Retinoic acid receptor β enhanced the anti-cancer stem cells effect of β-carotene by down-regulating expression of delta-like 1 homologue in human neuroblastoma cells

Biochem Biophys Res Commun. 2016 Nov 11;480(2):254-260. doi: 10.1016/j.bbrc.2016.10.041. Epub 2016 Oct 15.


Neuroblastoma (NB) is childhood malignancy that retains characteristics of cancer stem cells (CSCs). Targeting the CSCs is one of the therapeutic strategies proposed to achieve complete remission of NB. β-carotene (BC), an active precursor of retinoids, is a well-known antioxidant reported to possess anti-CSCs effects. Here, we investigated the involvement of retinoic acid receptors (RARs) in the anti-CSCs effects of BC. Treatment with BC or retinoic acid (RA) upregulated RARβ mRNA expression in two NB cell lines. Inhibition of RARβ using siRNA up-regulated gene expression of delta-like 1 homologue (DLK1), a marker of CSCs. To understand the molecular mechanisms of RARβ-mediated inhibition of DLK1, four retinoic acid receptor elements (RAREs) were identified in the promoter of DLK1. Chromatin immunoprecipitation assays indicated that RARβ bound directly to a RARE in the DLK1 promoter region. Knock-down of RARβ also increased the self-renewal capacity of NB cells, which was suppressed by BC. Taken together, this study provided evidence that the therapeutic anti-CSC effects of BC depend on RARβ and its ability to interact with and down-regulate the CSCs marker, DLK1.

Keywords: Cancer stem cells; DLK1; Neuroblastoma; Retinoic acid β; β-carotene.

MeSH terms

  • Antineoplastic Agents, Phytogenic / pharmacology
  • Calcium-Binding Proteins
  • Cell Line, Tumor
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Intercellular Signaling Peptides and Proteins / genetics
  • Intercellular Signaling Peptides and Proteins / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Neoplastic Stem Cells / drug effects*
  • Neoplastic Stem Cells / pathology
  • Neuroblastoma / drug therapy*
  • Neuroblastoma / metabolism
  • Neuroblastoma / pathology
  • Promoter Regions, Genetic
  • Receptors, Retinoic Acid / metabolism*
  • beta Carotene / pharmacology*


  • Antineoplastic Agents, Phytogenic
  • Calcium-Binding Proteins
  • DLK1 protein, human
  • Intercellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Receptors, Retinoic Acid
  • retinoic acid receptor beta
  • beta Carotene