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Homeobox B13 protein expression in a randomized tamoxifen trial of premenopausal breast cancer
Linköping University, Department of Clinical and Experimental Medicine, Cell Biology. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Clinical and Experimental Medicine, Oncology. Linköping University, Faculty of Health Sciences.
Department of Surgery, Helsingborg hospital, Helsingborg, Sweden.
Center for Molecular Pathology, Lund University, Malmö University hospital, Malmö, Sweden.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Homeobox B13 (HOXB13), part of the two-gene expression index HOXB13:IL17BR, has proven its capacity as a predictive factor of tamoxifen benefit in breast cancer. HOXB13 mRNA expression, as well as protein levels, have shown predictive value in postmenopausal patients. High levels were associated with decreased tamoxifen benefit and may indicate endocrine resistance. Here, we have analyzed HOXB13 protein expression in premenopausal breast cancer. We quantified the levels of HOXB13 with immunohistochemistry in tumor samples from 487 patients on tissue microarrays. Patients were diagnosed with stage II invasive breast cancer and randomized to tamoxifen or no endocrine treatment. HOXB13 protein analysis was successful for 367 patients. Data were correlated with clinicopathological variables. Investigation of tamoxifen benefit in patients with tumors expressing estrogen receptor (ER) α, progesterone receptor, or both, showed that patients with high HOXB13 levels had benefit from tamoxifen (hazard ratio for recurrences 0.43, 95% CI: 0.28-1.01, p=0.053). Corresponding numbers for the low HOXB13 group were 0.69 (95% CI: 0.44-1.07, p=0.10). For further analysis, we stratified the patients based on tumor ERβ status, which may function as a modifier of the performance of HOXB13 as a treatment predictive factor. For the ERβ positive subset of patients, there was a tendency towards a low HOXB13 expression associated with a better tamoxifen response. However, an increased benefit from tamoxifen, in terms of a longer recurrence-free survival (RFS), was associated with high HOXB13 expression in the ERβ negative group. The interaction between HOXB13 and treatment effect for RFS in the ERβ-negative group was significant in a multivariate model (p=0.04). In conclusion, in our study cohort, ERβ seems to be an additional determinant to HOXB13 protein expression for endocrine treatment prediction in premenopausal breast cancer. To identify patients less likely to respond to tamoxifen therapy, both HOXB13 and ERβ status should be taken into account.

National Category
Medical and Health Sciences
URN: urn:nbn:se:liu:diva-68120OAI: diva2:416452
Available from: 2011-05-11 Created: 2011-05-11 Last updated: 2011-05-12Bibliographically approved
In thesis
1. Homeobox B13 in breast cancer: Prediction of tamoxifen benefit
Open this publication in new window or tab >>Homeobox B13 in breast cancer: Prediction of tamoxifen benefit
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A major issue in the management of breast cancer is to identify patients who are less likely to be cured after primary treatment and would benefit from adjuvant chemotherapy. Of great importance is also identification of patients with only local disease who traditionally would be given chemotherapy but would survive without. In this thesis we have validated the utility of the two-gene ratio HOXB13:IL17BR, which previously has been demonstrated to predict disease-free survival in tamoxifen-treated breast cancer patients. We have also studied the prognostic and predictive utility of a single gene as a biomarker in breast cancer medicine.

We could confirm that HOXB13:IL17BR may classify patients with different treatment benefit; only patients with a low value showed benefit from prolonged duration of tamoxifen therapy, whereas for the group with high ratios, the long-term recurrence rate did not improve with longer treatment duration.

The combination of HOXB13:IL17BR and the molecular grade index (MGI), another prognostic marker, has been shown to outperform either alone in predicting risk of breast cancer recurrence. We validated the prognostic utility of HOXB13:IL17BR+MGI in a large randomized patient cohort and found that this risk classification identified more than 50% of the tamoxifen-treated lymph node-negative patients as having a less than 3% risk of distant recurrence and breast cancer death. Furthermore, we developed and tested a continuous risk model of HOXB13:IL17BR+MGI called Breast Cancer Index (BCI), for estimation of recurrence risk at the individual level. Our study shows that BCI has the ability to identify more than 50% of patients with a low risk of recurrence more accurately than using traditional risk assessment. These results suggest that BCI may help clinicians to make better informed treatment decisions and spare toxic chemotherapy for a large group of breast cancer patients.

The protein expression of HOXB13 was also shown to be a valuable predictor in postmenopausal patients. High expression was associated with worse outcome after tamoxifen therapy. In a premenopausal cohort, patients with hormone receptor-positive tumors showed benefit from tamoxifen regardless of HOXB13 expression. Further analysis indicated that estrogen receptor β (ERβ) modified the performance of HOXB13 as a predictor of treatment effect and should be taken into account when identifying patients less likely to respond to the therapy given.

In conclusion, BCI identifies patients with a very low risk of distant recurrence. It may be utilized in the management of breast cancer patients to optimize the use of chemotherapy. HOXB13 protein expression may be used as a marker for tamoxifen benefit, but its performance in premenopausal patients might be modified by ERβ.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 69 p.
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1243
National Category
Medical and Health Sciences
urn:nbn:se:liu:diva-68137 (URN)978-91-7393-184-7 (ISBN)
Public defence
2011-06-01, Berzeliussalen, Hälsouniversitetet, Campus US, Linköpings universitet, Linköping, 13:00 (Swedish)
Available from: 2011-05-12 Created: 2011-05-12 Last updated: 2011-05-12Bibliographically approved

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