Impact of altered growth factor signalling on endocrine response in breast cancer and the transition from ER+ to ER− disease

This article examines the experimental and clinical evidence of the effect of growth factor signalling in an attempt to reconcile the seeming paradox of, on the one hand, evidence that growth factor signalling can facilitate the activity of oestrogen receptor-α (ER-α), and on the other hand, evidence that extreme growth factor signalling can promote loss of ER function and expression, thereby promoting an endocrine insensitive and ultimately ER− phenotype. The results of this analysis lead to the therapeutic possibility that ER negativity may, in some instances, be reversible to generate endocrine response and improve patient prognosis.