A feedback loop comprising lin-28 and let-7 controls pre-let-7 maturation during neural stem-cell commitment

The microRNA Let-7 and its exosomal form: Epigenetic regulators of gynecological cancers

Many types of gynecological cancer (GC) are often silent until they reach an advanced stage, and are therefore often diagnosed too late for effective treatment. Hence, there is a real need for more efficient diagnosis and treatment for patients with GC. During recent years, researchers have increasingly studied the impact of microRNAs cancer development, leading to a number of applications in detection and treatment. MicroRNAs are a particular group of tiny RNA molecules that regulate regular gene expression by affecting the translation process. The downregulation of numerous miRNAs has been observed in human malignancies. Let-7 is an example of a miRNA that controls cellular processes as well as signaling cascades to affect post-transcriptional gene expression. Recent research supports the hypothesis that enhancing let-7 expression in those cancers where it is downregulated may be a potential treatment option. Exosomes are tiny vesicles that move through body fluids and can include components like miRNAs (including let-7) that are important for communication between cells. Studies proved that exosomes are able to enhance tumor growth, angiogenesis, chemoresistance, metastasis, and immune evasion, thus suggesting their importance in GC management.

Molecular mechanisms underlying the regulation of tumour suppressor genes in lung cancer

Tumour suppressor genes play a cardinal role in the development of a large array of human cancers, including lung cancer, which is one of the most frequently diagnosed cancers worldwide. Therefore, extensive studies have been committed to deciphering the underlying mechanisms of alterations of tumour suppressor genes in governing tumourigenesis, as well as resistance to cancer therapies. In spite of the encouraging clinical outcomes demonstrated by lung cancer patients on initial treatment, the subsequent unresponsiveness to first-line treatments manifested by virtually all the patients is inherently a contentious issue. In light of the aforementioned concerns, this review compiles the current knowledge on the molecular mechanisms of some of the tumour suppressor genes implicated in lung cancer that are either frequently mutated and/or are located on the chromosomal arms having high LOH rates (1p, 3p, 9p, 10q, 13q, and 17p). Our study identifies specific genomic loci prone to LOH, revealing a recurrent pattern in lung cancer cases. These loci, including 3p14.2 (FHIT), 9p21.3 (p16INK4a), 10q23 (PTEN), 17p13 (TP53), exhibit a higher susceptibility to LOH due to environmental factors such as exposure to DNA-damaging agents (carcinogens in cigarette smoke) and genetic factors such as chromosomal instability, genetic mutations, DNA replication errors, and genetic predisposition. Furthermore, this review summarizes the current treatment landscape and advancements for lung cancers, including the challenges and endeavours to overcome it. This review envisages inspired researchers to embark on a journey of discovery to add to the list of what was known in hopes of prompting the development of effective therapeutic strategies for lung cancer.

Aberrant stem cell and developmental programs in pediatric leukemia

Hematopoiesis is a finely orchestrated process, whereby hematopoietic stem cells give rise to all mature blood cells. Crucially, they maintain the ability to self-renew and/or differentiate to replenish downstream progeny. This process starts at an embryonic stage and continues throughout the human lifespan. Blood cancers such as leukemia occur when normal hematopoiesis is disrupted, leading to uncontrolled proliferation and a block in differentiation of progenitors of a particular lineage (myeloid or lymphoid). Although normal stem cell programs are crucial for tissue homeostasis, these can be co-opted in many cancers, including leukemia. Myeloid or lymphoid leukemias often display stem cell-like properties that not only allow proliferation and survival of leukemic blasts but also enable them to escape treatments currently employed to treat patients. In addition, some leukemias, especially in children, have a fetal stem cell profile, which may reflect the developmental origins of the disease. Aberrant fetal stem cell programs necessary for leukemia maintenance are particularly attractive therapeutic targets. Understanding how hijacked stem cell programs lead to aberrant gene expression in place and time, and drive the biology of leukemia, will help us develop the best treatment strategies for patients.

Post-transcriptional (re)programming of B lymphocyte development: From bench to bedside?

Hematopoiesis, a process which generates blood and immune cells, changes significantly during mammalian development. Definitive hematopoiesis is marked by the emergence of long-term hematopoietic stem cells (HSCs). Here, we will focus on the post-transcriptional differences between fetal liver (FL) and adult bone marrow (ABM) HSCs. It remains unclear how or why exactly FL HSCs transition to ABM HSCs, but we aim to leverage their differences to revive an old idea: in utero HSC transplantation. Unexpectedly, the expression of certain RNA-binding proteins (RBPs) play an important role in HSC specification, and can be employed to convert or reprogram adult HSCs back to a fetal-like state. Among other features, FL HSCs have a broad differentiation capacity that includes the ability to regenerate both conventional B and T cells, as well as innate-like or unconventional lymphocytes such as B-1a and marginal zone B (MzB) cells. This chapter will focus on RNA binding proteins, namely LIN28B and IGF2BP3, that are expressed during fetal life and how they promote B-1a cell development. Furthermore, this chapter considers a potential clinical application of synthetic co-expression of LIN28B and IGF2BP3 in HSCs.

Structural atlas of human primary microRNAs generated by SHAPE-MaP

MicroRNA (miRNA) maturation is critically dependent on structural features of primary transcripts (pri-miRNAs). However, the scarcity of determined pri-miRNA structures has limited our understanding of miRNA maturation. Here, we employed selective 2'-hydroxyl acylation analyzed by primer extension and mutational profiling (SHAPE-MaP), a high-throughput RNA structure probing method, to unravel the secondary structures of 476 high-confidence human pri-miRNAs. Our SHAPE-based structures diverge substantially from those inferred solely from computation, particularly in the apical loop and basal segments, underlining the need for experimental data in RNA structure prediction. By comparing the structures with high-throughput processing data, we determined the optimal structural features of pri-miRNAs. The sequence determinants are influenced substantially by their structural contexts. Moreover, we identified an element termed the bulged GWG motif (bGWG) with a 3' bulge in the lower stem, which promotes processing. Our structure-function mapping better annotates the determinants of pri-miRNA processing and offers practical implications for designing small hairpin RNAs and predicting the impacts of miRNA mutations.

Lin28 affects the proliferation and osteogenic differentiation of human dental pulp stem cells by directly inhibiting let-7b maturation

OBJECTIVE

Activation of Lin28 gene under certain conditions promotes tissue damage repair. However, it remains unknown whether conditional expression of Lin28 facilitates the recovery of damaged pulp tissue. In the study, we focus on exploring the effects and possible regulatory mechanisms of Lin28 on the proliferation and differentiation of human dental pulp stem cells (hDPSCs).

MATERIALS AND METHODS

We adopted techniques such as the ethynyl-2'-deoxyuridine (EdU) incorporation assay, RNA-protein immunoprecipitation (RIP) analysis, and luciferase assays to study the regulation of hDPSCs by Lin28. Furthermore, gain-of-function and loss-of-function analyses were also used in explored factors regulating hDPSCs activation.

RESULTS

The results show that Lin28 inhibited osteogenic differentiation by directly targets pre-let-7b. Through bioinformatics sequencing and dual luciferase experiments we learned that let-7b directly targets the IGF2BP2 3'UTR. Silencing of IGF2BP2 showed a similar biological effect as overexpression of let-7b. Overexpression of IGF2BP2 counteracted the differentiation-promoting effects produced by let-7b overexpression.

DISCUSSION/CONCLUSIONS

In conclusion, the RNA-binding protein Lin28 regulates osteogenic differentiation of hDPSCs by inhibiting let-7 miRNA maturation. And mature let-7b directly regulated the expression of IGF2BP2 by targeting the 3'UTR region of IGF2BP2 mRNA thus further inhibiting the differentiation of hDPSCs.

Dynamic nucleolar phase separation influenced by non-canonical function of LIN28A instructs pluripotent stem cell fate decisions

LIN28A is important in somatic reprogramming and pluripotency regulation. Although previous studies addressed that LIN28A can repress let-7 microRNA maturation in the cytoplasm, few focused on its role within the nucleus. Here, we show that the nucleolus-localized LIN28A protein undergoes liquid-liquid phase separation (LLPS) in mouse embryonic stem cells (mESCs) and in vitro. The RNA binding domains (RBD) and intrinsically disordered regions (IDR) of LIN28A contribute to LIN28A and the other nucleolar proteins' phase-separated condensate establishment. S120A, S200A and R192G mutations in the IDR result in subcellular mislocalization of LIN28A and abnormal nucleolar phase separation. Moreover, we find that the naive-to-primed pluripotency state conversion and the reprogramming are associated with dynamic nucleolar remodeling, which depends on LIN28A's phase separation capacity, because the LIN28A IDR point mutations abolish its role in regulating nucleolus and in these cell fate decision processes, and an exogenous IDR rescues it. These findings shed light on the nucleolar function in pluripotent stem cell states and on a non-canonical RNA-independent role of LIN28A in phase separation and cell fate decisions.

Hair Cell Regeneration: From Animals to Humans

Cochlear hair cells convert sound into electrical signals that are relayed via the spiral ganglion neurons to the central auditory pathway. Hair cells are vulnerable to damage caused by excessive noise, aging, and ototoxic agents. Non-mammals can regenerate lost hair cells by mitotic regeneration and direct transdifferentiation of surrounding supporting cells. However, in mature mammals, damaged hair cells are not replaced, resulting in permanent hearing loss. Recent studies have uncovered mechanisms by which sensory organs in non-mammals and the neonatal mammalian cochlea regenerate hair cells, and outlined possible mechanisms why this ability declines rapidly with age in mammals. Here, we review similarities and differences between avian, zebrafish, and mammalian hair cell regeneration. Moreover, we discuss advances and limitations of hair cell regeneration in the mature cochlea and their potential applications to human hearing loss.

Growth-suppressor microRNAs mediate synaptic overgrowth and behavioral deficits in Fragile X mental retardation protein deficiency

Abnormal neuronal and synapse growth is a core pathology resulting from deficiency of the Fragile X mental retardation protein (FMRP), but molecular links underlying the excessive synthesis of key synaptic proteins remain incompletely defined. We find that basal brain levels of the growth suppressor let-7 microRNA (miRNA) family are selectively lowered in FMRP-deficient mice and activity-dependent let-7 downregulation is abrogated. Primary let-7 miRNA transcripts are not altered in FMRP-deficiency and posttranscriptional misregulation occurs downstream of MAPK pathway induction and elevation of Lin28a, a let-7 biogenesis inhibitor. Neonatal restoration of brain let-7 miRNAs corrects hallmarks of FMRP-deficiency, including dendritic spine overgrowth and social and cognitive behavioral deficits, in adult mice. Blockade of MAPK hyperactivation normalizes let-7 miRNA levels in both brain and peripheral blood plasma from Fmr1 KO mice. These results implicate dysregulated let-7 miRNA biogenesis in the pathogenesis of FMRP-deficiency, and highlight let-7 miRNA-based strategies for future biomarker and therapeutic development.

Exploring Lin28 proteins: Unravelling structure and functions with emphasis on nervous system malignancies

Cancer and stem cells share many characteristics related to self-renewal and differentiation. Both cell types express the same critical proteins that govern cellular stemness, which provide cancer cells with the growth and survival benefits of stem cells. LIN28 is an example of one such protein. LIN28 includes two main isoforms, LIN28A and LIN28B, with diverse physiological functions from tissue development to control of pluripotency. In addition to their physiological roles, LIN28A and LIN28B affect the progression of several cancers by regulating multiple cancer hallmarks. Altered expression levels of LIN28A and LIN28B have been proposed as diagnostic and/or prognostic markers for various malignancies. This review discusses the structure and modes of action of the different LIN28 proteins and examines their roles in regulating cancer hallmarks with a focus on malignancies of the nervous system. This review also highlights some gaps in the field that require further exploration to assess the potential of targeting LIN28 proteins for controlling cancer.

microRNAs in action: biogenesis, function and regulation

Ever since microRNAs (miRNAs) were first recognized as an extensive gene family >20 years ago, a broad community of researchers was drawn to investigate the universe of small regulatory RNAs. Although core features of miRNA biogenesis and function were revealed early on, recent years continue to uncover fundamental information on the structural and molecular dynamics of core miRNA machinery, how miRNA substrates and targets are selected from the transcriptome, new avenues for multilevel regulation of miRNA biogenesis and mechanisms for miRNA turnover. Many of these latest insights were enabled by recent technological advances, including massively parallel assays, cryogenic electron microscopy, single-molecule imaging and CRISPR-Cas9 screening. Here, we summarize the current understanding of miRNA biogenesis, function and regulation, and outline challenges to address in the future.

Effect of down-regulation of let-7c/g on triggering a double-negative feedback loop and promoting restenosis

BACKGROUND

Excessive proliferation and migration of vascular smooth muscle cells (VSMCs) are the main causes of restenosis (RS) in diabetic lower extremity arterial disease (LEAD). However, the relevant pathogenic mechanisms are poorly understood.

METHODS

In this study, we introduced a "two-step injury protocol" rat RS model, which started with the induction of atherosclerosis (AS) and was followed by percutaneous transluminal angioplasty (PTA). Hematoxylin-eosin (HE) staining and immunohistochemistry staining were used to verify the form of RS. Two-step transfection was performed, with the first transfection of Lin28a followed by a second transfection of let-7c and let-7g, to explore the possible mechanism by which Lin28a exerted effects. 5-ethynyl-2΄-deoxyuridine (EdU) and Transwell assay were performed to evaluate the ability of proliferation and migration of VSMCs. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) were performed to detect the expression of Lin28a protein and let-7 family members.

RESULTS

Using a combination of in vitro and in vivo experiments, we discovered that let-7c, let-7g, and microRNA98 (miR98) were downstream targets of Lin28a. More importantly, decreased expression of let-7c/let-7g increased Lin28a, leading to further inhibition of let-7c/let-7g. We also found an increased level of let-7d in the RS pathological condition, suggesting that it may function as a protective regulator of the Lin28a/let-7 loop by inhibiting the proliferation and migration of VSMCs.

CONCLUSION

These findings indicated the presence of a double-negative feedback loop consisting of Lin28a and let-7c/let-7g, which may be responsible for the vicious behavior of VSMCs in RS.

Parameters of clustered suboptimal miRNA biogenesis

The nuclear cleavage of a suboptimal primary miRNA hairpin by the Drosha/DGCR8 complex ("Microprocessor") can be enhanced by an optimal miRNA neighbor, a phenomenon termed cluster assistance. Several features and biological impacts of this new layer of miRNA regulation are not fully known. Here, we elucidate the parameters of cluster assistance of a suboptimal miRNA and also reveal competitive interactions amongst optimal miRNAs within a cluster. We exploit cluster assistance as a functional assay for suboptimal processing and use this to invalidate putative suboptimal substrates, as well as identify a "solo" suboptimal miRNA. Finally, we report complexity in how specific mutations might affect the biogenesis of clustered miRNAs in disease contexts. This includes how an operon context can buffer the effect of a deleterious processing variant, but reciprocally how a point mutation can have a nonautonomous effect to impair the biogenesis of a clustered, suboptimal, neighbor. These data expand our knowledge regarding regulated miRNA biogenesis in humans and represent a functional assay for empirical definition of suboptimal Microprocessor substrates.

Lin28 regulates thymic growth and involution and correlates with MHCII expression in thymic epithelial cells

Thymic epithelial cells (TECs) are essential for T cell development in the thymus, yet the mechanisms governing their differentiation are not well understood. Lin28, known for its roles in embryonic development, stem cell pluripotency, and regulating cell proliferation and differentiation, is expressed in endodermal epithelial cells during embryogenesis and persists in adult epithelia, implying postnatal functions. However, the detailed expression and function of Lin28 in TECs remain unknown. In this study, we examined the expression patterns of Lin28 and its target Let-7g in fetal and postnatal TECs and discovered opposing expression patterns during postnatal thymic growth, which correlated with FOXN1 and MHCII expression. Specifically, Lin28b showed high expression in MHCIIhi TECs, whereas Let-7g was expressed in MHCIIlo TECs. Deletion of Lin28a and Lin28b specifically in TECs resulted in reduced MHCII expression and overall TEC numbers. Conversely, overexpression of Lin28a increased total TEC and thymocyte numbers by promoting the proliferation of MHCIIlo TECs. Additionally, our data strongly suggest that Lin28 and Let-7g expression is reliant on FOXN1 to some extent. These findings suggest a critical role for Lin28 in regulating the development and differentiation of TECs by modulating MHCII expression and TEC proliferation throughout thymic ontogeny and involution. Our study provides insights into the mechanisms underlying TEC differentiation and highlights the significance of Lin28 in orchestrating these processes.

C1632 inhibits ovarian cancer cell growth and migration by inhibiting LIN28 B/let-7/FAK signaling pathway and FAK phosphorylation

The highly conserved RNA-binding protein LIN28B and focal adhesion kinase (FAK) are significantly upregulated in ovarian cancer (OC), serving as markers for disease progression and prognosis. Nonetheless, the correlation between LIN28B and FAK, as well as the pharmacological effects of the LIN28 inhibitor C1632, in OC cells have not been elucidated. The present study demonstrates that C1632 significantly reduced the rate of DNA replication, arrested the cell cycle at the G0/G1 phase, consequently reducing cell viability, and impeding clone formation. Moreover, treatment with C1632 decreased cell-matrix adhesion, as well as inhibited cell migration and invasion. Further mechanistic studies revealed that C1632 inhibited the OC cell proliferation and migration by concurrently inhibiting LIN28 B/let-7/FAK signaling pathway and FAK phosphorylation. Furthermore, C1632 exhibited an obvious inhibitory effect on OC cell xenograft tumors in mice. Altogether, these findings identified that LIN28 B/let-7/FAK is a valuable target in OC and C1632 is a promising onco-therapeutic agent for OC treatment.

miR-153-3p suppresses the differentiation and proliferation of neural stem cells via targeting GPR55

Alzheimer's disease is the most frequent neurodegenerative disease and is characterized by progressive cognitive impairment and decline. NSCs (neural stem cells) serve as beneficial and promising adjuncts to treat Alzheimer's disease. This study aimed to determine the role of miR-153-3p expression in NSC differentiation and proliferation. We illustrated that miR-153-3p was decreased and GPR55 was upregulated during NSC differentiation. IL-1β can induce miR-153-3p expression. Luciferase reporter analysis noted that elevated expression of miR-153-3p significantly inhibited the luciferase value of the WT reporter plasmid but did not change the luciferase value of the mut reporter plasmid. Ectopic miR-153-3p expression suppressed GPR55 expression in NSCs and identified GPR55 as a direct target gene of miR-153-3p. Ectopic expression of miR-153-3p inhibited NSC growth and differentiation into astrocytes and neurons. Elevated expression of miR-153-3p induced the release of proinflammatory cytokines, such as TNF-α, IL-1β and IL-6, in NSCs. Furthermore, miR-153-3p inhibited NSC differentiation and proliferation by targeting GPR55 expression. These data suggested that miR-153-3p may act as a clinical target for the therapeutics of neurodegenerative diseases.

Accelerated export of Dicer1 from lipid-challenged hepatocytes buffers cellular miRNA-122 levels and prevents cell death

Hepatocytes on exposure to high levels of lipids reorganize the metabolic program while fighting against the toxicity associated with elevated cellular lipids. The mechanism of this metabolic reorientation and stress management in lipid-challenged hepatocytes has not been well explored. We have noted the lowering of miR-122, a liver-specific miRNA, in the liver of mice fed with either a high-fat diet or a methionine-choline-deficient diet that is associated with increased fat accumulation in mice liver. Interestingly, low miR-122 levels are attributed to the enhanced extracellular export of miRNA processor enzyme Dicer1 from hepatocytes in the presence of high lipids. Export of Dicer1 can also account for the increased cellular levels of pre-miR-122-the substrate of Dicer1. Interestingly, restoration of Dicer1 levels in the mouse liver resulted in a strong inflammatory response and cell death in the presence of high lipids. Increasing death of hepatocytes was found to be caused by increased miR-122 levels in hepatocytes restored for Dicer1. Thus, the Dicer1 export by hepatocytes seems to be a key mechanism to combat lipotoxic stress by shunting out miR-122 from stressed hepatocytes. Finally, as part of this stress management, we determined that the Ago2-interacting pool of Dicer1, responsible for mature microribonucleoprotein formation in mammalian cells, gets depleted. miRNA-binder and exporter protein HuR is found to accelerate Ago2-Dicer1 uncoupling to ensure export of Dicer1 via extracellular vesicles in lipid-loaded hepatocytes.

Convergence of multiple RNA-silencing pathways on GW182/TNRC6

The RNA-binding protein TRIM71/LIN-41 is a phylogenetically conserved developmental regulator that functions in mammalian stem cell reprogramming, brain development, and cancer. TRIM71 recognizes target mRNAs through hairpin motifs and silences them through molecular mechanisms that await identification. Here, we uncover that TRIM71 represses its targets through RNA-supported interaction with TNRC6/GW182, a core component of the miRNA-induced silencing complex (miRISC). We demonstrate that AGO2, TRIM71, and UPF1 each recruit TNRC6 to specific sets of transcripts to silence them. As cellular TNRC6 levels are limiting, competition occurs among the silencing pathways, such that the loss of AGO proteins or of AGO binding to TNRC6 enhances the activities of the other pathways. We conclude that a miRNA-like silencing activity is shared among different mRNA silencing pathways and that the use of TNRC6 as a central hub provides a means to integrate their activities.

Temporal transitions in the postembryonic nervous system of the nematode Caenorhabditis elegans: Recent insights and open questions

After the generation, differentiation and integration into functional circuitry, post-mitotic neurons continue to change certain phenotypic properties throughout postnatal juvenile stages until an animal has reached a fully mature state in adulthood. We will discuss such changes in the context of the nervous system of the nematode C. elegans, focusing on recent descriptions of anatomical and molecular changes that accompany postembryonic maturation of neurons. We summarize the characterization of genetic timer mechanisms that control these temporal transitions or maturational changes, and discuss that many but not all of these transitions relate to sexual maturation of the animal. We describe how temporal, spatial and sex-determination pathways are intertwined to sculpt the emergence of cell-type specific maturation events. Finally, we lay out several unresolved questions that should be addressed to move the field forward, both in C. elegans and in vertebrates.

Antisense Oligonucleotides against Let-7 Enhance the Therapeutic Potential of Mesenchymal Stromal Cells

Let-7 miRNAs have pleiotropic cellular functions in cell proliferation, migration, and regenerative processes. Here, we investigate whether the inhibition of let-7 miRNAs with antisense oligonucleotides (ASOs) can be a transient and safe strategy enhancing the therapeutic potential of mesenchymal stromal cells (MSCs) to overcome their limitations in cell therapeutic trials. We first identified major subfamilies of let-7 miRNAs preferentially expressed in MSCs, and efficient ASO combinations against these selected subfamilies that mimic the effects of LIN28 activation. When let-7 miRNAs were inhibited with an ASO combination (anti-let7-ASOs), MSCs exhibited higher proliferation with delayed senescence during the passaging into a culture. They also exhibited increased migration and enhanced osteogenic differentiation potential. However, these changes in MSCs were not accompanied by cell-fate changes into pericytes or the additional acquisition of stemness, but instead occurred as functional changes accompanied by changes in proteomics. Interestingly, MSCs with let-7 inhibition exhibited metabolic reprogramming characterized by an enhanced glycolytic pathway, decreased reactive oxygen species, and lower transmembrane potential in mitochondria. Moreover, let-7-inhibited MSCs promoted the self-renewal of neighboring hematopoietic progenitor cells, and enhanced capillary formation in endothelial cells. These findings together show that our optimized ASO combination efficiently reprograms the MSC functional state, allowing for more efficient MSC cell therapy.

The role of LIN28B in tumor progression and metastasis in solid tumor entities

LIN28B is an RNA-binding protein that targets a broad range of microRNAs and modulates their maturation and activity. Under normal conditions, LIN28B is exclusively expressed in embryogenic stem cells, blocking differentiation and promoting proliferation. In addition, it can play a role in epithelial-to-mesenchymal transition by repressing the biogenesis of let-7 microRNAs. In malignancies, LIN28B is frequently overexpressed, which is associated with increased tumor aggressiveness and metastatic properties. In this review, we discuss the molecular mechanisms of LIN28B in promoting tumor progression and metastasis in solid tumor entities and its potential use as a clinical therapeutic target and biomarker.

LIN28 and histone H3K4 methylase induce TLR4 to generate tumor-initiating stem-like cells

Chemoresistance and plasticity of tumor-initiating stem-like cells (TICs) promote tumor recurrence and metastasis. The gut-originating endotoxin-TLR4-NANOG oncogenic axis is responsible for the genesis of TICs. This study investigated mechanisms as to how TICs arise through transcriptional, epigenetic, and post-transcriptional activation of oncogenic TLR4 pathways. Here, we expressed constitutively active TLR4 (caTLR4) in mice carrying pLAP-tTA or pAlb-tTA, under a tetracycline withdrawal-inducible system. Liver progenitor cell induction accelerated liver tumor development in caTLR4-expressing mice. Lentiviral shRNA library screening identified histone H3K4 methylase SETD7 as central to activation of TLR4. SETD7 combined with hypoxia induced TLR4 through HIF2 and NOTCH. LIN28 post-transcriptionally stabilized TLR4 mRNA via de-repression of let-7 microRNA. These results supported a LIN28-TLR4 pathway for the development of HCCs in a hypoxic microenvironment. These findings not only advance our understanding of molecular mechanisms responsible for TIC generation in HCC, but also represent new therapeutic targets for the treatment of HCC.

Glycolytic Pfkp acts as a Lin41 protein kinase to promote endodermal differentiation of embryonic stem cells

Unveiling the principles governing embryonic stem cell (ESC) differentiation into specific lineages is critical for understanding embryonic development and for stem cell applications in regenerative medicine. Here, we establish an intersection between LIF-Stat3 signaling that is essential for maintaining murine (m) ESCs pluripotency, and the glycolytic enzyme, the platelet isoform of phosphofructokinase (Pfkp). In the pluripotent state, Stat3 transcriptionally suppresses Pfkp in mESCs while manipulating the cells to lift this repression results in differentiation towards the ectodermal lineage. Pfkp exhibits substrate specificity changes to act as a protein kinase, catalyzing serine phosphorylation of the developmental regulator Lin41. Such phosphorylation stabilizes Lin41 by impeding its autoubiquitination and proteasomal degradation, permitting Lin41-mediated binding and destabilization of mRNAs encoding ectodermal specification markers to favor the expression of endodermal specification genes. This provides new insights into the wiring of pluripotency-differentiation circuitry where Pfkp plays a role in germ layer specification during mESC differentiation.

Promiscuous splicing-derived hairpins are dominant substrates of tailing-mediated defense of miRNA biogenesis in mammals

Canonical microRNA (miRNA) hairpins are processed by the RNase III enzymes Drosha and Dicer into ∼22 nt RNAs loaded into an Argonaute (Ago) effector. In addition, splicing generates numerous intronic hairpins that bypass Drosha (mirtrons) to yield mature miRNAs. Here, we identify hundreds of previously unannotated, splicing-derived hairpins in intermediate-length (∼50-100 nt) but not small (20-30 nt) RNA data. Since we originally defined mirtrons from small RNA duplexes, we term this larger set as structured splicing-derived RNAs (ssdRNAs). These associate with Dicer and/or Ago complexes, but generally accumulate modestly and are poorly conserved. We propose they contaminate the canonical miRNA pathway, which consequently requires defense against the siege of splicing-derived substrates. Accordingly, ssdRNAs/mirtrons comprise dominant hairpin substrates for 3' tailing by multiple terminal nucleotidyltransferases, notably TUT4/7 and TENT2. Overall, the rampant proliferation of young mammalian mirtrons/ssdRNAs, coupled with an inhibitory molecular defense, comprises a Red Queen's race of intragenomic conflict.

RNA-Binding Proteins in Bladder Cancer

RNA-binding proteins (RBPs) are key regulators of transcription and translation, with highly dynamic spatio-temporal regulation. They are usually involved in the regulation of RNA splicing, polyadenylation, and mRNA stability and mediate processes such as mRNA localization and translation, thereby affecting the RNA life cycle and causing the production of abnormal protein phenotypes that lead to tumorigenesis and development. Accumulating evidence supports that RBPs play critical roles in vital life processes, such as bladder cancer initiation, progression, metastasis, and drug resistance. Uncovering the regulatory mechanisms of RBPs in bladder cancer is aimed at addressing the occurrence and progression of bladder cancer and finding new therapies for cancer treatment. This article reviews the effects and mechanisms of several RBPs on bladder cancer and summarizes the different types of RBPs involved in the progression of bladder cancer and the potential molecular mechanisms by which they are regulated, with a view to providing information for basic and clinical researchers.

Position-dependent effects of RNA-binding proteins in the context of co-transcriptional splicing

Alternative splicing is an important step in eukaryotic mRNA pre-processing which increases the complexity of gene expression programs, but is frequently altered in disease. Previous work on the regulation of alternative splicing has demonstrated that splicing is controlled by RNA-binding proteins (RBPs) and by epigenetic DNA/histone modifications which affect splicing by changing the speed of polymerase-mediated pre-mRNA transcription. The interplay of these different layers of splicing regulation is poorly understood. In this paper, we derived mathematical models describing how splicing decisions in a three-exon gene are made by combinatorial spliceosome binding to splice sites during ongoing transcription. We additionally take into account the effect of a regulatory RBP and find that the RBP binding position within the sequence is a key determinant of how RNA polymerase velocity affects splicing. Based on these results, we explain paradoxical observations in the experimental literature and further derive rules explaining why the same RBP can act as inhibitor or activator of cassette exon inclusion depending on its binding position. Finally, we derive a stochastic description of co-transcriptional splicing regulation at the single-cell level and show that splicing outcomes show little noise and follow a binomial distribution despite complex regulation by a multitude of factors. Taken together, our simulations demonstrate the robustness of splicing outcomes and reveal that quantitative insights into kinetic competition of co-transcriptional events are required to fully understand this important mechanism of gene expression diversity.

Pharmacological inhibition of Lin28 promotes ketogenesis and restores lipid homeostasis in models of non-alcoholic fatty liver disease

Lin28 RNA-binding proteins are stem-cell factors that play key roles in development. Lin28 suppresses the biogenesis of let-7 microRNAs and regulates mRNA translation. Notably, let-7 inhibits Lin28, establishing a double-negative feedback loop. The Lin28/let-7 axis resides at the interface of metabolic reprogramming and oncogenesis and is therefore a potential target for several diseases. In this study, we use compound-C1632, a drug-like Lin28 inhibitor, and show that the Lin28/let-7 axis regulates the balance between ketogenesis and lipogenesis in liver cells. Hence, Lin28 inhibition activates synthesis and secretion of ketone bodies whilst suppressing lipogenesis. This occurs at least partly via let-7-mediated inhibition of nuclear receptor co-repressor 1, which releases ketogenesis gene expression mediated by peroxisome proliferator-activated receptor-alpha. In this way, small-molecule Lin28 inhibition protects against lipid accumulation in multiple cellular and male mouse models of hepatic steatosis. Overall, this study highlights Lin28 inhibitors as candidates for the treatment of hepatic disorders of abnormal lipid deposition.

Identifying key m6A-methylated lncRNAs and genes associated with neural tube defects via integrative MeRIP and RNA sequencing analyses

Objective: N6-methyladenosine (m6A) is a common post-transcriptional modification of messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs). However, m6A-modified lncRNAs are still largely unexplored. This study aimed to investigate differentially m6A-modified lncRNAs and genes involved in neural tube defect (NTD) development. Methods: Pregnant Kunming mice (9-10 weeks of age) were treated with retinoic acid to construct NTD models. m6A levels and methyltransferase-like 3 (METTL3) expression were evaluated in brain tissues of the NTD models. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were performed on the NovaSeq platform and Illumina HiSeq 2,500 platform, respectively. Differentially m6A-methylated differentially expressed lncRNAs (DElncRNAs) and differentially expressed genes (DEGs) were identified, followed by GO biological process and KEGG pathway functional enrichment analyses. Expression levels of several DElncRNAs and DEGs were evaluated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for validation. Results: m6A levels and METTL3 expression levels were significantly lower in the brain tissues of the NTD mouse model than in controls. By integrating MeRIP-seq and RNA-seq data, 13 differentially m6A-methylated DElncRNAs and 170 differentially m6A-methylated DEGs were identified. They were significantly enriched in the Hippo signaling pathway and mannose-type O-glycan biosynthesis. The qRT-PCR results confirmed the decreased expression levels of lncRNAs, such as Mir100hg, Gm19265, Gm10544, and Malat1, and genes, such as Zfp236, Erc2, and Hmg20a, in the NTD group. Conclusion: METTL3-mediated m6A modifications may be involved in NTD development. In particular, decreased expression levels of Mir100hg, Gm19265, Gm10544, Malat1, Zfp236, Erc2, and Hmg20a may contribute to the development of NTD.

miR-124- and let-7-Mediated Reprogram of Human Fibroblasts into SST Interneurons

Many neurological disorders stem from defects in or the loss of specific neurons. Dysfunction of γ-aminobutyric acid (GABA)ergic interneurons may cause a variety of neurological and psychiatric disorders such as epilepsy, autism, Alzheimer's disease, and depression. Unlike other types of neurons, which can be generated relatively easily by direct reprogramming, it is difficult to generate GABAergic neurons by traditional methods. Neuronal transdifferentiation of fibroblasts mediated by nongenomic-integrated adenovirus has many advantages, but the efficiency is low, and there is a lack of studies using human cells as the initial materials. In this study, we explored the feasibility of the conversion of human fibroblasts into neurons through adenovirus-mediated gene expression and found that by introducing two microRNAs, miR-124 and let-7, together with several small chemical compounds, they can effectively generate GABAergic neuron-like cells from human neonatal fibroblasts without reverting to a progenitor cell stage. Most of these cells expressed neuronal markers and were all somatostatin (SST)-positive cells. Therefore, our study provides a relatively safe and efficient method to generate SST interneurons.

Tumor necrosis factor alpha delivers exogenous inflammation-related microRNAs to recipient cells with functional targeting capabilities

Tumor necrosis factor alpha (TNF-α) is a critical pro-inflammatory cytokine in a wide range of tumors and infectious diseases. This study showed for the first time that TNF-α could specifically bind to certain intracellular or circulating inflammation-related microRNAs both in vitro and in vivo. The binding sites of TNF-α to microRNAs are located at the N-terminal of TNF-α and the 3'-GGUU motif of microRNAs. TNF-α could deliver exogenous unmodified single-stranded microRNAs into recipient cells through the TNF-α receptors (TNFRs) and stabilize them from being degraded by RNase in cells. Exogenous miR-146a or let-7c delivered into HCT116 cells by TNF-α could escape from lysosomes and specifically downregulate their target genes and then affect cell proliferation and migration in vitro, as well as tumorigenesis in vivo. Based on the above findings, the concept of "non-conjugated ligand-mediated RNA delivery (ncLMRD)" was proposed, which may serve as a promising strategy for therapeutic microRNA delivery in the future.

Panoramic view of microRNAs in regulating cancer stem cells

Cancer stem cells (CSCs) are a subgroup of tumor cells, possessing the abilities of self-renewal and generation of heterogeneous tumor cell lineages. They are believed to be responsible for tumor initiation, metastasis, as well as chemoresistance in human malignancies. MicroRNAs (miRNAs) are small noncoding RNAs that play essential roles in various cellular activities including CSC initiation and CSC-related properties. Mature miRNAs with ∼22 nucleotides in length are generated from primary miRNAs via its precursors by miRNA-processing machinery. Extensive studies have demonstrated that mature miRNAs modulate CSC initiation and stemness features by regulating multiple pathways and targeting stemness-related factors. Meanwhile, both miRNA precursors and miRNA-processing machinery can also affect CSC properties, unveiling a new insight into miRNA function. The present review summarizes the roles of mature miRNAs, miRNA precursors, and miRNA-processing machinery in regulating CSC properties with a specific focus on the related molecular mechanisms, and also outlines the potential application of miRNAs in cancer diagnosis, predicting prognosis, as well as clinical therapy.

Correlating multi-functional role of cold shock domain proteins with intrinsically disordered regions

Cold shock proteins (CSPs) are an ancient and conserved family of proteins. They are renowned for their role in response to low-temperature stress in bacteria and nucleic acid binding activities. In prokaryotes, cold and non-cold inducible CSPs are involved in various cellular and metabolic processes such as growth and development, osmotic oxidation, starvation, stress tolerance, and host cell invasion. In prokaryotes, cold shock condition reduces cell transcription and translation efficiency. Eukaryotic cold shock domain (CSD) proteins are evolved form of prokaryotic CSPs where CSD is flanked by N- and C-terminal domains. Eukaryotic CSPs are multi-functional proteins. CSPs also act as nucleic acid chaperons by preventing the formation of secondary structures in mRNA at low temperatures. In human, CSD proteins play a crucial role in the progression of breast cancer, colon cancer, lung cancer, and Alzheimer's disease. A well-defined three-dimensional structure of intrinsically disordered regions of CSPs family members is still undetermined. In this article, intrinsic disorder regions of CSPs have been explored systematically to understand the pleiotropic role of the cold shock family of proteins.

Regulated dicing of pre-mir-144 via reshaping of its terminal loop

Although the route to generate microRNAs (miRNAs) is often depicted as a linear series of sequential and constitutive cleavages, we now appreciate multiple alternative pathways as well as diverse strategies to modulate their processing and function. Here, we identify an unusually profound regulatory role of conserved loop sequences in vertebrate pre-mir-144, which are essential for its cleavage by the Dicer RNase III enzyme in human and zebrafish models. Our data indicate that pre-mir-144 dicing is positively regulated via its terminal loop, and involves the ILF3 complex (NF90 and its partner NF45/ILF2). We provide further evidence that this regulatory switch involves reshaping of the pre-mir-144 apical loop into a structure that is appropriate for Dicer cleavage. In light of our recent findings that mir-144 promotes the nuclear biogenesis of its neighbor mir-451, these data extend the complex hierarchy of nuclear and cytoplasmic regulatory events that can control the maturation of clustered miRNAs.

Adipose-derived exosomes block muscular stem cell proliferation in aged mouse by delivering miRNA Let-7d-3p that targets transcription factor HMGA2

Sarcopenia is an aging-associated attenuation of muscular volume and strength and is the major cause of frailty and falls in elderly individuals. The number of individuals with sarcopenia is rapidly increasing worldwide; however, little is known about the underlying mechanisms of the disease. Sarcopenia often copresents with obesity, and some patients with sarcopenia exhibit accumulation of peri-organ or intra-organ adipose tissue as ectopic fat deposition, including atrophied skeletal muscle. In this study, we showed that transplantation of the perimuscular adipose tissue (PMAT) to the hindlimb thigh muscles of young mice decreased the number of integrin α7/CD29-double positive muscular stem/progenitor cells and that the reaction was mediated by PMAT-derived exosomes. We also found that the inhibition of cell proliferation was induced by Let-7d-3p miRNA that targets HMGA2, which is an important transcription factor for stem cell self-renewal, in muscular stem/progenitor cells and the composite molecular reaction in aged adipocytes. Reduction of Let-7 miRNA repressor Lin28 A/B and activation of nuclear factor-kappa B signaling can lead to the accumulation of Let-7d-3p in the exosomes of aged PMAT. These findings suggest a novel crosstalk between adipose tissue and skeletal muscle in the development of aging-associated muscular atrophy and indicate that adipose tissue–derived miRNAs may play a key role in sarcopenia.

Selective inhibition of miRNA processing by a herpesvirus-encoded miRNA

Herpesviruses have mastered host cell modulation and immune evasion to augment productive infection, life-long latency and reactivation^1,2. A long appreciated, yet undefined relationship exists between the lytic-latent switch and viral non-coding RNAs^3,4. Here we identify viral microRNA (miRNA)-mediated inhibition of host miRNA processing as a cellular mechanism that human herpesvirus 6A (HHV-6A) exploits to disrupt mitochondrial architecture, evade intrinsic host defences and drive the switch from latent to lytic virus infection. We demonstrate that virus-encoded miR-aU14 selectively inhibits the processing of multiple miR-30 family members by direct interaction with the respective primary (pri)-miRNA hairpin loops. Subsequent loss of miR-30 and activation of the miR-30-p53-DRP1 axis triggers a profound disruption of mitochondrial architecture. This impairs induction of type I interferons and is necessary for both productive infection and virus reactivation. Ectopic expression of miR-aU14 triggered virus reactivation from latency, identifying viral miR-aU14 as a readily druggable master regulator of the herpesvirus lytic-latent switch. Our results show that miRNA-mediated inhibition of miRNA processing represents a generalized cellular mechanism that can be exploited to selectively target individual members of miRNA families. We anticipate that targeting miR-aU14 will provide new therapeutic options for preventing herpesvirus reactivations in HHV-6-associated disorders.

MicroRNA Roles in Cell Reprogramming Mechanisms

Cell reprogramming is a groundbreaking technology that, in few decades, generated a new paradigm in biomedical science. To date we can use cell reprogramming to potentially generate every cell type by converting somatic cells and suitably modulating the expression of key transcription factors. This approach can be used to convert skin fibroblasts into pluripotent stem cells as well as into a variety of differentiated and medically relevant cell types, including cardiomyocytes and neural cells. The molecular mechanisms underlying such striking cell phenotypes are still largely unknown, but in the last decade it has been proven that cell reprogramming approaches are significantly influenced by non-coding RNAs. Specifically, this review will focus on the role of microRNAs in the reprogramming processes that lead to the generation of pluripotent stem cells, neurons, and cardiomyocytes. As highlighted here, non-coding RNA-forced expression can be sufficient to support some cell reprogramming processes, and, therefore, we will also discuss how these molecular determinants could be used in the future for biomedical purposes.

Let7b-5p inhibits insulin secretion and decreases pancreatic β-cell mass in mice

MicroRNAs are crucial regulators for the development, mass and function of pancreatic β-cells. MiRNA dysregulation is associated with β-cell dysfunction and development of diabetes. The members of let7 family are important players in regulating cellular growth and metabolism. In this study we investigated the functional role of let7b-5p in the mouse pancreatic β-cells. We generated pancreatic β-cell-specific let7b-5p transgenic mouse model and analyzed the glucose metabolic phenotype, β-cells mass and insulin secretion in vivo. Luciferase reporter assay, immunofluorescence staining and western blot were carried out to study the target genes of let7b-5p in β-cells. Let7b-5p overexpression impaired the insulin production and secretion of β-cells and resulted impaired glucose tolerance in mice. The overexpressed let7b-5p inhibited pancreatic β-cell proliferation and decreased the expression of cyclin D1 and cyclin D2. Our findings demonstrated that let7b-5p was critical in regulating the proliferation and insulin secretion of pancreatic β-cells.

Interactome analysis illustrates diverse gene regulatory processes associated with LIN28A in human iPS cell-derived neural progenitor cells

A single protein can be multifaceted depending on the cellular contexts and interacting molecules. LIN28A is an RNA-binding protein that governs developmental timing, cellular proliferation, differentiation, stem cell pluripotency, and metabolism. In addition to its best-known roles in microRNA biogenesis, diverse molecular roles have been recognized. In the nervous system, LIN28A is known to play critical roles in proliferation and differentiation of neural progenitor cells (NPCs). We profiled the endogenous LIN28A-interacting proteins in NPCs differentiated from human induced pluripotent stem (iPS) cells using immunoprecipitation and liquid chromatography-tandem mass spectrometry. We identified over 500 LIN28A-interacting proteins, including 156 RNA-independent interactors. Functions of these proteins span a wide range of gene regulatory processes. Prompted by the interactome data, we revealed that LIN28A may impact the subcellular distribution of its interactors and stress granule formation upon oxidative stress. Overall, our analysis opens multiple avenues for elaborating molecular roles and characteristics of LIN28A.

A Focus on Regulatory Networks Linking MicroRNAs, Transcription Factors and Target Genes in Neuroblastoma

Neuroblastoma (NB) is a tumor of the peripheral sympathetic nervous system that substantially contributes to childhood cancer mortality. NB originates from neural crest cells (NCCs) undergoing a defective sympathetic neuronal differentiation and although the starting events leading to the development of NB remain to be fully elucidated, the master role of genetic alterations in key oncogenes has been ascertained: (1) amplification and/or over-expression of MYCN, which is strongly associated with tumor progression and invasion; (2) activating mutations, amplification and/or over-expression of ALK, which is involved in tumor initiation, angiogenesis and invasion; (3) amplification and/or over-expression of LIN28B, promoting proliferation and suppression of neuroblast differentiation; (4) mutations and/or over-expression of PHOX2B, which is involved in the regulation of NB differentiation, stemness maintenance, migration and metastasis. Moreover, altered microRNA (miRNA) expression takes part in generating pathogenetic networks, in which the regulatory loops among transcription factors, miRNAs and target genes lead to complex and aberrant oncogene expression that underlies the development of a tumor. In this review, we have focused on the circuitry linking the oncogenic transcription factors MYCN and PHOX2B with their transcriptional targets ALK and LIN28B and the tumor suppressor microRNAs let-7, miR-34 and miR-204, which should act as down-regulators of their expression. We have also looked at the physiologic role of these genetic and epigenetic determinants in NC development, as well as in terminal differentiation, with their pathogenic dysregulation leading to NB oncogenesis.

The distinct RNA-interaction modes of a small ZnF domain underlay TUT4(7) diverse action in miRNA regulation

TUT4 and the closely related TUT7 are non-templated poly(U) polymerases required at different stages of development, and their mis-regulation or mutation has been linked to important cancer pathologies. While TUT4(7) interaction with its pre-miRNA targets has been characterized in detail, the molecular bases of the broader target recognition process are unclear. Here, we examine RNA binding by the ZnF domains of the protein. We show that TUT4(7) ZnF2 contains two distinct RNA binding surfaces that are used in the interaction with different RNA nucleobases in different targets, i.e that this small domain encodes diversity in TUT4(7) selectivity and molecular function. Interestingly and unlike other well-characterized CCHC ZnFs, ZnF2 is not physically coupled to the flanking ZnF3 and acts independently in miRNA recognition, while the remaining CCHC ZnF of TUT4(7), ZnF1, has lost its intrinsic RNA binding capability. Together, our data suggest that the ZnFs of TUT4(7) are independent units for RNA and, possibly, protein-protein interactions that underlay the protein's functional flexibility and are likely to play an important role in building its interaction network.

Retina stem cells, hopes and obstacles

Retinal degeneration is a major contributor to visual dysfunction worldwide. Although it comprises several eye diseases, loss of retinal pigment epithelial (RPE) and photoreceptor cells are the major contributors to their pathogenesis. Early therapies included diverse treatments, such as provision of anti-vascular endothelial growth factor and many survival and trophic factors that, in some cases, slow down the progression of the degeneration, but do not effectively prevent it. The finding of stem cells (SC) in the eye has led to the proposal of cell replacement strategies for retina degeneration. Therapies using different types of SC, such as retinal progenitor cells (RPCs), embryonic SC, pluripotent SCs (PSCs), induced PSCs (iPSCs), and mesenchymal stromal cells, capable of self-renewal and of differentiating into multiple cell types, have gained ample support. Numerous preclinical studies have assessed transplantation of SC in animal models, with encouraging results. The aim of this work is to revise the different preclinical and clinical approaches, analyzing the SC type used, their efficacy, safety, cell attachment and integration, absence of tumor formation and immunorejection, in order to establish which were the most relevant and successful. In addition, we examine the questions and concerns still open in the field. The data demonstrate the existence of two main approaches, aimed at replacing either RPE cells or photoreceptors. Emerging evidence suggests that RPCs and iPSC are the best candidates, presenting no ethical concerns and a low risk of immunorejection. Clinical trials have already supported the safety and efficacy of SC treatments. Serious concerns are pending, such as the risk of tumor formation, lack of attachment or integration of transplanted cells into host retinas, immunorejection, cell death, and also ethical. However, the amazing progress in the field in the last few years makes it possible to envisage safe and effective treatments to restore vision loss in a near future.

Nonenzymatic DNA-Based Fluorescence Biosensor Combining Carbon Dots and Graphene Oxide with Target-Induced DNA Strand Displacement for microRNA Detection

Based on a fluorescence "on-off-on" strategy, we fabricated a simple and highly sensitive DNA-based fluorescence biosensor for the detection of micro (mi)RNA from carbon dots (CDs) and graphene oxide (GO) without complicated and time-consuming operations. CDs were successfully synthesized and conjugated to the end of a single-stranded fuel DNA that was adsorbed onto the surface of GO through π-π stacking, resulting in fluorescence quenching. In the presence of the target miRNA let-7a, the fuel DNA was desorbed from the GO surface, and fluorescence was restored through two successive toehold-mediated strand displacement reactions on double-stranded DNA-modified gold nanoparticles. The target miRNA let-7a was recycled, leading to signal amplification. The concentration of let-7a was proportional to the degree of fluorescence recovery. Under optimal conditions, there was a good linear relationship between the relative fluorescence intensity and let-7a concentration in the range of 0.01-1 nM, with a detection limit of 7.8 pM. With its advantages of signal amplification and high biocompatibility, this fluorescence sensing strategy can be applied to the detection of a variety of target miRNAs and can guide the design of novel biosensors with improved properties.

Specificity, Safety, Efficacy of EGFRvIII-Retargeted Oncolytic HSV for Xenotransplanted Human Glioblastoma

Glioblastoma is a lethal primary brain tumor lacking effective therapy. The secluded onset site, combined with the infiltrative properties of this tumor, require novel targeted therapies. In this scenario, the use of oncolytic viruses retargeted to glioblastoma cells and able to spread across the tumor cells represent an intriguing treatment strategy. Here, we tested the specificity, safety and efficacy of R-613, the first oncolytic HSV fully retargeted to EGFRvIII, a variant of the epidermal growth factor receptor carrying a mutation typically found in glioblastoma. An early treatment with R-613 on orthotopically transplanted EGFRvIII-expressing human glioblastoma significantly increased the median survival time of mice. In this setting, the growth of human glioblastoma xenotransplants was monitored by a secreted luciferase reporter and showed that R-613 is able to substantially delay the development of the tumor masses. When administered as late treatment to a well-established glioblastomas, R-613 appeared to be less effective. Notably the uninfected tumor cells derived from the explanted tumor masses were still susceptible to R-613 infection ex vivo, thus suggesting that multiple treatments could enhance R-613 therapeutic efficacy, making R-613 a promising oncolytic HSV candidate for glioblastoma treatment.

SALL4 and microRNA: The Role of Let-7

SALL4 is a zinc finger transcription factor that belongs to the spalt-like (SALL) gene family. It plays important roles in the maintenance of self-renewal and pluripotency of embryonic stem cells, and its expression is repressed in most adult organs. SALL4 re-expression has been observed in different types of human cancers, and dysregulation of SALL4 contributes to the pathogenesis, metastasis, and even drug resistance of multiple cancer types. Surprisingly, little is known regarding how SALL4 expression is controlled, but recently microRNAs (miRNAs) have emerged as important regulators of SALL4. Due to the ability of regulating targets differentially in specific tissues, and recent advances in systemic and organ specific miRNA delivery mechanisms, miRNAs have emerged as promising therapeutic targets for cancer treatment. In this review, we summarize current knowledge of the interaction between SALL4 and miRNAs in mammalian development and cancer, paying particular attention to the emerging roles of the Let-7/Lin28 axis. In addition, we discuss the therapeutic prospects of targeting SALL4 using miRNA-based strategies, with a focus on the Let-7/LIN28 axis.

NANOG gene suppression and replacement of let-7 modulate the stemness, invasion, and apoptosis in breast cancer

In the treatment of breast cancer (BC), as an important type of cancer in women, the specific cells, called cancer stem cells (CSCs), are the reason of failure and metastasis. So, targeting CSCs can be used as a novel strategy in cancer therapy in addition to common therapeutic strategies. According to the importance of CSCs, we tried to find a correlation between stemness and metastatic characteristics of BC cells, to address whether CSCs are a potential target for cancer therapy. Here, we evaluated the NANOG inhibition by siRNA and the increase of Let-7a levels by miRNA mimic in breast cancer cells and the effects of these changes on biologic aspects like cell apoptosis, stemness and invasion. Our results showed that the inhibition of NANOG combined with Let-7a restoration contributed to significant decrease in malignant phenotypes and stemness feature of BC cells. In conclusion, these findings showed that the combination of Let-7a miRNA mimic and Nanog siRNA could be exploited as a new treatment strategy to improve the cancer therapy outcome.

The Role of microRNA Let-7d in Female Malignancies and Diseases of the Female Reproductive Tract

microRNAs are small noncoding RNAs that regulate gene expression at the posttranscriptional level. Let-7d is a microRNA of the conserved let-7 family that is dysregulated in female malignancies including breast cancer, ovarian cancer, endometrial cancer, and cervical cancer. Moreover, a dysregulation is observed in endometriosis and pregnancy-associated diseases such as preeclampsia and fetal growth restriction. Let-7d expression is regulated by cytokines and steroids, involving transcriptional regulation by OCT4, MYC and p53, as well as posttranscriptional regulation via LIN28 and ADAR. By downregulating a wide range of relevant mRNA targets, let-7d affects cellular processes that drive disease progression such as cell proliferation, apoptosis (resistance), angiogenesis and immune cell function. In an oncological context, let-7d has a tumor-suppressive function, although some of its functions are context-dependent. Notably, its expression is associated with improved therapeutic responses to chemotherapy in breast and ovarian cancer. Studies in mouse models have furthermore revealed important roles in uterine development and function, with implications for obstetric diseases. Apart from a possible utility as a diagnostic blood-based biomarker, pharmacological modulation of let-7d emerges as a promising therapeutic concept in a variety of female disease conditions.

Lin28 paralogs regulate lung branching morphogenesis

The molecular mechanisms that govern the choreographed timing of organ development remain poorly understood. Our investigation of the role of the Lin28a and Lin28b paralogs during the developmental process of branching morphogenesis establishes that dysregulation of Lin28a/b leads to abnormal branching morphogenesis in the lung and other tissues. Additionally, we find that the Lin28 paralogs, which regulate post-transcriptional processing of both mRNAs and microRNAs (miRNAs), predominantly control mRNAs during the initial phases of lung organogenesis. Target mRNAs include Sox2, Sox9, and Etv5, which coordinate lung development and differentiation. Moreover, we find that functional interactions between Lin28a and Sox9 are capable of bypassing branching defects in Lin28a/b mutant lungs. Here, we identify Lin28a and Lin28b as regulators of early embryonic lung development, highlighting the importance of the timing of post-transcriptional regulation of both miRNAs and mRNAs at distinct stages of organogenesis.

The timing of organogenesis is poorly understood. Here, Osborne et al. show that the Lin28 paralogs (Lin28a and Lin28b) regulate branching morphogenesis in a let-7-independent manner by directly binding to the mRNAs of Sox2, Sox9, and Etv5 to enhance their post-transcriptional processing.

YB1 regulates miR-205/200b-ZEB1 axis by inhibiting microRNA maturation in hepatocellular carcinoma

BACKGROUND

Y-box binding protein 1 (YB1 or YBX1) plays a critical role in tumorigenesis and cancer progression. However, whether YB1 affects malignant transformation by modulating non-coding RNAs remains largely unknown. This study aimed to investigate the relationship between YB1 and microRNAs and reveal the underlying mechanism by which YB1 impacts on tumor malignancy via miRNAs-mediated regulatory network.

METHODS

The biological functions of YB1 in hepatocellular carcinoma (HCC) cells were investigated by cell proliferation, wound healing, and transwell invasion assays. The miRNAs dysregulated by YB1 were screened by microarray analysis in HCC cell lines. The regulation of YB1 on miR-205 and miR-200b was determined by quantitative real-time PCR, dual-luciferase reporter assay, RNA immunoprecipitation, and pull-down assay. The relationships of YB1, DGCR8, Dicer, TUT4, and TUT1 were identified by pull-down and coimmunoprecipitation experiments. The cellular co-localization of YB1, DGCR8, and Dicer were detected by immunofluorescent staining. The in vivo effect of YB1 on tumor metastasis was determined by injecting MHCC97H cells transduced with YB1 shRNA or shControl via the tail vein in nude BALB/c mice. The expression levels of epithelial to mesenchymal transition markers were detected by immunoblotting and immunohistochemistry assays.

RESULTS

YB1 promoted HCC cell migration and tumor metastasis by regulating miR-205/200b-ZEB1 axis partially in a Snail-independent manner. YB1 suppressed miR-205 and miR-200b maturation by interacting with the microprocessors DGCR8 and Dicer as well as TUT4 and TUT1 via the conserved cold shock domain. Subsequently, the downregulation of miR-205 and miR-200b enhanced ZEB1 expression, thus leading to increased cell migration and invasion. Furthermore, statistical analyses on gene expression data from HCC and normal liver tissues showed that YB1 expression was positively associated with ZEB1 expression and remarkably correlated with clinical prognosis.

CONCLUSION

This study reveals a previously undescribed mechanism by which YB1 promotes cancer progression by regulating the miR-205/200b-ZEB1 axis in HCC cells. Furthermore, these results highlight that YB1 may play biological functions via miRNAs-mediated gene regulation, and it can serve as a potential therapeutic target in human cancers.

LncRNA TCONS_00023297 Regulates the Balance of Osteogenic and Adipogenic Differentiation in Bone Marrow Mesenchymal Stem Cells and the Coupling Process of Osteogenesis and Angiogenesis

Long noncoding RNA (lncRNA) is a noncoding RNA with a length of more than 200 bases. It plays an important role in the occurrence and development of diseases. Research on lncRNAs has received increasing attention. Bone is an important organ of the human body. As the population ages, the incidence of osteoporosis gradually increases. The mechanism of action of lncRNAs in the development of osteoporosis is unclear. The imbalance between osteogenic and adipogenic differentiation in bone marrow mesenchymal stem cells (hBMSCs) and the coupling process of osteogenesis and angiogenesis plays an important role in the development of osteoporosis. Therefore, this study focused on the mechanism by which lncRNAs regulate the osteogenic differentiation of bone marrow mesenchymal stem cells and the mechanism of action of lncRNAs in bone metabolism. The expression of lncRNAs in the osteogenic differentiation of hBMSCs was detected by lncRNA microarray. Real-time quantitative PCR was used to detect the expression changes of lncRNA and osteogenic genes during hBMSC osteogenic and adipogenic differentiation. The ceRNA mechanisms were detected by RIP and luciferase reporter gene assays. The effect of lncRNAs on the osteogenesis–angiogenesis coupling process was detected by Transwell assays. TCONS_00023297 increased expression during osteogenic differentiation; TCONS_00023297 overexpression promoted osteogenic differentiation of hBMSCs; BMP2 regulated TCONS_00023297 expression in a concentration- and time-dependent manner; TCONS_00023297 regulated miR-608 via a ceRNA mechanism; TCONS_00023297 inhibited hBMSC adipogenic differentiation; and TCONS_00023297 promoted VEGF secretion by hBMSCs. TCONS_00023297 regulates osteogenic differentiation, adipogenic differentiation, and osteogenic–angiogenic coupling of hBMSCs via the TCONS_00023297/miR-608/RUNX2/SHH signaling axis.

Developing the right tools for the job: Lin28 regulation of early life T-cell development and function

T cells comprise a functionally heterogeneous cell population that has important roles in the immune system. While T cells are broadly considered to be a component of the antigen-specific adaptive immune response, certain T-cell subsets display innate-like effector characteristics whereas others perform immunosuppressive functions. These functionally diverse T-cell populations preferentially arise at different stages of ontogeny and are tailored to the immunological priorities of the organism over time. Many differences in early life versus adult T-cell phenotypes can be attributed to the cell-intrinsic properties of the distinct progenitors that seed the thymus throughout development. It is becoming clear that Lin28, an evolutionarily conserved, heterochronic RNA-binding protein that is differentially expressed among early life and adult hematopoietic progenitor cells, plays a substantial role in influencing early T-cell development and function. Here, we discuss the mechanisms by which Lin28 shapes the T-cell landscape to protect the developing fetus and newborn. Manipulation of the Lin28 gene regulatory network is being considered as one means of improving hematopoietic stem cell transplant outcomes; as such, understanding the impact of Lin28 on T-cell function is of clinical relevance.