ALDH1A1 and breast carcinoma: While the expression of retinaldehyde dehydrogenases may contribute to stem-like characteristics in breast cancer [42,43,44], we identify no correlation between atRA sensitivity and the expression of ALDH1A1, ALDH1A2, ALDH1A3, or ALDH8A1 (Figure 2E); or with differential expression of these isoforms following atRA treatment (Figure 2F).