Biological profiles of endocrine breast cancer
avAnna Göthlin Eremo
Akademisk avhandling
Avhandling för medicine doktorsexamen i Medicinsk Vetenskap, inriktning Biomedicin,
som kommer att försvaras offentligt fredag den 29 maj 2015 kl. 09.00,
Wilandersalen, M-huset, Universitetssjukhuset Örebro Opponent: Docent Agneta Jansson
Institutionen för klinisk och experimentell medicin, Onkologi, Linköpings Universitet
Örebro universitet
Institutionen för Hälsovetenskap och Medicin 701 82 ÖREBRO
Abstract
Anna Göthlin Eremo (2015): Biological profiles of endocrine breast cancer. Örebro Studies in Medicine 123
The majority of breast cancer patients have a hormone responsive tumor and are candidates for endocrine treatment. Adjuvant tamoxifen signifi-cantly lowers the risk of recurrence for most patients, however up to 40% still experience a tumor relapse and the importance of finding addi-tional predictive factors is substantial. The objective of present thesis was to study molecular aspects of tamoxifen resistance in endocrine breast cancer. We evaluated the transcription factor Foxl2 which may activate the enzyme aromatase (CYP19A1) gene expression, followed by in-creased intratumoral estrogen levels. We discovered Foxl2 and aroma-tase co-expression in tumor tissue and patients with nuclear Foxl2 had a longer recurrence-free survival. Protein expression of the tumor suppres-sor Wwox has previously been associated to endocrine breast cancer. The function of Wwox seem to be via protein-protein interactions, by keeping certain transcription factors from entering the nucleus. We found that patients with expression of Wwox had an improved recur-rence-free survival compared to Wwox-negative, but only among those given adjuvant tamoxifen. Further, nuclear localization of the HER4 intracellular domain (4ICD) is a co-activator of ERα, although Wwox interaction may cause cytoplasmic sequestration. We investigated co-expression patterns of Wwox and 4ICD however found no correlations to patients’ survival. Finally, we conducted a microarray study of gene expressions in tumors from tamoxifen treated patients with or without a distant recurrence. We found genes (e.g. AGTR1, S100P and AREG) with possible associations to endocrine resistance, which could offer basis for further investigations. In a future perspective, increased knowledge of tamoxifen resistance may lead to improved personalized medicine and hence survival for patients with endocrine breast cancer.
Keywords: Endocrine breast cancer, tamoxifen, Foxl2, Wwox, ErbB4,
HER4, gene expression, randomized patients.
Anna Göthlin Eremo, School of Health and Medical Sciences Örebro University, SE-701 82 Örebro, Sweden.
