Modulation of epidermal growth factor receptor in endocrine-resistant, oestrogen receptor-positive breast cancer

There is an increasing body of evidence demonstrating that growth factor ne tworks are highly interactive with oestrogen receptor (ER) signalling in th e control of breast cancer growth. As such, tumour responses to anti-hormon es are likely to be a composite of the ER and growth factor inhibitory acti vity of these agents. The current article examines the modulation of growth factor networks during endocrine response, and presents in vitro and clini cal evidence that epidermal growth factor receptor signalling, maintained i n either an ER-dependent or -independent manner, is critical to antihormona l-resistant breast cancer cell growth. The considerable potential of the ep idermal growth factor receptor-selective tyrosine kinase inhibitor, ZD 1839 (Iressa; AstraZeneca) to efficiently treat, and perhaps even prevent, endo crine-resistant breast cancer is highlighted.