ALDH9A1 and prostate cancer: Indeed, ALDH1A1 along with ALDH2, ALDH1A3, ALDH6A1, ALDH7A1 or ALDH9A1 were found to be preferentially expressed in stem-like cell populations of breast and prostate cancer, but ALDH2 and ALDH7A1 were found to be part of an overlap in a gene expression profile analysis in different stem cell populations [26, 41, 42].