulated by LINC01207. MiR-671-5p could reverse the function of LINC01207. DDX5 was a downstream target of miR-671-5p and was positively modulated by LINC01207. LINC01207 promotes the proliferation and metastasis of gastric cancer cells by regulating miR-671-5p/DDX5 axis.

Cerebral Cavernous Malformation 1 Determines YAP/TAZ Signaling-Dependent Metastatic Hallmarks of Prostate Cancer Cells

Enhanced Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ) signaling is correlated with the extraprostatic extension of prostate cancer. However, the mechanism by which YAP/TAZ signaling becomes hyperactive and drives prostate cancer progression is currently unclear. In this study, we revealed that higher expression of CCM1, which is uniquely found in advanced prostate cancer, is inversely correlated with metastasis-free and overall survival in patients with prostate cancer. We also demonstrated that CCM1 induces the metastasis of multiple types of prostate cancer cells by regulating YAP/TAZ signaling. Mechanistically, CCM1, a gene mutated in cerebral cavernous malformation, suppresses DDX5, which regulates the suppression of YAP/TAZ signaling, indicating that CCM1 and DDX5 are novel upstream regulators of YAP/TAZ signaling. Our findings highlight the importance of CCM1-DDX5-YAP/TAZ signaling in the metastasis of prostate cancer cells.

The DEAD-box protein family of RNA helicases: sentinels for a myriad of cellular functions with emerging roles in tumorigenesis

DEAD-box RNA helicases comprise a family within helicase superfamily 2 and make up the largest group of RNA helicases. They are a profoundly conserved family of RNA-binding proteins, carrying a generic Asp-Glu-Ala-Asp (D-E-A-D) motif that gives the family its name. Members of the DEAD-box family of RNA helicases are engaged in all facets of RNA metabolism from biogenesis to decay. DEAD-box proteins ordinarily function as constituents of enormous multi-protein complexes and it is believed that interactions with other components in the complexes might be answerable for the various capacities ascribed to these proteins. Therefore, their exact function is probably impacted by their interacting partners and to be profoundly context dependent. This may give a clarification to the occasionally inconsistent reports proposing that DEAD-box proteins have both pro- and anti-proliferative functions in cancer. There is emerging evidence that DEAD-box family of RNA helicases play pivotal functions in various cellular processes and in numerous cases have been embroiled in cellular proliferation and/or neoplastic transformation. In various malignancy types, DEAD-box RNA helicases have been reported to possess pro-proliferation or even oncogenic roles as well as anti-proliferative or tumor suppressor functions. Clarifying the exact function of DEAD-box helicases in cancer is probably intricate, and relies upon the cellular milieu and interacting factors. This review aims to summarize the current data on the numerous capacities that have been ascribed to DEAD-box RNA helicases. It also highlights their diverse actions upon malignant transformation in the various tumor types.

LncRNA SLC26A4-AS1 suppresses the MRN complex-mediated DNA repair signaling and thyroid cancer metastasis by destabilizing DDX5

Lymph node metastasis is the major adverse feature for recurrence and death of thyroid cancer patients. To identify lncRNAs involved in thyroid cancer metastasis, we systemically screened differentially expressed lncRNAs in lymph node metastasis, thyroid cancer, and normal tissues via RNAseq. We found that lncRNA SLC26A4-AS1 was continuously, significantly down-regulated in normal tissues, thyroid cancer, and lymph node metastasis specimens. Low SLC26A4-AS1 levels in tissues were significantly associated with poor prognosis of thyroid cancer patients. LncRNA SLC26A4-AS1 markedly inhibited migration, invasion, and metastasis capability of cancer cells in vitro and in vivo. Intriguingly, SLC26A4-AS1 could simultaneously interact with DDX5 and the E3 ligase TRIM25, which promoting DDX5 degradation through the ubiquitin-proteasome pathway. In particular, SLC26A4-AS1 inhibited expression of multiple DNA double-strand breaks (DSBs) repair genes, especially genes coding proteins in the MRE11/RAS50/NBS1 (MRN) complex. Enhanced interaction between DDX5 and transcriptional factor E2F1 due to silencing of SLC26A4-AS1 promoted binding of the DDX5-E2F1 complex at promoters of the MRN genes and, thus, stimulate the MRN/ATM dependent DSB signaling and thyroid cancer metastasis. Our study uncovered new insights into the biology driving thyroid cancer metastasis and highlights potentials of lncRNAs as future therapeutic targets again cancer metastasis.

Human MYC G-quadruplex: From discovery to a cancer therapeutic target

Overexpression of the MYC oncogene is a molecular hallmark of both cancer initiation and progression. Targeting MYC is a logical and effective cancer therapeutic strategy. A special DNA secondary structure, the G-quadruplex (G4), is formed within the nuclease hypersensitivity element III₁ (NHE III₁) region, located upstream of the MYC gene's P1 promoter that drives the majority of its transcription. Targeting such G4 structures has been a focus of anticancer therapies in recent decades. Thus, a comprehensive review of the MYC G4 structure and its role as a potential therapeutic target is timely. In this review, we first outline the discovery of the MYC G4 structure and evidence of its formation in vitro and in cells. Then, we describe the functional role of G4 in regulating MYC gene expression. We also summarize three types of MYC G4-interacting proteins that can promote, stabilize and unwind G4 structures. Finally, we discuss G4-binding molecules and the anticancer activities of G4-stabilizing ligands, including small molecular compounds and peptides, and assess their potential as novel anticancer therapeutics.

Silencing of p68 and STAT3 synergistically diminishes cancer progression

AIMS

Since several factors are involved in the tumorigenesis process, targeting only one factor most probably cannot overwhelm cancer progression. Therefore, it seems that combination therapy through targeting more than one cancer-related factor may lead to cancer control. The expression and function of p68 (DDX5; DEAD-Box Helicase 5) are dysregulated in various cancers. P68 is also a co-activator of many oncogenic transcription factors such as the signal transducer and activator of transcription-3 (STAT3), which contributes to cancer progression. This close connection between p68 and STAT3 plays an important role in the growth and development of cancer.

MATERIALS AND METHODS

We decided to suppress the p68/STAT3 axis in various cancer cells by using Polyethylene glycol-trimethyl Chitosan-Hyaluronic acid (PEG-TMC-HA) nanoparticles (NPs) loaded with siRNA molecules. We assessed the impact of this combination therapy on apoptosis, proliferation, angiogenesis, and tumor growth, both in vitro and in vivo.

KEY FINDINGS

The results showed that siRNA-loaded NPs notably suppressed the expression of p68/STAT3 axis in cancer cells, which was associated with blockade of tumor growth, colony formation, angiogenesis, and cancer cell migration. In addition to apoptosis induction, this combined therapy also reduced the expression of several tumor-promoting factors including Fibroblast growth factors (FGF), vascular endothelial growth factor (VEGF), transforming growth factor-β (TGF-β), matrix metallopeptidases-2 (MMP-2), MMP-9, hypoxia-inducible factor-(HIF-1α), interleukin-6 (IL-6), IL-33, Bcl-x, vimentin, and snail.

SIGNIFICANCE

These findings indicate the potential of this nano-based anti-cancer therapeutic strategy for efficient cancer therapy which should be further investigated in future studies.

Knockdown of terminal differentiation induced ncRNA (TINCR) suppresses proliferation and invasion in hepatocellular carcinoma by targeting the miR-218-5p/DEAD-box helicase 5 (DDX5) axis

Terminal differentiation induced ncRNA (TINCR), a newly identified lncRNA, has been found to be associated with different human cancers including hepatocellular carcinoma (HCC). However, little is known regarding the pathological mechanisms of TINCR in HCC progression. In this study, we confirmed that TINCR expression was upregulated in HCC tumors and cell lines, and high TINCR expression was associated with larger tumor size, advanced tumor node metastasis stage, and poor prognosis. Functionally, knockdown of TINCR facilitated apoptosis and suppressed viability, colony formation and invasion in Huh7 and Hep3B cells. Mechanically, TINCR functioned as competing endogenous RNA (ceRNA) to regulate DEAD-box helicase 5 (DDX5) expression through sponging miR-218-5p. Moreover, the miR-218-5p expression was downregulated and DDX5 expression was upregulated in HCC tumors. The silencing of miR-218-5p or ectopic expression of DDX5 abated the tumor-suppressive effect of TINCR knockdown in vitro. Furthermore, si-TINCR-induced inactivation of AKT signaling was rescued by suppression of miR-218-5p or overexpression of DDX5. Also, the silencing of TINCR resulted in tumor growth inhibition in vivo. In summary, knockdown of TINCR suppressed HCC progression presumably by inactivation of AKT signaling through targeting the miR-218-5p/DDX5 axis, suggesting a novel TINCR/miR-218-5p/DDX5 pathway and therapy target for HCC.

Affinity-Based Protein Profiling Reveals Cellular Targets of Photoreactive Anticancer Inhibitors

Affinity-based protein profiling has proven to be a powerful method in target identification of bioactive molecules. Here, this technology was applied in two photoreactive anticancer inhibitors, arenobufagin and HM30181. Using UV irradiation, these photoreactive reagents can covalently cross-link to target proteins, leading to a covalent binding with target proteins. Moreover, the cellular on/off targets of these two molecules, including ATP1A1, MDR1, PARP1, DDX5, NOP2, RAB6A, and ERGIC1 were first identified by affinity-based protein profiling and bioimaging approaches. The protein hit, PARP1, was further validated to be involved in the function of the anticancer effects.