Targeting PI3K/AKT/mTOR pathway to enhance the anti-leukemia efficacy of venetoclax.

BACKGROUND: The treatment of acute myeloid leukemia (AML) is developing towards "targeted therapy", which faces challenges such as low sensitivity and drug resistance. Therefore, targeted drugs need to be used in combination with other drugs to overcome clinical problems. OBJECTIVE: AML cells and animal models were used to determine the synergistic anti-leukemic effect of Dactolisib (BEZ235) and Venetoclax (ABT199) and explore its mechanism. METHODS: In vitro experiments, we used cell counting kit-8 (CCK8), flow cytometry, real-time quantitative PCR (qPCR), and Western blot to detect the anti-leukemic effects of ABT199 and BEZ235. In vivo experiments, female nude mice were injected subcutaneously with THP-1 cells to form tumors, evaluate the combined effect of ABT199 and BEZ235 by indicators such as tumor size, tumor weight, Ki67 and cleaved-Caspase3 staining. The mice's body weight and HE staining were used to evaluate the liver injury and adverse drug reactions. RESULTS: The combination of BEZ235 and ABT199 has a synergistic effect through promoting apoptosis and inhibiting proliferation. The BEZ235 increased the drug sensitivity of ABT199 by reducing the MCL-1 protein synthesis and promoted the degradation of MCL-1 protein, which is considered as the mechanism of reversing ABT199 resistance. Furthermore, the BEZ235 and ABT199 can synergistically enhance the inhibition of PI3K/AKT/mTOR pathway. CONCLUSION: The combination of BEZ235 and ABT199 exhibits a synergistic anti-tumor effect in AML by down-regulating MCL-1 protein.

Metformin exerts a synergistic effect with venetoclax by downregulating Mcl-1 protein in acute myeloid leukemia.

Background: Recently, one of the specific BH3-mimetics, Venetoclax has been approved by FDA providing new options for newly diagnosed AML patient especially who are unfitted to receive conventional chemotherapy. Though the clinical success of venetoclax has been achieved in clinical outcomes such as complete remission (CR) and overall survival. Acquired resistance to ABT-199 which is induced by the regulation of apoptosis pathway is still an important clinical problem. To this end, the attempt to combine drugs which can reverse the compensatory regulation is urgent. Methods: In three AML cell lines (KG-1, Kasumi-1 and THP-1), the anti-AML effects of the combination of ABT-199 (Venetoclax) and metformin or the two drugs used alone were compared. CCK8 was used to evaluate the cell viability, and flow cytometry was used to estimate the rate of apoptosis, Western blot method was performed to detect apoptosis-related protein levels. In mice experiments, female BALB/c-nu nude mice were subcutaneously injected with THP-1 cells for subcutaneous tumor formation, and the combined effect of ABT-199 and metformin was tested. The evaluation indicators were tumor size, tumor weight, and Ki67 staining. Mouse body weight and HE staining were detected to evaluate liver damage and adverse drug reactions. Results: Both in vitro and in vivo experiments showed that compared with metformin or ABT-199 alone, the combined use of the two drugs exerts a synergistic effect on promoting apoptosis, thereby producing a strong anti-leukemia effect. Furthermore, after a short incubation time, ABT-199 swiftly increased the expression level of the anti-apoptotic protein Mcl-1, while the combined use of metformin and ABT-199 significantly reduced the level of Mcl-1. Notably, Metformin significantly downregulates the level of Mcl-1 protein by inhibiting its protein production. To less extent, metformin can also downregulate the expression of another anti-apoptotic protein, BCL-xl. Conclusion: Metformin downregulates the expression of anti-apoptotic proteins Mcl-1 and Bcl-xl by inhibiting protein production, and shows a synergistic anti-tumor effect with ABT-199 in acute myeloid leukemia.