DLL4 and lung carcinoma: In contrast, activation of SIRT1 signaling through the use of the small molecules SRT1720 or SRT2183 inhibited DLL4-mediated induction of HEY1 and HEY2 expression, indicating that SIRT1 negatively modulated DLL4/Notch1 signaling in lung cancer-derived ECs (Fig. S1D).