Targeting FLT3-ITD signaling mediates ceramide-dependent mitophagy and attenuates drug resistance in AML

Blood. 2016 Oct 13;128(15):1944-1958. doi: 10.1182/blood-2016-04-708750. Epub 2016 Aug 18.

Abstract

Signaling pathways regulated by mutant Fms-like tyrosine kinase 3 (FLT3)-internal tandem duplication (ITD), which mediate resistance to acute myeloid leukemia (AML) cell death, are poorly understood. Here, we reveal that pro-cell death lipid ceramide generation is suppressed by FLT3-ITD signaling. Molecular or pharmacologic inhibition of FLT3-ITD reactivated ceramide synthesis, selectively inducing mitophagy and AML cell death. Mechanistically, FLT3-ITD targeting induced ceramide accumulation on the outer mitochondrial membrane, which then directly bound autophagy-inducing light chain 3 (LC3), involving its I35 and F52 residues, to recruit autophagosomes for execution of lethal mitophagy. Short hairpin RNA (shRNA)-mediated knockdown of LC3 prevented AML cell death in response to FLT3-ITD inhibition by crenolanib, which was restored by wild-type (WT)-LC3, but not mutants of LC3 with altered ceramide binding (I35A-LC3 or F52A-LC3). Mitochondrial ceramide accumulation and lethal mitophagy induction in response to FLT3-ITD targeting was mediated by dynamin-related protein 1 (Drp1) activation via inhibition of protein kinase A-regulated S637 phosphorylation, resulting in mitochondrial fission. Inhibition of Drp1 prevented ceramide-dependent lethal mitophagy, and reconstitution of WT-Drp1 or phospho-null S637A-Drp1 but not its inactive phospho-mimic mutant (S637D-Drp1), restored mitochondrial fission and mitophagy in response to crenolanib in FLT3-ITD+ AML cells expressing stable shRNA against endogenous Drp1. Moreover, activating FLT3-ITD signaling in crenolanib-resistant AML cells suppressed ceramide-dependent mitophagy and prevented cell death. FLT3-ITD+ AML drug resistance is attenuated by LCL-461, a mitochondria-targeted ceramide analog drug, in vivo, which also induced lethal mitophagy in human AML blasts with clinically relevant FLT3 mutations. Thus, these data reveal a novel mechanism which regulates AML cell death by ceramide-dependent mitophagy in response to FLT3-ITD targeting.

MeSH terms

  • Animals
  • Benzimidazoles / pharmacology*
  • Ceramides* / genetics
  • Ceramides* / metabolism
  • Cyclic AMP-Dependent Protein Kinases / genetics
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Drug Resistance, Neoplasm* / drug effects
  • Drug Resistance, Neoplasm* / genetics
  • Dynamins
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / metabolism
  • Humans
  • Leukemia, Myeloid, Acute* / drug therapy
  • Leukemia, Myeloid, Acute* / genetics
  • Leukemia, Myeloid, Acute* / metabolism
  • Male
  • Mice
  • Mice, Inbred NOD
  • Microtubule-Associated Proteins / antagonists & inhibitors
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Mitochondria / genetics
  • Mitochondria / metabolism
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism
  • Mitophagy* / drug effects
  • Mitophagy* / genetics
  • Mutation*
  • Phosphorylation / drug effects
  • Phosphorylation / genetics
  • Piperidines / pharmacology*
  • RNA, Small Interfering / pharmacology*
  • Signal Transduction* / drug effects
  • Signal Transduction* / genetics
  • fms-Like Tyrosine Kinase 3* / antagonists & inhibitors
  • fms-Like Tyrosine Kinase 3* / genetics
  • fms-Like Tyrosine Kinase 3* / metabolism

Substances

  • Benzimidazoles
  • Ceramides
  • MAP1LC3A protein, human
  • Microtubule-Associated Proteins
  • Mitochondrial Proteins
  • Piperidines
  • RNA, Small Interfering
  • FLT3 protein, human
  • fms-Like Tyrosine Kinase 3
  • Cyclic AMP-Dependent Protein Kinases
  • GTP Phosphohydrolases
  • DNM1L protein, human
  • Dynamins
  • crenolanib