Hypermethylation of RAS effector related genes and DNA methyltransferase 1 expression in endometrial carcinogenesis

LncRNA MIR210HG promotes the proliferation, migration, and invasion of lung cancer cells by inhibiting the transcription of SH3GL3

Lung cancer (LCa), the most frequent malignancy worldwide, causes millions of mortalities each year. Overexpression of the long noncoding RNA MIR210HG in LCa has been established; however, a more comprehensive investigation into its biological role within LCa is imperative. This study aimed to validate the MIR210H levels in LCa tissues and cells. The expression of indicated genes was evaluated using quantitative real-time polymerase chain reaction (qRT-PCR) and/or Western blotting. The viability, proliferation, migration, and invasion of LCa cells were measured using the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), colony formation, wound healing, and transwell assays, respectively. The methylation levels of LCa cells were determined via methylation-specific PCR; additionally, chromatin immunoprecipitation or RNA immunoprecipitation assays were performed to determine the targeting relationship between DNA methyltransferase 1 (DNMT1) and the SH3-domain containing CRB2 like 3 (SH3GL3) promoters and the interaction between DNMT1 and MIR210HG, respectively. Our findings revealed the upregulation of MIR210HG, coupled with a diminished expression of SH3GL3 in LCa tissues and cells. Knockdown of MIR210HG or overexpression of SH3GL3 suppressed the proliferative, migratory, and invasive capacities of the cells. DNMT1 bound to the SH3GL3 promoter region, and MIR210HG inhibited the transcription of SH3GL3 by recruiting DNMT1. These findings indicate that MIR210HG facilitates LCa cell growth and metastasis by repressing SH3GL3 transcription via the recruitment of DNMT1 to the SH3GL3 promoter region.

DNMT1 expression partially dictates 5-Azacytidine sensitivity and correlates with RAS/MEK/ERK activity in gastric cancer cells

Though DNMTs inhibitors were widely used in myelodysplastic syndrome and leukaemia, their application in solid tumours has been limited by low response rate and lack of optimal combination strategies. In gastric cancer (GC), the therapeutic implication of KRAS mutation or MEK/ERK activation for combinational use of DNMTs inhibitors with MEK/ERK inhibitors remains elusive. In this study, stable knockdown of DNMT1 expression by lentiviral transfection led to decreased sensitivity of GC cells to 5-Azacytidine. KRAS knockdown in KRAS mutant GC cells or the MEK/ERK activation by EGF stimulation in GC cells increased DNMT1 expression, while inhibition of MEK/ERK activity by Selumetinib led to decreased DNMT1 expression. 5-Azacytidine treatment, which led to dramatic decline of DNMTs protein levels and increased activity of MEK/ERK pathway, altered the activity of MEK/ERK inhibitor Selumetinib on GC cells. Both RAS-dependent gene expression signature and expression levels of multiple MEK/ERK-dependent genes were correlated with DNMT1 expression in TCGA stomach cancer samples. In conclusion, DNMT1 expression partially dictates 5-Azacytidine sensitivity and correlates with RAS/MEK/ERK activity in GC cells. Combining DNMTs inhibitor with MEK/ERK inhibitor might be a promising strategy for patients with GC.[Figure: see text].

Research Progress of DNA Methylation in Endometrial Cancer

Endometrial cancer (EC)) is one of the most common malignant tumors of the female genital system, with an increasing incidence and mortality, worldwide. Although the therapeutic strategy of EC is still complicated and challenging, further understanding of carcinogenesis from a gene perspective would allow an effort to improve therapeutic precision in this complex malignancy. DNA methylation is the most widely studied epigenetic alteration in human tumors. Aberrant DNA methylation events, resulting in altered gene expression, are features of many tumor types. In this review, we provide an update on evidence about the roles of aberrant DNA methylation within some classical tumor suppressor genes and oncogenes in endometrial carcinogenesis, and report on recent advances in the understanding of the contribution of aberrant DNA methylation to EC, as well as opportunities and challenges of DNA methylation in EC management and prevention.

Targeting Epigenetic Regulators for Endometrial Cancer Therapy: Its Molecular Biology and Potential Clinical Applications

Endometrial cancer is one of the most frequently diagnosed gynecological malignancies worldwide. However, its prognosis in advanced stages is poor, and there are only few available treatment options when it recurs. Epigenetic changes in gene function, such as DNA methylation, histone modification, and non-coding RNA, have been studied for the last two decades. Epigenetic dysregulation is often reported in the development and progression of various cancers. Recently, epigenetic changes in endometrial cancer have also been discussed. In this review, we give the main points of the role of DNA methylation and histone modification in endometrial cancer, the diagnostic tools to determine these modifications, and inhibitors targeting epigenetic regulators that are currently in preclinical studies and clinical trials.

Discriminating miRNA Profiles between Endometrioid Well- and Poorly-Differentiated Tumours and Endometrioid and Serous Subtypes of Endometrial Cancers

The discrimination of different subtypes of endometrial carcinoma (EC) is frequently problematic when using the current histomorphological classification; therefore, new markers for this differentiation are needed. Here, we examined differences in miRNA expression between well- and poorly-differentiated (grades 1 and 3) endometrioid endometrial carcinoma (EEC) and between EEC and serous endometrial carcinoma (SEC). The expression of 84 tumour-suppressor miRNAs was analysed by real-time polymerase chain reactions in 62 EC and 20 non-neoplastic endometrial specimens. The potential functions of the differentially expressed miRNAs were determined by bioinformatics analyses. The expression of let-7c-5p, miR-125b-5p, miR-23b-3p, and miR-99a-5p in grade 3 EEC was decreased compared to grade 1 EEC. To discriminate between EEC and SEC, let-7g-5p, miR-195-5p, miR-34a-5p, and miR-497-5p expression was significantly downregulated in SEC. In bioinformatic analyses, miRNAs that could discriminate grade 1 from grade 3 mainly targeted genes involved in PI3K-AKT signaling, whereas miRNAs that could discriminate EEC from SEC targeted genes involved in several signaling pathways, but mainly MAPK signaling. Taken collectively, our results indicate that the activation of certain signaling pathways can be useful in the molecular characterization of EEC and SEC.

Integrative analysis of genomic and epigenetic regulation of endometrial cancer

Endometrial carcinomas (EC) are characterized by high DNA copy numbers and DNA methylation aberrations. In this study, we sought to comprehensively explore the effect of these two factors on development and progression of EC by analyzing integrated genomic and epigenetic analysis to. We found high DNA copy number and DNA methylation abnormalities in EC, with 6308 copy-number variation genes (CNV-G) and 4376 methylation genes (MET-G). We used these CNV-G and MET-G to subcategorize the samples for prognostic analysis, and identified three molecular subtypes (iC1, iC2, iC3). Moreover, the subtypes exhibited different tumor immune microenvironment characteristics. A further analysis of their molecular characteristics revealed three potential prognostic markers (KIAA1324, nonexpresser of pathogenesis-related genes1 (NPR1) and idiopathic hypogonadotropic hypogonadism (IHH)). Notably, all three markers showed distinct CNV, DNA methylation, and gene expression profiles. Analysis of mutations among the three subtypes revealed that iC2 had fewer mutations than the other subtypes. Conversely, iC2 showed significantly higher CNV levels than other subtypes. This comprehensive analysis of genomic and epigenetic profiles identified three prognostic markers, therefore, provides new insights into the multi-layered pathology of EC. These can be utilized for accurate treatment of EC patients.

Could DNA hydroxymethylation be crucial in influencing steroid hormone signaling in endometrial biology and endometriosis?

Endometriosis affects 10% of reproductive-aged women. It is characterized by the growth of the endometrium, outside the uterus and is associated with infertility and chronic abdominal pain. Lack of noninvasive diagnostic tools and early screening tests results in delayed treatment and subsequently increased disease severity. Endometriosis is a disease associated with a deregulated hormonal response, therefore, understanding the molecular mechanisms that govern this hormonal interplay is of paramount importance. DNA methylation is an epigenetic mark that regulates gene expression and is often associated with genes that code for steroid receptors and enzymes associated with estrogen synthesis and metabolism in endometriosis. DNA hydroxymethylation, which is structurally similar to methylation but functionally different, is a biologically critical mechanism that is also known to regulate gene expression. Ten Eleven Translocation (TET) proteins mediate hydroxymethylation. However, the role of DNA hydroxymethylation or TETs in the endometrium remains relatively unexplored. Currently, the "gold standard" technique used to study methylation patterns is bisulfite genomic sequencing. This technique also detects hydroxymethylation but fails to distinguish between the two, thereby limiting our understanding of these two processes. The presence of TETs in the male and female reproductive tract and its contribution to endometrial cancer makes it an important factor to study in endometriosis. This review summarizes the role of DNA methylation in aberrant steroid hormone signaling and hypothesizes that hydroxymethylation could be a factor influencing hormonal instability seen in endometriosis.

DNMT3A/3B overexpression might be correlated with poor patient survival, hypermethylation and low expression of ESR1/PGR in endometrioid carcinoma: an analysis of The Cancer Genome Atlas

BACKGROUND

DNA methylation is involved in numerous biologic events and associates with transcriptional gene silencing, playing an important role in the pathogenesis of endometrial cancer. ESR1/PGR frequently undergoes de novo methylation and loss expression in a wide variety of tumors, including breast, colon, lung, and brain tumors. However, the mechanisms underlying estrogen and progesterone receptors (ER/PR) loss in endometrial cancer have not been studied extensively. The aims of this study were to determine the expression of DNA (cytosine-5)-methyltransferase 3A/3B (DNMT3A/3B) in endometrial cancer to investigate whether the methylation catalyzed by DNMT3A/3B contributes to low ER/PR expression.

METHODS

The clinicopathologic information and RNA-Seq expression data of DNMT3A/3B of 544 endometrial cancers were derived from The Cancer Genome Atlas (TCGA) uterine cancer cohort in May 2018. RNA-Seq level of DNMT3A/3B was compared between these clinicopathologic factors with t-test or one-way analysis of variance.

RESULTS

DNMT3A/3B was overexpressed in endometrioid carcinoma (EEC) and was even higher in non-endometrioid carcinoma (NEEC) (DNMT3A, EEC vs. NEEC: 37.6% vs. 69.9%, t = -7.440, P < 0.001; DNMT3B, EEC vs. NEEC: 42.4% vs. 72.8%, t = -6.897, P < 0.001). In EEC, DNMT3A overexpression was significantly correlated with the hypermethylation and low expression of the ESR1 and PGR (P < 0.05). The same trend was observed in the DNMT3B overexpression subgroup. In the ESR1/PGR low-expression subgroups, as much as 83.1% of ESR1 and 59.5% of PGR were hypermethylated, which was significantly greater than the ESR1/PGR high-expression subgroups (31.3% and 11.9%, respectively). However, the above phenomena were absent in NEEC, while DNMT3A/3B overexpression, ESR1/PGR hypermethylation, and low ER/PR expression occurred much more often. In univariate analysis, DNMT3A/3B overexpressions were significantly correlated with worse prognosis. In multivariate analysis, only DNMT3A was an independent predictor of disease-free survival (P < 0.05).

CONCLUSIONS

DNMT3A/3B expression increases progressively from EEC to NEEC and is correlated with poor survival. The mechanisms underlying low ER/PR expression might be distinct in EEC vs. NEEC. In EEC, methylation related to DNMT3A/3B overexpression might play a major role in ER/PR downregulation.

Endometrial Carcinoma: Specific Targeted Pathways

Endometrial cancer (EC) is the most common gynecologic malignancy in the western world with more than 280,000 cases per year worldwide. Prognosis for EC at early stages, when primary surgical resection is the most common initial treatment, is excellent. Five-year survival rate is around 70 %.Several molecular alterations have been described in the different types of EC. They occur in genes involved in important signaling pathways. In this chapter, we will review the most relevant altered pathways in EC, including PI3K/AKT/mTOR, RAS-RAF-MEK-ERK, Tyrosine kinase, WNT/β-Catenin, cell cycle, and TGF-β signaling pathways. At the end of the chapter, the most significant clinical trials will be briefly discussed.This information is important to identify specific targets for therapy.

Potential of RASSF1A promoter methylation as biomarker for endometrial cancer: A systematic review and meta-analysis

BACKGROUND

An epigenetic approach to explaining endometrial carcinogenesis necessitates good understanding of Ras association domain family 1 isoform A (RASSF1A) promoter methylation data from primary studies.

AIMS

Differential magnitude of reported associations between RASSF1A promoter methylation and endometrial cancer (EC) prompted a meta-analysis to obtain more precise estimates.

METHODS

Literature search yielded eight included articles. We calculated pooled odds ratios (OR) and 95% confidence intervals and subgrouped the data by race. Sources of heterogeneity were investigated with outlier analysis.

RESULTS

The pooled ORs indicated increased risk, mostly significant. The overall effect (OR 11.46) was reflected in the European outcome (OR 15.07). However, both findings were heterogeneous (I²=57-70%) which when subjected to outlier treatment, erased heterogeneity (I²=0%) and retained significance (OR 9.85-12.66). Significance of these pre- and post-outlier outcomes were pegged at P≤0.0001. Only the Asian pre-outlier (OR 6.85) and heterogeneous (I²=82%) outcome was not significant (P=0.12) but when subjected to outlier treatment, erased heterogeneity (I²=0%) and generated significance (OR 23.74, P≤0.0001).

CONCLUSIONS

Consistent increased risk associations underpinned by significance and robustness render RASSF1A with good biomarker potential for EC.

Epigenetics in endometrial carcinogenesis - part 1: DNA methylation

Carcinogenesis is a multistep multifactorial process that involves the accumulation of genetic and epigenetic alterations. In the past two decades, there has been an exponential growth of knowledge establishing the importance of epigenetic changes in cancer. Our work focused on reviewing the main role of epigenetics in the pathogenesis of endometrial carcinoma, highlighting the reported results concerning each epigenetic mechanistic layer. The present review is the first part of this work, in which we examined the contribution of DNA methylation alterations for endometrial carcinogenesis.

Down-regulation of DAB2IP promotes colorectal cancer invasion and metastasis by translocating hnRNPK into nucleus to enhance the transcription of MMP2

DOC-2/DAB2 interacting protein (DAB2IP) is a RasGAP protein that shows a suppressive effect on cancer progression. Our previous study showed the involvement of transcription regulation of DAB2IP in metastasis of colorectal cancer (CRC). However, the molecular mechanisms of DAB2IP in regulating the progression of CRC need to be further explored. Here, we identified heterogeneous nuclear ribonucleoprotein K (hnRNPK) and matrix metalloproteinase 2 (MMP2) as vital downstream targets of DAB2IP in CRC cells by two-dimensional fluorescence difference gel electrophoresis and cDNA microassay, respectively. Mechanistically, down-regulation of DAB2IP increased the level of hnRNPK through MAPK/ERK signaling pathway. Subsequently, translocation of hnRNPK into nucleus enhanced the transcription activity of MMP2, and therefore promoted invasion and metastasis of CRC. Down-regulation of DAB2IP correlated negatively with hnRNPK and MMP2 expressions in CRC tissues. In conclusion, our study elucidates a novel mechanism of the DAB2IP/hnRNPK/MMP2 axis in the regulation of CRC invasion and metastasis, which may be a potential therapeutic target.

Dynamic studies of H-Ras•GTPγS interactions with nucleotide exchange factor Sos reveal a transient ternary complex formation in solution

The cycling between GDP- and GTP- bound forms of the Ras protein is partly regulated by the binding of Sos. The structural/dynamic behavior of the complex formed between activated Sos and Ras at the point of the functional cycle where the nucleotide exchange is completed has not been described to date. Here we show that solution NMR spectra of H-Ras∙GTPγS mixed with a functional fragment of Sos (Sos^Cat) at a 2:1 ratio are consistent with the formation of a rather dynamic assembly. H-Ras∙GTPγS binding was in fast exchange on the NMR timescale and retained a significant degree of molecular tumbling independent of Sos^Cat, while Sos^Cat also tumbled largely independently of H-Ras. Estimates of apparent molecular weight from both NMR data and SEC-MALS revealed that, at most, only one H-Ras∙GTPγS molecule appears stably bound to Sos. The weak transient interaction between Sos and the second H-Ras∙GTPγS may provide a necessary mechanism for complex dissociation upon the completion of the native GDP → GTP exchange reaction, but also explains measurable GTP → GTP exchange activity of Sos routinely observed in in vitro assays that use fluorescently-labelled analogs of GTP. Overall, the data presents the first dynamic snapshot of Ras functional cycle as controlled by Sos.

EPB41L3, TSP-1 and RASSF2 as new clinically relevant prognostic biomarkers in diffuse gliomas

Hypermethylation of tumor suppressor genes is one of the hallmarks in the progression of brain tumors. Our objectives were to analyze the presence of the hypermethylation of EPB41L3, RASSF2 and TSP-1 genes in 132 diffuse gliomas (astrocytic and oligodendroglial tumors) and in 10 cases of normal brain, and to establish their association with the patients’ clinicopathological characteristics. Gene hypermethylation was analyzed by methylation-specific-PCR and confirmed by pyrosequencing (for EPB41L3 and TSP-1) and bisulfite-sequencing (for RASSF2). EPB41L3, RASSF2 and TSP-1 genes were hypermethylated only in tumors (29%, 10.6%, and 50%, respectively), confirming their cancer-specific role. Treatment of cells with the DNA-demethylating-agent 5-aza-2′-deoxycytidine restores their transcription, as confirmed by quantitative-reverse-transcription-PCR and immunofluorescence. Immunohistochemistry for EPB41L3, RASSF2 and TSP-1 was performed to analyze protein expression; p53, ki-67, and CD31 expression and 1p/19q co-deletion were considered to better characterize the tumors. EPB41L3 and TSP-1 hypermethylation was associated with worse (p = 0.047) and better (p = 0.037) prognosis, respectively. This observation was confirmed after adjusting the results for age and tumor grade, the role of TSP-1 being most pronounced in oligodendrogliomas (p = 0.001). We conclude that EPB41L3, RASSF2 and TSP-1 genes are involved in the pathogenesis of diffuse gliomas, and that EPB41L3 and TSP-1 hypermethylation are of prognostic significance.

Prognostic importance of RASSF2 expression in patients with gastric cancer who had undergone radical gastrectomy

BACKGROUND

Although Ras-association domain family of gene 2 (RASSF2) has been shown to undergo promoter methylation at high frequency in some cancer types and in brain metastases, its clinical utility as a useful prognostic molecular marker remains unclear in gastric cancer.

METHODS

Prognostic significance of RASSF2 expression was retrospectively analysed by immunohistochemically in 105 patients with gastric cancer who underwent curative gastrectomy.

RESULTS

Low RASSF2 expression was detected in 58 (55 %) patients, whereas 47 patients (45 %) had high RASSF2 expression. Lymph node involvement, pT stage, TNM stage, vascular invasion, perineural invasion and the presence of recurrence were found to be significantly related to RASSF2 expression levels. Low PRL-3 expression was closely correlated with lymph node metastasis (p = 0.001), advanced pT stage (p = 0.021), advanced TNM stage (p < 0.001), the presence of vascular invasion (p < 0.001), perineural invasion (p = 0.018) and high prevalence of recurrence (p = 0.003) compared with high RASSF2 expression. The median disease-free survival (DFS) time for patients with low RASSF2 expression was significantly worse than that of patients with high RASSF2 expression (10.2 vs. 50.6 months, p < 0.001). In addition, patients with high RASSF2 expression had the higher overall survival (OS) interval compared to patients with low RASSF2 expression (NR vs. 14.9 months, p < 0.001). In the multivariate analysis, the rate of RASSF2 expression levels was an independent prognostic factor, for DFS [p < 0.001, HR 0.12 (0.10-0.88)] and OS [p < 0.001, HR 0.10 (0.04-0.46)], as were pT stage and TNM stage, respectively.

CONCLUSIONS

RASSF2 may be an important molecular marker for carcinogenesis, prognosis and progression in gastric cancer, but the potential value of RASSF2 expression as a useful molecular marker in gastric cancer progression should be evaluated, comprehensively. It would be possible to develop treatments targeting RASSF2 and advance new treatment strategies for gastric cancer.

Aberrant expression and localization of deoxyribonucleic acid methyltransferase 3B in endometriotic stromal cells

OBJECTIVE

To define the expression and function of DNA methyltransferases (DNMTs) in response to decidualizing stimuli in endometriotic cells compared with healthy endometrial stroma.

DESIGN

Basic science.

SETTING

University research center.

PATIENT(S)

Premenopausal women with or without endometriosis.

INTERVENTION(S)

Primary cultures of stromal cells from healthy endometrium (E-IUM) or endometriomas (E-OSIS) were subjected to in vitro decidualization (IVD) using 1 μM medroxyprogesterone acetate, 35 nM 17β-estradiol, and 0.05 mM 8-Br-cAMP.

MAIN OUTCOME MEASURE(S)

Expression of DNMT1, DNMT3A, and DNMT3B in E-IUM and E-OSIS were assessed by quantitative real-time polymerase chain reaction and immunoblotting. Recruitment of DNMT3B to the promoters of steroidogenic factor 1 (SF-1) and estrogen receptor α (ESR1) was examined by chromatin immunoprecipitation.

RESULT(S)

IVD treatment reduced DNMT3B messenger RNA (74%) and protein levels (81%) only in E-IUM; DNMT1 and DNMT3A were unchanged in both cell types. Significantly more DNMT3B bound to the SF-1 promoter in E-IUM compared with E-OSIS, and IVD treatment reduced binding in E-IUM to levels similar to those in E-OSIS. Enrichment of DNMT3B across 3 ESR1 promoters was reduced in E-IUM after IVD, although the more-distal promoter showed increased DNMT3B enrichment in E-OSIS after IVD.

CONCLUSION(S)

The inability to downregulate DNMT3B expression in E-OSIS may contribute to an aberrant epigenetic fingerprint that misdirects gene expression in endometriosis and contributes to its altered response to steroid hormones.

Clinical utility of RASSF1A methylation in human malignancies

The high frequency of RASSF1A methylation has been noted in a vast number of patients in a broad spectrum of malignancies, suggesting that RASSF1A inactivation is associated with cancer pathogenesis. However, whether this recurrent incidence of RASSF1A hypermethylation in human malignancies and its association with more aggressive tumour phenotype is a frequent event across different cancer types has not yet been discussed. In this review, we interrogated existing evidence for association of RASSF1A hypermethylation with clinicopathological characteristics that can indicate more invasive lesions.

Differential role of gene hypermethylation in adenocarcinomas, squamous cell carcinomas and cervical intraepithelial lesions of the uterine cervix

Cervical cancer is the third most common cancer in women worldwide. The hypermethylation of P16, TSLC-1 and TSP-1 genes was analyzed in squamous cell carcinomas (SCC), cervical intraepithelial lesions (CIN) and adenocarcinomas (ADC) of the uterine cervix (total 181 lesions). Additionally human papillomavirus (HPV) type, EPB41L3, RASSF1 and RASSF2 hypermethylation were tested in ADC and the results were compared with those obtained previously by our group in SCC. P16, TSLC-1 and TSP-1 hypermethylation was more frequent in SCCs than in CINs. These percentages and the corresponding ones for EPB41L3, RASSF1 and RASSF2 genes were also higher in SCCs than in ADCs, except for P16. The presence of HPV in ADCs was lower than reported previously in SCC and CIN. Patients with RASSF1A hypermethylation showed significantly longer disease-free survival (P = 0.015) and overall survival periods (P = 0.009) in ADC patients. To our knowledge, this is the first description of the EPB41L3 and RASSF2 hypermethylation in ADCs. These results suggest that the involvement of DNA hypermethylation in cervical cancer varies depending on the histological type, which might contribute to explaining the different prognosis of patients with these types of tumors.

Piwil1 causes epigenetic alteration of PTEN gene via upregulation of DNA methyltransferase in type I endometrial cancer

Piwil1, a member of the Piwi family, has been well demonstrated to mediate tumorigenesis associated with DNA hypermethylation. It has been reported that Piwil1 is overexpressed in various types of cancer, including endometrial cancer. However, the underlying mechanism of Piwil1 in endometrial cancer remains largely unclear. PTEN exerts an important tumor suppressor role in endometrial carcinogenesis. The present study aimed to investigate whether Piwil1 could regulate the expression of PTEN. Herein, we found that Piwil1 could promote the loss of PTEN expression and increase aberrant hypermethylation of PTEN gene promoter in Ishikawa cells. We also found that Piwil1 could regulate the expression of DNA methyltransferase 1 (DNMT1). Silencing DNMT1 gene could upregulate the PTEN gene expression and change the methylation status of PTEN gene promoter in Ishikawa cells. These results suggested that Piwil1 caused the loss of PTEN expression through DNMT1-mediated PTEN hypermethylation. Taken together, these data provide a novel regulatory mechanism of Piwil1 in endometrial cancer.

Aberrant methylation of RASSF2A in tumors and plasma of patients with epithelial ovarian cancer

OBJECTIVE

The tumor suppressor gene, Ras-association domain family (RASSF)2A, is inactivated by promoter hypermethylation in many cancers. The current study was performed to evaluate the methylation status of RASSF2A in epithelial ovarian cancer (EOC) tissues and plasma, and correlations with gene expression and clinicopathologic characteristics.

METHOD

We detected methylation of the RASSF2A gene in tissues and corresponding plasma samples from 47 EOC patients and 14 patients with benign ovarian tumors and 10 with normal ovarian tissues. The methylation status was determined by methylation-specific PCR while gene expression of mRNA was examined by RT-PCR. The EOC cell line, SKOV3, was treated with 5-aza-2'-deoxycytidine (5-aza- dC).

RESULTS

RASSF2A mRNA expression was significantly low in EOC tissues. The frequency of aberrant methylation of RASSF2A was 51.1% in EOC tissues and 36.2% in corresponding plasma samples, whereas such hypermethylation was not detected in the benign ovarial tumors and normal ovarian samples. The expression of RASSF2A mRNA was significantly down-regulated or lost in the methylated group compared to the unmethylated group (p<0.05). After treatment with 5-aza-dC, RASSF2A mRNA expression was significantly restored in the Skov3 cell line.

CONCLUSION

Epigenetic inactivation of RASSF2A through aberrant promoter methylation may play an important role in the pathogenesis of EOC. Methylation of the RASSF2A gene in plasma may be a valuable molecular marker for the early detection of EOC.

Emerging drugs for endometrial cancer

INTRODUCTION

From the dualistic classification that divides endometrial cancer (EC) into two types with distinct underlying molecular profiling, histopathology and clinical behavior, arises a deeper understanding of the carcinogenesis pathways. EC treatment comprises different and multimodal therapeutic approaches, such as chemotherapy, radiation therapy or combinations of novel drugs; however, few of these regimens have truly improved progression-free or survival rates in advanced and metastatic settings.

AREAS COVERED

We reviewed the main molecular pathways involved in EC carcinogenesis through a wide literature search of novel compounds that alone or in combination with traditional drugs have been investigated or are currently under investigation in randomized clinical trials.

EXPERT OPINION

The molecular therapies mainly discussed in this review are potential therapeutic candidates for more effective and specific treatments. In the genomic era, a deeper knowledge about molecular characteristics of cancer provides the hope for the development of better therapeutic approaches. Targeting both genetic and epigenetic alterations, attacking tumor cells using cell-surface markers overexpressed in tumor tissue, reactivating antitumor immune responses and identifying predictive biomarkers represent the emerging strategies and the major challenges.

Comparative DNA methylome analysis of endometrial carcinoma reveals complex and distinct deregulation of cancer promoters and enhancers

BACKGROUND

Aberrant DNA methylation is a hallmark of many cancers. Classically there are two types of endometrial cancer, endometrioid adenocarcinoma (EAC), or Type I, and uterine papillary serous carcinoma (UPSC), or Type II. However, the whole genome DNA methylation changes in these two classical types of endometrial cancer is still unknown.

RESULTS

Here we described complete genome-wide DNA methylome maps of EAC, UPSC, and normal endometrium by applying a combined strategy of methylated DNA immunoprecipitation sequencing (MeDIP-seq) and methylation-sensitive restriction enzyme digestion sequencing (MRE-seq). We discovered distinct genome-wide DNA methylation patterns in EAC and UPSC: 27,009 and 15,676 recurrent differentially methylated regions (DMRs) were identified respectively, compared with normal endometrium. Over 80% of DMRs were in intergenic and intronic regions. The majority of these DMRs were not interrogated on the commonly used Infinium 450K array platform. Large-scale demethylation of chromosome X was detected in UPSC, accompanied by decreased XIST expression. Importantly, we discovered that the majority of the DMRs harbored promoter or enhancer functions and are specifically associated with genes related to uterine development and disease. Among these, abnormal methylation of transposable elements (TEs) may provide a novel mechanism to deregulate normal endometrium-specific enhancers derived from specific TEs.

CONCLUSIONS

DNA methylation changes are an important signature of endometrial cancer and regulate gene expression by affecting not only proximal promoters but also distal enhancers.

Aberrant promoter methylation and silencing of RASSF2A gene in cervical cancer

AIM

Ras association domain family (RASSF)2A as a negative effector of Ras protein is inactivated by promoter hypermethylation in many cancers. This study evaluated the methylation status of RASSF2A in cervical cancer (CC) and its correlation with clinicopathological characteristics.

METHODS

Methylation-specific polymerase chain reaction and reverse transcriptase polymerase chain reaction were utilized to analyze the methylation status and RASSF2A mRNA expression in four CC cell lines and tissue samples from 25 normal controls and 46 CC patients. The CC cell lines also were treated with the methyltransferase inhibitor 5-aza-2'-deoxycytidine (5-aza-dC).

RESULTS

Expression of RASSF2A was downregulated in all cell lines and CC tissue samples. Hypermethylation of RASSF2A was detected in all cell lines and 26 of 46 (56.5%) CC samples. No methylation of RASSF2A was found in the normal cervical tissues. A decreased level (P < 0.05) of RASSF2A expression was observed among RASSF2A-methylated CC cases (0.1002 ± 0.0377, mean ± standard deviation) compared to unmethylated cases (0.2882 ± 0.0642, mean ± standard deviation). After treatment with 5-aza-dC, loss of RASSF2A expression was restored in four CC cell lines. RASSF2A methylation was significantly different in patients with or without lymph node metastasis (90% vs 47.2%, respectively; P < 0.05).

CONCLUSION

Promoter hypermethylation of RASSF2A is observed in CC, while not in normal cervical tissues. RASSF2A is inactivated in CC by promoter hypermethylation and may play a role in cervical carcinogenesis.

DNA methyltransferases and TETs in the regulation of differentiation and invasiveness of extra-villous trophoblasts

Specialized cell types of trophoblast cells form the placenta in which each cell type has particular properties of proliferation and invasion. The placenta sustains the growth of the fetus throughout pregnancy and any aberrant trophoblast differentiation or invasion potentially affects the future health of the child and adult. Recently, the field of epigenetics has been applied to understand differentiation of trophoblast lineages and embryonic stem cells (ESC), from fertilization of the oocyte onward. Each trophoblast cell-type has a distinctive epigenetic profile and we will concentrate on the epigenetic mechanism of DNA methyltransferases and TETs that regulate DNA methylation. Environmental factors affecting the mother potentially regulate the DNA methyltransferases in trophoblasts, and so do steroid hormones, cell cycle regulators, such as p53, and cytokines, especially interlukin-1β. There are interesting questions of why trophoblast genomes are globally hypomethylated yet specific genes can be suppressed by hypermethylation (in general, tumor suppressor genes, such as E-cadherin) and how invasive cell-types are liable to have condensed chromatin, as in metastatic cancer cells. Future work will attempt to understand the interactive nature of all epigenetic mechanisms together and their effect on the complex biological system of trophoblast differentiation and invasion in normal as well as pathological conditions.

The tumor suppressor gene, RASSF1A, is essential for protection against inflammation -induced injury

Ras association domain family protein 1A (RASSF1A) is a tumor suppressor gene silenced in cancer. Here we report that RASSF1A is a novel regulator of intestinal inflammation as Rassf1a^+/−, Rassf1a^−/− and an intestinal epithelial cell specific knockout mouse (Rassf1a ^IEC-KO) rapidly became sick following dextran sulphate sodium (DSS) administration, a chemical inducer of colitis. Rassf1a knockout mice displayed clinical symptoms of inflammatory bowel disease including: increased intestinal permeability, enhanced cytokine/chemokine production, elevated nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB) activity, elevated colonic cell death and epithelial cell injury. Furthermore, epithelial restitution/repair was inhibited in DSS-treated Rassf1a^−/− mice with reduction of several makers of proliferation including Yes associated protein (YAP)-driven proliferation. Surprisingly, tyrosine phosphorylation of YAP was detected which coincided with increased nuclear p73 association, Bax-driven epithelial cell death and p53 accumulation resulting in enhanced apoptosis and poor survival of DSS-treated Rassf1a knockout mice. We can inhibit these events and promote the survival of DSS-treated Rassf1a knockout mice with intraperitoneal injection of the c-Abl and c-Abl related protein tyrosine kinase inhibitor, imatinib/gleevec. However, p53 accumulation was not inhibited by imatinib/gleevec in the Rassf1a^−/− background which revealed the importance of p53-dependent cell death during intestinal inflammation. These observations suggest that tyrosine phosphorylation of YAP (to drive p73 association and up-regulation of pro-apoptotic genes such as Bax) and accumulation of p53 are consequences of inflammation-induced injury in DSS-treated Rassf1a^−/− mice. Mechanistically, we can detect robust associations of RASSF1A with membrane proximal Toll-like receptor (TLR) components to suggest that RASSF1A may function to interfere and restrict TLR-driven activation of NFκB. Failure to restrict NFκB resulted in the inflammation-induced DNA damage driven tyrosine phosphorylation of YAP, subsequent p53 accumulation and loss of intestinal epithelial homeostasis.

RASSF2 hypermethylation is present and related to shorter survival in squamous cervical cancer

Ras association (RalGDS/AF-6) domain family member 2 (RASSF2) is a gene involved in the progression of several human cancers, including breast, colorectal and lung cancer. The aims of this study were to determine the hypermethylation of the gene in squamous cervical cancer and precursor lesions, along with that of RASSF1 and the recently described EPB41L3, and to analyze the potential prognostic role of these genes. Methylation-specific PCR and bisulfite sequencing were used to analyze the methylation status of RASSF2 and EPB41L3 gene in 60 squamous cervical cancer, 76 cervical intraepithelial neoplasias grade III, 16 grade II, 14 grade I and 13 cases of normal tissue adjacent to cervical intraepithelial neoplasia. RASSF2 expression was evaluated by immunohistochemistry and the re-expression of RASSF2 and EPB41L3 was analyzed by quantitative reverse-transcription PCR in HeLa, SiHa, C33A and A431 cell lines treated with 5-aza-2'-deoxycytidine and/or trichostatin. RASSF1 hypermethylation and human papillomavirus type were also analyzed in all the cases by methylation-specific PCR and reverse line blot, respectively. RASSF2 hypermethylation was predominant in squamous cervical cancer (60.9%) compared with cervical intraepithelial neoplasias (4.2%) and was associated with a lower level of RASSF2 expression and vascular invasion in squamous cervical cancer. EPB41L3 and RASSF1 hypermethylations were also more frequent in cancer than in precursor lesions. Patients with RASSF2 hypermethylation had shorter survival time, independent of tumor stage (hazard ratio: 6.0; 95% confidence interval: 1.5-24.5). Finally, the expressions of RASSF2 and EPB41L3 were restored in several cell lines treated with 5-aza-2'-deoxycytidine. Taken together, our results suggest that RASSF2 potentially functions as a new tumor-suppressor gene that is inactivated through hypermethylation in cervical cancer and is related to the bad prognosis of these patients.

Emerging therapeutic biomarkers in endometrial cancer

Although clinical trials of molecular therapies targeting critical biomarkers (mTOR, epidermal growth factor receptor/epidermal growth factor receptor 2, and vascular endothelial growth factor) in endometrial cancer show modest effects, there are still challenges that might remain regarding primary/acquired drug resistance and unexpected side effects on normal tissues. New studies that aim to target both genetic and epigenetic alterations (noncoding microRNA) underlying malignant properties of tumor cells and to specifically attack tumor cells using cell surface markers overexpressed in tumor tissue are emerging. More importantly, strategies that disrupt the cancer stem cell/epithelial-mesenchymal transition-dependent signals and reactivate antitumor immune responses would bring new hope for complete elimination of all cell compartments in endometrial cancer. We briefly review the current status of molecular therapies tested in clinical trials and mainly discuss the potential therapeutic candidates that are possibly used to develop more effective and specific therapies against endometrial cancer progression and metastasis.

OCT4 is epigenetically regulated by DNA hypomethylation of promoter and exon in primary gliomas

Glioma is the leading cause of tumor-related mortality in the central nervous system. There is increasing evidence that the self-renewal capacity of cancer cells is critical for the initiation, growth and recurrence of tumors. OCT4 is a transcription factor that plays a key role in regulating the self-renewal ability of embryonic stem cells. DNA methylation is involved in the regulation of OCT4 expression during the development and differentiation of embryonic stem cells and neural stem cells. In the present study, we reported that OCT4 was highly expressed in primary gliomas and its expression levels increased in parallel with pathological grades. BSP analysis showed that the methylation levels of OCT4 gene promoter and exon were significantly reduced in comparison with the normal group and were negatively correlated with OCT4 gene expression in primary gliomas. In vitro, OCT4 gene expression was upregulated following treatment by a demethylation reagent in glioma cell lines. Our findings suggest that OCT4 is epigenetically regulated by DNA hypomethylation in primary gliomas, which may provide evidence for the role of DNA methylation in tumor and may present a new direction for developing more powerful strategies to treat glioma in the clinic.

Protein expression, mRNA expression and gene amplification of DNA methyltransferase 1 in endometrial tumor tissues

Inactivation of tumor suppressor genes by methylation is an important pathway in the multi-step process of carcinogenesis. This aim of this study was to investigate the expression of DNA methyltransferase 1 (DNMT1) which strongly contributes to the methylation process in endometrial normal and tumor tissues. Moreover, a correlation with the expression of hMLH1 and E-cadherin that was inactivated in a number of endometrial cancers was observed. Samples were obtained from 8 cases of normal endometrium, 10 cases of hyperplasia, 11 cases of atypical hyperplasia and 38 cases of carcinoma. DNMT1 expression was correlated with tumor progression (P=0.0023), as well as with the attenuation of hMLH1 and E-cadherin expression (P=0.031 and 0.031, respectively). No attenuation of hMLH1 and E-cadherin expression was observed in DNMT1-negative cases. Thus, the investigation of DNMT1 expression in clinical samples was shown to be useful in identifying the conditions that are related to general methylation. Overexpression of DNMT1 microRNA (mRNA) was mainly observed in carcinomas. Gene amplification occurred with tumor development. Gene amplification of DNMT1 was correlated with the expression of DNMT1 protein (P=0.041). In conclusion, overexpression of DNMT1 protein is caused by various factors, one of which is gene amplification.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone induces retinoic acid receptor β hypermethylation through DNA methyltransferase 1 accumulation in esophageal squamous epithelial cells

Overexpression of DNA methyltransferase 1 (DNMT1) has been detected in many cancers. Tobacco exposure is known to induce genetic and epigenetic changes in the pathogenesis of malignancy. 4-(Methylnitrosamino)- 1-(3-pyridyl)-1-butanone (NNK) is an important carcinogen present in tobacco smoke; however the detailed molecular mechanism of how NNK induces esophageal carcinogenesis is still unclear. We found that DNMT1 was overexpressed in ESCC tissues compared with paired non-cancerous tissues, the overexpression being correlated with smoking status and low expression of RARβ. The latter could be upregulated by NNK treatment in Het-1A cells, and the increased DNMT1 expression level reflected promoter hypermethylation and downregulation of retinoic acid receptor β (RARβ). RNA interference mediated knockdown of DNMT1 resulted in promoter demethylation and upregulation of RARβ in KYSE30 and TE-1 cells. 3-(4,5-Dimethyl-thiazol-2yl)- 2,5-diphenyltetrazolium bromide (MTT) and flow cytometric analysis demonstrated that NNK treatment in Het- 1A cells could enhance cell proliferation and inhibit cell apoptosis in a dose-dependent manner. In conclusion, DNMT1 overexpression is correlated with smoking status and low expression of RARβ in esophageal SCC patients. NNK could induce RARβ promoter hypermethylation through upregulation of DNMT1 in esophageal squamous epithelial cells, finally leading to enhancement of cell proliferation and inhibition of apoptosis.

Loss of heterozygosity and methylation of multiple tumor suppressor genes on chromosome 3 in hepatocellular carcinoma

BACKGROUND

Genetic and epigenetic alterations are the two key mechanisms in the development of hepatocellular carcinoma (HCC). However, how they contribute to hepatocarcinogenesis and the correlation between them has not been fully elucidated.

METHODS

A total of 48 paired HCCs and noncancerous tissues were used to detect loss of heterozygosity (LOH) and the methylation profiles of five tumor suppressor genes (RASSF1A, BLU, FHIT, CRBP1, and HLTF) on chromosome 3 by using polymerase chain reaction (PCR) and methylation-specific PCR. Gene expression was analyzed by immunohistochemistry and reverse transcription (RT)-PCR.

RESULTS

Sixteen of 48 (33.3 %) HCCs had LOH on at least one locus on chromosome 3, and two smallest common deleted regions (3p22.3-24.3 and 3p12.3-14.2) were identified. RASSF1A, BLU, and FHIT showed very high frequencies of methylation in HCCs (100, 81.3, and 64.6 %, respectively) and noncancerous tissues, but not in liver tissues from control patients. Well-differentiated HCCs showed high methylation frequencies of these genes but very low frequencies of LOH. Furthermore, BLU methylation was associated with an increased level of alpha-fetoprotein, and FHIT methylation was inversely correlated with HCC recurrence. In comparison, CRBP1 showed moderate frequencies of methylation, while HLTF showed low frequencies of methylation, and CRBP1 methylation occurred mainly in elderly patients. Treatment with 5-aza-2'-deoxycytidine demethylated at least one of these genes and restored their expression in a DNA methylation-dependent or -independent manner.

CONCLUSIONS

Hypermethylation of RASSF1A, BLU, and FHIT is a common and very early event in hepatocarcinogenesis; CRBP1 methylation may also be involved in the later stage. Although LOH was not too frequent on chromosome 3, it may play a role as another mechanism in hepatocarcinogenesis.

HBP1-mediated transcriptional regulation of DNA methyltransferase 1 and its impact on cell senescence

The activity of DNA methyltransferase 1 (DNMT1) is associated with diverse biological activities, including cell proliferation, senescence, and cancer development. In this study, we demonstrated that the HMG box-containing protein 1 (HBP1) transcription factor is a new repressor of DNMT1 in a complex mechanism during senescence. The DNMT1 gene contains an HBP1-binding site at bp -115 to -134 from the transcriptional start site. HBP1 repressed the endogenous DNMT1 gene through sequence-specific binding, resulting in both gene-specific (e.g., p16(INK4)) and global DNA hypomethylation changes. The HBP1-mediated repression by DNMT1 contributed to replicative and premature senescence, the latter of which could be induced by Ras and HBP1 itself. A detailed investigation unexpectedly revealed that HBP1 has dual and complex transcriptional functions, both of which contribute to premature senescence. HBP1 both repressed the DNMT1 gene and activated the p16 gene in premature senescence. The opposite transcriptional functions proceeded through different DNA sequences and differential protein acetylation. While intricate, the reciprocal partnership between HBP1 and DNMT1 has exceptional importance, since its abrogation compromises senescence and promotes tumorigenesis. Together, our results suggest that the HBP1 transcription factor orchestrates a complex regulation of key genes during cellular senescence, with an impact on overall DNA methylation state.

Expression of DNA methyltransferases in the mouse uterus during early pregnancy and susceptibility to dietary folate deficiency

We have characterized the uterine expression of DNA methyltransferases (DNMTs) during early pregnancy in mice and determined whether a folate-deficient diet (FDD) can affect DNMTs in this context. Within endometrial cells, expressions of DNMT (cytosine-5) 1 (Dnmt1), Dnmt3a, and Dnmt3b were significantly elevated during the prereceptive phase of pregnancy but generally returned to baseline levels during receptive and postimplantation periods. As such, the transcription of DNMT genes is temporally regulated during early pregnancy. When comparisons were made between implantation sites (IS) and inter-IS on day 5 of pregnancy, lower levels of Dnmt3a were detected at IS. Comparisons between IS and inter-IS did not reveal significant expression differences for other DNMT genes. When tissue sections were examined, DNMT3A was specifically lower in the stroma of IS. Reduced DNMT1 and DNMT3B levels were also observed in the luminal and glandular epithelia of IS, whereas no obvious differences in the stroma were detected. In pseudo-pregnant mice subjected to a FDD, levels of Dnmt1 and Dnmt3a (but not Dnmt3b) were significantly upregulated in endometrial tissues, as compared with controls. When tissues from these folate-deficient mice were examined, DNMT1 levels were elevated in both the luminal and glandular epithelia, whereas DNMT3A was upregulated in the luminal epithelium and the stroma. A slight increase in DNMT3B levels was detected in the glandular epithelium. These results indicate that DNMTs may regulate the transcription of endometrial genes associated with embryo implantation and that levels of DNMTs are affected by dietary folate in mice.

DNA methylation profiles in precancerous tissue and cancers: carcinogenetic risk estimation and prognostication based on DNA methylation status

Alterations in DNA methylation, which are associated with DNA methyltransferase abnormalities and result in silencing of tumor-related genes and chromosomal instability, are involved even in precancerous changes in various organs. DNA methylation alterations also account for the histological heterogeneity and clinicopathological diversity of human cancers. Therefore, we have analyzed DNA methylation on a genome-wide scale in clinical tissue samples. Our approach using the bacterial artificial chromosome array-based methylated CpG island amplification method has revealed that DNA methylation alterations correlated with the future development of more malignant cancers are already accumulated at the precancerous stage in the kidney, liver and urinary tract. DNA methylation profiles at precancerous stages are basically inherited by the corresponding cancers developing in individual patients. Such DNA methylation alterations may confer vulnerability to further genetic and epigenetic alterations, generate more malignant cancers, and thus determine patient outcome. On the basis of bacterial artificial chromosome array-based methylated CpG island amplification data, indicators for carcinogenetic risk estimation have been established using liver tissue specimens from patients with hepatitis virus infection, chronic hepatitis and liver cirrhosis or histologically normal urothelia, and for prognostication using biopsy or surgically resected specimens from patients with renal cell carcinoma, hepatocellular carcinoma and urothelial carcinoma. Such genome-wide DNA methylation profiling has now firmly established the clinical relevance of translational epigenetics.

The genomics and genetics of endometrial cancer

Most sporadic endometrial cancers (ECs) can be histologically classified as endometrioid, serous, or clear cell. Each histotype has a distinct natural history, clinical behavior, and genetic etiology. Endometrioid ECs have an overall favorable prognosis. They are typified by high frequency genomic alterations affecting PIK3CA, PIK3R1, PTEN, KRAS, FGFR2, ARID1A (BAF250a), and CTNNB1 (β-catenin), as well as epigenetic silencing of MLH1 resulting in microsatellite instability. Serous and clear cell ECs are clinically aggressive tumors that are rare at presentation but account for a disproportionate fraction of all endometrial cancer deaths. Serous ECs tend to be aneuploid and are typified by frequent genomic alterations affecting TP53 (p53), PPP2R1A, HER-2/ERBB2, PIK3CA, and PTEN; additionally, they display dysregulation of E-cadherin, p16, cyclin E, and BAF250a. The genetic etiology of clear cell ECs resembles that of serous ECs, but it remains relatively poorly defined. A detailed discussion of the characteristic patterns of genomic alterations that distinguish the three major histotypes of endometrial cancer is reviewed herein.

Aberrant methylation of RASSF2A in human pancreatic ductal adenocarcinoma and its relation to clinicopathologic features

OBJECTIVES

Tumor suppressor gene Ras-association domain family 2A (RASSF2A) is inactivated by promoter hypermethylation in many cancers. The study was performed to evaluate the methylation status of RASSF2A in pancreatic ductal adenocarcinoma and cell lines and its relation to clinicopathologic features.

METHODS

The RASSF2 expression in 8 pancreatic carcinoma cell lines and 1 normal pancreatic tissue was detected. The methylation status of RASSF2A in 8 pancreatic carcinoma cell lines, 41 cases of pancreatic ductal adenocarcinoma, and corresponding normal pancreatic tissue was also examined by methylation-specific PCR. BxPC-3 and AsPC-1 cell lines were treated with 5-aza-2'-deoxycytidine (5-aza-dC), and RASSF2 expression was determined by quantitative real-time reverse transcriptase-polymerase chain reaction.

RESULTS

The expression of RASSF2 was down-regulated in all cell lines. Hypermethylation of RASSF2A was detected in all cell lines and 9 of 41 pancreatic ductal adenocarcinomas. Whereas none of hypermethylation of RASSF2A was found in the normal pancreatic tissue. The expression of RASSF2 could be restored by 5-aza-dC in cell lines.

CONCLUSIONS

Promoter hypermethylation of RASSF2A is observed in pancreatic ductal adenocarcinoma, while not in normal pancreatic tissue. RASSF2A is inactivated in pancreatic ductal adenocarcinoma by CpG island promoter hypermethylation and may play a role in pancreatic carcinogenesis.

Effects of DNA methyltransferase 1 inhibition on esophageal squamous cell carcinoma

To explore the role of DNA methyltransferase 1 (DNMT1) in esophageal squamous cell carcinoma (ESCC) and the potential of DNMT1-targeted small interfering RNA as ESCC therapy, we examined expression changes of DNMT1 in ESCC and investigated the effect of DNMT1 knockdown by RNA interference in a human ESCC cell line, KYSE30. DNMT1 messenger RNA was over-expressed in seven out of 12 ESCC samples, and the percentage of cells expressing DNMT1 was significantly higher in ESCC tissues compared with paired non-cancerous tissues. DNMT1 protein levels correlated with lymph node metastasis, but exhibited no correlation with sex, age, tumor site, or tumor differentiation. Knockdown of DNMT1 in KYSE30 cells using RNA interference resulted in a reduction of promoter methylation and re-expression of methyl-guanine methyl-transferase and retinoic acid receptors beta, inhibition of cell proliferation/viability and induction of cell apoptosis. These results indicate that DNMT1 over-expression is involved in ESCC and correlated with lymph node metastasis. Knockdown of DNMT1 led to promoter demethylation and re-expression of several tumor suppressor genes thereby inhibiting cell proliferation/viability and inducing cell apoptosis.

A common genetic variant (97906C>A) of DAB2IP/AIP1 is associated with an increased risk and early onset of lung cancer in Chinese males

DOC-2/DAB2 interactive protein (DAB2IP) is a novel identified tumor suppressor gene that inhibits cell growth and facilitates cell apoptosis. One genetic variant in DAB2IP gene was reported to be associated with an increased risk of aggressive prostate cancer recently. Since DAB2IP involves in the development of lung cancer and low expression of DAB2IP are observed in lung cancer, we hypothesized that the variations in DAB2IP gene can increase the genetic susceptibility to lung cancer. In a case-control study of 1056 lung cancer cases and 1056 sex and age frequency-matched cancer-free controls, we investigated the association between two common polymorphisms in DAB2IP gene (-1420T>G, rs7042542; 97906C>A, rs1571801) and the risk of lung cancer. We found that compared with the 97906CC genotypes, carriers of variant genotypes (97906AC+AA) had a significant increased risk of lung cancer (adjusted odds ratio [OR] = 1.33, 95%CI = 1.04-1.70, P = 0.023) and the number of variant (risk) allele worked in a dose-response manner (P(trend) = 0.0158). Further stratification analysis showed that the risk association was more pronounced in subjects aged less than 60 years old, males, non-smokers, non-drinkers, overweight groups and in those with family cancer history in first or second-degree relatives, and the 97906A interacted with overweight on lung cancer risk. We further found the number of risk alleles (97906A allele) were negatively correlated with early diagnosis age of lung cancer in male patients (P = 0.003). However, no significant association was observed on the -1420T>G polymorphism. Our data suggested that the 97906A variant genotypes are associated with the increased risk and early onset of lung cancer, particularly in males.

Expression and regulation of DNA methyltransferases in human endometrium

The messenger RNA of the DNA methyltransferases DNMT3a and DNMT3b are expressed temporally in the endometrium across the menstrual cycle, as is the steroid hormone regulation of DNMT1, DNMT3a, and DNMT3b. This suggests that DNA methylation in endometrium is changeable during the menstrual cycle and potentially alters gene expression.

Current concepts in the pathology and epigenetics of endometrial carcinoma

In the Western world, endometrial carcinoma is the most common malignant tumour of the female genital tract and is the fourth most common cancer in women. Two different clinicopathological subtypes are recognised: the oestrogen-related (type I, endometrioid) and the non-oestrogen related (type II, non-endometrioid). This article reviews the epidemiology, risk factors, genetic alterations during endometrial carcinogenesis, features of tumours and precursors and early detection of the disease. Insights into the epigenetic alterations, with emphasis on DNA methylation during endometrial carcinogenesis, and their diagnostic value are also provided.

DNA methylation in endometrial cancer

Endometrial cancer is the most commonly diagnosed gynecological cancer, and it has been shown to be a complex disease driven by abnormal genetic, and epigenetic alterations, as well as environmental factors. Epigenetic changes resulting in aberrant gene expression are dynamic and modifiable features of many cancer types. A significant epigenetic change is aberrant DNA methylation. In this review, we review evidence on the role of aberrant DNA methylation, examining changes in relation to endometrial carcinogenesis, and report on recent advances in the understanding of the contribution of aberrant DNA methylation to endometrial cancer with the emphasis on the role of dietary/ lifestyle and environmental factors, as well as opportunities and challenges of DNA methylation in endometrial cancer management and prevention.

Hypermethylation of SOX2 Promoter in Endometrial Carcinogenesis

This paper aimed at investigating the expression and methylation profiles of SOX2, a gene coding for the stem cell-related transcription factor SOX2, in endometrial carcinomas. By methylation-specific polymerase chain reaction (MS-PCR), the methylation status of SOX2 promoter region in 72 endometrial carcinomas and 12 normal endometrial samples was examined. Methylated allele was found in 37.5% (27/72) of endometrial carcinomas but only in 8.3% (1/12) of normal endometrial, significantly more frequent in cancers (P = .0472). SOX2 mRNA level was significantly reduced in endometrial carcinoma compared with nonneoplastic endometrium (P = .045). A significant correlation between SOX2 mRNA expression and hypermethylation of SOX2 was found (P = .024). Hypermethylation of SOX2 tended to be more frequently found in type II serous or clear cell adenocarcinoma. SOX2 methylation was also significantly correlated with shorter survival of patients (P = .046). In conclusion, epigenetic mechanisms may play a crucial role on the transcriptional regulation of SOX2 and loss of SOX2 expression may be related to endometrial carcinogenesis.

Differential expression and phosphorylation of Pak1 and Pak2 in ovarian cancer: effects on prognosis and cell invasion

Ovarian cancer is a gynecological malignancy with high mortality. Therefore, the identification of novel prognostic and therapeutic targets is important. p21-activated kinases (Paks) are involved in cytoskeleton reorganization. This study investigated the clinical significance of total and phosphorylated (p) Pak1 and Pak2 as well as their functional roles in ovarian cancer. Expressions of Pak1, p-Pak1 Thr(212), Pak2 and p-Pak2 Ser(20) in ovarian normal and cancerous cell lines as well as in clinical samples of ovarian tumors were evaluated. The effects of Pak1 and Pak2 on ovarian cancer cell functions were determined. Pak1, p-Pak1 and p-Pak2 were overexpressed in ovarian cancer cell lines, and clinical samples of ovarian cancers were compared with benign ovarian lesions/inclusion cysts. Similar Pak2 expression levels were observed among normal and cancerous cell lines and clinical samples. After multiple testing correction, high Pak1 and nuclear p-Pak1 expression in ovarian cancers was significantly associated with histological type and tumor grade, respectively. Pak1 and p-Pak1 expression was associated with poor overall and disease-free survival. Pak1 was an independent prognostic factor. Knockdown of Pak1 and Pak2 in ovarian cancer cell lines reduced cell migration and invasion but did not affect cell proliferation and apoptosis. Knockdown of Pak1 also reduced p38 activation and downregulated vascular endothelial growth factor. Conversely, ectopic Pak1 overexpression enhanced ovarian cancer cell migration and invasion in a kinase-dependent manner, along with increased p38 activation. Our findings suggest that Pak1, p-Pak1 and p-Pak2 play important roles in ovarian carcinogenesis. Pak1 and p-Pak1 may be potential prognostic markers and therapeutic molecular targets in ovarian cancer.

Epigenetic regulation of endometrium during the menstrual cycle

The endometrium undergoes morphological and functional changes during the menstrual cycle which are essential for uterine receptivity. These changes are driven by estrogen and progesterone and involve the fine control of many different genes-several of which have been identified as being epigenetically regulated. Epigenetic modification may therefore influence the functional changes in the endometrium required for successful implantation. There is, however, only limited information on epigenetic regulation in endometrium. We review the potential role of epigenetic regulation of key processes during the menstrual cycle and present our own findings following a preliminary study into global acetylation levels in the human endometrium. A changing epigenetic state is associated with the differentiation of stem cells into different lineages and thus may be involved in endometrial regeneration. Histone acetylation is implicated in the vascular endothelial growth factor pathway during angiogenesis, and studies using histone deacetylase inhibitors suggest an involvement in endometrial proliferation and differentiation. The processes of decidualization and implantation are also associated with epigenetic change and epigenetic modulators show variable expression across the menstrual cycle. Our own studies found that endometrial global histone acetylation, as determined by western blotting, changed throughout the menstrual cycle and correlated well with expected transcription activity during the different phases. This suggests that epigenetics may be involved in the regulation of endometrial gene expression during the menstrual cycle and that abnormal epigenetic modifications may therefore be associated with implantation failure and early pregnancy loss as well as with other endometrial pathologies.