| Popis: |
Antagonistic sex hormone activity occurs in mammary gland development, whereby estrogen stimulates and androgen inhibits post-pubertal growth, but the mechanistic basis of this is largely unknown. Whether sex hormone antagonism occurs in the context of breast cancer is also unclear. The estrogen receptor alpha (ER) unequivocally drives the majority of breast malignancies, but the role of the androgen receptor (AR) is controversial, particularly in the context of ER-positive (ER+) tumours resistant to standard-of-care ER targeting therapies. The controversy has constrained clinical implementation of new drugs that influence AR activity for treatment of this disease. Using a diverse panel of cell line and patient-derived models of ER+ breast cancer, we demonstrate that activation, not suppression, of AR activity exerts potent anti-tumour activity in multiple clinically relevant contexts, including tumours resistant to ER targeting therapy. We also show that AR agonists can be combined with old and new (i.e. Palbociclib, a CDK4/6 inhibitor) standard-of-care agents to enhance therapeutic efficacy. Mechanistically, agonist activation of AR altered the distribution of ER and its coactivators (p300, SRC-3) on chromatin, resulting in repression of ER-regulated cell cycle genes and up-regulation of AR target genes, including known tumour suppressors. Consistent with the mechanistic findings, a gene signature of AR activity derived from in vivo models positively predicted disease survival in multiple large, well-annotated clinical cohorts of ER+ breast cancer, outperforming existing pan-cancer or breast cancer specific signatures. These findings provide compelling evidence that AR has a tumour suppressor role in ER+ breast cancer and resolves an important clinical controversy concerning the optimal AR-directed treatment strategy, revealing a rational therapeutic opportunity. |
