The transcriptional corepressor CtBP: a foe of multiple tumor suppressors

Identification of potential biomarkers for 2022 Mpox virus infection: a transcriptomic network analysis and machine learning approach

Monkeypox virus (MPXV), a zoonotic pathogen, re-emerged in 2022 with the Clade IIb variant, raising global health concerns due to its unprecedented spread in non-endemic regions. Recent studies have shown that Clade IIb (2022 MPXV) is marked by unique genomic mutations and epidemiological behaviors, suggesting variations in host-virus interactions. This study aimed to identify the differentially expressed genes (DEGs) induced by the 2022 MPXV infection through comprehensive bioinformatics analyses of microarray and RNA-Seq datasets from post-infected cell types with different MPXV clades. Subsequently, gene expression network analyses pinpoint the key DEGs, followed by their candidate drug assessment using the Drug SIGnatures DataBase (DSigDB) and validation by multiple machine learning algorithms. Comparative differential gene expression (DGE) analysis revealed 798 DEGs exclusive to the 2022 MPXV invasion in the skin cell types (keratinocytes). Intriguingly, 13 key DEGs were identified across hubs and clusters, highlighting their aberrant expressions in cell cycle regulation, immune responses, and cancer pathways. Biomarker screening via Random Forest (RF) model (selected with PyCaret from multiple models) and validation through t-distributed stochastic neighbor embedding (t-SNE) algorithm, principal component analysis (PCA), and ROC curve analysis employing Logistic Regression and Random Forest, identified 6 key DEGs (TXNRD1, CCNB1, BUB1, CDC20, BUB1B, and CCNA2) as promising biomarkers (AUC > 0.7) for clade IIb infection. This study anticipates that further investigation and clinical trials will catalyze novel detection and therapeutic options to combat 2022 MPXV infection in humans.

Spatial Profiling Reveals Equivalence-Derived Molecular Signatures of Brain Mimicry and Adaptation in Breast Cancer Brain Metastases

Brain metastases (BrMets), common for advanced-stage breast cancer patients, are associated with poor median survival and accompanied by severe neurologic decline. Halting the progression of breast cancer brain metastases (BCBMs) may require modulation of the tumor microenvironment (TME), yet little is known about the impact of the primary breast TME on brain tropism, or how, once there, metastatic breast cancer cells coexist with brain-resident cells (e.g., neurons and glia). Traditionally, studies in this space have focused on differential expression analysis, overlooking potential insights gained from investigating genes with equivalent expression between groups. This is particularly crucial in distant metastasis, where tumor cells may co-opt the transcriptional programs of the host organ (e.g., brain) to facilitate successful seeding and outgrowth. Prior to our work, no computational framework existed to determine biologically-relevant equivalent gene expression. To resolve molecular mechanisms of BCBM enabled by metastatic cancer cells and/or resident brain cells, we leveraged Nanostring GeoMx to perform spatially-resolved transcriptomic profiling on 235 patient-derived tissue cores from BCBM (including adjacent normal brain), primary invasive breast cancers, and normal (non-cancer) brain; analyzing 18,677 RNAs in 450 areas of interest (AOIs). We introduce the "Equivalent Expression Index" a highly specific and accurate algorithm that identifies statistically significant "Equivalently-Expressed Genes". This method facilitated the identification of molecular remodeling and mimicry genes within tissue-specific TMEs. By integrating differential expression analysis with the Equivalent Expression Index, we discovered multiple novel gene signatures associated with BCBM and primary tumor brain-metastatic potential. We demonstrate that the Equivalent Expression Index is a powerful tool to uncover shared gene expression programs representing the adaptation of metastatic cells and brain-resident cells to the BCBM microenvironment.

Interpretable identification of cancer genes across biological networks via transformer-powered graph representation learning

Graph representation learning has been leveraged to identify cancer genes from biological networks. However, its applicability is limited by insufficient interpretability and generalizability under integrative network analysis. Here we report the development of an interpretable and generalizable transformer-based model that accurately predicts cancer genes by leveraging graph representation learning and the integration of multi-omics data with the topologies of homogeneous and heterogeneous networks of biological interactions. The model allows for the interpretation of the respective importance of multi-omic and higher-order structural features, achieved state-of-the-art performance in the prediction of cancer genes across biological networks (including networks of interactions between miRNA and proteins, transcription factors and proteins, and transcription factors and miRNA) in pan-cancer and cancer-specific scenarios, and predicted 57 cancer-gene candidates (including three genes that had not been identified by other models) among 4,729 unlabelled genes across 8 pan-cancer datasets. The model's interpretability and generalization may facilitate the understanding of gene-related regulatory mechanisms and the discovery of new cancer genes.

CtBP1 is essential for epigenetic silencing of μ-opioid receptor genes in the dorsal root ganglion in spinal nerve ligation-induced neuropathic pain

Neuropathic pain poses a significant public health challenge, greatly impacting patients' quality of life. Emerging evidence underscores the involvement of epigenetics in dorsal root ganglion (DRG) neurons relevant to pain modulation. C-terminal binding protein 1 (CtBP1) has emerged as a crucial epigenetic transcriptional coregulator. However, the underlying molecular mechanisms of CtBP1-mediated epigenetic regulation in DRG neurons in neuropathic pain remain poorly elucidated. Here, we employed a Sprague‒Dawley rat model of spinal nerve ligation (SNL) to establish a neuropathic pain model. CtBP1 expression in the ipsilateral DRG gradually increased over a three-week period post-SNL. Immunohistochemistry revealed a significant elevation in CtBP1 levels specifically in NeuN-positive neuronal cells in the ipsilateral DRG following SNL. Further characterization demonstrated CtBP1 expression across various subtypes of DRG neurons in SNL rats. Silencing CtBP1 expression with siRNA reversed tactile allodynia in SNL rats and restored both CtBP1 and μ-opioid receptor expression in the DRG in SNL rats. Moreover, Foxp1 was identified to recruit CtBP1 for mediating μ-opioid receptor gene silencing in the DRG in SNL rats. Subsequent investigation unveiled that Foxp1 recruits CtBP1 and associates with HDAC2 to regulate H3K9Ac binding to μ-opioid receptor chromatin regions in the DRG in SNL rats, implicating epigenetic mechanisms in neuropathic pain. Targeting the Foxp1/CtBP1/HDAC2/μ-opioid receptor signaling pathway in the DRG holds promise as a potential therapeutic strategy for managing neuropathic pain.

Mechanism of APC truncation involved in colorectal cancer tumorigenesis (Review)

Adenomatous polyposis coli (APC) is widely recognized as a heavily mutated gene that suppresses tumor growth in colorectal cancer (CRC). Its mutation is considered to be the primary and early event that occurs in the development of CRC. In addition, APC has a crucial role in inhibiting the canonical Wnt signaling pathway. APC mutations in CRC result in the production of shortened gene products. This impairment of β-catenin destruction complexes causes an accumulation of active β-catenin in the cytoplasm and nucleus. In these compartments, β-catenin can bind with DNA-binding proteins of the transcription factor/lymphoid enhancer-binding factor family, thereby activating the Wnt signaling pathway. Consequently, the balance of numerous cellular processes is disrupted, ultimately driving the formation of tumors. There is a growing body of evidence indicating the prevalent occurrence of APC truncation in the majority of CRC cases. Furthermore, it has been observed that these truncated proteins have a crucial role in the activation of the Wnt signaling pathway and the subsequent loss of tumor inhibitory function. This review aimed to provide an overview of the recent advancements in understanding the mechanism behind APC truncation and its association with the onset and progression of CRC.

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Nuclear Bcl-xL is found to promote cancer metastasis independently of its mitochondria-based anti-apoptotic activity. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates histone H3 trimethyl Lys4 (H3K4me3) modification have yet to be understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds to Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced invasion and metastasis in mouse models. Furthermore, knockout of CtBP2 not only reduces the nuclear portion of Bcl-xL but also suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of the MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGFβ mRNA upregulation, as well as invasion. Moreover, the cleavage under targets and release using nuclease (CUT&RUN) assay coupled with next-generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor regions of genes encoding TGFβ and its signaling pathway members in cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1 and this study offers new therapeutic strategies to treat Bcl-xL-overexpressing cancer.

Master corepressor inactivation through multivalent SLiM-induced polymerization mediated by the oncogene suppressor RAI2

While the elucidation of regulatory mechanisms of folded proteins is facilitated due to their amenability to high-resolution structural characterization, investigation of these mechanisms in disordered proteins is more challenging due to their structural heterogeneity, which can be captured by a variety of biophysical approaches. Here, we used the transcriptional master corepressor CtBP, which binds the putative metastasis suppressor RAI2 through repetitive SLiMs, as a model system. Using cryo-electron microscopy embedded in an integrative structural biology approach, we show that RAI2 unexpectedly induces CtBP polymerization through filaments of stacked tetrameric CtBP layers. These filaments lead to RAI2-mediated CtBP nuclear foci and relieve its corepressor function in RAI2-expressing cancer cells. The impact of RAI2-mediated CtBP loss-of-function is illustrated by the analysis of a diverse cohort of prostate cancer patients, which reveals a substantial decrease in RAI2 in advanced treatment-resistant cancer subtypes. As RAI2-like SLiM motifs are found in a wide range of organisms, including pathogenic viruses, our findings serve as a paradigm for diverse functional effects through multivalent interaction-mediated polymerization by disordered proteins in healthy and diseased conditions.

Unveiling the metabolic landscape of pulmonary hypertension: insights from metabolomics

Pulmonary hypertension (PH) is regarded as cardiovascular disease with an extremely poor prognosis, primarily due to irreversible vascular remodeling. Despite decades of research progress, the absence of definitive curative therapies remains a critical challenge, leading to high mortality rates. Recent studies have shown that serious metabolic disorders generally exist in PH animal models and patients of PH, which may be the cause or results of the disease. It is imperative for future research to identify critical biomarkers of metabolic dysfunction in PH pathophysiology and to uncover metabolic targets that could enhance diagnostic and therapeutic strategies. Metabolomics offers a powerful tool for the comprehensive qualitative and quantitative analysis of metabolites within specific organisms or cells. On the basis of the findings of the metabolomics research on PH, this review summarizes the latest research progress on metabolic pathways involved in processes such as amino acid metabolism, carbohydrate metabolism, lipid metabolism, and nucleotide metabolism in the context of PH.

Fibroblasts in Pulmonary Hypertension: Roles and Molecular Mechanisms

Fibroblasts, among the most prevalent and widely distributed cell types in the human body, play a crucial role in defining tissue structure. They do this by depositing and remodeling extracellular matrixes and organizing functional tissue networks, which are essential for tissue homeostasis and various human diseases. Pulmonary hypertension (PH) is a devastating syndrome with high mortality, characterized by remodeling of the pulmonary vasculature and significant cellular and structural changes within the intima, media, and adventitia layers. Most research on PH has focused on alterations in the intima (endothelial cells) and media (smooth muscle cells). However, research over the past decade has provided strong evidence of the critical role played by pulmonary artery adventitial fibroblasts in PH. These fibroblasts exhibit the earliest, most dramatic, and most sustained proliferative, apoptosis-resistant, and inflammatory responses to vascular stress. This review examines the aberrant phenotypes of PH fibroblasts and their role in the pathogenesis of PH, discusses potential molecular signaling pathways underlying these activated phenotypes, and highlights areas of research that merit further study to identify promising targets for the prevention and treatment of PH.

Identification and characterization of a new potent inhibitor targeting CtBP1/BARS in melanoma cells

BACKGROUND

The C-terminal-binding protein 1/brefeldin A ADP-ribosylation substrate (CtBP1/BARS) acts both as an oncogenic transcriptional co-repressor and as a fission inducing protein required for membrane trafficking and Golgi complex partitioning during mitosis, hence for mitotic entry. CtBP1/BARS overexpression, in multiple cancers, has pro-tumorigenic functions regulating gene networks associated with "cancer hallmarks" and malignant behavior including: increased cell survival, proliferation, migration/invasion, epithelial-mesenchymal transition (EMT). Structurally, CtBP1/BARS belongs to the hydroxyacid-dehydrogenase family and possesses a NAD(H)-binding Rossmann fold, which, depending on ligands bound, controls the oligomerization of CtBP1/BARS and, in turn, its cellular functions. Here, we proposed to target the CtBP1/BARS Rossmann fold with small molecules as selective inhibitors of mitotic entry and pro-tumoral transcriptional activities.

METHODS

Structured-based screening of drug databases at different development stages was applied to discover novel ligands targeting the Rossmann fold. Among these identified ligands, N-(3,4-dichlorophenyl)-4-{[(4-nitrophenyl)carbamoyl]amino}benzenesulfonamide, called Comp.11, was selected for further analysis. Fluorescence spectroscopy, isothermal calorimetry, computational modelling and site-directed mutagenesis were employed to define the binding of Comp.11 to the Rossmann fold. Effects of Comp.11 on the oligomerization state, protein partners binding and pro-tumoral activities were evaluated by size-exclusion chromatography, pull-down, membrane transport and mitotic entry assays, Flow cytometry, quantitative real-time PCR, motility/invasion, and colony assays in A375MM and B16F10 melanoma cell lines. Effects of Comp.11 on tumor growth in vivo were analyzed in mouse tumor model.

RESULTS

We identify Comp.11 as a new, potent and selective inhibitor of CtBP1/BARS (but not CtBP2). Comp.11 directly binds to the CtBP1/BARS Rossmann fold affecting the oligomerization state of the protein (unlike other known CtBPs inhibitors), which, in turn, hinders interactions with relevant partners, resulting in the inhibition of both CtBP1/BARS cellular functions: i) membrane fission, with block of mitotic entry and cellular secretion; and ii) transcriptional pro-tumoral effects with significantly hampered proliferation, EMT, migration/invasion, and colony-forming capabilities. The combination of these effects impairs melanoma tumor growth in mouse models.  CONCLUSIONS: This study identifies a potent and selective inhibitor of CtBP1/BARS active in cellular and melanoma animal models revealing new opportunities to study the role of CtBP1/BARS in tumor biology and to develop novel melanoma treatments.

Patient-derived castration-resistant prostate cancer model revealed CTBP2 upregulation mediated by OCT1 and androgen receptor

BACKGROUND

Prostate cancer is dependent on androgen receptor (AR) signaling, and androgen deprivation therapy (ADT) has proven effective in targeting prostate cancer. However, castration-resistant prostate cancer (CRPC) eventually emerges. AR signaling inhibitors (ARSI) have been also used, but resistance to these agents develops due to genetic AR alterations and epigenetic dysregulation.

METHODS

In this study, we investigated the role of OCT1, a member of the OCT family, in an AR-positive CRPC patient-derived xenograft established from a patient with resistance to ARSI and chemotherapy. We conducted a genome-wide analysis chromatin immunoprecipitation followed by sequencing and bioinformatic analyses using public database.

RESULTS

Genome-wide analysis of OCT1 target genes in PDX 201.1 A revealed distinct OCT1 binding sites compared to treatment-naïve cells. Bioinformatic analyses revealed that OCT1-regulated genes were associated with cell migration and immune system regulation. In particular, C-terminal Binding Protein 2 (CTBP2), an OCT1/AR target gene, was correlated with poor prognosis and immunosuppressive effects in the tumor microenvironment. Metascape revealed that CTBP2 knockdown affects genes related to the immune response to bacteria. Furthermore, TISIDB analysis suggested the relationship between CTBP2 expression and immune cell infiltration in prostate cancer, suggesting that it may contribute to immune evasion in CRPC.

CONCLUSIONS

Our findings shed light on the genome-wide network of OCT1 and AR in AR-positive CRPC and highlight the potential role of CTBP2 in immune response and tumor progression. Targeting CTBP2 may represent a promising therapeutic approach for aggressive AR-positive CRPC. Further validation will be required to explore novel therapeutic strategies for CRPC management.

iChIP-SILAC analysis identifies epigenetic regulators of CpG methylation of the p16INK4A gene

Allele-specific epigenetic events regulate the expression of specific genes such as tumor suppressor genes. Methods to biochemically identify epigenetic regulators remain limited. Here, we used insertional chromatin immunoprecipitation (iChIP) to address this issue. iChIP combined with quantitative mass spectrometry identified DNA methyltransferase 1 (DNMT1) and epigenetic regulators as proteins that potentially interact with a region of the p16INK4A gene that is CpG-methylated in one allele in HCT116 cells. Some of the identified proteins are involved in the CpG methylation of this region, and of these, DEAD-box helicase 24 (DDX24) contributes to CpG methylation by regulating the protein levels of DNMT1. Thus, iChIP is a useful method to identify proteins which bind to a target locus of interest.

LINC MIR503HG Controls SC-β Cell Differentiation and Insulin Production by Targeting CDH1 and HES1

Stem cell-derived pancreatic progenitors (SC-PPs), as an unlimited source of SC-derived β (SC-β) cells, offers a robust tool for diabetes treatment in stem cell-based transplantation, disease modeling, and drug screening. Whereas, PDX1+/NKX6.1+ PPs enhances the subsequent endocrine lineage specification and gives rise to glucose-responsive SC-β cells in vivo and in vitro. To identify the regulators that promote induction efficiency and cellular function maturation, single-cell RNA-sequencing is performed to decipher the transcriptional landscape during PPs differentiation. The comprehensive evaluation of functionality demonstrated that manipulating LINC MIR503HG using CRISPR in PP cell fate decision can improve insulin synthesis and secretion in mature SC-β cells, without effects on liver lineage specification. Importantly, transplantation of MIR503HG-/- SC-β cells in recipients significantly restored blood glucose homeostasis, accompanied by serum C-peptide release and an increase in body weight. Mechanistically, by releasing CtBP1 occupying the CDH1 and HES1 promoters, the decrease in MIR503HG expression levels provided an excellent extracellular niche and appropriate Notch signaling activation for PPs following differentiation. Furthermore, this exhibited higher crucial transcription factors and mature epithelial markers in CDH1High expressed clusters. Altogether, these findings highlighted MIR503HG as an essential and exclusive PP cell fate specification regulator with promising therapeutic potential for patients with diabetes.

Dachshund and C-terminal Binding Protein bind directly during Drosophila eye development

The transcription factor Dachshund (Dac) and the transcriptional co-regulator C-terminal Binding Protein (CtBP) were identified as the retinal determination factors during Drosophila eye development . A previous study established that Dac and CtBP interact genetically during eye development. Co-immunoprecipitation assays suggested that both molecules interact in the Drosophila larval eye-antennal disc. Our present study shows that Dac and CtBP bind each other directly, as determined by GST pull-down assays. Thus, our results demonstrate the molecular mechanism of Dac and CtBP interaction and suggest the direct binding of these two transcription regulators in the cells of the eye disc promotes the Drosophila eye specification.

Transcriptional corepressor activity of CtBP1 is regulated by ISG15 modification

C-terminal binding protein 1 (CtBP1) is a critical transcriptional corepressor of many tumor suppressor genes and plays diverse roles in the progression of cancers. The transcriptional repression function of CtBP1 is mediated by recruiting histone-modifying enzymes, such as histone deacetylases and histone methyltransferases, to target genes by binding with DNA-interacting factors. Several post-translational modifications of CtBP1 have been identified, including ubiquitination, phosphorylation, and SUMOylation. This paper reports that CtBP1 is conjugated by ISG15. Endogenous CtBP1 was modified by ISG15 after interferon-α treatment in HeLa cells. The ISGylation process of CtBP1 was regulated by deISGylation enzyme USP18 and ISG15 E3 ligase EFP. Interestingly, CtBP1 ISGylation affected the binding affinity between CtBP1 and some components of CtBP1-associated transcriptional complexes. HDAC1 and LSD1 bound more efficiently to ISG15-conjugated CtBP1 than non-conjugated CtBP1. On the other hand, binding between CtBP1 and HDAC4 was unaffected by ISG15 modification. Furthermore, ISG15 modification enhanced the transcriptional repression activity of CtBP1 on several target genes related to EMT and apoptosis. These findings suggest that the ISG15 modification of CtBP1 modulates the function and activity of CtBP1 and that CtBP1 ISGylation may provide a new insight for CtBP1-mediated cancers.

C-Terminal Binding Protein 2 Emerges as a Critical Player Linking Metabolic Imbalance to the Pathogenesis of Obesity

Metabolism is one of the vital functions of cells and living organisms, and the systems to sense and respond to the metabolic alterations play pivotal roles in a plethora of biological processes, including cell proliferative activities, immune cell functions, aging processes, and neuronal functions. Recently, we have reported that a transcriptional cofactor, C-terminal binding protein 2 (CtBP2), serves as a critical metabolite sensor in this context. CtBP2 has a structural pocket called Rossmann fold to accommodate metabolites, and it has been reported to be activated upon binding to NADH/NAD＋. Owing to its preferential binding affinity for NADH compared with NAD＋, increased glycolysis activates CtBP2 by regenerating NADH from NAD＋. Furthermore, we recently reported that fatty acyl-CoAs, metabolites accumulated under the condition of lipid overload, as represented by obesity, can inactivate CtBP2. These observations suggest that CtBP2 monitors not only redox state but also energy substrate preference in the maintenance of metabolic homeostasis. In line with these metabolite-sensing capabilities, CtBP2 is activated in healthy subjects to protect against metabolic disturbances, whereas inactivation of CtBP2 in obesity contributes to the pathogeneses of obesity.This metabolic system orchestrated by CtBP2 can provide a novel framework for understanding how cells maintain their homeostasis through coordination of metabolism, and CtBP2 incapacitation can be a critical point of the obesogenic cascade.

Combined Targeting of NAD Biosynthesis and the NAD-dependent Transcription Factor C-terminal Binding Protein as a Promising Novel Therapy for Pancreatic Cancer

Cancer therapies targeting metabolic derangements unique to cancer cells are emerging as a key strategy to address refractory solid tumors such as pancreatic ductal adenocarcinomas (PDAC) that exhibit resistance to extreme nutrient deprivation in the tumor microenvironment. Nicotinamide adenine dinucleotide (NAD) participates in multiple metabolic pathways and nicotinamide phosphoribosyl transferase (NAMPT) is one of the key intracellular enzymes that facilitate the synthesis of NAD. C-terminal binding proteins 1 and 2 (CtBP) are paralogous NAD-dependent oncogenic transcription factors and dehydrogenases that nucleate an epigenetic complex regulating a cohort of genes responsible for cancer proliferation and metastasis. As adequate intracellular NAD is required for CtBP to oligomerize and execute its oncogenic transcriptional coregulatory activities, we hypothesized that NAD depletion would synergize with CtBP inhibition, improving cell inhibitory efficacy. Indeed, depletion of cellular NAD via the NAMPT inhibitor GMX1778 enhanced growth inhibition induced by either RNAi-mediated CtBP1/2 knockdown or the CtBP dehydrogenase inhibitor 4-chlorophenyl-2-hydroxyimino propanoic acid as much as 10-fold in PDAC cells, while untransformed pancreatic ductal cells were unaffected. The growth inhibitory effects of the NAMPT/CtBP inhibitor combination correlated pharmacodynamically with on-target disruption of CtBP1/2 dimerization, CtBP2 interaction with the CoREST epigenetic regulator, and transcriptional activation of the oncogenic target gene TIAM1. Moreover, this same therapeutic combination strongly attenuated growth of PDAC cell line xenografts in immunodeficient mice, with no observable toxicity. Collectively, our data demonstrate that targeting CtBP in combination with NAD depletion represents a promising therapeutic strategy for PDAC.

SIGNIFICANCE

Effective precision therapies are lacking in PDAC. We demonstrate that simultaneous inhibition of NAD metabolism and the oncoprotein CtBP is potently effective at blocking growth of both PDAC cells in culture and human PDAC-derived tumors in mice and should be explored further as a potential therapy for patients with PDAC.

CRISPR/Cas9-Mediated CtBP1 Gene Editing Enhances Chemosensitivity and Inhibits Metastatic Potential in Esophageal Squamous Cell Carcinoma Cells

Innovative therapeutic strategies for esophageal squamous cell carcinoma (ESCC) are urgently required due to the limited effectiveness of standard chemotherapies. C-Terminal Binding Protein 1 (CtBP1) has been implicated in various cancers, including ESCC. However, the precise expression patterns and functional roles of CtBP1 in ESCC remain inadequately characterized. In this study, we aimed to investigate CtBP1 expression and its role in the resistance of ESCC to paclitaxel, an effective chemotherapeutic agent. Western blotting and immunofluorescence were applied to assess CtBP1 expression in the TE-1 and KYSE-50 cell lines. We observed the marked expression of CtBP1, which was associated with enhanced proliferation, invasion, and metastasis in these cell lines. Further, we successfully generated paclitaxel resistant ESCC cell lines and conducted cell viability assays. We employed the CRISPR/Cas9 genome editing system to disable the CtBP1 gene in ESCC cell lines. Through the analysis of the drug dose-response curve, we assessed the sensitivity of these cell lines in different treatment groups. Remarkably, CtBP1-disabled cell lines displayed not only improved sensitivity but also a remarkable inhibition of proliferation, invasion, and metastasis. This demonstrates that CtBP1 may promote ESCC cell malignancy and confer paclitaxel resistance. In summary, our study opens a promising avenue for targeted therapies, revealing the potential of CtBP1 inhibition to enhance the effectiveness of paclitaxel treatment for the personalized management of ESCC.

CtBP Neuroprotective Role in Toxin-Based Parkinson's Disease Models: From Expression Pattern to Dopaminergic Survival

C-terminal binding proteins (CtBP) are transcriptional co-repressors regulating gene expression. CtBP promote neuronal survival through repression of pro-apoptotic genes, and may represent relevant targets for neurodegenerative disorders, such as Parkinson's disease (PD). Nevertheless, evidence of the role of CtBP1 and CtBP2 in neurodegeneration are scarce. Herein, we showed that CtBP1 and CtBP2 are expressed in neurons, dopaminergic neurons, astrocytes, and microglia in the substantia nigra (SN) and striatum of adult mice. Old mice showed a lower expression of CtBP1 in the SN and higher expression of CtPB2 in the SN and striatum compared with adult mice. In vivo models for PD (paraquat, MPTP, 6-OHDA) showed increased expression of CtBP1 in the SN and striatum while CtBP2 expression was increased in the striatum of paraquat-treated rats only. Moreover, an increased expression of both CtBP was found in a dopaminergic cell line (N27) exposed to 6-OHDA. In the 6-OHDA PD model, we found a dual effect using an unspecific ligand of CtBP, the 4-methylthio 2-oxobutyric acid (MTOB): higher concentrations (e.g. 2500 µM, 1000 µM) inhibited dopaminergic survival, while at 250 μM it counteracted cell death. In vitro, this latter protective role was absent after the siRNA silencing of CtBP1 or CtBP2. Altogether, this is the first report exploring the cellular and regional expression pattern of CtBP in the nigrostriatal pathway and the neuroprotective role in PD toxin-based models. CtBP could counteract dopaminergic cell death in the 6-OHDA PD model and, therefore, CtBP function and therapeutic potential in PD should be further explored.

JAC4 Inhibits EGFR-Driven Lung Adenocarcinoma Growth and Metastasis through CTBP1-Mediated JWA/AMPK/NEDD4L/EGFR Axis

Lung adenocarcinoma (LUAD) is the most common lung cancer, with high mortality. As a tumor-suppressor gene, JWA plays an important role in blocking pan-tumor progression. JAC4, a small molecular-compound agonist, transcriptionally activates JWA expression both in vivo and in vitro. However, the direct target and the anticancer mechanism of JAC4 in LUAD have not been elucidated. Public transcriptome and proteome data sets were used to analyze the relationship between JWA expression and patient survival in LUAD. The anticancer activities of JAC4 were determined through in vitro and in vivo assays. The molecular mechanism of JAC4 was assessed by Western blot, quantitative real-time PCR (qRT-PCR), immunofluorescence (IF), ubiquitination assay, co-immunoprecipitation, and mass spectrometry (MS). Cellular thermal shift and molecule-docking assays were used for confirmation of the interactions between JAC4/CTBP1 and AMPK/NEDD4L. JWA was downregulated in LUAD tissues. Higher expression of JWA was associated with a better prognosis of LUAD. JAC4 inhibited LUAD cell proliferation and migration in both in-vitro and in-vivo models. Mechanistically, JAC4 increased the stability of NEDD4L through AMPK-mediated phosphorylation at Thr367. The WW domain of NEDD4L, an E3 ubiquitin ligase, interacted with EGFR, thus promoting ubiquitination at K716 and the subsequent degradation of EGFR. Importantly, the combination of JAC4 and AZD9191 synergistically inhibited the growth and metastasis of EGFR-mutant lung cancer in both subcutaneous and orthotopic NSCLC xenografts. Furthermore, direct binding of JAC4 to CTBP1 blocked nuclear translocation of CTBP1 and then removed its transcriptional suppression on the JWA gene. The small-molecule JWA agonist JAC4 plays a therapeutic role in EGFR-driven LUAD growth and metastasis through the CTBP1-mediated JWA/AMPK/NEDD4L/EGFR axis.

Bcl-xL is translocated to the nucleus via CtBP2 to epigenetically promote metastasis

Besides its mitochondria-based anti-apoptotic role, Bcl-xL also travels to the nucleus to promote cancer metastasis by upregulating global histone H3 trimethyl Lys4 (H3K4me3) and TGFβ transcription. How Bcl-xL is translocated into the nucleus and how nuclear Bcl-xL regulates H3K4me3 modification are not understood. Here, we report that C-terminal Binding Protein 2 (CtBP2) binds Bcl-xL via its N-terminus and translocates Bcl-xL into the nucleus. Knockdown of CtBP2 by shRNA decreases the nuclear portion of Bcl-xL and reverses Bcl-xL-induced cell migration and metastasis in mouse models. Furthermore, knockout of CtBP2 suppresses Bcl-xL transcription. The binding between Bcl-xL and CtBP2 is required for their interaction with MLL1, a histone H3K4 methyltransferase. Pharmacologic inhibition of MLL1 enzymatic activity reverses Bcl-xL-induced H3K4me3 and TGFβ mRNA upregulation as well as cell invasion. Moreover, cleavage under targets and release using nuclease (CUT&RUN) coupled with next generation sequencing reveals that H3K4me3 modifications are particularly enriched in the promotor region of genes encoding TGFβ and its signaling pathway in the cancer cells overexpressing Bcl-xL. Altogether, the metastatic function of Bcl-xL is mediated by its interaction with CtBP2 and MLL1.

Succinylation of CTBP1 mediated by KAT2A suppresses its inhibitory activity on the transcription of CDH1 to promote the progression of prostate cancer

CTBP1 has been demonstrated as a co-repressor in the transcriptional regulation of downstream genes and is involved in various cell process. However, the mechanism of CTBP1 in the progression of prostate cancer is still unclear. Here, we aim to investigate how CTBP1 exerts its role in prostate cancer progression, especially how CTBP1 was regulated by the upstream genes. We found that CTBP1 was highly expressed in prostate cancer and promoted the cell viability, migration, invasion and glycolysis of prostate cancer cells. CDH1 was verified to be the target of CTBP1. We determined that CTBP1 could directly bind with SP1 to inhibit the transcription of CDH1. Moreover, succinylation of CTBP1 was found to be up-regulated in prostate cancer cell. Further studies demonstrated that KAT2A promotes the succinylation of CTBP1 and mediates the transcription suppressing activity of it. In addition, the K46 and K280 was confirmed to be the two sites that regulated by KAT2A. In vivo studies further indicated that CTBP1 could promote the growth of prostate cancer, and this effect of CTBP1 could be partially reversed by KAT2A knockdown. Taken together, we found that succinylation of CTBP1 mediated by KAT2A suppresses the inhibitory activity of CTBP1 on the transcription of CDH1, thus act as an oncogene.

Transcription factors and potential therapeutic targets for pulmonary hypertension

Pulmonary hypertension (PH) is a refractory and fatal disease characterized by excessive pulmonary arterial cell remodeling. Uncontrolled proliferation and hypertrophy of pulmonary arterial smooth muscle cells (PASMCs), dysfunction of pulmonary arterial endothelial cells (PAECs), and abnormal perivascular infiltration of immune cells result in pulmonary arterial remodeling, followed by increased pulmonary vascular resistance and pulmonary pressure. Although various drugs targeting nitric oxide, endothelin-1 and prostacyclin pathways have been used in clinical settings, the mortality of pulmonary hypertension remains high. Multiple molecular abnormalities have been implicated in pulmonary hypertension, changes in numerous transcription factors have been identified as key regulators in pulmonary hypertension, and a role for pulmonary vascular remodeling has been highlighted. This review consolidates evidence linking transcription factors and their molecular mechanisms, from pulmonary vascular intima PAECs, vascular media PASMCs, and pulmonary arterial adventitia fibroblasts to pulmonary inflammatory cells. These findings will improve the understanding of particularly interactions between transcription factor-mediated cellular signaling pathways and identify novel therapies for pulmonary hypertension.

Up-regulated Circular RNAs in Colorectal Cancer: New Entities for Therapy and Tools for Identification of Therapeutic Targets

Patients with disseminated colorectal cancer have a dismal prognosis with a 5-year survival rate of only 13%. In order to identify new treatment modalities and new targets, we searched the literature for up-regulated circular RNAs in colorectal cancer which induce tumor growth in corresponding preclinical in vivo models. We identified nine circular RNAs that mediate resistance against chemotherapeutic agents, seven that up-regulate transmembrane receptors, five that induce secreted factors, nine that activate signaling components, five which up-regulate enzymes, six which activate actin-related proteins, six which induce transcription factors and two which up-regulate the MUSASHI family of RNA binding proteins. All of the circular RNAs discussed in this paper induce the corresponding targets by sponging microRNAs (miRs) and can be inhibited by RNAi or shRNA in vitro and in xenograft models. We have focused on circular RNAs with demonstrated activity in preclinical in vivo models because the latter is an important milestone in drug development. All circular RNAs with in vitro activity only data are not referenced in this review. The translational impact of inhibition of these circular RNAs and of the identified targets for treatment of colorectal cancer (CRC) are discussed.

The dorsal hippocampal CA3 regulates spatial reference memory through the CtBP2/GluR2 pathway

The dorsal hippocampus plays a pivotal role in spatial memory. However, the role of subregion-specific molecular pathways in spatial cognition remains unclear. We observed that the transcriptional coregulator C-terminal binding protein 2 (CtBP2) presented CA3-specific enrichment in expression. RNAi interference of CtBP2 in the dorsal CA3 (dCA3) neurons, but not the ventral CA3 (vCA3), specifically impaired spatial reference memory and reduced the expression of GluR2, the calcium permeability determinant subunit of AMPA receptors. Application of an antagonist for GluR2-absent calcium permeable AMPA receptors rescued spatial memory deficits in dCA3 CtBP2 knockdown animals. Transcriptomic analysis suggest that CtBP2 may regulate GluR2 protein level through post-translational mechanisms, especially by the endocytosis pathway which regulates AMPA receptor sorting. Consistently, CtBP2 deficiency altered the mRNA expression of multiple endocytosis-regulatory genes, and CtBP2 knockdown in primary hippocampal neurons enhanced GluR2-containing AMPA receptor endocytosis. Together, our results provide evidence that the dCA3 regulates spatial reference memory by the CtBP2/GluR2 pathway through the modulation of calcium permeable AMPA receptors.

Metabotropic Glutamate Receptors at Ribbon Synapses in the Retina and Cochlea

Our senses define our view of the world. They allow us to adapt to environmental stimuli and are essential for communication and social behaviour. For most humans, seeing and hearing are central senses for their daily life. Our eyes and ears respond to an extraordinary broad range of stimuli covering about 12 log units of light intensity or acoustic power, respectively. The cellular basis is represented by sensory cells (photoreceptors in the retina and inner hair cells in the cochlea) that convert sensory inputs into electrical signals. Photoreceptors and inner hair cells have developed a specific pre-synaptic structure, termed synaptic ribbon, that is decorated with numerous vesicles filled with the excitatory neurotransmitter glutamate. At these ribbon synapses, glutamatergic signal transduction is guided by distinct sets of metabotropic glutamate receptors (mGluRs). MGluRs belong to group II and III of the receptor classification can inhibit neuronal activity, thus protecting neurons from overstimulation and subsequent degeneration. Consequently, dysfunction of mGluRs is associated with vision and hearing disorders. In this review, we introduce the principle characteristics of ribbon synapses and describe group II and III mGluRs in these fascinating structures in the retina and cochlea.

Retinoic Acid-Induced 2 (RAI2) Is a Novel Antagonist of Wnt/β-Catenin Signaling Pathway and Potential Biomarker of Chemosensitivity in Colorectal Cancer

Objective

Aberrant activation of Wnt/β-catenin signaling contributes to the maintenance of cancer stem cells and chemoresistance in colorectal cancer (CRC). Retinoic acid-induced 2 (RAI2) was proved to be a tumor suppressor in CRC in our previous report. In this study, the role of RAI2 in Wnt/β-catenin signaling was further investigated.

Methods

As a transcriptional co-regulator, C-terminal Binding Protein 2 (CtBP2) was reported to be involved in Wnt signaling in multiple and complex ways. The correlation of RAI2 and CtBP2 in CRC was analyzed by TCGA dataset, and the interaction between RAI2 and CtBP2 was explored by co-immunoprecipitation (Co-IP) in CRC cells. The effect of RAI2 on the activity of Wnt signaling and the location of β-catenin was detected by Dual-Luciferase reporter assay and Immunofluorescence respectively. Western blotting analysis was performed to detect the expression of target genes involved in Wnt signaling. Sphere formation assay was employed to detect the effect of RAI2 on stem cell like properties. Cell viability assay was used to detect the chemosensitivity of cells before and after transfection of RAI2.

Results

The interaction between RAI2 and CtBP2 was confirmed by Co-IP in CRC cells. Besides, the negative correlation of RAI2 and CtBP2 in CRC was found by analyzing the TCGA dataset. Re-expression of RAI2 in human colon cancer cells (HCT116 and LoVo) suppressed the fluorescent activity of Wnt signaling, increased the phosphorylation and inhibited nuclear translocation of β-catenin, with down-regulation of target genes like c-Myc, CyclinD1, ASCL2, and LGR5. In contrast, the mutated RAI2, which can’t interact with CtBP2, has no above effects. We observed low expression of RAI2 in 33.89% (101/298) of CRC patients, which was significantly associated with reduced phosphorylation of β-catenin (r=0.8866, P<0.0001), poor 5-year relapse-free survival (RFS) (P = 0.0029) and overall survival (OS) (P = 0.0102). Restoration of RAI2 in HCT116 and LoVo cells inhibited stem cell-like properties of CRC cells and increased chemosensitivity of these cells to oxaliplatin and fluorouracil.

Conclusion

Low expression of RAI2 can serve as an independent poor prognostic marker. RAI2 inhibits Wnt signaling by interacting with or down-regulating CtBP2, resulting in repression of stem cell-like properties and increased chemosensitivity of CRC cells.

Inhibition of CtBP-Regulated Proinflammatory Gene Transcription Attenuates Psoriatic Skin Inflammation

Psoriasis is a chronic immune-mediated disease characterized by excessive proliferation of epidermal keratinocytes and increased immune cell infiltration to the skin. Although it is well-known that psoriasis pathogenesis is driven by aberrant production of proinflammatory cytokines, the mechanisms underlying the imbalance between proinflammatory and anti-inflammatory cytokine expression are incompletely understood. In this study, we report that the transcriptional coregulators CtBP1 and 2 can transactivate a common set of proinflammatory genes both in the skin of imiquimod-induced mouse psoriasis model and in human keratinocytes and macrophages stimulated by imiquimod. We find that mice overexpressing CtBP1 in epidermal keratinocytes display severe skin inflammation phenotypes with increased expression of T helper type 1 and T helper type 17 cytokines. We also find that the expression of CtBPs and CtBP-target genes is elevated both in human psoriatic lesions and in the mouse imiquimod psoriasis model. Moreover, we were able to show that topical treatment with a peptidic inhibitor of CtBP effectively suppresses the CtBP-regulated proinflammatory gene expression and thus attenuates psoriatic inflammation in the imiquimod mouse model. Together, our findings suggest to our knowledge previously unreported strategies for therapeutic modulation of the immune response in inflammatory skin diseases.

NADH/NAD+ binding and linked tetrameric assembly of the oncogenic transcription factors CtBP1 and CtBP2

The activation of oncogenic C-terminal binding Protein (CtBP) transcriptional activity is coupled with NAD(H) binding and homo-oligomeric assembly, although the level of CtBP assembly and nucleotide binding affinity continues to be debated. Here, we apply biophysical techniques to address these fundamental issues for CtBP1 and CtBP2. Our ultracentrifugation results unambiguously demonstrate that CtBP assembles into tetramers in the presence of saturating NAD⁺ or NADH with tetramer to dimer dissociation constants about 100 nm. Isothermal titration calorimetry measurements of NAD(H) binding to CtBP show dissociation constants between 30 and 500 nm, depending on the nucleotide and paralog. Given cellular levels of NAD⁺ , CtBP is likely to be fully saturated with NAD under physiological concentrations suggesting that CtBP is unable to act as a sensor for NADH levels.

Circular RNA circHERC4 as a novel oncogenic driver to promote tumor metastasis via the miR-556-5p/CTBP2/E-cadherin axis in colorectal cancer

BACKGROUND

The main cause of death in colorectal cancer patients is metastasis. Accumulating evidences suggest that circRNA plays pivotal roles in cancer initiation and development. However, the underlying molecular mechanisms of circRNAs that orchestrate cancer metastasis remain vague and need further clarification.

METHODS

Two paired CRC and adjacent normal tissues were used to screen the upregulated circRNAs by circRNA-seq; then, cell invasion assay was applied to confirm the functional invasion-related circRNAs. According to the above methods, circHERC4 (hsa_circ_0007113) was selected for further research. Next, we investigated the clinical significance of circHERC4 in a large cohort of patients with CRC. The oncogenic activity of circHERC4 was investigated in both CRC cell lines and animal xenograft studies. Finally, we explored the molecular mechanisms underlying circHERC4 as a malignant driver.

RESULTS

We demonstrated that circHERC4 was aberrantly elevated in CRC tissues (P < 0.001), and was positively associated with lymph node metastasis and advanced tumor grade (P < 0.01). Notably, the expression of circHERC4 was associated with worse survival in patients with CRC. Silencing of circHERC4 significantly inhibited the proliferation and migration of two highly aggressive CRC cell lines and reduced liver and lung metastasis in vivo. Mechanistically, we revealed that circHERC4 inactivated the tumor suppressor, miR-556-5p, leading to the activation of CTBP2/E-cadherin pathway which promotes tumor metastasis in CRC.

CONCLUSIONS

CircHERC4 exerts critical roles in promoting tumor aggressiveness through miR-556-5p/CTBP2/E-cadherin pathway and is a prognostic biomarker of the disease, suggesting that circHERC4 may serve as an exploitable therapeutic target for patients with CRC.

CTBP1 strengthens the cisplatin resistance of gastric cancer cells by upregulating RAD51 expression

Drug resistance is a key factor affecting the treatment of gastric cancer. The resistance of gastric cancer cells to anticancer drugs, such as cisplatin (DDP), remains a major challenge to patient recovery. The present study aimed to investigate the roles of C-terminal-binding protein 1 (CTBP1) in the DDP resistance of gastric cancer cells and to determine its regulatory effect on DNA repair protein RAD51 homolog 1 (RAD51). The DDP-resistant human gastric cancer AGS and HGC cell lines, AGS/DDP and HGC-27/DDP, respectively, were established and CTBP1 expression was detected by western blotting. In addition, Cell Counting Kit-8, colony formation and flow cytometry assays were performed to detect the proliferation and apoptosis of these two cell lines following CTBP1 knockdown. The expression levels of apoptosis-related proteins were detected by western blotting. In addition, RAD51 was overexpressed in CTBP1 knockdown cells, and proliferation and apoptosis were subsequently determined using the aforementioned methods. The results demonstrated that CTBP1 expression was notably increased in DDP-resistant gastric cancer cells. Furthermore, CTBP1 knockdown suppressed the proliferation and induced the apoptosis of AGS/DDP and HGC-27/DDP cells. Notably, CTBP1 promoted RAD51 expression in DDP-resistant gastric cancer cells. Overexpression of RAD51 in CTBP1 knockdown AGS/DDP and HGC-27/DDP cells rescued the proliferation and alleviated the apoptosis of these cells. Taken together, the results of the present study suggested that CTBP1 may enhance the DDP resistance of gastric cancer cells by activating RAD51 expression, thus providing a potential novel therapy (CTBP1 knockdown) for the clinical treatment of patients with gastric cancer.

Transcriptomics and Metabolomics Integration Reveals Redox-Dependent Metabolic Rewiring in Breast Cancer Cells

Rewiring glucose metabolism toward aerobic glycolysis provides cancer cells with a rapid generation of pyruvate, ATP, and NADH, while pyruvate oxidation to lactate guarantees refueling of oxidized NAD⁺ to sustain glycolysis. CtPB2, an NADH-dependent transcriptional co-regulator, has been proposed to work as an NADH sensor, linking metabolism to epigenetic transcriptional reprogramming. By integrating metabolomics and transcriptomics in a triple-negative human breast cancer cell line, we show that genetic and pharmacological down-regulation of CtBP2 strongly reduces cell proliferation by modulating the redox balance, nucleotide synthesis, ROS generation, and scavenging. Our data highlight the critical role of NADH in controlling the oncogene-dependent crosstalk between metabolism and the epigenetically mediated transcriptional program that sustains energetic and anabolic demands in cancer cells.

CtBP modulates Snail-mediated tumor invasion in Drosophila

Cancer is one of the most fatal diseases that threaten human health, whereas more than 90% mortality of cancer patients is caused by tumor metastasis, rather than the growth of primary tumors. Thus, how to effectively control or even reverse the migration of tumor cells is of great significance for cancer therapy. CtBP, a transcriptional cofactor displaying high expression in a variety of human cancers, has become one of the main targets for cancer prediction, diagnosis, and treatment. The roles of CtBP in promoting tumorigenesis have been well studied in vitro, mostly based on gain-of-function, while its physiological functions in tumor invasion and the underlying mechanism remain largely elusive. Snail (Sna) is a well-known transcription factor involved in epithelial-to-mesenchymal transition (EMT) and tumor invasion, yet the mechanism that regulates Sna activity has not been fully understood. Using Drosophila as a model organism, we found that depletion of CtBP or snail (sna) suppressed Ras^V12/lgl^-/--triggered tumor growth and invasion, and disrupted cell polarity-induced invasive cell migration. In addition, loss of CtBP inhibits Ras^V12/Sna-induced tumor invasion and Sna-mediated invasive cell migration. Furthermore, both CtBP and Sna are physiologically required for developmental cell migration during thorax closure. Finally, Sna activates the JNK signaling and promotes JNK-dependent cell invasion. Given that CtBP physically interacts with Sna, our data suggest that CtBP and Sna may form a transcriptional complex that regulates JNK-dependent tumor invasion and cell migration in vivo.

CtBP1/2 differentially regulate genomic stability and DNA repair pathway in high-grade serous ovarian cancer cell

The C-terminal binding proteins (CtBPs), CtBP1 and CtBP2, are transcriptional co-repressor that interacts with multiple transcriptional factors to modulate the stability of chromatin. CtBP proteins were identified with overexpression in the high-grade serous ovarian carcinoma (HGSOC). However, little is known about CtBP proteins’ regulatory roles in genomic stability and DNA repair in HGSOC. In this study, we combined whole-transcriptome analysis with multiple research methods to investigate the role of CtBP1/2 in genomic stability. Several key functional pathways were significantly enriched through whole transcription profile analysis of CtBP1/2 knockdown SKOV3 cells, including DNA damage repair, apoptosis, and cell cycle. CtBP1/2 knockdown induced cancer cell apoptosis, increased genetic instability, and enhanced the sensitivity to DNA damage agents, such as γ-irradiation and chemotherapy drug (Carboplatin and etoposide). The results of DNA fiber assay revealed that CtBP1/2 contribute differentially to the integrity of DNA replication track and stability of DNA replication recovery. CtBP1 protects the integrity of stalled forks under metabolic stress condition during prolonged periods of replication, whereas CtBP2 acts a dominant role in stability of DNA replication recovery. Furthermore, CtBP1/2 knockdown shifted the DSBs repair pathway from homologous recombination (HR) to non-homologous end joining (NHEJ) and activated DNA-PK in SKOV3 cells. Interesting, blast through TCGA tumor cases, patients with CtBP2 genetic alternation had a significantly longer overall survival time than unaltered patients. Together, these results revealed that CtBP1/2 play a different regulatory role in genomic stability and DSBs repair pathway bias in serous ovarian cancer cells. It is possible to generate novel potential targeted therapy strategy and translational application for serous ovarian carcinoma patients with a predictable better clinical outcome.

The transrepression and transactivation roles of CtBPs in the pathogenesis of different diseases

Gene transcription is strictly controlled by transcriptional complexes, which are assemblies of transcription factors, transcriptional regulators, and co-regulators. Mammalian genomes encode two C-terminal-binding proteins (CtBPs), CtBP1 and CtBP2, which are both well-known transcriptional corepressors of oncogenic processes. Their overexpression in tumors is associated with malignant behavior, such as uncontrolled cell proliferation, migration, and invasion, as well as with an increase in the epithelial-mesenchymal transition. CtBPs coordinate with other transcriptional regulators, such as histone deacetylases (HDACs) and histone acetyltransferases (p300 and CBP [CREBP-binding protein]) that contain the PXDLS motif, and with transcription factors to assemble transcriptional complexes that dock onto the promoters of genes to initiate gene transcription. Emerging evidence suggests that CtBPs function as both corepressors and coactivators in different biological processes ranging from apoptosis to inflammation and osteogenesis. Therapeutic targeting of CtBPs or the interactions required to form transcriptional complexes has also shown promising effects in preventing disease progression. This review summarizes the most recent progress in the study of CtBP functions and therapeutic inhibitors in different biological processes. This knowledge may enable a better understanding of the complexity of the roles of CtBPs, while providing new insights into therapeutic strategies that target CtBPs.

Genetic variants in epithelial-mesenchymal transition genes as predictors of clinical outcomes in localized prostate cancer

BACKGROUND

Epithelial-mesenchymal transition (EMT) plays a pivotal role in the progression of prostate cancer (PCa). However, little is known about genetic variants in the EMT pathway as predictors of aggressiveness, biochemical recurrence (BCR) and disease reclassification in localized PCa.

PATIENTS AND METHODS

In this multistage study, we evaluated 5186 single nucleotide polymorphisms (SNPs) from 264 genes related to EMT pathway to identify SNPs associated with PCa aggressiveness and BCR in the MD Anderson PCa (MDA-PCa) patient cohort (N = 1762), followed by assessment of the identified SNPs with disease reclassification in the active surveillance (AS) cohort (N = 392).

RESULTS

In the MDA-PCa cohort, 312 SNPs were associated with high D'Amico risk (P < 0.05), among which, 14 SNPs in 10 genes were linked to BCR risk. In the AS cohort, 2 of 14 identified SNPs (rs76779889 and rs7083961) in C-terminal Binding Proteins 2 gene were associated with reclassification risk. The associations of rs76779889 with different endpoints were: D'Amico high versus low, odds ratio [95% confidence interval (CI)] = 2.89 (1.32-6.34), P = 0.008; BCR, hazard ratio (HR) (95% CI) = 2.88 (1.42-5.85), P = 0.003; and reclassification, HR (95% CI) = 2.83 (1.40-5.74), P = 0.004. For rs7083961, the corresponding risk estimates were: D'Amico high versus low, odds ratio (95% CI) = 1.69 (1.12-2.57), P = 0.013; BCR, HR (95% CI) = 1.87 (1.15-3.02), P = 0.011 and reclassification, HR (95% CI) = 1.72 (1.09-2.72), P = 0.020. There were cumulative effects of these two SNPs on modulating these endpoints.

CONCLUSION

Genetic variants in EMT pathway may influence the risks of localized PCa's aggressiveness, BCR and disease reclassification, suggesting their potential role in the assessment and management of localized PCa.

LSD1 as a Biomarker and the Outcome of Its Inhibitors in the Clinical Trial: The Therapy Opportunity in Tumor

Tumors are the foremost cause of death worldwide. As a result of that, there has been a significant enhancement in the investigation, treatment methods, and good maintenance practices on cancer. However, the sensitivity and specificity of a lot of tumor biomarkers are not adequate. Hence, it is of inordinate significance to ascertain novel biomarkers to forecast the prognosis and therapy targets for tumors. This review characterized LSD1 as a biomarker in different tumors. LSD1 inhibitors in clinical trials were also discussed. The recent pattern advocates that LSD1 is engaged at sauce chromatin zones linking with complexes of multi-protein having an exact DNA-binding transcription factor, establishing LSD1 as a favorable epigenetic target, and also gives a large selection of therapeutic targets to treat different tumors. This review sturdily backing the oncogenic probable of LSD1 in different tumors indicated that LSD1 levels can be used to monitor and identify different tumors and can be a useful biomarker of progression and fair diagnosis in tumor patients. The clinical trials showed that inhibitors of LSD1 have growing evidence of clinical efficacy which is very encouraging and promising. However, for some of the inhibitors such as GSK2879552, though selective, potent, and effective, its disease control was poor as the rate of adverse events (AEs) was high in tumor patients causing clinical trial termination, and continuation could not be supported by the risk-benefit profile. Therefore, we propose that, to attain excellent clinical results of inhibitors of LSD1, much attention is required in designing appropriate dosing regimens, developing in-depth in vitro/in vivo mechanistic works of LSD1 inhibitors, and developing inhibitors of LSD1 that are reversible, safe, potent, and selective which may offer safer profiles.

CtBP1-Mediated Membrane Fission Contributes to Effective Recycling of Synaptic Vesicles

Compensatory endocytosis of released synaptic vesicles (SVs) relies on coordinated signaling at the lipid-protein interface. Here, we address the synaptic function of C-terminal binding protein 1 (CtBP1), a ubiquitous regulator of gene expression and membrane trafficking in cultured hippocampal neurons. In the absence of CtBP1, synapses form in greater density and show changes in SV distribution and size. The increased basal neurotransmission and enhanced synaptic depression could be attributed to a higher vesicular release probability and a smaller fraction of release-competent SVs, respectively. Rescue experiments with specifically targeted constructs indicate that, while synaptogenesis and release probability are controlled by nuclear CtBP1, the efficient recycling of SVs relies on its synaptic expression. The ability of presynaptic CtBP1 to facilitate compensatory endocytosis depends on its membrane-fission activity and the activation of the lipid-metabolizing enzyme PLD1. Thus, CtBP1 regulates SV recycling by promoting a permissive lipid environment for compensatory endocytosis.

NAD(H) phosphates mediate tetramer assembly of human C-terminal binding protein (CtBP)

C-terminal binding proteins (CtBPs) are cotranscriptional factors that play key roles in cell fate. We have previously shown that NAD(H) promotes the assembly of similar tetramers from either human CtBP1 and CtBP2 and that CtBP2 tetramer destabilizing mutants are defective for oncogenic activity. To assist structure-based design efforts for compounds that disrupt CtBP tetramerization, it is essential to understand how NAD(H) triggers tetramer assembly. Here, we investigate the moieties within NAD(H) that are responsible for triggering tetramer formation. Using multiangle light scattering (MALS), we show that ADP is able to promote tetramer formation of both CtBP1 and CtBP2, whereas AMP promotes tetramer assembly of CtBP1, but not CtBP2. Other NAD(H) moieties that lack the adenosine phosphate, including adenosine and those incorporating nicotinamide, all fail to promote tetramer assembly. Our crystal structures of CtBP1 with AMP reveal participation of the adenosine phosphate in the tetrameric interface, pinpointing its central role in NAD(H)-linked assembly. CtBP1 and CtBP2 have overlapping but unique roles, suggesting that a detailed understanding of their unique structural properties might have utility in the design of paralog-specific inhibitors. We investigated the different responses to AMP through a series of site-directed mutants at 13 positions. These mutations reveal a central role for a hinge segment, which we term the 120s hinge that connects the substrate with coenzyme-binding domains and influences nucleotide binding and tetramer assembly. Our results provide insight into suitable pockets to explore in structure-based drug design to interfere with cotranscriptional activity of CtBP in cancer.

C-Terminal Binding Proteins Promote Neurogenesis and Oligodendrogenesis in the Subventricular Zone

C-terminal binding proteins (CtBPs) are transcriptional modulators that can regulate gene expression through the recruitment of a corepressor complex composed of chromatin-modifying enzymes and transcriptional factors. In the brain, CtBPs have been described as regulators of cell proliferation, differentiation, and survival. Nevertheless, the role of CtBPs on postnatal neural stem cells (NSCs) fate is not known yet. Herein, we evaluate the expression and functions of CtBPs in postnatal NSCs from the subventricular zone (SVZ). We found that CtBPs were expressed in immature/progenitor cells, neurons and glial cells in the SVZ niche. Using the CtBPs modulator 4-methylthio 2-oxobutyric acid (MTOB), our results showed that 1 mM of MTOB induced cell death, while 5, 25, and 50 μM increased the number of proliferating neuroblasts, mature neurons, and oligodendrocytes. Interestingly, it also increased the dendritic complexity of immature neurons. Altogether, our results highlight CtBPs putative application for brain regenerative applications.

Arabidopsis C-terminal binding protein ANGUSTIFOLIA modulates transcriptional co-regulation of MYB46 and WRKY33

The apparent antagonism between salicylic acid (SA) and jasmonic acid (JA)/ethylene (ET) signalling resulting in trade-offs between defence against (hemi)biotrophic and necrotrophic pathogens has been widely described across multiple plant species. However, the underlying mechanism remains to be fully established. The molecular and cellular functions of ANGUSTIFOLIA (AN) were characterised, and its role in regulating the pathogenic response was studied in Arabidopsis. We demonstrated that AN, a plant homologue of mammalian C-TERMINAL BINDING PROTEIN (CtBP), antagonistically regulates plant resistance to the hemibiotrophic pathogen Pseudomonas syringae and the necrotrophic pathogen Botrytis cinerea. Consistent with phenotypic observations, transcription of genes involved in SA and JA/ET pathways was antagonistically regulated by AN. By interacting with another nuclear protein TYROSYL-DNA PHOSPHODIESTERASE1 (TDP1), AN imposes transcriptional repression on MYB46, encoding a transcriptional activator of PHENYLALANINE AMMONIA-LYASE (PAL) genes which are required for SA biosynthesis, while releasing TDP1-imposed transcriptional repression on WRKY33, a master regulator of the JA/ET signalling pathway. These findings demonstrate that transcriptional co-regulation of MYB46 and WRKY33 by AN mediates the coordination of SA and JA/ET pathways to optimise defences against (hemi)biotrophic and necrotrophic pathogens.

Cryo-EM structure of CtBP2 confirms tetrameric architecture

C-terminal binding proteins 1 and 2 (CtBP1 and CtBP2) are transcriptional regulators that activate or repress many genes involved in cellular development, apoptosis, and metastasis. NADH-dependent CtBP activation has been implicated in multiple types of cancer and poor patient prognosis. Central to understanding activation of CtBP in oncogenesis is uncovering how NADH triggers protein assembly, what level of assembly occurs, and if oncogenic activity depends upon such assembly. Here, we present the cryoelectron microscopic structures of two different constructs of CtBP2 corroborating that the native state of CtBP2 in the presence of NADH is tetrameric. The physiological relevance of the observed tetramer was demonstrated in cell culture, showing that CtBP tetramer-destabilizing mutants are defective for cell migration, transcriptional repression of E-cadherin, and activation of TIAM1. Together with our cryoelectron microscopy studies, these results highlight the tetramer as the functional oligomeric form of CtBP2.

Low expression of CTBP2 and CASP8AP2 predicts risk of relapse in childhood B-cell precursor acute lymphoblastic leukemia: a retrospective cohort study

CtBP is a known corepressor abundantly expressed in cancer and regulates genes involved in cancer initiation, progression, and metastasis. This study aimed to investigate the prognostic significance of CTBP2 expression in a cohort of pediatric patients with B cell precursor acute lymphoblastic leukemia (BCP-ALL). It further evaluated the role of combined CTBP2 and CASP8AP2 expression in risk of relapse of BCP-ALL. The expression of CTBP2 mRNA was retrospectively detected by a qRT-PCR approach in bone marrow samples from 104 children with newly diagnosed BCP-ALL. CASP8AP2 was assessed simultaneously in the 100 patients included in this study. The receiver operating characteristic (ROC) curve analysis determined the cut off levels for CTBP2 and CASP8AP2 expression with good predictive significance for relapse of BCP-ALL. Patients with low CTBP2 expression had inferior relapse-free survival (RFS) and event-free survival (EFS) when compared to patients with high-CTBP2 expression. The expression level of CTBP2 was significantly associated with CASP8AP2 expression (r = 0.449, P < 0.001). Patients were stratified into three groups according to the combined evaluation of the two gene expression, and patients with simultaneous low-expression had the worst outcome (6-year RFS: 64.6%±12.8%, P < 0.001). Multivariate analysis demonstrated the expression of CTBP2 and CASP8AP2, minimal residual disease (MRD) at day 33 remained as independent prognostic factors for RFS. Based on the final Cox hazards model, we proposed an algorithm to calculate the risk index, which was more precise for predicting relapse. In conclusion, low expression of CTBP2 and CASP8AP2 correlated with poor outcome and predicted risk of relapse in pediatric BCP-ALL.

TLE2 is associated with favorable prognosis and regulates cell growth and gemcitabine sensitivity in pancreatic cancer

Background

The transducin-like enhancer of split (TLE) proteins are a group of transcriptional corepressors. They play a crucial role in cellular homeostasis and are involved in various cancers. Compared with other TLE family members, little is known about the role and the underlying mechanism of TLE2 in human cancers. This study aimed to investigate the role of TLE2 in pancreatic ductal adenocarcinoma (PDAC) using in silico analysis and in vitro experiments.

Methods

Data were obtained from the Cancer Genome Atlas (TCGA) database to evaluate the prognostic value of TLE2 in PDAC. The MiaPaCa-2 cell line was transfected with siRNA to inhibit endogenous TLE2 expression, and a PANC-1 cell line with stable TLE2 overexpression was constructed using lentiviral transfection, which were confirmed by real-time polymerase chain reaction and western blotting. MTT assay, transwell invasion assays, and flow cytometry were carried out to assess cell viability, invasion, and apoptosis, respectively. TLE2 expression in PDAC cells was altered to evaluate their sensitivity to gemcitabine. Gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to predict the biological role of TLE2.

Results

High expression of TLEs was significantly associated with increased overall survival (OS) and disease-free survival (DFS) in patients with PDAC. Among the PDAC cell lines, TLE2 expression was lowest and highest in PANC-1 cells and MiaPaCa-2 cells, respectively. TLE2 overexpression impaired the proliferation ability of PANC-1 cells and downregulation of TLE2 promoted the proliferation of MiaPaCa-2 cells. Upregulation of TLE2 in PANC-1 cells induced S-phase accumulation and sensitivity to gemcitabine. In contrast, the downregulation of TLE2 in MiaPaCa-2 cells promoted resistance to gemcitabine. Moreover, bioinformatics analysis also revealed the potential tumor suppressor role of TLE2 and uncovered a close relationship between TLE2 expression and cell cycle regulation.

Conclusions

Our results suggest that TLE2 expression is correlated with prognosis in patients with PDAC and show that TLE2 plays a central role in the regulation of cell proliferation, the cell cycle, and gemcitabine sensitivity. This study provides new insights and evidence that TLE2 functions as a tumor suppressor gene and prognostic marker in PDAC.

CtBP2 interacts with ZBTB18 to promote malignancy of glioblastoma

OBJECTIVE

To investigate how the interaction of CtBP2 with ZBTB18 affect glioblastoma (GBM).

METHODS

Western blotting was performed to detect CtBP2 and ZBTB18 expression in GBM and normal brain tissues (NBT). U-87 MG cells were transfected with ZBTB18 CRISPR activation plasmid, CtBP2 shRNA with/without ZBTB18 shRNA. The biological characteristics were detected by EdU assay, MTT, Wound-healing, Transwell, TUNEL staining, and Flow cytometry. Furthermore, U-87 MG cells transfected with CtBP2 shRNA and/or ZBTB18 shRNA were injected into the flank region of mice and the tumor volume was measured. The mRNA and protein expression was quantified by qRT-PCR or Western blotting.

RESULTS

GBM tissues exhibited increased CtBP2 expression and decreased ZBTB18 expression, which demonstrated a negative correlation in GBM tissues and showed the combined effect on prognosis. Based on immunoprecipitation and immunofluorescence, there was an interaction between CtBP2 and ZBTB18 in U-87 MG cells. CtBP2 shRNA counteracted the effect of ZBTB18 shRNA on inhibiting U-87 MG cell apoptosis, as well as promoting cell proliferation and viability with increased EMT, invasion and migration. Meanwhile, CtBP2 shRNA interact with ZBTB18 to block cells at phase G0/G1 and suppress SHH-GLI1 pathway. CtBP2 shRNA decreased tumor volume, increase ZBTB18 expression in tumor tissues, and inhibit SHH-GLI1 pathway in mice, which could be reversed by ZBTB18 shRNA.

CONCLUSION

CtBP2 elevation and ZBTB18 down-regulation were found in GBM, both of which were associated with prognosis of GBM patients. CtBP2 interacted with ZBTB18 to affect biological characteristics of GBM cells, and the tumor growth, which may be related to the SHH-GLI1 pathway.

Stabilization of C-terminal binding protein 2 by cellular inhibitor of apoptosis protein 1 via BIR domains without E3 ligase activity

C-terminal binding protein 2 (CtBP2) is a transcriptional co-repressor that regulates many genes involved in normal cellular events. Because CtBP2 overexpression has been implicated in various human cancers, its protein levels must be precisely regulated. Previously, we reported that CtBP1 and CtBP1-mediated transcriptional repression are regulated by X-linked inhibitor of apoptosis protein (XIAP). In the present study, we sought to investigate whether CtBP2 is also regulated by XIAP or any other human IAP. We found that cIAP1 interacts with CtBP2 via through BIR domains to regulates the steady-state levels of CtBP2 protein in the nucleus. The levels of CtBP2 were gradually increased upon cIAP1 overexpression and downregulated upon cIAP1 depletion. Interestingly, the RING domain of cIAP1 responsible for E3 ligase activity was not required for this regulation. Finally, the levels of CtBP2 modulated by cIAP1 affected the transcription of CtBP2 target genes and subsequent cell migration. Taken together, our data demonstrate a novel function of cIAP1 which involves protecting CtBP2 from degradation to stabilize its steady-state level. These results suggest that cIAP1 might be a useful target in strategies aiming to downregulate the steady-state level of CtBP2 protein in treating human cancers.

Glycolysis, via NADH-dependent dimerisation of CtBPs, regulates hypoxia-induced expression of CAIX and stem-like breast cancer cell survival

Adaptive responses to hypoxia are mediated by the hypoxia-inducible factor (HIF) family of transcription factors. These responses include the upregulation of glycolysis to maintain ATP production. This also generates acidic metabolites, which require HIF-induced carbonic anhydrase IX (CAIX) for their neutralisation. C-terminal binding proteins (CtBPs) are coregulators of gene transcription and couple glycolysis with gene transcription due to their regulation by the glycolytic coenzyme NADH. Here, we find that experimental manipulation of glycolysis and CtBP function in breast cancer cells through multiple complementary approaches supports a hypothesis whereby the expression of known HIF-inducible genes, and CAIX in particular, adapts to available glucose in the microenvironment through a mechanism involving CtBPs. This novel pathway promotes the survival of stem cell-like cancer (SCLC) cells in hypoxia.

NSM00158 Specifically Disrupts the CtBP2-p300 Interaction to Reverse CtBP2-Mediated Transrepression and Prevent the Occurrence of Nonunion

Carboxyl-terminal binding proteins (CtBPs) are transcription regulators that control gene expression in multiple cellular processes. Our recent findings indicated that overexpression of CtBP2 caused the repression of multiple bone development and differentiation genes, resulting in atrophic nonunion. Therefore, disrupting the CtBP2-associated transcriptional complex with small molecules may be an effective strategy to prevent nonunion. In the present study, we developed an in vitro screening system in yeast cells to identify small molecules capable of disrupting the CtBP2-p300 interaction. Herein, we focus our studies on revealing the in vitro and in vivo effects of a small molecule NSM00158, which showed the strongest inhibition of the CtBP2-p300 interaction in vitro. Our results indicated that NSM00158 could specifically disrupt CtBP2 function and cause the disassociation of the CtBP2-p300-Runx2 complex. The impairment of this complex led to failed binding of Runx2 to its downstream targets, causing their upregulation. Using a mouse fracture model, we evaluated the in vivo effect of NSM00158 on preventing nonunion. Consistent with the in vitro results, the NSM00158 treatment resulted in the upregulation of Runx2 downstream targets. Importantly, we found that the administration of NSM00158 could prevent the occurrence of nonunion. Our results suggest that NSM00158 represents a new potential compound to prevent the occurrence of nonunion by disrupting CtBP2 function and impairing the assembly of the CtBP2-p300-Runx2 transcriptional complex.

p53 is regulated by aerobic glycolysis in cancer cells by the CtBP family of NADH-dependent transcriptional regulators

High rates of glycolysis in cancer cells are a well-established characteristic of many human tumors, providing rapidly proliferating cancer cells with metabolites that can be used as precursors for anabolic pathways. Maintenance of high glycolytic rates depends on the lactate dehydrogenase-catalyzed regeneration of NAD⁺ from GAPDH-generated NADH because an increased NADH:NAD⁺ ratio inhibits GAPDH. Here, using human breast cancer cell models, we identified a pathway in which changes in the extramitochondrial-free NADH:NAD⁺ ratio signaled through the CtBP family of NADH-sensitive transcriptional regulators to control the abundance and activity of p53. NADH-free forms of CtBPs cooperated with the p53-binding partner HDM2 to suppress p53 function, and loss of these forms in highly glycolytic cells resulted in p53 accumulation. We propose that this pathway represents a "glycolytic stress response" in which the initiation of a protective p53 response by an increased NADH:NAD⁺ ratio enables cells to avoid cellular damage caused by mismatches between metabolic supply and demand.

C-terminal binding proteins 1 and 2 in traumatic brain injury-induced inflammation and their inhibition as an approach for anti-inflammatory treatment

Traumatic brain injury (TBI) induces an acute inflammatory response in the central nervous system that involves both resident and peripheral immune cells. The ensuing chronic neuroinflammation causes cell death and tissue damage and may contribute to neurodegeneration. The molecular mechanisms involved in the maintenance of this chronic inflammation state remain underexplored. C-terminal binding protein (CtBP) 1 and 2 are transcriptional coregulators that repress diverse cellular processes. Unexpectedly, we find that the CtBPs can transactivate a common set of proinflammatory genes both in lipopolysaccharide-activated microglia, astrocytes and macrophages, and in a mouse model of the mild form of TBI. We also find that the expression of these genes is markedly enhanced by a single mild injury in both brain and peripheral blood leukocytes in a severity- and time-dependent manner. Moreover, we were able to demonstrate that specific inhibitors of the CtBPs effectively suppress the expression of the CtBP target genes and thus improve neurological outcome in mice receiving single and repeated mild TBIs. This discovery suggests new avenues for therapeutic modulation of the inflammatory response to brain injury.