Multi-gene epigenetic silencing of tumor suppressor genes in T-cell lymphoma cells; delayed expression of the p16 protein upon reversal of the silencing

Leuk Res. 2006 Mar;30(3):303-12. doi: 10.1016/j.leukres.2005.08.012. Epub 2005 Sep 26.

Abstract

To understand better T-cell lymphomagenesis, we examined promoter CpG methylation and mRNA expression of closely related genes encoding p16, p15, and p14 tumor suppressor genes in cultured malignant T-cells that were derived from cutaneous, adult type, and anaplastic lymphoma kinase (ALK)-expressing T-cell lymphomas. p16 gene was epigenetically silenced in all but one of the 10 malignant T-cell lines examined, p15 gene silenced in roughly half of the lines, and p14 was the least frequently affected. Extensive methylation of the p16 promoter was seen in six out of 10 cutaneous T-cell lymphoma patient samples and corresponded with lack of p16 protein expression in the cases examined. Treatment of cultured T-cells with the DNA methyltransferase inhibitor, 5-aza-2-deoxy-cytidine, resulted in reversal of the p16 gene silencing. However, expression of p16 protein was delayed in relationship to p16 promoter demethylation and required up to 3 weeks to occur, seemingly reflecting late activation of the p16 gene. These findings indicate that epigenetic silencing affects in T-cell malignancies, often simultaneously, several tumor suppressor genes that impact on key cell functions. The observed differential silencing of p16 and p14, and to a lesser degree p15 gene, indicates that the silencing is governed by precise, promoter region-specific mechanisms. The study provides also further rationale for treatment of at least some types of T-cell lymphomas with DNA methyltransferase inhibitors to target the epigenetically silenced tumor suppressor genes.

Publication types

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

MeSH terms

  • Adult
  • Anaplastic Lymphoma Kinase
  • Azacitidine / analogs & derivatives
  • Azacitidine / pharmacology
  • Cell Line, Tumor
  • Cyclin-Dependent Kinase Inhibitor p15 / biosynthesis
  • DNA Methylation / drug effects
  • DNA Modification Methylases / antagonists & inhibitors
  • DNA Modification Methylases / metabolism
  • Decitabine
  • Enzyme Inhibitors / pharmacology
  • Epigenesis, Genetic* / drug effects
  • Gene Expression Regulation, Leukemic* / drug effects
  • Gene Silencing* / drug effects
  • Humans
  • Lymphoma, T-Cell, Cutaneous / drug therapy
  • Lymphoma, T-Cell, Cutaneous / metabolism*
  • Lymphoma, T-Cell, Cutaneous / pathology
  • Promoter Regions, Genetic
  • Protein Biosynthesis / drug effects
  • Protein-Tyrosine Kinases / biosynthesis
  • Receptor Protein-Tyrosine Kinases
  • Skin Neoplasms / drug therapy
  • Skin Neoplasms / metabolism*
  • Time Factors
  • Tumor Suppressor Protein p14ARF / biosynthesis*

Substances

  • Cyclin-Dependent Kinase Inhibitor p15
  • Enzyme Inhibitors
  • Tumor Suppressor Protein p14ARF
  • Decitabine
  • DNA Modification Methylases
  • ALK protein, human
  • Anaplastic Lymphoma Kinase
  • Protein-Tyrosine Kinases
  • Receptor Protein-Tyrosine Kinases
  • Azacitidine