Interaction of the MUC1 Tumor Antigen and the Adenomatous Polyposis Coli Tumor Suppressor in Human Breast Cancer

摘要

This project examines the interaction of MUC1, a breast tumor antigen, with APC, a potent tumor suppressor. We have focused on Task 4 in the approved Statement of Work: 'To clarify the functional significance of the interaction in relation to b-catenin and ErbB signaling'. TO this end, we have determined that APC most likely interacts preferentially with wildtype MUC1 as compared to a MUC1 mutant lacking tyrosines in the cytoplasmic tail. We have created several constructs to overcome difficulties associated with poor APC antibodies: His (exp-6) and myc-tagged, as well as constructs for tandem affinity purification (TAP) and fluorescence resonance energy transfer (FRET). We have expressed APC in breast cell lines under a zinc-inducible promoter, but have determined that these cells are too inconsistent to use for immunoprecipitations. In another breast cancer cell lines, MDA-MB-468, we have successfully knocked down MUC1 expression using siRNA technology; interestingly, the reduced level of MUC1 correlated with a decrease in active b-catenin in these cells. Our upcoming studies will make use of TAP, FRET, and siRNA as complementary assays in examining the role of the MUC1-APC interaction in human breast cancer.