ALDH4A1 and breast cancer: In fact, ALDH1A3 was identified as the dominant isoform in breast cancer responsible for ALDEFLUOR activity.17 In colon cancer cell lines, ALDH1A3 is upregulated in chemoresistant lines29 and its regulation in chemoresistant lines may be due to changes in expression.30 While there is no data, to our knowledge, showing any links between ALDH4A1, ALDH6A1, and ALDH7A1 expression and colon cancer, our findings show changes in expression of these three isoforms at the mRNA level.