bcl-2 over-expression enhances NF-κB activity and induces mmp-9 transcription in human MCF7ADR breast-cancer cells
✍ Scribed by Alfredo Ricca; Annamaria Biroccio; Donatella Del Bufalo; Andrew R. Mackay; Angela Santoni; Marco Cippitelli
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- French
- Weight
- 204 KB
- Volume
- 86
- Category
- Article
- ISSN
- 0020-7136
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✦ Synopsis
bcl-2 expression is often associated with poor prognosis in several types of tumors; however, the role of this molecule in breast cancer is still controversial. We found earlier that over-expression of bcl-2 in a human breast-cancer cell line (MCF7 ADR ) enhances its tumorigenicity and metastatic potential by inducing metastasis-associated properties such as increased secretion of the matrix metalloproteinase-9 (mmp-9). In the present study, we investigated the effect of bcl-2 over-expression on the activity of the transcription factor NF-B, an important regulator of genes involved in tumor progression and invasion. Transient transfection experiments indicate that over-expression of bcl-2 in the MCF7 ADR cell line, enhances NF-B-dependent transcriptional activity. Mobility-shift analysis revealed an increase of NF-B DNAbinding in bcl-2-over-expressing clones that correlated with lower levels of the NF-B cytoplasmic inhibitor IB␣. Moreover, point mutations of 2 highly conserved residues within the BH1 and BH2 domains that abrogate the interaction of bcl-2 with bax, or deletion of the N-terminal BH4 domain, completely eliminate the ability of this molecule to up-regulate NF-B-dependent transactivation. Since mmp-9 is a NF-B-regulated gene, we also investigated whether bcl-2 overexpression up-regulated mmp-9 transcription. We found that induction of mmp-9 mRNA correlates with the activation of an mmp-9-promoter-reporter-gene construct in transient transfection assay, and a mutation of the (؊600)mmp-9-NF-B binding element abolishes this effect. The overall data indicate that bcl-2-mediated regulation of NF-B-transcription-factor activity may represent an important mechanism for the promotion of malignant behavior in MCF-7 ADR cells.