title: Increased gamma-tubulin expression and P16INK4A promoter methylation occur together in preinvasive lesions and carcinomas of the breast.
abstract: BACKGROUND
  Loss of p16(INK4A) due to promoter hypermethylation is correlated with the ability to acquire centrosomal abnormalities in variant human mammary epithelial cells. gamma-Tubulin is a highly conserved component of centrosome in most animal cells and gamma-tubulin protein overexpression could lead to centrosome aberration.
  
  
  METHODS
  A large series of breast premalignant lesions and carcinoma was analyzed. Real-time quantitative PCR and immunohistochemistry were carried out to measure gamma-tubulin copy numbers and protein expression. MethyLight and immunohistochemistry were carried out to determine p16(INK4A) methylation and protein expression.
  
  
  RESULTS
  gamma-Tubulin protein expression was concordant with gene amplification; both of them were found to increase with atypical ductal hyperplasia-carcinoma sequence. The median value and positive rate of p16(INK4a) methylation increased while protein expression displayed a decreasing trend. P16(INK4a) methylation showed a firm association with gamma-tubulin gene amplification.
  
  
  CONCLUSIONS
  gamma-Tubulin gene amplification and the concomitant protein overexpression present not only in invasive carcinoma but also in a significant fraction of atypical hyperplasia and in situ carcinomas. P16(INK4a) methylation and gamma-tubulin gene amplification had a synergistic effect on tumor progression. The synergism might arise as a result of the combined influence that p16(INK4a) and gamma-tubulin have on the G1-S cell cycle checkpoints and centrosome.
authors.affiliation: Breast Cancer Research Key Laboratory of National Education Ministry, Cancer Institute and Hospital, Tianjin Medical University, Tianjin, China.
authors.forename: T
authors.initials: T
authors.lastname: Liu
authors.forename: Y
authors.initials: Y
authors.lastname: Niu
authors.forename: Y
authors.initials: Y
authors.lastname: Yu
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: F
authors.initials: F
authors.lastname: Zhang
mesh_terms: D001483:Base Sequence; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation; D017931:DNA Primers; D019942:Genes, p16; D006801:Humans; D007150:Immunohistochemistry; D009361:Neoplasm Invasiveness; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D014404:Tubulin / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D014404:Tubulin