Transcriptional regulation of Wnt inhibitory factor-1 by Miz-1/c-Myc

High DNAJA4 expression correlates with poor survival outcomes in breast cancer

Background: DNAJA4 (PRO1472) is a heat shock protein that has been associated with several types of cancers, including breast cancer. We aimed to reveal the protein expression, clinical outcomes, and regulatory mechanisms of DNAJA4 gene in breast cancer by employing tissue microarrays, transcriptomic datasets, and in-silico tools.

Methods: DNAJA4 protein expression and its clinical implications were evaluated by immunohistochemistry assay (normals = 32; tumors = 121). RNA-seq and DNA microarray datasets were analyzed by using breast cancer gene-expression miner (Bc-GenExMiner v4.8) to estimate the survival probabilities of breast cancer patients. DNAJA4 promoter methylation level was analyzed in clinical samples by UALCAN in-silico tool (normals = 97; tumors = 793).

Results: DNAJA4 protein expression is significantly high in clinical breast cancer samples compared to the normal samples (P = 0.016). High DNAJA4 mRNA expression is correlated with poor overall survival (OS), disease-free survival (DFS), and distant metastasis-free survival (DMFS) in breast cancer patients (P < 0.05). Mutations or copy number variations of DNAJA4 are uncommon in clinical samples. Reduced promoter methylation was observed in clinical breast cancer samples.

Conclusion: We suggest DNAJA4 expression as a new biomarker candidate for breast cancer. Promoter hypomethylation could be an important epigenetic factor in the upregulation of DNAJA4 expression in breast cancer.

Epigenetic alterations induced by genotoxic occupational and environmental human chemical carcinogens: An update of a systematic literature review

Epigenetic alterations, such as changes in DNA methylation, histones/chromatin structure, nucleosome positioning, and expression of non-coding RNAs, are recognized among key characteristics of carcinogens; they may occur independently or concomitantly with genotoxic effects. While data on genotoxicity are collected through standardized guideline tests, data collected on epigenetic effects is far less uniform. In 2016, we conducted a systematic review of published studies of genotoxic carcinogens that reported epigenetic endpoints to better understand the evidence for epigenetic alterations of human carcinogens, and the potential association with genotoxic endpoints. Since then, the number of studies of epigenetic effects of chemicals has nearly doubled. This review stands as an update on epigenetic alterations induced by occupational and environmental human carcinogens that were previously and recently classified as Group 1 by the International Agency for Research on Cancer. We found that the evidence of epigenetic effects remains uneven across agents. Studies of DNA methylation are most abundant, while reports concerning effects on non-coding RNA have increased over the past 5 years. By contrast, mechanistic toxicology studies of histone modifications and chromatin state alterations remain few. We found that most publications of epigenetic effects of carcinogens were studies in exposed humans or human cells. Studies in rodents represent the second most common species used for epigenetic studies in toxicology, in vivo exposures being the most predominant. Future studies should incorporate dose- and time-dependent study designs and also investigate the persistence of effects following cessation of exposure, considering the dynamic nature of most epigenetic alterations.

Recognition of DNA Methylation Molecular Features for Diagnosis and Prognosis in Gastric Cancer

Background: The management of gastric cancer (GC) still lacks tumor markers with high specificity and sensitivity. The goal of current research is to find effective diagnostic and prognostic markers and to clarify their related mechanisms.

Methods: In this study, we integrated GC DNA methylation data from publicly available datasets obtained from TCGA and GEO databases, and applied random forest and LASSO analysis methods to screen reliable differential methylation sites (DMSs) for GC diagnosis. We constructed a diagnostic model of GC by logistic analysis and conducted verification and clinical correlation analysis. We screened credible prognostic DMSs through univariate Cox and LASSO analyses and verified a prognostic model of GC by multivariate Cox analysis. Independent prognostic and biological function analyses were performed for the prognostic risk score. We performed TP53 correlation analysis, mutation and prognosis analysis on eleven-DNA methylation driver gene (DMG), and constructed a multifactor regulatory network of key genes.

Results: The five-DMS diagnostic model distinguished GC from normal samples, and diagnostic risk value was significantly correlated with grade and tumor location. The prediction accuracy of the eleven-DMS prognostic model was verified in both the training and validation datasets, indicating its certain potential for GC survival prediction. The survival rate of the high-risk group was significantly lower than that of the low-risk group. The prognostic risk score was an independent risk factor for the prognosis of GC, which was significantly correlated with N stage and tumor location, positively correlated with the VIM gene, and negatively correlated with the CDH1 gene. The expression of CHRNB2 decreased significantly in the TP53 mutation group of gastric cancer patients, and there were significant differences in CCDC69, RASSF2, CHRNB2, ARMC9, and RPN1 between the TP53 mutation group and the TP53 non-mutation group of gastric cancer patients. In addition, CEP290, UBXN8, KDM4A, RPN1 had high frequency mutations and the function of eleven-DMG mutation related genes in GC patients is widely enriched in multiple pathways.

Conclusion: Combined, the five-DMS diagnostic and eleven-DMS prognostic GC models are important tools for accurate and individualized treatment. The study provides direction for exploring potential markers of GC.

Targeting Myc Interacting Proteins as a Winding Path in Cancer Therapy

MYC, as a well-known oncogene, plays essential roles in promoting tumor occurrence, development, invasion and metastasis in many kinds of solid tumors and hematologic neoplasms. In tumors, the low expression and the short half-life of Myc are reversed, cause tumorigenesis. And proteins that directly interact with different Myc domains have exerted a significant impact in the process of Myc-driven carcinogenesis. Apart from affecting the transcription of Myc target genes, Myc interaction proteins also regulate the stability of Myc through acetylation, methylation, phosphorylation and other post-translational modifications, as well as competitive combination with Myc. In this review, we summarize a series of Myc interacting proteins and recent advances in the related inhibitors, hoping that can provide new opportunities for Myc-driven cancer treatment.

Radiosensitizing effects of c‑myc gene knockdown‑induced G2/M phase arrest by intrinsic stimuli via the mitochondrial signaling pathway

Osteosarcoma is the most common primary malignant bone tumor in children and adolescents and its long‑term survival rate has stagnated in the past decades. Previous studies have shown that tumors in the G2/M phase are more sensitive to radiotherapy. The proto‑oncogene c‑myc is a transformed member of the myc family and c‑myc‑interacting zinc finger protein‑1 (Miz‑1) is a poly‑Cys2His2 zinc finger (ZF) activator of cell cycle regulator genes, such as the cyclin‑dependent kinase inhibitor p21. C‑myc can repress the expression of p21 by binding to Miz‑1 and abolishing the interaction between Miz‑1 and its co‑activators, which induces G2/M phase arrest. Therefore, the present study investigated the radiosensitizing effects of the c‑myc gene and the sensitizing apoptosis pathway, aiming to identify a more effective combination radiotherapy treatment for osteosarcoma. The present study demonstrated that the c‑myc gene was overexpressed in osteosarcoma cells compared to osteoblasts. Following inhibition of c‑myc gene expression in osteosarcoma cells, tumor proliferation was significantly hindered after inducing G2/M phase arrest via regulating G2/M phase‑associated proteins. Additionally, it was revealed that inhibiting c‑myc gene expression combined with radiotherapy could significantly increase the apoptosis rate of osteosarcoma cells via the mitochondrial signaling pathway. In summary, the present study verified the radiosensitizing effects of c‑myc gene knockdown‑induced G2/M phase arrest, which was achieved by intrinsic stimuli through the mitochondrial signaling pathway.

miR-145 promotes miR-133b expression through c-myc and DNMT3A-mediated methylation in ovarian cancer cells

Ovarian cancer presents as malignant tumors in the female reproductive system with high mortality. MicroRNAs are involved in the progression of ovarian cancer; however, the regulatory relationship among miRs remains unclear. In our study, we verified that both miR-145 and miR-133b messenger RNA (mRNA) levels in ovarian cancer tissues were lower than in normal ovarian tissues, and their mRNA level in serum of patients with ovarian cancer was reduced. We demonstrated miR-145 targeted c-myc, and c-myc interacted physically with DNMT3A in ovarian cancer cells. We confirmed that c-myc recruited DNMT3A to the miR-133b promoter. miR-133b overexpression also inhibited target gene PKM2 expression along with the Warburg effect. Our results indicate that miR-145 inhibited the Warburg effect through miR-133b/PKM2 pathways, which may improve approaches to ovarian cancer diagnosis and treatment.

Temporal control of Wnt signaling is required for habenular neuron diversity and brain asymmetry

Precise temporal coordination of signaling processes is pivotal for cellular differentiation during embryonic development. A vast number of secreted molecules are produced and released by cells and tissues, and travel in the extracellular space. Whether they induce a signaling pathway and instruct cell fate, however, depends on a complex network of regulatory mechanisms, which are often not well understood. The conserved bilateral left-right asymmetrically formed habenulae of the zebrafish are an excellent model for investigating how signaling control facilitates the generation of defined neuronal populations. Wnt signaling is required for habenular neuron type specification, asymmetry and axonal connectivity. The temporal regulation of this pathway and the players involved have, however, have remained unclear. We find that tightly regulated temporal restriction of Wnt signaling activity in habenular precursor cells is crucial for the diversity and asymmetry of habenular neuron populations. We suggest a feedback mechanism whereby the tumor suppressor Wnt inhibitory factor Wif1 controls the Wnt dynamics in the environment of habenular precursor cells. This mechanism might be common to other cell types, including tumor cells.

Methylation of tumour suppressor genes associated with thyroid cancer

BACKGROUND

Thyroid carcinoma is the most common endocrine malignancy worldwide. Changes in DNA methylation can cause silencing of normally active genes, especially tumour suppressor genes (TSG) or activation of normally silent genes.

OBJECTIVE

The aim of this study is to evaluate the degree of promoter methylation for a panel of markers for thyroid neoplasms and to establish their relationship with thyroid oncogenesis.

METHODS

To generate a comprehensive DNA methylation signature of TSGs involved in thyroid neoplasia, we use Human TSG EpiTect Methyl II Signature PCR Array-Qiagen for 24 samples (follicular adenomas and papillary thyroid carcinomas) compared with normal thyroid tissue. We extended the evaluation for three TSGs (TP73, WIF1, PDLIM4) using qMS-PCR. Statistical analysis was performed with GraphPad Prism.

RESULTS

We noted four important genes NEUROG1, ESR1, RUNX3, MLH1, which presented methylated promoter in tumour samples compared to normal. We found new characteristic of thyroid tumours: methylation of TP73, WIF1 and PDLIM4 TSGs, which can contribute to thyroid neoplasia. A significant correlation between BRAF V600E mutation and RET/PTC rearrangements with TIMP3 and CDH13, RARB methylation, respectively was observed.

CONCLUSIONS

TSGs promoter hypermethylation is a hallmark of cancer and a test that uses methylation quantification method is suitable for diagnosis and prognosis of thyroid cancer.

DKK1 promotes hepatocellular carcinoma inflammation, migration and invasion: Implication of TGF-β1

Dickkopf-1 (DKK1), an inhibitor of the most frequently impaired signaling pathway in hepatocellular carcinoma (HCC), the Wnt/beta-catenin pathway, seems to fulfill contradictory functions in the process of tumorigenesis, acting either as an oncogenic promoter of metastasis or as a tumor suppressor. Elevated serum levels of DKK1 have been reported in HCC; however, little is known about its functional significance. In the current study, we treated HepG2/C3A and PLC/PRF/5 with the recombinant protein DKK1. Cytotoxicity was first determined by the WST-8 assay. AFP expression was measured at both the mRNA and protein levels. Expression of the oncogenes MYC, CCND1, hTERT, and MDM2 and the tumor suppressor genes TP53, P21 and RB was assessed. Western blot analysis of non-phosphorylated ẞ-catenin and Sanger sequencing were performed to explain the functional differences between the two cell lines. Subsequently, inflammation, migration and invasion were evaluated by qPCR, ELISA, the Boyden chamber assay, zymography, and MMP-2 and MMP-9 western blot analysis. Knockdown of DKK1 and TGF-β1 were also performed. Our results suggest that DKK1 exerts an oncogenic effect on HepG2/C3A cell line by upregulating the expression of oncogenes and downregulating that of tumor suppressor genes, whereas the opposite effect was demonstrated in PLC/PRF/5 cells. This differential impact of DKK1 can be explained by the mutations that affect the canonical Wnt pathway that were detected in exon 3 of the CTNNB1 gene in the HepG2 cell line. We further confirmed that DKK1 promotes inflammation, tumor invasion and migration in both cell types. The canonical pathway was not responsible for the DKK1 proinvasive effect, as indicated by the active ẞ-catenin levels in the two cell lines upon DKK1 treatment. Interestingly, knockdown of TGF-β1 negatively affected the DKK1 proinvasive effect. Taken together, DKK1 appears to facilitate tumor invasion and migration through TGF- β1 by remodeling the tumor microenvironment and inducing inflammation. This finding endorses the relevance of TGF-β1 as a therapeutic target.

Analysis of DNA methylation in cancer: location revisited

Changes in DNA methylation in cancer have been heralded as promising targets for the development of powerful diagnostic, prognostic, and predictive biomarkers. Despite the existence of more than 14,000 scientific publications describing DNA methylation-based biomarkers and their clinical associations in cancer, only 14 of these biomarkers have been translated into a commercially available clinical test. Methodological and experimental obstacles are both major causes of this disparity, but the genomic location of a DNA methylation-based biomarker is an intrinsic and essential property that also has an important and often overlooked role. Here, we examine the importance of the location of DNA methylation for the development of cancer biomarkers, and take a detailed look at the genomic location and other relevant characteristics of the various biomarkers with commercially available tests. We also emphasize the value of publicly available databases for the development of DNA methylation-based biomarkers and the importance of accurate reporting of the full methodological details of research findings.

MYC and DNMT3A-mediated DNA methylation represses microRNA-200b in triple negative breast cancer

Triple‐negative breast cancer (TNBC) is the most aggressive breast cancer subtype with a poor prognosis. The microRNA‐200 (miR‐200) family has been associated with breast cancer metastasis. However, the epigenetic mechanisms underlying miR‐200b repression in TNBC are not fully elucidated. In this study, we found that MYC proto‐oncogene, bHLH transcription factor (MYC) and DNA methyltransferase 3A (DNMT3A) were highly expressed in TNBC tissues compared with other breast cancer subtypes, while miR‐200b expression was inhibited significantly. We demonstrated that MYC physically interacted with DNMT3A in MDA‐MB‐231 cells. Furthermore, we demonstrated that MYC recruited DNMT3A to the miR‐200b promoter, resulting in proximal CpG island hypermethylation and subsequent miR‐200b repression. MiR‐200b directly inhibited DNMT3A expression and formed a feedback loop in TNBC cells. MiR‐200b overexpression synergistically repressed target genes including zinc‐finger E‐box‐binding homeobox factor 1, Sex determining region Y‐box 2 (SOX2), and CD133, and inhibited the migration, invasion and mammosphere formation of TNBC cells. Our findings reveal that MYC can collaborate with DNMT3A on inducing promoter methylation and miR‐200b silencing, and thereby promotes the epithelial to mesenchymal transition and mammosphere formation of TNBC cells.

A miR-26a/E2F7 feedback loop contributes to tamoxifen resistance in ER-positive breast cancer

Tamoxifen (TAM) resistance is a substantial challenge in the treatment of estrogen receptor (ER)-positive breast cancer. Previous studies have revealed an important role of microRNA (miRNA/miR)-26a in TAM resistance in breast cancer. However, the mechanism underlying the regulatory effects of miR-26a on TAM resistance remains to be elucidated. The expression levels of miR-26a in ER-positive breast cancer were detected by reverse transcription-quantitative polymerase chain reaction. E2F transcription factor 7 (E2F7) and MYC proto-oncogene, bHLH transcription factor (MYC) levels were detected by western blotting. The present study demonstrated that miR-26a expression was reduced in ER-positive breast cancer compared with in normal breast tissues, whereas E2F7 expression was significantly elevated. Furthermore, an inverse correlation between miR-26a and E2F7 expression was detected in ER-positive breast cancer. The results indicated that miR-26a directly inhibited E2F7 expression through translational inhibition and indirectly inhibited MYC expression partly via E2F7 repression. E2F7, in turn, decreased miR-26a expression via MYC-induced transcriptional inhibition of miRNAs. Furthermore, transfection with miR-26a mimics increased the expression of its host genes (CTD small phosphatase like and CTD small phosphatase 2), whereas ectopic E2F7 expression abrogated the effects of miR-26a. These findings indicated that miR-26a and E2F7 may form a double-negative feedback loop, resulting in downregulation of miR-26a and upregulation of E2F7 in ER-positive breast cancer. Both miR-26a knockdown and E2F7 overexpression conferred resistance to TAM in MCF-7 cells. Conversely, miR-26a overexpression and E2F7 silencing resensitized MCF-7 resistant cells to TAM. These findings revealed that a feedback loop between miR-26a and E2F7 may promote TAM resistance in ER-positive breast cancer.

TRIM59 induces epithelial-to-mesenchymal transition and promotes migration and invasion by PI3K/AKT signaling pathway in medulloblastoma

Medulloblastoma is the most common malignant brain tumor in children. Despite remarkable advances over previous decades, the long-term survival of patients with medulloblastoma remains poor due to the frequent metastatic nature of this malignancy. The aim of the present study was to examine the role of tripartite motif containing 59 (TRIM59) in cell metastasis in medulloblastoma. It was initially demonstrated that TRIM59 expression was significantly increased in clinical medulloblastoma tissues compared with adjacent non-cancerous tissues and differentially expressed in a series of medulloblastoma cell lines. The knockdown of TRIM59 in D283 cells resulted in epithelial-to-mesenchymal transition (EMT), and decreased cell migratory and invasive capacities. By contrast, the overexpression of TRIM59 in Daoy cells was able to inhibit the EMT process and increase migratory and invasive capacities of the cells. Notably, the knockdown of TRIM59 was able to decrease the protein level of matrix metalloproteinase (MMP)-2 without altering the levels of MMP-9, and conversely the overexpression of TRIM59 was able to increase the protein level of MMP-2. Importantly, the downregulation of TRIM59 in D283 cells was able to inhibit the levels of phosphorylated (p)-AKT (Ser473), glycogen synthase kinase 3 β(GSK3β; Ser9) and phosphoinositide 3-kinase (PI3K) p85 (Tyr458) without altering the levels of total protein. The data from the present study suggest that TRIM59 induces epithelial-to-mesenchymal transition and promotes migration and invasion by PI3K/AKT signaling pathway in medulloblastoma. This data may provide novel insight into tumor metastasis and pave the way for the development of therapeutic strategies for the treatment of medulloblastoma in the clinic.

In Utero Exposure to a High-Fat Diet Programs Hepatic Hypermethylation and Gene Dysregulation and Development of Metabolic Syndrome in Male Mice

Exposure to a high-fat (HF) diet in utero is associated with increased incidence of cardiovascular disease, diabetes, and metabolic syndrome later in life. However, the molecular basis of this enhanced susceptibility for metabolic disease is poorly understood. Gene expression microarray and genome-wide DNA methylation analyses of mouse liver revealed that exposure to a maternal HF milieu activated genes of immune response, inflammation, and hepatic dysfunction. DNA methylation analysis revealed 3360 differentially methylated loci, most of which (76%) were hypermethylated and distributed preferentially to hotspots on chromosomes 4 [atherosclerosis susceptibility quantitative trait loci (QTLs) 1] and 18 (insulin-dependent susceptibility QTLs 21). Interestingly, we found six differentially methylated genes within these hotspot QTLs associated with metabolic disease that maintain altered gene expression into adulthood (Arhgef19, Epha2, Zbtb17/Miz-1, Camta1 downregulated; and Ccdc11 and Txnl4a upregulated). Most of the hypermethylated genes in these hotspots are associated with cardiovascular system development and function. There were 140 differentially methylated genes that showed a 1.5-fold increase or decrease in messenger RNA levels. Many of these genes play a role in cell signaling pathways associated with metabolic disease. Of these, metalloproteinase 9, whose dysregulation plays a key role in diabetes, obesity, and cardiovascular disease, was upregulated 1.75-fold and hypermethylated in the gene body. In summary, exposure to a maternal HF diet causes DNA hypermethylation, which is associated with long-term gene expression changes in the liver of exposed offspring, potentially contributing to programmed development of metabolic disease later in life.

Knockdown of tripartite motif-59 inhibits the malignant processes in human colorectal cancer cells

The aim of the present study was to clarify the clinical implication and functional role of tripartite motif-59 (TRIM59) in colorectal carcinoma (CRC) and explore the underlying mechanism of aberrant high expression of TRIM59 in cancer. We validated that TRIM59 was upregulated in CRC samples, and also demonstrated that its upregulation was associated with advanced tumor stage of CRC patients; and its high expression indicated shorter overall survival and faster recurrence. Knockdown of TRIM59 significantly inhibited cell proliferation, migration and invasion. Cell cycle analysis showed that TRIM59-depleted cells accumulated in S-phase. In addition, the cell cycle regulators CDC25C, cyclin B1 and cyclin D1 were decreased by TRIM59 siRNA mediated knockdown. Furthermore, the depletion of TRIM59 promoted apoptosis in cell culture as indicated by the cleavage of caspase-3 and PARP when TRIM59 was depleted. These results suggested that TRIM59 is upregulated in human colorectal tumors compared with non-tumor tissues. The level of TRIM59 is correlated with malignant features of CRC and may serve as potential therapeutic and preventive strategies for CRC.

Spi-B-Mediated Silencing of Claudin-2 Promotes Early Dissemination of Lung Cancer Cells from Primary Tumors

Dissociation from epithelial sheets and invasion through the surrounding stroma are critical early events during epithelial cancer metastasis. Here we find that a lymphocyte lineage-restricted transcription factor, Spi-B, is frequently expressed in human lung cancer tissues. The Spi-B-expressing cancer cells coexpressed vimentin but repressed E-cadherin and exhibited invasive behavior. Increased Spi-B expression was associated with tumor grade, lymphatic metastasis, and short overall survival. Mechanistically, Spi-B disrupted intercellular junctions and enhanced invasiveness by reconfiguring the chromatin structure of the tight junction gene claudin-2 (CLDN2) and repressing its transcription. These data suggest that Spi-B participates in mesenchymal invasion, linking epithelial cancer metastasis with a lymphatic transcriptional program. Cancer Res; 77(18); 4809-22. ©2017 AACR.

Electroacupuncture stimulation at CV4 prevents ovariectomy-induced osteoporosis in rats via Wnt-β-catenin signaling

The present study aimed to investigate the effect of electroacupuncture stimulation at CV4 (also termed Guanyuan) on femoral osteocalcin also termed bone gla protein (BGP), alkaline phosphatase (ALP), bone mineral density (BMD) and biomechanics, as well as the Wnt‑β‑catenin signaling pathway in rats with postmenopausal osteoporosis. Female Sprague‑Dawley rats (4.5‑months old) were randomly divided into sham, Ovx, CV4 and mock groups (n=10/group). With the exception of those in the sham group, the rats were ovariectomized to induce postmenopausal osteoporosis. The rats in the CV4 and mock groups were given electroacupuncture at CV4 and non‑acupoint, respectively. The rats in the Ovx model and sham groups underwent identical fixing procedures, but did not undergo electroacupuncture. Following treatment, hematoxylin and eosin staining was used to observe morphological changes in the left femoral trabecular bone, and a three‑point‑bending test was used to analyze femur biomechanics and determine the BMD. In addition, an enzyme‑linked immunosorbent assay was used to measure the serum levels of ALP/BGP and reverse transcription‑quantitative polymerase chain reaction was used detect the expression levels of Wnt3a, β‑catenin and Runx2. In the present study, it was demonstrated that electroacupuncture at CV4 significantly improved the osteoporotic morphological changes that occurred in the ovariectomized rats, increased serum ALP and BGP levels, enhanced the maximum and fracture loads, increased BMD (P<0.01), and activated the Wnt‑β‑catenin signaling pathway. These findings demonstrated that electroacupuncture stimulation at CV4 affected bone formation and promoted bone metabolism in rats with postmenopausal osteoporosis, possibly by activating the Wnt‑β‑catenin signaling pathway.

The class-specific BCR tonic signal modulates lymphomagenesis in a c-myc deregulation transgenic model

Deregulation of c-myc by translocation onto immunoglobulin (Ig) loci can promote B cell malignant proliferations with phenotypes as diverse as acute lymphoid leukemia, Burkitt lymphoma, diffuse large B cell lymphoma, myeloma… The B cell receptor (BCR) normally providing tonic signals for cell survival and mitogenic responses to antigens, can also contribute to lymphomagenesis upon sustained ligand binding or activating mutations. BCR signaling varies among cell compartments and BCR classes. For unknown reasons, some malignancies associate with expression of either IgM or class-switched Ig. We explored whether an IgA BCR, with strong tonic signaling, would affect lymphomagenesis in c-myc IgH 3′RR transgenic mice prone to lymphoproliferations. Breeding c-myc transgenics in a background where IgM expression was replaced with IgA delayed lymphomagenesis. By comparison to single c-myc transgenics, lymphomas from double mutant animals were more differentiated and less aggressive, with an altered transcriptional program. Larger tumor cells more often expressed CD43 and CD138, which culminated in a plasma cell phenotype in 10% of cases. BCR class-specific signals thus appear to modulate lymphomagenesis and may partly explain the observed association of specific Ig classes with human B cell malignancies of differential phenotype, progression and prognosis.

Wnt/β-catenin signaling regulates Dental Pulp Stem Cells' responses to pulp injury by resinous monomers

OBJECTIVES

Aim of this study was to investigate whether Dental Pulp Stem Cells-DPSCs responses to pulp injury caused by resinous monomers is be mediated through activation of Wnt/β-catenin signaling.

METHODS

DPSCs cultures were established from third molars of healthy donors and characterized for stem cell markers with flow cytometry. Cells were exposed to TEGDMA (T: 0.5-2mM) with or without presence of the Wnt-1 ligand (W:25-100ng/ml) or the GSK3β inhibitor Lithium (L:1-10mM), used both as activators of Wnt/β-catenin signaling. Cell viability was evaluated by MTT assay, cell cycle profiles by flow cytometry and expression of key molecules of Wnt/β-catenin signaling by Real-time PCR and Western Blot.

RESULTS

DPSC exposure to TEGDMA caused a concentration-dependent cytotoxicity, accompanied by G1 arrest at lower and G2/M arrest at higher concentrations or after prolonged exposure. Lithium caused a dual effect, by stimulating/inhibiting cell proliferation at lower/higher concentrations respectively and causing a G2/M arrest in a concentration-dependent manner. Wnt signaling could be activated in DPSCs after Lithium or Wnt-1 treatment, as shown by accumulation of β-catenin, its translocation into the nucleus and enhanced expression of key pathway players, like LEF1 and Cyclin D1. Importantly, exposure to TEGDMA caused a more pronounced activation of the pathway, whereas cumulative effects were observed after T/L or T/W co-treatment, indicating a very strong activation of Wnt signaling after treatment of already "activated" (by Lithium or Wnt-1) cells with TEGDMA.

SIGNIFICANCE

These findings highlight the important role of Wnt canonical signaling in pulp repair responses to common injuries.

TRIM13 is a negative regulator of MDA5-mediated type I interferon production

Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are essential intracellular detectors of viral RNA. They contribute to the type I interferon (IFN) response that is crucial for host defense against viral infections. Given the potent antiviral and proinflammatory activities elicited by the type I IFNs, induction of the type I IFN response is tightly regulated. Members of the tripartite motif (TRIM) family of proteins have recently emerged as key regulators of antiviral immunity. We show that TRIM13, an E3 ubiquitin ligase, is expressed in immune cells and is upregulated in bone marrow-derived macrophages upon stimulation with inducers of type I IFN. TRIM13 interacts with MDA5 and negatively regulates MDA5-mediated type I IFN production in vitro, acting upstream of IFN regulatory factor 3. We generated Trim13(-/-) mice and show that upon lethal challenge with encephalomyocarditis virus (EMCV), which is sensed by MDA5, Trim13(-/-) mice produce increased amounts of type I IFNs and survive longer than wild-type mice. Trim13(-/-) murine embryonic fibroblasts (MEFs) challenged with EMCV or poly(I · C) also show a significant increase in beta IFN (IFN-β) levels, but, in contrast, IFN-β responses to the RIG-I-detected Sendai virus were diminished, suggesting that TRIM13 may play a role in positively regulating RIG-I function. Together, these results demonstrate that TRIM13 regulates the type I IFN response through inhibition of MDA5 activity and that it functions nonredundantly to modulate MDA5 during EMCV infection.

IMPORTANCE

The type I interferon (IFN) response is crucial for host defense against viral infections, and proper regulation of this pathway contributes to maintaining immune homeostasis. Retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are intracellular detectors of viral RNA that induce the type I IFN response. In this study, we show that expression of the gene tripartite motif 13 (Trim13) is upregulated in response to inducers of type I IFN and that TRIM13 interacts with both MDA5 and RIG-I in vitro. Through the use of multiple in vitro and in vivo model systems, we show that TRIM13 is a negative regulator of MDA5-mediated type I IFN production and may also impact RIG-I-mediated type I IFN production by enhancing RIG-I activity. This places TRIM13 at a key junction within the viral response pathway and identifies it as one of the few known modulators of MDA5 activity.

The role of MIZ-1 in MYC-dependent tumorigenesis

A hallmark of MYC-transformed cells is their aberrant response to antimitogenic signals. Key examples include the inability of MYC-transformed cells to arrest proliferation in response to antimitogenic signals such as TGF-β or DNA damage and their inability to differentiate into adipocytes in response to hormonal stimuli. Given the plethora of antimitogenic signals to which a tumor cell is exposed, it is likely that the ability to confer resistance to these signals is central to the transforming properties of MYC in vivo. At the same time, the inability of MYC-transformed cells to halt cell-cycle progression on stress may establish a dependence on mutations that impair or disable apoptosis. We propose that the interaction of MYC with the zinc finger protein MIZ-1 mediates resistance to antimitogenic signals. In contrast to other interactions of MYC, there is currently little evidence that MIZ-1 associates with MYC in normal, unperturbed cells. The functional interaction of both proteins becomes apparent at oncogenic expression levels of MYC and association with MIZ-1 mediates both oncogenic functions of MYC as well as tumor-suppressive responses to oncogenic levels of MYC.

Functional epigenetic approach identifies frequently methylated genes in Ewing sarcoma

Using a candidate gene approach we recently identified frequent methylation of the RASSF2 gene associated with poor overall survival in Ewing sarcoma (ES). To identify effective biomarkers in ES on a genome-wide scale, we used a functionally proven epigenetic approach, in which gene expression was induced in ES cell lines by treatment with a demethylating agent followed by hybridization onto high density gene expression microarrays. After following a strict selection criterion, 34 genes were selected for expression and methylation analysis in ES cell lines and primary ES. Eight genes (CTHRC1, DNAJA4, ECHDC2, NEFH, NPTX2, PHF11, RARRES2, TSGA14) showed methylation frequencies of>20% in ES tumors (range 24-71%), these genes were expressed in human bone marrow derived mesenchymal stem cells (hBMSC) and hypermethylation was associated with transcriptional silencing. Methylation of NPTX2 or PHF11 was associated with poorer prognosis in ES. In addition, six of the above genes also showed methylation frequency of>20% (range 36-50%) in osteosarcomas. Identification of these genes may provide insights into bone cancer tumorigenesis and development of epigenetic biomarkers for prognosis and detection of these rare tumor types.

Deregulation of Wnt/β-catenin signaling through genetic or epigenetic alterations in human neuroendocrine tumors

Carcinoid tumors are rare neuroendocrine tumors (NETs) that are increasing in incidence. Mutation and altered expression of Wnt/β-catenin signaling components have been described in many tumors but have not been well-studied in NETs. Here, we observed accumulation of β-catenin in the cytoplasm and/or nucleus in 25% of clinical NET tissues. By mutational analysis, the mutations of β-catenin (I35S) and APC (E1317Q, T1493T) were identified in NET cells and the tissues. Expression of representative Wnt inhibitors was absent or markedly decreased in BON, a human pancreatic carcinoid cell line; treatment with 5-aza-2'-deoxycytidine (5-aza-CdR) increased expression levels of the Wnt inhibitors. Methylation analyses demonstrated that CpG islands of SFRP-1 and Axin-2 were methylated, whereas the promoters of DKK-1, DKK-3 and WIF-1 were unmethylated in four NET cells. Aberrant methylation of SFRP-1 was particularly observed in most of clinical NET tissues. In addition, the repression of these unmethylated genes was associated with histone H3 lysine 9 dimethylation (H3K9me2) in BON cells. Together, 5-aza-CdR treatment inhibited cell proliferation and decreased the protein levels of H3K9me2 and G9a. Moreover, a novel G9a inhibitor, UNC0638, suppressed BON cell proliferation through inhibition of Wnt/β-catenin pathway. Overexpression of the inhibitory genes, particularly SFRP-1 and WIF-1 in BON cells, resulted in suppression of anchorage-independent growth and inhibition of tumor growth in mice. Our findings suggest that aberrant Wnt/β-catenin signaling, through either mutations or epigenetic silencing of Wnt antagonists, contributes to the pathogenesis and growth of NETs and have important clinical implications for the prognosis and treatment of NETs.

The Wnt signalling pathway is upregulated in an in vitro model of acquired tamoxifen resistant breast cancer

Background

Acquired resistance to Tamoxifen remains a critical problem in breast cancer patient treatment, yet the underlying causes of resistance have not been fully elucidated. Abberations in the Wnt signalling pathway have been linked to many human cancers, including breast cancer, and appear to be associated with more metastatic and aggressive types of cancer. Here, our aim was to investigate if this key pathway was involved in acquired Tamoxifen resistance, and could be targeted therapeutically.

Methods

An in vitro model of acquired Tamoxifen resistance (named TamR) was generated by growing the estrogen receptor alpha (ER) positive MCF7 breast cancer cell line in increasing concentrations of Tamoxifen (up to 5 uM). Alterations in the Wnt signalling pathway and epithelial to mesenchymal transition (EMT) in response to Tamoxifen and treatment with the Wnt inhibitor, IWP-2 were measured via quantitative RT-PCR (qPCR) and TOP/FOP Wnt reporter assays. Resistance to Tamoxifen, and effects of IWP-2 treatment were determined by MTT proliferation assays.

Results

TamR cells exhibited increased Wnt signalling as measured via the TOP/FOP Wnt luciferase reporter assays. Genes associated with both the β-catenin dependent (AXIN2, MYC, CSNK1A1) and independent arms (ROR2, JUN), as well as general Wnt secretion (PORCN) of the Wnt signalling pathway were upregulated in the TamR cells compared to the parental MCF7 cell line. Treatment of the TamR cell line with human recombinant Wnt3a (rWnt3a) further increased the resistance of both MCF7 and TamR cells to the anti-proliferative effects of Tamoxifen treatment. TamR cells demonstrated increased expression of EMT markers (VIM, TWIST1, SNAI2) and decreased CDH1, which may contribute to their resistance to Tamoxifen. Treatment with the Wnt inhibitor, IWP-2 inhibited cell proliferation and markers of EMT.

Conclusions

These data support the role of the Wnt signalling pathway in acquired resistance to Tamoxifen. Further research into the mechanism by which activated Wnt signalling inhibits the effects of Tamoxifen should be undertaken. As a number of small molecules targeting the Wnt pathway are currently in pre-clinical development, combinatorial treatment with endocrine agents and Wnt pathway inhibitors may be a useful therapeutic option in the future for a subset of breast cancer patients.

Promoter hypermethylation-induced transcriptional down-regulation of the gene MYCT1 in laryngeal squamous cell carcinoma

Background

MYCT1, previously named MTLC, is a novel candidate tumor suppressor gene. MYCT1 was cloned from laryngeal squamous cell cancer (LSCC) and has been found to be down-regulated in LSCC; however, the regulatory details have not been fully elucidated.

Methods

Here, we sought to investigate the methylation status of the CpG islands of MYCT1 and mRNA levels by bisulfite-specific PCR (BSP) based on sequencing restriction enzyme digestion, reverse transcription and real-time quantitative polymerase chain reaction (RQ-PCR). The function of specific sites in the proximal promoter of MYCT1 in LSCC was measured by transient transfection, luciferase assays, electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation assay (ChIP).

Results

The results suggested hypermethylation of 12 CpG sites of the promoter in both laryngeal cancer tissues and the laryngeal cancer line Hep-2 cell. The hypermethylation of the site CGCG (−695 to −692), which has been identified as the c-Myc binding site, was identified in laryngeal cancer tissues (59/73) compared to paired mucosa (13/73); in addition, statistical analysis revealed that the methylation status of this site significantly correlated with cancer cell differentiation(p < 0.01). The mRNA level of MYCT1 increased in Hep-2 cells treated with 5-aza-C (p < 0.01). The luciferase activity from mutant transfectants pGL3-MYCT1m (−852/+12, mut-695-C > A, mut-693-C > G) was significantly reduced compared with the wild type pGL3-MYCT1 (−852/+12), while the luciferase activity from wild transfectants pGL3-MYCT1 (−852/+12) rose after 5-aza treatment in Hep-2 cells. Finally, EMSA and ChIP confirmed that the methylation of the CGCG (−695 to −692) site prevented c-Myc from binding of the site and demethylation treatment of the 5′ flanking region of MYCT1 by 5-aza induced the increased occupation of the core promoter by c-Myc (p < 0.01).

Conclusion

In summary, this study concluded that hypermethylation contributed to the transcriptional down-regulation of MYCT1 and could inhibit cancer cell differentiation in LSCC. DNA methylation of the CGCG site (−695 to −692) of MYCT1 altered the promoter activity by interfering with its binding to c-Myc in LSCC. Epigenetic therapy of reactivating MYCT1 by 5-aza should be further evaluated in clinical trails of LSCC.

Genome-wide DNA methylation studies suggest distinct DNA methylation patterns in pediatric embryonal and alveolar rhabdomyosarcomas

Rhabdomyosarcoma is the most common soft-tissue sarcoma in children. While cytogenetic abnormalities have been well characterized in this disease, aberrant epigenetic events such as DNA hypermethylation have not been described in genome-wide studies. We have analyzed the methylation status of 25,500 promoters in normal skeletal muscle, and in cell lines and tumor samples of embryonal and alveolar rhabdomyosarcoma from pediatric patients. We identified over 1,900 CpG islands that are hypermethylated in rhabdomyosarcomas relative to skeletal muscle. Genes involved in tissue development, differentiation, and oncogenesis such as DNAJA4, HES5, IRX1, BMP8A, GATA4, GATA6, ALX3, and P4HTM were hypermethylated in both RMS cell lines and primary samples, implicating aberrant DNA methylation in the pathogenesis of rhabdomyosarcoma. Furthermore, cluster analysis revealed embryonal and alveolar subtypes had distinct DNA methylation patterns, with the alveolar subtype being enriched in DNA hypermethylation of polycomb target genes. These results suggest that DNA methylation signatures may aid in the diagnosis and risk stratification of pediatric rhabdomyosarcoma and help identify new targets for therapy.

Silencing of tumor suppressor genes RASSF1A, SLIT2, and WIF1 by promoter hypermethylation in hereditary breast cancer

Promoter hypermethylation is gaining strength as one of the main mechanisms through which tumor suppressor genes are silenced during tumor progression. Three tumor suppressor genes are frequently found methylated in their promoter, in concordance with absence of expression, RASSF1A, SLIT2, and WIF1. In addition, a previous array-CGH analysis from our group showed that these genes are found in deleted genomic regions observed in hereditary breast cancer tumors. In the present work we analyzed the methylation status of these three tumor suppressor gene promoters in 47 hereditary breast cancer tumors. Promoter methylation status analysis of hereditary breast tumors revealed high methylation frequencies for the three genes (67% RASSF1A, 80% SLIT2, and 72% WIF1). Additionally, the presence of methylated PCR products was associated with absence of protein expression for the three genes and statistically significant for RASSF1A and WIF1. Interestingly, methylation of all the three genes was found in 4 out of 6 grade I invasive ductal carcinoma tumors. Association between RASSF1A methylation and DCIS tumors was found. These results suggest that silencing of these tumor suppressor genes is an early event in hereditary breast cancer, and could be a marker for pre-malignant phenotypes.

A novel multiplex cell viability assay for high-throughput RNAi screening

Cell-based high-throughput RNAi screening has become a powerful research tool in addressing a variety of biological questions. In RNAi screening, one of the most commonly applied assay system is measuring the fitness of cells that is usually quantified using fluorescence, luminescence and absorption-based readouts. These methods, typically implemented and scaled to large-scale screening format, however often only yield limited information on the cell fitness phenotype due to evaluation of a single and indirect physiological indicator. To address this problem, we have established a cell fitness multiplexing assay which combines a biochemical approach and two fluorescence-based assaying methods. We applied this assay in a large-scale RNAi screening experiment with siRNA pools targeting the human kinome in different modified HEK293 cell lines. Subsequent analysis of ranked fitness phenotypes assessed by the different assaying methods revealed average phenotype intersections of 50.7±2.3%–58.7±14.4% when two indicators were combined and 40–48% when a third indicator was taken into account. From these observations we conclude that combination of multiple fitness measures may decrease false-positive rates and increases confidence for hit selection. Our robust experimental and analytical method improves the classical approach in terms of time, data comprehensiveness and cost.

WIF1 is a frequent target for epigenetic silencing in squamous cell carcinoma of the cervix

Aberrant activation of the Wnt/β-catenin signaling axis is a prominent oncogenic mechanism in numerous cancers including cervical cancer. Wnt inhibitory factor-1 (WIF1) is a secreted protein that binds Wnt and antagonizes Wnt activity. While the WIF1 gene is characterized as a target for epigenetic silencing in some tumor types, WIF1 expression has not been examined in human cervical tissue and cervical cancer. Here, we show that WIF1 is unmethylated and its gene product is expressed in normal cervical epithelium and some cultured cervical tumor lines. In contrast, several cervical cancer lines contained dense CpG methylation within the WIF1 gene, and expression of both WIF1 transcript and protein was restored by culturing cells in the presence of the global DNA demethylating agent 5-aza-2'-deoxycytidine. Using single-molecule MAPit methylation footprinting, we observed differences in chromatin structure within the WIF1 promoter region between cell lines that express and those that do not express WIF1, consistent with transcriptional activity and repression, respectively. The WIF1 promoter was aberrantly methylated in ∼60% (10 of 17) high-grade highly undifferentiated squamous cell cervical tumors examined, whereas paired normal tissue showed significantly lower levels of CpG methylation. WIF1 protein was not detectable by immunohistochemistry in tumors with quantitatively high levels of WIF1 methylation. Of note, WIF1 protein was not detectable in two of the seven unmethylated cervical tumors examined, suggesting other mechanisms may contribute WIF1 repression. Our findings establish the WIF1 gene as a frequent target for epigenetic silencing in squamous cell carcinoma of the cervix.

Physiological inhibitors of Wnt signaling

Wnt signaling is crucial for cell proliferation and differentiation. It represents a complex network with mechanisms of self-regulation through positive and negative feedback. Recent increasing interest in this signaling pathway has led to the discovery of many new proteins that down-regulate Wnt activity. Here, we provide a short description of the most important and best-studied inhibitors, group them according to the target molecule within the Wnt cascade, and discuss their clinical potential. Although most of the inhibitors discussed here may also interact with proteins from other signaling pathways, we focus only on their ability to modulate Wnt signaling.

Analysis of promoter CpG island hypermethylation in cancer: location, location, location!

The genetic and epigenetic alterations that underlie cancer pathogenesis are rapidly being identified. This provides novel insights in tumor biology as well as in potential cancer biomarkers. The somatic mutations in cancer genes that have been implemented in clinical practice are well defined and very specific. For epigenetic alterations, and more specifically aberrant methylation of promoter CpG islands, evidence is emerging that these markers could be used for the early detection of cancer as well as prediction of prognosis and response to therapy. However, the exact location of biologically and clinically relevant hypermethylation has not been identified for the majority of methylation markers. The most widely used approaches to analyze DNA methylation are based on primer- and probe-based assays that provide information for a limited number of CpG dinucleotides and thus for only part of the information available in a given CpG island. Validation of the current data and implementation of hypermethylation markers in clinical practice require a more comprehensive and critical evaluation of DNA methylation and limitations of the techniques currently used in methylation marker research. Here, we discuss the emerging evidence on the importance of the location of CpG dinucleotide hypermethylation in relation to gene expression and associations with clinicopathologic characteristics in cancer.