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Genome-wide DNA methylation analysis on testicular embryonal carcinoma

ABSTRACT: Genomic DNA from 6 pure EC and 2 normal testis was fragmented and immunoprecipitated with anti-5mC monoclonal antibodies by MeDIP. After IP, DNA was purified and amplified using Whole Genome Amplification. Subsequently, DNA was biotin-labeled and hybridized to Human Tiling Array 2.0R Chips (Affymetrix) according to the manufacturer’s instruction. Raw data (CEL files) were normalized and analyzed by TAS (Affymetrix). Technical replicate of MeDIP-chip procedure was performed. Testicular embryonic carcinoma (EC) is a major subtype of non-seminomatous germ cell tumors (NSGCTs) in males. To identify epigenetic changes during testicular tumorigenesis, we profiled the DNA methylation of 6 ECs. These samples represent different stages (stage I and stage III) and different extent of invasiveness. Non-cancerous testicular tissues were included. A total of 1167 tumor-hypermethylated differential methylated regions (DMRs) were identified across the genome. Among them, 40 genes/ncRNA were found to have hypermethylated promoters. Interestingly, we found several hypermethylated sex-linked genes, including X-linked genes STAG2, SPANXD/E, MIR1184, Y-linked genes RBMY1A1/1B/1D and FAM197Y2P. Expression of RBMY1A was confirmed by immunohistochemistry in normal germ cells, but lost in EC and seminoma. Our genome-wide analysis identified methylation changes in several previously unknown genes for testicular ECs, which might provide insight into the crosstalk between normal germ cell development and carcinogenesis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE66784 | GEO | 2015/03/12

SECONDARY ACCESSION(S): PRJNA277952

REPOSITORIES: GEO

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Project description:Malignant (type II) testicular germ cell tumors (TGCT) are considered tumors of embryonic germ cell ancestry that diverge morphologically as seminoma (SE), and nonseminomas (NS), the latter including embryonal carcinoma (EC), teratoma (TE), yolk sac tumor (YS) and choriocarcinoma. We have analyzed the genomes and epigenomes of pure histological forms of TGCT (n=130) and 128 matched adjacent normal testicular tissues for TGCT core and subtype-specific DNA methylome profiles and somatic copy number aberrations (SCNA). Original data were compared with published data sets focused on differentiated and pluripotent states. First, we identified pan-TGCT recurrent erasure of maternal and paternal germline imprints and DPPA3 (STELLA), consistent with an embryonic germ cell ancestry. Beyond these conserved properties, we identified TGCT subtype-dependent epigenomic congruency with pluripotent versus somatic reference lineages, thereby establishing competency for lineage-conforming methylation reprogramming in the multi-potent common ancestor of TGCT. Notable subtype programming distinctions are as follows: the SE methylome reflects a ground-state of germ cell erasure; EC is found to harbor pervasive embryonic stem cell (ESC)-like CpH (non-CpG) methylation, absent in other TGCT and non-germ cell tumors and differentiated tissues. EC was further distinguished by ESC-like hypomethylation of NANOG, contrasting with NANOG methylation in TE, YS, and somatic tissues. Thus, EC methylomes present a novel mixed ESC/embryonic germ cell epigenomic state. TE global methylation was most convergent with somatic tissue; however, and unique among TGCT subtypes, TE manifested hypermethylation of the H19 paternal germline DMR. The YS methylome most closely resembled extra-embryonic trophoblast. The total set of findings provides evidence for a multi-potent TGCT stem cell whose progeny may harbor pluripotent, primordial germ/gonocyte, and somatic lineage-defining methylation marks. Despite such competency, no TGCT subtype restored erased parental germline imprints. TE is the exception, with H19 hypermethylation. Benign testis adjacent to TGCT exhibited a bimodal epigenotype distribution determined by spermatogenesis and significantly associated with high versus low Johnsen score. Overall, TGCT methylomes are trapped in a core embryonic germ cell-like state of DPPA3/STELLA and imprint erasure, while differential somatic and pluripotent reprogramming profiles are otherwise established.

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Genome-wide DNA methylation analysis on testicular embryonal carcinoma

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