For primary ovarian cancer cells, the lower ALDH1 activity was observed compared to corresponding immortalized cells: for OvCa3 A (1.00 mU/mL ± 0.10 mU/mL vs. 1.92 mU/mL ± 0.01 mU/mL), and for OvCa7 A (1.33 mU/mL ± 0.10 mU/mL vs. 7.20 mU/mL ± 0.05 mU/mL), respectively. Here, ALDH1A1 is linked to ovarian cancer.