title: Altered Expression of PTEN and Its Major Regulator MicroRNA-21 in Pulmonary Neuroendocrine Tumors.
abstract: BACKGROUND
  Phosphatase and tensin homolog on chromosome ten (PTEN) is one of the most frequently inactivated tumor suppressors in various tumor types. MicroRNA-21 (miR-21) may affect tumor progression by post-transcriptional repression of expression of tumor suppressors, such as PTEN. This study was conducted to evaluate the significance of PTEN expression in pulmonary neuroendocrine (NE) tumors and to analyze the relationship between PTEN and miR-21 expressions.
  
  
  METHODS
  Expressions of PTEN and miR-21 were investigated by immunohistochemistry and real time reverse transcription-polymerase chain reaction, respectively, in 75 resected pulmonary NE tumors (23 typical carcinoids [TCs], nine atypical carcinoids [ACs], 22 large cell NE carcinomas [LCNECs], and 21 small cell lung carcinomas [SCLCs]).
  
  
  RESULTS
  Loss of PTEN expression was observed in four of 23 TCs (17.4%), four of nine ACs (44.4%), 16 of 22 LCNECs (72.7%) and nine of 21 SCLCs (42.9%) (p=.025). The expression level of miR-21 was significantly higher in high-grade NE carcinomas than in carcinoid tumors (p<.001). PTEN expression was inversely correlated with miR-21 expression (p<.001).
  
  
  CONCLUSIONS
  This study suggests that aberrant expression of PTEN in relation to miR-21 may represent an important step in the development and progression of pulmonary NE tumors.
authors.affiliation: Department of Pathology, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
authors.forename: Hyoun Wook
authors.initials: HW
authors.lastname: Lee
authors.affiliation: Department of Pathology, Gachon University Gil Medical Center, Incheon, Korea.
authors.forename: Seung Yeon
authors.initials: SY
authors.lastname: Ha
authors.affiliation: Department of Pathology, Dong-A University College of Medicine, Busan, Korea.
authors.forename: Mee Sook
authors.initials: MS
authors.lastname: Roh
keywords: Lung; MicroRNA-21, human; Neuroendocrine tumors; PTEN