Fig. 6From: C/EBPα-p30 confers AML cell susceptibility to the terminal unfolded protein response and resistance to Venetoclax by activating DDIT3 transcriptionActivation of DDIT3 expression synergizes with Venetoclax to enhance apoptotic death of BCL2 inhibitor-resistant NB4 cells through MCL1 inhibition in vitro and in vivo. A The protein levels of DDIT3 were increased in NB4 cells after the treatment of tunicamycin (100 ng/ml, 24 h) and sorafenib (3 μM, 24 h). B-C The protein level of MCL1 could be up-regulated by venetoclax, while down-regulated by tunicamycin (B) and sorafenib (C). The MCL1 levels of NB4 cells were further decreased by treatment with tunicamycin + venetocalx and sorafenib + venetoclax. D Combined treatment with tunicamycin and venetoclax resulted in increased apoptosis/cell death of NB4 cells compared to each drug alone. E The combination indexes (CIs) were calculated for each concentration combination of tunicamycin and venetoclax, and the CIs were all less than 1, indicating the synergistic effect. F Combined treatment with sorafenib and venetoclax resulted in increased apoptosis/cell death of NB4 cells compared to each drug alone. G The CIs were also calculated for each concentration combination of sorafenib and venetoclax, and the values were all less than 1. H NB4 cells treated with combination of tunicamycin (100 ng/ml, 24 h) and venetoclax (5 μM, 48 h) had a significantly increased proportion of cells in the G0/G1 phase and a significantly decreased proportion of cells in the G2/M phase compared to cells treated with a single drug or DMSO. I NB4 cells treated with combination of sorafenib (3 μM, 24 h) and venetoclax (5 μM, 24 h) had a significantly increased proportion of cells in the G0/G1 phase and a significantly decreased proportion of cells in the S phase compared to cells treated with a single drug or DMSO. J Treatment schedule and experimental set-up. K Quantification of bioluminescence showed the lowest tumor load in mice after treatment with venetocalx (100 mg/kg/d) + sorafenib (40 mg/kg/d) on day 7. L During the process of treatment, the group with co-administration of venetoclax and sorafenib continuously showed the lowest leukemia load by quantification of bioluminescence, and was the only group that showed a significantly decreased AML burden compared to vehicle group on day 14. M Kaplan-Meyer survival curve revealed that co-administration of venetoclax and sorafenib substantially prolonged animal survival compared to vehicle group (statistical analysis by Log-rank test, P = 0.0063). Data represent Mean ± SD (n = 3); Each animal group included 5 mice; *P < 0.05; **P < 0.01, ***P < 0.001, ****P < 0.0001Back to article page