Hypoxia-Induced Suppression of Alternative Splicing of MBD2 Promotes Breast Cancer Metastasis via Activation of FZD1

Frizzled receptors (FZDs) in Wnt signaling: potential therapeutic targets for human cancers

Frizzled receptors (FZDs) are key contributors intrinsic to the Wnt signaling pathway, activation of FZDs triggering the Wnt signaling cascade is frequently observed in human tumors and intimately associated with an aggressive carcinoma phenotype. It has been shown that the abnormal expression of FZD receptors contributes to the manifestation of malignant characteristics in human tumors such as enhanced cell proliferation, metastasis, chemotherapy resistance as well as the acquisition of cancer stemness. Given the essential roles of FZD receptors in the Wnt signaling in human tumors, this review aims to consolidate the prevailing knowledge on the specific status of FZD receptors (FZD1-10) and elucidate their respective functions in tumor progression. Furthermore, we delineate the structural basis for binding of FZD and its co-receptors to Wnt, and provide a better theoretical foundation for subsequent studies on related mechanisms. Finally, we describe the existing biological classes of small molecule-based FZD inhibitors in detail in the hope that they can provide useful assistance for design and development of novel drug candidates targeted FZDs.

Methyl-CpG binding domain protein 2 (Mbd2) drives breast cancer progression through the modulation of epithelial-to-mesenchymal transition

Methyl-CpG-binding domain protein 2 (Mbd2), a reader of DNA methylation, has been implicated in different types of malignancies, including breast cancer. However, the exact role of Mbd2 in various stages of breast cancer growth and progression in vivo has not been determined. To test whether Mbd2 plays a causal role in mammary tumor growth and metastasis, we performed genetic knockout (KO) of Mbd2 in MMTV-PyMT transgenic mice and compared mammary tumor progression kinetics between the wild-type (PyMT-Mbd2+/+) and KO (PyMT-Mbd2-/-) groups. Our results demonstrated that deletion of Mbd2 in PyMT mice impedes primary tumor growth and lung metastasis at the experimental endpoint (postnatal week 20). Transcriptomic and proteomic analyses of primary tumors revealed that Mbd2 deletion abrogates the expression of several key determinants involved in epithelial-to-mesenchymal transition, such as neural cadherin (N-cadherin) and osteopontin. Importantly, loss of the Mbd2 gene impairs the activation of the PI3K/AKT pathway, which is required for PyMT-mediated oncogenic transformation, growth, and survival of breast tumor cells. Taken together, the results of this study provide a rationale for further development of epigenetic therapies targeting Mbd2 to inhibit the progression of breast cancer.

The Role of Circulating Tumor Cells as a Liquid Biopsy for Cancer: Advances, Biology, Technical Challenges, and Clinical Relevance

Cancer remains a leading cause of mortality worldwide, with metastasis significantly contributing to its lethality. The metastatic spread of tumor cells, primarily through the bloodstream, underscores the importance of circulating tumor cells (CTCs) in oncological research. As a critical component of liquid biopsies, CTCs offer a non-invasive and dynamic window into tumor biology, providing invaluable insights into cancer dissemination, disease progression, and response to treatment. This review article delves into the recent advancements in CTC research, highlighting their emerging role as a biomarker in various cancer types. We explore the latest technologies and methods for CTC isolation and detection, alongside novel approaches to characterizing their biology through genomics, transcriptomics, proteomics, and epigenetic profiling. Additionally, we examine the clinical implementation of these findings, assessing how CTCs are transforming the landscape of cancer diagnosis, prognosis, and management. By offering a comprehensive overview of current developments and potential future directions, this review underscores the significance of CTCs in enhancing our understanding of cancer and in shaping personalized therapeutic strategies, particularly for patients with metastatic disease.

Autophagy-dependent alternative splicing of ribosomal protein S24 produces a more stable isoform that aids in hypoxic cell survival

Cells remodel splicing and translation machineries to mount specialized gene expression responses to stress. Here, we show that hypoxic human cells in 2D and 3D culture models increase the relative abundance of a longer mRNA variant of ribosomal protein S24 (RPS24L) compared to a shorter mRNA variant (RPS24S) by favoring the inclusion of a 22 bp cassette exon. Mechanistically, RPS24L and RPS24S are induced and repressed, respectively, by distinct pathways in hypoxia: RPS24L is induced in an autophagy-dependent manner, while RPS24S is reduced by mTORC1 repression in a hypoxia-inducible factor-dependent manner. RPS24L produces a more stable protein isoform that aids in hypoxic cell survival and growth, which could be exploited by cancer cells in the tumor microenvironment.

HnRNPR-mediated UPF3B mRNA splicing drives hepatocellular carcinoma metastasis

INTRODUCTION

Abnormal alternative splicing (AS) contributes to aggressive intrahepatic invasion and metastatic spread, leading to the high lethality of hepatocellular carcinoma (HCC).

OBJECTIVES

This study aims to investigate the functional implications of UPF3B-S (a truncated oncogenic splice variant) in HCC metastasis.

METHODS

Basescope assay was performed to analyze the expression of UPF3B-S mRNA in tissues and cells. RNA immunoprecipitation, and in vitro and in vivo models were used to explore the role of UPF3B-S and the underlying mechanisms.

RESULTS

We show that splicing factor HnRNPR binds to the pre-mRNA of UPF3B via its RRM2 domain to generate an exon 8 exclusion truncated splice variant UPF3B-S. High expression of UPF3B-S is correlated with tumor metastasis and unfavorable overall survival in patients with HCC. The knockdown of UPF3B-S markedly suppresses the invasive and migratory capacities of HCC cells in vitro and in vivo. Mechanistically, UPF3B-S protein targets the 3'-UTR of CDH1 mRNA to enhance the degradation of CDH1 mRNA, which results in the downregulation of E-cadherin and the activation of epithelial-mesenchymal transition. Overexpression of UPF3B-S enhances the dephosphorylation of LATS1 and the nuclear accumulation of YAP1 to trigger the Hippo signaling pathway.

CONCLUSION

Our findings suggest that HnRNPR-induced UPF3B-S promotes HCC invasion and metastasis by exhausting CDH1 mRNA and modulating YAP1-Hippo signaling. UPF3B-S could potentially serve as a promising biomarker for the clinical management of invasive HCC.

Alternative splicing and related RNA binding proteins in human health and disease

Alternative splicing (AS) serves as a pivotal mechanism in transcriptional regulation, engendering transcript diversity, and modifications in protein structure and functionality. Across varying tissues, developmental stages, or under specific conditions, AS gives rise to distinct splice isoforms. This implies that these isoforms possess unique temporal and spatial roles, thereby associating AS with standard biological activities and diseases. Among these, AS-related RNA-binding proteins (RBPs) play an instrumental role in regulating alternative splicing events. Under physiological conditions, the diversity of proteins mediated by AS influences the structure, function, interaction, and localization of proteins, thereby participating in the differentiation and development of an array of tissues and organs. Under pathological conditions, alterations in AS are linked with various diseases, particularly cancer. These changes can lead to modifications in gene splicing patterns, culminating in changes or loss of protein functionality. For instance, in cancer, abnormalities in AS and RBPs may result in aberrant expression of cancer-associated genes, thereby promoting the onset and progression of tumors. AS and RBPs are also associated with numerous neurodegenerative diseases and autoimmune diseases. Consequently, the study of AS across different tissues holds significant value. This review provides a detailed account of the recent advancements in the study of alternative splicing and AS-related RNA-binding proteins in tissue development and diseases, which aids in deepening the understanding of gene expression complexity and offers new insights and methodologies for precision medicine.

Mechanistic Insights into Alternative Gene Splicing in Oxidative Stress and Tissue Injury

Significance: Oxidative stress (OS) and inflammation are inducers of tissue injury. Alternative splicing (AS) is an essential regulatory step for diversifying the eukaryotic proteome. Human diseases link AS to OS; however, the underlying mechanisms must be better understood. Recent Advances: Genome‑wide profiling studies identify new differentially expressed genes induced by OS-dependent ischemia/reperfusion injury. Overexpression of RNA-binding protein RBFOX1 protects against inflammation. Hypoxia-inducible factor-1α directs polypyrimidine tract binding protein 1 to regulate mouse carcinoembryonic antigen-related cell adhesion molecule 1 (Ceacam1) AS under OS conditions. Heterogeneous nuclear ribonucleoprotein L variant 1 contains an RGG/RG motif that coordinates with transcription factors to influence human CEACAM1 AS. Hypoxia intervention involving short interfering RNAs directed to long-noncoding RNA 260 polarizes M2 macrophages toward an anti-inflammatory phenotype and alleviates OS by inhibiting IL-28RA gene AS. Critical Issues: Protective mechanisms that eliminate reactive oxygen species (ROS) are important for resolving imbalances that lead to chronic inflammation. Defects in AS can cause ROS generation, cell death regulation, and the activation of innate and adaptive immune factors. We propose that AS pathways link redox regulation to the activation or suppression of the inflammatory response during cellular stress. Future Directions: Emergent studies using molecule-mediated RNA splicing are being conducted to exploit the immunogenicity of AS protein products. Deciphering the mechanisms that connect misspliced OS and pathologies should remain a priority. Controlled release of RNA directly into cells with clinical applications is needed as the demand for innovative nucleic acid delivery systems continues to be demonstrated.

Tumor microenvironment-induced tumor cell plasticity: relationship with hypoxic stress and impact on tumor resistance

The role of tumor interaction with stromal components during carcinogenesis is crucial for the design of efficient cancer treatment approaches. It is widely admitted that tumor hypoxic stress is associated with tumor aggressiveness and thus impacts susceptibility and resistance to different types of treatments. Notable biological processes that hypoxia functions in include its regulation of tumor heterogeneity and plasticity. While hypoxia has been reported as a major player in tumor survival and dissemination regulation, the significance of hypoxia inducible factors in cancer stem cell development remains poorly understood. Several reports indicate that the emergence of cancer stem cells in addition to their phenotype and function within a hypoxic tumor microenvironment impacts cancer progression. In this respect, evidence showed that cancer stem cells are key elements of intratumoral heterogeneity and more importantly are responsible for tumor relapse and escape to treatments. This paper briefly reviews our current knowledge of the interaction between tumor hypoxic stress and its role in stemness acquisition and maintenance. Our review extensively covers the influence of hypoxia on the formation and maintenance of cancer stem cells and discusses the potential of targeting hypoxia-induced alterations in the expression and function of the so far known stem cell markers in cancer therapy approaches. We believe that a better and integrated understanding of the effect of hypoxia on stemness during carcinogenesis might lead to new strategies for exploiting hypoxia-associated pathways and their targeting in the clinical setting in order to overcome resistance mechanisms. More importantly, at the present time, efforts are oriented towards the design of innovative therapeutical approaches that specifically target cancer stem cells.

TCAF2 in Pericytes Promotes Colorectal Cancer Liver Metastasis via Inhibiting Cold-Sensing TRPM8 Channel

Hematogenous metastasis is the main approach for colorectal cancer liver metastasis (CRCLM). However, as the gatekeepers in the tumor vessels, the role of TPCs in hematogenous metastasis remains largely unknown, which may be attributed to the lack of specific biomarkers for TPC isolation. Here, microdissection combined with a pericyte medium-based approach is developed to obtain TPCs from CRC patients. Proteomic analysis reveals that TRP channel-associated factor 2 (TCAF2), a partner protein of the transient receptor potential cation channel subfamily M member 8 (TRPM8), is overexpressed in TPCs from patients with CRCLM. TCAF2 in TPCs is correlated with liver metastasis, short overall survival, and disease-free survival in CRC patients. Gain- and loss-of-function experiments validate that TCAF2 in TPCs promotes tumor cell motility, epithelial-mesenchymal transition (EMT), and CRCLM, which is attenuated in pericyte-conditional Tcaf2-knockout mice. Mechanistically, TCAF2 inhibits the expression and activity of TRPM8, leading to Wnt5a secretion in TPCs, which facilitates EMT via the activation of the STAT3 signaling pathway in tumor cells. Menthol, a TRPM8 agonist, significantly suppresses Wnt5a secretion in TPCs and CRCLM. This study reveals the previously unidentified pro-metastatic effects of TPCs from the perspective of cold-sensory receptors, providing a promising diagnostic biomarker and therapeutic target for CRCLM.

A bibliometric analysis of metastatic breast cancer: two-decade report (2002-2022)

Background

MBC is a lethal form of breast cancer that arises when cancer cells invade other organs or tissues. The treatment of MBC needs personalized approaches based on the tumor and patient characteristics. The purpose of this paper is to analyze MBC studies from 2002 to 2022 using bibliometrics and to investigate its current situation, main contributors, core journals, highly cited papers, and topic evolution.

Materials and methods

We retrieved data from Web of Science Core Collection (WOSCC). Bibliometric analysis of the included literatures mainly used the following tools: the function of "analyze results" and "citation report" in WoS, Microsoft excel 2021, CiteSpace v.6.1. R6, VOSviewer v.1.6.18, BICOMB v.2.04 and gCLUTO v.1.0.

Results

We found 12,653 articles on MBC research published in 1, 802 journals by 69, 753 authors from 118 countries. The annual output and citation of MBC articles showed a rising trend over time. The United States was the most influential country in MBC research. The most cited journal in this field was The Journal of Clinical Oncology. And the most cited article was by Slamon DJ. The co-word analysis of keywords divides MBC into six research clusters. The hormone receptor-positive MBC and liquid biopsy of MBC are the frontiers research trends. "CDK4/6 inhibitor" had the highest burst strength.

Conclusion

Our bibliometric analysis offers a comprehensive overview of MBC research in the past two decades. It shows the current situation, main contributors, core journals, highly cited papers, and topic evolution of this field. Our study can assist researchers and practitioners to comprehend the development and trends of MBC research and to discover potential directions for future research.

Towards understandings of serine/arginine-rich splicing factors

Serine/arginine-rich splicing factors (SRSFs) refer to twelve RNA-binding proteins which regulate splice site recognition and spliceosome assembly during precursor messenger RNA splicing. SRSFs also participate in other RNA metabolic events, such as transcription, translation and nonsense-mediated decay, during their shuttling between nucleus and cytoplasm, making them indispensable for genome diversity and cellular activity. Of note, aberrant SRSF expression and/or mutations elicit fallacies in gene splicing, leading to the generation of pathogenic gene and protein isoforms, which highlights the therapeutic potential of targeting SRSF to treat diseases. In this review, we updated current understanding of SRSF structures and functions in RNA metabolism. Next, we analyzed SRSF-induced aberrant gene expression and their pathogenic outcomes in cancers and non-tumor diseases. The development of some well-characterized SRSF inhibitors was discussed in detail. We hope this review will contribute to future studies of SRSF functions and drug development targeting SRSFs.

Hypoxia-driven ncRNAs in breast cancer

Low oxygen tension, or hypoxia is the driving force behind tumor aggressiveness, leading to therapy resistance, metastasis, and stemness in solid cancers including breast cancer, which now stands as the leading cause of cancer-related mortality in women. With the great advancements in exploring the regulatory roles of the non-coding genome in recent years, the wide spectrum of hypoxia-responsive genome is not limited to just protein-coding genes but also includes multiple types of non-coding RNAs, such as micro RNAs, long non-coding RNAs, and circular RNAs. Over the years, these hypoxia-responsive non-coding molecules have been greatly implicated in breast cancer. Hypoxia drives the expression of these non-coding RNAs as upstream modulators and downstream effectors of hypoxia inducible factor signaling in the favor of breast cancer through a myriad of molecular mechanisms. These non-coding RNAs then contribute in orchestrating aggressive hypoxic tumor environment and regulate cancer associated cellular processes such as proliferation, evasion of apoptotic death, extracellular matrix remodeling, angiogenesis, migration, invasion, epithelial-to-mesenchymal transition, metastasis, therapy resistance, stemness, and evasion of the immune system in breast cancer. In addition, the interplay between hypoxia-driven non-coding RNAs as well as feedback and feedforward loops between these ncRNAs and HIFs further contribute to breast cancer progression. Although the current clinical implications of hypoxia-driven non-coding RNAs are limited to prognostics and diagnostics in breast cancer, extensive explorations have established some of these hypoxia-driven non-coding RNAs as promising targets to treat aggressive breast cancers, and future scientific endeavors hold great promise in targeting hypoxia-driven ncRNAs at clinics to treat breast cancer and limit global cancer burden.

Hypoxia-induced loss of SRSF2-dependent DNA methylation promotes CTCF-mediated alternative splicing of VEGFA in breast cancer

Alternative splicing of vascular endothelial growth factor A (VEGFA) generates numerous isoforms with unique roles in tumor angiogenesis, and investigating the underlying mechanism during hypoxia necessitates diligent pursuance. Our research systematically demonstrated that the splicing factor SRSF2 causes the inclusion of exon-8b, leading to the formation of the anti-angiogenic VEGFA-165b isoform under normoxic conditions. Additionally, SRSF2 interacts with DNMT3A and maintains methylation on exon-8a, inhibiting CCCTC-binding factor (CTCF) recruitment and RNA polymerase II (pol II) occupancy, causing exon-8a exclusion and decreased expression of pro-angiogenic VEGFA-165a. Conversely, SRSF2 is downregulated by HIF1α-induced miR-222-3p under hypoxic conditions, which prevents exon-8b inclusion and reduces VEGFA-165b expression. Furthermore, reduced SRSF2 under hypoxia promotes hydroxymethylation on exon-8a, increasing CTCF recruitment, pol II occupancy, exon-8a inclusion, and VEGFA-165a expression. Overall, our findings unveil a specialized dual mechanism of VEGFA-165 alternative splicing, instrumented by the cross-talk between SRSF2 and CTCF, which promotes angiogenesis under hypoxic conditions.

Identifying missing pieces in color vision defects: a genome-wide association study in Silk Road populations

Introduction: Color vision defects (CVDs) are conditions characterized by the alteration of normal trichromatic vision. CVDs can arise as the result of alterations in three genes (OPN1LW, OPN1MW, OPN1SW) or as a combination of genetic predisposition and environmental factors. To date, apart from Mendelian CVDs forms, nothing is known about multifactorial CVDs forms. Materials and Methods: Five hundred and twenty individuals from Silk Road isolated communities were genotyped and phenotypically characterized for CVDs using the Farnsworth D-15 color test. The CVDs traits Deutan-Protan (DP) and Tritan (TR) were analysed. Genome Wide Association Study for both traits was performed, and results were corrected with a False Discovery Rate linkage-based approach (FDR-p). Gene expression of final candidates was investigated using a published human eye dataset, and pathway analysis was performed. Results: Concerning DP, three genes: PIWIL4 (FDR-p: 9.01*10^-9), MBD2 (FDR-p: 4.97*10^-8) and NTN1 (FDR-p: 4.98*10^-8), stood out as promising candidates. PIWIL4 is involved in the preservation of Retinal Pigmented Epithelium (RPE) homeostasis while MBD2 and NTN1 are both involved in visual signal transmission. With regards to TR, four genes: VPS54 (FDR-p: 4.09*10^-9), IQGAP (FDR-p: 6,52*10^-10), NMB (FDR-p: 8.34*10^-11), and MC5R (FDR-p: 2.10*10^-8), were considered promising candidates. VPS54 is reported to be associated with Retinitis pigmentosa; IQGAP1 is reported to regulate choroidal vascularization in Age-Related Macular Degeneration; NMB is involved in RPE homeostasis regulation; MC5R is reported to regulate lacrimal gland function. Discussion: Overall, these results provide novel insights regarding a complex phenotype (i.e., CVDs) in an underrepresented population such as Silk Road isolated communities.

Insights into the potential of Sanguinarine as a promising therapeutic option for breast cancer

Breast cancer (BC) is one of the leading causes of cancer-related deaths in women worldwide. The tumor microenvironment (TME) plays a crucial role in the progression and metastasis of BC. A significant proportion of BC is characterized by a hypoxic TME, which contributes to the development of drug resistance and cancer recurrence. Sanguinarine (SAN), an isoquinoline alkaloid found in Papaver plants, has shown promise as an anticancer agent. The present review focuses on exploring the molecular mechanisms of hypoxic TME in BC and the potential of SAN as a therapeutic option. The review presents the current understanding of the hypoxic TME, its signaling pathways, and its impact on the progression of BC. Additionally, the review elaborates on the mechanisms of action of SAN in BC, including its effects on vital cellular processes such as proliferation, migration, drug resistance, and tumor-induced immune suppression. The review highlights the importance of addressing hypoxic TME in treating BC and the potential of SAN as a promising therapeutic option.

Modular cytokine receptor-targeting chimeras for targeted degradation of cell surface and extracellular proteins

Targeted degradation of cell surface and extracellular proteins via lysosomal delivery is an important means to modulate extracellular biology. However, these approaches have limitations due to lack of modularity, ease of development, restricted tissue targeting and applicability to both cell surface and extracellular proteins. We describe a lysosomal degradation strategy, termed cytokine receptor-targeting chimeras (KineTACs), that addresses these limitations. KineTACs are fully genetically encoded bispecific antibodies consisting of a cytokine arm, which binds its cognate cytokine receptor, and a target-binding arm for the protein of interest. We show that KineTACs containing the cytokine CXCL12 can use the decoy recycling receptor, CXCR7, to target a variety of target proteins to the lysosome for degradation. Additional KineTACs were designed to harness other CXCR7-targeting cytokines, CXCL11 and vMIPII, and the interleukin-2 (IL-2) receptor-targeting cytokine IL-2. Thus, KineTACs represent a general, modular, selective and simple genetically encoded strategy for inducing lysosomal delivery of extracellular and cell surface targets with broad or tissue-specific distribution.

Alternative splicing signature of alveolar type II epithelial cells of Tibetan pigs under hypoxia-induced

Alternative splicing (AS) allows the generation of multiple transcript variants from a single gene and affects biological processes by generating protein diversity in organisms. In total, 41,642 AS events corresponding to 9,924 genes were identified, and SE is the most abundant alternatively spliced type. The analysis of functional categories demonstrates that alternatively spliced differentially expressed genes (DEGs) were enriched in the MAPK signaling pathway and hypoxia-inducible factor 1 (HIF-1) signaling pathway. Proteoglycans in cancer between the normoxic (21% O2, TN and LN) and hypoxic (2% O2, TL and LL) groups, such as SLC2A1, HK1, HK2, ENO3, and PFKFB3, have the potential to rapidly proliferate alveolar type II epithelial (ATII) cells by increasing the intracellular levels of glucose and quickly divert to anabolic pathways by glycolysis intermediates under hypoxia. ACADL, EHHADH, and CPT1A undergo one or two AS types with different frequencies in ATII cells between TN and TL groups (excluding alternatively spliced DEGs shared between normoxic and hypoxic groups), and a constant supply of lipids might be obtained either from the circulation or de novo synthesis for better growth of ATII cells under hypoxia condition. MCM7 and MCM3 undergo different AS types between LN and LL groups (excluding alternatively spliced DEGs shared between normoxic and hypoxic groups), which may bind to the amino-terminal PER-SIM-ARNT domain and the carboxyl terminus of HIF-1α to maintain their stability. Overall, AS and expression levels of candidate mRNAs between Tibetan pigs and Landrace pigs revealed by RNA-seq suggest their potential involvement in the ATII cells grown under hypoxia conditions.

Dysregulation of splicing variants and spliceosome components in breast cancer

The dysregulation of the splicing process has emerged as a novel hallmark of metabolic and tumor pathologies. In breast cancer (BCa), which represents the most diagnosed cancer type among women worldwide, the generation and/or dysregulation of several oncogenic splicing variants have been described. This is the case of the splicing variants of HER2, ER, BRCA1, or the recently identified by our group, In1-ghrelin and SST5TMD4, which exhibit oncogenic roles, increasing the malignancy, poor prognosis, and resistance to treatment of BCa. This altered expression of oncogenic splicing variants has been closely linked with the dysregulation of the elements belonging to the macromolecular machinery that controls the splicing process (spliceosome components and the associated splicing factors). In this review, we compile the current knowledge demonstrating the altered expression of splicing variants and spliceosomal components in BCa, showing the existence of a growing body of evidence supporting the close implication of the alteration in the splicing process in mammary tumorigenesis.

The splicing factor SF3B4 drives proliferation and invasion in cervical cancer by regulating SPAG5

Regulation of alternative splicing (AS) by the splicing factor 3b (SF3B) family plays an essential role in cancer. However, the biological function of SF3B family members in cervical cancer (CC) needs to be further elucidated. In this study, we found that splicing factor 3b subunit 4 (SF3B4) was highly expressed in CC by bioinformatics analysis using cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC) data from The Cancer Genome Atlas (TCGA). Then, we demonstrated that high expression of SF3B4 promoted proliferation and invasion abilities of CC cells in vitro and in vivo and that reduced expression of SF3B4 performed the opposite effect. Further RNA-seq and AS analysis showed that sperm-associated antigen 5 (SPAG5) was a downstream target gene of SF3B4. Interestingly, SPAG5 expression was decreased after SF3B4 knockdown because of retained introns (RIs) and reduced maturation of SPAG5 pre-mRNA. Importantly, SPAG5 deficiency impaired the oncogenic effects of SF3B4 overexpression on CC cells. In conclusion, SF3B4 promotes CC progression by regulating the effective splicing of SPAG5. SF3B4 could be a promising target for CC.

Long non-coding RNA ZNF674-AS1 antagonizes oxaliplatin resistance of gastric cancer via regulating EZH2-mediated methylation of CHST7

Chemoresistance leads the cause of poor outcome of patients with gastric cancer (GC). Long non-coding RNAs (LncRNAs) is intimately involved in the regulation of tumorigenesis and progression. Here, we demonstrated ZNF674-AS1 was down-regulated in oxaliplatin (OXA)-resistant tissues and cell lines, lower level of ZNF674-AS1 predicted poor prognosis of GC patients. Besides, forced expression of ZNF674-AS1 not only reduced cell viability, colony formation, expression of drug-resistant markers but also promoted cell apoptosis of OXA-resistant GC cells, exposed to oxaliplatin. Silence of ZNF674-AS1 exhibited an opposite effects on OXA resistance of GC cells. Further mechanistic research showed that ZNF674-AS1 interacted with EZH2, led to higher methylation level of target gene CHST7. In addition, functional experiments verified that depletion of CHST7 re-sensitized OXA-resistant GC cells to OXA. Thus, our results indicated that ZNF674-AS1 suppressed OXA resistance of GC through EZH2-mediated inhibition of CHST7, providing potential theoretic basis and therapeutic strategy for chemoresistant GC.

Increased Methyl-CpG-Binding Domain Protein 2 Promotes Cigarette Smoke-Induced Pulmonary Hypertension

Pulmonary hypertension (PH) is a chronic vascular proliferative disorder. While cigarette smoke (CS) plays a vital part in PH related to chronic obstructive pulmonary disease (COPD). Methyl-CpG-Binding Domain Protein 2 (MBD2) has been linked to multiple proliferative diseases. However, the specific mechanisms of MBD2 in CS-induced PH remain to be elucidated. Herein, the differential expression of MBD2 was tested between the controls and the PH patients’ pulmonary arteries, CS-exposed rat models’ pulmonary arteries, and primary human pulmonary artery smooth muscle cells (HPASMCs) following cigarette smoke extract (CSE) stimulation. As a result, PH patients and CS-induced rats and HPASMCs showed an increase in MBD2 protein expression compared with the controls. Then, MBD2 silencing was used to investigate the function of MBD2 on CSE-induced HPASMCs’ proliferation, migration, and cell cycle progression. As a consequence, CSE could induce HPASMCs’ increased proliferation and migration, and cell cycle transition, which were suppressed by MBD2 interference. Furthermore, RNA-seq, ChIP-qPCR, and MassARRAY were conducted to find out the downstream mechanisms of MBD2 for CS-induced pulmonary vascular remodeling. Subsequently, RNA-seq revealed MBD2 might affect the transcription of BMP2 gene, which furtherly altered the expression of BMP2 protein. ChIP-qPCR demonstrated MBD2 could bind BMP2’s promotor. MassARRAY indicated that MBD2 itself could not directly affect DNA methylation. In sum, our results indicate that increased MBD2 expression promotes CS-induced pulmonary vascular remodeling. The fundamental mechanisms may be that MBD2 can bind BMP2’s promoter and downregulate its expression. Thus, MBD2 may promote the occurrence of the CS-induced PH.

Brain vasculature disturbance in schizophrenia

PURPOSE OF REVIEW

The vascular hypothesis of schizophrenia (SZ) postulates that brain endothelial dysfunction contributes to brain pathophysiology. This review discusses recent evidence for and against this hypothesis, including data related to blood-brain barrier (BBB), brain endothelium, and brain blood supply, to provide a critical weighed update.

RECENT FINDINGS

Different studies report a consistent proportion of SZ patients showing increased BBB permeability, reflected by higher levels of albumin in the cerebral spinal fluid. Of note, this was not a result of antipsychotic medication. The high inflammatory profile observed in some SZ patients is strongly associated with increased BBB permeability to circulating immune cells, and with more severe cognitive deficiencies. Also, sex was found to interact with BBB integrity and permeability in SZ. The strongest independent genetic association with SZ has been identified in FZD1, a hypoxia-response gene that is 600-fold higher expressed in early development endothelium as compared to adult brain endothelium. Regarding brain blood supply, there is evidence to suggest alterations in proper brain perfusion in SZ. Nonetheless, ex-vivo experiments suggested that widely used antipsychotics favor vasoconstriction; thus, alterations in cerebral perfusion might be related to the patients' medication.

SUMMARY

In some patients with SZ, a vulnerable brain endothelium may be interacting with environmental stressors, such as inflammation or hypoxia, converging into a more severe SZ symptomatology. Gene expression and performance of human brain endothelium could vary along with development and the establishment of the BBB; therefore, we encourage to investigate its possible contribution to SZ considering this dynamic context.

Targeting HNRNPM Inhibits Cancer Stemness and Enhances Antitumor Immunity in Wnt-activated Hepatocellular Carcinoma

BACKGROUND & AIMS

Cancer stemness and immune evasion are closely associated and play critical roles in tumor development and resistance to immunotherapy. However, little is known about the underlying molecular mechanisms that coordinate this association.

METHODS

The expressions of heterogeneous nuclear ribonucleoprotein M (HNRNPM) in 240 hepatocellular carcinoma (HCC) samples, public databases, and liver development databases were analyzed. Chromatin immunoprecipitation assays were performed to explore the associations between stem-cell transcription factors and HNRNPM. HNRNPM-regulated alternative splicing (AS) and its binding motif were identified by RNA-seq and RIP-seq. HNRNPM-specific antisense oligonucleotides were developed to explore potential therapeutic targets in HCC. CD8+ T cells that were co-cultured with tumor cells were sorted by flow cytometry assays.

RESULTS

We identified an elevated oncofetal splicing factor in HCC, HNRNPM, that unifies and regulates the positive association between cancer stemness and immune evasion. HNRNPM knockdown abolished HCC tumorigenesis and diminished cancer stem cell properties in vitro and in vivo. Mechanistically, HNRNPM regulated the AS of MBD2 by binding its flanking introns, whose isoforms played opposing roles. Although MBD2a and MBD2c competitively bound to CpG islands in the FZD3 promoter, MBD2a preferentially increased FZD3 expression and then activated the WNT/β-catenin pathway. Interestingly, FZD3 and β-catenin further provided additional regulation by targeting OCT4 and SOX2. We found that HNRNPM inhibition significantly promoted CD8+ T cell activation and that HNRNPM- antisense oligonucleotides effectively inhibited WNT/β-catenin to enhance anti-programmed cell death protein-1 immunotherapy by promoting CD8+ T cell infiltration.

CONCLUSIONS

HNRNPM has a tumor-intrinsic function in generating an immunosuppressive HCC environment through an AS-dependent mechanism and demonstrates proof of the concept of targeting HNRNPM in tailoring HCC immunotherapeutic approaches.

Alternative Splicing, Epigenetic Modifications and Cancer: A Dangerous Triangle, or a Hopeful One?

Simple Summary

Epigenetics studies the alteration of gene expression without changing DNA sequence and very often, epigenetic dysregulation causes cancer. Alternative splicing is a mechanism that results in the production of several mRNA isoforms from a single gene and aberrant splicing is also a frequent cause of cancer. The present review is built on the interrelations of epigenetics and alternative splicing. In an intuitive way, we say that epigenetic modifications and alternative splicing are at two vertices of a triangle, the third vertex being occupied by cancer. Interconnection between alternative splicing and epigenetic modifications occurs backward and forward and the mechanisms involved are widely reviewed. These connections also provide novel diagnostic or prognostic tools, which are listed. Finally, as epigenetic alterations are reversible and aberrant alternative splicing may be corrected, the therapeutic possibilities to break the triangle are discussed.

Abstract

The alteration of epigenetic modifications often causes cancer onset and development. In a similar way, aberrant alternative splicing may result in oncogenic products. These issues have often been individually reviewed, but there is a growing body of evidence for the interconnection of both causes of cancer. Actually, aberrant splicing may result from abnormal epigenetic signalization and epigenetic factors may be altered by alternative splicing. In this way, the interrelation between epigenetic marks and alternative splicing form the base of a triangle, while cancer may be placed at the vertex. The present review centers on the interconnections at the triangle base, i.e., between alternative splicing and epigenetic modifications, which may result in neoplastic transformations. The effects of different epigenetic factors, including DNA and histone modifications, the binding of non-coding RNAs and the alterations of chromatin organization on alternative splicing resulting in cancer are first considered. Other less-frequently considered questions, such as the epigenetic regulation of the splicing machinery, the aberrant splicing of epigenetic writers, readers and erasers, etc., are next reviewed in their connection with cancer. The knowledge of the above-mentioned relationships has allowed increasing the collection of biomarkers potentially useful as cancer diagnostic and/or prognostic tools. Finally, taking into account on one hand that epigenetic changes are reversible, and some epigenetic drugs already exist and, on the other hand, that drugs intended for reversing aberrations in alternative splicing, therapeutic possibilities for breaking the mentioned cancer-related triangle are discussed.

Comprehensive analysis of prognosis-related alternative splicing events in ovarian cancer

Ovarian cancer (OV) is characterized by high incidence and poor prognosis. Increasing evidence indicates that aberrant alternative splicing (AS) events are associated with the pathogenesis of cancer. We examined prognosis-related alternative splicing events and constructed a clinically applicable model to predict patients’ outcomes. Public database including The Cancer Genome Atlas (TCGA), TCGA SpliceSeq, and the Genomics of Drug Sensitivity in Cancer databases were used to detect the AS expression, immune cell infiltration and IC50. The prognosis-related AS model was constructed and validated by using Cox regression, LASSO regression, C-index, calibration plots, and ROC curves. A total of eight AS events (including FLT3LG|50942|AP) were selected to establish the prognosis-related AS model. Compared with high-risk group, low-risk group had a better outcome (P = 1.794e-06), was more sensitive to paclitaxel (P = 0.022), and higher proportions of plasma cells. We explored the upstream regulatory mechanisms of prognosis-related AS and found that two splicing factor and 156 tag single nucleotide polymorphisms may be involved in the regulation of prognosis-related AS. In order to assess patient prognosis more comprehensively, we constructed a clinically applicable model combining risk score and clinicopathological features, and the 1 -, and 3-year AUCs of the clinically applicable model were 0.812, and 0.726, which were 7.5% and 3.3% higher than that of the risk score. We constructed a prognostic signature for OV patients and comprehensively analysed the regulatory characteristics of the prognostic AS events in OV.

The role of RNA processing and regulation in metastatic dormancy

Tumor dormancy is a major contributor to the lethality of metastatic disease, especially for cancer patients who develop metastases years-to-decades after initial diagnosis. Indeed, tumor cells can disseminate during early disease stages and persist in new microenvironments at distal sites for months, years, or even decades before initiating metastatic outgrowth. This delay between primary tumor remission and metastatic relapse is known as "dormancy," during which disseminated tumor cells (DTCs) acquire quiescent states in response to intrinsic (i.e., cellular) and extrinsic (i.e., microenvironmental) signals. Maintaining dormancy-associated phenotypes requires DTCs to activate transcriptional, translational, and post-translational mechanisms that engender cellular plasticity. RNA processing is emerging as an essential facet of cellular plasticity, particularly with respect to the initiation, maintenance, and reversal of dormancy-associated phenotypes. Moreover, dysregulated RNA processing, particularly that associated with alternative RNA splicing and expression of noncoding RNAs (ncRNAs), can occur in DTCs to mediate intrinsic and extrinsic metastatic dormancy. Here we review the pathophysiological impact of alternative RNA splicing and ncRNAs in promoting metastatic dormancy and disease recurrence in human cancers.

circKCNN2 suppresses the recurrence of hepatocellular carcinoma at least partially via regulating miR-520c-3p/methyl-DNA-binding domain protein 2 axis

BACKGROUND

Recurrence is the major cause of hepatocellular carcinoma (HCC) death. We aimed to identify circular RNA (circRNA) with predictive and therapeutic value for recurrent HCC.

METHODS

Tissue samples from recurrent and non-recurrent HCC patients were subjected to circRNA sequencing and transcriptome sequencing. circKCNN2 was identified through multi-omics analyses. The effects of circKCNN2 on HCC were evaluated in cells, animals, database of The Cancer Genome Atlas, and a cohort with 130 HCC patients. circRNA precipitation, chromatin immunoprecipitation assay, RNA pull-down, luciferase assay, and cell experiments were applied to evaluate the interaction of circKCNN2 with miRNAs and proteins. The association between circKCNN2 and the therapeutic effect of lenvatinib was investigated in HCC cell lines and HCC tissue-derived organoids.

RESULTS

The expression of circKCNN2 was downregulated in HCC tissues and predicted a favorable overall survival and recurrence-free survival. The expression of circKCNN2 was positively correlated with the parental gene, potassium calcium-activated channel subfamily N member (KCNN2). Nuclear transcription factor Y subunit alpha (NFYA) was proven to inhibit the promoter activity of KCNN2, downregulate the expression of KCNN2 and circKCNN2, and predict an unfavorable recurrence-free survival. Ectopic expression of circKCNN2 inhibited HCC cell proliferation, colony formation, migration, and tumor formation in a mouse model. miR-520c-3p sponged by circKCNN2 could reverse the inhibitory effect of circKCNN2 on HCC cells and down-regulate the expression of methyl-DNA-binding domain protein 2 (MBD2). The intratumoral expression of MBD2 predicted a favorable recurrence-free survival. circKCNN2 down-regulated the expression of fibroblast growth factor receptor 4 (FGFR4), which can be reversed by miR-520c-3p and knockdown of MBD2. Lenvatinib inhibited the expression of FGFR4 and upregulated the expression of circKCNN2 and MBD2. Ectopic expression of circKCNN2 in HCC cells enhanced the therapeutic effect of lenvatinib. However, the high inherent level of circKCNN2 in HCC cells was associated with lenvatinib resistance.

CONCLUSIONS

circKCNN2, transcriptionally repressed by NFYA, suppresses HCC recurrence via the miR-520c-3p/MBD2 axis. Inherent level of circKCNN2 in HCC cells predisposes anti-tumor effect of lenvatinib possibly because both circKCNN2 and lenvatinib repress the expression of FGFR4. circKCNN2 may be a promising predictive biomarker and therapeutic agent for HCC recurrence.

Wnt/β-catenin signaling in cancers and targeted therapies

Wnt/β-catenin signaling has been broadly implicated in human cancers and experimental cancer models of animals. Aberrant activation of Wnt/β-catenin signaling is tightly linked with the increment of prevalence, advancement of malignant progression, development of poor prognostics, and even ascendence of the cancer-associated mortality. Early experimental investigations have proposed the theoretical potential that efficient repression of this signaling might provide promising therapeutic choices in managing various types of cancers. Up to date, many therapies targeting Wnt/β-catenin signaling in cancers have been developed, which is assumed to endow clinicians with new opportunities of developing more satisfactory and precise remedies for cancer patients with aberrant Wnt/β-catenin signaling. However, current facts indicate that the clinical translations of Wnt/β-catenin signaling-dependent targeted therapies have faced un-neglectable crises and challenges. Therefore, in this study, we systematically reviewed the most updated knowledge of Wnt/β-catenin signaling in cancers and relatively targeted therapies to generate a clearer and more accurate awareness of both the developmental stage and underlying limitations of Wnt/β-catenin-targeted therapies in cancers. Insights of this study will help readers better understand the roles of Wnt/β-catenin signaling in cancers and provide insights to acknowledge the current opportunities and challenges of targeting this signaling in cancers.

Mining Natural Compounds to Target WNT Signaling: Land and Sea Tales

WNT signaling plays paramount roles in organism development, physiology, and disease, representing a highly attractive target for drug development. However, no WNT-modulating drugs have been approved, with several candidates trudging through the early clinical trials. This delay instigates alternative approaches to discover WNT-modulating drugs. Natural products were the source of therapeutics for centuries, but the chemical diversity they offer, especially when looking at different taxonomic groups and habitats, is still to a large extent unexplored. These considerations urge researchers to screen natural compounds for the WNT-modulatory activities. Since several reviews on such endeavors exist, we here have attempted to present these efforts as "Land and sea tales" (citing the book title by Rudyard Kipling) superimposing them onto the traditional pipeline of drug discovery and early development. In doing so, we illustrate each step of the pipeline with case studies stemming from our own research. It will become obvious that several steps of the pipeline need to be modified when applied to natural products rather than to synthetic libraries. Yet the main message of this chapter is that natural compounds represent a powerful source for the WNT signaling modulators and can be developed towards drug candidates against WNT-dependent maladies.