AMD3465 sensitizes FLT3-mutated cells to FLT3 inhibitor–induced apoptosis. (A) The average percentage of annexin V⁺ Ba/F3-ITD and Ba/F3-FLT3 cells after exposure to AMD3465 alone, sorafenib alone, or sorafenib in combination with AMD3465 in the absence or presence of MS-5 cells for 24 hours. (B) Ba/F3-ITD and Ba/F3-FLT3 cells were treated with AMD3465, AG1296 (FLT3 inhibitor), or AG1296 in combination with AMD3465 in the absence or presence of MS-5 cells, and apoptotic cells were detected by annexin V flow cytometry. (C) MOLM13 carrying FLT3-ITD cells were treated with AMD3465, sorafenib, or their combination in the absence or presence of MS-5 cells for 24 hours, under normoxic (21% O₂) or hypoxic (2% O₂) conditions. Induction of apoptosis was measured by annexin V flow cytometry. (D) Blasts from primary AML samples with FLT3 mutations (n = 7) were treated with sorafenib alone or in combination with AMD3465 in coculture with MS-5 cells for 96 hours, and apoptosis induction was measured by annexin V flow cytometry after gating on CD34⁺ cells. The specific apoptosis was calculated using the formula described above. Error bars represent the SEM of each group.