Regulation of proton partitioning in kinase-activating acute myeloid leukemia and its therapeutic implication

Abstract

Gain-of-function kinase mutations are common in AML and usually portend an inferior prognosis. We reported a novel mechanism whereby kinase mutants induced intracellular alkalization characteristic in oncogenesis. Thirteen kinases were found to activate sodium/hydrogen exchanger (NHE1) in normal hematopoietic progenitors, of which FLT3-ITD, KRASG12D, and BTK phosphorylated NHE1 maintained alkaline intracellular pH (pHi) and supported survival of AML cells. Primary AML samples with kinase mutations also showed increased NHE1 phosphorylation and evidence of NHE1 addiction. Amiloride enhanced anti-leukemic effects and intracellular distribution of kinase inhibitors and chemotherapy. Co-inhibition of NHE1 and kinase synergistically acidified pHi in leukemia and inhibited its growth in vivo. Plasma from patients taking amiloride for diuresis reduced pHi of leukemia and enhanced cytotoxic effects of kinase inhibitors and chemotherapy in vitro. NHE1-mediated intracellular alkalization played a key pathogenetic role in transmitting the proliferative signal from mutated-kinase and could be exploited for therapeutic intervention in AML.

Hexamethylene amiloride synergizes with venetoclax to induce lysosome-dependent cell death in acute myeloid leukemia

“…We found that the NHE1 expression level is elevated in AML patients compared to those who achieve CR, which is in line with the findings by Cheuk Him Man et al. 20 We also found that patients with a high NHE1 expression level had worse overall survival. Genetic or pharmacological inhibition of NHE1 hampers the growth of AML cells, and NHE1 knockdown counteract the effect of HA.…”

“…These results are in accordance with the previous studies. 19 , 20 Moreover, we also observed dose-dependent effects of HA on the promotion of cell death as demonstrated by increased Annexin V + cells and caspase-3/7 activity ( Figures 1 G, 1H, S1 H, and S1I). We also observed a dose-dependent decrease in cell proliferation by EdU assay ( Figures 1 I and S1 J), and the accumulation of DNA fragmentation by TUNEL assay ( Figures 1 J and S1 K).…”

“…In a recent published study by Cheuk Him Man et al., amiloride used as a NHE1 inhibitor was potential to reduce leukemic burden in vivo , implying targeting NHE1 is a feasible strategy. 20 However, direct evaluation of the safety and effectiveness of HA in vivo is lacking. Here, we demonstrate the therapeutic potential of HA combined with venetoclax in an AML cell-derived xenograft model.…”