SUMO1 and breast cancer: As expected, we found that endogenous α-catenin was modified by SUMO1 in MDA-MB-231 cells instead of MCF-7 and T47D cells (Fig. 5a), and the α-catenin-SUMO1 band was also present in lysates from MDA-MB-157 cells when cells were infected with WT α-catenin but not the K870R mutant (Fig. 5b), suggesting that endogenous α-catenin may mainly be SUMOylated in basal-like breast cancer cells.