Combined Targeting of SYK and BCL-2 in Acute Myeloid Leukaemia and Mechanism Study

Acute myeloid leukemia (AML) is a highly heterogeneous haematological malignancy and is the most common acute leukaemia in adults, with a median age of onset of 68 years and a 5-year survival rate of only 30%. Only 60-80% of adult AML patients can achieve complete remission with the first induction chemotherapy, and 50-80% of AML patients ultimately relapse with the “3+7” first-line treatment regimen based on anthracycline and cytarabine (Ara-C), so there is an urgent need to find safer and more effective targeted therapies. There is an urgent need to find safer and more effective targeted therapies.

Venetoclax (ABT-199) is an FDA-approved oral selective Bcl-2 inhibitor with limited anti-leukaemia activity as a single agent, and mechanisms of resistance include up-regulation of anti-apoptotic proteins, compensation of multiple metabolic pathways such as OXPHOS glycolysis, and mutations in BCL-2 and BAX.In 2018, the FDA approved the use of Venetoclax in combination with demethylating drugs (azacitidine ( AZA) or low-dose azacitidine AraC (LDAC)) in combination for newly diagnosed AML in older adults aged 75 years and older, and while this combination greatly improves remission rates, most patients relapse within 18 months. It has been suggested that direct or indirect inhibition of oxidative phosphorylation (OXPHOS) may be able to circumvent adaptive resistance of AML to Venetoclax+ AraC combination therapy. Therefore, an ideal candidate therapy in combination with Venetoclax should be able to antagonise its resistance mechanisms from metabolic pathways and down-regulation of MCL-1.

Purpose

To investigate the efficacy and related mechanisms of co-targeting SYK with BCL-2 for the treatment of acute myeloid leukaemia (AML).

Experimental Design

AML cell lines and primary patient samples were collected for cell proliferation assays. Firstly, cell activity was detected by MTS colorimetric assay, by Compusyn calculation software, the joint index CI value was calculated, apoptosis was detected by flow cytometry, mitochondrial membrane potential was altered, gene expression was detected by transcriptome sequencing, and the signalling pathways were analysed, followed by apoptosis-related proteins, BCL-2-related proteins by Western Blot, and glucose was detected by metabolism kit. sugar consumption,ATP and lactate content. The in vivo efficacy of the combination of Venetoclax and Entospletinib was assessed using an MV4-11-derived xenograft mouse model.

Results

SYK is highly expressed in AML and is associated with poor prognosis. ...The combination of Venetoclax and Entospletinib in AML cell lines and AML primary patient cells had significant synergistic growth inhibitory and apoptosis-inducing effects...Venetoclax in combination with Entospletinib down-regulated the expression of anti-apoptotic proteins, MCL-1, and BCL-XL, and down-regulated phosphorylated ERK expression, thereby affecting MCL1 post-translational protein stability rather than transcriptional levels.... Venetoclax in combination with Entospletinib downregulated the expression of anti-apoptotic proteins MCL-1, BCL-XL and phosphorylated ERK, thereby affecting the post-translational protein stability of MCL1, but not the transcriptional level.

Conclusions

The combination of Venetoclax and Entospletinib had significant synergistic killing effects in both AML cell lines and AML primary patient cells.Venetoclax in combination with Entospletinib exerts synergistic therapeutic effects on AML through down-regulation of ERK phosphorylation affecting the expression of anti-apoptotic proteins MCL-1, BCL-XL and reprogramming of glucose metabolism.

No relevant conflicts of interest to declare.