ERBB2 and breast cancer: Shepherd et al (2001) has suggested that PEA3 has the potential to positively regulate HER2 transcription. Conversely, another study suggests that PEA3 represses HER2 promoter-reporter expression in a human ovarian and a human breast carcinoma cell line (Xing et al, 2000), and Xia et al (2006) have suggested that PEA3 expression does not correlate with HER2 expression in human breast cancer. These conflicting studies prompted us to undertake ex vivo studies in human breast tissue and in primary cell cultures derived from patient tumours.