The impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen treatment in breast cancer patients

Cancer Biol Ther. 2012 Oct;13(12):1165-74. doi: 10.4161/cbt.21346. Epub 2012 Aug 15.

Abstract

Tamoxifen is a standard therapeutical treatment in patients with estrogen receptor positive breast carcinoma. However, less than 50% of estrogen receptor positive breast cancers do not respond to tamoxifen treatment whereas 40% of tumors that initially respond to treatment develop resistance over time. The underlying mechanisms for tamoxifen resistance are probably multifactorial but remain largely unknown. The primary aim of this study was to investigate the impact of PTEN tumor suppressor gene on acquiring resistance to tamoxifen by analyzing loss of heterozygosity (LOH) and immunohystochemical expression of PTEN in 49 primary breast carcinomas of patients treated with tamoxifen as the only adjuvant therapy. The effect of PTEN inactivation on breast cancer progression and disease outcome was also analyzed. Reduced or completely lost PTEN expression was observed in 55.1% of samples, while 63.3% of samples displayed LOH of PTEN gene. Inactivation of PTEN immunoexpression significantly correlated with the PTEN loss of heterozygosity, suggesting LOH as the most important genetic mechanism for the reduction or complete loss of PTEN expression in primary breast carcinoma. Most importantly, LOH of PTEN and consequential reduction of its immunoexpression showed significant correlation with the recurrence of the disease. Besides, our study revealed that LOH of PTEN tumor suppressor was significantly associated with shorter disease free survival, breast cancer specific survival and overall survival. In summary, our results imply that LOH of PTEN could be used as a good prognostic characteristic for the outcome of breast cancer patients treated with tamoxifen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Breast Neoplasms* / drug therapy
  • Breast Neoplasms* / genetics
  • Breast Neoplasms* / pathology
  • Drug Resistance, Neoplasm / genetics*
  • Estrogens / metabolism
  • Female
  • Genes, Tumor Suppressor
  • Humans
  • Loss of Heterozygosity
  • Middle Aged
  • Neoplasms, Hormone-Dependent* / drug therapy
  • Neoplasms, Hormone-Dependent* / genetics
  • Neoplasms, Hormone-Dependent* / metabolism
  • PTEN Phosphohydrolase* / genetics
  • PTEN Phosphohydrolase* / metabolism
  • Prognosis
  • Tamoxifen / administration & dosage*
  • Treatment Outcome
  • Tumor Suppressor Proteins / genetics

Substances

  • Estrogens
  • Tumor Suppressor Proteins
  • Tamoxifen
  • PTEN Phosphohydrolase
  • PTEN protein, human