Hypermethylation of the promoter region is associated with the loss of MEG3 gene expression in human pituitary tumors.

MEG3 is a human homolog of the mouse maternal imprinted gene, Gtl2. Gtl2 has been suggested to be involved in fetal and postnatal development and to function as an RNA. Recently our laboratory demonstrated that a cDNA isoform of MEG3, MEG3a, inhibits cell growth in vitro. Interestingly, MEG3 is highly expressed in the normal human pituitary. In striking contrast, no MEG3 expression was detected in human clinically nonfunctioning pituitary tumors. These data indicate that this imprinted gene may be involved in pituitary tumorigenesis. In the present study we investigated the mechanism underlying the absence of MEG3 expression in human clinically nonfunctioning pituitary tumors. No genomic abnormality was detected in the tumors examined. Instead, we found that two 5'-flanking regions, immediately in front of and approximately 1.6-2.1 kb upstream of the first exon, respectively, were hypermethylated in tumors without MEG3 expression compared with the normal pituitary. Reporter assays demonstrated that these two regions are functionally important in gene expression activation. Furthermore, treatment of human cancer cell lines with a methylation inhibitor resulted in MEG3 expression. We conclude that hypermethylation of the MEG3 regulatory region is an important mechanism associated with the loss of MEG3 expression in clinically nonfunctioning pituitary tumors.

[1]  K. Kovacs,et al.  Clonal origin of pituitary adenomas. , 1990, The Journal of clinical endocrinology and metabolism.

[2]  A. Arnold,et al.  Clinically nonfunctioning pituitary tumors are monoclonal in origin. , 1990, The Journal of clinical investigation.

[3]  A. Klibanski,et al.  Somatostatin receptor subtype gene expression in pituitary adenomas. , 1995, The Journal of clinical endocrinology and metabolism.

[4]  V. Gouyer,et al.  Expression of c-ets-1, collagenase 1, and urokinase-type plasminogen activator genes in lung carcinomas. , 1995, The American journal of pathology.

[5]  P. Sassone-Corsi,et al.  Cyclic AMP signalling and cellular proliferation: regulation of CREB and CREM , 1997, FEBS letters.

[6]  T. Houseal,et al.  Frequent loss of chromosome 14 in atypical and malignant meningioma: identification of a putative `tumor progression' locus , 1997, Oncogene.

[7]  R. Fahlbusch,et al.  Comparative genomic hybridization analysis of nonfunctioning pituitary tumors. , 1998, The Journal of clinical endocrinology and metabolism.

[8]  A. Mutirangura,et al.  Loss of heterozygosity on chromosome 14 in nasopharyngeal carcinoma , 1998, International journal of cancer.

[9]  A. Ferguson-Smith,et al.  The mouse Gtl2 gene is differentially expressed during embryonic development, encodes multiple alternatively spliced transcripts, and may act as an RNA , 1998, Developmental dynamics : an official publication of the American Association of Anatomists.

[10]  D. Danila,et al.  The Journal of Clinical Endocrinology & Metabolism Printed in U.S.A. Copyright © 1999 by The Endocrine Society Expression of Prolactin-Releasing Peptide and Its Receptor Messenger Ribonucleic Acid in Normal Human Pituitary and Pituitary Adenomas* , 2022 .

[11]  A. Valentini,et al.  Structure, expression, and function of human pituitary tumor-transforming gene (PTTG). , 1999, Molecular endocrinology.

[12]  M. Isobe,et al.  Loss of heterozygosity of 14q32 in colorectal carcinoma. , 1999, Cancer genetics and cytogenetics.

[13]  T. Okamura,et al.  Cytogenetic alterations in pituitary adenomas detected by comparative genomic hybridization. , 1999, Cancer genetics and cytogenetics.

[14]  R. Buettner,et al.  Regulatory roles of AP-2 transcription factors in vertebrate development, apoptosis and cell-cycle control. , 2000, Gene.

[15]  S. Murphy,et al.  Novel imprinted DLK1/GTL2 domain on human chromosome 14 contains motifs that mimic those implicated in IGF2/H19 regulation. , 2000, Genome research.

[16]  N. Aarskog,et al.  Real-time quantitative polymerase chain reaction , 2000, Human Genetics.

[17]  Á. Carracedo,et al.  Rapid real-time fluorescent PCR gene dosage test for the diagnosis of DNA duplications and deletions. , 2000, Clinical chemistry.

[18]  S. Wakana,et al.  Identification of an imprinted gene, Meg3/Gtl2 and its human homologue MEG3, first mapped on mouse distal chromosome 12 and human chromosome 14q , 2000, Genes to cells : devoted to molecular & cellular mechanisms.

[19]  K. Ohshima,et al.  Cytogenetic analysis and clinical significance in adult T-cell leukemia/lymphoma: a study of 50 cases from the human T-cell leukemia virus type-1 endemic area, Nagasaki. , 2001, Blood.

[20]  Peter A. Jones,et al.  The fundamental role of epigenetic events in cancer , 2002, Nature Reviews Genetics.

[21]  S. Asa,et al.  The pathogenesis of pituitary tumours , 2002, Nature Reviews Cancer.

[22]  Gillian E. Wu,et al.  Targeted expression of a human pituitary tumor-derived isoform of FGF receptor-4 recapitulates pituitary tumorigenesis. , 2002, The Journal of clinical investigation.

[23]  L. Shaffer,et al.  Epigenetic detection of human chromosome 14 uniparental disomy , 2003, Human mutation.

[24]  M. Minden,et al.  Quantitative PCR identifies a minimal deleted region of 120 kb extending from the Philadelphia chromosome ABL translocation breakpoint in chronic myeloid leukemia with poor outcome , 2003, Leukemia.

[25]  T. Kalebic.  Epigenetic Changes: Potential Therapeutic Targets , 2003, Annals of the New York Academy of Sciences.

[26]  W. Farrell,et al.  Epigenetic change in pituitary tumorigenesis. , 2003, Endocrine-related cancer.

[27]  Valerie Combaret,et al.  Real-time PCR based on SYBR-Green I fluorescence: An alternative to the TaqMan assay for a relative quantification of gene rearrangements, gene amplifications and micro gene deletions , 2003, BMC biotechnology.

[28]  C. Gélinas,et al.  To be, or not to be: NF-κB is the answer – role of Rel/NF-κB in the regulation of apoptosis , 2003, Oncogene.

[29]  D. Danila,et al.  A pituitary-derived MEG3 isoform functions as a growth suppressor in tumor cells. , 2003, The Journal of clinical endocrinology and metabolism.

[30]  Yunli Zhou,et al.  DNA Damage-induced Inhibition of Securin Expression Is Mediated by p53* , 2003, The Journal of Biological Chemistry.

[31]  M. Korbonits,et al.  Role of regulatory factors in pituitary tumour formation. , 2004, Frontiers of hormone research.

[32]  W. Farrell,et al.  Loss of expression of the growth inhibitory gene GADD45γ, in human pituitary adenomas, is associated with CpG island methylation , 2004, Oncogene.