Inhibition of CRM1 reverses hypoxia-driven chemoresistance in acute myeloid leukemia via overcoming HIF-1α-mediated lysosomal sequestration.

INTRODUCTION: In relapsed/refractory acute myeloid leukemia (R/R-AML), hypoxia-driven chemoresistance is orchestrated by HIF-1α-induced P-glycoprotein (P-gp) overexpression and subsequent lysosomal sequestration of anthracyclines. Nuclear-cytoplasmic shuttling of the HIF-1α prolyl-hydroxylase PHD2 is controlled by chromosome region maintenance 1 (CRM1), which is frequently up-regulated in AML; however, whether pharmacologic CRM1 inhibition restores PHD2 nuclear availability to accelerate HIF-1α degradation and reverse chemoresistance remains undefined.

METHODS: AML cell lines (MV4-11 and MOLM13) were cultured under normoxic or hypoxic conditions. The effects of hypoxia on drug sensitivity, intracellular drug distribution, and protein expression were assessed using CCK-8 assays, immunofluorescence, Western blot, and flow cytometry. Genetic and pharmacological inhibition of P-gp, HIF-1α, and CRM1 was performed to validate their roles in chemoresistance. Hypoxia-adapted zebrafish CHT xenografts were employed for in vivo validation.

RESULTS: Hypoxia reduced AML cell sensitivity to DNR, increased HIF-1α and P-gp expression, and promoted lysosomal sequestration of DNR. Inhibition of P-gp or HIF-1α reversed these effects. CRM1 and PHD2 expression increased under hypoxia, but nuclear accumulation of PHD2 decreased. Selinexor restored PHD2 nuclear localization, promoted HIF-1α degradation, reduced P-gp expression, and enhanced DNR nuclear accumulation. Combination treatment with Selinexor and DNR significantly increased apoptosis and DNA damage in vitro and reduced leukemia burden in zebrafish xenografts.

CONCLUSIONS: CRM1 inhibition by Selinexor re-establishes nuclear PHD2 residency, increases the degradation of HIF-1α in hypoxia, abrogates P-gp-mediated lysosomal anthracycline trapping, and confers potent in-vitro and in-vivo chemosensitization. These data provide mechanistic rationale for integrating Selinexor into salvage regimens for R/R-AML.