ALDH1A1 and acute myeloid leukemia: Indeed, a positive correlation has been shown between low/absent ALDH1A1 activity and favorable prognosis in AML, as expected: patients with AML cells lacking ALDH1A1 had a favorable prognosis, and ALDH1A1− cell lines as well as primary leukemia cells were found to be sensitive to treatment with compounds that directly and indirectly generate toxic ALDH substrates including 4-hydroxynonenal and the clinically relevant compounds arsenic trioxide and 4-hydroperoxycyclophosphamide [12].