TCF4 and breast cancer: Notably, we have previously shown that Sox2 activates Wnt signalling in hormone-resistant cells [12] and now find that Sox9, itself a Wnt-responsive gene [15, 60], also regulates Wnt signalling, in agreement with the observed association between Sox9 and the expression of Wnt/β-catenin components LRP6 and Tcf4 in breast cancer [29].