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Int J Cancer. 2000 Aug 15;87(4):582-90.

Bcl-xl antisense treatment induces apoptosis in breast carcinoma cells.

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Division of Oncology, Department of Internal Medicine, University Hospital Zurich, Zurich, Switzerland.


Upregulated expression of bcl-xL is involved in the initiation and progression of breast cancer by inhibiting tumor cell apoptosis. Here we describe the use of the 2;-O-methoxy-ethoxy antisense oligonucleotide 4259 targeting nucleotides 687-706 of the bcl-xL mRNA, a sequence that does not occur in the pro-apoptotic bcl-xS transcript, to restore apoptosis in estrogen-dependent and independent breast carcinoma cells. The antisense effect of oligonucleotide 4259 was examined on the mRNA and protein level using real-time PCR and Western blot analysis, respectively, and the induction of cell death was investigated in viability and apoptosis assays. Treatment of MCF7 cells with oligonucleotide 4259 at a concentration of 600 nM for 20 hr decreased bcl-xL mRNA and protein levels by more than 80% and 50%, respectively. This resulted in the induction of apoptosis characterized by mitochondrial cytochrome c release, decrease of mitochondrial transmembrane potential, and the appearance of condensed nuclei in approximately 40% of cells. Moreover, oligonucleotide 4259 efficiently downregulated bcl-xL expression and decreased cell growth in the breast carcinoma cell lines T-47D, ZR-75-1, and MDA-MB-231. Our data emphasize the importance of bcl-xL as a survival factor for breast carcinoma cells and suggest that oligonucleotide 4259 deserves further investigations for use in breast cancer therapy.

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