ALDH1A3 and breast cancer: In cancer, a well‐known example is that ALDH1A3/RA signaling activates the downstream factors homeobox transcription factor A1 (HOXA1) gene, which possesses a RARE sequence that is previously shown to be inducible by RA35 and is hypomethylated in breast cancer cell line MDA‐MB‐468 cells to be a tumor suppressor.42