Casein kinase 1: a Wnt'er of disconnect

CK1α deficiency impairs mouse uterine adenogenesis by inducing epithelial cell apoptosis through GSK3β pathway and inhibiting Foxa2 expression through p53 pathway†

Uterine glands and their secretions are crucial for conceptus survival and implantation in rodents and humans. In mice, the development of uterine gland known as adenogenesis occurs after birth, whereas the adenogenesis in humans initiates from fetal life and completed at puberty. Uterine adenogenesis involves dynamic epithelial cell proliferation, differentiation, and apoptosis. However, it is largely unexplored about the mechanisms governing adenogenesis. CK1α plays important roles in regulating cell division, differentiation, and death, but it is unknown whether CK1α affects adenogenesis. In the current study, uterus-specific CK1α knockout female mice (Csnk1a1d/d) were infertile resulted from lack of uterine glands. Subsequent analysis revealed that CK1α deletion induced massive apoptosis in uterine epithelium by activating GSK3β, which was confirmed by injections of GSK3β inhibitor SB216763 to Csnk1a1d/d females, and the co-treatment of SB216763 and CK1 inhibitor d4476 on cultured epithelial cells. Another important finding was that our results revealed CK1α deficiency activated p53, which then blocked the expression of Foxa2, an important factor for glandular epithelium development and function. This was confirmed by that Foxa2 expression level was elevated in p53 inhibitor pifithrin-α injected Csnk1a1d/d mouse uterus and in vitro dual-luciferase reporter assay between p53 and Foxa2. Collectively, these studies reveal that CK1α is a novel factor regulating uterine adenogenesis by inhibiting epithelial cell apoptosis through GSK3β pathway and regulating Foxa2 expression through p53 pathway. Uncovering the mechanisms of uterine adenogenesis is expected to improve pregnancy success in humans and other mammals.

SNTB1 regulates colorectal cancer cell proliferation and metastasis through YAP1 and the WNT/β-catenin pathway

Colorectal cancer is a common type of digestive tract cancer with a significant morbidity and death rate across the world, partially attributing to the metastasis-associated problems. In this study, integrative bioinformatics analyses were performed to identify genes that might contribute to colorectal cancer metastasis, and 293 genes were dramatically increased and 369 genes were decreased within colon cancer samples. Among up-regulated genes, top five genes correlated with colorectal cancer patient's prognosis were verified for expression in clinical samples and syntrophin beta 1 (SNTB1) was the most up-regulated. In vitro, SNTB1 knockdown suppresses the malignant behaviors of colorectal cancer cells, including cell viability, colony formation capacity, as well as the abilities to migrate and invade. Furthermore, SNTB1 knockdown decreased the levels of Wnt1, C-Jun, C-Myc, TCF7, and cyclin D1, and inhibited EMT in both cell lines. In vivo, SNTB1 knockdown inhibited tumor growth and metastasis in nude mice models. SNTB1 positively regulated Yes1 associated transcriptional regulator (YAP1) expression; YAP1 partially reversed the effects of SNTB1 on colorectal cancer cell phenotypes and the Wnt/β-catenin/MYC signaling. In conclusion, SNTB1 knockdown inhibits colorectal cancer cell aggressiveness in vitro and tumor growth and metastasis in vivo through the Wnt/β-catenin/MYC signaling; YAP1 might mediate SNTB1 functions on colorectal cancer.

Interplay between Signaling Pathways and Tumor Microenvironment Components: A Paradoxical Role in Colorectal Cancer

The study of the tumor microenvironment (TME) has become an important part of colorectal cancer (CRC) research. Indeed, it is now accepted that the invasive character of a primary CRC is determined not only by the genotype of the tumor cells, but also by their interactions with the extracellular environment, which thereby orchestrates the development of the tumor. In fact, the TME cells are a double-edged sword as they play both pro- and anti-tumor roles. The interaction of the tumor-infiltrating cells (TIC) with the cancer cells induces the polarization of the TIC, exhibiting an antagonist phenotype. This polarization is controlled by a plethora of interconnected pro- and anti-oncogenic signaling pathways. The complexity of this interaction and the dual function of these different actors contribute to the failure of CRC control. Thus, a better understanding of such mechanisms is of great interest and provides new opportunities for the development of personalized and efficient therapies for CRC. In this review, we summarize the signaling pathways linked to CRC and their implication in the development or inhibition of the tumor initiation and progression. In the second part, we enlist the major components of the TME and discuss the complexity of their cells functions.

Clinicopathologic and molecular spectrum of testicular sex cord-stromal tumors not amenable to specific histopathologic subclassification

A subset of testicular sex cord-stromal tumors (SCST), which includes neoplasms with mixed histology, cannot be classified into a specific histologic subtype. This study evaluated the clinicopathologic, immunophenotypic and molecular features of 26 SCST not amenable to specific classification by expert uropathologists. Median age at diagnosis was 43 years and median tumor size was 2.4 cm. Follow-up information was available for 18 (69%) patients, with evidence of an aggressive clinical course in 6 patients (4 alive with disease, 2 dead of disease 3 months and 6 months after orchiectomy). Microscopically, SCST not amenable to specific classification demonstrated monophasic epithelioid (9/26, 35%), monophasic spindle cell (5/26, 19%), and biphasic or mixed histology (12/26, 46%). One or more aggressive histopathologic features were seen in 11 cases. DNA sequencing was successful in 22 tumors. Pathogenic CTNNB1 and APC alterations were seen in 7 (33%) and 2 (10%) cases, respectively, with additional variants (e.g., CDKN2A, RB1, TP53, BRCA2) being identified in individual cases. Combined evaluation of morphology, sequencing data and beta-catenin immunohistochemistry resulted in reclassification of 6 (23%) tumors as Sertoli cell tumor, not otherwise specified. This was supported by comparing the methylation profiles of a subset of these tumors and those of typical Sertoli cell tumors. Additionally, a subset of 5 neoplasms (19%) with spindle cell or biphasic histology and SMA expression was characterized by hyperdiploid genomes with recurrent chromosomal gains and absence of driver mutations, possibly representing a distinct tumor type. The SCST that remained not amenable to specific histologic classification (15/26, 58%) were enriched for aggressive histologic features and malignant clinical behavior. In conclusion, this study demonstrated that a subset of testicular SCST that were originally not amenable to specific classification could be reclassified by combined evaluation of morphology, immunohistochemistry and molecular data.

A nomogram combining clinical factors and biomarkers for predicting the recurrence of high-risk cutaneous squamous cell carcinoma

Background

Although determining the recurrence of cutaneous squamous cell carcinoma (cSCC) is important, currently suggested systems and single biomarkers have limited power for predicting recurrence.

Objective

In this study, combinations of clinical factors and biomarkers were adapted into a nomogram to construct a powerful risk prediction model.

Methods

The study included 145 cSCC patients treated with Mohs micrographic surgery. Clinical factors were reviewed, and immunohistochemistry was performed using tumor tissue samples. A nomogram was constructed by combining meaningful clinical factors and protein markers.

Results

Among the various factors, four clinical factors (tumor size, organ transplantation history, poor differentiation, and invasion into subcutaneous fat) and two biomarkers (Axin2 and p53) were selected and combined into a nomogram. The concordance index (C-index) of the nomogram for predicting recurrence was 0.809, which was higher than that for the American Joint Committee on Cancer (AJCC) 7th, AJCC 8th, Brigham and Women’s Hospital, and Breuninger staging systems in the patient data set.

Conclusion

A nomogram model that included both clinical factors and biomarkers was much more powerful than previous systems for predicting cSCC recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10213-2.

LRP5 and LRP6 in Wnt Signaling: Similarity and Divergence

The canonical Wnt/β-catenin signaling plays a fundamental role in regulating embryonic development, injury repair and the pathogenesis of human diseases. In vertebrates, low density lipoprotein receptor-related proteins 5 and 6 (LRP5 and LRP6), the single-pass transmembrane proteins, act as coreceptors of Wnt ligands and are indispensable for Wnt signal transduction. LRP5 and LRP6 are highly homologous and widely co-expressed in embryonic and adult tissues, and they share similar function in mediating Wnt signaling. However, they also exhibit distinct characteristics by interacting with different protein partners. As such, each of them possesses its own unique functions. In this review, we systematically discuss the similarity and divergence of LRP5 and LRP6 in mediating Wnt and other signaling in the context of kidney diseases. A better understanding of the precise role of LRP5 and LRP6 may afford us to identify and refine therapeutic targets for the treatment of a variety of human diseases.

Ubiquitin-Regulated Cell Proliferation and Cancer

Ubiquitin ligases (E3) play a crucial role in the regulation of different cellular processes such as proliferation and differentiation via recognition, interaction, and ubiquitination of key cellular proteins in a spatial and temporal regulated manner. The type of ubiquitin chain formed determines the fate of the substrates. The ubiquitinated substrates can be degraded by the proteasome, display altered subcellular localization, or can suffer modifications on their interaction with functional protein complexes. Deregulation of E3 activities is frequently found in various human pathologies, including cancer. The illegitimated or accelerated degradation of oncosuppressive proteins or, inversely, the abnormally high accumulation of oncoproteins, contributes to cell proliferation and transformation. Anomalies in protein abundance may be related to mutations that alter the direct or indirect recognition of proteins by the E3 enzymes or alterations in the level of expression or activity of ubiquitin ligases. Through a few examples, we illustrate here the complexity and diversity of the molecular mechanisms related to protein ubiquitination involved in cell cycle regulation. We will discuss the role of ubiquitin-dependent degradation mediated by the proteasome, the role of non-proteolytic ubiquitination during cell cycle progression, and the consequences of this deregulation on cellular transformation. Finally, we will highlight the novel opportunities that arise from these studies for therapeutic intervention.

A tannin compound from Sanguisorba officinalis blocks Wnt/β-catenin signaling pathway and induces apoptosis of colorectal cancer cells

BACKGROUND

Sanguisorba officinalis, a popular Chinese herb, called DiYu, has been shown to inhibit the growth of many human cancer cell lines, including colorectal cancer cells. The aims of this study were to discover the active compound and molecular mechanism of S. officinalis against Wnt/β-catenin signaling pathway and develop Wnt inhibitors from natural products as anti-colorectal cancer agents.

METHODS

1,4,6-Tri-O-galloyl-β-d-glucopyranose (TGG) was obtained by the preparative HPLC. The effect of DiYu on proliferation of NIH3T3 and HT29 was detected by MTT assay. Luciferase reporter assay was applied to investigate the activity of Wnt/β-catenin signaling in NIH3T3. The expression levels of mRNA and protein were detected by RT-PCR and western blot. Immunofluorescence assay was used to measure the level of β-catenin in cytoplasm and nucleus. Transcriptomic profiling study was performed to investigate the molecular mechanism of DiYu on the Wnt/β-catenin signaling pathway.

RESULTS

TGG significantly inhibited the Wnt/β-catenin signaling pathway, down-regulated the expression of β-catenin and Wnt target genes (Dkk1, c-Myc, FGF20, NKD1, Survivin), up-regulated the levels of cleaved caspase3, cleaved PARP and ratio of Bax/Bcl-2, which may explain the apoptosis of HT29.

CONCLUSIONS

Our study enhanced the discovery of the materials and elucidation of mechanisms that account for the anti-Wnt activity of natural inhibitor (DiYu) and identified the potential of TGG to be developed as anti-colorectal cancer drugs.

A Positive Feed-Forward Loop between LncRNA-CYTOR and Wnt/β-Catenin Signaling Promotes Metastasis of Colon Cancer

We previously demonstrated that long non-coding RNA cytoskeleton regulator RNA (CYTOR), also known as Linc00152, was significantly overexpressed in colon cancer and conferred resistance to oxaliplatin-induced apoptosis. At the same time, elevated CYTOR expression was also reported in gastric cancer and exerted influences on epithelial-mesenchymal transition (EMT) markers. However, the precise mechanism by which CYTOR promotes the EMT phenotype and cancer metastasis remains poorly understood. Here, we showed that loss of epithelial characteristics and simultaneous gain of mesenchymal features correlated with CYTOR expression. Knockdown of CYTOR attenuated colon cancer cell migration and invasion. Conversely, ectopic expression of CYTOR induced an EMT program and enhanced metastatic properties of colon cancer cells. Mechanistically, the binding of CYTOR to cytoplasmic β-catenin impeded casein kinase 1 (CK1)-induced β-catenin phosphorylation that enabled it to accumulate and translocate to the nucleus. Reciprocally, β-catenin/TCF complex enhanced the transcription activity of CYTOR in nucleus, thus forming a positive feed-forward circuit. Moreover, elevated CYTOR, alone or combined with overexpression of nuclear β-catenin, was predictive of poor prognosis. Our findings suggest that CYTOR promotes colon cancer EMT and metastasis by interacting with β-catenin, and the positive feed-forward circuit of CYTOR-β-catenin might be a useful therapeutic target in antimetastatic strategy.

Protein Kinase C-ζ stimulates colorectal cancer cell carcinogenesis via PKC-ζ/Rac1/Pak1/β-Catenin signaling cascade

Colorectal cancer (CRC) is the second most common cancer in the world and death from CRC accounts for 8% of all cancer deaths both in men and women in the United States. CRC is life-threatening disease due to therapy resistant cancerous cells. The exact mechanisms of cell growth, survival, metastasis and inter & intracellular signaling pathways involved in CRC is still a significant challenge. Hence, investigating the signaling pathways that lead to colon carcinogenesis may give insight into the therapeutic target. In this study, the role of atypical Protein Kinase C (aPKC) on CRC was investigated by using two inhibitors of that protein class: 1) ζ-Stat (8-hydroxynaphthalene-1,3,6-trisulfonic acid) is a specific inhibitor of PKC-ζ and 2) ICA-I 5-amino-1-(2,3-dihydroxy-4-hydroxymethyl)cyclopentyl)-1H-imidazole-4-carboxamide) is a specific inhibitor of PKC-ι. The cell lines tested were CCD18CO normal colon epithelial and LOVO metastatic CRC cells. The inhibition of aPKCs did not bring any significant toxicity on CCD18CO normal colon cell line. Although PKC-ι is an oncogene in many cancers, we found the overexpression of PKC-ζ and its direct association with Rac1. Our findings suggest that the PKC-ζ may be responsible for the abnormal growth, proliferation, and migration of metastatic LOVO colon cancer cells via PKC-ζ/Rac1/Pak1/β-Catenin pathway. These results suggest the possibility of utilizing PKC-ζ inhibitor to block CRC cells growth, proliferation, and metastasis.

Aqueous extract of Sanguisorba officinalis blocks the Wnt/β-catenin signaling pathway in colorectal cancer cells

Sanguisorba officinalis (the Chinese name is DiYu, DY) exerts significant anti-proliferative activities against colorectal cancer (CRC) cells.

Snail and Axin2 expression predict the malignant transformation of oral leukoplakia

OBJECTIVES

Oral leukoplakia (OL) has a well-documented potential risk of malignant transformation into oral squamous cell carcinoma (OSCC), although biomarker(s) predicting malignant potential are limited in capability. The aim of this cross-sectional and retrospective cohort study was to investigate the predictive role of canonical Wnt genes Axin2 and Snail (SNAI1) expression in the malignant transformation of OL lesions.

MATERIALS AND METHODS

The expression of epithelial-mesenchymal transition (EMT) genes Snail and Axin2, which are regulated by the canonical Wnt pathway, were determined using immunohistochemical staining in an OL cohort consisting of 154 samples of patients with long-term follow-up and then evaluated as risk factors for malignant transformation of OL.

RESULTS

Increased Axin2 and Snail abundance were found in 107 (69.5%) and 58 (37.7%) of OL patients, respectively. In a multivariate analysis using gender, age, lesion site, Axin2, and Snail as cofactors, both Axin2 and Snail were independent risk factors for malignant transformation with a hazard ratio of 7.47 (95% confidence interval, 2.23-25.02; P=0.001) and 4.41 (95% confidence interval, 1.78-10.93; P=0.001), respectively. A nomogram for predicting 5-, 10-, and 15-year cancer-free survival probability was developed in patients with OL by including gender, age, lesion site, Axin2, and Snail expression with ac-index of 0.760.

CONCLUSION

The increased abundance of Snail and Axin2 is highly correlated to malignant transformation of OL, making them novel biomarker(s) predicting oral cancer development.

Canonical Wnt signaling in diabetic retinopathy

Diabetic retinopathy (DR) is a common eye complication of diabetes, and the pathogenic mechanism of DR is still under investigation. The canonical Wnt signaling pathway is an evolutionarily conserved pathway that plays fundamental roles in embryogenesis and adult tissue homeostasis. Wnt signaling regulates expression of multiple genes that control retinal development and eye organogenesis, and dysregulated Wnt signaling plays pathophysiological roles in many ocular diseases, including DR. This review highlights recent progress in studies of Wnt signaling in DR. We discuss Wnt signaling regulation in the retina and dysregulation of Wnt signaling associated with ocular diseases with an emphasis on DR. We also discuss the therapeutic potential of modulating Wnt signaling in DR. Continued studies in this field will advance our current understanding on DR and contribute to the development of new treatments.

Identification of miRNA biomarkers of pneumonia using RNA-sequencing and bioinformatics analysis

Pneumonia is a lower respiratory tract infection that causes dramatic mortality worldwide. The present study aimed to investigate the pathogenesis of pneumonia and identify microRNA (miRNA) biomarkers as candidates for targeted therapy. RNA from the peripheral blood plasma of participants with pneumonia (severe, n=9; non-severe, n=9) and controls (n=9) was isolated and paired-end sequencing was performed on an Illumina HiSeq4000 system. Following the processing of raw reads, the sequences were aligned against the Genome Reference Consortium human genome assembly 38 reference genome using Bowtie2 software. Reads per kilobase of transcript per million mapped read values were obtained and the limma software package was used to identify differentially expressed miRNAs (DE-miRs). Then, DE-miR targets were predicted and subjected to enrichment analysis. In addition, a protein-protein interaction (PPI) network of the predicted targets was constructed. This analysis identified 11 key DE-miRs in pneumonia samples, including 6 upregulated miRNAs (including hsa-miR-34a and hsa-miR-455) and 5 downregulated miRNAs (including hsa-let-7f-1). All DE-miRs kept their upregulation/downregulation pattern in the control, non-severe pneumonia and severe pneumonia samples. Predicted target genes of DE-miRs in the subjects with non-severe pneumonia vs. the control and the subjects with severe pneumonia vs. the non-severe pneumonia group were markedly enriched in the adherens junction and Wnt signaling pathways. KALRN, Ras homolog family member A (RHOA), β-catenin (CTNNB1), RNA polymerase II subunit K (POLR2K) and amyloid precursor protein (APP) were determined to encode crucial proteins in the PPI network constructed. KALRN was predicted to be a target of hsa-mir-200b, while RHOA, CTNNB1, POLR2K and APP were predicted targets of hsa-let-7f-1. The results of the present study demonstrated that hsa-let-7f-1 may serve a role in the development of cancer and the Notch signaling pathway. Conversely, hsa-miR-455 may be an inhibitor of pneumonia pathogenesis. Furthermore, hsa-miR-200b might promote pneumonia via targeting KALRN.

Wnt2 and WISP-1/CCN4 Induce Intimal Thickening via Promotion of Smooth Muscle Cell Migration

OBJECTIVE

Increased vascular smooth muscle cell (VSMC) migration leads to intimal thickening which acts as a soil for atherosclersosis, as well as causing coronary artery restenosis after stenting and vein graft failure. Investigating factors involved in VSMC migration may enable us to reduce intimal thickening and improve patient outcomes. In this study, we determined whether Wnt proteins regulate VSMC migration and thereby intimal thickening.

APPROACH AND RESULTS

Wnt2 mRNA and protein expression were specifically increased in migrating mouse aortic VSMCs. Moreover, VSMC migration was induced by recombinant Wnt2 in vitro. Addition of recombinant Wnt2 protein increased Wnt1-inducible signaling pathway protein-1 (WISP-1) mRNA by ≈1.7-fold, via β-catenin/T-cell factor signaling, whereas silencing RNA knockdown of Wnt-2 reduced WISP-1 mRNA by ≈65%. Treatment with rWISP-1 significantly increased VSMC migration by ≈1.5-fold, whereas WISP-1 silencing RNA knockdown reduced migration by ≈40%. Wnt2 and WISP-1 effects were integrin-dependent and not additive, indicating that Wnt2 promoted VSMC migration via WISP-1. Additionally, Wnt2 and WISP-1 were significantly increased and colocated in human coronary arteries with intimal thickening. Reduced Wnt2 and WISP-1 levels in mouse carotid arteries from Wnt2(+/-) and WISP-1(-/-) mice, respectively, significantly suppressed intimal thickening in response to carotid artery ligation. In contrast, elevation of plasma WISP-1 via an adenovirus encoding WISP-1 significantly increased intimal thickening by ≈1.5-fold compared with mice receiving control virus.

CONCLUSIONS

Upregulation of Wnt2 expression enhanced WISP-1 and promoted VSMC migration and thereby intimal thickening. As novel regulators of VSMC migration and intimal thickening, Wnt2 or WISP-1 may provide a potential therapy for restenosis and vein graft failure.

The coiled-coil domain containing protein Ccdc136b antagonizes maternal Wnt/β-catenin activity during zebrafish dorsoventral axial patterning

The coiled-coil domain containing protein CCDC136 is a putative tumor suppressor and significantly down-regulated in gastric and colorectal cancer tissues. However, little is known about its biological functions during vertebrate embryo development. Zebrafish has two CCDC136 orthologs, ccdc136a and ccdc136b, but only ccdc136b is highly expressed during early embryonic development. In this study, we demonstrate that ccdc136b is required for dorsal-ventral axial patterning in zebrafish embryos. ccdc136b morphants display strongly dorsalized phenotypes. Loss- and gain-of-function experiments in zebrafish embryos and mammalian cells show that Ccdc136b is a crucial negative regulator of the Wnt/β-catenin signaling pathway, and plays a critical role in the establishment of the dorsal-ventral axis. We further find that Ccdc136b interacts with APC, promotes the binding affinity of APC with β-catenin and then facilitates the turnover of β-catenin. These results provide the first evidence that CCDC136 regulates zebrafish dorsal-ventral patterning by antagonizing Wnt/β-catenin signal transduction and suggest a potential mechanism underlying its suppressive activity in carcinogenesis.

Beta-catenin is essential for ameloblast movement during enamel development

Beta-catenin is a multifunctional protein that plays key roles in cadherin-based cell adherens junctions and in the Wnt signaling pathway. The canonical Wnt/β-catenin pathway can regulate transcription factors that control cell movement/invasion. We investigated whether β-catenin regulates ameloblast movement through canonical Wnt signaling. The morphological and physical properties of enamel were assessed in enamel from control and β-catenin conditional knockout (cKO) mice. Ameloblast-lineage cells (ALC) were used to investigate the potential roles of β-catenin in cell migration and in E-cadherin expression. Compared with controls, incisors from β-catenin cKO mice were short, blunt, and where enamel was present, it was soft and malformed. Scanning electron microscopy revealed a dysplastic rod pattern within the enamel of incisors from β-catenin cKO mice, and Vickers microhardness measurements confirmed that mice with β-catenin ablated from their enamel organ had enamel that was significantly softer than normal. Amelogenesis was disrupted in the absence of β-catenin and the ameloblasts did not differentiate properly. We further demonstrated that migration of ALCs was inhibited in vitro and that E-cadherin expression was significantly up-regulated when ALCs were treated with the β-catenin inhibitor, ICG-001. Beta-catenin ablation causes enamel malformation in mice and this phenotype may occur, in part, by a lack of ameloblast differentiation and/or movement necessary to form the decussating enamel rod structure.

Wnt/β-catenin coupled with HIF-1α/VEGF signaling pathways involved in galangin neurovascular unit protection from focal cerebral ischemia

Microenvironmental regulation has become a promising strategy for complex disease treatment. The neurovascular unit (NVU), as the key structural basis to maintain an optimal brain microenvironment, has emerged as a new paradigm to understand the pathology of stroke. In this study, we investigated the effects of galangin, a natural flavonoid isolated from the rhizome of Alpina officinarum Hance, on NVU microenvironment improvement and associated signal pathways in rats impaired by middle cerebral artery occlusion (MCAO). Galangin ameliorated neurological scores, cerebral infarct volume and cerebral edema and reduced the concentration of Evans blue (EB) in brain tissue. NVU ultrastructural changes were also improved by galangin. RT-PCR and western blot revealed that galangin protected NVUs through the Wnt/β-catenin pathway coupled with HIF-1α and vascular endothelial growth factor (VEGF). VEGF and β-catenin could be the key nodes of these two coupled pathways. In conclusion, Galangin might function as an anti-ischemic stroke drug by improving the microenvironment of NVUs.

Schizophrenia: Evidence implicating hippocampal GluN2B protein and REST epigenetics in psychosis pathophysiology

The hippocampus is strongly implicated in the psychotic symptoms of schizophrenia. Functionally, basal hippocampal activity (perfusion) is elevated in schizophrenic psychosis, as measured with positron emission tomography (PET) and with magnetic resonance (MR) perfusion techniques, while hippocampal activation to memory tasks is reduced. Subfield-specific hippocampal molecular pathology exists in human psychosis tissue which could underlie this neuronal hyperactivity, including increased GluN2B-containing NMDA receptors in hippocampal CA3, along with increased postsynaptic density protein-95 (PSD-95) along with augmented dendritic spines on the pyramidal neuron apical dendrites. We interpret these observations to implicate a reduction in the influence of a ubiquitous gene repressor, repressor element-1 silencing transcription factor (REST) in psychosis; REST is involved in the age-related maturation of the NMDA receptor from GluN2B- to GluN2A-containing NMDA receptors through epigenetic remodeling. These CA3 changes in psychosis leave the hippocampus liable to pathological increases in neuronal activity, feedforward excitation and false memory formation, sometimes with psychotic content.

CCM1 and the second life of proteins in adhesion complexes

It is well recognized that a number of proteins present within adhesion complexes perform discrete signaling functions outside these adhesion complexes, including transcriptional control. In this respect, β-catenin is a well-known example of an adhesion protein present both in cadherin complexes and in the nucleus where it regulates the TCF transcription factor. Here we discuss nuclear functions of adhesion complex proteins with a special focus on the CCM-1/KRIT-1 protein, which may turn out to be yet another adhesion complex protein with a second life.

Casein kinase 1 suppresses activation of REST in insulted hippocampal neurons and halts ischemia-induced neuronal death

Repressor Element-1 (RE1) Silencing Transcription Factor/Neuron-Restrictive Silencer Factor (REST/NRSF) is a gene-silencing factor that is widely expressed during embryogenesis and plays a strategic role in neuronal differentiation. Recent studies indicate that REST can be activated in differentiated neurons during a critical window of time in postnatal development and in adult neurons in response to neuronal insults such as seizures and ischemia. However, the mechanism by which REST is regulated in neurons is as yet unknown. Here, we show that REST is controlled at the level of protein stability via β-TrCP-dependent, ubiquitin-based proteasomal degradation in differentiated neurons under physiological conditions and identify Casein Kinase 1 (CK1) as an upstream effector that bidirectionally regulates REST cellular abundance. CK1 associates with and phosphorylates REST at two neighboring, but distinct, motifs within the C terminus of REST critical for binding of β-TrCP and targeting of REST for proteasomal degradation. We further show that global ischemia in rats in vivo triggers a decrease in CK1 and an increase in REST in selectively vulnerable hippocampal CA1 neurons. Administration of the CK1 activator pyrvinium pamoate by in vivo injection immediately after ischemia restores CK1 activity, suppresses REST expression, and rescues neurons destined to die. Our results identify a novel and previously unappreciated role for CK1 as a brake on REST stability and abundance in adult neurons and reveal that loss of CK1 is causally related to ischemia-induced neuronal death. These findings point to CK1 as a potential therapeutic target for the amelioration of hippocampal injury and cognitive deficits associated with global ischemia.

The β-catenin E3 ubiquitin ligase SIAH-1 is regulated by CSN5/JAB1 in CRC cells

COP9 signalosome subunit 5 (CSN5) plays a decisive role in cellular processes such as cell cycle regulation and apoptosis via promoting protein degradation, gene transcription, and nuclear export. CSN5 regulates cullin-RING-E3 ligase (CRL) activity through its deNEDDylase function. It is overexpressed in several tumor entities, but its role in colorectal cancer (CRC) is poorly understood. Wnt/β-catenin signaling is aberrant in most CRC cells, resulting in increased levels of oncogenic β-catenin and thus tumor progression. Under physiological conditions, β-catenin levels are tightly regulated by continuous proteasomal degradation. We recently showed that knockdown of CSN5 in model and CRC cells results in decreased (phospho)-β-catenin levels. Reduced β-catenin levels were associated with an attenuated proliferation rate of different CRC cell types after CSN5 knockdown. The canonical Wnt pathway involves degradation of β-catenin by a β-TrCP1-containing E3 ligase, but is mostly non-functional in CRC cells. We thus hypothesized that alternative β-catenin degradation mediated by SIAH-1 (seven in absentia homolog-1), is responsible for the effect of CSN5 on β-catenin signaling in CRC cells. We found that SIAH-1 plays an essential role in β-catenin degradation in HCT116 CRC cells and that CSN5 affects β-catenin target gene expression in these cells. Of note, CSN5 affected SIAH-1 mRNA and SIAH-1 protein levels. Moreover, β-catenin and SIAH-1 form protein complexes with CSN5 in HCT116 cells. Lastly, we demonstrate that CSN5 promotes SIAH-1 degradation in HCT116 and SW480 cells and that this is associated with its deNEDDylase activity. In conclusion, we have identified a CSN5/β-catenin/SIAH-1 interaction network that might control β-catenin degradation in CRC cells.

Inhibition of the HER2 pathway by n-3 polyunsaturated fatty acids prevents breast cancer in fat-1 transgenic mice

Overexpression of the tyrosine kinase receptor, ErbB2/HER2/Neu, occurs in 25-30% of invasive breast cancer (BC) with poor patient prognosis. Due to confounding factors, inconsistencies still remain regarding the protective effects of n-3 polyunsaturated fatty acids (PUFAs) on BC. We therefore evaluated whether fat-1 transgenic mice, endogenously synthesizing n-3 PUFAs from n-6 PUFAs, were protected against BC development, and we then aimed to study in vivo a mechanism potentially involved in such protection. E0771 BC cells were implanted into fat-1 and wild-type (WT) mice. After tumorigenesis examination, we analyzed the expression of proteins involved in the HER2 signaling pathway and lipidomic analyses were performed in tumor tissues and plasma. Our results showed that tumors totally disappeared by day 15 in fat-1 mice but continued to grow in WT mice. This prevention can be related in part to significant repression of the HER2/β-catenin signaling pathway and formation of significant levels of n-3 PUFA-derived bioactive mediators (particularly 15-hydroxyeicosapentaenoic acid, 17-hydroxydocosahexaenoic acid, and prostaglandin E3) in the tumors of fat-1 mice compared with WT mice. All together these data demonstrate an anti-BC effect of n-3 PUFAs through, at least in part, HER2 signaling pathway downregulation, and highlight the importance of gene-diet interactions in BC.

Thyroid hormone receptors and cancer

BACKGROUND

Thyroid hormone receptors (TRs) are ligand-dependent transcription factors that mediate the actions of the thyroid hormone (T3) in development, growth, and differentiation. The THRA and THRB genes encode several TR isoforms that express in a tissue- and development-dependent manner. In the past decades, a significant advance has been made in the understanding of TR actions in maintaining normal cellular functions. However, the roles of TRs in human cancer are less well understood. The reduced expression of TRs because of hypermethylation, or deletion of TR genes found in human cancers suggests that TRs could function as tumor suppressors. A close association of somatic mutations of TRs with human cancers further supports the notion that the loss of normal functions of TR could lead to uncontrolled growth and loss of cell differentiation.

SCOPE OF REVIEW

In line with the findings from association studies in human cancers, mice deficient in total functional TRs (Thra1(-/-)Thrb(-/-) mice) or with a targeted homozygous mutation of the Thrb gene (denoted PV; Thrb(PV/PV) mice) spontaneously develop metastatic thyroid carcinoma. This review will examine the evidence learned from these genetically engineered mice that provided strong evidence to support the critical role of TRs in human cancer.

MAJOR CONCLUSIONS

Loss of normal functions of TR by deletion or by mutations could contribute to cancer development, progression and metastasis.

GENERAL SIGNIFICANCE

Novel mechanistic insights are revealed in how aberrant TR activities lead to carcinogenesis. Mouse models of thyroid cancer provide opportunities to identify molecular targets as potential treatment modalities. This article is part of a Special Issue entitled Thyroid hormone signalling.

Systems biology approach identifies the kinase Csnk1a1 as a regulator of the DNA damage response in embryonic stem cells

In pluripotent stem cells, DNA damage triggers loss of pluripotency and apoptosis as a safeguard to exclude damaged DNA from the lineage. An intricate DNA damage response (DDR) signaling network ensures that the response is proportional to the severity of the damage. We combined an RNA interference screen targeting all kinases, phosphatases, and transcription factors with global transcriptomics and phosphoproteomics to map the DDR in mouse embryonic stem cells treated with the DNA cross-linker cisplatin. Networks derived from canonical pathways shared in all three data sets were implicated in DNA damage repair, cell cycle and survival, and differentiation. Experimental probing of these networks identified a mode of DNA damage-induced Wnt signaling that limited apoptosis. Silencing or deleting the p53 gene demonstrated that genotoxic stress elicited Wnt signaling in a p53-independent manner. Instead, this response occurred through reduced abundance of Csnk1a1 (CK1α), a kinase that inhibits β-catenin. Together, our findings reveal a balance between p53-mediated elimination of stem cells (through loss of pluripotency and apoptosis) and Wnt signaling that attenuates this response to tune the outcome of the DDR.

Maintenance of adenomatous polyposis coli (APC)-mutant colorectal cancer is dependent on Wnt/beta-catenin signaling

Persistent expression of certain oncogenes is required for tumor maintenance. This phenotype is referred to as oncogene addiction and has been clinically validated by anticancer therapies that specifically inhibit oncoproteins such as BCR-ABL, c-Kit, HER2, PDGFR, and EGFR. Identifying additional genes that are required for tumor maintenance may lead to new targets for anticancer drugs. Although the role of aberrant Wnt pathway activation in the initiation of colorectal cancer has been clearly established, it remains unclear whether sustained Wnt pathway activation is required for colorectal tumor maintenance. To address this question, we used inducible β-catenin shRNAs to temporally control Wnt pathway activation in vivo. Here, we show that active Wnt/β-catenin signaling is required for maintenance of colorectal tumor xenografts harboring APC mutations. Reduced tumor growth upon β-catenin inhibition was due to cell cycle arrest and differentiation. Upon reactivation of the Wnt/β-catenin pathway colorectal cancer cells resumed proliferation and reacquired a crypt progenitor phenotype. In human colonic adenocarcinomas, high levels of nuclear β-catenin correlated with crypt progenitor but not differentiation markers, suggesting that the Wnt/β-catenin pathway may also control colorectal tumor cell fate during the maintenance phase of tumors in patients. These results support efforts to treat human colorectal cancer by pharmacological inhibition of the Wnt/β-catenin pathway.

A Rac1/PAK1 cascade controls β-catenin activation in colon cancer cells

P21-activated kinase 1 (PAK1) is associated with colon cancer progression and metastasis, whereas the molecular mechanism remains elusive. Here, we show that downregulation of PAK1 in colon cancer cells reduces total β-catenin level, as well as cell proliferation. Mechanistically, PAK1 directly phosphorylates β-catenin proteins at Ser675 site and this leads to more stable and transcriptional active β-catenin. Corroborating these results, PAK1 is required for full Wnt signaling, and superactivation of β-catenin is achieved by simultaneous knockdown of adenomatous polyposis coli protein and activation of PAK1. Moreover, we show that Rac1 functions upstream of PAK1 in colon cancer cells and contributes to β-catenin phosphorylation and accumulation. We conclude that a Rac1/PAK1 cascade controls β-catenin S675 phosphorylation and full activation in colon cancer cells. Supporting this conclusion, overexpression of PAK1 is observed in 70% of colon cancer samples and is correlated with massive β-catenin accumulation.

Functional implications of glycogen synthase kinase-3-mediated tau phosphorylation

Tau is primarily a neuronal microtubule-associated protein that has functions related to the stabilisation of microtubules. Phosphorylation of tau is an important dynamic and regulatory element involved in the binding of tau to tubulin. Thus, highly phosphorylated tau is more likely to be present in the cytosolic compartment of neurons, whereas reduced phosphate burden allows tau to bind to and stabilise the microtubule cytoskeleton. Highly phosphorylated forms of tau are deposited in the brain in a range of neurodegenerative disorders including Alzheimer's disease, progressive supranuclear palsy, and frontotemporal lobar degeneration associated with Pick bodies. A key candidate kinase for both physiological and pathological tau phosphorylation is glycogen synthase kinase-3 (GSK-3). Multiple phosphorylation sites have been identified on tau exposed to GSK-3 in vitro and in cells. In this review, we highlight recent data suggesting a role for GSK-3 activity on physiological tau function and on tau dysfunction in neurodegenerative disease.

Transcriptional pattern of TGF-β1 inhibitory effect on mouse C2C12 myoblasts differentiation

The aim of the present study was to define the effect of TGF-β1 on C2C12 myoblasts myogenesis. TGF-β1 together with its receptor is a negative auto-paracrine regulator of myogenesis, which influences the proliferation, differentiation, and functions of muscle cells. TGF-β1 exerts highly significant inhibitory effect on differentiation of C2C12 mouse myoblasts manifested by the impairment of cell fusion and very low expression of myosin heavy chain. The study of differentiating C2C12 mouse myoblasts treated with TGF-β1 revealed 502 genes (436 down-regulated and 66 up-regulated) with statistically different expression. TGF-β1-regulated genes were identified to be involved in 29 biological processes, 29 molecular functions groups and 59 pathways. The strongest inhibiting effect of TGF-β1 was observed in the cadherin and Wnt pathways. The key-genes that could play the role of TGF-β1 targets during myoblasts differentiation was identified such as: Max, Creb1, Ccna2, Bax, MdfI, Tef, Tubg1, Cxcl5, Rho, Calca and Lgals4.

Wnt pathway antagonists and angiogenesis

Dysregulation of the Wnt pathway has been extensively studied in multiple diseases, including some angiogenic disorders. Wnt signaling activation is a major stimulator in pathological angiogenesis and thus, Wnt antagonists are believed to have therapeutic potential for neovascular disorders. Actually, some Wnt antagonists have been identified directly from the anti-angiogenic factor family. This review summarizes the recent progress toward understanding of the roles of Wnt pathway antagonists in angiogenic regulation and their mechanism of action, and exploring their therapeutic potential.

Suppression of casein kinase 1alpha in melanoma cells induces a switch in beta-catenin signaling to promote metastasis

Casein kinase 1 alpha (CK1alpha) is a multifunctional Ser/Thr kinase that phosphorylates several substrates. Among those is beta-catenin, an important player in cell adhesion and Wnt signaling. Phosphorylation of beta-catenin by CK1alpha at Ser45 is the priming reaction for the proteasomal degradation of beta-catenin. Interestingly, aside from this role in beta-catenin degradation, very little is known about the expression and functional role of CK1alpha in tumor cells. Here, we show that CK1alpha expression in different tumor types is either strongly suppressed or completely lost during tumor progression and that CK1alpha is a key factor determining beta-catenin stability and transcriptional activity in tumor cells. CK1alpha reexpression in metastatic melanoma cells reduces growth in vitro and metastasis formation in vivo, and induces cell cycle arrest and apoptosis, whereas suppression of CK1alpha in primary melanoma cells induces invasive tumor growth. Inactivation of CK1alpha promotes tumor progression by regulating a switch in beta-catenin-mediated signaling. These results show that melanoma cells developed an efficient new mechanism to activate the beta-catenin signaling pathway and define CK1alpha as a novel tumor suppressor.

Inhibition of connective tissue growth factor overexpression in diabetic retinopathy by SERPINA3K via blocking the WNT/beta-catenin pathway

OBJECTIVE

Connective tissue growth factor (CTGF) is a major fibrogenic factor. Increased retinal CTGF levels have been implicated to play a role in diabetic retinopathy. SERPINA3K is a serine proteinase inhibitor, and its levels were decreased in retinas with diabetic retinopathy. The purpose of this study was to investigate the role of SERPINA3K in the regulation of CTGF and fibrogenesis and its mechanism of action.

RESEARCH DESIGN AND METHODS

Adenovirus expressing SERPINA3K was injected intravitreally into streptozotocin-induced diabetic rats. CTGF expression was measured using Western blot analysis and real-time RT-PCR. Fibrosis was evaluated by quantifying retinal fibronectin using enzyme-linked immunosorbent assay. Wnt pathway activation was determined by phosphorylation of LDL receptor-related protein 6, a coreceptor of Wnt ligands, and stabilization of beta-catenin, an essential effector of the canonical Wnt pathway.

RESULTS

Ad-SERPINA3K attenuated the CTGF and fibronectin overexpression in retinas of diabetic rats. In cultured retinal cells, SERPINA3K blocked the overproduction of CTGF induced by high glucose. Dickkopf-1, a specific Wnt antagonist, also attenuated the high-glucose-induced CTGF overexpression, indicating a role of Wnt signaling in CTGF overexpression in diabetes. Similarly, increased SERPINA3K blocked Wnt pathway activation in diabetic retinas and in cells treated with high glucose. Further, SERPINA3K also attenuated the Wnt3a-induced activation of the canonical Wnt pathway and the overexpression of CTGF.

CONCLUSION

SERPINA3K is an antifibrogenic factor, and its antifibrogenic activity is through blocking the Wnt pathway. Decreased SERPINA3K levels may contribute to the fibrosis in diabetic retinopathy.

Molecular imaging of glycogen synthase kinase-3beta and casein kinase-1alpha kinases

Glycogen synthase kinase-3beta (GSK3beta) and casein kinase-1alpha (CK1alpha) are multifunctional kinases that play critical roles in the regulation of a number of cellular processes. In spite of their importance, molecular imaging tools for noninvasive and real-time monitoring of their kinase activities have not been devised. Here we report development of the bioluminescent GSK3beta and CK1alpha reporter (BGCR) based on firefly luciferase complementation. Treatment of SW620 cells stably expressing the reporter with inhibitors of GSK3beta (SB415286 and LiCl) or CK1alpha (CKI-7) resulted in dose- and time-dependent increases in BGCR activity that were validated using Western blotting. No increase in bioluminescence was observed in the case of S37A mutant (GSK3beta inhibitors) or S45A mutant (CKI-7), demonstrating the specificity of the reporter. Imaging of mice tumor xenograft generated with BGCR-expressing SW620 cells following treatment with LiCl showed unique oscillations in GSK3beta activity that were corroborated by phosphorylated GSK3beta immunoblotting. Taken together, the BGCR is a novel molecular imaging tool that reveals unique insight into GSK3beta and CK1alpha kinase activities and may provide a powerful tool in experimental therapeutics for rapid optimization of dose and schedule of targeted therapies and for monitoring therapeutic response.

Partitioning of casein kinase 1-like 6 to late endosome-like vesicles

Members of the casein kinase 1 family are highly conserved protein Ser/Thr kinases found in all eukaryotes. They are involved in various cellular, physiological, and developmental processes, but the role of this family of kinase in plants is not well known. By localization studies employing fluorescent live cell imaging and biochemical membrane fractionation, here we showed that Arabidopsis casein kinase-like 6 (CKL6) localizes to motile vesicle-like structures that cofractionate with prevacuolar markers. They were found both in the cytoplasm and at the cell periphery and were motile within the cell. Apparently, this motility was dependent on actin filaments and CKL6-positive vesicles partially colocalized with a late endosomal compartment. However, CKL6-positive structures were not sensitive to brefeldin A nor wortmannin treatment, suggesting that they may belong to a novel compartment. Association of CKL6-positive structures with the cell periphery at the cellular junctions was detected after separation of the protoplasts by plasmolysis. Collectively, these data led us to propose that CKL6 is associated with late endosomal-like compartments that are not fully characterized and may play a role in cellular processes important for regulating components in membrane trafficking.

Blocking the Wnt pathway, a unifying mechanism for an angiogenic inhibitor in the serine proteinase inhibitor family

The Wnt pathway regulates multiple biological and pathological processes including angiogenesis and inflammation. Here we identified a unique inhibitor of the Wnt pathway, SERPINA3K, a serine proteinase inhibitor with anti-inflammatory and angiogenic activities. SERPINA3K blocked the Wnt pathway activation induced by a Wnt ligand and by diabetes. Coprecipitation and ligand binding assay showed that SERPINA3K binds to low-density lipoprotein receptor-like protein 6 (LRP6) with a K(d) of 10 nM, in the range of its physiological concentration in the retina. Under the same conditions, SERPINA3K did not bind to the frizzled (Fz) receptor or low-density lipoprotein receptor. Further, SERPINA3K bound to LRP6 at the extracellular domain and blocked its dimerization with the Fz receptor induced by a Wnt ligand. The antagonizing activity of SERPINA3K to LRP6 was further confirmed by Xenopus axis duplication assay. These results suggest that SERPINA3K is a high-affinity, endogenous antagonist of LRP6. The blockade of Wnt signaling may represent a unifying mechanism for the anti-inflammatory and anti-angiogenic effects of SERPINA3K.

Dynamic proteomic overview of glioblastoma cells (A172) exposed to perillyl alcohol

Perillyl alcohol (POH) is a naturally occurring terpene and a promising chemotherapeutic agent for glioblastoma multiform; yet, little is known about its molecular effects. Here we present results of a semi-quantitative proteomic analysis of A172 cells exposed to POH for different time-periods (1', 10', 30', 60', 4h, and 24h). The analysis identified more than 4000 proteins; which were clustered using PatternLab for proteomics and then linked to Ras signaling, tissue homeostasis, induction of apoptosis, metallopeptidase activity, and ubiquitin-protein ligase activity. Our results make available one of the most complete protein repositories for the A172. Moreover, we detected the phosphorylation of GSK3beta (Glycogen synthase kinase) and the inhibition of ERK's (extracellular signal regulated kinase) phosphorylation after 10', which suggests a new mechanism of POH's activation for apoptosis.

Hypothesis: neoplasms in myotonic dystrophy

Tumorigenesis is a multi-step process due to an accumulation of genetic mutations in multiple genes in diverse pathways which ultimately lead to loss of control over cell growth. It is well known that inheritance of rare germline mutations in genes involved in tumorigenesis pathways confer high lifetime risk of neoplasia in affected individuals. Furthermore, a substantial number of multiple malformation syndromes include cancer susceptibility in their phenotype. Studies of the mechanisms underlying these inherited syndromes have added to the understanding of both normal development and the pathophysiology of carcinogenesis. Myotonic dystrophy (DM) represents a group of autosomal dominant, multisystemic diseases that share the clinical features of myotonia, muscle weakness, and early-onset cataracts. Myotonic dystrophy type 1 (DM1) and myotonic dystrophy type 2 (DM2) result from unstable nucleotide repeat expansions in their respective genes. There have been multiple reports of tumors in individuals with DM, most commonly benign calcifying cutaneous tumors known as pilomatricomas. We provide a summary of the tumors reported in DM and a hypothesis for a possible mechanism of tumorigenesis. We hope to stimulate further study into the potential role of DM genes in tumorigenesis, and help define DM pathogenesis, and facilitate developing novel treatment modalities.

Novel non-genomic signaling of thyroid hormone receptors in thyroid carcinogenesis

The thyroid hormone receptors (TRs) are transcription factors that mediate the pleiotropic activities of the thyroid hormone, T3. Four T3-binding isoforms, TRalpha1, TRbeta1, TRbeta2, and TRbeta3, are encoded by two genes, THRA and THRB. Mutations and altered expression of TRs have been reported in human cancers. A targeted germ-line mutation of the Thrbeta gene in the mouse leads to spontaneous development of follicular thyroid carcinoma (TRbeta(PV/PV) mouse). The TRbetaPV mutant has lost T3-binding activity and displays potent dominant negative activity. The striking phenotype of thyroid cancer exhibited by TRbeta(PV/PV) mice has recently led to the discovery of novel non-genomic actions of TRbetaPV that contribute to thyroid carcinogenesis. These actions involve direct physical interaction of TRbetaPV with cellular proteins, namely the regulatory subunit of the phosphatidylinositol 3-kinase (p85alpha), the pituitary tumor transforming gene (PTTG) and beta-catenin, that are critically involved in cell proliferation, motility, migration, and metastasis. Thus, a TRbeta mutant (TRbetaPV), via a novel mode of non-genomic action, acts as an oncogene in thyroid carcinogenesis.

Novel oncogenic actions of TRbeta mutants in tumorigenesis

The thyroid hormone, T3, plays important roles in metabolism, growth, and differentiation. Germline mutations in thyroid hormone receptor beta (TRbeta) have been identified in many individuals with resistance to thyroid hormone, a syndrome of reduced sensitivity to T3. A close association of somatic mutations of TRbeta with several human cancers has become increasingly apparent, but how TRbeta mutants could be involved in the carcinogenesis in vivo has not been addressed. The creation of a mouse model (TRbeta(PV/PV) mouse) that harbors a knockin mutation of TRbeta (denoted TRbetaPV) has facilitated the study of the molecular actions of TRbeta mutants in vivo. The striking phenotype of thyroid cancer and the development of pituitary tumors exhibited by TRbeta(PV/PV) mice have uncovered novel functions of a TRbeta mutant in tumorigenesis. It led to the important findings that the oncogenic action of TRbetaPV is mediated by both genomic and nongenomic actions to alter gene expression and signaling pathways activity.

Isoreserpine promotes beta-catenin degradation via Siah-1 up-regulation in HCT116 colon cancer cells

Aberrant accumulation of intracellular beta-catenin in intestinal epithelial cells is a frequent early event during the development of colon cancer. To identify small molecules that decrease the level of intracellular beta-catenin, we performed cell-based chemical screening using genetically engineered HEK293 reporter cells to detect compounds that inhibit TOPFlash reporter activity, which was stimulated by Wnt3a-conditioned medium. We found that isoreserpine promoted the degradation of intracellular beta-catenin by up-regulation of Siah-1 in HEK293 and HCT116 colon cancer cells. Moreover, isoreserpine repressed the expression of beta-catenin/T-cell factor (TCF)-dependent genes, such as cyclin D1 and c-myc, resulting in the suppression of HCT116 cell proliferation. Our findings suggest that isoreserpine can potentially be used as a chemotherapeutic agent against colon cancer.

A two-step model for colon adenoma initiation and progression caused by APC loss

Aberrant Wnt/beta-catenin signaling following loss of the tumor suppressor adenomatous polyposis coli (APC) is thought to initiate colon adenoma formation. Using zebrafish and human cells, we show that homozygous loss of APC causes failed intestinal cell differentiation but that this occurs in the absence of nuclear beta-catenin and increased intestinal cell proliferation. Therefore, loss of APC is insufficient for causing beta-catenin nuclear localization. APC mutation-induced intestinal differentiation defects instead depend on the transcriptional corepressor C-terminal binding protein-1 (CtBP1), whereas proliferation defects and nuclear accumulation of beta-catenin require the additional activation of KRAS. These findings suggest that, following APC loss, CtBP1 contributes to adenoma initiation as a first step, whereas KRAS activation and beta-catenin nuclear localization promote adenoma progression to carcinomas as a second step. Consistent with this model, human FAP adenomas showed robust upregulation of CtBP1 in the absence of detectable nuclear beta-catenin, whereas nuclear beta-catenin was detected in carcinomas.

Hexachlorophene suppresses beta-catenin expression by up-regulation of Siah-1 in EBV-infected B lymphoma cells

Many studies have shown that the activation of β-catenin signaling can promote oncogenesis, and it is therefore of interest to find agents that modulate this pathway. Recent work has shown using B lymphoma cells that infection by Epstein–Barr virus (EBV) and expression of its latent membrane protein (LMP)-1, cause increases in the expression of β-catenin and cellular transformation. Conversely, results from cell-based small molecule screening studies have shown that the antibiotic hexachlorophene can down-regulate β-catenin in colon cancer cells. Here we report that hexachlorophene also counteracts the elevated β-catenin levels in EBV-infected B lymphomas. This is associated with restoration in levels of Siah-1 (an E3 ubiquitin ligase that is active in β-catenin regulation) which had been diminished by LMP-1. Our results suggest that Siah-1 is targeted by both LMP-1 and hexachlorophene with opposite effects. The hexachlorophene modulation of Siah-1 and β-catenin is independent of p53 and results in reduced expression of cyclin-D1 and c-Myc (target genes of β-catenin), leading to the growth arrest of B lymphoma cells. From these results we propose that hexachlorophene may provide a novel therapeutic strategy for EBV-infected B lymphoma cells by reducing β-catenin levels via the restoration of Siah-1.

Arabidopsis casein kinase 1-like 6 contains a microtubule-binding domain and affects the organization of cortical microtubules,

Members of the casein kinase 1 (CK1) family are evolutionarily conserved eukaryotic protein kinases that are involved in various cellular, physiological, and developmental processes in yeast and metazoans, but the biological roles of CK1 members in plants are not well understood. Here, we report that an Arabidopsis (Arabidopsis thaliana) CK1 member named casein kinase 1-like 6 (CKL6) associates with cortical microtubules in vivo and phosphorylates tubulins in vitro. The unique C-terminal domain of CKL6 was shown to contain the signal that allows localization of CKL6 to the cortical microtubules. This domain on its own was sufficient to associate with microtubules in vivo and to bind tubulins in vitro. CKL6 was able to phosphorylate soluble tubulins as well as microtubule polymers, and its endogenous activity was found to associate with a tubulin-enriched subcellular fraction. Two major in vitro phosphorylation sites were mapped to serine-413 and serine-420 of tubulin beta. Ectopic expression of wild-type CKL6 or a kinase-inactive mutant form induced alterations in cortical microtubule organization and anisotropic cell expansion. Collectively, these results demonstrate that CKL6 is a protein kinase containing a novel tubulin-binding domain and plays a role in anisotropic cell growth and shape formation in Arabidopsis through the regulation of microtubule organization, possibly through the phosphorylation of tubulins.

Bryostatin 1 modulates beta-catenin subcellular localization and transcription activity through protein kinase D1 activation

In recent years, the use of natural products for cancer prevention and treatment has received considerable attention. Bryostatin 1 is a natural macrocyclic lactone and a protein kinase D (PKD) modulator with potent antineoplastic properties that has been used to treat human cancers in clinical trials with limited success. Further understanding the mechanistic basis of Bryostatin 1 action may provide opportunities to improve clinical results of treatment with Bryostatin 1. We identified that PKD1, founding member of PKD family of serine/threonine kinases, modulates E-cadherin/beta-catenin activity, which plays an important role in cell integrity, polarity, growth, and morphogenesis. An aberrant expression and localization of E-cadherin/beta-catenin has been strongly associated with cancer progression and metastasis. In this study, we examined the effect of Bryostatin 1 treatment on PKD1 activation, beta-catenin translocation and transcription activity, and malignant phenotype of prostate cancer cells. Initial activation of PKD1 with Bryostatin 1 leads to colocalization of the cytoplasmic pool of beta-catenin with PKD1, trans-Golgi network markers, and proteins involved in vesicular trafficking. Activation of PKD1 by Bryostatin 1 decreases nuclear beta-catenin expression and beta-catenin/TCF transcription activity. Activation of PKD1 alters cellular aggregation and proliferation in prostate cancer cells associated with subcellular redistribution of E-cadherin and beta-catenin. For the first time, we have identified that Bryostatin 1 modulates beta-catenin signaling through PKD1, which identifies a novel mechanism to improve efficacy of Bryostatin 1 in clinical settings.

Inhibition of fibroblast growth factor 19 reduces tumor growth by modulating beta-catenin signaling

Fibroblast growth factors (FGF) play important roles in development, angiogenesis, and cancer. FGF19 uniquely binds to FGF receptor 4 (FGFR4). Our previous study has shown that FGF19 transgenic tumors have an activated Wnt-pathway phenotype. Wnt signaling is implicated in initiating or promoting FGF signaling in various cell types and organs. In this study, we examined whether FGF19 or inhibition of FGF19 affects the beta-catenin signaling pathway using human colon cancer cell lines (HCT116, Colo201). Our results show that FGF19 increases tyrosine phosphorylation of beta-catenin and causes loss of beta-catenin-E-cadherin binding. FGF19 increases p-GSK3beta and active beta-catenin levels and anti-FGF19 antibody (1A6) treatment abrogates this effect of FGF19. Anti-FGF19 antibody treatment increases S33/S37/T41 phosphorylation and ubiquitination of beta-catenin. Ion-trap mass spectrometric analysis confirmed that 1A6 increases phosphorylation of beta-catenin in the NH(2) terminus. Using HCT116-paired beta-catenin knockout cells, we show that FGF19 induces TCF/LEF reporter activity in parental (WT/Delta45) and in WT/--but not in mutant (-/Delta45) cells, and that inhibition of endogenous FGF19 reduces this reporter activity, indicating that wild-type beta-catenin is accessible for modulation. FGFR4 knockdown using inducible short hairpin RNA significantly reduces the colony-forming ability in vitro and tumor growth in vivo. Although cleaved caspase-3 immunoreactivity remains unchanged, the number of ki67-positive nuclei is reduced in FGFR4 knockdown tumor xenograft tissues. Consistent with the reduced beta-catenin activation, Taqman analyses show that FGF19/FGFR4 inhibition reduced beta-catenin target gene (cyclin D1, CD44, c-jun, Cox-2, UPAR) expression. These findings highlight that FGF19/FGFR4 cross-talk with beta-catenin and that pathway intervention reduces tumor growth.