Specific inhibition of CBP/beta-catenin interaction rescues defects in neuronal differentiation caused by a presenilin-1 mutation

Nicotinamide and pyridoxine stimulate muscle stem cell expansion and enhance regenerative capacity during aging

Skeletal muscle relies on resident muscle stem cells (MuSCs) for growth and repair. Aging and muscle diseases impair MuSC function, leading to stem cell exhaustion and regenerative decline that contribute to the progressive loss of skeletal muscle mass and strength. In the absence of clinically available nutritional solutions specifically targeting MuSCs, we used a human myogenic progenitor high-content imaging screen of natural molecules from food to identify nicotinamide (NAM) and pyridoxine (PN) as bioactive nutrients that stimulate MuSCs and have a history of safe human use. NAM and PN synergize via CK1-mediated cytoplasmic β-catenin activation and AKT signaling to promote amplification and differentiation of MuSCs. Oral treatment with a combination of NAM and PN accelerated muscle regeneration in vivo by stimulating MuSCs, increased muscle strength during recovery, and overcame MuSC dysfunction and regenerative failure during aging. Levels of NAM and bioactive PN spontaneously declined during aging in model organisms and interindependently associated with muscle mass and walking speed in a cohort of 186 aged people. Collectively, our results establish the NAM/PN combination as a nutritional intervention that stimulates MuSCs, enhances muscle regeneration, and alleviates age-related muscle decline with a direct opportunity for clinical translation.

Targeting CBP and p300: Emerging Anticancer Agents

CBP and p300 are versatile transcriptional co-activators that play essential roles in regulating a wide range of signaling pathways, including Wnt/β-catenin, p53, and HIF-1α. These co-activators influence various cellular processes such as proliferation, differentiation, apoptosis, and response to hypoxia, making them pivotal in normal physiology and disease progression. The Wnt/β-catenin signaling pathway, in particular, is crucial for cellular proliferation, differentiation, tissue homeostasis, and embryogenesis. Aberrant activation of this pathway is often associated with several types of cancer, such as colorectal tumor, prostate cancer, pancreatic and hepatocellular carcinomas. In recent years, significant efforts have been directed toward identifying and developing small molecules as novel anticancer agents capable of specifically inhibiting the interaction between β-catenin and the transcriptional co-activators CBP and p300, which are required for Wnt target gene expression and are consequently involved in the regulation of tumor cell proliferation, migration, and invasion. This review summarizes the most significant and original research articles published from 2010 to date, found by means of a PubMed search, highlighting recent advancements in developing both specific and non-specific inhibitors of CBP/β-catenin and p300/β-catenin interactions. For a more comprehensive view, we have also explored the therapeutic potential of CBP/p300 bromodomain and histone acetyltransferase inhibitors in disrupting the transcriptional activation of genes involved in various signaling pathways related to cancer progression. By focusing on these therapeutic strategies, this review aims to offer a detailed overview of recent approaches in cancer treatment that selectively target CBP and p300, with particular emphasis on their roles in Wnt/β-catenin-driven oncogenesis.

Why Is Wnt/β-Catenin Not Yet Targeted in Routine Cancer Care?

Despite significant progress in cancer prevention, screening, and treatment, the still limited number of therapeutic options is an obstacle towards increasing the cancer cure rate. In recent years, many efforts were put forth to develop therapeutics that selectively target different components of the oncogenic Wnt/β-catenin signaling pathway. These include small molecule inhibitors, antibodies, and more recently, gene-based approaches. Although some of them showed promising outcomes in clinical trials, the Wnt/β-catenin pathway is still not targeted in routine clinical practice for cancer management. As for most anticancer treatments, a critical limitation to the use of Wnt/β-catenin inhibitors is their therapeutic index, i.e., the difficulty of combining effective anticancer activity with acceptable toxicity. Protecting healthy tissues from the effects of Wnt/β-catenin inhibitors is a major issue due to the vital role of the Wnt/β-catenin signaling pathway in adult tissue homeostasis and regeneration. In this review, we provide an up-to-date summary of clinical trials on Wnt/β-catenin pathway inhibitors, examine their anti-tumor activity and associated adverse events, and explore strategies under development to improve the benefit/risk profile of this therapeutic approach.

3D Chromatin Alteration by Disrupting β-Catenin/CBP Interaction Is Enriched with Insulin Signaling in Pancreatic Cancer

The therapeutic potential of targeting the β-catenin/CBP interaction has been demonstrated in a variety of preclinical tumor models with a small molecule inhibitor, ICG-001, characterized as a β-catenin/CBP antagonist. Despite the high binding specificity of ICG-001 for the N-terminus of CBP, this β-catenin/CBP antagonist exhibits pleiotropic effects. Our recent studies found global changes in three-dimensional (3D) chromatin architecture in response to disruption of the β-catenin/CBP interaction in pancreatic cancer cells. However, an understanding of how the functional crosstalk between the antagonist and the β-catenin/CBP interaction affects changes in 3D chromatin architecture and, thereby, gene expression and downstream effects remains to be elucidated. Here, we perform Hi-C analyses on canonical and patient-derived pancreatic cancer cells before and after treatment with ICG-001. In addition to global alteration of 3D chromatin domains, we unexpectedly identify insulin signaling genes enriched in the altered chromatin domains. We further demonstrate that the chromatin loops associated with insulin signaling genes are significantly weakened after ICG-001 treatment. We finally elicit the deletion of a looping of IRS1-a key insulin signaling gene-significantly impeding pancreatic cancer cell growth, indicating that looping-mediated insulin signaling might act as an oncogenic pathway to promote pancreatic cancer progression. Our work shows that targeting aberrant insulin chromatin looping in pancreatic cancer might provide a therapeutic benefit.

HGF secreted by hUC-MSCs mitigates neuronal apoptosis to repair the injured spinal cord via phosphorylation of Akt/FoxO3a pathway

Spinal cord injury (SCI) can cause severe and permanent neurological damage, and neuronal apoptosis could inhibit functional recovery of damaged spinal cord greatly. Human umbilical cord mesenchymal stem cells (hUC-MSCs) have great potential to repair SCI because of a series of advantages, including inhibition of neuronal apoptosis and multiple differentiation. The former may play an important role. However, the detailed regulatory mechanism associated with the inhibition of neuronal apoptosis after hUC-MSCs administration has not been elucidated. In this study, proteomics analysis of precious human cerebrospinal fluid (CSF) samples collected from SCI subjects receiving hUC-MSCs delivery indicated that hepatocyte growth factor (HGF) is largely involved in SCI repair. Furthermore, overexpression of HGF derived from hUC-MSCs could decrease reactive oxygen species to prevent neuron apoptosis to the maximum, and thus lead to significant recovery of spinal cord dysfunction. Moreover, HGF could promote phosphorylation of Akt/FoxO3a pathway to decrease reactive oxygen species to reduce neuron apoptosis. For the first time, our research revealed that HGF secreted by hUC-MSCs inhibits neuron apoptosis by phosphorylation of Akt/FoxO3a to repair SCI. This study provides important clues associated with drug selection for the effective treatment of SCI in humans.

Reprogramming of 3D chromatin domains by antagonizing the β-catenin/CBP interaction attenuates insulin signaling in pancreatic cancer

The therapeutic potential of targeting the β-catenin/CBP interaction has been demonstrated in a variety of preclinical tumor models with a small molecule inhibitor, ICG-001, characterized as a β-catenin/CBP antagonist. Despite the high binding specificity of ICG-001 for the N-terminus of CBP, this β-catenin/CBP antagonist exhibits pleiotropic effects. Our recent studies found global changes in three-dimensional (3D) chromatin architecture in response to disruption of the β-catenin/CBP interaction in pancreatic cancer cells. However, an understanding of the functional crosstalk between antagonizing the β-catenin/CBP interaction effect changes in 3D chromatin architecture and thereby gene expression and downstream effects remains to be elucidated. Here we perform Hi-C analyses on canonical and patient-derived pancreatic cancer cells before and after the treatment with ICG-001. In addition to global alteration of 3D chromatin domains, we unexpectedly identify insulin signaling genes enriched in the altered chromatin domains. We further demonstrate the chromatin loops associated with insulin signaling genes are significantly weakened after ICG-001 treatment. We finally elicit the deletion of a looping of IRS1, a key insulin signaling gene, significantly impede pancreatic cancer cell growth, indicating that looping-mediated insulin signaling might act as an oncogenic pathway to promote pancreatic cancer progression. Our work shows that targeting aberrant insulin chromatin looping in pancreatic cancer might provide a therapeutic benefit.

Stromal-induced epithelial-mesenchymal transition induces targetable drug resistance in acute lymphoblastic leukemia

The bone marrow microenvironment (BME) drives drug resistance in acute lymphoblastic leukemia (ALL) through leukemic cell interactions with bone marrow (BM) niches, but the underlying mechanisms remain unclear. Here, we show that the interaction between ALL and mesenchymal stem cells (MSCs) through integrin β1 induces an epithelial-mesenchymal transition (EMT)-like program in MSC-adherent ALL cells, resulting in drug resistance and enhanced survival. Moreover, single-cell RNA sequencing analysis of ALL-MSC co-culture identifies a hybrid cluster of MSC-adherent ALL cells expressing both B-ALL and MSC signature genes, orchestrated by a WNT/β-catenin-mediated EMT-like program. Blockade of interaction between β-catenin and CREB binding protein impairs the survival and drug resistance of MSC-adherent ALL cells in vitro and results in a reduction in leukemic burden in vivo. Targeting of this WNT/β-catenin-mediated EMT-like program is a potential therapeutic approach to overcome cell extrinsically acquired drug resistance in ALL.

Anti-inflammatory and antifibrotic effects of CBP/β-catenin inhibitor for hepatocytes: small molecular inhibitor, OP-724 possibly improves liver function

Wnt/β-catenin signals are associated with several functions, including organ fibrosis. A synthetic small molecule, OP-724 (prodrug of C-82), an inhibitor of cyclic AMP response element-binding protein (CREB)-binding protein (CBP)/β-catenin, has demonstrated antifibrotic activity in mouse models of hepatic fibrosis. OP-724 is mediated by profibrotic and antifibrotic cells, such as hepatic stellate cells, macrophages, and neutrophils. In this study, the direct effects of C-82 on hepatocytes in hepatic inflammation were investigated. Immortalized human hepatocytes were pretreated with inflammatory cytokines. Moreover, the alteration of mRNA and protein expressions of cytokines and chemokines associated with hepatic inflammation and fibrosis, and of mitochondria-related molecules after C-82 treatment were analyzed in this study. The mRNA expression of several proinflammatory and profibrotic chemokines was upregulated by the stimulation of these inflammatory cytokines. In addition, this increase was prevented by C-82. In particular, the protein secretion of CCL2, CCL5, CXCL1, CXCL9, and CXCL10 was noticeably upregulated by TNFα and prevented by additional C-82. Moreover, C-82 increased the VEGF-A and FGF-2 proteins, categorized as anti-inflammatory and antifibrotic molecules, respectively. It also increased the expression of mitochondrial components and mitochondrial membrane potential. In conclusion, C-82 inhibits hepatocyte-mediated proinflammation and fibrogenesis. It also directly activates the mitochondrial function, thus improving liver dysfunction.

Medicinal Chemistry Strategies for the Development of Inhibitors Disrupting β-Catenin's Interactions with Its Nuclear Partners

Dysregulation of the Wnt/β-catenin signaling pathway is strongly associated with various aspects of cancer, including tumor initiation, proliferation, and metastasis as well as antitumor immunity, and presents a promising opportunity for cancer therapy. Wnt/β-catenin signaling activation increases nuclear dephosphorylated β-catenin levels, resulting in β-catenin binding to TCF and additional cotranscription factors, such as BCL9, CBP, and p300. Therefore, directly disrupting β-catenin's interactions with these nuclear partners holds promise for the effective and selective suppression of the aberrant activation of Wnt/β-catenin signaling. Herein, we summarize recent advances in biochemical techniques and medicinal chemistry strategies used to identify potent peptide-based and small-molecule inhibitors that directly disrupt β-catenin's interactions with its nuclear binding partners. We discuss the challenges involved in developing drug-like inhibitors that target the interactions of β-catenin and its nuclear binding partner into therapeutic agents.

Wnt signaling and the regulation of pluripotency

The role of Wnt signaling in stem cells has been mired in seemingly contradictory findings. On one hand, Wnt has been heralded as a self-renewal factor. On the other hand, Wnt's association with differentiation and lineage commitment is indisputable. This apparent contradiction is particularly evident in pluripotent stem cells, where Wnt promotes self-renewal as well as differentiation. To resolve this discrepancy one must delve into fundamental principles of pluripotency and gain an appreciation for the concept of pluripotency states, which exist in a continuum with intermediate metastable states, some of which have been stabilized in vitro. Wnt signaling is a critical regulator of transitions between pluripotent states. Here, we will discuss Wnt's roles in maintaining pluripotency, promoting differentiation, as well as stimulating reprogramming of somatic cells to an induced pluripotent state.

Osteoprogenitor SFRP1 prevents exhaustion of hematopoietic stem cells via PP2A-PR72/130-mediated regulation of p300

Remodeling of the bone marrow microenvironment in chronic inflammation and in aging reduces hematopoietic stem cell (HSC) function. To assess the mechanisms of this functional decline of HSC and find strategies to counteract it, we established a model in which the Sfrp1 gene was deleted in Osterix+ osteolineage cells (OS1Δ/Δ mice). HSC from these mice showed severely diminished repopulating activity with associated DNA damage, enriched expression of the reactive oxygen species pathway and reduced single-cell proliferation. Interestingly, not only was the protein level of Catenin beta-1 (bcatenin) elevated, but so was its association with the phosphorylated co-activator p300 in the nucleus. Since these two proteins play a key role in promotion of differentiation and senescence, we inhibited in vivo phosphorylation of p300 through PP2A-PR72/130 by administration of IQ-1 in OS1Δ/Δ mice. This treatment not only reduced the b-catenin/phosphop300 association, but also decreased nuclear p300. More importantly, in vivo IQ-1 treatment fully restored HSC repopulating activity of the OS1Δ/Δ mice. Our findings show that the osteoprogenitor Sfrp1 is essential for maintaining HSC function. Furthermore, pharmacological downregulation of the nuclear b-catenin/phospho-p300 association is a new strategy to restore poor HSC function.

Targeting β-catenin in acute myeloid leukaemia: past, present, and future perspectives

Acute myeloid leukaemia (AML) is an aggressive disease of the bone marrow with a poor prognosis. Evidence suggests long established chemotherapeutic regimens used to treat AML are reaching the limits of their efficacy, necessitating the urgent development of novel targeted therapies. Canonical Wnt signalling is an evolutionary conserved cascade heavily implicated in normal developmental and disease processes in humans. For over 15 years its been known that the central mediator of this pathway, β-catenin, is dysregulated in AML promoting the emergence, maintenance, and drug resistance of leukaemia stem cells. Yet, despite this knowledge, and subsequent studies demonstrating the therapeutic potential of targeting Wnt activity in haematological cancers, β-catenin inhibitors have not yet reached the clinic. The aim of this review is to summarise the current understanding regarding the role and mechanistic dysregulation of β-catenin in AML, and assess the therapeutic merit of pharmacologically targeting this molecule, drawing on lessons from other disease contexts.

Involvement of activator protein-1 family members in β-catenin and p300 association on the genome of PANC-1 cells

Wnt/β-catenin is believed to regulate different sets of genes with different coactivators, cAMP response element-binding protein (CREB)-binding protein (CBP) or p300. However, the factors that determine which coactivators act on a particular promoter remain elusive. ICG-001 is a specific inhibitor for β-catenin/CBP but not for β-catenin/p300. By taking advantage of the action of ICG-001, we sought to investigate regulatory mechanisms underlying β-catenin coactivator usage in human pancreatic carcinoma PANC-1 cells through combinatorial analysis of chromatin immunoprecipitation-sequencing and RNA-sequencing. CBP and p300 preferentially bound to regions with the TCF motif alone and with both the TCF and AP-1 motifs, respectively. ICG-001 increased β-catenin binding to regions with both the TCF and AP-1 motifs, flanking the genes induced by ICG-001, concomitant with the increments of the p300 and AP-1 component c-JUN binding. Taken together, AP-1 possibly coordinates β-catenin coactivator usage in PANC-1 cells. These results would further our understanding of the canonical Wnt/β-catenin signaling divergence.

Clinical significance of acetylcholinesterase activity in brain tumors

It has been established that the non-neuronal cholinergic system is related to the oncogenesis which increases the attractiveness of its components as the promising markers of oncologic diseases. The purpose of this work is to evaluate the clinical significance of the analysis of the activity of acetyl cholinesterase as a new marker of gliomas. The activity of acetyl cholinesterase was assessed by photo colorimetric analysis according to the Hestrin method recalculating the activity of the enzyme in the tumor tissue per 1 g of protein, and in the blood - by 0.1 g of hemoglobin. The data obtained in the primary tumors of the brain (28) in the tissue of the brain of persons who died as a result of injury (6) and in whole blood of patients with gliomas (28) and practically healthy people (10) were compared with the use of a number of statistical programs. A significant decrease in the activity of acetyl cholinesterase in tumor tissue and in whole blood is revealed as the degree of anaplasia of tumors increases, starting with Grade II. It is for the first time that a significant direct correlation was noted showing the consistency between the decrease in the activity of acetyl cholinesterase in the tumor tissue of the brain and blood. Bioinformatic analysis showed the connection of the enzyme of acetyl cholinesterase with proteins of the PI3K-AKT and Notch signaling pathways providing antiapoptotic and proliferative effects. The found dependences provide new insights into understanding of the mechanisms of gliomas genesis and can be used for selection of new diagnostic markers of brain tumors.

Differential Kat3 Usage Orchestrates the Integration of Cellular Metabolism with Differentiation

Simple Summary

The coupling of metabolism with cellular status is critically important and highly evolutionarily conserved. However, how cells coordinate metabolism with transcription as they change their status is not clear. Utilizing multiomic and functional studies, we now demonstrate the dichotomous roles of the Kat3 coactivators CBP and p300 and, in particular, their extreme N-termini, in coordinating cellular metabolism with cell differentiation. Using multiple in vitro and in vivo systems, our study sheds new light on metabolic regulation in homeostasis and disease, including cancer.

Abstract

The integration of cellular status with metabolism is critically important and the coupling of energy production and cellular function is highly evolutionarily conserved. This has been demonstrated in stem cell biology, organismal, cellular and tissue differentiation and in immune cell biology. However, a molecular mechanism delineating how cells coordinate and couple metabolism with transcription as they navigate quiescence, growth, proliferation, differentiation and migration remains in its infancy. The extreme N-termini of the Kat3 coactivator family members, CBP and p300, by far the least homologous regions with only 66% identity, interact with members of the nuclear receptor family, interferon activated Stat1 and transcriptionally competent β-catenin, a critical component of the Wnt signaling pathway. We now wish to report based on multiomic and functional investigations, utilizing p300 knockdown, N-terminal p300 edited and p300 S89A edited cell lines and p300 S89A knockin mice, that the N-termini of the Kat3 coactivators provide a highly evolutionarily conserved hub to integrate multiple signaling cascades to coordinate cellular metabolism with the regulation of cellular status and function.

Decoding Stem Cells: An Overview on Planarian Stem Cell Heterogeneity and Lineage Progression

Planarians are flatworms capable of whole-body regeneration, able to regrow any missing body part after injury or amputation. The extraordinary regenerative capacity of planarians is based upon the presence in the adult of a large population of somatic pluripotent stem cells. These cells, called neoblasts, offer a unique system to study the process of stem cell specification and differentiation in vivo. In recent years, FACS-based isolation of neoblasts, RNAi functional analyses as well as high-throughput approaches such as single-cell sequencing have allowed a rapid progress in our understanding of many different aspects of neoblast biology. Here, we summarize our current knowledge on the molecular signatures that define planarian neoblasts heterogeneity, which includes a percentage of truly pluripotent stem cells, and guide the commitment of pluripotent neoblasts into lineage-specific progenitor cells, as well as their differentiation into specific planarian cell types.

Taking the road less traveled - the therapeutic potential of CBP/β-catenin antagonists

AREAS COVERED

This perspective discusses the challenges of targeting the Wnt signaling cascade, the safety, efficacy, and therapeutic potential of specific CBP/β-catenin antagonists and a rationale for the pleiotropic effects of CBP/β-catenin antagonists beyond Wnt signaling.

EXPERT OPINION

CBP/β-catenin antagonists can correct lineage infidelity, enhance wound healing, both normal and aberrant (e.g. fibrosis) and force the differentiation and lineage commitment of stem cells and cancer stem cells by regulating enhancer and super-enhancer coactivator occupancy. Small molecule CBP/β-catenin antagonists rebalance the equilibrium between CBP/β-catenin versus p300/β-catenin dependent transcription and may be able to treat or prevent many diseases of aging, via maintenance of our somatic stem cell pool, and regulating mitochondrial function and metabolism involved in differentiation and immune cell function.

Loss of BAF Complex in Developing Cortex Perturbs Radial Neuronal Migration in a WNT Signaling-Dependent Manner

Radial neuronal migration is a key neurodevelopmental event indispensable for proper cortical laminar organization. Cortical neurons mainly use glial fiber guides, cell adhesion dynamics, and cytoskeletal remodeling, among other discrete processes, to radially trek from their birthplace to final layer positions. Dysregulated radial migration can engender cortical mis-lamination, leading to neurodevelopmental disorders. Epigenetic factors, including chromatin remodelers have emerged as formidable regulators of corticogenesis. Notably, the chromatin remodeler BAF complex has been shown to regulate several aspects of cortical histogenesis. Nonetheless, our understanding of how BAF complex regulates neuronal migration is limited. Here, we report that BAF complex is required for neuron migration during cortical development. Ablation of BAF complex in the developing mouse cortex caused alteration in the cortical gene expression program, leading to loss of radial migration-related factors critical for proper cortical layer formation. Of note, BAF complex inactivation in cortex caused defective neuronal polarization resulting in diminished multipolar-to-bipolar transition and eventual disruption of radial migration of cortical neurons. The abnormal radial migration and cortical mis-lamination can be partly rescued by downregulating WNT signaling hyperactivity in the BAF complex mutant cortex. By implication, the BAF complex modulates WNT signaling to establish the gene expression program required for glial fiber-dependent neuronal migration, and cortical lamination. Overall, BAF complex has been identified to be crucial for cortical morphogenesis through instructing multiple aspects of radial neuronal migration in a WNT signaling-dependent manner.

Beta-Catenin Causes Adrenal Hyperplasia by Blocking Zonal Transdifferentiation

Activating mutations in the canonical Wnt/β-catenin pathway are key drivers of hyperplasia, the gateway for tumor development. In a wide range of tissues, this occurs primarily through enhanced effects on cellular proliferation. Whether additional mechanisms contribute to β-catenin-driven hyperplasia remains unknown. The adrenal cortex is an ideal system in which to explore this question, as it undergoes hyperplasia following somatic β-catenin gain-of-function (βcat-GOF) mutations. Targeting βcat-GOF to zona Glomerulosa (zG) cells leads to a progressive hyperplastic expansion in the absence of increased proliferation. Instead, we find that hyperplasia results from a functional block in the ability of zG cells to transdifferentiate into zona Fasciculata (zF) cells. Mechanistically, zG cells demonstrate an upregulation of Pde2a, an inhibitor of zF-specific cAMP/PKA signaling. Hyperplasia is further exacerbated by trophic factor stimulation leading to organomegaly. Together, these data indicate that β-catenin drives adrenal hyperplasia through both proliferation-dependent and -independent mechanisms.

Using the adrenal cortex as a model for slow-cycling tissues, Pignatti et al. show that activation of the canonical Wnt/β-catenin pathway leads to tissue hyperplasia by blocking cellular differentiation/cell-fate commitment, independent of its effects on cellular proliferation.

p300 Serine 89: A Critical Signaling Integrator and Its Effects on Intestinal Homeostasis and Repair

Simple Summary

Given their high degree of identity and even greater similarity at the amino acid level, Kat3 coactivators, CBP (Kat3A) and p300 (Kat3B), have long been considered redundant. We describe the generation of novel p300 S89A knock-in mice carrying a single site directed amino acid mutation in p300, changing the highly evolutionarily conserved serine 89 to alanine, thus enhancing Wnt/CBP/catenin signaling (at the expense of Wnt/p300/catenin signaling). p300 S89A knock-in mice exhibit multiple organ system, immunologic and metabolic differences, compared with their wild type counterparts. In particular, these p300 S89A knock-in mice are highly sensitive to intestinal injury resulting in colitis which is known to significantly predispose to colorectal cancer. Our results highlight the critical role of this region in p300 as a signaling nexus and provide further evidence that p300 and CBP are non-redundant, playing definite and distinctive roles in development and disease.

Abstract

Differential usage of Kat3 coactivators, CBP and p300, by β-catenin is a fundamental regulatory mechanism in stem cell maintenance and initiation of differentiation and repair. Based upon our earlier pharmacologic studies, p300 serine 89 (S89) is critical for controlling differential coactivator usage by β-catenin via post-translational phosphorylation in stem/progenitor populations, and appears to be a target for a number of kinase cascades. To further investigate mechanisms of signal integration effected by this domain, we generated p300 S89A knock-in mice. We show that S89A mice are extremely sensitive to intestinal insult resulting in colitis, which is known to significantly increase the risk of developing colorectal cancer. We demonstrate cell intrinsic differences, and microbiome compositional differences and differential immune responses, in intestine of S89A versus wild type mice. Genomic and proteomic analyses reveal pathway differences, including lipid metabolism, oxidative stress response, mitochondrial function and oxidative phosphorylation. The diverse effects on fundamental processes including epithelial differentiation, metabolism, immune response and microbiome colonization, all brought about by a single amino acid modification S89A, highlights the critical role of this region in p300 as a signaling nexus and the rationale for conservation of this residue and surrounding region for hundreds of million years of vertebrate evolution.

Target Inhibition of CBP Induced Cell Senescence in BCR-ABL- T315I Mutant Chronic Myeloid Leukemia

The treatment of chronic myeloid leukemia (CML) with BCR-ABL tyrosine kinase inhibitors (TKIs), such as imatinib, has yielded clinical success. However, the direct targeting of BCR-ABL does not eradicate CML cells expressing mutant BCR-ABL, especially the T315I mutation in BCR-ABL. Moreover, increasing mutations were identified in BCR-ABL domain, resulting in TKIs resistance recently. It is necessary to find BCR-ABL-independent target for treating CML patients with various mutations, including T315I mutation in BCR-ABL. The dichotomous behavior of CREB binding protein (CBP) and E1A protein (p300), recruited by β-catenin associated with self-renewal and differentiation, have been identified in hematopoietic stem cells, respectively. In this study, CBP was aberrantly expressed in CML cells on the basis of Oncomine dataset. The β-catenin bound with much more CBP than p300 in CML cells. Down-regulation of CBP inhibited cell proliferation capacity and increased the binding of β-catenin to p300, thus promoting cell differentiation and p53-dependent cell senescence in CML cells with either wild type or T315I mutant BCR-ABL in vitro and in vivo models. These demonstrate CBP blockage can be developed for the treatment of CML independent of BCR-ABL mutation status including T315I.

Pharmacologically Targeting the WNT/β-Catenin Signaling Cascade: Avoiding the Sword of Damocles

WNT/β-catenin signaling plays fundamental roles in numerous developmental processes and in adult tissue homeostasis and repair after injury, by controlling cellular self-renewal, activation, division, differentiation, movement, genetic stability, and apoptosis. As such, it comes as no surprise that dysregulation of WNT/β-catenin signaling is associated with various diseases, including cancer, fibrosis, neurodegeneration, etc. Although multiple agents that specifically target the WNT/β-catenin signaling pathway have been studied preclinically and a number have entered clinical trials, none has been approved by the FDA to date. In this chapter, we provide our insights as to the reason(s) it has been so difficult to safely pharmacologically target the WNT/β-catenin signaling pathway and discuss the significant efforts undertaken towards this goal.

Dysregulated Wnt Signalling in the Alzheimer's Brain

The Wnt signalling system is essential for both the developing and adult central nervous system. It regulates numerous cellular functions ranging from neurogenesis to blood brain barrier biology. Dysregulated Wnt signalling can thus have significant consequences for normal brain function, which is becoming increasingly clear in Alzheimer's disease (AD), an age-related neurodegenerative disorder that is the most prevalent form of dementia. AD exhibits a range of pathophysiological manifestations including aberrant amyloid precursor protein processing, tau pathology, synapse loss, neuroinflammation and blood brain barrier breakdown, which have been associated to a greater or lesser degree with abnormal Wnt signalling. Here we provide a comprehensive overview of the role of Wnt signalling in the CNS, and the research that implicates dysregulated Wnt signalling in the ageing brain and in AD pathogenesis. We also discuss the opportunities for therapeutic intervention in AD via modulation of the Wnt signalling pathway, and highlight some of the challenges and the gaps in our current understanding that need to be met to enable that goal.

Klotho is a novel therapeutic target in peritoneal fibrosis via Wnt signaling inhibition

BACKGROUND

Long-term exposure to bioincompatible peritoneal dialysate causes the loss of mesothelial cells and accumulation of matrix proteins, leading to an increase in the thickness of the submesothelial layer, thereby limiting the long-term effectiveness of peritoneal dialysis (PD). However, the detailed molecular mechanisms underlying the process of peritoneal fibrosis have not been clearly elucidated. Wnt/β-catenin signaling pathway activation has been suggested to play a pivotal role in the development of organ fibrosis. Moreover, Klotho protein can regulate Wnt/β-catenin signaling. We examined the role of Klotho protein in reducing peritoneal fibrosis by inhibiting Wnt/β-catenin signaling.

METHODS

The β-catenin-activated transgenic (BAT) driving expression of nuclear β-galactosidase reporter transgenic (BAT-LacZ) mice, the alpha-Klotho gene under control of human elongation factor 1 alpha promoter [Klotho transgenic (KLTG) and C57BL/6 background] and C57BL/6 mice [wild-type (WT)] were used. The mice received daily intraperitoneal (i.p.) injections of 4.25% glucose with lactate (PD solution) or saline as a control for 4 weeks. Other mice received daily i.p. injections of the same volume of saline (normal control).

RESULTS

After exposure to PD, Wnt signal activation was observed on the peritoneal mesothelial cells in WT-PD mice. The peritoneal fibrosis was also accelerated in WT-PD mice. The protein expression of β-catenin and Wnt-inducible genes were also remarkably increased in WT-PD mice. On the other hand, KLTG-PD mice attenuated activation of Wnt/β-catenin signaling after exposure to PD and ameliorated the progression of peritoneal fibrosis.

CONCLUSIONS

Overexpression of Klotho protein protects the peritoneal membrane through attenuation of the Wnt/β-catenin signaling pathway. The availability of recombinant Klotho protein would provide a novel potential therapeutic target in peritoneal fibrosis.

Targeting the CBP/β-Catenin Interaction to Suppress Activation of Cancer-Promoting Pancreatic Stellate Cells

Background: Although cyclic AMP-response element binding protein-binding protein (CBP)/β-catenin signaling is known to promote proliferation and fibrosis in various organ systems, its role in the activation of pancreatic stellate cells (PSCs), the key effector cells of desmoplasia in pancreatic cancer and fibrosis in chronic pancreatitis, is largely unknown. Methods: To investigate the role of the CBP/β-catenin signaling pathway in the activation of PSCs, we have treated mouse and human PSCs with the small molecule specific CBP/β-catenin antagonist ICG-001 and examined the effects of treatment on parameters of activation. Results: We report for the first time that CBP/β-catenin antagonism suppresses activation of PSCs as evidenced by their decreased proliferation, down-regulation of “activation” markers, e.g., α-smooth muscle actin (α-SMA/Acta2), collagen type I alpha 1 (Col1a1), Prolyl 4-hydroxylase, and Survivin, up-regulation of peroxisome proliferator activated receptor gamma (Ppar-γ) which is associated with quiescence, and reduced migration; additionally, CBP/β-catenin antagonism also suppresses PSC-induced migration of cancer cells. Conclusion: CBP/β-catenin antagonism represents a novel therapeutic strategy for suppressing PSC activation and may be effective at countering PSC promotion of pancreatic cancer.

Convergence of Canonical and Non-Canonical Wnt Signal: Differential Kat3 Coactivator Usage

BACKGROUND

The ancient and highly evolutionarily conserved Wnt signaling pathway is critical in nearly all tissues and organs for an organism to develop normally from embryo through adult. Wnt signaling is generally parsed into "canonical" or Wnt-β-catenin-dependent or "non-canonical" β-catenin-independent signaling. Even though designating Wnt signaling as either canonical or noncanonical allows for easier conceptual discourse about this signaling pathway, in fact canonical and non-canonical Wnt crosstalk regulates complex nonlinear networks.

OBJECTIVE

In this perspective, we discuss the integration of canonical and non-canonical Wnt signaling via differential Kat3 (CBP and p300) coactivator usage, thereby regulating and coordinating gene expression programs associated with both proliferation and cellular differentiation and morphogenesis.

METHODS

Pharmacologic inhibitors, cell culture, real-time PCR, chromatin immunoprecipitation, protein immunoprecipitation, Western blotting, reporter-luciferase, protein purification, site-directed mutagenesis, in vitro phosphorylation and binding assays, and immunofluorescence were utilized.

CONCLUSION

Coordinated integration between both canonical and non-canonical Wnt pathways appears to be crucial not only in the control of fundamental morphologic processes but also in the regulation of normal as well as pathologic events. Such integration between both canonical and non-canonical Wnt signaling is presumably effected via reversible phosphorylation mechanism (e.g., protein kinase C) to regulate differential β -catenin/Kat3 coactivator usage in order to coordinate proliferation with differentiation and adhesion.

Hypothesis: Retinoblastoma protein inactivation mediates effects of histone deacetylase inhibitor-induced Wnt hyperactivation in colorectal cancer cells

Butyrate, a product of dietary fiber and a histone deacetylase inhibitor, induces apoptosis of colorectal cancer cells; this effect of butyrate is in part mediated by its ability to hyperactivate Wnt signaling, and may in part explain the preventive action of dietary fiber against colorectal cancer. However, the mechanisms by which Wnt hyperactivation promotes apoptosis are unknown. Inactivation of the retinoblastoma tumor suppressor occurs in some cancers and can lead to context-dependent cell proliferation or cell death/apoptosis. The function of retinoblastoma protein (Rb) in normal cells is modulation of cell cycle; inactivation of Rb allows for cell cycle progression and, hence, cell proliferation. Wnt signaling is upregulated in a variety of cancers, and deregulated Wnt signaling is a key initiating event in most cases of sporadic colorectal cancer. It has been shown that Wnt signaling activated by APC inactivation can synergize with the inactivation of Rb to induce apoptosis in a manner mediated by increased TORC1 activity, leading to induced metabolic and energy stress. Rb is typically not inactivated in colorectal cancer; however, Rb is phosphorylated and deactivated during cell cycle G1/S transition. This manuscript posits that it is during this time that butyrate/histone deacetylase inhibitor-induced Wnt hyperactivation induces apoptosis in colorectal cancer cells. Thus, the inactivation of Rb in cell cycle progression may synergize with Wnt hyperactivation to induce apoptosis in response to histone deacetylase inhibitors. The hypothesis is that hyperactivation of Wnt signaling enhances colorectal cancer cell apoptosis via the interaction between upregulated Wnt signaling and inactivated Rb during cell cycle progression. This paper discusses this hypothesis and offers initial experimental approaches for testing the hypothesis. A better understanding of how histone deacetylase inhibitors induce colorectal cancer cell apoptosis through hyperactivation of Wnt signaling, and of cross-talk between repression of cell cycle and induction of apoptosis that occurs with treatment with histone deacetylase inhibitors, can assist in the development of novel therapies for colorectal cancer.

The prognostic capacities of CBP and p300 in locally advanced rectal cancer

Background

CREB-binding protein (CBP) and p300 represent histone acetyltransferases (HATs) and transcriptional coactivators that play essential roles in tumour initiation and progression. Both proteins are generally thought to function as tumour suppressors, although their distinct roles in colorectal cancer (CRC) remain inconsistent and ambiguous.

Thus, we analysed the expression of these two HATs in human tissue samples from patients with locally advanced rectal cancer via immunohistochemistry and evaluated their potential impacts on future CRC diagnosis and treatment.

Methods

In our analysis, we included ninety-three (n = 93) patients diagnosed with adenocarcinoma in the upper third of the rectum. None of the patients received preoperative chemoradiotherapy, but the patients did undergo primary resection of the tumour within the phase II GAST-05 trial. By using H-scores, the expression of both proteins was visualised via immunohistochemistry in resected specimens from the patients. CBP and p300 expression were correlated with clinical and follow-up data.

Results

Our analysis showed that high expression of CBP was significantly associated with prolonged cancer-specific survival (CSS; p = 0.002). In univariate analysis, CBP was an independent prognostic parameter for CSS (p = 0.042). High nuclear CBP expression was observed in two-thirds of patients. In contrast, we could not find any significant correlation between the expression of p300 and cancer-specific survival in this cohort of patients (p = 0.09). We did not observe any cooperation between CBP and p300 in our analysis.

Conclusions

High expression of CBP was significantly associated with improved oncological outcomes. This finding could help to stratify patients in the future for CRC treatment. Histone deacetylase (HDAC) inhibitors are increasingly playing a role in oncological treatment and could additionally become therapeutic options in CRC. Our findings need to be further evaluated and verified in future clinical analyses.

Restoring Wnt/β-catenin signaling is a promising therapeutic strategy for Alzheimer's disease

Alzheimer’s disease (AD) is an aging-related neurological disorder characterized by synaptic loss and dementia. Wnt/β-catenin signaling is an essential signal transduction pathway that regulates numerous cellular processes including cell survival. In brain, Wnt/β-catenin signaling is not only crucial for neuronal survival and neurogenesis, but it plays important roles in regulating synaptic plasticity and blood-brain barrier integrity and function. Moreover, activation of Wnt/β-catenin signaling inhibits amyloid-β production and tau protein hyperphosphorylation in the brain. Critically, Wnt/β-catenin signaling is greatly suppressed in AD brain via multiple pathogenic mechanisms. As such, restoring Wnt/β-catenin signaling represents a unique opportunity for the rational design of novel AD therapies.

PTEN in Autism and Neurodevelopmental Disorders

Phosphatase and tensin homolog (PTEN) is a classical tumor suppressor that antagonizes phosphatidylinositol 3-phosphate kinase (PI3K)/AKT signaling. Although there is a strong association of PTEN germline mutations with cancer syndromes, they have also been described in a subset of patients with autism spectrum disorders with macrocephaly characterized by impairments in social interactions and communication, repetitive behavior and, occasionally, epilepsy. To investigate PTEN's role during neurodevelopment and its implication for autism, several conditional Pten knockout mouse models have been generated. These models are valuable tools to understand PTEN's spatiotemporal roles during neurodevelopment. In this review, we will highlight the anatomical and phenotypic results from animal studies and link them to cellular and molecular findings.

Enhanced Kat3A/Catenin transcription: a common mechanism of therapeutic resistance

Cancers are heterogeneous at the cellular level. Cancer stem cells/tumor initiating cells (CSC/TIC) both initiate tumorigenesis and are responsible for therapeutic resistance and disease relapse. Elimination of CSC/TIC should therefore be able to reverse therapy resistance. In principle, this could be accomplished by either targeting cancer stem cell surface markers or "stemness" pathways. Although the successful therapeutic elimination of "cancer stemness" is a critical goal, it is complex in that it should be achieved without depletion of or increases in somatic mutations in normal tissue stem cell populations. In this perspective, we will discuss the prospects for this goal via pharmacologically targeting differential Kat3 coactivator/Catenin usage, a fundamental transcriptional control mechanism in stem cell biology.

The Mode of Stem Cell Division Is Dependent on the Differential Interaction of β-Catenin with the Kat3 Coactivators CBP or p300

Normal long-term repopulating somatic stem cells (SSCs) preferentially divide asymmetrically, with one daughter cell remaining in the niche and the other going on to be a transient amplifying cell required for generating new tissue in homeostatic maintenance and repair processes, whereas cancer stem cells (CSCs) favor symmetric divisions. We have previously proposed that differential β-catenin modulation of transcriptional activity via selective interaction with either the Kat3 coactivator CBP or its closely related paralog p300, regulates symmetric versus asymmetric division in SSCs and CSCs. We have previously demonstrated that SSCs that divide asymmetrically per force retain one of the dividing daughter cells in the stem cell niche, even when treated with specific CBP/β-catenin antagonists, whereas CSCs can be removed from their niche via forced stochastic symmetric differentiative divisions. We now demonstrate that loss of p73 in early corticogenesis biases β-catenin Kat3 coactivator usage and enhances β-catenin/CBP transcription at the expense of β-catenin/p300 transcription. Biased β-catenin coactivator usage has dramatic consequences on the mode of division of neural stem cells (NSCs), but not neurogenic progenitors. The observed increase in symmetric divisions due to enhanced β-catenin/CBP interaction and transcription leads to an immediate increase in NSC symmetric differentiative divisions. Moreover, we demonstrate for the first time that the complex phenotype caused by the loss of p73 can be rescued in utero by treatment with the small-molecule-specific CBP/β-catenin antagonist ICG-001. Taken together, our results demonstrate the causal relationship between the choice of β-catenin Kat3 coactivator and the mode of stem cell division.

Protein complexes associated with β-catenin differentially influence the differentiation profile of neonatal and adult CD8+ T cells

The canonical Wnt signaling pathway is a master cell regulator involved in CD8⁺ T cell proliferation and differentiation. In human CD8⁺ T cells, this pathway induces differentiation into memory cells or a "stem cell memory like" population, which is preferentially present in cord blood. To better understand the role of canonical Wnt signals in neonatal or adult blood, we compared the proteins associated with β-catenin, in nonstimulated and Wnt3a-stimulated human neonatal and adult naive CD8⁺ T cells. Differentially recruited proteins established different complexes in adult and neonatal cells. In the former, β-catenin-associated proteins were linked to cell signaling and immunological functions, whereas those of neonates were linked to proliferation and metabolism. Wnt3a stimulation led to the recruitment and overexpression of Wnt11 in adult cells and Wnt5a in neonatal cells, suggesting a differential connexion with planar polarity and Wnt/Ca²⁺ noncanonical pathways, respectively. The chromatin immunoprecipitation polymerase chain reaction β-catenin was recruited to a higher level on the promoters of cell renewal genes in neonatal cells and of differentiation genes in those of adults. We found a preferential association of β-catenin with CBP in neonatal cells and with p300 in the adult samples, which could be involved in a higher self-renewal capacity of the neonatal cells and memory commitment in those of adults. Altogether, our results show that different proteins associated with β-catenin during Wnt3a activation mediate a differential response of neonatal and adult human CD8⁺ T cells.

The Dietary Flavonoid, Luteolin, Negatively Affects Neuronal Differentiation

Luteolin, a polyphenolic plant flavonoid, has been attributed with numerous beneficial properties like anti-cancer, antioxidant, and anti-inflammatory action. Luteolin has been reported earlier to be neuroprotective in models of spinal cord injury and traumatic brain injury and also induces neurite outgrowth in PC12 cells. However, the effect of luteolin on early differentiation, which might be important for its beneficial effects, is unknown. In this report, we show that luteolin negatively affects early differentiation of embryonic stem cells, hampering the formation of embryoid bodies. At later stages of differentiation, luteolin specifically inhibits neuronal differentiation, where the expression of early neuronal markers is suppressed, whereas luteolin treatment does not inhibit expression of meso- and endodermal markers. Further, in a developing zebrafish model, luteolin treatment leads to fewer numbers of mitotic cells in the brain. These specific effects of luteolin on neuronal differentiation could possibly be due to its ability to inhibit the lysine acetyltransferase, p300, since the structurally closely related p300 non-inhibitor flavonoid, apigenin, does not inhibit neuronal differentiation. These results show that luteolin perturbs neuronal differentiation of embryonic stem cells.

Regulation of Human Airway Epithelial Tissue Stem Cell Differentiation by β-Catenin, P300, and CBP

The wingless/integrase-1 (WNT)/β-catenin signaling pathway is active in several chronic lung diseases including idiopathic pulmonary fibrosis, asthma, and chronic obstructive pulmonary disease. Although this WNT/β-catenin pathway activity is associated with an increase in mucus cell frequency and a decrease in ciliated cell frequency, a cause and consequence relationship between signaling and cell frequency has not been established. We previously demonstrated that genetic stabilization of β-catenin inhibited differentiation of mouse bronchiolar tissue stem cells (TSC). This study determined the effect of β-catenin and its co-factors P300 (E1A-binding protein, 300 kDa) and cAMP response element binding (CREB)-binding protein (CBP) on human bronchial epithelial TSC differentiation to mucus and ciliated cells. We developed a modified air-liquid interface (ALI) culture system in which mucus and ciliated cell frequency is similar. These cultures were treated with the β-catenin agonist CHIR99021 (CHIR) and antagonists to β-catenin (XAV939), P300 (IQ1), and CBP (ICG001). We report that human TSC differentiation to mucus and ciliated cells can be divided into two stages, specification and commitment. CHIR treatment inhibited mucus and ciliated cell commitment while XAV939 treatment demonstrated that β-catenin was necessary for mucus and ciliated cell specification. Additional studies demonstrate that a β-catenin/P300 complex promotes mucus cell specification and that β-catenin interacts with either P300 or CBP to inhibit ciliated cell commitment. These data indicate that activation of β-catenin-dependent signaling in chronic lung disease leads to changes in mucus and ciliated cell frequency and that P300 and CBP tune the β-catenin signal to favor mucus cell differentiation. Stem Cells 2018;36:1905-12.

The role of acetyltransferases for the temporal-specific accessibility of β-catenin to the myogenic gene locus

Molecules involved in WNT/β-catenin signaling show spatiotemporal-specific expression and play vital roles in muscle development. Our previous study showed that WNT/β-catenin signaling promotes myoblast proliferation and differentiation through the regulation of the cyclin A2 (Ccna2)/cell division cycle 25C (Cdc25c) and Fermitin family homolog 2 (Fermt2) genes, respectively. However, it remains unclear how β-catenin targets different genes from stage to stage during myogenesis. Here, we show that the accessibility of β-catenin to the promoter region of its target genes is regulated by developmental stage-specific histone acetyltransferases (HATs), lysine acetyltransferase 2B (KAT2B), and cAMP-response element-binding protein (CREB)-binding protein (CBP). We found that KAT2B was specifically expressed at the myoblast proliferation stage and formed a complex with β-catenin to induce Ccna2/Cdc25c expression. On the other hand, CBP was specifically expressed during myoblast differentiation and formed a complex with β-catenin to induce Fermt2 expression. Our findings indicate that β-catenin efficiently accesses to its target gene’s promoters by forming a complex with developmental stage-specific acetyltransferases during myogenesis.

Expression and Manipulation of the APC-β-Catenin Pathway During Peripheral Neuron Regeneration

Molecules and pathways that suppress growth are expressed in postmitotic neurons, a potential advantage in mature neural networks, but a liability during regeneration. In this work, we probed the APC (adenomatous polyposis coli)-β-catenin partner pathway in adult peripheral sensory neurons during regeneration. APC had robust expression in the cytoplasm and perinuclear region of adult DRG sensory neurons both before and after axotomy injury. β-catenin was expressed in neuronal nuclei, neuronal cytoplasm and also in perineuronal satellite cells. In injured dorsal root ganglia (DRG) sensory neurons and their axons, we observed paradoxical APC upregulation, despite its role as an inhibitor of growth whereas β-catenin was downregulated. Inhibition of APC in adult sensory neurons and activation of β-catenin, LEF/TCF transcriptional factors were associated with increased neuronal plasticity in vitro. Local knockdown of APC, at the site of sciatic nerve crush injury enhanced evidence for electrophysiological, behavioural and structural regeneration in vivo. This was accompanied by upregulation of β-catenin. Collectively, the APC-β-catenin-LEF/TCF transcriptional pathway impacts intrinsic mechanisms of axonal regeneration and neuronal plasticity after injury, offering new options for addressing axon regeneration.

Effect of inhibition of CBP-coactivated β-catenin-mediated Wnt signalling in uremic rats with vascular calcifications

Uremic vascular calcification is a regulated cell-mediated process wherein cells in the arterial wall transdifferentiate to actively calcifying cells resulting in a process resembling bone formation. Wnt signalling is established as a major driver for vessel formation and maturation and for embryonic bone formation, and disturbed Wnt signalling might play a role in vascular calcification. ICG-001 is a small molecule Wnt inhibitor that specifically targets the coactivator CREB binding protein (CBP)/β-catenin-mediated signalling. In the present investigation we examined the effect of ICG-001 on vascular calcification in uremic rats. Uremic vascular calcification was induced in adult male rats by 5/6-nephrectomy, high phosphate diet and alfacalcidol. The presence of uremic vascular calcification in the aorta was associated with induction of gene expression of the Wnt target gene and marker of proliferation, cyclinD1; the mediator of canonical Wnt signalling, β-catenin and the matricellular proteins, fibronectin and periostin. Furthermore, genes from fibrosis-related pathways, TGF-β and activin A, as well as factors related to epithelial-mesenchymal transition, snail1 and vimentin were induced. ICG-001 treatment had significant effects on gene expression in kidney and aorta from healthy rats. These effects were however limited in uremic rats, and treatment with ICG-001 did not reduce the Ca-content of the uremic vasculature.

Wnt/β-Catenin Signaling and Obesity

Obesity has become epidemic worldwide, which triggers several obesity-associated complications. Obesity is characterized by excess fat storage mainly in the visceral white adipose tissue (vWAT), subcutaneous WAT (sWAT), and other tissues. Myriad studies have demonstrated the crucial role of canonical Wnt/β-catenin cascade in the development of organs and physiological homeostasis, whereas recent studies show that genetic variations/mutations in the Wnt/β-catenin pathway are associated with human metabolic diseases. In this review, we highlight the regulation of updated Wnt/β-catenin signaling in obesity, especially the distinctly depot-specific roles between subcutaneous and visceral adipose tissue under high-fed diet stimulation and WAT browning process.

Modulating the masters: chemical tools to dissect CBP and p300 function

Dysregulation of transcription is found in nearly every human disease, and as a result there has been intense interest in developing new therapeutics that target regulators of transcription. CREB binding protein (CBP) and its paralogue p300 are attractive targets due to their function as `master coactivators'. Although inhibitors of several CBP/p300 domains have been identified, the selectivity of many of these compounds has remained underexplored. Here, we review recent successes in the development of chemical tools targeting several CBP/p300 domains with selectivity acceptable for use as chemical probes. Additionally, we highlight recent studies which have used these probes to expand our understanding of interdomain interactions and differential coactivator usage.

Differentiation Therapy Targeting the β-Catenin/CBP Interaction in Pancreatic Cancer

Background: Although canonical Wnt signaling is known to promote tumorigenesis in pancreatic ductal adenocarcinoma (PDAC), a cancer driven principally by mutant K-Ras, the detailed molecular mechanisms by which the Wnt effector β-catenin regulates such tumorigenesis are largely unknown. We have previously demonstrated that β-catenin’s differential usage of the Kat3 transcriptional coactivator cyclic AMP-response element binding protein-binding protein (CBP) over its highly homologous coactivator p300 increases self-renewal and suppresses differentiation in other types of cancer. Aim/methods: To investigate Wnt-mediated carcinogenesis in PDAC, we have used the specific small molecule CBP/β-catenin antagonist, ICG-001, which our lab identified and has extensively characterized, to examine its effects in human pancreatic cancer cells and in both an orthotopic mouse model and a human patient-derived xenograft (PDX) model of PDAC. Results/conclusion: We report for the first time that K-Ras activation increases the CBP/β-catenin interaction in pancreatic cancer; and that ICG-001 specific antagonism of the CBP/β-catenin interaction sensitizes pancreatic cancer cells and tumors to gemcitabine treatment. These effects were associated with increases in the expression of let-7a microRNA; suppression of K-Ras and survivin; and the elimination of drug-resistant cancer stem/tumor-initiating cells.

The β-catenin/CBP-antagonist ICG-001 inhibits pediatric glioma tumorigenicity in a Wnt-independent manner

Pediatric high-grade gliomas (pedHGG) belong to the most aggressive cancers in children with a poor prognosis due to a lack of efficient therapeutic strategies. The β-catenin/Wnt-signaling pathway was shown to hold promising potential as a treatment target in adult high-grade gliomas by abrogating tumor cell invasion and the acquisition of stem cell-like characteristics. Since pedHGG differ from their adult counterparts in genetically and biologically we aimed to investigate the effects of β-catenin/Wnt-signaling pathway-inhibition by the β-catenin/CBP antagonist ICG-001 in pedHGG cell lines. In contrast to adult HGG, pedHGG cells displayed minimal detectable canonical Wnt-signaling activity. Nevertheless, low doses of ICG-001 inhibited cell migration/invasion, tumorsphere- and colony formation, proliferation in vitro as well as tumor growth in vivo/ovo, suggesting that ICG-001 affects pedHGG tumor cell characteristics independent of β-catenin/Wnt-signaling. RNA-sequencing analyses support a Wnt/β-catenin-independent effect of ICG-001 on target gene transcription, revealing strong effects on genes involved in cellular metabolic/biosynthetic processes and cell cycle progression. Among these, high mRNA expression of cell cycle regulator JDP2 was found to confer a better prognosis for pedHGG patients. In conclusion, ICG-001 might offer an effective treatment option for pedHGG patients functioning to regulate cell phenotype and gene expression programs in absence of Wnt/β-catenin signaling-activity.

Design, Synthesis, and Evaluation of Orally Bioavailable Quinoline-Indole Derivatives as Innovative Multitarget-Directed Ligands: Promotion of Cell Proliferation in the Adult Murine Hippocampus for the Treatment of Alzheimer's Disease

A novel series of quinoline-indole derivatives were synthesized and evaluated as multitarget-directed ligands for the treatment of Alzheimer's disease (AD). Biological evaluation revealed that the derivatives had multifunctional profiles including antioxidant effects, blood-brain barrier (BBB) penetration, biometal chelation, Aβ aggregation modulation, neurotrophic and neuroprotective properties. Moreover, several representative target derivatives demonstrated hippocampal cell proliferation in living adult mice by intracerebroventricular (icv) injection or oral administration. Further drug-like property analysis demonstrated that the optimized compound, 8d (WI-1758), had liver microsomal metabolic stability, was well tolerated (>2000 mg/kg), and had a rational pharmacokinetic profile, as well as an oral bioavailability of 14.1% and a positive log BB (-0.19) to cross the BBB in vivo. Pharmacodynamics studies demonstrated that chronic oral administration of 8d·HCl substantially ameliorated the cognitive and spatial memory deficits in APP/PS1 AD mice and noticeably reduced overall cerebral β-amyloid deposits.

Re-education begins at home: an overview of the discovery of in vivo-active small molecule modulators of endogenous stem cells

INTRODUCTION

Degenerative diseases, such as Alzheimer's disease, heart disease and arthritis cause great suffering and are major socioeconomic burdens. An attractive treatment approach is stem cell transplantation to regenerate damaged or destroyed tissues. However, this can be problematic. For example, donor cells may not functionally integrate into the host tissue. An alternative methodology is to deliver bioactive agents, such as small molecules, directly into the diseased tissue to enhance the regenerative potential of endogenous stem cells. Areas covered: In this review, the authors discuss the necessity of developing these small molecules to treat degenerative diseases and survey progress in their application as therapeutics. They describe both the successes and caveats of developing small molecules that target endogenous stem cells to induce tissue regeneration. This article is based on literature searches which encompass databases for biomedical research and clinical trials. These small molecules are also categorized per their target disease and mechanism of action. Expert opinion: The development of small molecules targeting endogenous stem cells is a high-profile research area. Some compounds have made the successful transition to the clinic. Novel approaches, such as modulating the stem cell niche or targeted delivery to disease sites, should increase the likelihood of future successes in this field.

Wnt Signaling in Stem Cells and Cancer Stem Cells: A Tale of Two Coactivators

Wnt signaling in stem cells plays critical roles in development, normal adult physiology, and disease. In this chapter, we focus on the role of the Wnt signaling pathway in somatic stem cell biology and its critical role in normal tissue homeostasis and cancer. Wnt signaling can both maintain potency and initiate differentiation in somatic stem cells, depending on the cellular and environmental context. Based principally on studies from our lab, we will explain the dichotomous behavior of this signaling pathway in determining stem cell fate decisions, placing special emphasis on the interaction of β-catenin with either of the two highly homologous Kat3 coactivator proteins, CBP and p300. We will also discuss our results, both preclinical and clinical, demonstrating that small molecule modulators of the β-catenin/Kat3 coactivator interaction can be safely utilized to shift the balance between maintenance of potency and initiation of differentiation.

Insufficient microwave ablation-induced promotion of distant metastasis is suppressed by β-catenin pathway inhibition in breast cancer

Microwave ablation (MWA), a thermal ablation, is an effective treatment for breast cancer. However, residual breast cancer is still detected. The biological characteristics of residual breast cancer after thermal ablation remain unknown. To mimic insufficient MWA in vitro, breast cancer cells were treated at 37°C, 42°C, 45°C, 47°C and 50°C for 10 mins, the 37°C as control group. Insufficient MWA induced EMT-like changes of residual breast cancer by down-regulation of E-cadherin and up-regulation of vimentin and N-cadherin in vitro and in vivo. For the first time, we reported insufficient MWA promoted distant metastasis of residual breast cancer in vivo. Reduced β-catenin expression by siRNA diminished the EMT-like phenotype and enhanced migration capability induced by heat treatment in breast cancer cells. Moreover, ICG001, a special inhibitor of β-catenin pathway, depressed EMT of residual tumor and distant metastasis in an insufficient MWA nude mice model of breast cancer. In conclusion, our results demonstrate that insufficient MWA promotes EMT of residual breast cancer by activating β-catenin signal pathway, resulting in enhanced distant metastasis of residual breast cancer. In addition, the effectiveness of ICG001 in suppressing enhanced metastasis of residual breast cancer is preliminarily validated.

CBP/Catenin antagonists: Targeting LSCs' Achilles heel

Cancer stem cells (CSCs), including leukemia stem cells (LSCs), exhibit self-renewal capacity and differentiation potential and have the capacity to maintain or renew and propagate a tumor/leukemia. The initial isolation of CSCs/LSCs was in adult myelogenous leukemia, although more recently, the existence of CSCs in a wide variety of other cancers has been reported. CSCs, in general, and LSCs, specifically with respect to this review, are responsible for initiation of disease, therapeutic resistance and ultimately disease relapse. One key focus in cancer research over the past decade has been the development of therapies that safely eliminate the LSC/CSC population. One major obstacle to this goal is the identification of key mechanisms that distinguish LSCs from normal endogenous hematopoietic stem cells. An additional daunting feature that has recently come to light with advances in next-generation sequencing and single-cell sequencing is the heterogeneity within leukemias/tumors, with multiple combinations of mutations, gain and loss of function of genes, and so on being capable of driving disease, even within the CSC/LSC population. The focus of this review/perspective is on our work in identifying and validating, in both chronic myelogenous leukemia and acute lymphoblastic leukemia, a safe and efficacious mechanism to target an evolutionarily conserved signaling nexus, which constitutes a common "Achilles heel" for LSCs/CSCs, using small molecule-specific CBP/catenin antagonists.

ZEB1 Mediates Drug Resistance and EMT in p300-Deficient CRC

We discuss the hypothesis that ZEB1-Wnt-p300 signaling integrates epithelial to mesenchymal transition (EMT) and resistance to histone deacetylase inhibitors (HDACis) in colorectal cancer (CRC) cells. The HDACi butyrate, derived from dietary fiber, has been linked to CRC prevention, and other HDACis have been proposed as therapeutic agents against CRC. We have previously discussed that resistance to butyrate likely contributes to colonic carcinogenesis, and we have demonstrated that butyrate resistance leads to cross-resistance to cancer therapeutic HDACis. Deregulated Wnt signaling is the major initiating event in most CRC cases. One mechanism whereby butyrate and other HDACis exert their anti-CRC effects is via Wnt signaling hyperactivation, which promotes CRC cell apoptosis. The histone acetylases (HATs) CBP and p300 are mediators of Wnt transcriptional activity, and play divergent roles in the downstream consequences of Wnt signaling. CBP-mediated Wnt signaling is associated with cell proliferation and stem cell maintenance; whereas, p300-mediated Wnt activity is associated with differentiation. We have found that CBP and p300 differentially affect the ability of butyrate to influence Wnt signaling, apoptosis, and proliferation. ZEB1 is a Wnt signaling-targeted gene, whose product is a transcription factor expressed at the invasive front of carcinomas where it promotes malignant progression and EMT. ZEB1 is typically a transcriptional repressor; however, when associated with p300, ZEB1 enhances transcription. These changes in ZEB1 activity likely affect the cancer cell phenotype. ZEB1 has been shown to promote resistance to chemotherapeutic agents, and expression of ZEB1 is upregulated in butyrate-resistant CRC cells that lack p300 expression. Since the expression of ZEB1 correlates with poor outcomes in cancer, ZEB represents a relevant therapeutic target. Here we propose that targeting the signaling network established by ZEB1, Wnt signaling, and p300 signaling can reverse HDACi resistance and inhibit EMT.