MUC1 and breast carcinoma: MUC1 positive human breast cancer cell lines MCF-7 and T47D (Figure 3a) and HEK 293T cells transfected with MUC1-CFP (Figure 3b, panel 1) or the MUC1 splice variant lacking the tandem repeat domain MUCY-YFP-Fv (Figure 3b, panel 2) were lysed with or without prior treatment with the membrane permeable crosslinker DSS.