BRD4 promotes the stemness of gastric cancer cells via attenuating miR-216a-3p-mediated inhibition of Wnt/β-catenin signaling

High-altitude hypoxia promotes BRD4-mediated activation of the Wnt/β-catenin pathway and disruption of intestinal barrier

Hypobaric hypoxia, commonly experienced at elevated altitudes, presents significant physiological challenges. Our investigation is centered on the impact of the bromodomain protein 4 (BRD4) under these conditions, especially its interaction with the Wnt/β-Catenin pathway and resultant effects on glycolytic inflammation and intestinal barrier stability. By combining transcriptome sequencing with bioinformatics, we identified BRD4's key role in hypoxia-related intestinal anomalies. Clinical parameters of altitude sickness patients, including serum BRD4 levels, inflammatory markers, and barrier integrity metrics, were scrutinized. In vitro studies using CCD 841 CoN cells depicted expression changes in BRD4, Interleukin (IL)-1β, IL-6, and β-Catenin. Transepithelial electrical resistance (TEER) and FD4 analyses assessed barrier resilience. Hypoxia-induced mouse models, analyzed via H&E staining and Western blot, provided insights into barrier and protein alterations. Under hypoxic conditions, marked BRD4 expression variations emerged. Elevated serum BRD4 in patients coincided with intensified Wnt signaling, inflammation, and barrier deterioration. In vitro, findings showed hypoxia-induced upregulation of BRD4 and inflammatory markers but a decline in Occludin and ZO1, affecting barrier strength-effects mitigated by BRD4 inhibition. Mouse models echoed these patterns, linking BRD4 upregulation in hypoxia to barrier perturbations. Hypobaric hypoxia-induced BRD4 upregulation disrupts the Wnt/β-Catenin signaling, sparking glycolysis-fueled inflammation and weakening intestinal tight junctions and barrier degradation.

Wnt signaling and tumors (Review)

Wnt signaling is a highly conserved evolutionary pathway that plays a key role in regulation of embryonic development, as well as tissue homeostasis and regeneration. Abnormalities in Wnt signaling are associated with tumorigenesis and development, leading to poor prognosis in patients with cancer. However, the pharmacological effects and mechanisms underlying Wnt signaling and its inhibition in cancer treatment remain unclear. In addition, potential side effects of inhibiting this process are not well understood. Therefore, the present review outlines the role of Wnt signaling in tumorigenesis, development, metastasis, cancer stem cells, radiotherapy resistance and tumor immunity. The present review further identifies inhibitors that target Wnt signaling to provide a potential novel direction for cancer treatment. This may facilitate early application of safe and effective drugs targeting Wnt signaling in clinical settings. An in-depth understanding of the mechanisms underlying inhibition of Wnt signaling may improve the prognosis of patients with cancer.

Circular RNA AGAP1 Stimulates Immune Escape and Distant Metastasis in Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most representative subtype of renal cancer, with a highly aggressive phenotype and extremely poor prognosis. Immune escape is one of the main reasons for ccRCC growth and metastasis, in which circular RNAs (circRNAs) play critical roles. Therefore, this research studied circAGAP1-associated mechanisms in immune escape and distant metastasis in ccRCC. circAGAP1/miR-216a-3p/MKNK2 was overexpressed or down-regulated by cell transfection. EdU assay, colony formation assay, scratch assay, Transwell assay, immunoblotting, and flow cytometry were used to evaluate cell proliferation, migration, invasion, EMT, and immune escape, respectively. Dual-luciferase reporting assay and RIP assay were used to evaluate the targeting relationship between circAGAP1/miR-216a-3p/MKNK2. Xenotransplantation in nude mice was used to evaluate the growth of ccRCC tumors in vivo. Here, circAGAP1 high expression was positively correlated with higher histological grade and distant metastasis and was a prognostic indicator for ccRCC. Depleting circAGAP1 effectively hampered the proliferative, invasive, and migratory capacities, EMT, and immune escape of ccRCC cells. Correspondingly, silencing circAGAP1 delayed tumor growth, distant metastasis, and immune escape in vivo. Mechanistically, circAGAP1 sponged the tumor suppressor miR-216a-3p, thereby preventing miR-216a-3p from inhibiting MAPK2. Collectively, our findings demonstrate that circAGAP1 exerts a tumor suppressor function through miR-216a-3p/MKNK2 during the immune escape and distant metastasis in ccRCC, and suggest that circAGAP1 may be a novel prognostic marker and therapeutic target for ccRCC.

Multifaceted role of microRNAs in gastric cancer stem cells: Mechanisms and potential biomarkers

MicroRNAs (miRNAs) have received much attention in the past decade as potential key epigenomic regulators of tumors and cancer stem cells (CSCs). The abnormal expression of miRNAs is responsible for different phenotypes of gastric cancer stem cells (GCSCs). Some specific miRNAs could be used as promising biomarkers and therapeutic targets for the identification of GCSCs. This review summarizes the coding process and biological functions of miRNAs and demonstrates their role and efficacy in gastric cancer (GC) metastasis, drug resistance, and apoptosis, especially in the regulatory mechanism of GCSCs. It shows that the overexpression of onco-miRNAs and silencing of tumor-suppressor miRNAs can play a role in promoting or inhibiting tumor metastasis, apart from the initial formation of GC. It also discusses the epigenetic regulation and potential clinical applications of miRNAs as well as the role of CSCs in the pathogenesis of GC. We believe that this review may help in designing novel therapeutic approaches for GC.

Overexpression of BRD4 in Gastric Cancer and its Clinical Significance as a Novel Therapeutic Target

BACKGROUND

BRD4 is a member of the bromodomain and extra terminal domain (BET) family of proteins, containing two bromodomains and one extra terminal domain, and is overexpressed in several human malignancies. However, its expression in gastric cancer has not yet been well illustrated.

OBJECTIVE

This study aimed to elucidate the overexpression of BRD4 in gastric cancer and its clinical significance as a novel therapeutic target.

METHODS

Fresh gastric cancer tissues and paraffin-embedded specimens of gastric cancer patients were collected, and the BRD4 expression was examined by Western Blot Analysis (WB) and Immunohistochemistry Analysis (IHC), respectively. The possible relationship between BRD4 expression and the clinicopathological features as well as survival in gastric cancer patients was analyzed. The effect of BRD4 silencing on human gastric cancer cell lines was investigated by MTT assay, WB, wound healing assay, and Transwell invasion.

RESULTS

The results showed that the expression level in tumor tissues and adjacent tissues was significantly higher than that in normal tissues, respectively (P < 0.01). BRD4 expression level in gastric cancer tissues was strongly correlated with the degree of tumor differentiated degree (P = 0.033), regional lymph nodes metastasis (P = 0.038), clinical staging (P = 0.002), and survival situation (P = 0.000), while the gender (P = 0.564), age (P = 0.926) and infiltrating depth (P = 0.619) of patients were not associated. Increased BRD4 expression resulted in poor overall survival (P = 0.003). In in vitro assays, BRD4 small interfering RNA resulted in significantly decreased BRD4 protein expression, therefore inhibiting proliferation, migration, and invasion of gastric cancer cells.

CONCLUSION

BRD4 might be a novel biomarker for the early diagnosis, prognosis, and therapeutic target in gastric cancer.

MicroRNA: trends in clinical trials of cancer diagnosis and therapy strategies

As a type of short noncoding RNAs, microRNA (miRNA) undoubtedly plays a crucial role in cancer development. Since the discovery of the identity and clinical functions of miRNAs, over the past few decades, the roles of miRNAs in cancer have been actively investigated. Numerous pieces of evidence indicate that miRNAs are pivotal factors in most types of cancer. Recent cancer research focused on miRNAs has identified and characterized a large cohort of miRNAs commonly dysregulated in cancer or exclusively dysregulated in specific types of cancer. These studies have suggested the potential of miRNAs as biomarkers in the diagnosis and prognostication of cancer. Moreover, many of these miRNAs have oncogenic or tumor-suppressive functions. MiRNAs have been the focus of research given their potential clinical applications as therapeutic targets. Currently, various oncology clinical trials using miRNAs in screening, diagnosis, and drug testing are underway. Although clinical trials studying miRNAs in various diseases have been reviewed before, there have been fewer clinical trials related to miRNAs in cancer. Furthermore, updated results of recent preclinical studies and clinical trials of miRNA biomarkers and drugs in cancer are needed. Therefore, this review aims to provide up-to-date information on miRNAs as biomarkers and cancer drugs in clinical trials.

An emphasis on the interaction of signaling pathways highlights the role of miRNAs in the etiology and treatment resistance of gastric cancer

Gastric cancer (GC) is 4th in incidence and mortality rates globally. Several genetic and epigenetic factors, including microRNAs (miRNAs), affect its initiation and progression. miRNAs are short chains of nucleic acids that can regulate several cellular processes by controlling their gene expression. So, dysregulation of miRNAs expressions is associated with GC initiation, progression, invasion capacity, apoptosis evasions, angiogenesis, promotion and EMT enhancement. Of important pathways in GC and controlled by miRNAs are Wnt/β-catenin signaling, HMGA2/mTOR/P-gp, PI3K/AKT/c-Myc, VEGFR and TGFb signaling. Hence, this review was conducted to review an updated view of the role of miRNAs in GC pathogenesis and their modulatory effects on responses to different GC treatment modalities.

Molecular mechanisms of microRNA-216a during tumor progression

MicroRNAs (miRNAs) as the members of non-coding RNAs family are involved in post-transcriptional regulation by translational inhibiting or mRNA degradation. They have a critical role in regulation of cell proliferation and migration. MiRNAs aberrations have been reported in various cancers. Considering the importance of these factors in regulation of cellular processes and their high stability in body fluids, these factors can be suggested as suitable non-invasive markers for the cancer diagnosis. MiR-216a deregulation has been frequently reported in different cancers. Therefore, in the present review we discussed the molecular mechanisms of the miR-216a during tumor progression. It has been reported that miR-216a mainly functioned as a tumor suppressor through the regulation of signaling pathways and transcription factors. This review paves the way to suggest the miR-216a as a probable therapeutic and diagnostic target in cancer patients.

Chromatin and noncoding RNA-mediated mechanisms of gastric tumorigenesis

Gastric cancer (GC) is one of the most common and deadly cancers in the world. It is a multifactorial disease highly influenced by environmental factors, which include radiation, smoking, diet, and infectious pathogens. Accumulating evidence suggests that epigenetic regulators are frequently altered in GC, playing critical roles in gastric tumorigenesis. Epigenetic regulation involves DNA methylation, histone modification, and noncoding RNAs. While it is known that environmental factors cause widespread alterations in DNA methylation, promoting carcinogenesis, the chromatin- and noncoding RNA-mediated mechanisms of gastric tumorigenesis are still poorly understood. In this review, we focus on discussing recent discoveries addressing the roles of histone modifiers and noncoding RNAs and the mechanisms of their interactions in gastric tumorigenesis. A better understanding of epigenetic regulation would likely facilitate the development of novel therapeutic approaches targeting specific epigenetic regulators in GC.

Bromodomain (BrD) Family Members as Regulators of Cancer Stemness-A Comprehensive Review

Epigenetic mechanisms involving DNA methylation and chromatin modifications have emerged as critical facilitators of cancer heterogeneity, substantially affecting cancer development and progression, modulating cell phenotypes, and enhancing or inhibiting cancer cell malignant properties. Not surprisingly, considering the importance of epigenetic regulators in normal stem cell maintenance, many chromatin-related proteins are essential to maintaining the cancer stem cell (CSC)-like state. With increased tumor-initiating capacities and self-renewal potential, CSCs promote tumor growth, provide therapy resistance, spread tumors, and facilitate tumor relapse after treatment. In this review, we characterized the epigenetic mechanisms that regulate the acquisition and maintenance of cancer stemness concerning selected epigenetic factors belonging to the Bromodomain (BrD) family of proteins. An increasing number of BrD proteins reinforce cancer stemness, supporting the maintenance of the cancer stem cell population in vitro and in vivo via the utilization of distinct mechanisms. As bromodomain possesses high druggable potential, specific BrD proteins might become novel therapeutic targets in cancers exhibiting de-differentiated tumor characteristics.

Investigations into the impact of non-coding RNA on the sensitivity of gastric cancer to radiotherapy

Non-coding RNAs (ncRNAs) are a newly discovered functional RNA different from messenger RNA, which can participate in regulating the occurrence and development of tumors. More and more research results show that ncRNAs can participate in the regulation of gastric cancer (GC) radiotherapy response, and its mechanism may be related to its effect on DNA damage repair, gastric cancer cell stemness, cell apoptosis, activation of epidermal growth factor receptor signaling pathway, etc. This article summarizes the relevant mechanisms of ncRNAs regulating the response to radiotherapy in gastric cancer, which will be directly important for the introduction of ncRNAs particularly microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) into clinical medicine as biomarkers and therapeutic targets.

ALDH1: A potential therapeutic target for cancer stem cells in solid tumors

Solid tumors can be divided into benign solid tumors and solid malignant tumors in the academic community, among which malignant solid tumors are called cancers. Cancer is the second leading cause of death in the world, and the global incidence of cancer is increasing yearly New cancer patients in China are always the first. After the concept of stem cells was introduced in the tumor community, the CSC markers represented by ALDH1 have been widely studied due to their strong CSC cell characteristics and potential to be the driving force of tumor metastasis. In the research results in the past five years, it has been found that ALDH1 is highly expressed in various solid cancers such as breast cancer, lung cancer, colorectal cancer, liver cancer, gastric cancer, cervical cancer, esophageal cancer, ovarian cancer, head,and neck cancer. ALDH1 can activate and transform various pathways (such as the USP28/MYC signaling pathway, ALDH1A1/HIF-1α/VEGF axis, wnt/β-catenin signaling pathway), as well as change the intracellular pH value to promote formation and maintenance, resulting in drug resistance in tumors. By targeting and inhibiting ALDH1 in tumor stem cells, it can enhance the sensitivity of drugs and inhibit the proliferation, differentiation, and metastasis of solid tumor stem cells to some extent. This review discusses the relationship and pathway of ALDH1 with various solid tumors. It proposes that ALDH1 may serve as a diagnosis and therapeutic target for CSC, providing new insights and new strategies for reliable tumor treatment.

The prognostic significance of bromodomain protein 4 expression in solid tumor patients: A meta-analysis

BACKGROUND

Cancer is a leading cause of death worldwide. At present, several inhibitors of bromodomain protein 4 have shown promising anti-tumor responses in clinical trials. Numerous studies have reported the value of bromodomain protein 4 expression in predicting the prognosis of patients with cancers, but their conclusions remain controversial. Therefore, we conducted a meta-analysis to explore the association between bromodomain protein 4 and patient prognosis with the aim to provide new directions for the development of strategies for targeted cancer therapy.

METHODS

The meta-analysis was registered in the International Prospective Register of Systematic Reviews (https://www.crd.york.ac.uk/prospero/; Registration No. CRD42020184948) and followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement. PubMed Central, PubMed, Cochrane Library and Embase were thoroughly searched to identify eligible studies published through March 31, 2021. Odds ratios with 95% confidence intervals were calculated to demonstrate the relationship between bromodomain protein 4 expression and clinicopathological features. We computed pooled estimated hazard ratios with 95% confidence intervals using Stata 12.0 software to clarify the relationship between bromodomain protein 4 expression and overall survival of various cancers. A quality assessment of the eligible articles was performed based on the Newcastle-Ottawa scale.

RESULTS

A total of 974 patients from 10 studies were enrolled in the meta-analysis. Our results revealed that compared to low bromodomain protein 4 expression, high bromodomain protein 4 expression in cancer tissues was significantly associated with lymph node metastasis (Odds ratio = 3.59, 95% confidence interval: 2.62-4.91), distant metastasis (Odds ratio = 4.22, 95% confidence interval: 2.40-7.45), advanced TNM stage (III+IV vs. I+II: Odds ratio = 3.23, 95% confidence interval: 1.29-8.08), and poorly differentiated tumors (Odds ratio = 1.87, 95% confidence interval: 1.33-2.63). In addition, an elevated expression of bromodomain protein 4 tended to shorten survival time (Hazard ratio = 2.23, 95% confidence interval: 1.62-3.07). The subgroup analysis results showed that bromodomain protein 4 upregulation was related to poor prognosis in patients with digestive system cancers (Hazard ratio = 2.54, 95% confidence interval: 1.85-3.50).

CONCLUSION

This meta-analysis indicated that bromodomain protein 4 may serve as a promising prognostic biomarker for cancers and a direct effective cancer treatment target.

Berbamine Suppresses the Growth of Gastric Cancer Cells by Inactivating the BRD4/c-MYC Signaling Pathway

PURPOSE

Berbamine (Ber), a bioactive constituent extracted from a traditional Chinese medicinal herb, has been shown to exhibit broad inhibitory activity on a panel of cancer cell types. However, its effects and the underlying molecular mechanisms on gastric cancer (GC) remain poorly understood.

METHODS

The anti-growth activity of Ber on two GC cell lines and normal gastric epithelial cell line were evaluated using MTS and clone formation assay. Flow cytometry analysis was employed to evaluate the cell cycle distribution and apoptosis of GC cells. Western blot and quantitative PCR (qPCR) analysis were employed to investigate the anti-GC mechanism of Ber. The inhibitory activity and binding affinity of Ber against BRD4 were evaluated by homogeneous time-resolved fluorescence (HTRF) and surface plasmon resonance (SPR) assay, respectively. Molecular docking and molecular simulations were conducted to predict the interaction mode between BRD4 and Ber.

RESULTS

The results demonstrated that Ber reduced the proliferation of GC cell lines SGC-7901 and BGC-823 and induced cell cycle arrest and apoptosis. Mechanistically, Ber was identified as a novel natural-derived BRD4 inhibitor through multiple experimental assay, and its anti-GC activity was probably mediated by BRD4 inhibition. Molecular modeling studies suggested that Ber might bind to BRD4 primarily through hydrophobic interactions.

CONCLUSION

Our study uncovered the underlying anti-GC activity of Ber in vitro and suggested that Ber holds promise as a potential lead compound in the discovery of novel BRD4 inhibitors.

Aldehyde Dehydrogenase 1 in Gastric Cancer

Gastric cancer (GC) is a disease that threatens human health. It is thus crucial to clarify the mechanisms involved in GC development and discover diagnostic biomarkers and therapeutics. As a cancer stem cell marker, aldehyde dehydrogenase 1 (ALDH1) is involved in the development, progression, and treatment of GC. This review evaluated the prognostic value of ALDH1 and explored its mechanism of action in GC. Importantly, ALDH1 is an informative biomarker in clinical practice as it has specific relationships with indicators, such as metastasis and overall survival. Additionally, ALDH1 interacts with genes and exhibits properties that mimic stem cell characteristics amongst other mechanisms employed in the occurrence and progression of GC. Our results, therefore, provide evidence of possible clinical utility of ALDH1 as a GC therapeutic target.

Systematic Analysis of Molecular Characterization and Clinical Relevance of Liquid–Liquid Phase Separation Regulators in Digestive System Neoplasms

Background: The role of liquid–liquid phase separation (LLPS) in cancer has also attracted more and more attention, which is found to affect transcriptional regulation, maintaining genomic stability and signal transduction, and contribute to the occurrence and progression of tumors. However, the role of LLPS in digestive system tumors is still largely unknown.

Results: Here, we characterized the expression profiles of LLPS regulators in 3 digestive tract tumor types such as COAD, STAD, and ESCA with The Cancer Genome Atlas (TCGA) data. Our results for the first time showed that LLPS regulatory factors, such as Brd4, FBN1, and TP53, were frequently mutated in all types of digestive system tumors. Variant allele frequency (VAF) and APOBEC analysis demonstrated that genetic alterations of LLPS regulators were related to the progression of digestive system neoplasms (DSNs), such as TP53, NPHS1, TNRC6B, ITSN1, TNPO1, PML, AR, BRD4, DLG4, and PTPN1. KM plotter analysis showed that the mutation status of LLPS regulators was significantly related to the overall survival (OS) time of DSNs, indicating that they may contribute to the progression of DSN. The expression analysis of LLPS regulatory factors showed that a variety of LLPS regulatory factors were significantly dysregulated in digestive system tumors, such as SYN2 and MAPT. It is worth noting that we first found that LLPS regulatory factors were significantly correlated with tumor immune infiltration of B cells, CD4+ T cells, and CD8+ T cells in digestive system tumors. Bioinformatics analysis showed that the LLPS regulators’ expression was closely related to multiple signaling, including the ErbB signaling pathway and T-cell receptor signaling pathway. Finally, several LLPS signatures were constructed and had a strong prognostic stratification ability in different digestive gland tumors. Finally, the results demonstrated the LLPS regulators’ signature score was significantly positively related to the infiltration levels of CD4⁺ T cells, neutrophil cells, macrophage cells, and CD8⁺ T cells.

Conclusion: Our study for the first time showed the potential roles of LLPS regulators in carcinogenesis and provide novel insights to identify novel biomarkers for the prediction of immune therapy and prognosis of DSNs.

miR-124a Involves in the Regulation of Wnt/β-Catenin and P53 Pathways to Inhibit Abdominal Aortic Aneurysm via Targeting BRD4

BACKGROUND

Abdominal aortic aneurysm (AAA) belongs to a progressive, gradual aortic rupture, which can lead to death without surgical intervention. The key factors regulating the occurrence and progress of AAA are not clear. Increasing studies have indicated that microRNA (miRNA) plays an important role in cancer development. miR-124a serves as a tumor suppressor in several neoplasms, and its upregulation can greatly inhibit the life activities such as malignant growth and migration of tumor cells.

AIM

The objective of this study is to explore the association of miR-124a with AAA and to uncover the regulated mechanism of miR-124a on AAA progression.

METHODS

The specimens from the AAA patients were used for observing the miR-124a expression, and human aortic endothelial cells (hAoECs) were treated with AngII to establish the AAA cell models. The quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), CCK-8, transwell assay, flow cytometry assay, and western blot were conducted to unearth the regulation mechanism of miR-124a on AAA, and the dual-luciferase reporter assay was employed to investigate the downstream target of miR-124a.

RESULTS

miR-124a was significantly downregulated in the whole blood of the patients, and the decreased miR-124a was also observed in AAA cell models. Overexpressing miR-124a could effectively inhibit the proliferation and migration and promote the apoptosis of the AAA cells. The dual-luciferase reporter assay confirmed that BRD4 was a downstream target of miR-124a, and BRD4 upregulation could obviously reverse the effects of miR-124a on the phenotype of AAA cells. Moreover, it was found that miR-124a could regulate the activities of Wnt/β-catenin and P53 pathways via targeting the BRD4.

CONCLUSION

Our data suggested that miR-124a could regulate the activities of Wnt/β-catenin and P53 to suppress the AAA progression via targeting the BRD4.

The association between bromodomain (BrD) proteins and cancer stemness in different solid tumor types

Cancer stemness, which covers the stem cell‐like molecular traits of cancer cells, is essential for tumor development, progression and relapse. Both transcriptional and epigenetic aberrations are essentially connected with cancer stemness. The engagement of bromodomain (BrD) proteins—a family of epigenetic factors—has been presented in the pathogenesis of several tumor types, although their association with cancer stemness remains largely unknown. Here, we harnessed TCGA and GEO databases and used several bioinformatic tools (ie, Oncomine, PrognoScan, GEPIA2, TIMER2.0, TISIDB, GSEA, R2 platform) to characterize the association between the BrD family members' expression and cancer stemness in solid tumors. Our results demonstrate that significant upregulation of ATAD2 and SMARCA4, and downregulation of SMARCA2 is consistently associated with enriched cancer stem cell‐like phenotype, respectively. Especially, higher‐grade tumors that display stem cell‐like properties overexpress ATAD2. In contrast to most BrD members, the gene expression profiles of ATAD2^HIGH expressing tumors are strongly enriched with known markers of stem cells and with specific targets for c‐Myc transcription factor. For other BrD proteins, the association with cancer de‐differentiation status is rather tumor‐specific. Our results demonstrate for the first time the relation between distinct BrD family proteins and cancer stemness across 27 solid tumor types. Specifically, our approach allowed us to discover a robust association of high ATAD2 expression with cancer stemness and reveal its' versatility in tumors. As bromodomains are attractive targets from a chemical and structural perspective, we propose ATAD2 as a novel druggable target for de‐differentiated tumors, especially those overexpressing MYC.

PCAT6 May Be a Whistler and Checkpoint Target for Precision Therapy in Human Cancers

Simple Summary

Prostate cancer-associated transcript 6 (PCAT6), as a newly discovered carcinogenic long non-coding RNA (lncRNA), is abnormally expressed in multiple diseases. With the accumulation of studies on PCAT6, we have a deeper understanding of its biological functions and mechanisms. Therefore, in this review, the various molecular mechanisms by which PCAT6 promotes multiple tumorigenesis and progression are summarized and discussed. Furthermore, its potential diagnostic, prognostic, and immunotherapeutic values are also clarified.

Abstract

LncRNAs are involved in the occurrence and progressions of multiple cancers. Emerging evidence has shown that PCAT6, a newly discovered carcinogenic lncRNA, is abnormally elevated in various human malignant tumors. Until now, PCAT6 has been found to sponge various miRNAs to activate the signaling pathways, which further affects tumor cell proliferation, migration, invasion, cycle, apoptosis, radioresistance, and chemoresistance. Moreover, PCAT6 has been shown to exert biological functions beyond ceRNAs. In this review, we summarize the biological characteristics of PCAT6 in a variety of human malignancies and describe the biological mechanisms by which PCAT6 can facilitate tumor progression. Finally, we discuss its diagnostic and prognostic values and clinical applications in various human malignancies.

BRD4 REGULATES TRANSCRIPTION FACTOR ∆Np63αTO DRIVE A CANCER STEM CELL PHENOTYPE IN SQUAMOUS CELL CARCINOMAS

Bromodomain containing protein 4 (BRD4) plays a critical role in controlling the expression of genes involved in development and cancer. Inactivation of BRD4 inhibits cancer growth, making it a promising anticancer drug target. The cancer stem cell population is a key driver of recurrence and metastasis in cancer patients. Here we show that cancer stem-like cells can be enriched from squamous cell carcinomas, and that these cells display an aggressive phenotype with enhanced stem cell marker expression, migration, invasion, and tumor growth. BRD4 was highly elevated in this aggressive subpopulation of cells, and its function is critical for these cancer stem cell-like properties. Moreover, BRD4 regulated ∆Np63α, a key transcription factor that is essential for epithelial stem cell function that is often overexpressed in cancers. BRD4 regulated an EZH2/STAT3 complex that led to increased ∆Np63α-mediated transcription. Targeting BRD4 in human squamous cell carcinoma reduces ∆Np63α, leading to inhibition of spheroid formation, migration, invasion and tumor growth. These studies identify a novel BRD4-regulated signaling network in a subpopulation of cancer stem-like cells elucidating a possible avenue for effective therapeutic intervention.

The design, synthesis and cellular imaging of a tumor-anchored, potent and cell-permeable BRD4-targeted fluorescent ligands

Bromodomain 4 (BRD4) proteins play an important role in histone post-translational modifications and facilitate several important physiological and pathological processes, including cancers. The inhibition of BRD4 by small molecule inhibitors shows promise as a therapeutic strategy for cancer treatment. However, their clinical applications were limited, which is largely hampered by off-target effects-induced toxicity. We herein report the design, synthesis, and cellular imaging of a set of tumor-anchored and BRD4-targeted fluorescent ligands by introducing selective and potent BRD4 inhibitor into different fluorophores via variable linkers. One of the fluorescent conjugates (compound 6) was demonstrated to be cell-permeable and low cytotoxic, preferentially accumulated in cancer cells, and display pronounced fluorescent signal. More importantly, 6 was identified to show specific BRD4 engagement in the cellular content. Collectively, this study provides a pathway for developing labeled BRD4 ligands and highlights that compound 6 may represent a valuable tool for explorative learning and target delivery study of BRD4.

BRD4 induces osteogenic differentiation of BMSCs via the Wnt/β-catenin signaling pathway

Bromodomain 4 (BRD4), an important epigenetic regulator, is involved in many bone-related pathologies via promoting osteoclast formation. However, whether and how it participates in the process of osteoblast formation remain unclear. This study aimed to investigate the potential role of BRD4 in osteogenic differentiation of bone marrow stromal cells (BMSCs). Our experiments revealed that an inhibitor of BRD4, JQ1, attenuated osteogenic differentiation of BMSCs. The recombinant adenoviruses for AdBRD4 and AdsiBRD4 could infect BMSCs with high efficiency. Exogenous BRD4 expression potentiated differentiation, and silencing endogenous BRD4 expression decreased it. In addition, the Wnt/β-catenin signaling pathway is known to be important for osteogenic differentiation. Our results showed that AdBRD4 increased the expressions of Wnt3a and β-catenin while AdsiBRD4 decreased the expressions. What's more, the recombinant adenovirus for Adsiβ-catenin, which obviously decreased in β-catenin expression, inhibited BRD4-induced osteogenic differentiation. Conclusion: Our data indicates that the epigenetic reader BRD4 participates in the process of BMSC osteogenic differentiation via the Wnt/β-catenin signaling pathway. This finding may pave the way into further understanding the mechanism of BMSC osteogenic differentiation.

Clinical crosstalk between microRNAs and gastric cancer (Review)

Globally, there were over 1 million new gastric cancer (GC) patients in 2018 and GC has become the sixth most common cancer worldwide. GC caused 783,000 deaths worldwide in 2018, making it the third most deadly cancer type. miRNAs are short (~22 nucleotides in length) non‑coding RNA molecules, which can regulate gene expression passively at a post‑transcriptional level. There are more and more in‑depth studies on miRNAs. There are numerous conclusive evidences that there is an inseparable link between miRNAs and GC. miRNAs can affect the entire process of GC, including the oncogenesis, development, diagnosis, treatment and prognosis of GC. Although many miRNAs have been linked to GC, few can be applied to clinical practice. This review takes the clinical changes of GC as a clue and summarizes the miRNAs related to GC that have confirmed the mechanism of action in the past three years. Through in‑depth study and understanding of the mechanism of those miRNAs, we predict their possible clinical uses, and suggest some new insights to overcome GC.

CircABCC4 Regulates the Proliferation, Migration, and Invasion of Colorectal Cancer SW620 Cells by Targeting Micro RNA-216a-3p

This work investigates the effect of circABCC4 on the proliferation, migration, and invasion of colorectal cancer SW620 cells; circABCC4’s regulation of miR-216a-3p is also studied. qRT-PCR was used to measure the levels of circABCC4 and miR-216a-3p in colorectal cancer and adjacent tissues. The human colorectal cancer SW620 cells were transfected with different constructs of circABCC4 or miR-216a-3p or both to study their interactions and combined effects on cell behavior. A dual-luciferase reporter experiment tested the targeted relationship between circABCC4 to miR-216a-3p. Furthermore, the behaviors of SW620 cells, such as cell viability, migration, and invasion, were investigated. Also, the proteins related to cell behaviors were investigated with western blotting. Our results showed that colorectal cancer tissues had a higher level of circABCC4 but a lower level miR-216a-3p. The increased level of circABCC4 and the reduced level of miR-216a-3p had analogous influences on the behaviors of SW620 cells, resulting in reduced cell proliferation, migration, and invasion; the levels of related protein were also decreased. Moreover, we found that disrupting miR-548c-3p could reverse the influence of inhibiting circABCC4 on SW620 cells. In addition, the dual-luciferase reporter assay results confirmed the targeting of miR-216a-3p by circABCC4. These data demonstrate that the silencing of circABCC4 may inhibit the proliferation, migration, and invasion of colorectal cancer cells by upregulating miR-548c-3p.

Roles of microRNAs in Gastrointestinal Cancer Stem Cell Resistance and Therapeutic Development

Resistance to cancer treatment is one of the major challenges currently faced when treating gastrointestinal (GI) cancers. A major contributing factor to this resistance is the presence of cancer stem cells (CSCs) in GI cancers (e.g., colorectal, pancreatic, gastric, liver cancer). Non-coding RNAs, such as microRNAs (miRNAs), have been found to regulate several key targets that are responsible for cancer stemness, and function as oncogenic miRNAs (oncomiRs) or tumor suppressor miRNAs. As a result, several miRNAs have been found to alter, or be altered by, the expression of CSC-defining markers and their related pathways. These miRNAs can be utilized to affect stemness in multiple ways, including directly targeting CSCs and enhancing the efficacy of cancer therapeutics. This review highlights current studies regarding the roles of miRNAs in GI CSCs, and efforts towards the development of cancer therapeutics.

Targeting non-canonical activation of GLI1 by the SOX2-BRD4 transcriptional complex improves the efficacy of HEDGEHOG pathway inhibition in melanoma

Despite the development of new targeted and immune therapies, the prognosis of metastatic melanoma remains bleak. Therefore, it is critical to better understand the mechanisms controlling advanced melanoma to develop more effective treatment regimens. Hedgehog/GLI (HH/GLI) signaling inhibitors targeting the central pathway transducer Smoothened (SMO) have shown to be clinical efficacious in skin cancer; however, several mechanisms of non-canonical HH/GLI pathway activation limit their efficacy. Here, we identify a novel SOX2-BRD4 transcriptional complex driving the expression of GLI1, the final effector of the HH/GLI pathway, providing a novel mechanism of non-canonical SMO-independent activation of HH/GLI signaling in melanoma. Consistently, we find a positive correlation between the expression of GLI1 and SOX2 in human melanoma samples and cell lines. Further, we show that combined targeting of canonical HH/GLI pathway with the SMO inhibitor MRT-92 and of the SOX2-BRD4 complex using a potent Proteolysis Targeted Chimeras (PROTACs)-derived BRD4 degrader (MZ1), yields a synergistic anti-proliferative effect in melanoma cells independently of their BRAF, NRAS, and NF1 mutational status, with complete abrogation of GLI1 expression. Combination of MRT-92 and MZ1 strongly potentiates the antitumor effect of either drug as single agents in an orthotopic melanoma model. Together, our data provide evidence of a novel mechanism of non-canonical activation of GLI1 by the SOX2-BRD4 transcriptional complex, and describe the efficacy of a new combinatorial treatment for a subset of melanomas with an active SOX2-BRD4-GLI1 axis.

Acylglycerol kinase promotes the stemness of nasopharyngeal carcinoma cells by promoting β-catenin translocation to the nucleus through activating PI3K/Akt pathway

Recent evidences show that acylglycerol kinase (AGK) expression is related to the occurrence and development of various human cancers. However, its roles in nasopharyngeal carcinoma (NPC) progression are still unclear. This work aims to explore the roles of AGK in NPC cell stemness. It was shown that AGK expression was higher in NPC tissues compared to the adjacent tissues. Online dataset analysis revealed that AGK expression was negatively correlated with the overall survival of NPC patients. Gain and loss of functional experiments demonstrated that AGK positively regulated the stemness of NPC cells, as evident by the change of the tumor sphere-formation ability, ALDH1 activity and expression of stemness critical regulators. KEGG analysis were performed to determine the potential pathways of AGK involved in NPC cell stemness and showed that the PI3K/Akt pathway exhibited the most correlation with AGK expression. Further mechanistic studies confirmed that AGK promoted the stemness of NPC cells through activating the PI3K/Akt pathway, and thus enhancing β-catenin accumulation in nucleus. This study demonstrates a novel AGK/PI3K/Akt/β-catenin axis involving in NPC cell stemness.

MicroRNA in Gastric Cancer Development: Mechanisms and Biomarkers

Gastric cancer (GC) is one of the most common and difficult diseases to treat. The study of signaling pathway regulation by microRNA provides information on the mechanisms of GC development and is the basis for biomarker creation. In this study, a circuit of microRNA interactions with signaling pathways was constructed. The microRNAs, associated with metastasis and chemoresistance, are described. In most cases, microRNAs in GC regulate the Wnt/β-catenin, PI3K/AKT/mTOR, RAS/RAF/ERK/MAPK, NF-kB, TGF-β, and JAK/STAT pathways. Part of the microRNA acts on several target genes that function in different pathways. This often leads to an intensification of the induced processes. MicroRNAs have also been described that have the opposite effect on different pathways, causing different functional consequences. By acting on several target genes, or genes associated with several pathways, microRNAs can function in a signaling network. MicroRNAs associated with metastasis most often interact with the Wnt/β-catenin pathway. MicroRNAs affecting chemoresistance, in most cases, affect the regulators of apoptosis and are associated with the PI3K/AKT/mTOR pathway. The characteristics of microRNAs proposed as candidates for GC biomarkers were analyzed. The currently developed diagnostic and prognostic panels of microRNAs are also considered.

Conditional Deletion of Foxg1 Alleviates Demyelination and Facilitates Remyelination via the Wnt Signaling Pathway in Cuprizone-Induced Demyelinated Mice

The massive loss of oligodendrocytes caused by various pathological factors is a basic feature of many demyelinating diseases of the central nervous system (CNS). Based on a variety of studies, it is now well established that impairment of oligodendrocyte precursor cells (OPCs) to differentiate and remyelinate axons is a vital event in the failed treatment of demyelinating diseases. Recent evidence suggests that Foxg1 is essential for the proliferation of certain precursors and inhibits premature neurogenesis during brain development. To date, very little attention has been paid to the role of Foxg1 in the proliferation and differentiation of OPCs in demyelinating diseases of the CNS. Here, for the first time, we examined the effects of Foxg1 on demyelination and remyelination in the brain using a cuprizone (CPZ)-induced mouse model. In this work, 7-week-old Foxg1 conditional knockout and wild-type (WT) mice were fed a diet containing 0.2% CPZ w/w for 5 weeks, after which CPZ was withdrawn to enable remyelination. Our results demonstrated that, compared with WT mice, Foxg1-knockout mice exhibited not only alleviated demyelination but also accelerated remyelination of the demyelinated corpus callosum. Furthermore, we found that Foxg1 knockout decreased the proliferation of OPCs and accelerated their differentiation into mature oligodendrocytes both in vivo and in vitro. Wnt signaling plays a critical role in development and in a variety of diseases. GSK-3β, a key regulatory kinase in the Wnt pathway, regulates the ability of β-catenin to enter nuclei, where it activates the expression of Wnt target genes. We then used SB216763, a selective inhibitor of GSK-3β activity, to further demonstrate the regulatory mechanism by which Foxg1 affects OPCs in vitro. The results showed that SB216763 clearly inhibited the expression of GSK-3β, which abolished the effect of the proliferation and differentiation of OPCs caused by the knockdown of Foxg1. These results suggest that Foxg1 is involved in the proliferation and differentiation of OPCs through the Wnt signaling pathway. The present experimental results are some of the first to suggest that Foxg1 is a new therapeutic target for the treatment of demyelinating diseases of the CNS.

Three-Dimensional Culture Systems in Gastric Cancer Research

Gastric cancer (GC), which includes cancer of the esophagus, the oesophagogastric junction, and the stomach fundus, is highly deadly with strong regional influence, Asia being the most affected. GC is often detected at late stages, with 30% of metastatic cases at diagnosis. Many authors have devised models to both unravel the mechanisms of GC development and to evaluate candidate therapeutics. Among these models, 2D-cell cultures are progressively replaced by 3D-cell cultures that recapitulate, much more comprehensively, tumor cellular and genetic heterogeneity, as well as responsiveness to environmental changes, such as exposure to drugs or irradiation. With respect to the specifics of GC, there are high hopes from such model systems, especially with the aim of identifying prognostic markers and novel drug targets.

Combined treatment with CBP and BET inhibitors reverses inadvertent activation of detrimental super enhancer programs in DIPG cells

Diffuse intrinsic pontine gliomas (DIPG) are the most aggressive brain tumors in children with 5-year survival rates of only 2%. About 85% of all DIPG are characterized by a lysine-to-methionine substitution in histone 3, which leads to global H3K27 hypomethylation accompanied by H3K27 hyperacetylation. Hyperacetylation in DIPG favors the action of the Bromodomain and Extra-Terminal (BET) protein BRD4, and leads to the reprogramming of the enhancer landscape contributing to the activation of DIPG super enhancer-driven oncogenes. The activity of the acetyltransferase CREB-binding protein (CBP) is enhanced by BRD4 and associated with acetylation of nucleosomes at super enhancers (SE). In addition, CBP contributes to transcriptional activation through its function as a scaffold and protein bridge. Monotherapy with either a CBP (ICG-001) or BET inhibitor (JQ1) led to the reduction of tumor-related characteristics. Interestingly, combined treatment induced strong cytotoxic effects in H3.3K27M-mutated DIPG cell lines. RNA sequencing and chromatin immunoprecipitation revealed that these effects were caused by the inactivation of DIPG SE-controlled tumor-related genes. However, single treatment with ICG-001 or JQ1, respectively, led to activation of a subgroup of detrimental super enhancers. Combinatorial treatment reversed the inadvertent activation of these super enhancers and rescued the effect of ICG-001 and JQ1 single treatment on enhancer-driven oncogenes in H3K27M-mutated DIPG, but not in H3 wild-type pedHGG cells. In conclusion, combinatorial treatment with CBP and BET inhibitors is highly efficient in H3K27M-mutant DIPG due to reversal of inadvertent activation of detrimental SE programs in comparison with monotherapy.

MiR-216a-3p suppresses the proliferation and invasion of cervical cancer through downregulation of ACTL6A-mediated YAP signaling

The tumor-suppressive role of microRNA-216a-3p (miR-216a-3p) has been evidenced in multiple tumors. Yet, the relevance of miR-216a-3p in cervical cancer remains undermined. The current study was designed to determine the expression and potential function of miR-216a-3p in cervical cancer. Expression of miR-216a-3p was markedly decreased in cervical cancer and functional assays revealed an inhibitory effect of miR-216a-3p on the proliferation, colony formation, and invasion of cervical cancer. Actin-like 6A (ACTL6A) was identified as a target gene of miR-216a-3p. Elevated ACTL6A expression was detected in cervical cancer, and ACTL6A inhibition exhibited a tumor-suppressive effect. ACTL6A inhibition increased yes-associated protein (YAP) phosphorylation and downregulated YAP-mediated transcriptional activity. ACTL6A restoration or YAP reactivation partially abrogated the miR-216a-3p-mediated antitumor effect in cervical cancer cells. Taken together, these data demonstrate that miR-216a-3p acts as a potential tumor-suppressive miRNA in cervical cancer, which exerts its function through inhibition of YAP signaling via targeting ACTL6A.

Transcriptional factor Yin Yang 1 facilitates the stemness of ovarian cancer via suppressing miR-99a activity through enhancing its deacetylation level

The promoting effects of transcriptional factor Yin Yang 1 (YY1) have been confirmed in various tumors, however, its roles in ovarian cancer (OC) progression are still unclear. Here, Kaplan-Meier Plotter analysis was used to determine the correlation between YY1 expression and the survival of OC patients. It was found that YY1 expression was negatively correlated with the overall survival, progression-free survival and post-progression survival of OC patients. Functional experiments indicated that overexpression of YY1 facilitated the stemness of OC cells, while YY1 knockdown reduced it. MiRNAs-based RNA-sequencing analysis showed that miR-99a was the mostly upregulated miRNA in RNA extracted from OC cells with YY1 knockdown. Mechanistic studies revealed that YY1 recruited (Histone deacetylase) HDAC5 to the promoter of miR-99a, and subsequently enhanced miR-99a deacetylation level and decreased miR-99a level. Additionally, overexpression of miR-99a or knockdown of HDAC5 attenuated the promoting effects of YY1 on the stemness of OC cells. This work firstly indicated a novel YY1/miR-99a axis, which promotes the stemness of OC cells.

Wnt-regulating microRNAs role in gastric cancer malignancy

Gastric cancer (GC) is responsible for high morbidity and mortality worldwide. This cancer claims fifth place among other cancers. There are a number of factors associated with GC development such as alcohol consumption and tobacco smoking. It seems that genetic factors play significant role in GC malignancy and progression. MicroRNAs (miRs) are short non-coding RNA molecules with negative impact on the expression of target genes. A variety of studies have elucidated the potential role of miRs in GC growth. Investigation of molecular pathways has revealed that miRs function as upstream modulators of Wnt signaling pathway. This signaling pathway involves in important biological processes such as cell proliferation and differentiation, and its dysregulation is associated with GC invasion. At the present review, we demonstrate that how miRs regulate Wnt signaling pathway in GC malignancy.

BRD4 promotes glioma cell stemness via enhancing miR-142-5p-mediated activation of Wnt/β-catenin signaling

The bromodomain protein BRD4 exerts carcinogenic effects in many cancers. However, its roles in glioma occurrence are still confused. Here, it is found that BRD4 expression is increased in glioma tissues and negatively correlated with the overall survival of glioma patients. We construct cellular experiments indicating that BRD4 promotes glioma cell stemness by analyzing ALDH1 activity, master stemness regulator expression, and sphere formation ability. Mechanistically, BRD4 knockdown triggers a switch of miR-142-5p promoter methylation, which targets Wnt3a and thus further inactivates Wnt/β-catenin signaling. Importantly, inhibition of miR-142-5p or reactivation of Wnt/β-catenin signaling rescues the inhibition of BRD4 knockdown on glioma cell stemness. As a result, these results not only indicate an unforeseen connection between BRD4, miR-142-5p, and Wnt/β-catenin signaling, but also reveal a promising epigenetic-based therapeutic strategy that might be explored for glioma patients.

A Positive Tetraspanin 8 (TSPAN8)/β-Catenin Regulatory Loop Enhances the Stemness of Colorectal Cancer Cells

BACKGROUND The expression of TSPAN8 (tetraspanin 8) is upregulated in colorectal cancer; however, its roles in colorectal cancer progression are never been revealed. This work aimed to investigate TSPAN8 effects and the molecular basis in regulating colorectal cancer stemness. MATERIAL AND METHODS Real-time quantitative polymerase chain reaction and western blot analysis were used to detect the expression of TSPAN8 expression in clinical samples and the expression of stemness genes in colorectal cancer cells. Sphere forming analysis was performed to detect TSPAN8 effects on sphere forming ability of colorectal cancer cells. Co-IP and ChIP analysis were performed to confirm the molecular basis contributing to TSPAN8-mediated effects on colorectal cancer stemness. RESULTS TSPAN8 expression is increased in colorectal cancer tissues. Knockdown of TSPAN8 reduced the expression of stemness genes and sphere forming capacity in colorectal cancer cells. Mechanistically, TSPAN8 directly interacted ß-catenin and enhanced its protein expression, which is necessary for TSPAN8-mediated effects on colorectal cancer stemness. Conversely, ß-catenin directly bound to TSPAN8 promoter and enhanced TSPAN8 transcription. CONCLUSIONS TSPAN8 promotes colorectal cancer stemness through a positive TSPAN8/ß-catenin regulatory loop.

Bromodomain and Extraterminal Proteins as Novel Epigenetic Targets for Renal Diseases

Epigenetic mechanisms, especially DNA methylation and histone modifications, are dynamic processes that regulate the gene expression transcriptional program in normal and diseased states. The bromodomain and extraterminal (BET) protein family (BRD2, BRD3, BRD4, and BRDT) are epigenetic readers that, via bromodomains, regulate gene transcription by binding to acetylated lysine residues on histones and master transcriptional factors. Experimental data have demonstrated the involvement of some BET proteins in many pathological conditions, including tumor development, infections, autoimmunity, and inflammation. Selective bromodomain inhibitors are epigenetic drugs that block the interaction between BET proteins and acetylated proteins, thus exerting beneficial effects. Recent data have described the beneficial effect of BET inhibition on experimental renal diseases. Emerging evidence underscores the importance of environmental modifications in the origin of pathological features in chronic kidney diseases (CKD). Several cellular processes such as oxidation, metabolic disorders, cytokines, inflammation, or accumulated uremic toxins may induce epigenetic modifications that regulate key processes involved in renal damage and in other pathological conditions observed in CKD patients. Here, we review how targeting bromodomains in BET proteins may regulate essential processes involved in renal diseases and in associated complications found in CKD patients, such as cardiovascular damage, highlighting the potential of epigenetic therapeutic strategies against BET proteins for CKD treatment and associated risks.