ALDH1A1 and breast cancer: In studies on breast cancer, ALDH1A1 expression has been shown to lower the intracellular pH of breast cancer cells, which in turn promotes the phosphorylation of TAK1, activates the NF-κB signaling pathway, and results in the expansion of myeloid-derived suppressor cells and immune suppression, confirming that the enzymatic activity of ALDH1A1 promotes breast tumor growth (Liu et al., 2021).