BP1 transcriptionally activates bcl-2and inhibits TNFα-induced cell death in MCF7 breast cancer cellsReport as inadecuate




BP1 transcriptionally activates bcl-2and inhibits TNFα-induced cell death in MCF7 breast cancer cells - Download this document for free, or read online. Document in PDF available to download.

Breast Cancer Research

, 9:R60

First Online: 13 September 2007Received: 14 March 2007Revised: 15 August 2007Accepted: 13 September 2007

Abstract

IntroductionWe have previously shown that the Beta Protein 1 BP1 homeodomain protein is expressed in 81% of invasive ductal breast carcinomas, and that increased BP1 expression correlates with tumor progression. The purpose of our current investigation was to determine whether elevated levels of BP1 in breast cancer cells are associated with increased cell survival.

MethodsEffects on cell viability and apoptosis of MCF7 cells stably overexpressing BP1 were determined using MTT and Annexin V assays, and through examination of caspase activation. TNFα was used to induce apoptosis. The potential regulation of apoptosis-associated genes by BP1 was studied using real-time PCR and western blot analyses. Electrophoretic mobility shift assays, site-directed mutagenesis, and transient assays were performed to specifically characterize the interaction of BP1 with the promoter of the bcl-2 gene.

ResultsStable overexpression of BP1 led to inhibition of apoptosis in MCF7 breast cancer cells challenged with TNFα. Increased BP1 resulted in reduced processing and activation of caspase-7, caspase-8, and caspase-9, and inactivation of the caspase substrate PolyADP-Ribose Polymerase PARP. Increased levels of full-length PARP and a decrease in procaspase-8 were also associated with BP1 overexpression. The bcl-2 gene is a direct target of BP1 since: i BP1 protein bound to a consensus binding sequence upstream of the bcl-2 P1 promoter in vitro. ii MCF7 cells overexpressing BP1 showed increased levels of bcl-2 mRNA and protein. iii Transient assays indicated that increased bcl-2 promoter activity is due to direct binding and modulation by BP1 protein. BP1 expression also prevented TNFα-mediated downregulation of bcl-2 mRNA and protein.

ConclusionThese findings suggest mechanisms by which increased BP1 may impart a survival advantage to breast cancer cells, which could lead to increased resistance to therapeutic agents in patients.

Abbreviationsbpbase pairs

BP1Beta Protein 1

FITCFluorescein Isothiocyanate

HPLChigh-performance liquid chromatography

MTTthiazolyl blue tetrazolium bromide

PARPPolyADP-Ribose Polymerase

PCRpolymerase chain reaction

TNFtumor necrosis factor.

Electronic supplementary materialThe online version of this article doi:10.1186-bcr1766 contains supplementary material, which is available to authorized users.

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Author: Holly S Stevenson - Sidney W Fu - Joseph J Pinzone - Jinguen Rheey - Samuel J Simmens - Patricia E Berg

Source: https://link.springer.com/



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