HES1 and acute lymphoblastic leukemia: This is in line with a study reporting the activity of NOTCH in inducing apoptosis in several B-ALL cell lines: here, the activation of NOTCH resulting in NOTCH target Hairy/Enhancer of Split1 (HES1)-mediated PARP1 activation and subsequent apoptosis-inducing factor (AIF)-induced apoptosis may in part explain the contrasting effects of NOTCH signaling in B-ALL versus T-ALL, representing a mechanism of cell-specific consequences of NOTCH activation.