Priming with GM-CSF instead of G-CSF enhances CAG-induced apoptosis of acute monocytic leukemia cells in vitro

High expression of granulocyte–macrophage colony-stimulating factor (GM-CSF) receptor has been found in myelomonocytic or monocytic subtypes (M4/M5) of acute myeloid leukemia. Herein, we aimed to improve the effect of CAG [Ara-C, ACR, and G-CSF (granulocyte colony-stimulating factor)] regimen for acute monocytic leukemia by replacing G-CSF with GM-CSF. Results showed that the percentage of cells in S phase was higher with GM-CSF than with G-CSF treatment at 20 ng/mL (P < 0.05). When THP-1 and SHI-1 cells were primed with 20 ng/mL G-CSF or GM-CSF followed by Ara-C and ACR, cell proliferation rate in the CAGM (Ara-C, ACR, and GM-CSF) regimen was lower than in the CAG regimen (P < 0.05). Furthermore, CAGM regimen induced more obvious cell apoptosis than CAG regimen probably by reducing Bcl-2/Bax ratio (P < 0.05). Similar results were seen in primary cells from M5 patients. Collectively, our study suggests that priming with GM-CSF may be more effective than G-CSF in CAG regimen in acute monocytic leukemia.