This finding suggests that the WW1 in WWP1 is the major interacting domain with ΔNp63α, and the tandem alignment of the other three WW domains may facilitate the interaction, as evidenced by the fact that the binding of WW1 and WW2 is stronger than that of WW3 and WW4.71 Lastly, WWP1 expression negatively correlates with p63 expression in numerous prostate and breast cancer cell lines, suggesting a tumorigenic role of WWP1. Here, WWP1 is linked to breast cancer.