ALDH1A1 and breast cancer: Studies have confirmed that MUC1-C induces ERK signaling and thereby phosphorylation and activation of C/EBPβ, and show that a complex of MUC1-C and C/EBPβ occupies the ALDH1A1 promoter and induces ALDH1A1 expression, promotes breast cancer progression (Poturnajova et al., 2021) (Figure 1D).