STAT3 and breast cancer: Thus, in breast cancer, it has been reported that STAT3 upregulates the expression and function of β-catenin (Armanious et al. 2010) whilst in oesophageal and some haematological malignancies, β-catenin appears to upregulate the expression of STAT3 (Yan et al. 2008; Anand et al. 2010).