title: Promoter methylation and differential expression of pi-class glutathione S-transferase in endometrial carcinoma.
abstract: Pi-class glutathione S-transferase (GSTP1), located on chromosome 11q13, codes for a phase II metabolic enzyme that detoxifies reactive electrophilic intermediates. The protein also interacts with steroid hormones in the human body. The role of GSTP1 in endometrial carcinoma has not been reported. In this study, we aimed at determining the expression of GSTP1 in relation to the epigenetic and genetic changes of the gene in endometrial carcinoma. The GSTP1 protein and mRNA expression was assessed by immunohistochemistry on tissue microarray and quantitative real-time reverse transcriptase-polymerase chain reaction, respectively. Its methylation status was studied by methylation-specific polymerase chain reaction and bisulfite sequencing. Possible mutations in coding region of GSTP1 were assessed by cDNA sequencing. Ninety-seven cases of endometrial carcinoma with available tissue blocks and clinical data were studied. Our results showed that 68.0% (66 of 97) of the cases showed reduced protein expression while 64% (16 of 25) showed reduced mRNA expression; 30.9% (30 of 97) of the cases demonstrated methylated alleles in at least one of the six methylation-specific polymerase chain reaction reactions. The methylation status significantly correlated with reduced protein expression (P = 0.008) and reduced mRNA expression (P = 0.003). Methylation at non-CpG sites including CpCpG trinucleotides and CpT dinucleotides were also observed. cDNA sequencing did not reveal genetic alterations in coding region of the gene. The extent of myometrial invasion was found to be significantly correlated with both the methylation status (P = 0.009) and the protein expression (P = 0.036) of the GSTP1 gene. We postulated that hypermethylation of the GSTP1 gene promoter region may act as a dynamic regulation mechanism contributing to reduced GSTP1 expression, which is associated with myometrial invasion potential of the endometrial carcinoma.
authors.affiliation: Department of Pathology, Queen Mary Hospital, The University of Hong Kong, Pokfulam Rd., Hong Kong.
authors.forename: Queeny K Y
authors.initials: QK
authors.lastname: Chan
authors.forename: Ui-Soon
authors.initials: US
authors.lastname: Khoo
authors.forename: Kelvin Y K
authors.initials: KY
authors.lastname: Chan
authors.forename: Hextan Y S
authors.initials: HY
authors.lastname: Ngan
authors.forename: Shan-Shan
authors.initials: SS
authors.lastname: Li
authors.forename: Pui-Man
authors.initials: PM
authors.lastname: Chiu
authors.forename: Li-Shan
authors.initials: LS
authors.lastname: Man
authors.forename: Philip P C
authors.initials: PP
authors.lastname: Ip
authors.forename: Wei-Cheng
authors.initials: WC
authors.lastname: Xue
authors.forename: Annie N Y
authors.initials: AN
authors.lastname: Cheung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001483:Base Sequence; D018269:Carcinoma, Endometrioid / Q000201:enzymology* / Q000235:genetics; D018899:CpG Islands / Q000235:genetics; D019175:DNA Methylation; D016889:Endometrial Neoplasms / Q000201:enzymology* / Q000235:genetics; D004717:Endometrium / Q000276:immunology / Q000473:pathology; D005260:Female; D015870:Gene Expression; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D012333:RNA, Messenger; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D005982:Glutathione Transferase