Epigenetic regulation of the taxol resistance-associated gene TRAG-3 in human tumors

Cancer Genet Cytogenet. 2004 May;151(1):1-13. doi: 10.1016/j.cancergencyto.2003.08.021.


TRAG-3, originally identified as a taxol resistance-associated gene from an ovarian carcinoma cell line, is upregulated in many human tumors. Like many tumor antigens, TRAG-3 mRNA is not detectable or is expressed at very low levels in normal fetal and adult human tissues except for testis, where TRAG-3 mRNA transcripts are detected abundantly. TRAG-3 mRNA is frequently overexpressed in tumors but is rarely detected in adjacent normal tissues. To delineate the transcriptional regulation of this tumor antigen, we cloned and sequenced the TRAG-3 promoter. A 539-base pair fragment upstream of the initiation site, which contains two unusual CT repeat stretches, was sufficient to drive the maximum activity of a luciferase reporter gene. Sodium bisulfite sequencing of genomic DNA revealed that the amount of DNA methylation in exon 2 and in the promoter regions is inversely correlated with gene expression. In normal tissues, TRAG-3 is hypermethylated and is thus transcriptionally silenced. In those tumors where TRAG-3 is actively transcribed, the TRAG-3 promoter and exon 2 are hypomethylated. Treatment of a TRAG-3-silenced cell line H23 with the demethylating reagent 5-aza-cytosine reduced DNA methylation and induced TRAG-3 expression in a dose-dependent manner. These results indicate that DNA demethylation is an important epigenetic mechanism that regulates the TRAG-3 tumor antigen in human tumors.

Publication types

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

MeSH terms

  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Base Sequence
  • Cell Line, Tumor
  • Cytosine / analogs & derivatives*
  • Cytosine / pharmacology
  • DNA Methylation
  • DNA Primers
  • Drug Resistance, Neoplasm / genetics*
  • Epigenesis, Genetic*
  • Gene Expression Regulation, Neoplastic*
  • Gene Silencing
  • Humans
  • Neoplasm Proteins / genetics*
  • Paclitaxel / pharmacology*
  • Promoter Regions, Genetic
  • RNA, Messenger / genetics


  • Antineoplastic Agents, Phytogenic
  • CSAG2 protein, human
  • DNA Primers
  • Neoplasm Proteins
  • RNA, Messenger
  • 5-azacytosine
  • Cytosine
  • Paclitaxel