Importantly, while the ALDEFLUOR reagent is metabolized by some preferred isoforms of ALDH, this demarcation is not strict, which makes the assay less specific.35,64 For instance, ALDH7A1 contributes to the fraction of cells with high-ALDH activity in prostate cancer, whereas ALDH3B1 is highly expressed in breast and lung tumors (reviewed by Marcato et al 2011). This evidence concerns the gene ALDH3B1 and prostate cancer.