The RNA-binding protein HuR in human cancer: A friend or foe?

Genus Physalis L.: A review of resources and cultivation, chemical composition, pharmacological effects and applications

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Physalis L. (Solanaceae) is commonly used in the treatment of dermatitis, leprosy, bronchitis, pneumonia, hepatitis and rheumatism in China and other Asian countries.

AIM OF THE REVIEW

This article reviews the resources, cultivation, phytochemistry, pharmacological properties, and applications of Physalis L., and proposes further research strategies to enhance its therapeutic potential in treating various human diseases.

MATERIALS AND METHODS

We conducted a systematic search of electronic databases, including CNKI, SciFinder and PubMed, using the term "Physalis L." to collect information on the resources, phytochemistry, pharmacological activities, and applications of Physalis L. in China during the past ten years (2013.1-2023.1).

RESULTS

So far, a variety of chemical constituents have been isolated and identified from Physalis L. mainly including steroids, flavonoids, and so on. Various pharmacological activities were evaluated by studying different extracts of Physalis L., these activities include anti-inflammatory, antibacterial, antioxidant, antiviral, antineoplastic, and other aspects.

CONCLUSION

Physalis L. occupies an important position in the traditional medical system. It is cost-effective and is a significant plant with therapeutic applications in modern medicine. However, further in-depth studies are needed to determine the medical use of this plant resources and cultivation, chemical composition, pharmacological effects and applications.

Tanshinone IIA suppresses ferroptosis to attenuate renal podocyte injury in diabetic nephropathy through the embryonic lethal abnormal visual-like protein 1 and acyl-coenzyme A synthetase long-chain family member 4 signaling pathway

AIMS/INTRODUCTION

Tanshinone IIA (TIIA) is one of the main components of the root of the red-rooted Salvia miltiorrhiza Bunge. However, the molecular mechanisms underlying TIIA-mediated protective effects in diabetic nephropathy (DN) are still unclear.

MATERIALS AND METHODS

High glucose (HG)-induced mouse podocyte cell line (MPC5) cells were used as the in vitro model of DN and treated with TIIA. Cell viability, proliferation and apoptosis were detected using 3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide, 5-ethynyl-2'-deoxyuridine and flow cytometry assays. The protein levels were assessed using western blot assay. The levels of inflammatory factors were deleted by enzyme-linked immunoassay. Fe+ level, reactive oxygen species, malondialdehyde and glutathione products were detected using special assay kits. After ENCORI prediction, the interaction between embryonic lethal abnormal visual-like protein 1 (ELAVL1) and acyl-coenzyme A synthetase long-chain family member 4 (ACSL4) was verified using co-immunoprecipitation assay and dual-luciferase reporter assays. ACSL4 messenger ribonucleic acid expression was measured using real-time quantitative polymerase chain reaction.

RESULTS

TIIA repressed HG-induced MPC5 cell apoptosis, inflammatory response and ferroptosis. ACSL4 upregulation relieved the repression of TIIA on HG-mediated MPC5 cell injury and ferroptosis. ELAVL1 is bound with ACSL4 to positively regulate the stability of ACSL4 messenger ribonucleic acid. TIIA hindered HG-triggered MPC5 cell injury and ferroptosis by regulating the ELAVL1-ACSL4 pathway. TIIA blocked DN progression in in vivo research.

CONCLUSION

TIIA treatment restrained HG-caused MPC5 cell injury and ferroptosis partly through targeting the ELAVL1-ACSL4 axis, providing a promising therapeutic target for DN treatment.

Inflammation as a driver of hematological malignancies

Hematopoiesis is a tightly regulated process that produces all adult blood cells and immune cells from multipotent hematopoietic stem cells (HSCs). HSCs usually remain quiescent, and in the presence of external stimuli like infection or inflammation, they undergo division and differentiation as a compensatory mechanism. Normal hematopoiesis is impacted by systemic inflammation, which causes HSCs to transition from quiescence to emergency myelopoiesis. At the molecular level, inflammatory cytokine signaling molecules such as tumor necrosis factor (TNF), interferons, interleukins, and toll-like receptors can all cause HSCs to multiply directly. These cytokines actively encourage HSC activation, proliferation, and differentiation during inflammation, which results in the generation and activation of immune cells required to combat acute injury. The bone marrow niche provides numerous soluble and stromal cell signals, which are essential for maintaining normal homeostasis and output of the bone marrow cells. Inflammatory signals also impact this bone marrow microenvironment called the HSC niche to regulate the inflammatory-induced hematopoiesis. Continuous pro-inflammatory cytokine and chemokine activation can have detrimental effects on the hematopoietic system, which can lead to cancer development, HSC depletion, and bone marrow failure. Reactive oxygen species (ROS), which damage DNA and ultimately lead to the transformation of HSCs into cancerous cells, are produced due to chronic inflammation. The biological elements of the HSC niche produce pro-inflammatory cytokines that cause clonal growth and the development of leukemic stem cells (LSCs) in hematological malignancies. The processes underlying how inflammation affects hematological malignancies are still not fully understood. In this review, we emphasize the effects of inflammation on normal hematopoiesis, the part it plays in the development and progression of hematological malignancies, and potential therapeutic applications for targeting these pathways for therapy in hematological malignancies.

TGF-β-activated circRYK drives glioblastoma progression by increasing VLDLR mRNA expression and stability in a ceRNA- and RBP-dependent manner

BACKGROUND

The TGF-β signalling pathway is intricately associated with the progression of glioblastoma (GBM). The objective of this study was to examine the role of circRNAs in the TGF-β signalling pathway.

METHODS

In our research, we used transcriptome analysis to search for circRNAs that were activated by TGF-β. After confirming the expression pattern of the selected circRYK, we carried out in vitro and in vivo cell function assays. The underlying mechanisms were analysed via RNA pull-down, luciferase reporter, and RNA immunoprecipitation assays.

RESULTS

CircRYK expression was markedly elevated in GBM, and this phenotype was strongly associated with a poor prognosis. Functionally, circRYK promotes epithelial-mesenchymal transition and GSC maintenance in GBM. Mechanistically, circRYK sponges miR-330-5p and promotes the expression of the oncogene VLDLR. In addition, circRYK could enhance the stability of VLDLR mRNA via the RNA-binding protein HuR.

CONCLUSION

Our findings show that TGF-β promotes epithelial-mesenchymal transition and GSC maintenance in GBM through the circRYK-VLDLR axis, which may provide a new therapeutic target for the treatment of GBM.

CircNUP54 promotes hepatocellular carcinoma progression via facilitating HuR cytoplasmic export and stabilizing BIRC3 mRNA

Circular RNAs (circRNAs) have been implicated in tumorigenesis and progression of various cancers. However, the underlying mechanisms of circRNAs in hepatocellular carcinoma (HCC) have not been fully elucidated. Herein, a new oncogenic circRNA, hsa_circ_0070039 (circNUP54), was identified to be significantly upregulated in HCC through circRNA sequencing. As verified in 68 HCC samples, circNUP54 overexpression was correlated with aggressive cancerous behaviors and poor outcomes. Moreover, the function experiments showed that knockdown of circNUP54 inhibited the malignant progression of HCC in vitro and in vivo, whereas overexpression of circNUP54 had the opposite role. Mechanistic investigations carried out by RNA pull-down, RNA immunoprecipitation, and immunofluorescence revealed that circNUP54 interacted with the RNA-binding protein Hu-antigen R (HuR) and promoted its cytoplasmic export. The cytoplasmic accumulation of HuR stabilized the downstream BIRC3 mRNA through its binding to the 3' UTR region. Consequently, the encoded protein of BIRC3, cellular inhibitor of apoptosis 2 (cIAP2), proceeded to activate the NF-κB signal pathway and ultimately contributed to HCC progression. In addition, depletion of BIRC3 rescued the pro-tumorigenic effect of circNUP54 on HCC cells. Overall, this study demonstrated that circNUP54 facilitates HCC progression via regulating the HuR/BIRC3/NF-κB axis, which may serve as a promising therapeutic target for HCC treatment.

HuR promotes castration-resistant prostate cancer progression by altering ERK5 activation via posttranscriptional regulation of BCAT1

BACKGROUND

Castration-resistant prostate cancer (CRPC) is refractory to hormone treatment, and the underlying mechanism has not been fully elucidated. This study aimed to clarify the role and mechanism of Human antigen R (HuR) as a therapeutic target for CRPC progression.

METHODS

HuR was knocked out by Cas9 or inhibited by the HuR-specific inhibitor KH-3 in CRPC cell lines and in a mouse xenograft model. The effects of HuR inhibition on tumour cell behaviors and signal transduction were examined by proliferation, transwell, and tumour xenograft assays. Posttranscriptional regulation of BCAT1 by HuR was determined by half-life and RIP assays.

RESULTS

HuR knockout attenuated the proliferation, migration, and invasion of PC3 and DU145 cells in vitro and inhibited tumour progression in vivo. Moreover, BCAT1 was a direct target gene of HuR and mediated the oncogenic effect of HuR on CRPC. Mechanistically, HuR directly interacted with BCAT1 mRNA and upregulated BCAT1 expression by increasing the stability and translation of BCAT1, which activated ERK5 signalling. Additionally, the HuR-specific inhibitor KH-3 attenuated CRPC progression by disrupting the HuR-BCAT1 interaction.

CONCLUSIONS

We confirmed that the HuR/BCAT1 axis plays a crucial role in CRPC progression and suggest that inhibiting the HuR/BCAT1 axis is a promising therapeutic approach for suppressing CRPC progression.

CSDE1 Intracellular Distribution as a Biomarker of Melanoma Prognosis

RNA-binding proteins are emerging as critical modulators of oncogenic cell transformation, malignancy and therapy resistance. We have previously found that the RNA-binding protein Cold Shock Domain containing protein E1 (CSDE1) promotes invasion and metastasis of melanoma, the deadliest form of skin cancer and also a highly heterogeneous disease in need of predictive biomarkers and druggable targets. Here, we design a monoclonal antibody useful for IHC in the clinical setting and use it to evaluate the prognosis potential of CSDE1 in an exploratory cohort of 149 whole tissue sections including benign nevi and primary tumors and metastasis from melanoma patients. Contrary to expectations for an oncoprotein, we observed a global decrease in CSDE1 levels with increasing malignancy. However, the CSDE1 cytoplasmic/nuclear ratio exhibited a positive correlation with adverse clinical features of primary tumors and emerged as a robust indicator of progression free survival in cutaneous melanoma, highlighting the potential of CSDE1 as a biomarker of prognosis. Our findings provide a novel feature for prognosis assessment and highlight the intricacies of RNA-binding protein dynamics in cancer progression.

UBE4B regulates p27 expression in A549 NSCLC cells through regulating the interaction of HuR and the p27 5' UTR

Ubiquitination factor E4B (UBE4B) has a tumor-promoting effect, demonstrated by its aberrant expression in various types of cancers, and in vitro studies have shown that the retardation of cancer cell proliferation can be induced by targeting UBE4B. However, the molecular pathways through which UBE4B exerts its oncogenic activities have not yet been clearly identified and existing knowledge is limited to p53 and its subsequent downstream targets. In this study, we demonstrated that UBE4B regulates p27 expression in A549 cells via the cap-independent translation pathway following treatment with rapamycin and cycloheximide (CHX). Subsequently, we identified that UBE4B regulates p27 translation by regulating the interaction between human antigen R (HuR) and the p27 internal ribosomal entry site (IRES). First, UBE4B interacts with HuR, which inhibits p27 translation through the IRES. Secondly, the interaction between HuR and the p27 IRES was diminished by UBE4B depletion and enhanced by UBE4B overexpression. Finally, HuR depletion-induced growth retardation, accompanied by p27 accumulation, was restored by UBE4B overexpression. Collectively, these results suggest that the oncogenic properties of UBE4B in A549 cells are mediated by HuR, suggesting the potential of targeting the UBE4B-HuR-p27 axis as a therapeutic strategy for lung cancer.

Circular RNA RHBDD1 regulates tumorigenicity and ferroptosis in colorectal cancer by mediating the ELAVL1/SCD mRNA interaction

Circular RNAs (circRNAs) are covalently closed noncoding RNA molecules that play multiple roles in tumorigenesis and metastasis. Ferroptosis is an iron-dependent, regulated form of cell death and has emerged as a promising target for cancer treatment. However, whether and how circRNAs regulate ferroptotic cell death in colorectal cancer (CRC) remains largely unknown. Three circRNA microarrays were used to screen differentially expressed circRNAs in CRC tissues. A series of functional experiments were conducted to investigate the effects of circRNA on CRC cell proliferation, migration and ferroptosis. We found that hsa_circ_0058495 (circRHBDD1), a novel circRNA, was significantly upregulated in colorectal cancer tissues and cells. The expression levels of circRHBDD1 in serum samples were strongly associated with the advancement of CRC. Silencing of circRHBDD1 remarkably suppressed the proliferation and migration of CRC cells in vitro. Moreover, the depletion of circRHBDD1 notably increased ferroptotic cell death and enhanced RSL3-induced ferroptosis in CRC cells. Mechanistically, circRHBDD1 upregulated the expression of stearoyl-CoA desaturase (SCD), a ferroptosis suppressor mediating lipid remodelling, by enhancing the ELAVL1/SCD mRNA interaction. Finally, circRHBDD1 knockdown repressed the tumorigenesis and ferroptosis of CRC cells in vivo. In conclusion, circRHBDD1 facilitates tumour progression and obstructs ferroptosis in CRC by regulating SCD expression in an ELAVL1-dependent manner.

Dynamic proximity interaction profiling suggests that YPEL2 is involved in cellular stress surveillance

YPEL2 is a member of the evolutionarily conserved YPEL family involved in cellular proliferation, mobility, differentiation, senescence, and death. However, the mechanism by which YPEL2, or YPEL proteins, mediates its effects is largely unknown. Proteins perform their functions in a network of proteins whose identities, amounts, and compositions change spatiotemporally in a lineage-specific manner in response to internal and external stimuli. Here, we explored interaction partners of YPEL2 by using dynamic TurboID-coupled mass spectrometry analyses to infer a function for the protein. Our results using inducible transgene expressions in COS7 cells indicate that proximity interaction partners of YPEL2 are mainly involved in RNA and mRNA metabolic processes, ribonucleoprotein complex biogenesis, regulation of gene silencing by miRNA, and cellular responses to stress. We showed that YPEL2 interacts with the RNA-binding protein ELAVL1 and the selective autophagy receptor SQSTM1. We also found that YPEL2 localizes stress granules in response to sodium arsenite, an oxidative stress inducer, which suggests that YPEL2 participates in stress granule-related processes. Establishing a point of departure in the delineation of structural/functional features of YPEL2, our results suggest that YPEL2 may be involved in stress surveillance mechanisms.

The critical roles of lnc-GLYATL2-2/PD-L1 axis in immune microenvironment and the clinical value of intracranial chordomas

Intracranial chordomas (ICs) are associated with a poor prognosis due to low total resection rates and high recurrence rates. However, the role of immunotherapy in ICs remains unknown. RNA sequencing and immunohistochemical staining were performed on IC tissues and normal tissues, and the long noncoding RNA (lncRNA) lnc-GLYATL2-2 was identified. The results indicated that high expression of lnc-GLYATL2-2 was positively correlated with the tumor-infiltrating lymphocyte (TIL) markers CD4 and Foxp3, negatively correlated with CD8, and positively correlated with the expression of the immune checkpoint molecules programmed death receptor-1 (PD-1) and programmed death ligand 1 (PD-L1). Additionally, Kaplan-Meier and univariate or multivariate Cox regression analyses revealed the predictive value of lnc-GLYATL2-2 for survival based on clinical data from patients with ICs. A high expression level of lnc-GLYATL2-2 is potentially correlated with a suppressive tumor immune microenvironment and adverse clinical outcomes in IC patients. Mechanistically, the upregulation of lnc-GLYATL2-2 can result in increased cytoplasmic levels of ELAVL1, leading to enhanced binding to the 3'-UTR of PD-L1 mRNA and maintenance of its stability. In contrast, lnc-GLYATL2-2 can directly interact with the PD-L1 protein to prevent degradation, thereby promoting high levels of PD-L1 expression simultaneously at the transcriptional and translational levels in chordoma cells. These results provide a new perspective on the diagnosis and prognosis of ICs and provide theoretical evidence for immunotherapy in patients with ICs.

Circular RNA circATP9A promotes non-small cell lung cancer progression by interacting with HuR and by promoting extracellular vesicles-mediated macrophage M2 polarization

BACKGROUND

CircRNA is recognized for its significant regulatory function across various cancers. However, its regulatory role in non-small cell lung cancer (NSCLC) is still largely uncharted.

METHODS

Analysis based on public databases is completed using R software. circATP9A was identified by two circRNA datasets of NSCLC from the Gene Expression Omnibus database. To examine the impact of circATP9A on the phenotype of NSCLC, we conducted both in vitro and in vivo functional experiments. The mRNA and protein levels of specific molecules were determined through quantitative real-time PCR and western blot assays. RNA pulldown and RNA immunoprecipitation assays were performed to verify the interaction between RNA and protein. The functional role of extracellular vesicles (EVs)-circATP9A on tumor-associated macrophage (TAM) polarization was assessed using co-culture system and cell flow cytometry.

RESULTS

Here, we elucidates the functional role of circATP9A in NSCLC. We demonstrated that circATP9A can foster the progression of NSCLC through in vivo and in vitro experiments. From a mechanistic standpoint, circATP9A can interact with the HuR protein to form an RNA-protein complex, subsequently amplifying the mRNA and protein levels of the target gene NUCKS1. Further, the PI3K/AKT/mTOR signaling was identified as the downstream pathways of circATP9A/HuR/NUCKS1 axis. More notably, hnRNPA2B1 can mediate the incorporation of circATP9A into EVs. Subsequently, these EVs containing circATP9A induce the M2 phenotype of TAMs, thereby facilitating NSCLC development.

CONCLUSIONS

Our discoveries indicate that circATP9A could serve as a promising diagnostic indicator and a therapeutic target for NSCLC.

YTHDC1 as a tumor progression suppressor through modulating FSP1-dependent ferroptosis suppression in lung cancer

Ferroptosis is a regulated cell death process initiated by iron-dependent phospholipid peroxidation and is mainly suppressed by GPX4-dependent and FSP1-dependent surveillance mechanisms. However, how the ferroptosis surveillance system is regulated during cancer development remains largely unknown. Here, we report that the YTHDC1-mediated m6A epigenetic regulation of FSP1 alleviates the FSP1-dependent ferroptosis suppression that partially contributes to the tumor suppressive role of YTHDC1 in lung cancer progression. YTHDC1 knockdown promoted the lung tumor progression and upregulated FSP1 protein level that resulted in ferroptosis resistance of lung cancer cells. Silencing FSP1 abrogated YTHDC1 knockdown-induced proliferation increase and ferroptosis resistance. Mechanistically, YTHDC1 binding to the m6A sites in the FSP1 3'-UTR recruited the alternative polyadenylation regulator CSTF3 to generate a less stable shorter 3'-UTR contained FSP1 mRNA, whereas YTHDC1 downregulation generated the longer 3'-UTR contained FSP1 mRNA that is stabilized by RNA binding protein HuR and thus led to the enhanced FSP1 protein level. Therefore, our findings identify YTHDC1 as a tumor progression suppressor in lung cancer and a ferroptosis regulator through modulating the FSP1 mRNA stability and thus suggest a ferroptosis-related therapeutic option for YTHDC1high lung cancer.

MiR-326-mediated overexpression of NFIB offsets TGF-β induced epithelial to mesenchymal transition and reverses lung fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is a progressively fatal and incurable disease characterized by the loss of alveolar structures, increased epithelial-mesenchymal transition (EMT), and aberrant tissue repair. In this study, we investigated the role of Nuclear Factor I-B (NFIB), a transcription factor critical for lung development and maturation, in IPF. Using both human lung tissue samples from patients with IPF, and a mouse model of lung fibrosis induced by bleomycin, we showed that there was a significant reduction of NFIB both in the lungs of patients and mice with IPF. Furthermore, our in vitro experiments using cultured human lung cells demonstrated that the loss of NFIB was associated with the induction of EMT by transforming growth factor beta (TGF-β). Knockdown of NFIB promoted EMT, while overexpression of NFIB suppressed EMT and attenuated the severity of bleomycin-induced lung fibrosis in mice. Mechanistically, we identified post-translational regulation of NFIB by miR-326, a miRNA with anti-fibrotic effects that is diminished in IPF. Specifically, we showed that miR-326 stabilized and increased the expression of NFIB through its 3'UTR target sites for Human antigen R (HuR). Moreover, treatment of mice with either NFIB plasmid or miR-326 reversed airway collagen deposition and fibrosis. In conclusion, our study emphasizes the critical role of NFIB in lung development and maturation, and its reduction in IPF leading to EMT and loss of alveolar structures. Our study highlights the potential of miR-326 as a therapeutic intervention for IPF. The schema shows the role of NFIB in maintaining the normal epithelial cell characteristics in the lungs and how its reduction leads to a shift towards mesenchymal cell-like features and pulmonary fibrosis. A In normal lungs, NFIB is expressed abundantly in the epithelial cells, which helps in maintaining their shape, cell polarity and adhesion molecules. However, when the lungs are exposed to factors that induce pulmonary fibrosis, such as bleomycin, or TGF-β, the epithelial cells undergo epithelial to mesenchymal transition (EMT), which leads to a decrease in NFIB. B The mesenchymal cells that arise from EMT appear as spindle-shaped with loss of cell junctions, increased cell migration, loss of polarity and expression of markers associated with mesenchymal cells/fibroblasts. C We designed a therapeutic approach that involves exogenous administration of NFIB in the form of overexpression plasmid or microRNA-326. This therapeutic approach decreases the mesenchymal cell phenotype and restores the epithelial cell phenotype, thus preventing the development or progression of pulmonary fibrosis.

Identification of HuR-RNA Interfering Compounds by Dynamic Combinatorial Chemistry and Fluorescence Polarization

The RNA binding protein HuR regulates the post-transcriptional process of different oncogenes and tumor suppressor genes, and its dysregulation is linked with cancer. Thus, modulating the complex HuR-RNA represents a promising anticancer strategy. To search for novel HuR ligands able to interfere with the HuR-RNA complex, the protein-templated dynamic combinatorial chemistry (pt-DCC) method was utilized. The recombinant RRM1+2 protein construct, which contains essential domains for ligand-HuR binding and exhibits enhanced solubility and stability compared to the native protein, was used for pt-DCC. Seven acylhydrazones with over 80% amplification were identified. The binding of the fragments to HuR extracted from DCC was validated using STD-NMR, and molecular modeling studies revealed the ability of the compounds to bind HuR at the mRNA binding pocket. Notably, three compounds effectively interfered with HuR-RNA binding in fluorescence polarization studies, suggesting their potential as foundational compounds for developing anticancer HuR-RNA interfering agents.

HuR-mediated nucleocytoplasmic translocation of HOTAIR relieves its inhibition of osteogenic differentiation and promotes bone formation

Bone marrow mesenchymal stem cell (BMSC) osteogenic differentiation and osteoblast function play critical roles in bone formation, which is a highly regulated process. Long noncoding RNAs (lncRNAs) perform diverse functions in a variety of biological processes, including BMSC osteogenic differentiation. Although several studies have reported that HOX transcript antisense RNA (HOTAIR) is involved in BMSC osteogenic differentiation, its effect on bone formation in vivo remains unclear. Here, by constructing transgenic mice with BMSC (Prx1-HOTAIR)- and osteoblast (Bglap-HOTAIR)-specific overexpression of HOTAIR, we found that Prx1-HOTAIR and Bglap-HOTAIR transgenic mice show different bone phenotypes in vivo. Specifically, Prx1-HOTAIR mice showed delayed bone formation, while Bglap-HOTAIR mice showed increased bone formation. HOTAIR inhibits BMSC osteogenic differentiation but promotes osteoblast function in vitro. Furthermore, we identified that HOTAIR is mainly located in the nucleus of BMSCs and in the cytoplasm of osteoblasts. HOTAIR displays a nucleocytoplasmic translocation pattern during BMSC osteogenic differentiation. We first identified that the RNA-binding protein human antigen R (HuR) is responsible for HOTAIR nucleocytoplasmic translocation. HOTAIR is essential for osteoblast function, and cytoplasmic HOTAIR binds to miR-214 and acts as a ceRNA to increase Atf4 protein levels and osteoblast function. Bglap-HOTAIR mice, but not Prx1-HOTAIR mice, showed alleviation of bone loss induced by unloading. This study reveals the importance of temporal and spatial regulation of HOTAIR in BMSC osteogenic differentiation and bone formation, which provides new insights into precise regulation as a target for bone loss.

Niclosamide improves cancer immunotherapy by modulating RNA-binding protein HuR-mediated PD-L1 signaling

BACKGROUND

Immune checkpoint blockade (ICB) represents a revolutionary advance in cancer treatment but remains limited success in triple-negative breast cancer (TNBC). Here we aim to explore the mechanism of RNA-binding protein (RBP) HuR in cancer immune evasion by post-transcriptionally regulating PD-L1 and evaluate the potential of HuR inhibition to improve immune response.

METHODS

The binding between HuR and PD-L1 mRNA was determined by ribonucleoprotein immunoprecipitation and RNA pull-down assays. The HuR knockout clones were established by CRISPR/Cas9 technology. The protein levels were assessed by Western blot, immunohistochemistry, and immunocytochemistry. The function and molecular mechanism of HuR-PD-L1 were determined by in vitro T cell activation and killing assay and in vivo efficacy assay.

RESULTS

We found that HuR directly bound to and stabilized PD-L1 mRNA. Knocking out HuR reduced PD-L1 levels and promoted T cell activation. We discovered that niclosamide reduced PD-L1 by inhibiting HuR cytoplasmic translocation, and diminished glycosylation of PD-L1. Niclosamide enhanced T cell-mediated killing of cancer cells and significantly improved the efficacy of anti-PD-1 immunotherapy in two syngeneic animal tumor models.

CONCLUSION

We identified HuR as a novel posttranscriptional regulator of PD-L1, which plays an important role in tumor immune evasion. Niclosamide might be a promising repurposed drug to improve the patient response to immunotherapy by targeting HuR-PD-L1 axis. Our study demonstrates a novel strategy for targeting HuR/PD-L1 and provides the first proof-of-principle for repurposing niclosamide as a HuR inhibitor to overcome cancer immune evasion and improve response to ICB immunotherapy.

Mechanism of tumor-derived extracellular vesicles in prostatic cancer progression through the circFMN2/KLF2/RNF128 axis

Circular RNAs (circRNAs) are a major type of cargos encapsulated in extracellular vesicles (EVs) and regulate the progression of prostatic cancer (PC). This study was conducted to explore the role of tumor-derived EVs in PC cell proliferation, invasion, and migration via shuttle of circRNA formin 2 (circFMN2). RT-qPCR or Western blot assay showed that circFMN2 was upregulated while KLF2 and RNF128 were downregulated in PC tissues and cells. EVs were separated from PC cells and characterized and its internalization in PC cells was examined, which suggested that PC-EVs mediated the shuttle of circFMN2 to upregulate circFMN2 expression in PC cells. PC cell functions were determined by cell counting kit-8, colony formation and Transwell assays, which suggested that PC-EVs fueled the proliferation, invasion, and migration of PC cells. At cellular level, PC-EVs mediated the shuttle of circFMN2 to upregulate circFMN2 expression in PC cells, and circFMN2 binding to HuR decreased the HuR-KLF2 interaction and repressed KLF2 expression, which further reduced the KLF2-RNF128 promoter binding and repressed RNF128 transcription. Overexpression of KLF2/RNF128 ablated the effects of PC-EVs on the proliferation, invasion, and migration of PC cells. The xenograft tumor models and lung/liver metastasis models were established and revealed that PC-EVs accelerated tumorigenesis and metastasis in vivo via delivery of circFMN2 and repression of KLF2/RNF128.

miR-325-3p Reduces Proliferation and Promotes Apoptosis of Gastric Cancer Cells by Inhibiting Human Antigen R

Human antigen R (HuR), also known as ELAVL1, is a widely expressed RNA-binding protein (RBP) that has a significant impact on the development and advancement of tumors. Our previous study found that 5-fluorouracil (5-FU) may impede the proliferation and increase apoptosis in gastric cancer cells by reducing the nucleocytoplasmic shuttling of HuR. However, how posttranscriptional regulation influences HuR functions in gastric cancer remains to be elucidated. Here, we demonstrated that miR-325-3p has the potential to regulate the expression level of HuR by directly binding to its 3'UTR, which in turn led to a significant reduction in proliferation and an increase in apoptosis in gastric cancer cells. In addition, xenograft experiment showed that knockdown of HuR or overexpression of miR-325-3p group exhibited smaller tumor sizes after transplant of gastric cancer cells into zebrafish larvae. Thus, our findings offer new insights into the pathogenesis of gastric cancer and may potentially assist in identifying novel targets for drug therapy.

Circular RNA hsa_circ_0067842 facilitates tumor metastasis and immune escape in breast cancer through HuR/CMTM6/PD-L1 axis

BACKGROUND

Circular RNAs (circRNAs) have been shown to play diverse biological functions in the progression of multiple diseases. However, the impacts of circRNAs on breast cancer (BC) progression remains unclear. Therefore, the objective of this paper is to investigate the role and mechanisms of a functional circRNA in BC metastasis and immune escape.

METHODS

This study used a circRNA microarray and identified a novel circRNA hsa_circ_0067842. The validation and characteristics of hsa_circ_0067842 were investigated using qRT-PCR, sanger sequencing, RNase R treatment, actinomycin D treatment and fluorescence in situ hybridization (FISH). Gain- and loss-of-function assays were performed to evaluate the biological function of hsa_circ_0067842 in BC progression and immune escape. Mechanistically, the interaction between hsa_circ_0067842 and HuR was explored by RNA pull down, mass spectrometry (MS), subcellular component protein extraction and immunofluorescence (IF). The regulatory mechanisms of hsa_circ_0067842/HuR/CMTM6/PD-L1 axis were investigated by qRT-PCR, western blot, FISH, immunoprecipitation and rescue assays.

RESULTS

The expression of hsa_circ_0067842 was upregulated in BC tissues and cells, which was found to be significantly associated with poor prognosis, regardless of other clinical covariates. Function assays showed that hsa_circ_0067842 promoted the migration and invasion capacities of BC cells. Moreover, co-culture experiment with peripheral blood mononuclear cells (PBMCs) showed that hsa_circ_0067842 played a role in the immune escape of BC cells. Mechanistically, our study showed that hsa_circ_0067842 interacted with HuR, affecting its nuclear translocation, thus enhancing the stability of CMTM6. CMTM6 not only enhances the migration and invasion ability of BC cells, but also affects the ubiquitination of PD-L1 and inhibits its degradation.

CONCLUSION

Collectively, our results demonstrated that hsa_circ_0067842 promoted BC progression through the HuR/CMTM6/PD-L1 axis, providing new insight and a potential target for BC prognosis and therapy.

Post-transcriptional dynamics and RNA homeostasis in autophagy and cancer

Autophagy is an essential recycling and quality control pathway which preserves cellular and organismal homeostasis. As a catabolic process, autophagy degrades damaged and aged intracellular components in response to conditions of stress, including nutrient deprivation, oxidative and genotoxic stress. Autophagy is a highly adaptive and dynamic process which requires an intricately coordinated molecular control. Here we provide an overview of how autophagy is regulated post-transcriptionally, through RNA processing events, epitranscriptomic modifications and non-coding RNAs. We further discuss newly revealed RNA-binding properties of core autophagy machinery proteins and review recent indications of autophagy's ability to impact cellular RNA homeostasis. From a physiological perspective, we examine the biological implications of these emerging regulatory layers of autophagy, particularly in the context of nutrient deprivation and tumorigenesis.

Targeting RNA-binding proteins with small molecules: Perspectives, pitfalls and bifunctional molecules

RNA-binding proteins (RBPs) play vital roles in organisms through binding with RNAs to regulate their functions. Small molecules affecting the function of RBPs have been developed, providing new avenues for drug discovery. Herein, we describe the perspectives on developing small molecule regulators of RBPs. The following types of small molecule modulators are of great interest in drug discovery: small molecules binding to RBPs to affect interactions with RNA molecules, bifunctional molecules binding to RNA or RBP to influence their interactions, and other types of molecules that affect the stability of RNA or RBPs. Moreover, we emphasize that the bifunctional molecules may play important roles in small molecule development to overcome the challenges encountered in the process of drug discovery.

Unraveling the complexity of histone-arginine methyltransferase CARM1 in cancer: From underlying mechanisms to targeted therapeutics

Coactivator-associated arginine methyltransferase 1 (CARM1), a type I protein arginine methyltransferase (PRMT), has been widely reported to catalyze arginine methylation of histone and non-histone substrates, which is closely associated with the occurrence and progression of cancer. Recently, accumulating studies have demonstrated the oncogenic role of CARM1 in many types of human cancers. More importantly, CARM1 has been emerging as an attractive therapeutic target for discovery of new candidate anti-tumor drugs. Therefore, in this review, we summarize the molecular structure of CARM1 and its key regulatory pathways, as well as further discuss the rapid progress in better understanding of the oncogenic functions of CARM1. Moreover, we further demonstrate several representative targeted CARM1 inhibitors, especially focusing on demonstrating their designing strategies and potential therapeutic applications. Together, these inspiring findings would shed new light on elucidating the underlying mechanisms of CARM1 and provide a clue on discovery of more potent and selective CARM1 inhibitors for the future targeted cancer therapy.

Downregulation of N6-methyladenosine-modified LINC00641 promotes EMT, but provides a ferroptotic vulnerability in lung cancer

The prognosis of lung cancer is poor with few effective therapies. Targeting ferroptosis is a new promising strategy for cancer therapy. LINC00641 has been involved in several cancers, however, its specific roles in lung cancer treatment remain largely unknown. Here, we reported that LINC00641 was down-regulated in tumor tissues and its downregulation was associated with poor outcomes in lung adenocarcinoma. LINC00641 was localized primarily in the nucleus and was modified by m⁶A. The nuclear m⁶A reader YTHDC1 regulated LINC00641 expression by affecting its stability. We demonstrated that LINC00641 suppressed lung cancer by inhibiting migration and invasion in vitro and metastasis in vivo. Knockdown of LINC00641 upregulated HuR protein level (especially in the cytoplasm), which subsequently increased N-cadherin levels by stabilizing its mRNA, then ultimately promoted EMT. Interestingly, LINC00641 knockdown in lung cancer cells increased the arachidonic acid metabolism and promoted ferroptosis sensitivity. Our findings identified LINC00641 as a tumor suppressor through inhibiting EMT. In another aspect, low expression of LINC00641 caused a ferroptotic vulnerability in lung cancer cells, which may serve as a potential ferroptosis-related therapeutic target for lung cancer.

MCD Diet Modulates HuR and Oxidative Stress-Related HuR Targets in Rats

The endogenous antioxidant defense plays a big part in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), a common metabolic disorder that can lead to serious complications such as cirrhosis and cancer. HuR, an RNA-binding protein of the ELAV family, controls, among others, the stability of MnSOD and HO-1 mRNA. These two enzymes protect the liver cells from oxidative damage caused by excessive fat accumulation. Our aim was to investigate the expression of HuR and its targets in a methionine-choline deficient (MCD) model of NAFLD. To this aim, we fed male Wistar rats with an MCD diet for 3 and 6 weeks to induce NAFLD; then, we evaluated the expression of HuR, MnSOD, and HO-1. The MCD diet induced fat accumulation, hepatic injury, oxidative stress, and mitochondrial dysfunction. A HuR downregulation was also observed in association with a reduced expression of MnSOD and HO-1. Moreover, the changes in the expression of HuR and its targets were significantly correlated with oxidative stress and mitochondrial injury. Since HuR plays a protective role against oxidative stress, targeting this protein could be a therapeutic strategy to both prevent and counteract NAFLD.

Mevalonate improves anti-PD-1/PD-L1 efficacy by stabilizing CD274 mRNA

Mevalonate metabolism plays an important role in regulating tumor growth and progression; however, its role in immune evasion and immune checkpoint modulation remains unclear. Here, we found that non-small cell lung cancer (NSCLC) patients with higher plasma mevalonate response better to anti-PD-(L)1 therapy, as indicated by prolonged progression-free survival and overall survival. Plasma mevalonate levels were positively correlated with programmed death ligand-1 (PD-L1) expression in tumor tissues. In NSCLC cell lines and patient-derived cells, supplementation of mevalonate significantly up-regulated the expression of PD-L1, whereas deprivation of mevalonate reduced PD-L1 expression. Mevalonate increased CD274 mRNA level but did not affect CD274 transcription. Further, we confirmed that mevalonate improved CD274 mRNA stability. Mevalonate promoted the affinity of the AU-rich element-binding protein HuR to the 3'-UTR regions of CD274 mRNA and thereby stabilized CD274 mRNA. By in vivo study, we further confirmed that mevalonate addition enhanced the anti-tumor effect of anti-PD-L1, increased the infiltration of CD8+ T cells, and improved cytotoxic function of T cells. Collectively, our findings discovered plasma mevalonate levels positively correlated with the therapeutic efficacy of anti-PD-(L)1 antibody, and provided the evidence that mevalonate supplementation could be an immunosensitizer in NSCLC.

New Functions of Intracellular LOXL2: Modulation of RNA-Binding Proteins

Lysyl oxidase-like 2 (LOXL2) was initially described as an extracellular enzyme involved in extracellular matrix remodeling. Nevertheless, numerous recent reports have implicated intracellular LOXL2 in a wide variety of processes that impact on gene transcription, development, differentiation, proliferation, migration, cell adhesion, and angiogenesis, suggesting multiple different functions for this protein. In addition, increasing knowledge about LOXL2 points to a role in several types of human cancer. Moreover, LOXL2 is able to induce the epithelial-to-mesenchymal transition (EMT) process-the first step in the metastatic cascade. To uncover the underlying mechanisms of the great variety of functions of intracellular LOXL2, we carried out an analysis of LOXL2's nuclear interactome. This study reveals the interaction of LOXL2 with numerous RNA-binding proteins (RBPs) involved in several aspects of RNA metabolism. Gene expression profile analysis of cells silenced for LOXL2, combined with in silico identification of RBPs' targets, points to six RBPs as candidates to be substrates of LOXL2's action, and that deserve a more mechanistic analysis in the future. The results presented here allow us to hypothesize novel LOXL2 functions that might help to comprehend its multifaceted role in the tumorigenic process.

The kinesin light chain-2, a target of mRNA stabilizing protein HuR, inhibits p53 protein phosphorylation to promote radioresistance in NSCLC

BACKGROUND

Radioresistance hinders radiotherapy for the treatment of lung cancer. Kinesin light chain-2 (KLC2) has been found to be upregulated in lung cancer and also to be associated with poor prognosis. This study aimed to investigate the effect of KLC2 on radiosensitivity in lung cancer.

METHODS

The radioresistant role of KLC2 was determined by colony formation, neutral comet assay, and γH2AX immunofluorescent staining assay. We further verified the function of KLC2 in a xenograft tumor model. The downstream of KLC2 was identified through gene set enrichment analysis and validated by western blot. Finally, we analyzed clinical data from the TCGA database to reveal the upstream transcription factor of KLC2, which was validated by RNA binding protein immunoprecipitation assay.

RESULTS

Here, we found that downregulation of KLC2 could significantly reduce colony formation, increase γH2AX level, and double-stranded DNA breaks in vitro. Meanwhile, overexpressed KLC2 significantly increased the proportion of the S phase in lung cancer cells. KLC2 knockdown could activate P53 pathway, and ultimately promoting radiosensitivity. The mRNA of KLC2 was observed to bind with Hu-antigen R (HuR). The mRNA and protein expression of KLC2 in lung cancer cells was significantly reduced when combined with siRNA-HuR. Interestingly, KLC2 overexpression significantly increased the expression of HuR in lung cancer cells.

CONCLUSION

Taken together, these results indicated that HuR-KLC2 forms a positive feedback loop, which decreases the phosphorylation of p53 and thereby weaken the radiosensitivity of lung cancer cells. Our findings highlight the potential prognosis and therapeutic target value of KLC2 in lung cancer patients treated with radiotherapy.

Exosomes derived from cancer-associated fibroblasts mediate response to cancer therapy

Cancer-associated fibroblasts (CAFs) are the prominent stromal cell population in the tumor microenvironment (TME), which play an indispensable role in cancer progression and response to therapy. CAFs provide communication between tumor cells and surrounding cells by secreting soluble biomolecules and extracellular vesicles (EVs). Exosomes are small membrane-bound EVs that contain various cargos, including growth factors, non-coding RNAs (ncRNAs), cytokines, and chemokines. These biomolecules can be transferred between cells within the TME and alter the behavior of recipient cells. Some studies have shown that exosomes secreted by CAFs contribute to resistance to chemotherapy and radiotherapy. This review focuses on CAF-derived exosomes in different types of tumors, with emphasis on resistance to chemotherapy and radiotherapy.

The Prognostic Role of HuR Varies Between Different Subtypes of Breast Cancer Patients: Data Mining and Retrospective Analysis

Objective

Human-antigen R (HuR) is an RNA-binding protein, which regulates the expression of several oncogenes and tumor suppressor genes through post-transcriptional mechanisms. But the role of HuR in breast cancer remains controversial. The aim of this study was to verify the association between cytoplasmic HuR level and prognosis of breast cancer patients.

Methods

Data mining from the Human Protein Atlas (HPA) and Kaplan-Meier Plotter (KMP) databases was performed. Then, 394 patients with stage I-III primary breast cancer were enrolled between January 2005 and December 2016. We investigated the association between cytoplasmic HuR level and clinicopathological characteristics or survival of these patients. Immunohistochemical analysis was performed to determine HuR expression level. SPSS 21.0 statistical software was used for analysis.

Results

In the HPA and KMP datasets, HuR protein and mRNA expression level were not significantly associated with overall survival of all breast cancer patients enrolled. Results from our 394 patients indicated that higher expression level of cytoplasmic HuR was associated with larger tumor size, lymph node positive, ER negative and triple-negative subtype. For all patients enrolled, the results indicated that compared with HuR negative patients, the DFS (disease-free survival) of HuR 1+ was longer (60.5% vs 78.8, P=0.053, HR=0.616, 95% CI: 0.378-1.005), the P value was borderline. In the triple-negative breast cancer (TNBC) subgroup, HuR positive patients had significantly longer DFS than HuR negative patients (65.5% vs 30.8%, P=0.001, HR=0.345, 95% CI: 0.180-0.658). In the HR+HER2- subgroup, HuR low (0~1+) patients had significantly longer OS than HuR high (2+~3+) patients (97.0% vs 89.5%, P=0.033, HR=2.482, 95% CI: 1.074-5.736).

Conclusion

In conclusion, our results revealed that higher expression level of HuR was related to aggressive biological characteristics which supported the findings from previous researches. In the HR+HER2- subgroup, lower HuR expression level patients had better survival time, while in the TNBC subgroup we got the opposite results. Our work indicated that HuR might play different roles in different breast cancer subtypes.

Small Molecules Targeting the RNA-Binding Protein HuR Inhibit Tumor Growth in Xenografts

The RNA-binding protein Hu antigen R (HuR) is a post-transcriptional regulator critical in several types of diseases, including cancer, making it a promising therapeutic target. We have identified small-molecule inhibitors of HuR through a screening approach used in combination with fragment analysis. A total of 36 new compounds originating from fragment linking or structural optimization were studied to establish structure-activity relationships in the set. Two top inhibitors, 1c and 7c, were further validated by binding assays and cellular functional assays. Both block HuR function by directly binding to the RNA-binding pocket, inhibit cancer cell growth dependence of HuR, and suppress cancer cell invasion. Intraperitoneal administration of inhibitor 1c inhibits tumor growth as a single agent and shows a synergistic effect in combination with chemotherapy docetaxel in breast cancer xenograft models. Mechanistically, 1c interferes with the HuR-TGFB/THBS1 axis.

Novel roles of RNA-binding proteins in drug resistance of breast cancer: from molecular biology to targeting therapeutics

Therapy resistance remains a huge challenge for current breast cancer treatments. Exploring molecular mechanisms of therapy resistance might provide therapeutic targets for patients with advanced breast cancer and improve their prognosis. RNA-binding proteins (RBPs) play an important role in regulating therapy resistance. Here we summarize the functions of RBPs, highlight their tremendously important roles in regulating therapy sensitivity and resistance and we also reveal current therapeutic approaches reversing abnormal functions of RBPs in breast cancer.

HuR inhibition reduces post-ischemic cardiac remodeling by dampening acute inflammatory gene expression and the innate immune response

Myocardial ischemia/reperfusion (I/R) injury and the resulting cardiac remodeling is a common cause of heart failure. The RNA binding protein Human Antigen R (HuR) has been previously shown to reduce cardiac remodeling following both I/R and cardiac pressure overload, but the full extent of the HuR-dependent mechanisms within cells of the myocardium have yet to be elucidated. In this study, we applied a novel small molecule inhibitor of HuR to define the functional role of HuR in the acute response to I/R injury and gain a better understanding of the HuR-dependent mechanisms during post-ischemic myocardial remodeling. Our results show an early (two hours post-I/R) increase in HuR activity that is necessary for early inflammatory gene expression by cardiomyocytes in response to I/R. Surprisingly, despite the reductions in early inflammatory gene expression at two hours post-I/R, HuR inhibition has no effect on initial infarct size at 24-hours post-I/R. However, in agreement with previously published work, we do see a reduction in pathological remodeling and preserved cardiac function at two weeks post-I/R upon HuR inhibition. RNA-sequencing analysis of neonatal rat ventricular myocytes (NRVMs) at two hours post-LPS treatment to model damage associated molecular pattern (DAMP)-mediated activation of toll like receptors (TLRs) demonstrates a broad HuR-dependent regulation of pro-inflammatory chemokine and cytokine gene expression in cardiomyocytes. We show that conditioned media from NRVMs pre-treated with HuR inhibitor loses the ability to induce inflammatory gene expression in bone marrow derived macrophages (BMDMs) compared to NRVMs treated with LPS alone. Functionally, HuR inhibition in NRVMs also reduces their ability to induce endocrine migration of peripheral blood monocytes in vitro and reduces post-ischemic macrophage infiltration to the heart in vivo. In summary, these results suggest a HuR-dependent expression of pro-inflammatory gene expression by cardiomyocytes that leads to subsequent monocyte recruitment and macrophage activation in the post-ischemic myocardium.

Rationally designed inhibitors of the Musashi protein-RNA interaction by hotspot mimicry

RNA-binding proteins (RBPs) are key post-transcriptional regulators of gene expression, and thus underlie many important biological processes. Here, we developed a strategy that entails extracting a "hotspot pharmacophore" from the structure of a protein-RNA complex, to create a template for designing small-molecule inhibitors and for exploring the selectivity of the resulting inhibitors. We demonstrate this approach by designing inhibitors of Musashi proteins MSI1 and MSI2, key regulators of mRNA stability and translation that are upregulated in many cancers. We report this novel series of MSI1/MSI2 inhibitors is specific and active in biochemical, biophysical, and cellular assays. This study extends the paradigm of "hotspots" from protein-protein complexes to protein-RNA complexes, supports the "druggability" of RNA-binding protein surfaces, and represents one of the first rationally-designed inhibitors of non-enzymatic RNA-binding proteins. Owing to its simplicity and generality, we anticipate that this approach may also be used to develop inhibitors of many other RNA-binding proteins; we also consider the prospects of identifying potential off-target interactions by searching for other RBPs that recognize their cognate RNAs using similar interaction geometries. Beyond inhibitors, we also expect that compounds designed using this approach can serve as warheads for new PROTACs that selectively degrade RNA-binding proteins.

Rationally designed inhibitors of the Musashi protein-RNA interaction by hotspot mimicry

RNA-binding proteins (RBPs) are key post-transcriptional regulators of gene expression, and thus underlie many important biological processes. Here, we developed a strategy that entails extracting a "hotspot pharmacophore" from the structure of a protein-RNA complex, to create a template for designing small-molecule inhibitors and for exploring the selectivity of the resulting inhibitors. We demonstrate this approach by designing inhibitors of Musashi proteins MSI1 and MSI2, key regulators of mRNA stability and translation that are upregulated in many cancers. We report this novel series of MSI1/MSI2 inhibitors is specific and active in biochemical, biophysical, and cellular assays. This study extends the paradigm of "hotspots" from protein-protein complexes to protein-RNA complexes, supports the "druggability" of RNA-binding protein surfaces, and represents one of the first rationally-designed inhibitors of non-enzymatic RNA-binding proteins. Owing to its simplicity and generality, we anticipate that this approach may also be used to develop inhibitors of many other RNA-binding proteins; we also consider the prospects of identifying potential off-target interactions by searching for other RBPs that recognize their cognate RNAs using similar interaction geometries. Beyond inhibitors, we also expect that compounds designed using this approach can serve as warheads for new PROTACs that selectively degrade RNA-binding proteins.

Integration of three machine learning algorithms identifies characteristic RNA binding proteins linked with diagnosis, immunity and pyroptosis of IgA nephropathy

Objective: RNA-binding proteins (RBPs) are essential for most post-transcriptional regulatory events, which exert critical roles in nearly all aspects of cell biology. Here, characteristic RBPs of IgA nephropathy were determined with multiple machine learning algorithms.

Methods: Our study included three gene expression datasets of IgA nephropathy (GSE37460, GSE73953, GSE93798). Differential expression of RBPs between IgA nephropathy and normal samples was analyzed via limma, and hub RBPs were determined through MCODE. Afterwards, three machine learning algorithms (LASSO, SVM-RFE, random forest) were integrated to determine characteristic RBPs, which were verified in the Nephroseq database. Immune cell infiltrations were estimated through CIBERSORT. Utilizing ConsensusClusterPlus, IgA nephropathy were classified based on hub RBPs. The potential upstream miRNAs were predicted.

Results: Among 388 RBPs with differential expression, 43 hub RBPs were determined. After integration of three machine learning algorithms, three characteristic RBPs were finally identified (DDX27, RCL1, and TFB2M). All of them were down-regulated in IgA nephropathy than normal specimens, with the excellent diagnostic efficacy. Additionally, they were significantly linked to immune cell infiltrations, immune checkpoints, and pyroptosis-relevant genes. Based on hub RBPs, IgA nephropathy was stably classified as two subtypes (cluster 1 and 2). Cluster 1 exhibited the relatively high expression of pyroptosis-relevant genes and characteristic RBPs. MiR-501-3p, miR-760, miR-502-3p, miR-1224-5p, and miR-107 were potential upstream miRNAs of hub RBPs.

Conclusion: Collectively, our findings determine three characteristic RBPs in IgA nephropathy and two RBPs-based subtypes, and thus provide a certain basis for further research on the diagnosis and pathogenesis of IgA nephropathy.

ELAVL1 promotes prostate cancer progression by interacting with other m6A regulators

N6-Methyladenosine (m6A) imbalance is an important factor in the occurrence and development of prostate cancer (PCa). Many m6A regulators have been found to be significantly dysregulated in PCa. ELAVL1 is an m6A binding protein that can promote the occurrence and development of tumors in an m6A-dependent manner. In this study, we found that most m6A regulators were significantly dysregulated in PCa, and some m6A regulators were associated with the progression-free interval. Mutations and copy number variations of these m6A regulators can alter their expression. However, ELAVL1 mutations were not found in PCa. Nevertheless, ELAVL1 upregulation was closely related to PCa proliferation. High ELAVL1 expression was also related to RNA metabolism. Further experiments showed that ELAVL1 interacted with other m6A regulators and that several m6A regulatory mRNAs have m6A sites that can be recognized by ELAVL1. Additionally, protein–protein interactions occur between ELAVL1 and other m6A regulators. Finally, we found that the dysregulation of ELAVL1 expression occurred in almost all tumors, and interactions between ELAVL1 and other m6A regulators also existed in almost all tumors. In summary, ELAVL1 is an important molecule in the development of PCa, and its interactions with other m6A regulators may play important roles in PCa progression.

Multifaceted Roles of the N6-Methyladenosine RNA Methyltransferase METTL3 in Cancer and Immune Microenvironment

As the most abundant internal mRNA modification in eukaryotic cells, N⁶-methyladenosine (m⁶A) has emerged as an important regulator of gene expression and has a profound impact on cancer initiation and progression. mRNA m⁶A modification is regulated by m⁶A methyltransferases, demethylases and reader proteins to fine tune gene expression at the post-transcriptional level. The most well-studied m⁶A methyltransferase, METTL3, plays critical roles in regulating gene expression and affecting the outcome of various cancers. In this review, we discuss the multifaceted roles of METTL3 in regulating specific molecular signaling pathways in different types of cancers and the recent progress on how METTL3 impacts the tumor immune microenvironment. Finally, we discuss future directions and the potential for therapeutic targeting of METTL3 in cancer treatment.

The Role of E3 Ligase Pirh2 in Disease

The p53-dependent ubiquitin ligase Pirh2 regulates a number of proteins involved in different cancer-associated processes. Targeting the p53 family proteins, Chk2, p27Kip1, Twist1 and others, Pirh2 participates in such cellular processes as proliferation, cell cycle regulation, apoptosis and cellular migration. Thus, it is not surprising that Pirh2 takes part in the initiation and progression of different diseases and pathologies including but not limited to cancer. In this review, we aimed to summarize the available data on Pirh2 regulation, its protein targets and its role in various diseases and pathological processes, thus making the Pirh2 protein a promising therapeutic target.