(A) Schematic diagram of MUC1/A, MUC1/B and MUC1ΔEX constructs used for transfection of COS-7 cells. The insertion of the FLAG tag within the N-terminal domain (NTD) is indicated. There are 42 tandem repeats (TR) in both MUC1/A and MUC1/B whereas MUC1ΔEX lacks the tandem repeat. The transmembrane (TM) and C-terminal domains (CD) are indicated. * indicates the SNP and nucleotide change between MUC1/B and MUC1/A. The black box indicates the additional 27 bp in MUC1/A. (B) Flow cytometry analysis of FLAG expression in COS-7 cells 24, 48 and 72 h post-transfection using M2 anti-FLAG antibody and PE-conjugated secondary antibody. Values are from one representative FACS analysis. (C) Western analysis of MUC1 protein expression in WCE from COS-7 cells either untransfected (UTx), transfected with the empty vector (EV), a mock control (no DNA), or expression vectors for MUC1/A or MUC1/B for 24, 48 and 72 h. 6 μg of WCE from MCF-7 cells was loaded into the far right lane as a positive control for MUC1. The blot was probed with CT2 anti-MUC1 antibody and β-actin which was used as a loading control. The bar graph shows the quantitation of MUC1/A and MUC1/B relative to β-actin expression relative to MCF-7 that was set to one for comparison.