Overexpression of TRIM24 is associated with the onset and progress of human hepatocellular carcinoma. PLoS One. 2014;9:e85462. [PMID: 24409330 PMCID: PMC3883694 DOI: 10.1371/journal.pone.0085462]

The tripartite motif-containing 24 is a multifunctional player in human cancer

Tripartite motif-containing 24 (TRIM24), also known as transcriptional intermediary factor 1α (TIF1α), is the founding member of TIF1 family. Recent evidence indicates that aberrant expression of TRIM24, functions as an oncogene, is associated with poor prognosis across various cancer types. TRIM24 exhibits a multifaceted structure comprising an N-terminal TRIM region with a RING domain, B-box type 1 and type 2 domains, and a coiled-coil region, as well as a C-terminal plant-homeodomain (PHD)-bromodomain. The bromodomain serves as a 'reader' of epigenetic histone marks, regulating chromatin structure and gene expression by linking associated proteins to acetylated nucleosomal targets, thereby controlling transcription of genes. Notably, bromodomains have emerged as compelling targets for cancer therapeutic development. In addition, TRIM24 plays specialized roles as a signal transduction molecule, orchestrating various cellular signaling cascades in cancer cells. Herein, we review the recent advancements in understanding the functions of TRIM24, and demonstrate the research progress in utilizing TRIM24 as a target for cancer therapy.

APIR: Aggregating Universal Proteomics Database Search Algorithms for Peptide Identification with FDR Control

Advances in mass spectrometry (MS) have enabled high-throughput analysis of proteomes in biological systems. The state-of-the-art MS data analysis relies on database search algorithms to quantify proteins by identifying peptide-spectrum matches (PSMs), which convert mass spectra to peptide sequences. Different database search algorithms use distinct search strategies and thus may identify unique PSMs. However, no existing approaches can aggregate all user-specified database search algorithms with a guaranteed increase in the number of identified peptides and a control on the false discovery rate (FDR). To fill in this gap, we proposed a statistical framework, Aggregation of Peptide Identification Results (APIR), that is universally compatible with all database search algorithms. Notably, under an FDR threshold, APIR is guaranteed to identify at least as many, if not more, peptides as individual database search algorithms do. Evaluation of APIR on a complex proteomics standard dataset showed that APIR outpowers individual database search algorithms and empirically controls the FDR. Real data studies showed that APIR can identify disease-related proteins and post-translational modifications missed by some individual database search algorithms. The APIR framework is easily extendable to aggregating discoveries made by multiple algorithms in other high-throughput biomedical data analysis, e.g., differential gene expression analysis on RNA sequencing data. The APIR R package is available at https://github.com/yiling0210/APIR.

Intricate confrontation: Research progress and application potential of TRIM family proteins in tumor immune escape

BACKGROUND

Tripartite motif (TRIM) family proteins have more than 80 members and are widely found in various eukaryotic cells. Most TRIM family proteins participate in the ubiquitin-proteasome degradation system as E3-ubiquitin ligases; therefore, they play pivotal regulatory roles in the occurrence and development of tumors, including tumor immune escape. Due to the diversity of functional domains of TRIM family proteins, they can extensively participate in multiple signaling pathways of tumor immune escape through different substrates. In current research and clinical contexts, immune escape has become an urgent problem. The extensive participation of TRIM family proteins in curing tumors or preventing postoperative recurrence and metastasis makes them promising targets.

AIM OF REVIEW

The aim of the review is to make up for the gap in the current research on TRIM family proteins and tumor immune escape and propose future development directions according to the current progress and problems.

KEY SCIENTIFIC CONCEPTS OF REVIEW

This up-to-date review summarizes the characteristics and biological functions of TRIM family proteins, discusses the mechanisms of TRIM family proteins involved in tumor immune escape, and highlights the specific mechanism from the level of structure-function-molecule-pathway-phenotype, including mechanisms at the level of protein domains and functions, at the level of molecules and signaling pathways, and at the level of cells and microenvironments. We also discuss the application potential of TRIM family proteins in tumor immunotherapy, such as possible treatment strategies for combination targeting TRIM family protein drugs and checkpoint inhibitors for improving cancer treatment.

Genome-wide CRISPR-Cas9 screen analyzed by SLIDER identifies network of repressor complexes that regulate TRIM24

TRIM24 is an oncogenic chromatin reader that is frequently overexpressed in human tumors and associated with poor prognosis. However, TRIM24 is rarely mutated, duplicated, or rearranged in cancer. This raises questions about how TRIM24 is regulated and what changes in its regulation are responsible for its overexpression. Here, we perform a genome-wide CRISPR-Cas9 screen by fluorescence-activated cell sorting (FACS) that nominated 220 negative regulators and elucidated a regulatory network that includes the KAP1 corepressor, CNOT deadenylase, and GID/CTLH E3 ligase. Knocking out required components of these three complexes caused TRIM24 overexpression, confirming their negative regulation of TRIM24. Our findings identify regulators of TRIM24 that nominate previously unexplored contexts for this oncoprotein in biology and disease. These findings were enabled by SLIDER, a new scoring system designed and vetted in our study as a broadly applicable tool for analysis of CRISPR screens performed by FACS.

TRIM24 is critical for the cellular response to DNA double-strand breaks through regulating the recruitment of MRN complex

The MRE11-RAD50-NBS1 (MRN) complex plays a crucial role in DNA double-strand breaks (DSBs) sensing and initiation of signaling cascades. However, the precise mechanisms by which the recruitment of MRN complex is regulated has yet to be elucidated. Here, we identified TRIpartite motif-containing protein 24 (TRIM24), a protein considered as an oncogene overexpressed in cancers, as a novel signaling molecule in response to DSBs. TRIM24 is essential for DSBs-induced recruitment of MRN complex and activation of downstream signaling. In the absence of TRIM24, MRN mediated DSBs repair is remarkably diminished. Mechanistically, TRIM24 is phosphorylated by ataxia-telangiectasia mutated (ATM) and then recruited to DSBs sites, facilitating the accumulation of the MRN components to chromatin. Depletion of TRIM24 sensitizes human hepatocellular carcinoma cells to cancer therapy agent-induced apoptosis and retards the tumor growth in a subcutaneous xenograft tumor mouse model. Together, our data reveal a novel function of TRIM24 in response to DSBs through regulating the MRN complex, which suggests that TRIM24 may be a potential therapeutic molecular target for tumor treatment.

PROTACs in Epigenetic Cancer Therapy: Current Status and Future Opportunities

The epigenetic regulation of gene functions has been proven to be strongly associated with the development and progression of cancer. Reprogramming the cancer epigenome landscape is one of the most promising target therapies in both treatments and in reversing drug resistance. Proteolytic targeted chimeras (PROTACs) are an emerging therapeutic modality for selective degradation via the native ubiquitin-proteasome system. Rapid advances in PROTACs have facilitated the exploration of targeting epigenetic proteins, a lot of PROTAC degraders have already been designed in the field of epigenetic cancer therapy, and PROTACs targeting epigenetic proteins can better exploit target druggability and improve the mechanistic understanding of the epigenetic regulation of cancer. Thus, this review focuses on the progress made in the development of PROTAC degraders and PROTAC drugs targeting epigenetics in cancer and discusses challenges and future opportunities for the field.

miR-339-3p inhibits cell growth and epithelial-mesenchymal transition in nasopharyngeal carcinoma by modulating the KAT6A/TRIM24 axis

OBJECTIVE

To explore the effect and mechanism of the miR-339-3p/KAT6A/TRIM24 axis in nasopharyngeal carcinoma (NPC) cell growth and epithelial-mesenchymal transition (EMT) progression.

METHODS

CNE2 and 5-8F NPC cell lines were transfected with miR-339-3p-mimic or sh-KAT6A alone or co-transfected with miR-339-3p-mimic and oe-KAT6A. The expression levels of miR-339-3p, KAT6A, TRIM24, and EMT-related proteins were assessed, in addition to cell biological behaviors. Then, the relationship between miR-339-3p and KAT6A was predicted and validated. The correlations between miR-339-3p and KAT6A or between KAT6A and TRIM24 were analyzed by Pearson coefficient and the enrichment of H3K23ac in TRIM24 promoter region was measured by chromatin immunoprecipitation.

RESULTS

miR-339-3p was downregulated, but KAT6A and TRIM24 were highly expressed in NPC cells and tissues. Upregulated miR-339-3p or downregulated KAT6A could inhibit the growth and EMT of NPC cells. Further experiments showed that miR-339-3p regulated NPC cell growth and EMT by mediating KAT6A in a targeted fashion. KAT6A was positively correlated with TRIM24, and the enrichment of H3K23ac was much higher in NPC tissues. miR-339-3p suppressed the growth and EMT of NPC cells by the KAT6A/TRIM24 axis. In a xenograft study, miR-339-3p overexpression inhibited NPC tumor growth in vivo.

CONCLUSION

Conclusively, miR-339-3p inhibited the growth and EMT of NPC cells via the KAT6A/TRIM24 axis.

Identification of Histone Peptide Binding Specificity and Small-Molecule Ligands for the TRIM33α and TRIM33β Bromodomains

TRIM33 is a member of the tripartite motif (TRIM) family of proteins, some of which possess E3 ligase activity and are involved in the ubiquitin-dependent degradation of proteins. Four of the TRIM family proteins, TRIM24 (TIF1α), TRIM28 (TIF1β), TRIM33 (TIF1γ) and TRIM66, contain C-terminal plant homeodomain (PHD) and bromodomain (BRD) modules, which bind to methylated lysine (KMe_n) and acetylated lysine (KAc), respectively. Here we investigate the differences between the two isoforms of TRIM33, TRIM33α and TRIM33β, using structural and biophysical approaches. We show that the N1039 residue, which is equivalent to N140 in BRD4(1) and which is conserved in most BRDs, has a different orientation in each isoform. In TRIM33β, this residue coordinates KAc, but this is not the case in TRIM33α. Despite these differences, both isoforms show similar affinities for H3_1-27K18Ac, and bind preferentially to H3_1-27K9Me₃K18Ac. We used this information to develop an AlphaScreen assay, with which we have identified four new ligands for the TRIM33 PHD-BRD cassette. These findings provide fundamental new information regarding which histone marks are recognized by both isoforms of TRIM33 and suggest starting points for the development of chemical probes to investigate the cellular function of TRIM33.

TRIM family contribute to tumorigenesis, cancer development, and drug resistance

The tripartite-motif (TRIM) family represents one of the largest classes of putative single protein RING-finger E3 ubiquitin ligases. TRIM family is involved in a variety of cellular signaling transductions and biological processes. TRIM family also contributes to cancer initiation, progress, and therapy resistance, exhibiting oncogenic and tumor-suppressive functions in different human cancer types. Moreover, TRIM family members have great potential to serve as biomarkers for cancer diagnosis and prognosis. In this review, we focus on the specific mechanisms of the participation of TRIM family members in tumorigenesis, and cancer development including interacting with dysregulated signaling pathways such as JAK/STAT, PI3K/AKT, TGF-β, NF-κB, Wnt/β-catenin, and p53 hub. In addition, many studies have demonstrated that the TRIM family are related to tumor resistance; modulate the epithelial–mesenchymal transition (EMT) process, and guarantee the acquisition of cancer stem cells (CSCs) phenotype. In the end, we havediscussed the potential of TRIM family members for cancer therapeutic targets.

Recent Advances in PROTACs for Drug Targeted Protein Research

Proteolysis-targeting chimera (PROTAC) is a heterobifunctional molecule. Typically, PROTAC consists of two terminals which are the ligand of the protein of interest (POI) and the specific ligand of E3 ubiquitin ligase, respectively, via a suitable linker. PROTAC degradation of the target protein is performed through the ubiquitin–proteasome system (UPS). The general process is that PROTAC binds to the target protein and E3 ligase to form a ternary complex and label the target protein with ubiquitination. The ubiquitinated protein is recognized and degraded by the proteasome in the cell. At present, PROTAC, as a new type of drug, has been developed to degrade a variety of cancer target proteins and other disease target proteins, and has shown good curative effects on a variety of diseases. For example, PROTACs targeting AR, BR, BTK, Tau, IRAK4, and other proteins have shown unprecedented clinical efficacy in cancers, neurodegenerative diseases, inflammations, and other fields. Recently, PROTAC has entered a phase of rapid development, opening a new field for biomedical research and development. This paper reviews the various fields of targeted protein degradation by PROTAC in recent years and summarizes and prospects the hot targets and indications of PROTAC.

TRIM24 Expression as an Independent Biomarker for Prognosis and Tumor Recurrence in HNSCC

Background: Head and neck squamous cell carcinomas (HNSCCs) are among the most common cancers in humans worldwide and have a rather poor prognosis. TRIM24 has various intracellular functions and was identified in other cancer entities as a poor prognostic factor for patients. Methods: The expression of TRIM24 was evaluated by using immunohistochemistry. We used a large and representative cohort of 341 HNSCC patients. Data derived from immunohistochemistry evaluation was correlated with clinicopathological data from HNSCC patients. Results: The TRIM24 expression in HNSCC primary tumors is negatively correlated with the p16 status of the tumor tissues. Primary tumors of patients who developed a local recurrence were significantly more often positive for TRIM24. Kaplan–Meier analyses and Cox regression showed that patients with TRIM24 expressing tumors have significantly worse overall survival and progression-free survival and that TRIM24 expression is independent of other established risk factors. Conclusions: TRIM24 might be a new prognostic biomarker for the survival prognosis and early detection of local recurrences in HNSCC patients. It could be used for risk stratification of HNSCC patients and to identify those patients who are more prone to develop a local recurrence and therefore could profit from more frequent follow-up examinations.

High expression of TRIM24 predicts worse prognosis and promotes proliferation and metastasis of epithelial ovarian cancer

BACKGROUND

Tripartite Motif-Containing 24 (TRIM24) is a member of the tripartite motif family. TRIM24 is claimed aberrantly activated in a number of cancers, such as breast cancer, prostate cancer and lung cancer. However, the expression of TRIM24 in epithelial ovarian cancer (EOC) and its relationship with prognosis remain unclear. In this study, we investigated the expression pattern and underlying clinical significance of TRIM24 in EOC.

RESULTS

Data from Oncomine and immunohistochemistry of tissue samples demonstrated that TRIM24 expression was obviously elevated in ovarian carcinoma compared with normal ovary tissues. Elevated TRIM24 expression was closely correlated with serum CA-125 (P = 0.0294), metastasis (P = 0.0022), FIGO (International Federation of Gynecology and Obstetrics) stage (P = 0.0068) and Ki-67 level (P = 0.0395). Kaplan-Meier survival analysis found that TRIM24 expression increased inversely with the clinical prognosis of patients with EOC. Moreover, colony formation and CCK-8 assays showed that TRIM24 promoted EOC cell growth, and tumorigenic experiments in nude mice showed that TRIM24 knockdown inhibited tumor growth in vivo. The Spearman's correlations revealed that the expression of TRIM24 was significantly correlated with levels of Ki-67 (P = 0.01), at a correlation coefficient of 0.517. Wound-healing and transwell migration assays demonstrated TRIM24 facilitated cell migration. Mechanism studies showed that TRIM24 could promote the phosphorylation level of Akt and the process of EMT.

CONCLUSION

Our results confirmed that TRIM24 could predict poor prognosis of EOC patients and promote tumor progression by regulating Akt pathway and EMT. TRIM24 may be used as a new prognostic marker for EOC and may provide a new strategy for targeted therapy of epithelial ovarian cancer.

Prognostic role of tripartite motif containing 24 in various human solid malignant neoplasms: An updated meta-analysis and systematic review

BACKGROUND

Currently, clinical studies of tripartite motif containing 24 (TRIM24) on human solid malignant neoplasms were developing, but the prognosis value of TRIM24 continues to be controversial. The aim of our study is to explore the prognostic effect of TRIM24 in various human solid malignant neoplasms.

METHODS

We performed a comprehensive research for eligible studies which evaluated the prognostic roles of TRIM24 in cancer patients based on PubMed, Embase, Web of Science, and China National Knowledge Infrastructure. The hazard ratios (HRs) with 95% confidence intervals (CIs) for various malignances were extracted from eligible studies.

RESULTS

A total of 13 studies with 1909 patients were enrolled in this analysis. Combined analyses showed that high expression of TRIM24 significantly predicted poorer overall survival both in univariate analysis (HR = 1.61, 95% CI 1.21-2.15, P = .001) and multivariate analysis (HR = 2.19, 95% CI 1.10-4.38, P = .026). In stratified analyses, high TRIM24 expression level predicted even worse overall survival in hormone-related cancers (HR = 1.92, 95% CI 1.28-2.86, P = .001). Although, expression of TRIM24 failed to show a significant relation with progression-free survival/disease-free survival/recurrence-free survival (HR = 1.42, 95% CI 0.93-2.16, P = .106), high expression predicted significant worse progression-free survival/disease-free survival/recurrence-free survival in hormone-related cancer (HR = 1.71, 95% CI 1.12-2.59, P = .013).

CONCLUSION

TRIM24 could serve as a new biomarker for patients with solid malignancies and could be a potential therapeutic target for patients especially for patients with hormone-related malignancies.

Functional Roles of Bromodomain Proteins in Cancer

Histone acetylation is generally associated with an open chromatin configuration that facilitates many cellular processes including gene transcription, DNA repair, and DNA replication. Aberrant levels of histone lysine acetylation are associated with the development of cancer. Bromodomains represent a family of structurally well-characterized effector domains that recognize acetylated lysines in chromatin. As part of their fundamental reader activity, bromodomain-containing proteins play versatile roles in epigenetic regulation, and additional functional modules are often present in the same protein, or through the assembly of larger enzymatic complexes. Dysregulated gene expression, chromosomal translocations, and/or mutations in bromodomain-containing proteins have been correlated with poor patient outcomes in cancer. Thus, bromodomains have emerged as a highly tractable class of epigenetic targets due to their well-defined structural domains, and the increasing ease of designing or screening for molecules that modulate the reading process. Recent developments in pharmacological agents that target specific bromodomains has helped to understand the diverse mechanisms that bromodomains play with their interaction partners in a variety of chromatin processes, and provide the promise of applying bromodomain inhibitors into the clinical field of cancer treatment. In this review, we explore the expression and protein interactome profiles of bromodomain-containing proteins and discuss them in terms of functional groups. Furthermore, we highlight our current understanding of the roles of bromodomain-containing proteins in cancer, as well as emerging strategies to specifically target bromodomains, including combination therapies using bromodomain inhibitors alongside traditional therapeutic approaches designed to re-program tumorigenesis and metastasis.

Regulation of p53 by E3s

More than 40 years of research on p53 have given us tremendous knowledge about this protein. Today we know that p53 plays a role in different biological processes such as proliferation, invasion, pluripotency, metabolism, cell cycle control, ROS (reactive oxygen species) production, apoptosis, inflammation and autophagy. In the nucleus, p53 functions as a bona-fide transcription factor which activates and represses transcription of a number of target genes. In the cytoplasm, p53 can interact with proteins of the apoptotic machinery and by this also induces cell death. Despite being so important for the fate of the cell, expression levels of p53 are kept low in unstressed cells and the protein is largely inactive. The reason for the low expression level is that p53 is efficiently degraded by the ubiquitin-proteasome system and the vast inactivity of the tumor suppressor protein under normal growth conditions is due to the absence of activating and the presence of inactivating posttranslational modifications. E3s are important enzymes for these processes as they decorate p53 with ubiquitin and small ubiquitin-like proteins and by this control p53 degradation, stability and its subcellular localization. In this review, we provide an overview about E3s that target p53 and discuss the connection between p53, E3s and tumorigenesis.

Overexpression of the TRIM24 E3 Ubiquitin Ligase is Linked to Genetic Instability and Predicts Unfavorable Prognosis in Prostate Cancer

Tripartite motif containing 24 (TRIM24) is a multifunctional protein involved in p53 degradation, chromatin binding, and transcriptional modulation of nuclear receptors. Emerging research has revealed that upregulation of TRIM24 in numerous tumor types is linked to poor prognosis, attributing an important role to TRIM24 in tumor biology. In order to better understand the role of TRIM24 in prostate cancer, we analyzed its immunohistochemical expression on a tissue microarray containing >17,000 prostate cancer specimens. TRIM24 immunostaining was detectable in 61% of 15,321 interpretable cancers, including low expression in 46% and high expression in 15% of cases. TRIM24 upregulation was associated with high Gleason grade, advanced pathologic tumor stage, lymph node metastasis, higher preoperative prostate-specific antigen level, increased cell proliferation as well as increased genomic instability, and predicted prognosis independent of clinicopathologic parameters available at the time of the initial biopsy (all P<0.0001). TRIM24 upregulation provides additional prognostic information in prostate cancer, particularly in patients with low Gleason grade tumors who may be eligible for active surveillance strategies, suggesting promising potential for TRIM24 in the routine diagnostic work-up of these patients.

Knockdown of TRIM24 suppresses growth and induces apoptosis in acute myeloid leukemia through downregulation of Wnt/GSK-3β/β-catenin signaling

Tripartite motif-containing protein 24 (TRIM24) has currently emerged as a crucial cancer-related gene present in a wide range of human cancer types. However, the involvement of TRIM24 in acute myeloid leukemia (AML) has not been well investigated. The present study aims to investigate the significance, cellular function, and potential regulatory mechanism of TRIM24 in AML. We found that TRIM24 expression was significantly upregulated in AML compared with normal tissues. AML patients with low expression of TRIM24 had higher survival rates than those expressing TRIM24 at higher levels. High expression of TRIM24 was also detected in AML cells and its knockdown markedly restricted proliferation and promoted apoptosis in AML cells. Further investigation revealed that TRIM24 contributed to the regulation of Wnt/β-catenin signaling, which was associated with modulating the phosphorylation status of glycogen synthase kinase-3β (GSK-3β). Inactivation of GSK-3β partially reversed the TRIM24 knockdown-mediated antitumor effects observed in AML cells. Furthermore, knockdown of TRIM24 retarded the growth of AML-derived xenograft tumors in nude mice in vivo. Overall, these findings demonstrate that knockdown of TRIM24 impedes the AML tumor growth through the modulation of Wnt/GSK-3β/β-catenin signaling. These findings highlight the potential TRIM24 as an attractive anticancer target to treat AML.

Tripartite motif containing 24 regulates cell proliferation in colorectal cancer through YAP signaling

The protein, tripartite motif containing 24 (TRIM24) is a member of the TRIM protein family, and acts as a critical co‐regulator of multiple nuclear receptors. TRIM24 is dysregulated in many cancers, including colorectal carcinoma. However, its biological functions and molecular mechanisms with respect to colorectal carcinoma are still largely unknown. In the current study, we found that TRIM24 promotes YAP signaling for driving cell proliferation in colorectal cancer. TRIM24 was significantly upregulated in colorectal carcinoma, and its expression was negatively correlated with the survival of patients. Depletion of TRIM24 impaired the ability of the cancer cells to proliferate and form colonies. Furthermore, this study also revealed the mechanism underlying the recruitment of TRIM24 by the DANCR/KAT6A complex, which is bound to acetylated lysine 23 of histone H3 (H3K23), resulting in binding to the YAP promoter and activation of YAP transcription that ultimately enhances the proliferation of colorectal cancer cells. Our results revealed a novel mechanism involving TRIM24‐YAP signaling for the regulation of colorectal cancer. We also identified TRIM24 as a potential therapeutic molecule for targeting colorectal cancer.

Dual Role For A MEK Inhibitor As A Modulator Of Inflammation And Host Defense Mechanisms With Potential Therapeutic Application In COPD

Background

Unlike p38 mitogen-activated protein Kinases (MAPK) that has been extensively studied in the context of lung-associated pathologies in COPD, the role of the dual-specificity mitogen-activated protein kinase kinase (MEK1/2) or its downstream signaling molecule extracellular signal-regulated kinases 1/2 (ERK1/2) in COPD is poorly understood.

Objectives

The aim of this study was to address whether MEK1/2 pathway activation is linked to COPD and that targeting this pathway can improve lung inflammation through decreased immune-mediated inflammatory responses without compromising bacterial clearance.

Methods

Association of MEK1/2 pathway activation to COPD was investigated by immunohistochemistry using lung tissue biopsies from COPD and healthy individuals and through analysis of sputum gene expression data from COPD patients. The anti-inflammatory effect of MEK1/2 inhibition was assessed on cytokine release from lipopolysaccharide-stimulated alveolar macrophages. The effect of MEK1/2 inhibition on bacterial clearance was assessed using Staphylococcus aureus killing assays with RAW 264.7 macrophage cell line and human neutrophils.

Results

We report here MEK1/2 pathway activation demonstrated by increased pERK1/2 staining in bronchial epithelium and by the presence of MEK gene activation signature in sputum samples from COPD patients. Inhibition of MEK1/2 resulted in a superior anti-inflammatory effect in human alveolar macrophages in comparison to a p38 inhibitor. Furthermore, MEK1/2 inhibition led to an increase in bacterial killing in human neutrophils and RAW 264.7 cells that was not observed with the p38 inhibitor.

Conclusion

Our data demonstrate the activation of MEK1/2 pathway in COPD and highlight a dual function of MEK1/2 inhibition in improving host defense responses whilst also controlling inflammation.

TRIM13 inhibits cell migration and invasion in clear-cell renal cell carcinoma

TRIM13, a member of the TRIM family, is a RING domain containing E3 ubiquitin ligase which plays critical roles in diverse cellular processes including cell death, cancer and antiviral immunity. However, its expression and molecular mechanism on renal cell carcinoma (RCC) have not been characterized. This study explored the clinical significance and biological function of TRIM13 in human RCC. Western blot analyses and Immunohistochemical were performed in RCC tissues. The clinical relevance of TRIM13 in RCC was evaluated by immunohistochemical staining using tissue microarray. The role of TRIM13 in migration was studied in renal cell carcinoma cell lines of 786-O through knocking down TRIM13 with siRNA and over-expression of TRIM13. The regulation of TRIM13 on migration and invasion were determined by wound-healing and transwell assays. Western blot analyses showed that TRIM13 expression was dramatically decreased in RCC tissues compared with adjacent non-tumorous tissues. Up-regulation of TRIM13 in 786-O cells resulted in decreased NF-kB, MMP-9 and p-AKT levels and the capability for migration and invasion. In contrast, the ectopic expression of TRIM13 decreased the migration and invasion ability of 786-O cells. These findings indicate that TRIM13 decreases RCC metastasis and invasion may serve as a candidate RCC prognostic marker and a potential therapeutic target.

Tripartite motif-containing 15 overexpression in non-small cell lung cancer is associated with poor patient prognoses

Purpose: This study aimed to comprehensively investigate the differential expression and prognostic indicators of the tripartite motif-containing (TRIM) gene family in non-small cell lung cancer (NSCLC). Methods: The Cancer Genome Atlas (TCGA) Research Network and three datasets from Gene Expression Omnibus (GEO) database were used to assess TRIM gene family expression patterns in NSCLC. Quantitative real-time PCR and immunohistochemistry (IHC) were conducted to confirm differentially expressed genes (DEGs). Kaplan-Meier survival analysis and univariate Cox regression analysis were carried out to analyze the association between TRIM gene expression and NSCLC prognoses. Gene set enrichment analysis (GSEA) was carried on for the predict the biological processes. Results: Of the 78 TRIM family members measured, TRIM15 was selected due to the DEGs and the prognostic value regarding NSCLC. In lung squamous cell carcinoma (LUSC), the Log₂ fold change (Log₂FC) of TRIM15 was 5.16 (p= 0.00575), whereas in lung adenocarcinoma (LUAD), it was 6.37 (p =6.78E-07). TRIM15 upregulation was related to poor prognoses in both LUSC (HR 1.353; 95%CI 1.023-1.789; p =0.034) and LUAD (HR 1.560; 95%CI 1.159-2.101; p =0.003). Using immunohistochemistry, TRIM15 expression was significantly higher in NSCLC tissues compared with that of matched normal tissues (p =0.0009), and similar findings were generated with tissue microarray analysis (p<0.0001). Conclusion: TRIM15 could act as a diagnostic predictor or therapeutic target for lung cancer treatments.

Elevated TRIM23 expression predicts poor prognosis in Chinese gastric cancer

The gene TRIM23 (tripartite motif containing 23) is a member of the tripartite motif (TRIM) family whose expression putatively participates in many pathophysiological processes. Nonetheless, the role of TRIM23 in gastric cancer (GC) remains uncertain. Our study evaluated the expression of TRIM23 in GC tissues and cell lines, and investigated an association between TRIM23 and survival. In the present study, our results demonstrated that TRIM23 mRNA and protein were frequently over-expressed in GC cell lines and GC tissues. High level of TRIM23 protein correlated with tumor size, tumor-node-metastasis (TNM) stage, depth of invasion, lymph node metastasis (LNM), tumor differentiation, and nerve invasion. Compared with the low TRIM23 protein group, the high TRIM23 protein group was significantly associated with worse prognosis of GC patients. Consistently, the KM-plot database suggested that high TRIM23 mRNA expression was also linked to a poor prognosis in GC patients both in positive and negative subgroups of human epidermal growth factor receptor 2 (HER2). But in the HER2 positive subgroup, the advantages of the low TRIM23 expression on overall survival were much more statistically significant. The univariate analysis indicated that TRIM23 expression correlated with overall survival. The multivariate analysis showed that independent factors of prognosis in GC were lymph node metastasis, vascular invasion, and depth of invasion. In summary, TRIM23 may be associated with progression of GC, and may be considered a therapeutic target for GC patients.

TRIM24 promotes hepatocellular carcinoma progression via AMPK signaling

Hepatocellular carcinoma (HCC) is one of the most common cancers diagnosed worldwide. However, the mechanism underlying HCC pathogenesis remains unknown. In the present study, TRIM24 was found increased in human HCC clinical samples and positively correlated with HCC tumor grade. Furthermore, TRIM24 knockdown inhibits proliferation and migration in a human HCC cell line in vitro while also inhibiting tumor growth in vivo. Mechanistically, TRIM24 appears to promote liver tumor development via AMPK signaling as AMPK knockdown alleviated the in vitro and in vivo effects of TRIM24 knockdown in a human HCC cell line. Taken together, these data enhance our understanding of HCC development in addition to highlighting TRIM24-regulated AMPK signaling as a potential therapeutic target for HCC treatment.

Cross-talk between chromatin acetylation and SUMOylation of tripartite motif-containing protein 24 (TRIM24) impacts cell adhesion

Proteins with domains that recognize and bind post-translational modifications (PTMs) of histones are collectively termed epigenetic readers. Numerous interactions between specific reader protein domains and histone PTMs and their regulatory outcomes have been reported, but little is known about how reader proteins may in turn be modulated by these interactions. Tripartite motif-containing protein 24 (TRIM24) is a histone reader aberrantly expressed in multiple cancers. Here, our investigation revealed functional cross-talk between histone acetylation and TRIM24 SUMOylation. Binding of TRIM24 to chromatin via its tandem PHD-bromodomain, which recognizes unmethylated lysine 4 and acetylated lysine 23 of histone H3 (H3K4me0/K23ac), led to TRIM24 SUMOylation at lysine residues 723 and 741. Inactivation of the bromodomain, either by mutation or with a small-molecule inhibitor, IACS-9571, abolished TRIM24 SUMOylation. Conversely, inhibition of histone deacetylation markedly increased TRIM24's interaction with chromatin and its SUMOylation. Of note, gene expression profiling of MCF7 cells expressing WT versus SUMO-deficient TRIM24 identified cell adhesion as the major pathway regulated by the cross-talk between chromatin acetylation and TRIM24 SUMOylation. In conclusion, our findings establish a new link between histone H3 acetylation and SUMOylation of the reader protein TRIM24, a functional connection that may bear on TRIM24's oncogenic function and may inform future studies of PTM cross-talk between histones and epigenetic regulators.

Functional TRIM24 degrader via conjugation of ineffectual bromodomain and VHL ligands

The addressable pocket of a protein is often not functionally relevant in disease. This is true for the multidomain, bromodomain-containing transcriptional regulator TRIM24. TRIM24 has been posited as a dependency in numerous cancers, yet potent and selective ligands for the TRIM24 bromodomain do not exert effective anti-proliferative responses. We therefore repositioned these probes as targeting features for heterobifunctional protein degraders. Recruitment of the VHL E3 ubiquitin ligase by dTRIM24 elicits potent and selective degradation of TRIM24. Using dTRIM24 to probe TRIM24 function, we characterize the dynamic genome-wide consequences of TRIM24 loss on chromatin localization and gene control. Further, we identify TRIM24 as a novel dependency in acute leukemia. Pairwise study of TRIM24 degradation versus bromodomain inhibition reveals enhanced anti-proliferative response from degradation. We offer dTRIM24 as a chemical probe of an emerging cancer dependency, and establish a path forward for numerous selective yet ineffectual ligands for proteins of therapeutic interest.

TRIM24 is an oncogenic transcriptional co-activator of STAT3 in glioblastoma

Aberrant amplification and mutations of epidermal growth factor receptor (EGFR) are the most common oncogenic events in glioblastoma (GBM), but the mechanisms by which they promote aggressive pathogenesis are not well understood. Here, we determine that non-canonical histone signature acetylated H3 lysine 23 (H3K23ac)-binding protein tripartite motif-containing 24 (TRIM24) is upregulated in clinical GBM specimens and required for EGFR-driven tumorigenesis. In multiple glioma cell lines and patient-derived glioma stem cells (GSCs), EGFR signaling promotes H3K23 acetylation and association with TRIM24. Consequently, TRIM24 functions as a transcriptional co-activator and recruits STAT3, leading to stabilized STAT3-chromatin interactions and subsequent activation of STAT3 downstream signaling, thereby enhancing EGFR-driven tumorigenesis. Our findings uncover a pathway in which TRIM24 functions as a signal relay for oncogenic EGFR signaling and suggest TRIM24 as a potential therapeutic target for GBM that are associated with EGFR activation.

EGF receptor (EGFR) amplification and mutation are major drivers in glioma tumorigenesis but this mechanism is not well understood. Here, the authors show EGFR-upregulated H3K23ac binds TRIM24 which recruits STAT3, leading to activation of STAT3 signaling, enhancing EGFR-driven tumorigenesis.

The polar warhead of a TRIM24 bromodomain inhibitor rearranges a water-mediated interaction network

Tripartite motif-containing protein 24 (TRIM24) is closely correlated with multiple cancers, and a recent study demonstrated that the bromodomain of TRIM24 is essential for the proliferation of lethal castration-resistant prostate cancer. Here, we identify three new inhibitors of the TRIM24 bromodomain using NMR fragment-based screening. The crystal structures of two new inhibitors in complex with the TRIM24 bromodomain reveal that the water-bridged interaction network is conserved in the same fashion as those for known benzoimidazolone inhibitors. Interestingly, the polar substitution on the warhead of one new inhibitor pulls the whole ligand approximately 2 Å into the inner side pocket of the TRIM24 bromodomain, and thus exhibits a binding mode significantly different from other known bromodomain ligands. This mode provides a useful handle for further hit-to-lead evolution toward novel inhibitors of the TRIM24 bromodomain.

DATABASE

Structural data are available in the PDB under the accession numbers 5H1T, 5H1U, and 5H1V.

Overexpression of TRIM24 is correlated with the progression of human cervical cancer

TRIM24, originally known as intermediary factor 1-alpha, is involved in the development of several cancers. This study aimed to evaluate the expression level and prognostic value of TRIM24 in cervical cancer. In the present study, we showed that the expression of TRIM24 was markedly upregulated in cervical cancer cell lines and cancerous specimens at both transcriptional and translational levels. TRIM24 expression was analyzed in 147 archived cervical cancer specimens using immunohistochemistry, and the correlation between TRIM24 expression and clinicopathological parameters was evaluated. Statistical analysis suggested that TRIM24 expression was significantly correlated with clinical stage and (P=0.007) and lymphatic metastasis (P=0.001). Patients with higher TRIM24 expression had shorter overall (P=0.005) and recurrence-free (P=0.011) survival time. Moreover, we found that silencing TRIM24 by short hairpin RNAi caused an inhibition of cell migration and invasion. Further study indicated that TRIM24 induced cervical cancer cell migration and invasion was through the NF-κB and AKT signaling pathways. In conclusion, TRIM24 is overexpressed in cervical cancer and regulates malignant cell metastasis, which makes TRIM24 a candidate therapeutic target for cervical cancer.

Elevated UHRF1 expression contributes to poor prognosis by promoting cell proliferation and metastasis in hepatocellular carcinoma

Ubiquitin-like with plant homeodomain and ring finger domains, 1 (UHRF1) is overexpressed in a variety of tumor tissues and is negatively correlated with prognosis of patients with cancers, yet so far, a comprehensive study of UHRF1 in hepatocellular carcinoma (HCC) has not been conducted. The present study was designed to explore the expression of UHRF1, associated clinical implications, and its possible functions in HCC. Reverse transcription-polymerase chain reaction and immunohistochemical staining were used to detect UHRF1 expression in HCC specimens including cancerous and noncancerous tissues. Associations of UHRF1 expression with demographic and clinicopathologic features in HCC were analyzed, and the effects of RNA interference of UHRF1 on cell proliferation, cell cycle, apoptosis, and migration were investigated in vitro and in vivo. UHRF1 mRNA and protein expression were both upregulated and negatively correlated with prognosis in HCC patients. Furthermore, inhibition of proliferation, migration, invasion, and epithelial-mesenchymal transition progression were observed in vitro and in vivo after UHRF1 knockdown, moreover, G2/M arrest was detected in HCC cells. In conclusion, elevated UHRF1 expression contributes to poor prognosis by promoting cell proliferation and metastasis in HCC.

Regulation of TRIM24 by miR-511 modulates cell proliferation in gastric cancer

Background

Increasing evidence highlights the important roles of tripartite motif containing 24 (TRIM24) in tumor initiation and malignant progression in many tumors, including gastric cancer (GC). Although TRIM24 expression is remarkably upregulated during GC carcinogenesis, the molecular mechanisms underlying TRIM24 dysregulation remain unexplored.

Methods

In this study, miRNA target prediction tools were applied to explore miRNAs that potentially target TRIM24. Western blot and quantitative reverse-transcriptase PCR (qRT-PCR) were performed to detected TRIM24 and miR-511 expression in GC tissues and cell lines. Dual-luciferase reporter assay was utilized to validate if TRIM24 is a direct target gene of miR-511. CCK-8 assay, cell colony formation assay, EdU incorporation assay and cell cycle analysis were performed to determine whether miR-511-mediated regulation of TRIM24 could affect GC progression.

Results

In our study, miR-511 was found to be downregulated in GC and an inverse correlation was observed between TRIM24 and miR-511 expression in primary GC tissues and cell lines. Dual-luciferase reporter assay further verified TRIM24 is a direct target of miR-511. Functional assays showed miR-511 overexpression inhibited cell growth, colony formation ability and cell cycle progression. Conversely, inhibition of endogenous miR-511 promoted these phenotypes in GC cells. Moreover, reintroduction of TRIM24 rescued miR-511-induced inhibitory effects on GC cells. Furthermore, miR-511 elicits tumor-suppressive effects through inactivating PI3K/AKT and Wnt/β-catenin pathways by suppressing TRIM24.

Conclusions

Our results provide the new evidence supporting the tumor-suppressive role of miR-511 in GC by suppressing TRIM24, suggesting that this novel miR-511/TRIM24 axis is critical in the control of gastric cancer tumorigenesis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0489-1) contains supplementary material, which is available to authorized users.

TRIM24 promotes the aggression of gastric cancer via the Wnt/β-catenin signaling pathway

Tripartite motif-containing 24 (TRIM24) is important in tumor development and progression. However, the role of TRIM24 in gastric cancer (GC) and the mechanisms underlying the dysregulated expression of TRIM24 remain to be fully elucidated. In the present study, it was found that TRIM24 was frequently overexpressed in GC cell lines and tissues compared with normal controls, as determined by western blotting and immunohistochemical staining. The high nuclear expression of TRIM24 was correlated with the depth of invasion (P=0.007), tumor-node-metastasis stage (P=0.005), and lymph node metastasis (P=0.027), and shorter overall survival rates (P=0.010) in patients with GC. Small interfering RNA-mediated knockdown of TRIM24 inhibited cell proliferation, colony formation, migration, invasion and the nuclear accumulation of β-catenin, and it delayed cell cycle progression and induced apoptosis. In addition, the expression of TRIM24 was positively correlated with that of β-catenin in GC tissues. TRIM24 knockdown decreased the expression of Wnt/β-catenin target genes, whereas the activation of Wnt/β-catenin signaling by lithium chloride reversed the effects of TRIM24 knockdown. Taken together, these data suggested that TRIM24 was a prognostic or potential therapeutic target for patients with GC and was important in the activation of the Wnt/β-catenin pathway during the progression of GC.

NVM-1 predicts prognosis and contributes to growth and metastasis in hepatocellular carcinoma

Novel metastasis-promoting gene 1 (NVM-1) has a significantly elevated protein level in a variety of tumor tissues and is involved in metastasis. However, its functions in hepatocellular carcinoma (HCC) are not clear. The current study aimed to investigate the functions of NVM-1 in cell proliferation, apoptosis, and epithelial-mesenchymal transition in HCC. NVM-1 protein expression in HCC was assessed by immunohistochemical staining. In vitro, cell proliferation, apoptosis, and aggressiveness were determined by CCK-8, fluorescence-assisted cell sorting, TdT-UTP nick-end labeling, and transwell assays, respectively. For in vivo studies, NVM-1 knockdown HCC cells were transplanted into BALB/c nude mice. NVM-1 was frequently upregulated in HCC tissues and positive NVM-1 expression was linked with poor prognosis. NVM-1 depletion significantly inhibited cell proliferation, migration, and invasion abilities in vitro and in vivo. Apoptosis was induced after NVM-1 knockdown. In conclusion, positive NVM-1 expression confers poor prognosis to HCC patients and the NVM-1 protein level correlates with HCC cell proliferation, apoptosis, and EMT.

Clinical significance of SLP-2 in hepatocellular carcinoma tissues and its regulation in cancer cell proliferation, migration, and EMT

Stomatin-like protein 2 (SLP-2) gene was significantly upregulated in a variety of tumor tissues and found to be involved in proliferation and metastasis. However, its functional role in hepatocellular carcinoma (HCC) remains unknown. Our study was to investigate the function of SLP-2 in cell proliferation, migration, invasion, cell apoptosis, and the process of epithelial-mesenchymal transition (EMT) in HCC. SLP-2 mRNA and protein expression in HCC were assessed by qRT-PCR and immunohistochemical staining. In vitro, we determined cell proliferation, migration, invasion, and cell apoptosis by CCK-8, transwell, and flow cytometry assays, respectively. SLP-2 was found to be upregulated at both mRNA and protein levels in HCC tissues, and its aberrant overexpression was linked with poor prognosis in patients with HCC. SLP-2 downregulation by siRNAs significantly suppressed cell proliferation, migration, invasion, anti-apoptosis abilities, and inhibited EMT process in vitro. In conclusion, the present study demonstrated the overexpression of SLP-2 in HCC tissues for the first time. As an effective regulator involved in cell proliferation, migration, invasion, cell apoptosis, and EMT, SLP-2 could be a novel therapeutic target for patients with HCC who express high levels of SLP-2.

Expanding the Circuitry of Pluripotency by Selective Isolation of Chromatin-Associated Proteins

Maintenance of pluripotency is regulated by a network of transcription factors coordinated by Oct4, Sox2, and Nanog (OSN), yet a systematic investigation of the composition and dynamics of the OSN protein network specifically on chromatin is still missing. Here we have developed a method combining ChIP with selective isolation of chromatin-associated proteins (SICAP) followed by mass spectrometry to identify chromatin-bound partners of a protein of interest. ChIP-SICAP in mouse embryonic stem cells (ESCs) identified over 400 proteins associating with OSN, including several whose interaction depends on the pluripotent state. Trim24, a previously unrecognized protein in the network, converges with OSN on multiple enhancers and suppresses the expression of developmental genes while activating cell cycle genes. Consistently, Trim24 significantly improved efficiency of cellular reprogramming, demonstrating its direct functionality in establishing pluripotency. Collectively, ChIP-SICAP provides a powerful tool to decode chromatin protein composition, further enhanced by its integrative capacity to perform ChIP-seq.

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ChIP-SICAP isolates and identifies proteins that colocalize on chromatin

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Chromatin composition around Oct4, Sox2, and Nanog depends on the pluripotent state

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Trim24 is part of the pluripotency network and promotes reprogramming

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ChIP-SICAP allows recovery of DNA for sequencing with ChIP-seq quality

Histone H3 lysine 23 acetylation is associated with oncogene TRIM24 expression and a poor prognosis in breast cancer

Acetylated H3 lysine 23 (H3K23ac) is a specific histone post-translational modification recognized by oncoprotein TRIM24. However, it is not clear whether H3K23ac levels are correlated with TRIM24 expression and what role H3K23ac may have in cancer. In this study, we collected breast carcinoma samples from 121 patients and conducted immunohistochemistry to determine the levels of TRIM24 and H3K23ac in breast cancer. Our results demonstrated that TRIM24 expression is positively correlated with H3K23ac levels, and high levels of both TRIM24 and H3K23ac predict shorter overall survival of breast cancer patients. We also showed that both TRIM24 and H3K23ac are higher in HER2-positive patients, and their levels were positively correlated with HER2 levels in breast cancer. Moreover, TRIM24 expression is associated with estrogen receptor (ER) and progesterone receptor (PR) statuses in both our cohort and The Cancer Genome Atlas (TCGA) breast carcinoma. In summary, our results revealed an important role of TRIM24 and H3K23ac in breast cancer and provided further evidence that TRIM24 small-molecule inhibitors may benefit ER- and PR-negative or HER2-positive breast cancer patients.

Chemical probes and inhibitors of bromodomains outside the BET family

Significant progress has been made in discovering inhibitors and chemical probes of bromodomains, epigenetic readers of lysine acetylation.

In the last five years, the development of inhibitors of bromodomains has emerged as an area of intensive worldwide research. Emerging evidence has implicated a number of non-BET bromodomains in the onset and progression of diseases such as cancer, HIV infection and inflammation. The development and use of small molecule chemical probes has been fundamental to pre-clinical evaluation of bromodomains as targets. Recent efforts are described highlighting the development of potent, selective and cell active non-BET bromodomain inhibitors and their therapeutic potential. Over half of typical bromodomains now have reported ligands, but those with atypical binding site residues remain resistant to chemical probe discovery efforts.

Regulation of gene expression in human cancers by TRIM24

Tripartite Motif-containing protein 24 (TRIM24) functions as an E3 ligase targeting p53 for ubiquitination, a histone 'reader' that interacts with a specific signature of histone post-translational modifications and a co-regulator of nuclear receptor-regulated transcription. Although mouse models of Trim24 depletion suggest that TRIM24 may be a liver-specific tumor suppressor, several studies show that human TRIM24 is an oncogene when aberrantly over expressed. This review focuses on the mechanisms of TRIM24 functions in oncogenesis and metabolic reprogramming, which underlie recent interest in therapeutic targeting of aberrant TRIM24 in human cancers.

TRIM-ing Ligand Dependence in Castration-Resistant Prostate Cancer

Prostate cancer is lethal when tumors evolve to activate androgen receptor signaling, which circumvents ligand-deprivation therapy. In this issue of Cancer Cell, Groner et al. show that histone reader and transcription co-regulator TRIM24 occupies a central role in this evolution, nominating inhibitors of TRIM24's bromodomain as a new therapeutic avenue.

TRIM24 Is an Oncogenic Transcriptional Activator in Prostate Cancer

Androgen receptor (AR) signaling is a key driver of prostate cancer (PC). While androgen-deprivation therapy is transiently effective in advanced disease, tumors often progress to a lethal castration-resistant state (CRPC). We show that recurrent PC-driver mutations in speckle-type POZ protein (SPOP) stabilize the TRIM24 protein, which promotes proliferation under low androgen conditions. TRIM24 augments AR signaling, and AR and TRIM24 co-activated genes are significantly upregulated in CRPC. Expression of TRIM24 protein increases from primary PC to CRPC, and both TRIM24 protein levels and the AR/TRIM24 gene signature predict disease recurrence. Analyses in CRPC cells reveal that the TRIM24 bromodomain and the AR-interacting motif are essential to support proliferation. These data provide a rationale for therapeutic TRIM24 targeting in SPOP mutant and CRPC patients.

Development of small molecule inhibitors of BRPF1 and TRIM24 bromodomains

The entry of small molecule inhibitors of the bromodomain and extra C-terminal domain (BET) family of bromodomains into the clinic has demonstrated the therapeutic potential for this class of epigenetic acetyl-lysine reader proteins. Within the past two years, the development of potent inhibitors for the bromodomain and PHD finger containing protein (BRPF) family and the tripartite motif containing protein 24 (TRIM24) have been reported and are the subject of this review. Both proteins contain other domains with diverse functions and can also be part of a complex of proteins which have implications in epigenetic signaling and disease. These new small molecule tools will be useful for unraveling the biological contribution of the bromodomain and enable pharmacological validation of these proteins.

Hepatocellular carcinoma and non-alcoholic steatohepatitis: The state of play

Hepatocellular carcinoma (HCC) is now the fifth cancer of greatest frequency and the second leading cause of cancer related deaths worldwide. Chief amongst the risks of HCC are hepatitis B and C infection, aflatoxin B1 ingestion, alcoholism and obesity. The latter can promote non-alcoholic fatty liver disease (NAFLD), that can lead to the inflammatory form non-alcoholic steatohepatitis (NASH), and can in turn promote HCC. The mechanisms by which NASH promotes HCC are only beginning to be characterized. Here in this review, we give a summary of the recent findings that describe and associate NAFLD and NASH with the subsequent HCC progression. We will focus our discussion on clinical and genomic associations that describe new risks for NAFLD and NASH promoted HCC. In addition, we will consider novel murine models that clarify some of the mechanisms that drive NASH HCC formation.

T-cell-intrinsic Tif1α/Trim24 regulates IL-1R expression on TH2 cells and TH2 cell-mediated airway allergy

There is a paucity of new therapeutic targets to control allergic reactions and forestall the rising trend of allergic diseases. Although a variety of immune cells contribute to allergy, cytokine-secreting αβ(+)CD4(+) T-helper 2 (TH2) cells orchestrate the type-2-driven immune response in a large proportion of atopic asthmatics. To identify previously unidentified putative targets in pathogenic TH2 cells, we performed in silico analyses of recently published transcriptional data from a wide variety of pathogenic TH cells [Okoye IS, et al. (2014) Proc Natl Acad Sci USA 111(30):E3081-E3090] and identified that transcription intermediary factor 1 regulator-alpha (Tif1α)/tripartite motif-containing 24 (Trim24) was predicted to be active in house dust mite (HDM)- and helminth-elicited Il4(gfp+)αβ(+)CD4(+) TH2 cells but not in TH1, TH17, or Treg cells. Testing this prediction, we restricted Trim24 deficiency to T cells by using a mixed bone marrow chimera system and found that T-cell-intrinsic Trim24 is essential for HDM-mediated airway allergy and antihelminth immunity. Mechanistically, HDM-elicited Trim24(-/-) T cells have reduced expression of many TH2 cytokines and chemokines and were predicted to have compromised IL-1-regulated signaling. Following this prediction, we found that Trim24(-/-) T cells have reduced IL-1 receptor (IL-1R) expression, are refractory to IL-1β-mediated activation in vitro and in vivo, and fail to respond to IL-1β-exacerbated airway allergy. Collectively, these data identify a previously unappreciated Trim24-dependent requirement for IL-1R expression on TH2 cells and an important nonredundant role for T-cell-intrinsic Trim24 in TH2-mediated allergy and antihelminth immunity.

Hepatocellular carcinoma mouse models: Hepatitis B virus-associated hepatocarcinogenesis and haploinsufficient tumor suppressor genes

The multifactorial and multistage pathogenesis of hepatocellular carcinoma (HCC) has fascinated a wide spectrum of scientists for decades. While a number of major risk factors have been identified, their mechanistic roles in hepatocarcinogenesis still need to be elucidated. Many tumor suppressor genes (TSGs) have been identified as being involved in HCC. These TSGs can be classified into two groups depending on the situation with respect to allelic mutation/loss in the tumors: the recessive TSGs with two required mutated alleles and the haploinsufficient TSGs with one required mutated allele. Hepatitis B virus (HBV) is one of the most important risk factors associated with HCC. Although mice cannot be infected with HBV due to the narrow host range of HBV and the lack of a proper receptor, one advantage of mouse models for HBV/HCC research is the numerous and powerful genetic tools that help investigate the phenotypic effects of viral proteins and allow the dissection of the dose-dependent action of TSGs. Here, we mainly focus on the application of mouse models in relation to HBV-associated HCC and on TSGs that act either in a recessive or in a haploinsufficient manner. Discoveries obtained using mouse models will have a great impact on HCC translational medicine.

Bromodomains: Structure, function and pharmacology of inhibition

Bromodomains are epigenetic readers of histone acetylation involved in chromatin remodeling and transcriptional regulation. The human proteome comprises 46 bromodomain-containing proteins with a total of 61 bromodomains, which, despite highly conserved structural features, recognize a wide array of natural peptide ligands. Over the past five years, bromodomains have attracted great interest as promising new epigenetic targets for diverse human diseases, including inflammation, cancer, and cardiovascular disease. The demonstration in 2010 that two small molecule compounds, JQ1 and I-BET762, potently inhibit proteins of the bromodomain and extra-terminal (BET) family with translational potential for cancer and inflammatory disease sparked intense efforts in academia and pharmaceutical industry to develop novel bromodomain antagonists for therapeutic applications. Several BET inhibitors are already in clinical trials for hematological malignancies, solid tumors and cardiovascular disease. Currently, the field faces the challenge of single-target selectivity, especially within the BET family, and of overcoming problems related to the development of drug resistance. At the same time, new trends in bromodomain inhibitor research are emerging, including an increased interest in non-BET bromodomains and a focus on drug synergy with established antitumor agents to improve chemotherapeutic efficacy. This review presents an updated view of the structure and function of bromodomains, traces the development of bromodomain inhibitors and their potential therapeutic applications, and surveys the current challenges and future directions of this vibrant new field in drug discovery.

Disrupting Acetyl-Lysine Recognition: Progress in the Development of Bromodomain Inhibitors

Bromodomains, small protein modules that recognize acetylated lysine on histones, play a significant role in the epigenome, where they function as "readers" that ultimately determine the functional outcome of the post-translational modification. Because the initial discovery of selective BET inhibitors have helped define the role of that protein family in oncology and inflammation, BET bromodomains have continued to garner the most attention of any other bromodomain. More recently, non-BET bromodomain inhibitors that are potent and selective have been disclosed for ATAD2, CBP, BRD7/9, BRPF, BRPF/TRIM24, CECR2, SMARCA4, and BAZ2A/B. Such novel inhibitors can be used to probe the physiological function of these non-BET bromodomains and further understanding of their role in certain disease states. Here, we provide an update to the progress in identifying selective bromodomain inhibitors and their use as biological tools, as well as our perspective on the field.

Structure-Guided Design of IACS-9571, a Selective High-Affinity Dual TRIM24-BRPF1 Bromodomain Inhibitor

The bromodomain containing proteins TRIM24 (tripartite motif containing protein 24) and BRPF1 (bromodomain and PHD finger containing protein 1) are involved in the epigenetic regulation of gene expression and have been implicated in human cancer. Overexpression of TRIM24 correlates with poor patient prognosis, and BRPF1 is a scaffolding protein required for the assembly of histone acetyltransferase complexes, where the gene of MOZ (monocytic leukemia zinc finger protein) was first identified as a recurrent fusion partner in leukemia patients (8p11 chromosomal rearrangements). Here, we present the structure guided development of a series of N,N-dimethylbenzimidazolone bromodomain inhibitors through the iterative use of X-ray cocrystal structures. A unique binding mode enabled the design of a potent and selective inhibitor 8i (IACS-9571) with low nanomolar affinities for TRIM24 and BRPF1 (ITC Kd = 31 nM and ITC Kd = 14 nM, respectively). With its excellent cellular potency (EC50 = 50 nM) and favorable pharmacokinetic properties (F = 29%), 8i is a high-quality chemical probe for the evaluation of TRIM24 and/or BRPF1 bromodomain function in vitro and in vivo.

Discovery of a Chemical Tool Inhibitor Targeting the Bromodomains of TRIM24 and BRPF

TRIM24 is a transcriptional regulator as well as an E3 ubiquitin ligase. It is overexpressed in diverse tumors, and high expression levels have been linked to poor prognosis in breast cancer patients. TRIM24 contains a PHD/bromodomain offering the opportunity to develop protein interaction inhibitors that target this protein interaction module. Here we identified potent acetyl-lysine mimetic benzimidazolones TRIM24 bromodomain inhibitors. The best compound of this series is a selective BRPF1B/TRIM24 dual inhibitor that bound with a K_D of 137 and 222 nM, respectively, but exerted good selectivity over other bromodomains. Cellular activity of the inhibitor was demonstrated using FRAP assays as well as cell viability data.

Clinical significance and biological roles of TRIM24 in human bladder carcinoma

Tripartite motif-containing 24 (TRIM24), also known as transcription intermediary factor 1-alpha (TIF1α), is a chromatin-associated protein which as been has been implicated in carcinogenesis. However, its expression profile and biological roles in human bladder carcinoma has not been investigated. In this study, we examined its expression in 95 bladder cancer specimens. We found that TRIM24 expression was upregulated in 39 of 95 (41.1 %) specimens compared with normal control. TRIM24 overexpression was associated with local invasion and advanced grade of bladder cancer. In addition, we transfected TRIM24 plasmid into BIU-87 cell line and TRIM24 siRNA into 5637 cell line. Colony formation, CCK-8, and transwell assay were used to assess its biological roles in bladder cancer cells. The result showed that TRIM24 could facilitate cancer cell growth and invading ability. Western blot analysis demonstrated that TRIM24 upregulated cyclin D1, cyclin E, p-IκBα, and p-AKT expression, suggesting TRIM24 activates NF-κB and AKT pathways. In addition, NF-κB inhibitor reversed the effect of TRIM24 on cyclin D1. In conclusion, TRIM24 is overexpressed in human bladder cancer and facilitates bladder cancer growth and invasion, possibly through NF-κB and AKT signaling pathways.

TRIM24 suppresses development of spontaneous hepatic lipid accumulation and hepatocellular carcinoma in mice

BACKGROUND & AIMS

Aberrantly high expression of TRIM24 occurs in human cancers, including hepatocellular carcinoma. In contrast, TRIM24 in the mouse is reportedly a liver-specific tumour suppressor. To address this dichotomy and to uncover direct regulatory functions of TRIM24 in vivo, we developed a new mouse model that lacks expression of all Trim24 isoforms, as the previous model expressed normal levels of Trim24 lacking only exon 4.

METHODS

To produce germline-deleted Trim24(dlE1) mice, deletion of the promoter and exon 1 of Trim24 was induced in Trim24(LoxP) mice by crossing with a zona pellucida 3-Cre line for global deletion. Liver-specific deletion (Trim24(hep)) was achieved by crossing with an albumin-Cre line. Phenotypic analyses were complemented by protein, gene-specific and global RNA expression analyses and quantitative chromatin immunoprecipitation.

RESULTS

Global loss of Trim24 disrupted hepatic homeostasis in 100% of mice with highly significant, decreased expression of oxidation/reduction, steroid, fatty acid, and lipid metabolism genes, as well as increased expression of genes involved in unfolded protein response, endoplasmic reticulum stress and cell cycle pathways. Trim24(dlE1/dlE1) mice have markedly depleted visceral fat and, like Trim24(hep/hep) mice, spontaneously develop hepatic lipid-filled lesions, steatosis, hepatic injury, fibrosis and hepatocellular carcinoma.

CONCLUSIONS

TRIM24, an epigenetic co-regulator of transcription, directly and indirectly represses hepatic lipid accumulation, inflammation, fibrosis and damage in the murine liver. Complete loss of Trim24 offers a model of human non-alcoholic fatty liver disease, steatosis, fibrosis and development of hepatocellular carcinoma in the absence of high-fat diet or obesity.