Hypermethylation of a Small CpGuanine-Rich Region Correlates with Loss of Activator Protein-2α Expression during Progression of Breast Cancer

Donna B. Douglas, Yoshimitsu Akiyama, Hetty Carraway, Steven A. Belinsky, Manel Esteller, Edward Gabrielson, Sigmund Weitzman, Trevor Williams, James G. Herman, Stephen B. Baylin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Scopus citations

Abstract

The transcription factor activator protein-2α (AP-2α) has recently been implicated as a tumor suppressor protein that can be lost during tumor progression and that exhibits growth-inhibitory properties when overexpressed in cancer cell lines. We now demonstrate that hypermethylation of a discrete 5′ region within a promoter CpG island of the gene is associated in breast cancer with the loss of AP-2α expression. Multiple CpG sites within the island become hypermethylated during breast cancer evolution. However, only hypermethylation of the most CpG-rich region, a small, ∼300-bp area at the 3′ end of exon 1, fully distinguishes neoplastic from normal breast tissue and correlates with transcriptional silencing. In cell culture, silenced AP-2α, associated with exon 1 hypermethylation, is re-expressed by 5-aza-2′deoxycytidine resulting in the restoration of a functional DNA sequence-specific binding protein. In vivo, as detected by a very sensitive nested PCR approach, methylation of the discrete AP-2α exon 1 region does not occur in normal breast epithelium and occurs in only 3 (16%) of 19 ductal carcinoma in situ (DCIS) lesions, but is present in 12 (75%) of 16 invasive breast tumors (P < 0.001; DCIS versus invasive cancers). Tumors unmethylated for this region expressed AP-2α protein throughout, whereas tumors with hypermethylation showed large areas of loss. Our studies then determine that hypermethylation of a small region of a CpG island correlates with silencing of AP-2α in breast cancer and suggest that inactivation of this gene could be a factor in, and a useful marker for, the progression of DCIS lesions.

Original languageEnglish (US)
Pages (from-to)1611-1620
Number of pages10
JournalCancer Research
Volume64
Issue number5
DOIs
StatePublished - Mar 1 2004

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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