ALDH1A1 and neoplasm: Similarly, ALDH1 was highly expressed in the most malignant cell line MDA-MB-231 while moderately expressed in MCF-7 and MDA-MB-468 that were less malignant (Fig. 1D,E and Supplementary Figure S1), which was consistent with the previously reported findings showing the correlation of ALDH1 with tumor malignancy and poor prognosis37,40.