Epigenetic regulation by decitabine of melanoma differentiation in vitro and in vivo

Int J Cancer. 2012 Jul 1;131(1):18-29. doi: 10.1002/ijc.26320. Epub 2011 Sep 6.


Apoptosis genes, such as TP53 and p16/CDKN2A, that mediate responses to cytotoxic chemotherapy, are frequently nonfunctional in melanoma. Differentiation may be an alternative to apoptosis for inducing melanoma cell cycle exit. Epigenetic mechanisms regulate differentiation, and DNA methylation alterations are associated with the abnormal differentiation of melanoma cells. The effects of the deoxycytidine analogue decitabine (5-aza-2'-deoxycytidine), which depletes DNA methyl transferase 1 (DNMT1), on melanoma differentiation were examined. Treatment of human and murine melanoma cells in vitro with concentrations of decitabine that did not cause apoptosis inhibited proliferation accompanied by cellular differentiation. A decrease in promoter methylation, and increase in expression of the melanocyte late-differentiation driver SOX9, was followed by increases in cyclin-dependent kinase inhibitors (CDKN) p27/CDKN1B and p21/CDKN1A that mediate cell cycle exit with differentiation. Effects were independent of the TP53, p16/CDKN2A and also the BRAF status of the melanoma cells. Resistance, when observed, was pharmacologic, characterized by diminished ability of decitabine to deplete DNMT1. Treatment of murine melanoma models in vivo with intermittent, low-dose decitabine, administered sub-cutaneously to limit high peak drug levels that cause cytotoxicity and increase exposure time for DNMT1 depletion, and with tetrahydrouridine to decrease decitabine metabolism and further increase exposure time, inhibited tumor growth and increased molecular and tumor stromal factors implicated in melanocyte differentiation. Modification of decitabine dose, schedule and formulation for differentiation rather than cytotoxic objectives inhibits the growth of melanoma cells in vitro and in vivo.

Publication types

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

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic / pharmacology*
  • Apoptosis
  • Azacitidine / administration & dosage
  • Azacitidine / analogs & derivatives*
  • Azacitidine / pharmacology
  • Base Sequence
  • Cell Differentiation / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cyclin-Dependent Kinase Inhibitor Proteins / biosynthesis
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism
  • DNA (Cytosine-5-)-Methyltransferase 1
  • DNA (Cytosine-5-)-Methyltransferases / analysis
  • DNA (Cytosine-5-)-Methyltransferases / metabolism*
  • DNA Methylation
  • Decitabine
  • Epigenesis, Genetic*
  • Female
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Male
  • Melanoma, Experimental / drug therapy*
  • Melanoma, Experimental / genetics
  • Melanoma, Experimental / metabolism
  • Melanoma, Experimental / pathology
  • Mice
  • Mice, Inbred C57BL
  • Mice, Nude
  • Promoter Regions, Genetic / genetics
  • Proto-Oncogene Proteins B-raf / biosynthesis
  • SOX9 Transcription Factor / biosynthesis
  • Sequence Analysis, DNA
  • Tetrahydrouridine / pharmacology
  • Tumor Suppressor Protein p53 / metabolism
  • Up-Regulation


  • Antimetabolites, Antineoplastic
  • Cyclin-Dependent Kinase Inhibitor Proteins
  • Cyclin-Dependent Kinase Inhibitor p16
  • SOX9 Transcription Factor
  • Sox9 protein, mouse
  • Tumor Suppressor Protein p53
  • Tetrahydrouridine
  • Decitabine
  • DNA (Cytosine-5-)-Methyltransferase 1
  • DNA (Cytosine-5-)-Methyltransferases
  • DNMT1 protein, human
  • Dnmt1 protein, mouse
  • Braf protein, mouse
  • Proto-Oncogene Proteins B-raf
  • Azacitidine