t-DARPP regulates phosphatidylinositol-3-kinase-dependent cell growth in breast cancer

Bhavatarini Vangamudi, Dunfa Peng, Qiuyin Cai, Wael El-Rifai, Wei Zheng, Abbes Belkhiri

Research output: Contribution to journalArticle

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Abstract

Background: Recent reports have shown that t-DARPP (truncated isoform of DARPP-32) can mediate trastuzumab resistance in breast cancer cell models. In this study, we evaluated expression of t-DARPP in human primary breast tumors, and investigated the role of t-DARPP in regulating growth and proliferation in breast cancer cells.Results: Quantitative real time RT-PCR analysis using primers specific for t-DARPP demonstrated overexpression of t-DARPP in 36% of breast cancers (13/36) as opposed to absent to very low t-DARPP expression in normal breast tissue (p < 0.05). The mRNA overexpression of t-DARPP was overwhelmingly observed in ductal carcinomas, including invasive ductal carcinomas and intraductal carcinomas, rather than other types of breast cancers. The immunohistochemistry analysis of DARPP-32/t-DARPP protein(s) expression in breast cancer tissue microarray that contained 59 tumors and matched normal tissues when available indicated overexpression in 35.5% of primary breast tumors that were more frequent in invasive ductal carcinomas (43.7%; 21/48). In vitro studies showed that stable overexpression of t-DARPP in MCF-7 cells positively regulated proliferation and anchorage-dependent and -independent growth. Furthermore, this effect was concomitant with induction of phosphorylation of AKTser473 and its downstream target phosphoser9 GSK3β, and increased Cyclin D1 and C-Myc protein levels. The knockdown of endogenous t-DARPP in HCC1569 cells led to a marked decrease in phosphorylation of AKTsser473 and GSK3βser9. The use of PI3K inhibitor LY294002 or Akt siRNA abrogated the t-DARPP-mediated phosphorylation of AKTser473 and led to a significant reduction in cell growth.Conclusions: Our findings underscore the potential role of t-DARPP in regulating cell growth and proliferation through PI3 kinase-dependent mechanism.

Original languageEnglish (US)
Article number240
JournalMolecular Cancer
Volume9
DOIs
StatePublished - Sep 13 2010
Externally publishedYes

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Phosphatidylinositol 3-Kinase
Protein Isoforms
Breast Neoplasms
Growth
Ductal Carcinoma
Phosphorylation
Phosphatidylinositol 3-Kinases
Cyclin C
Dopamine and cAMP-Regulated Phosphoprotein 32
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
Carcinoma, Intraductal, Noninfiltrating
Cyclin D1
MCF-7 Cells
Small Interfering RNA
Real-Time Polymerase Chain Reaction

ASJC Scopus subject areas

  • Molecular Medicine
  • Oncology
  • Cancer Research

Cite this

t-DARPP regulates phosphatidylinositol-3-kinase-dependent cell growth in breast cancer. / Vangamudi, Bhavatarini; Peng, Dunfa; Cai, Qiuyin; El-Rifai, Wael; Zheng, Wei; Belkhiri, Abbes.

In: Molecular Cancer, Vol. 9, 240, 13.09.2010.

Research output: Contribution to journalArticle

Vangamudi, Bhavatarini ; Peng, Dunfa ; Cai, Qiuyin ; El-Rifai, Wael ; Zheng, Wei ; Belkhiri, Abbes. / t-DARPP regulates phosphatidylinositol-3-kinase-dependent cell growth in breast cancer. In: Molecular Cancer. 2010 ; Vol. 9.
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abstract = "Background: Recent reports have shown that t-DARPP (truncated isoform of DARPP-32) can mediate trastuzumab resistance in breast cancer cell models. In this study, we evaluated expression of t-DARPP in human primary breast tumors, and investigated the role of t-DARPP in regulating growth and proliferation in breast cancer cells.Results: Quantitative real time RT-PCR analysis using primers specific for t-DARPP demonstrated overexpression of t-DARPP in 36{\%} of breast cancers (13/36) as opposed to absent to very low t-DARPP expression in normal breast tissue (p < 0.05). The mRNA overexpression of t-DARPP was overwhelmingly observed in ductal carcinomas, including invasive ductal carcinomas and intraductal carcinomas, rather than other types of breast cancers. The immunohistochemistry analysis of DARPP-32/t-DARPP protein(s) expression in breast cancer tissue microarray that contained 59 tumors and matched normal tissues when available indicated overexpression in 35.5{\%} of primary breast tumors that were more frequent in invasive ductal carcinomas (43.7{\%}; 21/48). In vitro studies showed that stable overexpression of t-DARPP in MCF-7 cells positively regulated proliferation and anchorage-dependent and -independent growth. Furthermore, this effect was concomitant with induction of phosphorylation of AKTser473 and its downstream target phosphoser9 GSK3β, and increased Cyclin D1 and C-Myc protein levels. The knockdown of endogenous t-DARPP in HCC1569 cells led to a marked decrease in phosphorylation of AKTsser473 and GSK3βser9. The use of PI3K inhibitor LY294002 or Akt siRNA abrogated the t-DARPP-mediated phosphorylation of AKTser473 and led to a significant reduction in cell growth.Conclusions: Our findings underscore the potential role of t-DARPP in regulating cell growth and proliferation through PI3 kinase-dependent mechanism.",
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AU - Zheng, Wei

AU - Belkhiri, Abbes

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