MUC1 and neoplasm: However, when MUC1 was overexpressed in MiaPaca2, TGF-β increased the viability of these cells significantly (Figure 4B), and when MUC1 was knocked down in HPAFII cells, TGF-β reduced cell viability (Figure 4C), thus clearly showing MUC1-dependent gain-of-function and loss-of function in TGF-β signaling switch towards a tumor promotor.