Founded in 1993
  Year: 2006 | Volume: 14 | Issue: 3-4 | Pages: 106-109
  Original Article
  THE ROLE OF ESTROGEN RECEPTORS ISOFORMS IN BREAST CANCER
Mandusic V, Nikolic-Vukosavljevic D, Neskovic-Konstantinovic Z, Tanic N, Celeketic D, Dimitrijevic B.
  DOI: 10.2298/AOO0604106M
  Abstract:
  Background: Estrogen and progesterone receptor (ER/PR) status is an accepted predictive marker in breast cancer. It is well known that breast tumors, which are ER(+) are more likely to respond to endocrine therapy. However, certain percentage of ER(+)/PR(+) tumors do not respond to endocrine therapy. Identification of the second estrogen receptor, named estrogen receptor beta (ERa), as well as the existence of numerous isoforms/splice variants of both ERa and ERb, suggests that complex regulation of estrogen action exists. In this study, we analyze does the expression of two ERb isoforms correlates with ERa/PR status.
Methods: Sixty samples of primary operable breast carcinomas were analyzed for ERa and PR protein levels and for mRNA expression of two ERb isoforms (ERb1 and ERbD5). ERa and PR proteins were measured by classical biochemical techniques, and ERb mRNAs were measured by real-time RT-PCR.
Results: Tumors are divided in three groups according to relative level of mRNA for ERb1 and ERbD5. We found that there is no correlation of ERb1 mRNA expression with ERa and PR protein levels. We confirmed the existence of inverse correlation of ERbD5 with PR and of ERbD5 with ERa in the group of postmenopausal patients. In the subsets of tumors defined by ERa/PR status, we found that percentage of tumors, which concomitantly expressed high levels of both transcripts, are parallel with those that do not response to tamoxifen treatment.
Conclusion: Inverse correlation of ERa with ERbD5 and PR with ERbD5 isoform suggests that ERbD5 may have inhibitory effect on ERa activity in postmenopausal patients. In addition, we point out that determination of expression profiles of ERa and ERb isoforms in the defined groups of patient are necessary for elucidating its involvement in endocrine resistance.
  Key words: Breast Neoplasms; Receptors, Estrogen; Receptors, Progesterone; Antineoplastic Agents, Hormonal; Reverse Transcriptase Polymerase Chain Reaction
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Founder, owner and publisher: Oncology Institute of Vojvodina, Serbia
Online since 1997 (Abstracts only); 2000 (Abstracts and Full text)
ISSN: 0354-7310 eISSN: 1450-9520