Sphingosine kinase-1 and Sphingosine 1-phosphate Receptor 2 Mediate Bcr-Abl1 Stability and Drug Resistance by Modulation of Protein Phosphatase 2A

Blood. 2011 Jun 2;117(22):5941-52. doi: 10.1182/blood-2010-08-300772. Epub 2011 Apr 28.

Abstract

The mechanisms by which sphingosine kinase-1 (SK-1)/sphingosine 1-phosphate (S1P) activation contributes to imatinib resistance in chronic myeloid leukemia (CML) are unknown. We show herein that increased SK-1/S1P enhances Bcr-Abl1 protein stability, through inhibition of its proteasomal degradation in imatinib-resistant K562/IMA-3 and LAMA-4/IMA human CML cells. In fact, Bcr-Abl1 stability was enhanced by ectopic SK-1 expression. Conversely, siRNA-mediated SK-1 knockdown in K562/IMA-3 cells, or its genetic loss in SK-1(-/-) MEFs, significantly reduced Bcr-Abl1 stability. Regulation of Bcr-Abl1 by SK-1/S1P was dependent on S1P receptor 2 (S1P2) signaling, which prevented Bcr-Abl1 dephosphorylation, and degradation via inhibition of PP2A. Molecular or pharmacologic interference with SK-1/S1P2 restored PP2A-dependent Bcr-Abl1 dephosphorylation, and enhanced imatinib- or nilotinib-induced growth inhibition in primary CD34(+) mononuclear cells obtained from chronic phase and blast crisis CML patients, K562/IMA-3 or LAMA4/IMA cells, and 32Dcl3 murine progenitor cells, expressing the wild-type or mutant (Y253H or T315I) Bcr-Abl1 in situ. Accordingly, impaired SK-1/S1P2 signaling enhanced the growth-inhibitory effects of nilotinib against 32D/T315I-Bcr-Abl1-derived mouse allografts. Since SK-1/S1P/S1P2 signaling regulates Bcr-Abl1 stability via modulation of PP2A, inhibition of SK-1/S1P2 axis represents a novel approach to target wild-type- or mutant-Bcr-Abl1 thereby overcoming drug resistance.

MeSH terms

  • Animals
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology
  • Benzamides
  • Cell Line, Tumor
  • Drug Resistance, Neoplasm*
  • Fusion Proteins, bcr-abl / chemistry*
  • Fusion Proteins, bcr-abl / genetics
  • Fusion Proteins, bcr-abl / metabolism
  • Humans
  • Imatinib Mesylate
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / drug therapy
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / metabolism*
  • Leukemia, Myelogenous, Chronic, BCR-ABL Positive / pathology
  • Lysophospholipids / metabolism*
  • Mice
  • Mice, SCID
  • Phosphorylation / drug effects
  • Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors
  • Phosphotransferases (Alcohol Group Acceptor) / genetics
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Piperazines / administration & dosage
  • Protein Phosphatase 2 / genetics
  • Protein Phosphatase 2 / metabolism*
  • Pyrimidines / administration & dosage
  • RNA, Small Interfering / genetics
  • Receptors, Lysosphingolipid / genetics
  • Receptors, Lysosphingolipid / metabolism*
  • Signal Transduction
  • Sphingosine / analogs & derivatives*
  • Sphingosine / metabolism
  • Ubiquitination

Substances

  • 4-methyl-N-(3-(4-methylimidazol-1-yl)-5-(trifluoromethyl)phenyl)-3-((4-pyridin-3-ylpyrimidin-2-yl)amino)benzamide
  • Benzamides
  • Lysophospholipids
  • Piperazines
  • Pyrimidines
  • RNA, Small Interfering
  • Receptors, Lysosphingolipid
  • sphingosine 1-phosphate
  • Imatinib Mesylate
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • Fusion Proteins, bcr-abl
  • Protein Phosphatase 2
  • Sphingosine