Tyrosine kinase signalling in breast cancer

Cells are continuously exposed to diverse stimuli ranging from soluble endo crine and paracrine factors to signalling molecules on neighbouring cells. Receptors of the tyrosine kinase family play an important role in the integ ration and interpretation of these external stimuli, allowing a cell to res pond appropriately to its environment. The activation of receptor tyrosine kinases (RTKs) is tightly controlled, allowing a normal cell to correctly i ntegrate its external environment with internal signal transduction pathway s. In contrast, due to numerous molecular alterations arising during the co urse of malignancy, a tumour is characterized by an abnormal response to it s environment, which allows cancer cells to evade the normal mechanisms con trolling cellular proliferation. Alterations in the expression of various R TKs, in their activation, and in the signalling molecules lying downstream of the receptors play important roles in the development of cancer. This to pic is the major focus of the thematic review section of this issue of Brea st Cancer Research.