[Comment] Androgen receptor agonism in advanced oestrogen receptor-positive breast cancer

The androgen receptor is expressed in a majority of oestrogen receptor-positive breast cancers, acting as both a promoter and inhibitor of tumour cell growth under various conditions of oestrogen stimulation.1 When oestrogen receptors are activated, androgen receptors act as a competitive binder, decreasing downstream oestrogen receptor activity. However, in the setting of treatment with endocrine therapy, androgen receptors can act as an accessory growth pathway to bypass oestrogen receptor blockade.