ERBB2 and breast cancer: In addition, a series of experimental and clinical findings have suggested that aberrant activation of tyrosine receptor kinases, such as EGFR/HER1 and HER2 pathways, play a causal role in the development of antioestrogen resistance in breast cancer (van Agthoven et al, 1992; Benz et al, 1993; Houston et al, 1999; Dowsett et al, 2001; Wakeling et al, 2001).