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R.S. Mali et al.
While MCL-1 inhibition (AMG 176) plus quizartinib improved survival, the response was inferior to venetoclax or navitoclax (BCL-2/BCL-XL) combined with quizartinib (Figure 4 A,C), demonstrating that inhibition of BCL-2 promotes enhanced anti-tumor efficacy compared to tar- geting MCL-1 in combination with FLT3-ITD inhibition. Co-targeting of BCL-2 and MCL-1 (venetoclax + AMG
176) resulted in shorter median survival compared with inhibition of BCL-2, BCL-XL and MCL-1 (navitoclax + AMG 176; Figure 4B-C) indicating that in order to achieve maximum efficacy in the MV4;11 model in vivo, inhibition of all three anti-apoptotic proteins may be required. Quizartinib plus venetoclax was superior to navitoclax plus AMG 176, suggesting that FLT3-ITD inhibition
A
Figure 7. FLT3-ITD inhibition primed cells to BCL-2 dependence. (A) MV4;11 cells were pre-treated for 6 hours with vehicle, 5 nM quizartinib or 20 nM sorafenib and depletion of intracellular cytochrome c was deter- mined following 1 hour exposure to BIM, BAD, HRK, MS- 1 and FS-1 peptides or venetoclax at the indicated con- centrations by flow cytometry. Data represents average ± standard deviation within the experiment. (B) MV4;11 and Molm13 cells were treated with 10 nM quizartinib for 24 hours followed by immunoprecipitation for BIM or BAK as indicated followed by Western blot analysis for BCL-2. (C) Cell lines were treated with 100 nM veneto- clax, 10 nM quizartinib or the combination for 24 hours and cell lysates were assessed by Western blot for BCL- 2 family proteins, cleaved caspase-3 and cleaved PARP as indicated. Data represents two independent experi- ments. FLT3-ITD: Fms-like tyrosine kinase 3 internal tan- dem duplication.
B
C
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haematologica | 2021; 106(4)