Silencing DNA methyltransferase 1 (DNMT1) inhibits proliferation, metastasis and invasion in ESCC by suppressing methylation of RASSF1A and DAPK

Mechanisms of radiotherapy resistance and radiosensitization strategies for esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is the sixth most common cause of cancer-related mortality worldwide, with more than half of them occurred in China. Radiotherapy (RT) has been widely used for treating ESCC. However, radiation-induced DNA damage response (DDR) can promote the release of cytokines and chemokines, and triggers inflammatory reactions and changes in the tumor microenvironment (TME), thereby inhibiting the immune function and causing the invasion and metastasis of ESCC. Radioresistance is the major cause of disease progression and mortality in cancer, and it is associated with heterogeneity. Therefore, a better understanding of the radioresistance mechanisms may generate more reversal strategies to improve the cure rates and survival periods of ESCC patients. We mainly summarized the possible mechanisms of radioresistance in order to reveal new targets for ESCC therapy. Then we summarized and compared the current strategies to reverse radioresistance.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Epigenetic alterations impede epithelial-mesenchymal transition by modulating centrosome amplification and Myc/RAS axis in triple negative breast cancer cells

Alterations in centrosome proteins may result in centrosome abnormalities such as disorganized spindles and centrosome amplification, leading to aneuploidy and genomic instability. Centrosomes exhibit unique epigenetic properties in which structural or positional information is propagated through somatic lineage by non-genetic pathways. Excessive centrosome amplification in breast cancer is accompanied by efficient clustering and loss of E-cadherin, indicating an important adaptive mechanism of cancer. This study sought to elucidate the effect of epigenetic alterations on centrosome amplification, epithelial-mesenchymal transition (EMT) and apoptosis in triple negative human breast adenocarcinoma derived MDA-MB-231 cell line. The results obtained here show that siRNA mediated silencing of DNMT1 and specific inhibition of HDAC1 & HDAC2 by Tricostatin A (TSA) synergistically inhibit cell proliferation through modulation of centrosome proteins γ-tubulin, TUBGCP2 and pericentrin. In addition, induction of apoptosis was observed by downregulation of Bcl2, upregulation of Bax and activation of PARP cleavage. Inhibition of EMT was confirmed through upregulation of E-cadherin and downregulation of N-cadherin and vimentin. Similarly, downregulation of Myc, RAS and CDK2, which plays important roles in proliferation and survival, was observed. Nuclear protein analysis revealed downregulation in the nuclear translocation of E2F1, which regulates centrosome amplification and metastasis in breast cancer. In conclusion, this study confirmed the role of epigenetic regulators in centrosome amplification and suggests that inhibition of DNA methylation and histone deacetylation-mediated chromatin remodelling synergistically disrupt EMT through modulation of centrosome amplification and Myc/RAS axis to potentiate apoptosis and attenuate cell proliferation in triple negative breast cancer cells.

Pleomorphic Adenoma of the Salivary Glands and Epithelial–Mesenchymal Transition

Pleomorphic adenoma (PA) is a localized tumor that presents pleomorphic or mixed characteristics of epithelial origin and is interwoven with mucoid tissue, myxoid tissue, and chondroid masses. The literature reported that PA most often occurs in adults aged 30–60 years and is a female predilection; the exact etiology remains unclear. Epithelial–mesenchymal transition (EMT) is the transdifferentiation of stationary epithelial cells primarily activated by a core set of transcription factors (EMT-TFs) involved in DNA repair and offers advantages under various stress conditions. Data have suggested that EMTs represent the basic principle of tissue heterogeneity in PAs, demonstrating the potential of adult epithelial cells to transdifferentiate into mesenchymal cells. It has also been reported that multiple TFs, such as TWIST and SLUG, are involved in EMT in PA and that SLUG could play an essential role in the transition from myoepithelial to mesenchymal cells. Given this background, this review aims to summarize and clarify the involvement of EMT in the development of PA, chondrocyte differentiation, and malignant transformation to contribute to the fundamental elucidation of the mechanisms underlying EMT.

DNMT1-mediated demethylation of lncRNA MEG3 promoter suppressed breast cancer progression by repressing Notch1 signaling pathway

Breast carcinoma is one of the common causes of cancer-related mortality in women. Maternally expressed gene 3 (MEG3), a lncRNA located at 14q32, can be involved in carcinogenesis. In this study, we discovered that MEG3 was downregulated by CpG hypermethylation within its gene promoter. Functionally, treatment of breast cancer cells with the DNA methylation inhibitor 5-AzadC as well as silencing of DNA methyltransferase-1 (DNMT1) could decrease the abnormal hypermethylation of the MEG3 promoter, reverse MEG3 expression, inhibit cell proliferation and promote cell apoptosis. In addition, we found that MEG3 expression was negatively correlated with DNMT1. Mechanistically, MEG3 knockdown combined with 5-AzadC or sh-DNMT1 treatment restored the expression of Notch1 receptor, leading to the Notch1 pathway activation, and promoted the progression of epithelial mesenchymal transformation (EMT). Finally, the mice tumor model experiments showed that DNMT1 knockdown can increase MEG3 expression and inhibit tumor growth. Collectively, our findings uncovered that DNMT1-mediated MEG3 demethylation leads to MEG3 upregulation, which in turn inhibits the Notch1 pathway and EMT process in breast cancer.

Low-dose cadmium exposure facilitates cell proliferation by promoter hypermethylation of RASSF1A and DAPK1 genes

Cadmium (Cd) at low concentrations has a potential to promote cell proliferation. However, the molecular mechanisms of Cd-induced proliferation are not well understood. Here, we reported that Cd (0-500 nM) significantly promoted the proliferation of HepG2 cells as demonstrated by elevated cell viability, more EdU-positive cells and increased gene expression of KI-67 and COX-2. Meanwhile, the gene expression of DNA methyltransferases was found to be elevated while that of tumor suppressor genes DAPK1 and RASSF1A were decreased under Cd exposure. Correspondingly, the methylation level of promoters in DAPK1 and RASSF1A were increased. Specifically, the CpG sites at -461 (Chr3:50, 374, 481) of RASSF1A promoter, and that at -260 (Chr9:90, 113, 207), -239 (Chr9:90, 113, 228), and -68 (Chr9:90, 113, 399) of DAPK1 promoter, were significantly hypermethylated. Moreover, 5-azacytidine (an inhibitor of DNA methyltransferase) partly impaired Cd-induced promoter hypermethylation of RASSF1A and DAPK1 genes, increased their expressions and slowed down Cd-induced cell proliferation, suggesting that DNA methylation play an essential part in Cd-boosted proliferation. The study showed that Cd caused promoter hypermethylation of RASSF1A and DAPK1, decreasing their expression and leading to higher level of cell proliferation. Furthermore, Cd at low concentrations could influence DNA methylation, which may serve as the proliferative mechanism of Cd.

The splicing regulator SLU7 is required to preserve DNMT1 protein stability and DNA methylation

Gene expression is finely and dynamically controlled through the tightly coordinated and interconnected activity of epigenetic modulators, transcription and splicing factors and post-translational modifiers. We have recently identified the splicing factor SLU7 as essential for maintaining liver cell identity and genome integrity and for securing cell division both trough transcriptional and splicing mechanisms. Now we uncover a new function of SLU7 controlling gene expression at the epigenetic level. We show that SLU7 is required to secure DNMT1 protein stability and a correct DNA methylation. We demonstrate that SLU7 is part in the chromatome of the protein complex implicated in DNA methylation maintenance interacting with and controlling the integrity of DNMT1, its adaptor protein UHRF1 and the histone methyl-transferase G9a at the chromatin level. Mechanistically, we found that SLU7 assures DNMT1 stability preventing its acetylation and degradation by facilitating its interaction with HDAC1 and the desubiquitinase USP7. Importantly, we demonstrate that this DNMT1 dependency on SLU7 occurs in a large panel of proliferating cell lines of different origins and in in vivo models of liver proliferation. Overall, our results uncover a novel and non-redundant role of SLU7 in DNA methylation and present SLU7 as a holistic regulator of gene expression.

DNA methyltransferase 1 inhibits O6-methylguanine-DNAmethyl-transferase-mediated cell growth and metastasis of hypopharyngeal squamous carcinoma

OBJECTIVE

To explore the role of DNA methyltransferase 1 (DNMT1) in development and progression of hypopharyngeal squamous carcinoma.

DESIGN

A total of 32 hypopharyngeal squamous carcinoma biopsy samples and 20 normal tissue specimens were collected. Immunohistochemical staining, quantitative real-time polymerase chain reaction, and Western blot were performed for expression analysis. The mRNA and protein expression in the specimens and subcellular localization were analyzed. hypopharyngeal squamous carcinoma cells (FaDu) were used for small interfering RNA of DNMT1, and proliferation, cell cycle, and apoptosis were determined in the transfected cells. Furthermore, metastatic ability and methylation status of O⁶-methylguanine-DNAmethyl-transferase (MGMT) promoter was assessed.

RESULTS

Our results showed that DNMT1 was overexpressed, while MGMT was down expressed in hypopharyngeal squamous carcinoma. DNMT1 overexpression and MGMT down expression were significantly associated with poorly differentiated tumors, lymph node metastasis, and clinical stage. DNMT1 and MGMT were majorly distributed in the nucleus. Furthermore, knockdown of DNMT1 inhibited proliferation and metastasis, induced apoptosis and G1 phase arrest in FaDu cells, and upregulated MGMT expression to reverse methylation status of MGMT promoter.

CONCLUSIONS

This study for the first time demonstrated the clinical value and the role of DNMT1 and MGMT in the biological function of hypopharyngeal squamous carcinoma. This work suggested that DNMT1 might serve as a potential therapeutic target for patients with hypopharyngeal squamous carcinoma.

Expression profiling of DNA methyl transferase I (DNMT1) and efficacy of a DNA-hypomethylating agent (decitabine) in combination with chemotherapy in osteosarcoma

Background

Abnormality in the DNA methylation process is one of the hallmarks of cancer. Emerging evidence strongly supports the idea that defects in DNA methyl transferases (DNMTs) are involved in tumor development and progression. This alteration has major effects at the transcription level of various cancer-associated genes.

Methods

Expression profiles of DNMT1 were investigated in fresh frozen tissues, patient-derived cells, and formalin-fixed paraffin-embedded tissues using immunoblotting and immunohistochemistry analysis. We also examined an anti-tumor effect of single DNA-hypomethylating agent (decitabine) and a combination of decitabine and chemotherapy in osteosarcoma cell lines.

Results

The results showed an overexpression of DNMT1 in most cases compared to normal cells and tissue samples. DNMT1 was also expressed at the same levels in paired primary cells derived from biopsy and post-chemotherapy tissues. Expression patterns of DNMT1 were examined in 77 osteosarcoma patients of whom 82% had positive DNMT1 with an IRS score > 0. Most of the cases expressed low to moderate levels of DNMT1 (IRS range 1-8, median = 2.0). Furthermore, we found that a combination of decitabine and chemotherapy had a synergistic effect in most of the tested osteosarcoma cells at a low dose therapeutic range of decitabine.

Conclusions

Our study revealed DNMT1 expression patterns that indicated potential roles of DNMT1 in osteosarcoma transformation and progression. This finding also suggests the efficacy of a combination therapy of decitabine with chemotherapy for osteosarcoma treatment.

Regulation of DNA methylation machinery by epi-miRNAs in human cancer: emerging new targets in cancer therapy

Disruption in DNA methylation processes can lead to alteration in gene expression and function that would ultimately result in malignant transformation. In this way, studies have shown that, in cancers, methylation-associated silencing inactivates tumor suppressor genes, as effectively as mutations. DNA methylation machinery is composed of several genes, including those with DNA methyltransferases activity, proteins that bind to methylated cytosine in the promoter region, and enzymes with demethylase activity. Based on a prominent body of evidence, DNA methylation machinery could be regulated by microRNAs (miRNAs) called epi-miRNAs. Numerous studies demonstrated that dysregulation in DNA methylation regulators like upstream epi-miRNAs is indispensable for carcinogenesis; consequently, the malignant capacity of these cells could be reversed by restoring of this regulatory system in cancer. Conceivably, recognition of these epi-miRNAs in cancer cells could not only reveal novel molecular entities in carcinogenesis, but also render promising targets for cancer therapy. In this review, at first, we have an overview of the methylation alteration in cancers, and the effect of this phenomenon in miRNAs expression and after that, we conduct an in-depth discussion about the regulation of DNA methylation regulators by epi-miRNAs in cancer cells.

Epigenetic Alterations in Oesophageal Cancer: Expression and Role of the Involved Enzymes

Oesophageal cancer is a life-threatening disease, accounting for high mortality rates. The poor prognosis of this malignancy is mostly due to late diagnosis and lack of effective therapies for advanced disease. Epigenetic alterations may constitute novel and attractive therapeutic targets, owing to their ubiquity in cancer and their reversible nature. Herein, we offer an overview of the most important studies which compared differences in expression of enzymes that mediate epigenetic alterations between oesophageal cancer and normal mucosa, as well as in vitro data addressing the role of these genes/proteins in oesophageal cancer. Furthermore, The Cancer Genome Atlas database was interrogated for the correlation between expression of these epigenetic markers and standard clinicopathological features. We concluded that most epigenetic players studied thus far are overexpressed in tumours compared to normal tissue. Furthermore, functional assays suggest an oncogenic role for most of those enzymes, supporting their potential as therapeutic targets in oesophageal cancer.

Microarray Profile of Long Noncoding RNA and Messenger RNA Expression in a Model of Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by a deficiency in cognitive skills. Although long noncoding RNAs (lncRNAs) have been proposed as associated with AD, the aberrant lncRNAs expression and the co-expression of lncRNAs-mRNAs network in AD remains unclear. Therefore, in this study, lncRNA microarray was performed on the brain of APP/PS1 mice at different age, widely used as an AD mouse model, and on age-matched wide-type controls. Our results identified a total of 3306 lncRNAs and 2458 mRNAs as aberrantly expressed among AD mice at different age and their age-matched control. Gene Ontology and pathway analysis of the AD-related lncRNAs and mRNAs indicated that neuroinflammation-related and synaptic transmission signaling pathways represented the main enriched pathways. An lncRNA-mRNA-miRNA network between the differentially expressed transcripts was constructed. Moreover, an mRNA-miRNA network between both significantly dysregulated and highly conserved genes was also constructed, and among this network, the IGF1, P2RX7, TSPO, SERPINE1, EGFR, HMOX1, and NFE212 genes were predicted to play a role in the development of AD. In conclusion, this study illustrated the prognostic value of lncRNAs and mRNAs associated to AD pathology by microarray analysis and might provide potential novel biomarkers in the diagnosis and treatment of AD.

RASSF1A Tumour Suppressor: Target the Network for Effective Cancer Therapy

The RASSF1A tumour suppressor is a scaffold protein that is involved in cell signalling. Increasing evidence shows that this protein sits at the crossroad of a complex signalling network, which includes key regulators of cellular homeostasis, such as Ras, MST2/Hippo, p53, and death receptor pathways. The loss of expression of RASSF1A is one of the most common events in solid tumours and is usually caused by gene silencing through DNA methylation. Thus, re-expression of RASSF1A or therapeutic targeting of effector modules of its complex signalling network, is a promising avenue for treating several tumour types. Here, we review the main modules of the RASSF1A signalling network and the evidence for the effects of network deregulation in different cancer types. In particular, we summarise the epigenetic mechanism that mediates RASSF1A promoter methylation and the Hippo and RAF1 signalling modules. Finally, we discuss different strategies that are described for re-establishing RASSF1A function and how a multitargeting pathway approach selecting druggable nodes in this network could lead to new cancer treatments.

5-Aza-CdR Regulates RASSF1A By Inhibiting DNMT1 To Affect Colon Cancer Cell Proliferation, Migration And Apoptosis

Objective

To evaluate 5-Aza-CdR’s inhibited effects on migration, proliferation, and apoptosis in colon cancer cells and its potential mechanisms.

Methods

HCT-116, SW480, and SW620 were divided into HCT116 group, HCT116+5-Aza-CdR group, SW480 group, SW480+5-Aza-CdR group, SW620 group and SW620+5-Aza according to experimental needs. MTT test was chosen to investigate cell proliferation; Transwell test was used to evaluate cell migration; scratch assay was used to investigate cell invasion; flow cytometry was used to investigate apoptosis; immunofluorescence assay was used to investigate the protein level of DNMT1 and RASSF1A in cells; qRT-PCR was used to examine DNMT1, RASSF1A, RAS, Raf1, MEK, Grb2 and ERK transcription levels.

Results

Compared with HCT116 group, 5-Aza-CdR+HCT116 group inhibited cell proliferation, increased apoptosis rate, decreased invasive ability, decreased DNMT1 expression, increased expression of RASSF1A, decreased expression of RAS, Raf1, MEK, Grb2 and ERK. SW480 was compared with 5-Aza-CdR+SW480 group and SW620 group with 5-Aza-CdR+SW620 group. Their change trend of detection index was similar to that in HCT-116 group and HCT116+5-Aza-CdR group.

Conclusion

5-Aza-CdR can obviously inhibit the proliferation, migration and invasion of three colon cancer cell lines. Its mechanism maybe relies on the inhibition of DNMT1 mRNA level and protein level and the enhancement of RASSF1A mRNA level and protein level.

DAPK1 loss triggers tumor invasion in colorectal tumor cells

Colorectal cancer (CRC) is one of the leading cancer-related causes of death worldwide. Despite the improvement of surgical and chemotherapeutic treatments, as of yet, the disease has not been overcome due to metastasis to distant organs. Hence, it is of great relevance to understand the mechanisms responsible for metastasis initiation and progression and to identify novel metastatic markers for a higher chance of preventing the metastatic disease. The Death-associated protein kinase 1 (DAPK1), recently, has been shown to be a potential candidate for regulating metastasis in CRC. Hence, the aim of the study was to investigate the impact of DAPK1 protein on CRC aggressiveness. Using CRISPR/Cas9 technology, we generated DAPK1-deficient HCT116 monoclonal cell lines and characterized their knockout phenotype in vitro and in vivo. We show that loss of DAPK1 implemented changes in growth pattern and enhanced tumor budding in vivo in the chorioallantoic membrane (CAM) model. Further, we observed more tumor cell dissemination into chicken embryo organs and increased invasion capacity using rat brain 3D in vitro model. The novel identified DAPK1-loss gene expression signature showed a stroma typical pattern and was associated with a gained ability for remodeling the extracellular matrix. Finally, we suggest the DAPK1-ERK1 signaling axis being involved in metastatic progression of CRC. Our results highlight DAPK1 as an anti-metastatic player in CRC and suggest DAPK1 as a potential predictive biomarker for this cancer type.

Promoter Methylation of Four Tumor Suppressor Genes in Human Papillary Thyroid Carcinoma

BACKGROUND & OBJECTIVE

Papillary thyroid cancer (PTC) is considered to be the most common type of thyroid malignancies. Epigenetic alteration, in which the chromatin conformation and gene expression change without changing the sequence of DNA, can occur in some tumor suppressor genes and oncogenes. Methylation is the most common type of epigenetic alterations that can be an excellent indicator of PTC invasive behavior.

METHODS

In this research, we determined the promoter methylation status of four tumor suppressor genes (SLC5A8, RASSF1, MGMT, and DNMT1) and compared the results of 55 PTC cases with 40 goiter patients. For methylation, we used the methylation-sensitive high resolution melting (MS-HRM) assay technique. The resulting graphs of each run were compared with those of 0%, 50%, and 100% methylated controls.

RESULTS

Our data showed that the promoter methylation of SLC5A8, Ras association domain family member 1(RASSF1), and MGMT were significantly different between PTC tissue and goiter with P-value less than 0.05. The most significant differences were observed in RASSF1; 77.2% of hyper-methylated PTC patients versus 15.6% hyper-methylated goiter samples (P<0.001).

CONCLUSION

RASSF1 promoter methylation can be a PTC genetic marker. RASSF1 promoter methylation is under the impact of the methyltransferase genes (DNMT1 and MGMT), protein expression, and promoter methylation.

Methylation Dynamics of RASSF1A and Its Impact on Cancer

5-methyl cytosine (5mC) is a key epigenetic mark entwined with gene expression and the specification of cellular phenotypes. Its distribution around gene promoters sets a barrier for transcriptional enhancers or inhibitor proteins binding to their target sequences. As a result, an additional level of regulation is added to the signals that organize the access to the chromatin and its structural components. The tumor suppressor gene RASSF1A is a microtubule-associated and multitasking scaffold protein communicating with the RAS pathway, estrogen receptor signaling, and Hippo pathway. RASSF1A action stimulates mitotic arrest, DNA repair and apoptosis, and controls the cell cycle and cell migration. De novo methylation of the RASSF1A promoter has received much attention due to its increased frequency in most cancer types. RASSF1A methylation is preceded by histones modifications and could represent an early molecular event in cell transformation. Accordingly, RASSF1A methylation is proposed as an epigenetic candidate marker in many cancer types, even though an inverse correlation of methylation and expression remains to be fully ascertained. Some findings indicate that the epigenetic abrogation of RASSF1A can promote the alternative expression of the putative oncogenic isoform RASSF1C. Understanding the complexity and significance of RASSF1A methylation is instrumental for a more accurate determination of its biological and clinical role. The review covers the molecular events implicated in RASSF1A methylation and gene silencing and provides a deeper view into the significance of the RASSF1A methylation patterns in a number of gastrointestinal cancer types.

Knockdown of KCNQ1OT1 Suppresses Cell Invasion and Sensitizes Osteosarcoma Cells to CDDP by Upregulating DNMT1-Mediated Kcnq1 Expression

Osteosarcoma is a malignant bone tumor, with a high incidence worldwide. The involvement of long non-coding RNAs (lncRNAs) in cancers and their molecular association with the progression of osteosarcoma have been previously discussed. We conducted the present study to examine the effect of lncRNA KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) on osteosarcoma cell invasion and chemosensitivity to cisplatin (CDDP). After determination of the expression of Kcnq1 in osteosarcoma tissues and cells, the plasmids with overexpression or knockdown KCNQ1OT1 were introduced into the cells to aid the identification of cell proliferation, migration, invasion, chemosensitivity to CDDP, and apoptosis. Then, the interaction between KCNQ1OT1 and the Kcnq1/DNA methyltransferase 1 (DNMT1) axis was evaluated by measuring the level of Kcnq1 promoter region methylation and DNMT1 enrichment of the Kcnq1 promoter region. Low Kcnq1 expression and high KCNQ1OT1 expression were shown in osteosarcoma tissues and cells. Kcnq1 was negatively mediated by KCNQ1OT1 via DNMT1. The overexpression of Kcnq1 or knockdown of KCNQ1OT1 inhibited the proliferation, migration, and invasion, and it promoted the chemosensitivity to CDDP and apoptosis of MG-63 cells and its CDDP-resistant cell lines. Moreover, the same trend was observed in the cells following methylation inhibitor treatment. Collectively, knockdown of KCNQ1OT1 can inhibit the osteosarcoma progression through the Kcnq1/DNMT1 axis.

miR-148a-3p Suppresses the Proliferation and Invasion of Esophageal Cancer by Targeting DNMT1

AIM

To identify whether miR-148a-3p interacts with DNA (cytosine-5)-methyltransferase 1 (DNMT1) in esophageal cancer.

METHODS

A luciferase assay and immunoblotting were performed to detect the relationship between miR-148a-3p and DNMT1. The MTT method, Annexin V/propidium iodide staining, and Transwell assays were adopted to assess the biological behaviors in EC109 cells. The association between the expression level of miR-148a-3p, clinical features, and prognosis were evaluated by chi-square test and univariate survival analysis.

RESULTS

In this study, DNMT1 was identified as a direct target of miR-148a-3p by luciferase assay and Western blot. Real-time quantitative PCR analyses showed that the relative expression levels of miR-148a-3p and DNMT1 were reduced in esophageal cancer samples compared with adjacent tissues; and a negative relationship between both was indicated. Upon overexpression of miR-148a-3p in esophageal cancer cells, proliferation and invasion were significantly suppressed, and apoptosis was promoted. A higher level of miR-148a-3p was correlated with better patient outcomes.

CONCLUSIONS

Our study indicated that miR-148a-3p, by targeting DNMT1, likely regulates cell proliferation and invasion in esophageal cancer. miR-148a-3p might also be used prognostically in esophageal cancer and serve as a therapeutic target in the future.

EBNA3C facilitates RASSF1A downregulation through ubiquitin-mediated degradation and promoter hypermethylation to drive B-cell proliferation

EBV latent antigen 3C (EBNA3C) is essential for EBV-induced primary B-cell transformation. Infection by EBV induces hypermethylation of a number of tumor suppressor genes, which contributes to the development of human cancers. The Ras association domain family isoform 1A (RASSF1A) is a cellular tumor suppressor, which regulates a broad range of cellular functions, including apoptosis, cell-cycle arrest, mitotic arrest, and migration. However, the expression of RASSF1A is lost in many human cancers by epigenetic silencing. In the present study, we showed that EBNA3C promoted B-cell transformation by specifically suppressing the expression of RASSF1A. EBNA3C directly interacted with RASSF1A and induced RASSF1A degradation via the ubiquitin-proteasome-dependent pathway. SCFSkp2, an E3-ubiquitin ligase, was recruited by EBNA3C to enhance RASSF1A degradation. Moreover, EBNA3C decreased the transcriptional activity of RASSF1A promoter by enhancing its methylation through EBNA3C-mediated modulation of DNMTs expression. EBNA3C also inhibited RASSF1A-mediated cell apoptosis, disrupted RASSF1A-mediated microtubule and chromosomal stability, and promoted cell proliferation by upregulating Cyclin D1 and Cyclin E expression. Our data provides new details, which sheds light on additional mechanisms by which EBNA3C can induce B-cell transformation. This will also facilitate the development of novel therapeutic approaches through targeting of the RASSF1A pathway.

Comprehensive bioinformation analysis of methylated and differentially expressed genes in esophageal squamous cell carcinoma

Differentially methylated genes (DMGs) play a crucial role in the etiology and pathogenesis of esophageal squamous cell carcinoma (ESCC).

Correlation between tripartite motif-containing protein 44 protein expression and the prognosis of postoperative patients exhibiting skin squamous cell carcinoma

Tripartite motif-containing protein 44 (TRIM44) plays an important role in the development and progression of some human cancers; however, its role in skin squamous cell carcinoma (SCC) remains unknown. The aim of the present study was to investigate TRIM44 expression and clinicopathological significance of TRIM44 in SCC.Immunohistochemistry (IHC) technique, reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot were performed to evaluate differences in TRIM44 protein expression in SCC and normal skin tissues.IHC showed that the positive rate of TRIM44 staining in SCC tissues 26.00% (9/30), while the positive rate of normal control group was 83.33% (25/30). The positive rate of TRIM44 staining in SCC tissues is significantly lower than normal skin tissue (P <.01). RT-PCR showed that the positive rates of TRIM44 mRNA expression in SCC tissues were 16.67% (5/30), but the positive rate of normal control group was 86.67% (26/30). TRIM44 mRNA expression in SCC group was significantly lower than that in the normal group (P <.01). Kaplan-Meier survival analysis showed that low expression was associated with poor overall survival in SCC patients (P =.004). Multi-factor survival analysis indicated that both low TRIM44 expression and tumor stage were independent factors affecting the overall survival of patients with SCC (P =.038 and P =.001, respectively). Low expression of TRIM44 in SCC was associated with staging (P =.009 and P =.008, respectively) and metastasis (P =.003 and P =.004, respectively).The levels of TRIM44 protein and TRIM44 mRNA in SCC are both lowly expressed which is strongly associated with tumor staging, metastasis, and poor survival. And it also is an independent factor affecting the overall survival of patients with SCC.

NUSAP1 gene silencing inhibits cell proliferation, migration and invasion through inhibiting DNMT1 gene expression in human colorectal cancer

Colorectal cancer (CRC) is one of the most common cause of cancer-related death in both female and male patients, with a high capacity for tumor migration and invasion. Recently, aberrant nucleolar and spindle-associated protein 1 (NUSAP1) expression has been reported in several cancers. However, the biological function and molecular mechanism of NUSAP1 in CRC have not been reported. Here, we demonstrated that NUSAP1 gene expression was notably upregulated in CRC tissues and cell lines (Caco2, LS174T, SW480, and LoVo). Subsequently, SW480 and LoVo cells were transfected with NUSAP1 siRNA, respectively, and the biological function of NUSAP1 was investigated. Results indicated that NUSAP1 silencing by siRNA inhibited CRC cell proliferation, and induces cell apoptosis. Moreover, NUSAP1 knockdown suppressed cell migration, cell invasion, and epithelial-to-mesenchymal transition (EMT). Furthermore, NUSAP1 silencing notably inhibited the mRNA and protein expression level of DNA methyltransferase 1 (DNMT1). DNMT1 overexpression partly rescued the effect of NUSAP1 silencing on colorectal cancer biological function. Taken together, NUSAP1 gene silencing induced cell apoptosis, and inhibited cell proliferation, cell migration, cell invasion, and EMT in colorectal cancer through inhibiting DNMT1 gene expression. These findings indicat that NUSAP1 is a promising molecular target for CRC treatment.

Promoter hypermethylation may contribute to E‑cadherin repression in the human salivary carcinoma ex pleomorphic adenoma

The role of promoter methylation in the inactivation of E‑cadherin (CDH1) in salivary carcinoma ex pleomorphic adenoma (CXPA) is unknown. The objective of this study was to determine the role and potential clinical implications of CDH1 promoter methylation in salivary CXPA. The CDH1 promoter methylation status was determined by bisulfite sequencing PCR in 37 primary CXPA tissues and 2 CXPA cell lines. E‑cadherin expression levels were determined by immunohistochemical analysis of each tumor. E‑cadherin protein levels and CDH1 mRNA levels were examined by immunoblotting and quantitative real-time PCR, respectively, in 2 CXPA cell lines. Cells were treated with 5‑Aza-dC or TGF‑β1 to test the influence of promoter methylation on CDH1 mRNA and protein expression. Associations between CDH1 molecular alterations and patients' clinicopathologic characteristics and prognosis were statistically evaluated. CDH1 promoter hypermethylation was detected in 21 of 37 tumors (56.76%). Of these 37 tumors, 13 tumors (35.14%) showed low E‑cadherin expression. Tumors that had CDH1 promoter methylation had a histological tendency toward luminal differentiation (P=0.004), high tumor grade (P=0.005), high T stage (P=0.024) and high TNM stage (P=0.038) compared with tumors that did not. The two CXPA cell lines exhibited an inverse relationship between CDH1 promoter methylation status and CDH1 mRNA and protein expression. Treatment of the hypermethylated cell line with 5‑Aza-dC restored CDH1 mRNA and E‑cadherin protein expression. The induction of hypermethylation by TGF‑β1 resulted in the repression of CDH1 mRNA and protein expression. CDH1 is commonly silenced in CXPA through promoter methylation. CDH1 methylation is closely related to tumor cell differentiation, histological grade, lymph node metastasis and advanced TNM stage, indicating that CDH1 methylation may play a role in the initiation and progression of CXPA.

DNMT1 is associated with cell cycle and DNA replication gene sets in diffuse large B-cell lymphoma

Dysregulation of DNA (cytosine-5)-methyltransferase 1 (DNMT1) is associated with the pathogenesis of various types of cancer. It has been previously shown that DNMT1 is frequently expressed in diffuse large B-cell lymphoma (DLBCL), however its functions remain to be elucidated in the disease. In this study, we gene expression profiled (GEP) shRNA targeting DNMT1(shDNMT1)-treated germinal center B-cell-like DLBCL (GCB-DLBCL)-derived cell line (i.e. HT) compared with non-silencing shRNA (control shRNA)-treated HT cells. Independent gene set enrichment analysis (GSEA) performed using GEPs of shRNA-treated HT cells and primary GCB-DLBCL cases derived from two publicly-available datasets (i.e. GSE10846 and GSE31312) produced three separate lists of enriched gene sets for each gene sets collection from Molecular Signatures Database (MSigDB). Subsequent Venn analysis identified 268, 145 and six consensus gene sets from analyzing gene sets in C2 collection (curated gene sets), C5 sub-collection [gene sets from gene ontology (GO) biological process ontology] and Hallmark collection, respectively to be enriched in positive correlation with DNMT1 expression profiles in shRNA-treated HT cells, GSE10846 and GSE31312 datasets [false discovery rate (FDR) <0.05]. Cell cycle progression and DNA replication were among the significantly enriched biological processes (FDR <0.05). Expression of genes involved in the activation of cell cycle and DNA replication (e.g. CDK1, CCNA2, E2F2, PCNA, RFC5 and POLD3) were highly correlated (r>0.8) with DNMT1 expression and significantly downregulated (log fold-change <-1.35; p<0.05) following DNMT1 silencing in HT cells. These results suggest the involvement of DNMT1 in the activation of cell cycle and DNA replication in DLBCL cells.

DNA methylation profiles in cancer diagnosis and therapeutics

Cancer initiation and proliferation is regulated by both epigenetic and genetic events with epigenetic modifications being increasingly identified as important targets for cancer research. DNA methylation catalyzed by DNA methyltransferases (DNMTs) is one of the essential epigenetic mechanisms that control cell proliferation, apoptosis, differentiation, cell cycle, and transformation in eukaryotes. Recent progress in epigenetics revealed a deeper understanding of the mechanisms of tumorigenesis and provided biomarkers for early detection, diagnosis, and prognosis in cancer patients. Although DNA methylation biomarker possesses potential contributing to precision medicine, there are still limitations to be overcome before it reaches clinical setting. Hence, the current status of DNA methylation biomarkers was reviewed and the future use in clinic was also predicted.

Correlation between secreted protein acidic and rich in cysteine protein expression and the prognosis of postoperative patients exhibiting esophageal squamous cell carcinoma

The aim of the present study was to investigate the association between the expression level of secreted protein acidic and rich in cysteine (SPARC) and the prognosis of postoperative patients with esophageal squamous cell carcinoma (ESCC). The expression level of SPARC was detected in the 89 ESCC tissue cases and 100 healthy esophageal mucosa cases, which served as the controls. Immunohistochemistry and reverse transcription‑polymerase chain reaction (RT‑PCR) were employed to evaluate the SPARC expression in cases with ESCC. RT‑PCR demonstrated that the positive rates of SPARC mRNA expression in ESCC were 71.91% (64/89). The positive rates of normal esophageal mucosa mRNA expression were 15.00% (15/100), which were significantly lower than that in the ESCC tissue samples. The difference was statistically significant (P<0.001). Immunohistochemical staining indicated that the positive expression rate of SPARC protein in the ESCC tissue samples was significantly higher than that in the esophageal mucosa tissue samples (65.17 vs. 8.00%; P<0.001). The expression of SPARC protein was negatively correlated with lymph node metastasis (P<0.05), which was not associated with the pathologic gross morphology, tumor differentiation degree or other clinical features. The survival of patients with ESCC was not associated with the expression level of SPARC protein (P>0.05), but was associated with the tumor location (P<0.05), differentiation (P<0.001) and staging (P<0.05). Thus, SPARC mRNA and protein were highly expressed in ESCC, and negatively correlated with lymph node metastasis, which was not associated with postoperative survival of ESCC patients. Thus, detection of SPARC mRNA and protein expression levels may facilitate early diagnosis and prognosis assessment of ESCC.

Association between promoter methylation of DAPK gene and HNSCC: A meta-analysis

BACKGROUND

The death-associated protein kinase (DAPK) is a tumor suppressor gene, which is a mediator of cell death of INF-γ-induced apoptosis. Aberrant methylation of DAPK promoter has been reported in patients with head and neck squamous cell carcinoma (HNSCC). However, the results of these studies are inconsistent. Hence, the present study aimed to evaluate the association between the promoter methylation of DAPK gene and HNSCC.

METHODS

Relevant studies were systematically searched in PubMed, Web of Science, Ovid, and Embase. The association between DAPK promoter methylation and HNSCC was assessed by odds ratio (ORs) and 95% confidence intervals (CI). To evaluate the potential sources of heterogeneity, we conducted the meta-regression analysis and subgroup analysis.

RESULTS

Eighteen studies were finally included in the meta-analysis. The frequency of DAPK promoter methylation in patients with HNSCC was 4.09-fold higher than the non-cancerous controls (OR = 3.96, 95%CI = 2.26-6.95). A significant association between DAPK promoter methylation and HNSCC was found among the Asian region and the Non-Asia region (Asian region, OR = 4.43, 95% CI = 2.29-8.58; Non-Asia region, OR = 3.39, 95% CI = 1.18-9.78). In the control source, the significant association between DAPK promoter methylation and HNSCC was seen among the autologous group and the heterogeneous group (autologous group, OR = 2.71, 95% CI = 1.49-4.93; heterogeneous group, OR = 9.50, 95% CI = 2.98-30.27). DAPK promoter methylation was significantly correlated with alcohol status (OR = 1.85, 95% CI = 1.07-3.21).

CONCLUSION

The results of this meta-analysis suggested that aberrant methylation of DAPK promoter was associated with HNSCC.

SQLE induces epithelial-to-mesenchymal transition by regulating of miR-133b in esophageal squamous cell carcinoma

Increasing evidence suggests that microRNAs, which control gene expression at the post-transcriptional level, are aberrantly expressed in cancers and play significant roles in carcinogenesis and cancer progression. In this study, we show differential miR-133b down-expression in human esophageal squamous cell carcinoma (ESCC) cells and tissues. In addition, squalene epoxidase (SQLE), a key enzyme of cholesterol synthesis, is identified as the direct downstream target gene of miR-133b by luciferase gene reporter assay. Furthermore, ectogenic miR-133b expression and SQLE knockdown can inhibit proliferation, invasion, and metastasis, and diminish epithelial-to-mesenchymal transition (EMT) traits of ESCC in vitro, implying that miR-133b-dependent SQLE can induce tumorigenicity and that SQLE is an EMT inducer. Xenograft experiment results also proved the biological function of SQLE in vivo. Therefore, we conclude that miR-133b-dependent SQLE plays a critical role in the potential metastasis mechanisms in ESCC.