Characterization of Δnp73 expression and regulation in gastric and esophageal tumors

A. E. Vilgelm, S. M. Hong, M. K. Washington, J. Wei, H. Chen, W. El-Rifai, A. Zaika

Research output: Contribution to journalArticle

20 Scopus citations

Abstract

p73 is a member of the p53 protein family. Although the tumor suppressor function of p53 is clearly defined, the role of p73 in tumorigenesis is still a matter of debate. A complex pattern of expression of p73 isoforms makes it difficult to unambiguously interpret the experimental results. Previously, we along with others have found that the N-terminally truncated isoform of p73, ΔNp73, has potent anti-apoptotic and oncogenic properties in vitro and in vivo. In this study, we analyzed, for the first time, the regulation of ΔNp73 in a large number of gastric, gastroesophageal junction and esophageal tumors. We found that expression of ΔNp73 mRNA and protein is increased in these neoplasms. Furthermore, the upregulation of the ΔNp73 protein is significantly associated with poor patient survival. Oncogenic properties of ΔNp73 were further confirmed by finding that ΔNp73 facilitates anchorage-independent growth of gastric epithelial cells in soft agar. As little is currently known about the regulation of ΔNp73 transcription, we investigated the alternative p73 gene promoter that mediates the ΔNp73 expression. Analyzing the ΔNp73 promoter in silico as well as by using chromatin immunoprecipitation, site-directed mutagenesis and deletion analyses, we identified the evolutionary conserved region within the ΔNp73 promoter that contains binding sites for HIC1 (hypermethylated in cancer) protein. We found that HIC1 negatively regulates ΔNp73 transcription in mucosal epithelial cells. This leads to a decrease in ΔNp73 protein levels and may normally control the oncogenic potential of the ΔNp73 isoform.

Original languageEnglish (US)
Pages (from-to)5861-5868
Number of pages8
JournalOncogene
Volume29
Issue number43
DOIs
StatePublished - Oct 28 2010
Externally publishedYes

Keywords

  • esophageal tumor
  • gastric tumor
  • p73

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Cancer Research

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