bcl-2 over-expression enhances NF-kappaB activity and induces mmp-9 transcription in human MCF7(ADR) breast-cancer cells.
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-kappaB, 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-kappaB-dependent transcriptional activity. Mobility-shift analysis revealed an increase of NF-kappaB DNA-binding in bcl-2-over-expressing clones that correlated with lower levels of the NF-kappaB cytoplasmic inhibitor IkappaBalpha. 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-kappaB-dependent transactivation. Since mmp-9 is a NF-kappaB-regulated gene, we also investigated whether bcl-2 over-expression 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-kappaB binding element abolishes this effect. The overall data indicate that bcl-2-mediated regulation of NF-kappaB-transcription-factor activity may represent an important mechanism for the promotion of malignant behavior in MCF-7(ADR) cells.
Ricca
A
A
Experimental Chemotherapy Laboratory, Regina Elena Cancer Institute, Rome, Italy.
Biroccio
A
A
Del Bufalo
D
D
Mackay
A R
AR
Santoni
A
A
Cippitelli
M
M
D001665:Binding Sites; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D015870:Gene Expression; D019254:Genes, bcl-2; D006801:Humans; D020672:I-kappa B Proteins; D020780:Matrix Metalloproteinase 9 / Q000235:genetics*; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017354:Point Mutation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D000072000:NF-KappaB Inhibitor alpha; D004247:DNA; D020780:Matrix Metalloproteinase 9