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Genome-Wide Screen of Promoter Methylation Identifies Novel Markers for Tumor Development in Melanoma

ABSTRACT: Background: DNA methylation is an important component of epigenetic modifications that influences the transcriptional machinery and is aberrant in many human diseases. In particular, dysregulation of promoter methylation in cancer has already been shown to be associated with repression of tumor suppressors and activation of oncogenes. In addition, detection of altered promoter methylation status is suitable for the design of diagnostic or prognostic tests. In this study we present a new methodological approach for the robust identification of promoter methylation markers and the first genome-wide study for the detection of methylation markers in melanoma. Methods and Findings: Genome-wide promoter methylation and gene expression of ten early passage melanoma cell strains are compared to newborn and adult normal melanocytes. For the identification of markers we applied linear mixed effect models (LME) in combination with a series of filters based on the localization of promoter methylation relative to the transcription start site, overall promoter CpG content, and differential gene expression. The aim of this methodology is to identify markers whose promoter differential methylation is likely to be functionally related to differential expression. We identified 76 markers, 68 hyper- and 8-hypo-methylated in melanomas (LME P<0.05). Promoter methylation profiles and differential expression of five of these markers were successfully validated. In addition, promoter demethylation following Aza treatment consistently restored expression of markers hyper-methylated in melanoma. Conclusions: The proposed methodology allows the identification of robust markers and can be applied to other experimental scenarios where promoter methylation is evaluated. More importantly, the list of markers represents the first systematic effort in the identification of methylation markers in melanoma. Many of the identified markers were not previously known to be regulated by promoter methylation and/or associated with this or other types of cancer.

ORGANISM(S): Homo sapiens

PROVIDER: GSE13706 | GEO | 2009/05/26

SECONDARY ACCESSION(S): PRJNA109437

REPOSITORIES: GEO

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Project description:Abstract; Background: Promoter hypermethylation coupled with loss of heterozygosity at the same locus results in loss of gene function in many tumor cells. The ârulesâ governing which genes are methylated during the pathogenesis of individual cancers, how specific methylation profiles are initially established, or what determines tumor-type specific methylation are unknown. However, DNA methylation markers that are highly specific and sensitive for common tumors would be useful for the early detection of cancer, and those required for the malignant phenotype identify pathways important as therapeutic targets. Methods and Findings: In an effort to identify new cancer-specific methylation markers, we employed a high throughput global expression profiling approach in lung cancer cells. We identified 132 genes that have 5â CpG islands, are induced from undetectable levels by 5-aza-2â-deoxycytidine (5-aza) in multiple non-small cell lung cancer cell lines, and are expressed in immortalized human bronchial epithelial cells. As expected, these genes were also expressed in normal lung, but often not in companion primary lung cancers. Methylation analysis of a subset (45/132) of these promoter regions in primary lung cancer (N=20) and adjacent non-malignant tissue showed that 31 genes had acquired methylation in the tumors, but did not show methylation in normal lung or lymphocytes. We studied the eight most frequently and specifically methylated genes from our lung cancer data set in breast cancer (N=37), colon cancer (N=24), and prostate cancer (N=24) along with counterpart non-malignant tissues. We found that seven loci were frequently methylated in both breast and lung cancers, with four showing extensive methylation in all four epithelial tumors. Conclusions: By using a systematic biological screen we identified multiple genes that are methylated with high penetrance in primary lung, breast, colon, and prostate cancers. The cross-tumor methylation pattern we observed for these novel markers suggests that we have identified a partial promoter hypermethylation signature for these common malignancies. These data suggest that while tumors in different tissues vary substantially with respect to gene expression, there may be commonalities in their promoter methylation profiles that represent potential targets for early detection screening or therapeutic intervention. Experiment Overall Design: Drug treatment: control, 100 nM, 1 uM Experiment Overall Design: Cancer vs. Normal Comparison: NSCLC vs. Normal

Project description:BACKGROUND: Promoter hypermethylation coupled with loss of heterozygosity at the same locus results in loss of gene function in many tumor cells. The "rules" governing which genes are methylated during the pathogenesis of individual cancers, how specific methylation profiles are initially established, or what determines tumor type-specific methylation are unknown. However, DNA methylation markers that are highly specific and sensitive for common tumors would be useful for the early detection of cancer, and those required for the malignant phenotype would identify pathways important as therapeutic targets. METHODS AND FINDINGS: In an effort to identify new cancer-specific methylation markers, we employed a high-throughput global expression profiling approach in lung cancer cells. We identified 132 genes that have 5' CpG islands, are induced from undetectable levels by 5-aza-2'-deoxycytidine in multiple non-small cell lung cancer cell lines, and are expressed in immortalized human bronchial epithelial cells. As expected, these genes were also expressed in normal lung, but often not in companion primary lung cancers. Methylation analysis of a subset (45/132) of these promoter regions in primary lung cancer (n = 20) and adjacent nonmalignant tissue (n = 20) showed that 31 genes had acquired methylation in the tumors, but did not show methylation in normal lung or peripheral blood cells. We studied the eight most frequently and specifically methylated genes from our lung cancer dataset in breast cancer (n = 37), colon cancer (n = 24), and prostate cancer (n = 24) along with counterpart nonmalignant tissues. We found that seven loci were frequently methylated in both breast and lung cancers, with four showing extensive methylation in all four epithelial tumors. CONCLUSIONS: By using a systematic biological screen we identified multiple genes that are methylated with high penetrance in primary lung, breast, colon, and prostate cancers. The cross-tumor methylation pattern we observed for these novel markers suggests that we have identified a partial promoter hypermethylation signature for these common malignancies. These data suggest that while tumors in different tissues vary substantially with respect to gene expression, there may be commonalities in their promoter methylation profiles that represent targets for early detection screening or therapeutic intervention. Experiment Overall Design: We compared the gene expression changes HBEC and NSCLC cells before and after treatment with 5-aza-2'deoxycytidine.

Project description:Epigenetic modifications, such as aberrant DNA promoter methylation is frequently observed in cervical cancer. Identification of hypermethylated regions maybe useful for discrimination between normal cervical epithelium and high-grade cervical intraepithelial neoplasia (CIN2/3) or worse may improve current cervical cancer population-based screening programs. In this study, the DNA methylome of high-grade CIN lesions were characterised using genome-wide methylation screening to identify potential biomarkers for early diagnosis of cervical neoplasia. Methyl-DNA Immunoprecipitation (MeDIP) combined with DNA microarray was used to compare DNA methylation profiles of epithelial cells derived from high-grade CIN lesions with normal cervical epithelium resulting in the identification of hypermethylated differentially methylated regions (DMRs). Validation of 9 selected DMRs by MSP or BSP in cervical tissue revealed methylation in 63.2-94.7% high-grade CIN and in 59.3-100% cervical carcinomas. QMSP for the two most significant high-grade CIN-specific methylation markers was applied exploring test performance in a large series of cervical scrapings. Frequency and relative level of methylation were significantly different between normal and cancer samples (p<0.001). Clinical validation of both markers in cervical scrapings from patients referred with an abnormal cervical smear, confirmed that frequency and relative level of methylation were related with increasing severity of the underlying CIN lesion (p<0.001) and the ROC analysis was discriminative (p<0.005). These possible methylation markers represent COL25A1 and KATNAL2 promoters and their observed increased methylation upon progression is in agreement with their biological function (cytoskeleton regulation). In conclusion, our newly identified hypermethylated DMRs represent specific DNA methylation patterns in high-grade CIN lesions and could be potential biomarkers for early detection. Epigenetic modifications, such as aberrant DNA promoter methylation is frequently observed in cervical cancer. Identification of hypermethylated regions maybe useful for discrimination between normal cervical epithelium and high-grade cervical intraepithelial neoplasia (CIN2/3) or worse may improve current cervical cancer population-based screening programs. In this study, the DNA methylome of high-grade CIN lesions were characterised using genome-wide methylation screening to identify potential biomarkers for early diagnosis of cervical neoplasia. Methyl-DNA Immunoprecipitation (MeDIP) combined with DNA microarray was used to compare DNA methylation profiles of epithelial cells derived from high-grade CIN lesions with normal cervical epithelium resulting in the identification of hypermethylated differentially methylated regions (DMRs). Validation of 9 selected DMRs by MSP or BSP in cervical tissue revealed methylation in 63.2-94.7% high-grade CIN and in 59.3-100% cervical carcinomas. QMSP for the two most significant high-grade CIN-specific methylation markers was applied exploring test performance in a large series of cervical scrapings. Frequency and relative level of methylation were significantly different between normal and cancer samples (p<0.001). Clinical validation of both markers in cervical scrapings from patients referred with an abnormal cervical smear, confirmed that frequency and relative level of methylation were related with increasing severity of the underlying CIN lesion (p<0.001) and the ROC analysis was discriminative (p<0.005). These possible methylation markers represent COL25A1 and KATNAL2 promoters and their observed increased methylation upon progression is in agreement with their biological function (cytoskeleton regulation). In conclusion, our newly identified hypermethylated DMRs represent specific DNA methylation patterns in high-grade CIN lesions and could be potential biomarkers for early detection. MeDIP with subsequent microarray analysis was performed on DNA isolated from frozen macrodissected epithelial tissue of CIN3 lesions (n=15) and normal cervices (n=10).

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Genome-Wide Screen of Promoter Methylation Identifies Novel Markers for Tumor Development in Melanoma

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