DDX3 modulates the tumor microenvironment via its role in endoplasmic reticulum-associated translation

LPS-induced extracellular AREG triggers macrophage pyroptosis through the EGFR/TLR4 signaling pathway

Amphiregulin (AREG), a member of the EGF family, exists as a transmembrane protein anchored to the cell surface. In response to external stimuli, its extracellular domain is released into the extracellular matrix through paracrine or autocrine signaling. However, its role in septic macrophage pyroptosis remains poorly understood. This study aims to investigate the role of extracellular AREG in septic macrophages, mice, and patients. We found that high expression of extracellular AREG was regulated by RPLP1 at the translation level, which increased the expression of IL-6, CCL2, and CCL3 protein, as well as Caspase 1, IL-1β, and Nlrp3 mRNA expression, resulting in macrophage pyroptosis. Mechanistically, macrophage pyroptosis was aggravated by extracellular AREG pretreatment, which was triggered by extracellular AREG and ATP (adenosine 5'-triphosphate). The AREG-neutralizing antibody reduced LPS-induced epidermal growth factor receptor (EGFR) activation, TLR4 expression, and pyroptosis. Extracellular AREG-induced macrophage pyroptosis decreased with EGFR and NF-κB inhibition, as well as TLR4 and Myd88 knockout. Additionally, DTT-pretreated extracellular AREG suppressed macrophage pyroptosis. In vivo, extracellular AREG attenuates systemic inflammation infiltration and delays survival in a septic mouse model. Furthermore, extracellular AREG mediates sepsis in humans, and genes involved in the AREG-mediated pyroptosis signaling pathway were highly expressed in patients with severe sepsis compared with those with general or moderate sepsis. Overall, LPS-induced extracellular AREG aggravated or triggered macrophage pyroptosis through the EGFR/TLR4/Myd88/NF-κB signaling pathway, providing promising treatment strategies for sepsis.

RNA G-quadruplexes control mitochondria-localized mRNA translation and energy metabolism

Cancer cells rely on mitochondria for their bioenergetic supply and macromolecule synthesis. Central to mitochondrial function is the regulation of mitochondrial protein synthesis, which primarily depends on the cytoplasmic translation of nuclear-encoded mitochondrial mRNAs whose protein products are imported into mitochondria. Despite the growing evidence that mitochondrial protein synthesis contributes to the onset and progression of cancer, and can thus offer new opportunities for cancer therapy, knowledge of the underlying molecular mechanisms remains limited. Here, we show that RNA G-quadruplexes (RG4s) regulate mitochondrial function by modulating cytoplasmic mRNA translation of nuclear-encoded mitochondrial proteins. Our data support a model whereby the RG4 folding dynamics, under the control of oncogenic signaling and modulated by small molecule ligands or RG4-binding proteins, modifies mitochondria-localized cytoplasmic protein synthesis. Ultimately, this impairs mitochondrial functions, affecting energy metabolism and consequently cancer cell proliferation.

What's in a name: the multifaceted function of DNA- and RNA-binding proteins in T cell responses

Cellular differentiation allows cells to transition between different functional states and adapt to various environmental cues. The diversity and plasticity of this process is beautifully exemplified by T cells responding to pathogens, which undergo highly specialized differentiation tailored to the ongoing infection. Such antigen-induced T cell differentiation is regulated at the transcriptional level by DNA-binding proteins and at the post-transcriptional level by RNA-binding proteins. Although traditionally defined as separate protein classes, a growing body of evidence indicates an overlap between these two groups of proteins, collectively coined DNA/RNA-binding proteins (DRBPs). In this review, we describe how DRBPs might bind both DNA and RNA, discuss the putative functional relevance of this dual binding, and provide an exploratory analysis into characteristics that are associated with DRBPs. To exemplify the significance of DRBPs in T cell biology, we detail the activity of several established and putative DRBPs during the T cell response. Finally, we highlight several methodologies that allow untangling of the distinct functionalities of DRBPs at the DNA and RNA level, including key considerations to take into account when applying such methods.

DDX3 is critical for female fertility via translational control in oogenesis

DEAD-box RNA helicase 3 (DDX3) and its homologs play a vital role in translation initiation by unwinding secondary structures of selected mRNAs. The human DDX3 gene is located on the sex chromosomes, so there are DDX3X and DDX3Y. DDX3X is ubiquitously expressed in almost all tissues and critical for embryonic development, whereas DDX3Y is only expressed in the testis and essential for male fertility. Drosophila belle (bel) is the single ortholog of DDX3, and mutations in bel cause male and female infertility. Using Drosophila bel mutants and Ddx3x conditional knockout (cKO) mice, we confirmed the pivotal role of DDX3 in female fertility and ovarian development. Drosophila bel mutants exhibited female infertility and immature egg chambers. Consistently, oocyte-specific Ddx3x knockout in mice resulted in female infertility and impaired oogenesis. We further found that immature egg chambers in Drosophila bel mutants and impaired follicular development in oocyte-specific Ddx3x cKO mice were caused by excessive apoptosis. We also identified a set of DDX3 target genes involved in oocyte meiosis and maturation and demonstrated that DDX3 is involved in their translation in human cells. Our results suggest that DDX3 is critical for female fertility via translational control in oogenesis.

The expression of immune co-stimulators as a prognostic predictor of head and neck squamous cell carcinomas and oral squamous cell carcinomas

Background/purpose

T cells require second immune checkpoint molecules for activation and immune memory after antigen presentation. We found that inducible co-stimulator (ICOS) has been a favorable prognostic factor amongst B7 immune checkpoint co-stimulators (ICSs) families in head and neck squamous cell carcinoma (HNSCC) and oral SCC (OSCC).

Materials and methods

This study analyzed the expression of non-B7 tumor necrosis factor (TNF) superfamily ICSs in the Cancer Genome Atlas (TCGA) HNSCC cohort, our OSCC cohort, and TCGA pan-cancer datasets. The correlation in expression, prognosis, and immune status was assessed.

Results

The higher expression of CD27, CD30, CD40L, death domain 3 (DR3), and OX40, presumably on the T cell surface, defined better overall survival of HNSCC patients. Besides, CD27, CD30, CD40L, and OX40 were highly correlated with ICOS expression in tumors. CD27, CD40L, and DR3 expression are higher in HPV+ HNSCC tumors than in HPV- tumors. The combined expression level of CD27/OX40 or CD27/CD40L/OX40 enables the potent survival prediction of small, less nodal involvement, early stage, and HPV + tumor subsets. Tumors expressing high CD27, CD30, CD40L, ICOS, and OX40 exhibited enhanced immune cell infiltration. The high correlation in the expression of these ICSs was also noted in the vast majority of tumor types in TCGA datasets.

Conclusion

The findings of this study not only confirm the potential of the concordant stimulation of CD27, CD30, CD40L, ICOS, and OX40 as a crucial strategy in cancer immunotherapy but also inspire further exploration into the field, highlighting the promising future of cancer treatment.

DDX3 regulates cancer immune surveillance via 3' UTR-mediated cell-surface expression of PD-L1

Programmed death-1 (PD-1)/PD ligand-1 (PD-L1)-mediated immune escape contributes to cancer development and has been targeted as an anti-cancer strategy. Here, we show that inhibition of the RNA helicase DDX3 increased CD8+ T cell infiltration in syngeneic oral squamous cell carcinoma tumors. DDX3 knockdown compromised interferon-γ-induced PD-L1 expression and, in particular, reduced the level of cell-surface PD-L1. DDX3 promoted surface PD-L1 expression by recruiting the adaptor protein 2 (AP2) complex to the 3' UTR of PD-L1 mRNA. DDX3 depletion or 3' UTR truncation increased the binding of the coatomer protein complexes to PD-L1, leading to its intracellular accumulation. Therefore, this 3' UTR-dependent mechanism may counteract cellular negative effects on surface trafficking of PD-L1. Finally, pharmaceutic disruption of DDX3's interaction with AP2 reduced surface PD-L1 expression, supporting that the DDX3-AP2 pathway routes PD-L1 to the cell surface. Targeting DDX3 to modulate surface trafficking of immune checkpoint proteins may provide a potential strategy for cancer immunotherapy.

DDX27 regulates oral squamous cell carcinoma development through targeting CSE1L

THE HEADINGS AIMS

DEAD-box helicase 27 (DDX27), a member of the DEAD-Box nucleic acid helicase family, holds an elusive role in oral squamous cell carcinoma (OSCC). This study aims to unravel the regulatory functions of DDX27 in OSCC and explore its downstream targets.

MATERIALS AND METHODS

A commercial oral squamous cell carcinoma (OSCC) tissue microarray (TMA) was utilized. We analyzed differentially expressed genes in OSCC through the GEO database. Target gene silencing was achieved using the shRNA-mediated lentivirus method. Coexpedia analysis identified co-expressed genes associated with DDX27. Additionally, a Co-Immunoprecipitation (Co-IP) experiment confirmed the protein interaction between DDX27 and CSE1L. Xenograft tumor models were employed to evaluate DDX27's role in OSCC tumor formation.

KEY FINDINGS

Elevated DDX27 expression in OSCC correlated with a higher pathological grade. DDX27 knockdown resulted in decreased cell proliferation, increased apoptosis, inhibited cell migration, and induced G2/M phase cell cycle arrest, as well as impaired tumor outgrowth. Coexpedia analysis identified STAU1, NELFCD, and CSE1L as top co-expressed genes. Lentiviral vectors targeting STAU1, NELFCD, and CSE1L revealed that silencing CSE1L significantly impaired cell growth, indicating it as a downstream target of DDX27. Cell rescue experiments demonstrated that increased DDX27 levels ameliorated cell proliferation, attenuated apoptosis, and CSE1L depletion blocked cell development induced by DDX27 overexpression.

SIGNIFICANCES

This study highlighted DDX27 as a potential therapeutic target for OSCC treatment, shedding light on its crucial role in OSCC development. Targeting DDX27 or its downstream effector, CSE1L, holds promise for innovative OSCC therapies.

Ribosome profiling: a powerful tool in oncological research

Neoplastic cells need to adapt their gene expression pattern to survive in an ever-changing or unfavorable tumor microenvironment. Protein synthesis (or mRNA translation), an essential part of gene expression, is dysregulated in cancer. The emergence of distinct translatomic technologies has revolutionized oncological studies to elucidate translational regulatory mechanisms. Ribosome profiling can provide adequate information on diverse aspects of translation by aiding in quantitatively analyzing the intensity of translating ribosome-protected fragments. Here, we review the primary currently used translatomics techniques and highlight their advantages and disadvantages as tools for translatomics studies. Subsequently, we clarified the areas in which ribosome profiling could be applied to better understand translational control. Finally, we summarized the latest advances in cancer studies using ribosome profiling to highlight the extensive application of this powerful and promising translatomic tool.

Kindlin-2 enhances c-Myc translation through association with DDX3X to promote pancreatic ductal adenocarcinoma progression

Rationale: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive solid tumor, with extremely low survival rates. Identifying key signaling pathways driving PDAC progression is crucial for the development of therapies to improve patient response rates. Kindlin-2, a multi-functional protein, is involved in numerous biological processes including cell proliferation, apoptosis and migration. However, little is known about the functions of Kindlin-2 in pancreatic cancer progression in vivo. Methods: In this study, we employ an in vivo PDAC mouse model to directly investigate the role of Kindlin-2 in PDAC progression. Then, we utilized RNA-sequencing, the molecular and cellular assays to determine the molecular mechanisms by which Kindlin-2 promotes PDAC progression. Results: We show that loss of Kindlin-2 markedly inhibits KrasG12D-driven pancreatic cancer progression in vivo as well as in vitro. Furthermore, we provide new mechanistic insight into how Kindlin-2 functions in this process, A fraction of Kindlin-2 was localized to the endoplasmic reticulum and associated with the RNA helicase DDX3X, a key regulator of mRNA translation. Loss of Kindlin-2 blocked DDX3X from binding to the 5'-untranslated region of c-Myc and inhibited DDX3X-mediated c-Myc translation, leading to reduced c-Myc-mediated glucose metabolism and tumor growth. Importantly, restoration of the expression of either the full-length Kindlin-2 or c-Myc, but not that of a DDX3X-binding-defective mutant of Kindlin-2, in Kindlin-2 deficient PDAC cells, reversed the inhibition of glycolysis and pancreatic cancer progression induced by the loss of Kindlin-2. Conclusion: Our studies reveal a novel Kindlin-2-DDX3X-c-Myc signaling axis in PDAC progression and suggest that inhibition of this signaling axis may provide a promising therapeutic approach to alleviate PDAC progression.

USP7 imparts partial EMT state in colorectal cancer by stabilizing the RNA helicase DDX3X and augmenting Wnt/β-catenin signaling

Epithelial mesenchymal transition (EMT) is a fundamental and highly regulated process that is normally observed during embryonic development and tissue repair but is deregulated during advanced cancer. Classically, through the process of EMT, cancer cells gradually transition from a predominantly epithelial phenotype to a more invasive mesenchymal phenotype. Increasing studies have, however, brought into light the existence of unique intermediary states in EMT, often referred to as partial EMT states. Through our studies we have found the deubiquitinase USP7 to be strongly associated with the development of such a partial EMT state in colon cancer cells, characterized by the acquisition of mesenchymal characteristics but without the reduction in epithelial markers. We found USP7 to be overexpressed in colon adenocarcinomas and to be closely associated with advancing tumor stage. We found that functional inhibition or knockdown of USP7 is associated with a marked reduction in mesenchymal markers and in overall migration potential of cancer cells. Starting off with a proteomics-based approach we were able to identify and later on verify the DEAD box RNA helicase DDX3X to be an interacting partner of USP7. We then went on to show that USP7, through the stabilization of DDX3X, augments Wnt/β-catenin signaling, which has previously been shown to be greatly associated with colorectal cancer cell invasiveness. Our results indicate USP7 as a novel key player in establishing a partial mesenchymal phenotype in colorectal cancer.

Defining genomic, transcriptomic, proteomic, epigenetic, and phenotypic biomarkers with prognostic capability in male breast cancer: a systematic review

Although similar phenotypically, there is evidence that male and female breast cancer differ in their molecular landscapes. In this systematic review, we consolidated all existing prognostic biomarker data in male breast cancer spanning genetics, transcriptomics, proteomics, and epigenetics, and phenotypic features of prognostic value from articles published over a 29-year period (March 16, 1992, to May 1, 2021). We identified knowledge gaps in the existing literature, discussed limitations of the included studies, and outlined potential approaches for translational biomarker discovery and validation in male breast cancer. We also recognised STC2, DDX3, and DACH1 as underexploited markers of male-specific prognostic value in breast cancer. Finally, beyond describing the cumulative knowledge on the extensively researched markers oestrogen receptor-α, progesterone receptor, HER2, androgen receptor, and BRCA2, we highlighted ATM, CCND1, FGFR2, GATA3, HIF1-α, MDM2, TP53, and c-Myc as well studied predictors of poor survival that also aligned with several hallmarks of cancer.

The human DEAD-box helicase DDX3X as a regulator of mRNA translation

The human DEAD-box protein DDX3X is an RNA remodelling enzyme that has been implicated in various aspects of RNA metabolism. In addition, like many DEAD-box proteins, it has non-conventional functions that are independent of its enzymatic activity, e.g., DDX3X acts as an adaptor molecule in innate immune signalling pathways. DDX3X has been linked to several human diseases. For example, somatic mutations in DDX3X were identified in various human cancers, and de novo germline mutations cause a neurodevelopmental condition now termed 'DDX3X syndrome'. DDX3X is also an important host factor in many different viral infections, where it can have pro-or anti-viral effects depending on the specific virus. The regulation of translation initiation for specific mRNA transcripts is likely a central cellular function of DDX3X, yet many questions regarding its exact targets and mechanisms of action remain unanswered. In this review, we explore the current knowledge about DDX3X's physiological RNA targets and summarise its interactions with the translation machinery. A role for DDX3X in translational reprogramming during cellular stress is emerging, where it may be involved in the regulation of stress granule formation and in mediating non-canonical translation initiation. Finally, we also discuss the role of DDX3X-mediated translation regulation during viral infections. Dysregulation of DDX3X's function in mRNA translation likely contributes to its involvement in disease pathophysiology. Thus, a better understanding of its exact mechanisms for regulating translation of specific mRNA targets is important, so that we can potentially develop therapeutic strategies for overcoming the negative effects of its dysregulation.

DEAD-Box RNA Helicases DDX3X and DDX5 as Oncogenes or Oncosuppressors: A Network Perspective

Simple Summary

The transformation of a normal cell into a cancerous one is caused by the deregulation of different metabolic pathways, involving a complex network of protein–protein interactions. The cellular enzymes DDX3X and DDX5 play important roles in the maintenance of normal cell metabolism, but their deregulation can accelerate tumor transformation. Both DDX3X and DDX5 interact with hundreds of different cellular proteins, and depending on the specific pathways in which they are involved, both proteins can either act as suppressors of cancer or as oncogenes. In this review, we summarize the current knowledge about the roles of DDX3X and DDX5 in different tumors. In addition, we present a list of interacting proteins and discuss the possible contribution of some of these protein–protein interactions in determining the roles of DDX3X and DDX5 in the process of cancer proliferation, also suggesting novel hypotheses for future studies.

Abstract

RNA helicases of the DEAD-box family are involved in several metabolic pathways, from transcription and translation to cell proliferation, innate immunity and stress response. Given their multiple roles, it is not surprising that their deregulation or mutation is linked to different pathological conditions, including cancer. However, while in some cases the loss of function of a given DEAD-box helicase promotes tumor transformation, indicating an oncosuppressive role, in other contexts the overexpression of the same enzyme favors cancer progression, thus acting as a typical oncogene. The roles of two well-characterized members of this family, DDX3X and DDX5, as both oncogenes and oncosuppressors have been documented in several cancer types. Understanding the interplay of the different cellular contexts, as defined by the molecular interaction networks of DDX3X and DDX5 in different tumors, with the cancer-specific roles played by these proteins could help to explain their apparently conflicting roles as cancer drivers or suppressors.

Disorder at the Start: The Contribution of Dysregulated Translation Initiation to Cancer Therapy Resistance

Translation of cellular RNA to protein is an energy-intensive process through which synthesized proteins dictate cellular processes and function. Translation is regulated in response to extracellular effectors and availability of amino acids intracellularly. Most eukaryotic mRNA rely on the methyl 7-guanosine (m7G) nucleotide cap to recruit the translation machinery, and the uncoupling of translational control that occurs in tumorigenesis plays a significant role in cancer treatment response. This article provides an overview of the mammalian translation initiation process and the primary mechanisms by which it is regulated. An outline of how deregulation of initiation supports tumorigenesis and how initiation at a downstream open reading frame (ORF) of Tousled-like kinase 1 (TLK1) leads to treatment resistance is discussed.