Promoter CpG Island Methylation Research Articles

MicroRNA Promoter Methylation in Colorectal Cancer

Colorectal cancer (CRC) is one of the most common cancers worldwide. The beginning and progression of the disease are thought to be determined by combinations of epigenetic and genetic changes that trigger multistep programs of carcinogenesis. In colorectal cancer, epigenetic alterations, in particular promoter CpG island methylation, occur more commonly than genetic mutations. Hyper-methylation contributes to carcinogenesis via inducing transcriptional silencing or down-regulation of tumor suppressor genes. DNA methylation alteration has a high potential for minimally invasive biomarker identification. Genome analysis has confirmed that microRNA expression is deregulated in most cancer types through several mechanisms, including failings in the microRNA biogenesis machinery. Moreover, microRNAs can be dysregulated by abnormal CpG methylation in cancer. Since it is believed that epigenetic changes occur in the early stages of the disease, these changes can be used for the early detection of cancer. In this review, we intend to study the role of microRNA gene promoter methylation in colorectal cancer.

Non-Canonical Functions of the ARF Tumor Suppressor in Development and Tumorigenesis.

P14ARF (ARF; Alternative Reading Frame) is an extensively characterized tumor suppressor which, in response to oncogenic stimuli, mediates cell cycle arrest and apoptosis via p53-dependent and independent routes. ARF has been shown to be frequently lost through CpG island promoter methylation in a wide spectrum of human malignancies, such as colorectal, prostate, breast, and gastric cancers, while point mutations and deletions in the p14ARF locus have been linked with various forms of melanomas and glioblastomas. Although ARF has been mostly studied in the context of tumorigenesis, it has been also implicated in purely developmental processes, such as spermatogenesis, and mammary gland and ocular development, while it has been additionally involved in the regulation of angiogenesis. Moreover, ARF has been found to hold important roles in stem cell self-renewal and differentiation. As is often the case with tumor suppressors, ARF functions as a pleiotropic protein regulating a number of different mechanisms at the crossroad of development and tumorigenesis. Here, we provide an overview of the non-canonical functions of ARF in cancer and developmental biology, by dissecting the crosstalk of ARF signaling with key oncogenic and developmental pathways.

RUNX3 promoter methylation is associated with oral squamous cell carcinoma location

The aetiology of OSCC remains unclear, however, aberrant methylation of CpG island promoters of tumor suppressor genes have been identified as contributory developmental pathways in several cancers. The aim of this study was to determine the presence of RUNX3 gene methylation and how its association with patients? demographic variables such as gender, age, histologic class and tumor location could be of diagnostic value for OSCC. Sixty-seven formalin-fixed paraffin-embedded (FFPE) solid tissue blocks of OSCC, and nine blocks of benign oral lesions of epithelial origin retrieved from the archives of the Department of Oral Pathology, University College Hospital, Ibadan, South-West Nigeria were used for the analyses. Frequency of CpG island methylation in the promoter region of RUNX3 was determined by methylation-specific polymerase chain reaction (MSP). Association between gender, age, tumor location, histologic class and promoter methylation in RUNX3 was assessed with Pearson?s ?2 test. Overall, 45% (30/67) of OSCC demonstrated methylation in the RUNX3 promoter indicating a high frequency of methylation of the CpG island promoter region of RUNX3. There was no association between gender, age, histologic class and promoter methylation in RUNX3 (P > 0.05), however a significant association was observed between tumor location and promoter methylation of RUNX3 (P < 0.05). Aberrant methylation of the CpG island promoter region of RUNX3 together with tumor location could therefore be critical in the development and diagnosis of OSCC.

Methylated PLK2 is a prognostic biomarker in taxane-treated breast cancers

Background: In search of potential biomarkers of drug responsiveness the tumour suppressor PLK2 has been identified as a mediator of taxane sensitivity in some tumour types, based on its role of G2M checkpoint regulation.Objective: The current study set out to evaluate PLK2 methylation in breast cancer treated with neo-adjuvant chemotherapy including a taxane, as a biomarker of disease progression.Methods: Silencing of PLK2 in MCF-7 cells followed by taxane treatment was assessed using apoptotic readout for proof of principle. DNA was extracted from 64 cases of diagnostic surgical FFPE sections. Using pyrosequencing, levels of PLK2 promoter methylation were measured.Results: Silencing of PLK2 resulted in a significantly reduced apoptotic response following paclitaxel treatment (compared with scramble transfected controls). An association with higher levels of CpG island promoter methylation was seen for those cases with a progression-free survival (PFS) of less than 12 months. Kaplan-Meier analysis showed there was an association between overall survival (OS) and level of methylation (p = .06).Conclusions: Thus, based on data obtained from this pilot study, further larger studies evaluating the utility of PLK2 methylation as a potential predictive biomarker in breast cancer are warranted.

Demethylation of the RB1 promoter concomitant with reactivation of TET2 and TET3 impairs gastric carcinogenesis in K19-Wnt1/C2mE transgenic mice

Aberrant methylation of promoter CpG islands (CGIs) can inactivate the expression of many tumor suppressor genes and play an important role in the carcinogenesis of gastric cancer. The tumor suppressor gene RB1, which encodes a cell cycle regulator, is hypermethylated and downregulated in multiple kinds of cancer. Activation of RB1 expression through DNA demethylation is a potential strategy for the treatment of gastric cancer. Herein, we found that the methylation status of the RB1 promoter was negatively related to the development of gastric tumors, while its expression was positively correlated with TET2 and TET3 expression. Further reactivation of RB1 expression by curcumin could inhibit gastric cell viability and carcinogenesis both in vitro and in vivo. Molecular docking and other studies confirmed that curcumin could bind to and upregulate the expression of TET2 and TET3 with hydrogen bonds and arene-H bonds, suggesting that demethylation of RB1 was attributed to reactivation of the demethylation enzymes TET2 and TET3 after curcumin treatment. Thus, our findings reveal a promising therapeutic strategy for gastric cancer prevention and treatment through RB1 demethylation and reactivation.

Methylation-mediated down-regulation of microRNA-497-195 cluster confers osteogenic differentiation in ossification of the posterior longitudinal ligament of the spine via ADORA2A.

Aberrant expression of microRNAs (miRNAs) has been associated with spinal ossification of the posterior longitudinal ligament (OPLL). Our initial bioinformatic analysis identified differentially expressed ADORA2A in OPLL and its regulatory miRNAs miR-497 and miR-195. Hence, this study was conducted to clarify the functional relevance of miR-497-195 cluster in OPLL, which may implicate in Adenosine A2A (ADORA2A). PLL tissues were collected from OPLL and non-OPLL patients, followed by quantification of miR-497, miR-195 and ADORA2A expression. The expression of miR-497, miR-195 and/or ADORA2A was altered in posterior longitudinal ligament (PLL) cells, which then were stimulated with cyclic mechanical stress (CMS). We validated that ADORA2A was expressed highly, while miR-497 and miR-195 were down-regulated in PLL tissues of OPLL patients. miR-195 and miR-497 expression in CMS-treated PLL cells was restored by a demethylation reagent 5-aza-2'-deoxycytidine (AZA). Moreover, expression of miR-195 and miR-497 was decreased by promoting promoter CpG island methylation. ADORA2A was verified as the target of miR-195 and miR-497. Overexpression of miR-195 and miR-497 diminished expression of osteogenic factors in PLL cells by inactivating the cAMP/PKA signaling pathway via down-regulation of ADORA2A. Collectively, miR-497-195 cluster augments osteogenic differentiation of PLL cells by inhibiting ADORA2A-dependent cAMP/PKA signaling pathway.

Integrated single-cell spatial multi-omics of intratumor heterogeneity in renal cell carcinoma.

e17106 Background: Clear cell renal cell carcinoma (ccRCC) exhibits conspicuous intratumor heterogeneity (ITH) - a driver of tumor evolution and metastasis. ITH in RCC has been studied extensively with bulk tumor DNA sequencing, which lacks the ability to integrate single cell resolution data, spatial architecture, and microenvironment composition. Therefore, we analyzed primary ccRCC tumors at multiple biopsy sites with CyTOF, multiplex immunofluorescence (MxIF), whole exome sequencing (WES), RNA sequencing (RNA-seq), single nuclei RNA-seq (snRNA-seq), and whole genome bisulfite sequencing (WGBS). Methods: Primary ccRCC tumors collected from 6 patients (pts) were biopsied at multiple locations and subjected to CyTOF (n = 21 sites, 6 pts), MxIF (20 markers, n = 8 sites, 3 pts), WES (n = 8 sites, 3 pts), RNA-seq (n = 8 sites, 3 pts), snRNA-seq (n = 8 sites, 3 pts), and WGBS (n = 8 sites, 3 pts), enabling integrated multi-omics analysis. MxIF, CyTOF, and genomic/transcriptomic analyses were performed by BostonGene. Results: Genomic intratumor (IT) evolution of ccRCC cells was tracked with WES, and subclonal distribution of SETD2, STAG2, TSC2 and PBRM1 mutations was observed in different IT regions. Different regions of the same tumor were similar, whereas individual patient tumors were distinct according to tumor microenvironment cellular composition measured by CyTOF or deconvoluted from RNA-seq. The cellular deconvolution of the ccRCC tumors reconstructed from RNA-seq correlated with CyTOF, snRNA-seq and WGBS, showing high concordance among the methods. The promoter CpG island methylation levels, averaged across all genes, positively correlated with ccRCC grade. MxIF revealed spatial IT heterogeneity in the distribution of immune infiltrate components. Macrophages and T cells dispersed among malignant cells; whereas, T cells formed clusters at unique tumor margins. Conclusions: The utilization of multi-omics methods produced a high-resolution portrait of the ccRCC tumor composition and identified differential ITH among regions within the primary tumors or among individual primary tumors. This study demonstrated strong concordance among the different technologies, suggesting that tumor deconvolution by bulk RNA-seq might be clinically applicable for ccRCC tumors. MxIF analysis enabled a fine elucidation of the spatial relationships among the tumor and the immune and stromal cells, missed by common omic platforms. Integrated single cell multi-omics could render specific pathobiological and therapeutic insights that impact treatment decisions.

Methylation Status of MTHFR Promoter and Oligozoospermia Risk: An Epigenetic Study and in Silico Analysis.

Objective In this study, we evaluated the effects of promoter methylation of MTHFR on oligozoospermia risk, followed by an in silico analysis. Materials and Methods In a case-control study, semen samples were collected from infertile and healthy control men. MTHFR promoter region was amplified by methylation-specific polymerase chain reaction (PCR). Finally, the promoter region of MTHFR was analyzed by bioinformatics software. Results Our data revealed significant associations of CpG island promoter methylation with oligozoospermia in a case-control study. In silico analysis showed that promoter contains a strong nucleosome exclusion region, a bonafide CGIs, six PROSITE motifs without a defined TATA box and 14 transcription factor (TF) binding sites, which are directly involved in spermatogenesis ConclusionBased on our findings, methylation of the MTHFR gene promoter region may be a risk factor for oligozoospermia. However, this is a preliminary report representing data for future comprehensive studies to make a clinical conclusion on the potential biomarker role of methylation of this promoter in elevating susceptibility to oligozoospermia.

Epigenetic Inactivation of Protocadherin 10 by Methylation in Colorectal Cancer

Aberrant promoter methylation of CpG islands of tumor-suppressor genes has been recognized as one of the important tumor markers for cancer detection. The aim of this study was to investigate the promoter methylation status of protocadherin 10 (PCDH10), a tumor suppressor gene, in Iranian colorectal cancer (CRC) patients. Cancerous and the adjacent normal tissues obtained from 38 CRC patients were used to assess the methylation status of PCDH10 with Methylation Specific PCR, in addition, to study the expression level of this gene by quantitative PCR. The relationship between hypermethylation and the demographic characteristics of these patients was analyzed. The promoter methylation level of PCDH10 was statistically different between tumoral and normal tissues in CRC patients. Twenty-seven out of 38 patients showed hypermethylation with a sensitivity of 73% and a specificity of 97%. PCDH10 expression decreased in 15 cases (46%) as 16 cases (50 %) showed overexpression and 1 case (4%) had no changes. Not a significant association was reported between PCDH10 hypermethylation and the clinicopathological characteristics (P>0.05). Our results indicated that PCDH10 methylation has a critical function in CRC, with a nearly elevated sensitivity and a high specificity in the Iranian population, qualify it as a potential candidate biomarker. © 2019 Tehran University of Medical Sciences. All rights reserved. Acta Med Iran 2019;57(8):472-477.

Aberrant Methylation of Suppressor of Cytokine Signaling 1 (SOCS1) Gene as a Biomarker for Early Prediction and Diagnosis of Bladder Cancer.

SOCS1 protein, the negative regulatory protein of the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) signaling pathway, may inhibit signaling of JAK-STAT pathway by several cytokines and has tumor suppressor activity. Methylation of CpG island in the promoter region of SOCS1 gene has often been shown to inactivate the SOCS1 gene in certain human cancers. However, the precise role of SOCS1 in bladder cancer is unclear. Two hundred forty-seven patients with BCa and 243 healthy controls were enrolled from Tumour Hospital Affiliated to Harbin Medical University, Hongqi Hospital Affiliated to Mudanjiang Medical University, and Mudanjiang Tumour Hospital from September 2013 to March 2019. The methylation rate in the promoter region of the SOCS1 among all participants were detected using the MassARRAY EpiTYPER system. A ROC curve was set out to analyze SOCS1 gene promoter CpG island methylation for BCa diagnosis. There was a significantly higher methylation rate in BCa compared to controls. Then we assessed the methylation rate of different CpG islands in SOCS1 gene among BCa cases and normal controls. Methylation rate was shown to vary among different CpG islands. The methylation rates of CpG islands were shown to vary among different grades. We observed that the methylation rate of different CpG islands vary according to pathological grades. Our study demonstrates that aberrant methylation of CpG island in the promoter region of SOCS1 gene may be involved in occurrence, progression, and prognosis of BCa and, thus, may serve as an independent diagnosis and prognostic biomarker.

SOX17 expression and its down-regulation by promoter methylation in cervical adenocarcinoma in situ and adenocarcinoma.

AimsSOX17 expression has not been studied in glandular lesions of the uterine cervix like adenocarcinoma in situ (AIS) and invasive adenocarcinomas (AdC), whereas SOX17 promoter CpG island methylation has been reported. Therefore, the aim of this study was to relate the topographical distribution of SOX17 expression and SOX17 methylation status to each other, and to SOX2 expression, human papillomavirus (HPV) type, and physical status of the virus.Methods and resultsImmunohistochemistry was used in 45 cases to assess expression of SOX17 and SOX2. SOX17 promoter methylation was determined in 25 cases by means of bisulphite conversion and methylation‐specific polymerase chain reaction. SOX17 and SOX2 showed a mutually exclusive expression pattern in normal epithelium, with a sharp delineation in the squamocolumnar junction. SOX17 was found in endocervical columnar and reserve cells, whereas SOX2 was exclusively found in squamous epithelium. In both glandular lesions and cases with coexisting glandular and squamous intraepithelial components, a complex combination of SOX17 and SOX2 expression patterns was seen and mutually exclusive expression was lost. Frequently, gain of expression of SOX2 was found and expression of SOX17 was lost. Methylation of the CpG island in the SOX17 promoter was shown to be strongly associated with loss of expression of SOX17 (P = 0.0016).ConclusionsIn this study, we show for the first time a direct correlation between the topographical distribution of SOX17 expression and the methylation status of its gene promoter. This explains the heterogeneity of SOX17 expression in the glandular lesions of the cervix. No correlation was found between HPV type and physical status of the virus on the one hand and methylation status on the other.

Region-specific glucocorticoid receptor promoter methylation has both positive and negative prognostic value in patients with estrogen receptor-positive breast cancer

BackgroundThe glucocorticoid receptor (NR3C1, GR) is frequently downregulated in breast tumors, and evidence suggests it acts as a tumor suppressor in estrogen receptor-positive (ER+) breast cancer. We previously found that methylation of the GR promoter CpG island represses gene expression and occurs in ER+ breast tumors. In this study, the prognostic and predictive value of GR methylation was examined in ER+ patients from the CCTG MA.12 clinical trial of tamoxifen versus placebo in women with early breast cancer.MethodsWe developed a targeted multiplex bisulfite next-generation sequencing assay to detect methylation at multiple GR promoter regions in DNA from formalin-fixed paraffin-embedded (FFPE) samples. Following validation in a small cohort of breast tumors, ER+ FFPE tumor samples from MA.12 (n = 208) were tested. Survival analyses evaluated the impact of GR promoter methylation on patient overall survival (OS) and disease-free survival (DFS).ResultsAn analysis of TCGA data found that GR methylation is prevalent in ER+ tumors and is associated with decreased gene expression and analysis of public microarray data (KM Plotter) linked decreased GR expression to a poor outcome. In MA.12, two GR promoter regions (U and C) each had prognostic value, but with opposite effects on the outcome. U methylation was associated with poor OS (HR = 1.79, P = 0.041) whereas C methylation was associated with better OS (HR = 0.40, P = 0.040) and DFS (HR = 0.49, P = 0.037). The classification of patients based on the methylation status of the two regions was prognostic for OS (P = 0.006) and DFS (P = 0.041) and revealed a group of patients (U methylated, C unmethylated) with very poor outcomes. Placebo-treated patients in this high-risk group had worse OS (HR = 2.86, P = 0.002) and DFS (HR = 2.09, P = 0.014) compared to the rest of the cohort.ConclusionRegion-specific GR promoter methylation was an independent prognostic marker for patient survival and identified a subset of patients with poor prognosis, particularly without tamoxifen treatment. These findings provide a foundation for future studies into GR methylation as a promising prognostic biomarker in ER+ breast cancer.

The role of double-strand break repair, translesion synthesis, and interstrand crosslinks in colorectal cancer progression-clinicopathological data and survival.

DNA repair is a new and important pathway that explains colorectal carcinogenesis. This study will evaluate the prognostic value of molecular modulation of double-strand break repair (XRCC2 and XRCC5); DNA damage tolerance/translesion synthesis (POLH, POLK, and POLQ), and interstrand crosslink repair (DCLRE1A) in sporadic colorectal cancer (CRC). Tumor specimens and matched healthy mucosal tissues from 47 patients with CRC who underwent surgery were assessed for gene expression of XRCC2, XRCC5, POLH, POLK, POLQ, and DCLRE1A; protein expression of Polk, Ku80, p53, Ki67, and mismatch repair MLH1 and MSH2 components; CpG island promoter methylation of XRCC5, POLH, POLK, POLQ, and DCLRE1A was performed. Neoplastic tissues exhibited induction of POLK (P < .001) and DCLRE1A (P < .001) expression and low expression of POLH (P < .001) and POLQ (P < .001) in comparison to healthy paired mucosa. Low expression of POLH was associated with mucinous histology and T1-T2 tumors (P = .038); low tumor expression of POLK was associated with distant metastases (P = .042). CRC harboring POLK promoter methylation exhibited better disease-free survival (DFS) (P = .005). This study demonstrated that low expression or unmethylated POLH and POLK were related to worse biological behavior tumors. However, POLK methylation was associated with better DFS. POLK and POLH are potential prognostic biomarkers in CRC.

Low level CpG island promoter methylation predicts a poor outcome in adult T-cell acute lymphoblastic leukemia.

Cancer cells undergo massive alterations in their DNA methylation patterns which result in aberrant gene expression and malignant phenotypes. Abnormal DNA methylation is a prognostic marker in several malignancies, but its potential prognostic significance in adult T-cell acute lymphoblastic leukemia (T-ALL) is poorly defined. Here, we performed methylated DNA immunoprecipitation to obtain a comprehensive genome-wide analysis of promoter methylation in adult T-ALL (n=24) compared to normal thymi (n=3). We identified a CpG hypermethylator phenotype that distinguishes two T-ALL subgroups and further validated it in an independent series of 17 T-lymphoblastic lymphoma. Next, we identified a methylation classifier based on nine promoters which accurately predict the methylation phenotype. This classifier was applied to an independent series of 168 primary adult T-ALL treated accordingly to the GRAALL03/05 trial using methylation-specific multiplex ligation-dependent probe amplification. Importantly hypomethylation correlated with specific oncogenic subtypes of T-ALL and identified patients associated with a poor clinical outcome. This methylation-specific multiplex ligation-dependent probe amplification based methylation profiling could be useful for therapeutic stratification of adult T-ALL in routine practice. The GRAALL-2003 and -2005 studies were registered at http://www.clinicaltrials.gov as #NCT00222027 and #NCT00327678, respectively.

Prostate Stem Cell Antigen Gene Polymorphism Is Associated with H. pylori-related Promoter DNA Methylation in Nonneoplastic Gastric Epithelium.

Genome-wide association study identified two functional SNPs associated with gastric cancer especially the diffuse type. The first was a polymorphism (rs2294008) in prostate stem cell antigen (PSCA), and the other was a polymorphism (rs4072037) in mucin 1 (MUC1). DNA methylation is associated with gastric cancer and Helicobacter pylori (H. pylori)-induced gastritis, while hypermethylation of promoter CpG island (CGI) is a common characteristic of enlarged-fold gastritis induced by H. pylori, a risk factor of diffuse-type gastric cancer. We evaluated the association between PSCA and MUC1 polymorphisms with H. pylori--related promoter CGI methylation in the nonneoplastic gastric mucosa. PSCA rs2294008 C/T and MUC1 rs4072037 A/G polymorphisms were genotyped in 410 cancer-free subjects in relation to promoter CGI methylation status of three candidate genes, of which the methylation status is associated with H. pylori infection (IGF2, MYOD1, and SLC16A12). Methylation levels of all three genes were significantly higher in subjects with PSCA rs2294008 T/T compared with the PSCA rs2294008 C/C (all P < 0.05). Such associations were more enhanced in H. pylori-positive subjects (all P < 0.01). The multivariate analysis demonstrated that PSCA C/T [OR, 2.37; 95% CI (confidence interval), 1.06-5.29; P = 0.035] and T/T genotypes (OR, 3.2; 95% CI, 1.41-7.25; P = 0.005) were significantly associated with methylation-high gastric mucosa as independent factors. MUC1 rs4072037 A/G polymorphism was not associated with methylation status of all three genes. PSCA C/T and T/T genotypes are associated with H. pylori-related promoter DNA methylation in the gastric mucosa.Impact: Our observations provided the evidence that PSCA polymorphism influence the susceptibility to gastric cancer through DNA methylation induction.

Methylation of RB1 CpG island by SUV39H1/DNMT3A promotes malignant melanoma development

Melanoma is among the most aggressive and treatment‐resistant human cancers. Aberrant histone H3 methylation at Lys 9 (H3K9) correlates with carcinogenic gene silencing but the significance of suppressor of variegation 3–9 homolog 1 (SUV39H1), a H3K9‐specific methyltransferase, in melanoma initiation and progression remains unclear. Here we show that SUV39H1‐mediated H3K9 trimethylation (H3K9me3) facilitates retinoblastoma (RB1) promoter CpG island methylation by interacting with DNMT3A and decreasing RB mRNA and protein in melanoma cells. Reduced RB abundance, in turn, impairs E2F1 transcriptional inhibition leading to increased peptidyl‐prolyl cis‐trans isomerase NIMA interacting 1 (PIN1) levels, human keratinocyte neoplastic cell transformation, and melanoma tumorigenesis via enhanced RAF1/MEKs/ERKs signaling pathway activation. In a synergistic model with B16‐F1 murine melanoma cells, SUV39H1 and PIN1 overexpression increased melanoma growth, which was abrogated by their inhibition in SUV39H1‐overexpressing B16‐F1 mice. SUV39H1 also positively correlated with PIN1 expression in human melanoma. Our studies establish SUV39H1 as an oncogene in melanoma and underscore the role of chromatin factors in regulating tumorigenesis.Support or Funding InformationThis research was supported by a grant of the Korea Health Technology R&amp;D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health &amp; Welfare, Republic of Korea (grant number : HI18C1083).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Expression and regulation of GnRHR2 gene and testosterone secretion mediated by GnRH2 and GnRHR2 within porcine testes

Gonadotropin-releasing hormone 2 receptor (GnRHR2) together with its cognate ligand involves in regulating reproductive behavior. However, little is known concerning the effect of transcription factor steroidogenic factor1 (SF-1) regulation on porcine GnRHR2 gene expression and GnRH2 regulation mechanism in testosterone secretion through GnRHR2. Our study demonstrated that GnRHR2 transcription levels were high in porcine testis. Immunohistochemistry analyses showed that GnRHR2 immunoreactivity was strong in the Leydig cells in boar testes. Two SF-1 binding sites were predicted in GnRHR2 promoter and the second site (-159/-149) was considered to be important for GnRHR2 promoter activity through site-directed mutagenesis. The binding of SF-1 to GnRHR2 promoter was confirmed by electrophoretic mobility shift assays (EMSA) and chromatin immunoprecipitation (ChIP). Overexpression and knockdown experiments revealed that SF-1 could up-regulate porcine GnRHR2 expression. DNA methylation of GnRHR2 promoter CpG island also specifically regulated GnRHR2 expression. Meanwhile, our study also demonstrated GnRH2 treatment promoted the expression of SF-1 and steroidogenic acute regulatory protein (StAR), and that this treatment stimulated cAMP responsive element binding protein (CREB) phosphorylation, regulated the expression of GnRHR2, especially that of GnRHR2-X1, and promoted testosterone secretion in porcine Leydig cells. We speculated that testosterone secretion mediated by GnRH2 and GnRHR2 (mainly GnRHR2-X1) was regulated by phosphorylated CREB interacting with SF-1 to control StAR expression. Taken together, the present study indicates that SF-1 and GnRH2 are the essential regulatory factors for GnRHR2 expression. This study also explores the regulation mechanism of testosterone secretion mediated by GnRH2 and GnRHR2 in porcine Leydig cells.

Aberrant hypermethylation of OGDHL gene promoter in sporadic colorectal cancer

BackgroundAberrant methylation patterns of certain genes including tumor suppressors, a major epigenetic event, contribute mainly to tumorigenesis. Promoter CpG island methylation in Oxoglutarate dehydrogenase like (OGDHL) gene has been reported to reduce gene expression and hence apoptosis induction. This gene has been shown to be involved in colorectal cancer progression. In the present study, we investigated methylation status of OGDHL gene promoter in patients with colorectal cancer and evaluated its potential as a diagnostic biomarker. Methods and materialAfter collecting clinicopathologic data of patients, tumor and matched tumor free margin samples were obtained from 40 individuals; total genomic DNA was extracted and subjected to bisulfite modification. Methylation status of the gene promoter was studied using quantitative methylation-specific PCR method. Finally, its potential as a diagnostic biomarker was evaluated by receiver operating characteristic curve analysis. ResultsThere was not any significant correlation for clinicopathologic features including tumor stage, grade, size, and location with methylation status of OGDHL promoter. However, a significant high methylation level was observed in tumoral tissues compared with nontumoral marginal samples (P < 0.0001). Moreover, receiver operating characteristic curve analysis revealed 97.5% sensitivity and 95%, specificity for OGDHL promoter methylation in a cut off of 27.37% methylation as a biomarker for colorectal cancer. ConclusionThe promoter of OGDHL gene is hypermethylated in colorectal cancer and might be considered as a biomarker for its development.

Differential regulation of CpG island methylation within divergent and unidirectional promoters in colorectal cancer.

The silencing of tumor suppressor genes by promoter CpG island (CGI) methylation is an important cause of oncogenesis. Silencing of MLH1 and BRCA1, two examples of oncogenic events, results from promoter CGI methylation. Interestingly, both MLH1 and BRCA1 have a divergent promoter, from which another gene on the opposite strand is also transcribed. Although studies have shown that divergent transcription is an important factor in transcriptional regulation, little is known about its implication in aberrant promoter methylation in cancer. In this study, we analyzed the methylation status of CGI in divergent promoters using a recently enriched transcriptome database. We measured the extent of CGI methylation in 119 colorectal cancer (CRC) clinical samples (65 microsatellite instability high [MSI‐H] CRC with CGI methylator phenotype, 28 MSI‐H CRC without CGI methylator phenotype and 26 microsatellite stable CRC) and 21 normal colorectal tissues using Infinium MethylationEPIC BeadChip. We found that CGI within divergent promoters are less frequently methylated than CGI within unidirectional promoters in normal cells. In the genome of CRC cells, CGI within unidirectional promoters are more vulnerable to aberrant methylation than CGI within divergent promoters. In addition, we identified three DNA sequence motifs that correlate with methylated CGI. We also showed that methylated CGI are associated with genes whose expression is low in normal cells. Thus, we here provide fundamental observations regarding the methylation of divergent promoters that are essential for the understanding of carcinogenesis and development of cancer prevention strategies.

Screening Relevance of Sessile Serrated Polyps.

Conventional adenomas have historically been considered to be the only screening-relevant colorectal cancer (CRC) precursor lesion. The prevailing paradigm was that most CRCs arise along the chromosomal instability pathway, where adenomas accumulate incremental genetic alterations over time, leading eventually to malignancy. However, it is now recognized that this “conventional” pathway accounts for only about two-thirds of CRCs. The serrated pathway is responsible for most of the remainder, and is a disproportionate contributor to postcolonoscopy CRC. Hallmarks of the serrated pathway are mutations in the BRAF gene, high levels of methylation of promoter CpG islands, and the sessile serrated polyp (SSP). Accumulating evidence shows that SSPs can be considered adenoma-equivalent from the standpoint of CRC screening. SSPs have a higher prevalence than previously thought, and appear to have a relatively long dwell time similar to that of conventional adenomas. In addition, SSPs, whether sporadic or as part of the serrated polyposis syndrome, are associated with increased risk of synchronous and metachronous neoplasia. These features collectively support that SSPs are highly relevant to CRC prevention.