Recent research by our group using human breast cancer cell lines indicate that although both isoforms are involved in different phases of the metastatic cascade, 50 % of the ALDEFLUORTM activity is driven by the ALDH1A3 isoform with no significant participation of ALDH1A1 in this assay (our unpublished data). The gene discussed is ALDH1A1; the disease is breast carcinoma.