Darpp-32

A novel antiapoptotic gene in upper gastrointestinal carcinomas

Abbes Belkhiri, Alexander Zaika, Nataliya Pidkovka, Sakari Knuutila, Christopher Moskaluk, Wael El-Rifai

Research output: Contribution to journalArticle

51 Citations (Scopus)

Abstract

We show the molecular mechanisms involved in Darpp-32 overexpression and its biological role in upper gastrointestinal adenocarcinomas (UGC). A tumor tissue array of 377 samples was developed and used to detect DARPP-32 DNA amplification and protein overexpression, which occurred in 32% and 60% of UGCs, respectively. Concomitant overexpression of mRNA for Darpp-32 and its truncated isoform t-Darpp was observed in 68% of tumors (P < 0.001). When Darpp-32 and t-Darpp were overexpressed in AGS and RKO gastrointestinal cells, up to a 4-fold reduction in the apoptosis rate was observed (terminal deoxynucleotidyl transferase-mediated nick-end labeling and Annexin V assays) in response to camptothecin, sodium butyrate, and ceramide. However, the introduction of mutations in phosphorylation sites abrogated this effect. Expression of Darpp-32 and t-Darpp preserved the mitochondrial transmembrane potential and was associated with increased levels of Bcl2 protein. A reversal of Bcl2 protein level was obtained using small interfering RNAs for Darpp-32 and t-Darpp. Luciferase assays using the p53 and p21 reporter plasmids and probing of immunoblots with antibodies specific for p53 transcriptional targets, such as Hdm2 and p21, indicated that neither Darpp-32 nor t-Darpp interfere with p53 function. Altogether, we show more frequent mRNA and protein overexpression of Darpp-32 than DNA amplification, suggesting that, in addition to amplification, transcriptional or posttranscriptional mechanisms may play an important role. The expression of Darpp-32 and t-Darpp is associated with a potent antiapoptotic advantage for cancer cells through a p53-independent mechanism that involves preservation of mitochondrial potential and increased Bcl2 levels.

Original languageEnglish (US)
Pages (from-to)6583-6592
Number of pages10
JournalCancer Research
Volume65
Issue number15
DOIs
StatePublished - Aug 1 2005
Externally publishedYes

Fingerprint

Carcinoma
Genes
Proteins
Camptothecin
Neoplasms
Messenger RNA
Butyric Acid
DNA Nucleotidylexotransferase
Ceramides
Annexin A5
DNA
Luciferases
Membrane Potentials
Small Interfering RNA
Protein Isoforms
Adenocarcinoma
Plasmids
Phosphorylation
Apoptosis
Mutation

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

Cite this

Darpp-32 : A novel antiapoptotic gene in upper gastrointestinal carcinomas. / Belkhiri, Abbes; Zaika, Alexander; Pidkovka, Nataliya; Knuutila, Sakari; Moskaluk, Christopher; El-Rifai, Wael.

In: Cancer Research, Vol. 65, No. 15, 01.08.2005, p. 6583-6592.

Research output: Contribution to journalArticle

Belkhiri, Abbes ; Zaika, Alexander ; Pidkovka, Nataliya ; Knuutila, Sakari ; Moskaluk, Christopher ; El-Rifai, Wael. / Darpp-32 : A novel antiapoptotic gene in upper gastrointestinal carcinomas. In: Cancer Research. 2005 ; Vol. 65, No. 15. pp. 6583-6592.
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