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ZNF703 overexpression and/or knockdown in the breast cancer cell line MCF-7

ABSTRACT: The telomeric amplicon at 8p12 is common in ER+ breast cancers. Array-CGH and expression analyses of 1172 tumors revealed ZNF703/Zeppo1 was the single gene within the minimal amplicon and was amplified predominantly in the Luminal B subtype. Amplification was shown to correlate with increased gene and protein expression and was associated with a distinct expression signature and poor outcome. In the luminal MCF-7 cell line manipulation of ZNF703 expression altered transcription of genes also present within the primary tumor signature, including TGFBR2 (whose promoter was bound by ZNF703). Overexpression of ZNF703 rendered MCF-7 cells insensitive to TGFβ-induced suppression of mammosphere formation. Forced overexpression of ZNF703 in normal human breast epithelial cells enhanced the frequency of in vitro colony-forming cells from luminal progenitors. Together these data strongly point to ZNF703/Zeppo1 as a novel oncogene in Luminal B breast cancer. MCF-7 breast cancer cell line was infected with ZNF703 overexpression (ZNF703) or control (HIV) virus and following GFP sorting of infected cells, were transfected with control siRNA (siC) or siRNA against endogenous ZNF703 (siZNF), resulting in four different conditions: siC_HIV, siC_ZNF, siZNF_HIV and siZNF-ZNF. RNA for each condition was harvested from triplicate plates.

ORGANISM(S): Homo sapiens

SUBMITTER: Holland DG

PROVIDER: S-ECPF-GEOD-23673 | biostudies-other | 2011 Mar

REPOSITORIES: biostudies-other

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Project description:BackgroundOverexpression the KCNJ3, a gene that encodes subunit 1 of G-protein activated inwardly rectifying K(+) channel (GIRK1) in the primary tumor has been found to be associated with reduced survival times and increased lymph node metastasis in breast cancer patients.MethodsIn order to survey possible tumorigenic properties of GIRK1 overexpression, a range of malignant mammary epithelial cells, based on the MCF-7 cell line that permanently overexpress different splice variants of the KCNJ3 gene (GIRK1a, GIRK1c, GIRK1d and as a control, eYFP) were produced. Subsequently, selected cardinal neoplasia associated cellular parameters were assessed and compared.ResultsAdhesion to fibronectin coated surface as well as cell proliferation remained unaffected. Other vital parameters intimately linked to malignancy, i.e. wound healing, chemoinvasion, cellular velocities / motilities and angiogenesis were massively affected by GIRK1 overexpression. Overexpression of different GIRK1 splice variants exerted differential actions. While GIRK1a and GIRK1c overexpression reinforced the affected parameters towards malignancy, overexpression of GIRK1d resulted in the opposite. Single channel recording using the patch clamp technique revealed functional GIRK channels in the plasma membrane of MCF-7 cells albeit at very low frequency.DiscussionWe conclude that GIRK1d acts as a dominant negative constituent of functional GIRK complexes present in the plasma membrane of MCF-7 cells, while overexpression of GIRK1a and GIRK1c augmented their activity. The core component responsible for the cancerogenic action of GIRK1 is apparently presented by a segment comprising aminoacids 235-402, that is present exclusively in GIRK1a and GIRK1c, but not GIRK1d (positions according to GIRK1a primary structure).ConclusionsThe current study provides insight into the cellular and molecular consequences of KCNJ3 overexpression in breast cancer cells and the mechanism upon clinical outcome in patients suffering from breast cancer.

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ZNF703 overexpression and/or knockdown in the breast cancer cell line MCF-7

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