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17β-hydroxysteroid dehydrogenases involved in local oestrogen synthesis have prognostic significance in breast cancer
Linköping University, Department of Biomedicine and Surgery, Oncology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Biomedicine and Surgery, Oncology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Biomedicine and Surgery, Oncology. Linköping University, Faculty of Health Sciences.
2005 (English)In: British Journal of Cancer, ISSN 0007-0920, E-ISSN 1532-1827, Vol. 92, no 3, 547-552 p.Article in journal (Refereed) Published
Abstract [en]

The 17β-hydroxysteroid dehydrogenase (17HSD) enzymes are involved in the local regulation of sex steroids. The 17HSD type 1 enzyme catalyses the interconversion of the weak oestrone (E1) to the more potent oestradiol (E2), whereas 17HSD type 2 catalyses the oxidation of E2 to E1. The aim of this study was to correlate the expression of these enzymes in the tumour with the recurrence-free survival of tamoxifen-treated breast cancer patients. We used real-time reverse transcriptase PCR to investigate the mRNA expression of 17HSD types 1 and 2 in tumour samples from 230 postmenopausal patients. For the patients with oestrogen receptor (ER)-positive breast cancer, we found a statistically significant positive correlation between recurrence-free survival and expression of 17HSD type 2 (P = 0.026). We examined the ratio of 17HSD types 2 and 1, and ER-positive patients with low ratios showed a significantly higher rate of recurrence than those with higher ratios (P = 0.0047), ER positive patients with high expression levels of 17HSD type 1 had a significantly higher risk for late relapse (P = 0.0051). The expression of 17HSD types 1 and 2 in breast cancer differs from the expression of these enzymes in normal mammary gland, and this study indicates that the expression has prognostic significance in breast cancer.

Place, publisher, year, edition, pages
2005. Vol. 92, no 3, 547-552 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-24442DOI: 10.1038/sj.bjc.6602375Local ID: 6550OAI: oai:DiVA.org:liu-24442DiVA: diva2:244760
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Steroid converting enzymes in breast cancer
Open this publication in new window or tab >>Steroid converting enzymes in breast cancer
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Estrogens play a central role in the development of breast cancer. Most breast carcinomas are detected after menopause and despite a low degree of ovarian estrogen production and low levels of serum estrogen these tumors show a high in situ level of estrogens. Enzymes modulating local steroid availability seem to play an important role in the progression of especially estrogen receptor positive breast cancer. The 17ß-hydroxysteroid dehydrogenase (17ß-HSD) enzymes are involved in the interconversion of biologically active and inactive sex steroids and are considered to play a critical role in the in situ metabolism of estrogen.

The aim of this thesis was to investigate the expression of 17ß-HSD type 1 and 2 in breast cancer and correlate this to prognosis, and to analyze if the gene encoding 17ßHSD type 1 exhibits altered gene copy number in breast cancer. We also wanted to examine if the protein levels of aromatase, 17ßHSD type 1 and 17ßHSD type 2 show association with the expression of COX-2 in breast tumors and whether these proteins correlate to prognosis. Real-time RT-PCR was used to detect the rnRNA levels of 17ßHSD type 1 and type 2, and immunohistochemistry to detect the protein expression. To analyze if the gene encoding 17ßHSD type 1 exhibits altered gene copy number in breast cancer we used real-time PCR and genomic DNA.

While 17ßHSD type 1 catalyzes the conversion of estrone to the more potent estradiol, the type 2 enzyme catalyzes the opposite reaction. All tumors investigated in this study exhibited detectable rnRNA levels of 17ßHSD type 1. We found detectable rnRNA levels of 17ßHSD type 2 in the normal breast tissue, whereas many tumors lacked expression of type 2, especially among ER-positive tumors. In Paper I the expression of 17ßHSD type 2 was detectable in 14% of the tumors and in Paper III 17ßHSD type 2 mRNA was detected in 69% of the tumors. The expression of 17ßHSD type 2 seems to be lost in a subset of the breast tumors.

In Paper II we found amplification of the gene coding for 17ßHSD type 1 in 14.5% of the cases. HSD17B1 amplification had prognostic significance, and in particular, for ER-positive patients who received tamoxifen treatment, increased gene copy number indicated a decreased breast cancer survival. There was a significant correlation between HSD17B1 gene copy number and mRNA expression level of 17ßHSD type 1, when analyzing a subgroup of the patients.

In Paper II, among ER-positive patients, those with low expression of type 2 had a significantly higher recurrence rate compared with patients who expressed normal levels and this difference could not be seen among ER-negative patients. The prognostic significance of type 2 hold true in multivariate analysis. In Paper I, patients with late relapse in their disease more frequently had lost the mRNA expression of 17ßHSD type 2 than had matched control patients. In Paper IV, patients with ER-positive breast tumors with low protein levels of 17ßHSD type 2 had a worse prognosis, both concerning distant recurrence and breast cancer related death. In Paper I a high mRNA level of 17ßHSD type 1 predicted late relapses among breast cancer patients, however, in Paper IV a prognostic value of 17ßHSD type 1 could not be detected. In Paper III, there was no significant association between 17HSD type 1 and recurrence-free survival if the entire follow-up period was considered. However, for ER-positive patients still recurrence-free after 5 years, high levels of 17HSD type 1 was associated with a significantly higher rate of late relapse in the disease. When 17ßHSD type 1 and 2 were considered together, the expression ratio was a significant prognostic variable.

COX-2 protein expression was significantly correlated to aromatase, 17ßHSD type 1 and 17ßHSD type 2 levels, and this suggests that COX-2 might contribute to the upregulation of steroid converting enzymes. However, any significant prognostic value of COX-2 or aromatase could not be detected.

In summary, these results suggest that 17ß-HSD type 1 and 2 have prognostic importance in estrogen dependent breast cancer.

Place, publisher, year, edition, pages
Linköping: Linköpings universitet, 2005. 76 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 908
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-31153 (URN)16890 (Local ID)91-85299-21-9 (ISBN)16890 (Archive number)16890 (OAI)
Public defence
2005-09-22, Berzeliussalen, Hälsouniversitetet, Linköping, 09:00 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-09-25Bibliographically approved

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Gunnarsson, CeciliaHellqvist, EvaStål, Olle

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