Regulation of the H19 imprinting gene expression in human nasopharyngeal carcinoma by methylation.
In East Asia and Singapore, the human nasopharyngeal carcinoma (NPC) presented clinically is mainly of the undifferentiated type. In contrast, the well-differentiated squamous NPC is more commonly detected in the West. To study the potential differences in carcinogenesis between undifferentiated and differentiated human NPC, we employed cDNA microarrays to isolate genes that might be specific for human undifferentiated NPC. One of the genes identified to be specifically upregulated in the undifferentiated human NPC cell line CNE-2 is the human imprinting gene H19. Interestingly, H19 is not expressed in the well-differentiated human HK1 NPC cells. Northern blot and in situ hybridization analyses also confirmed that the H19 gene is strongly expressed in the undifferentiated CNE-2 human NPC cell line but not in the well-differentiated HK1 human NPC cell line. In situ hybridization and reverse transcriptase-polymerase chain reaction also demonstrated that H19 is specifically expressed in NPC biopsies and not in non-NPC human tissue biopsies. Furthermore, we demonstrated that deregulation of H19 gene expression in the well-differentiated human HK1 NPC cells could be induced by the hypomethylation of CpG sites of the H19 promoter region. Hypermethylation of gene promoter regions might therefore be an important epigenetic event that plays a role in the differentiation of human NPC cells and the transcriptional silencing of imprinted genes.
Ng
Aylwin
A
Laboratory of Gene Structure and Expression, Division of Cellular and Molecular Research, National Cancer Centre, Singapore.
Tang
Jing P
JP
Goh
Christopher H K
CH
Hui
Kam M
KM
D001483:Base Sequence; D002454:Cell Differentiation; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D018392:Genomic Imprinting; D006801:Humans; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009303:Nasopharyngeal Neoplasms / Q000235:genetics* / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic / Q000235:genetics; D062085:RNA, Long Noncoding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
C094335:H19 long non-coding RNA; D062085:RNA, Long Noncoding; D012333:RNA, Messenger; D022661:RNA, Untranslated