title: Expression ofPTENand its pseudogenePTENP1, and promoter methylation ofPTENin non-tumourous thymus and thymic tumours.
abstract: OBJECTIVE
  Mutation or promoter methylation of the phosphatase tensin homologue deleted on chromosome 10 tumour suppressor gene (PTEN) promotes some cancers. Moreover,PTENP1(PTENpseudogene) transcript regulates PTEN expression and is thought to be associated with tumourigenesis in some cancers. Here, we investigated PTEN expression in thymic epithelium and thymic epithelial tumours.
  
  
  METHODS
  Immunohistochemical analysis of PTEN was performed on two non-tumourous thymus (NT) samples, 33 thymomas (three type A, eight type AB, 11 type B1, six type B2, and five type B3), and four thymic carcinomas (TCs). In 16 cases (two NT, three A, five B1, two B2, one B3 and three TC), analyses of mutations, promoter methylation and comparisons ofPTENmRNA andPTENP1transcripts were undertaken using PCR-direct sequencing, methylation-specific PCR, and reverse-transcription real-time PCR after target cell collection with laser microdissection.
  
  
  RESULTS
  PTEN protein was not immunohistochemically detected in NT epithelium or types B1 or B2 thymoma cells, but was expressed in type A thymoma and carcinoma cells. NeitherPTENmutations nor promoter methylation were detected in any samples. Statistical analysis revealed thatPTENmRNA expression was highest in NT epithelium and lowest in type A thymoma cells.PTENP1transcript expression did not significantly differ among NT, thymoma and TC samples.
  
  
  CONCLUSIONS
  We speculated that NT epithelium and types B1/B2 thymoma cells have a mechanism ofPTENtranslation repression and/or acceleration of protein degradation, whereas type A thymoma cells exhibit transcriptional repression ofPTENmRNA and accelerated translation and/or protein accumulation.
authors.affiliation: Respiratory Disease Center, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Masunaga
authors.affiliation: Department of Clinicodiagnostic Pathology, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Omatsu
authors.affiliation: Department of Clinicodiagnostic Pathology, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kunimura
authors.affiliation: Respiratory Disease Center, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Shugo
authors.initials: S
authors.lastname: Uematsu
authors.affiliation: Department of Emergency Medicine, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kamio
authors.affiliation: Respiratory Disease Center, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kitami
authors.affiliation: Molecular Pathology & Genetics Division, Kanagawa Cancer Center Research Institute, Yokohama, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Miyagi
authors.affiliation: Department of Pathology, Tokyo Women's Medical University Yachiyo Medical Center, Yachiyo, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hiroshima
authors.affiliation: Respiratory Disease Center, Showa University Northern Yokohama Hospital, Yokohama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
mesh_terms: D000328:Adult; D000368:Aged; D002648:Child; D019175:DNA Methylation / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011544:Pseudogenes / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D013945:Thymoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D013950:Thymus Gland / Q000378:metabolism*; D013953:Thymus Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D047368:Tumor Burden
chemical_list: D012333:RNA, Messenger; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human
keywords: CANCER; HISTOPATHOLOGY; IMMUNOCYTOCHEMISTRY; MOLECULAR PATHOLOGY; TUMOUR BIOLOGY