Increased gamma-tubulin expression and P16INK4A promoter methylation occur together in preinvasive lesions and carcinomas of the breast

Ann Oncol. 2009 Mar;20(3):441-8. doi: 10.1093/annonc/mdn651. Epub 2009 Jan 8.

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.

Materials and 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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology
  • DNA Methylation*
  • DNA Primers
  • Genes, p16*
  • Humans
  • Immunohistochemistry
  • Neoplasm Invasiveness
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic*
  • Tubulin / genetics
  • Tubulin / metabolism*

Substances

  • DNA Primers
  • Tubulin