MTOR and acute myeloid leukemia: In comparison to other AML cell lines, U937 cells have higher activity of Akt and mTOR, probably due to heterozygous deletion of phosphatase and tensin homolog (PTEN),45,46 and loss of PTEN has been reported to inhibit autophagy without affecting LC3 lipidation,47 which raises a possibility that even low level of autophagy in U937 cells may be sufficient for differentiation to occur.