Abstract: Objective To investigate the effect of GI254023X, an ADAM10 (a desintegrin and metalloproteinase domain containing protein 10)inhibitor, on the proliferation and apoptosis of CCRF-CEM and Molt4 cell lines and its mechanisms. Methods CCRF-CEM and Molt4 cells were treated with different concentrations of GI254023X. Proliferation-inhibition curve was assayed and plotted by CCK-8 method. Cell viability and apoptosis were detected by flow cytometry with Annexin V and 7-AAD staining, and cell cycle changes were analyzed by flow cytometry. For mechanism exploration, the cleavage of Notch1 protein was determined by Western blot. The transcripts of anti-apoptotic genes Bcl-2, c-Myc, Mcl-1 , pro-apoptosis genes BAD, BAK and Notch1 target gene Hes-1 were detected by real-time PCR. Results GI254023X inhibited the proliferation of CCRF-CEM and Molt4 cells in a time-and dose-depended manner (the rvalues of CCRF-CEM cells for 24 and 48 h were 0.981 and 0.962, respectively, while r values of Molt4 cells for 24 and 48 h were 0.992 and 0.957, respectively). The half maximal inhibitory concentration (IC₅₀) values of CCRF-CEM cells for 24 and 48 h were (29.40±3.28) μmol/L and (11.14±2.21) μmol/L, respectively, while IC₅₀ values of Molt4 cells for 24 and 48 h were (19.04±1.58) μmol/L and (11.25±2.31) μmol/L, respectively. Compared with the control group,the apoptosis rate of cells increased with the increment of concentration of GI254023X. Cell cycles were arrested at G₀/G₁ phase. Compared with DMSO in the control group, the expression of cleaved Notch1 was down-regulated after the treatment with GI254023X.The mRNA levels of anti-apoptotic genes Bcl-2 , c-Myc, Mcl-1 and Notch1 target gene Hes-1 mRNA transcripts in CCRF-CEM and Molt4 cells were reduced in GI254023X treated group, while the mRNA levels of pro-apoptosis genes BAD, BAK increased. Conclusions GI254023X can inhibit the proliferation and induce apoptosis of CCRF-CEM and Molt4 cells.Its mechanism may be related to the inhibition of Notch1 pathway.