Internal tandem duplication (ITD) of FLT3 (fms-like tyrosine kinase 3) in acute myeloid leukemia (AML) is associated with inferior clinical outcome. Sorafenib is effective in targeting chemo-refractory FLT3-ITD+ AML. However, leukemia progresses invariably. Mechanisms of drug resistance are not completely understood. We hypothesized that a gene encoding tescalcin (TESC), which activate a sodium/hydrogen exchanger 1 (NHE1) and known to be up-regulated at leukemia progression during continuous sorafenib treatment, may underlie TKI resistance. TESC was over-expressed in FLT3-ITD+ AML lines MOLM-13 and MV4-11. Knocking down TESC by siRNA lowered intracellular pH and induced apoptosis. The results were recapitulated by treatment with a NHE1 inhibitor, 5-(N,N-Hexamethylene) amiloride (HMA). Sorafenib resistant MOLM-13 cell line (M13-RE) was generated by long term culture of sorafenib. M13-RE significantly increased its sensitivity to HMA. HMA also enhanced suppression of FLT3 signaling by sorafenib in otherwise resistant cell lines. Treating MOLM-13, MV4-11 and primary FLT3-ITD+ AML cells with HMA significantly reduced leukemia initiation in NOD/SCID mouse xenotransplantation. These observations provided novel information about the pathogenetic role of the TESC-NHE1-pHi axis in mediating sorafenib resistance in AML.

Disclosures:

No relevant conflicts of interest to declare.

Topics:
hydrogen, impedance threshold device, ms-like tyrosine kinase 3, sodium, sorafenib, leukemia, amiloride, chemotherapy regimen, leukemia, myelocytic, acute, protein-tyrosine kinase inhibitor

Author notes

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Asterisk with author names denotes non-ASH members.

© 2013 by The American Society of Hematology
2013
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