SMURF1 and breast cancer: SMURF1 also shows tumor-promotor activity in breast cancer cells where the ubiquitination function of SMURF2 can promote SMURF1 degradation and, consequently, may rescue important tumor suppressive substrates of SMURF1 to prevent malignant migration of tumor cells (Fukunaga et al. 2008; Borroni et al. 2018b).