RARα2 expression confers myeloma stem cell features

Blood. 2013 Aug 22;122(8):1437-47. doi: 10.1182/blood-2013-02-482919. Epub 2013 Jul 11.

Abstract

We previously demonstrated that RARα2 expression is increased in CD138 selected plasma cells of relapsed multiple myelomas (MMs), and increased expression was linked to poor prognosis in newly diagnosed MM patients. In the present study, we demonstrate that increased RARα2 confers myeloma stem cell features. Higher expression of RARα2 was identified in the multiple myeloma stem cell (MMSC) fraction. Overexpression of RARα2 in bulk MM cell lines resulted in: 1) increased drug resistance; 2) increased clonogenic potential; 3) activation of both Wnt and Hedgehog (Hh) pathways; 4) increased side population and aldehyde dehydrogenase levels; and 5) increased expression of embryonic stem cell genes. The opposite effects were seen with RARα2 knockdown. We demonstrate that RARα2 induces drug resistance by activating the drug efflux pump gene ABCC3 and anti-apoptotic Bcl-2 family members. Inhibition of Wnt signaling or ABCC3 function could overcome drug resistance in RARα2 overexpressing MM cells. We also showed that in the 5TGM1 mouse model, targeting of the Wnt and Hh pathways using CAY10404, cyclopamine, or itraconazole significantly reduced the myeloma tumor burden and increased survival. Targeting RARα2 or its downstream signaling pathways provides a potential strategy to eliminate MMSC.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cell Survival
  • Gene Expression Profiling
  • Gene Expression Regulation, Neoplastic*
  • Hedgehog Proteins / metabolism
  • Humans
  • Isoxazoles / pharmacology
  • Itraconazole / pharmacology
  • Mice
  • Multidrug Resistance-Associated Proteins / metabolism
  • Multiple Myeloma / metabolism*
  • Neoplastic Stem Cells / cytology*
  • Plasma Cells / metabolism
  • Prognosis
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Receptors, Retinoic Acid / metabolism*
  • Retinoic Acid Receptor alpha
  • Signal Transduction
  • Sulfones / pharmacology
  • Syndecan-1 / metabolism
  • Veratrum Alkaloids / pharmacology
  • Wnt Proteins / metabolism

Substances

  • 3-(4-methylsulfonylphenyl)-4-phenyl-5-trifluoromethylisoxazole
  • Hedgehog Proteins
  • Isoxazoles
  • Multidrug Resistance-Associated Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RARA protein, human
  • Rara protein, mouse
  • Receptors, Retinoic Acid
  • Retinoic Acid Receptor alpha
  • Sulfones
  • Syndecan-1
  • Veratrum Alkaloids
  • Wnt Proteins
  • multidrug resistance-associated protein 3
  • Itraconazole
  • cyclopamine