Inhibition of cell proliferation, induction of apoptosis, reactivation of DLC1, and modulation of other gene expression by dietary flavone in breast cancer cell lines.
BACKGROUND
Dietary flavone was previously shown to increase the expression of deleted in liver cancer-1 gene (DLC-1) in HT-29 colon carcinoma cell line [Herzog A, Kindermann B, Doring F, Daniel H, Wenzel U. Pleiotropic molecular effects of the pro-apoptotic dietary constituent flavone in human colon cancer cells identified by protein and mRNA expression profiling. Proteomics 2004;4:2455-64]. DLC-1 that encodes a Rho GTPase-activating protein, functions as a tumor suppressor gene and is frequently inactivated or down-regulated in several common cancers. Restoration of DLC-1 expression suppresses in vitro tumor cells proliferation and tumorigenicity in vivo.


METHODS
Here, the effect of flavone was examined in several DLC-1-deficient cell lines derived from different types human cancer using assays for cell proliferation, gene expression and transfer.


RESULTS
We show that exposure to 150 microM flavone increased DLC1 expression in breast but not in liver or prostate carcinoma cells or a nonmalignant breast epithelial cell line. Flavone restored the expression of DLC1 in the breast carcinoma cell lines MDA-MB-468, MDA-MB-361, and BT20 as well as in the colon carcinoma cell line HT-29 all of which are DLC-1-negative due to promoter hypermethylation. We further show that flavone inhibited cell proliferation, induced cell cycle arrest at G(2)-M, increased p21(Waf1) gene expression, and caused apoptosis. Microarray analysis of these aggressive and metastatic breast carcinoma cells revealed 29 flavone-responsive genes, among which the DNA damage-inducible GADD genes were up-regulated and the proto-oncogene STMN1 and IGFBP3 were down-regulated.


CONCLUSIONS
Flavone-mediated alterations of genes that regulate tumor cell proliferation, cell cycle, and apoptosis contribute to chemopreventive and antitumoral effects of flavone. Alone or in combination with demethylating agents, flavone may be an effective adjunct to chemotherapy in preventing breast cancer metastasis.
Ullmannova
Veronika
V
Laboratory of Experimental Carcinogenesis, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, MSC 4264, Bethesda, MD 20892-4255, USA.
Popescu
Nicholas C
NC
D017209:Apoptosis / Q000187:drug effects*; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology*; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle; D049109:Cell Proliferation / Q000187:drug effects*; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D019175:DNA Methylation; D005260:Female; D047309:Flavones / Q000494:pharmacology*; D005434:Flow Cytometry; D020690:GTPase-Activating Proteins; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D016147:Genes, Tumor Suppressor; D006801:Humans; D015151:Immunoblotting; D008297:Male; D020411:Oligonucleotide Array Sequence Analysis; D000090063:Proto-Oncogene Mas; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins / Q000235:genetics* / Q000378:metabolism
D014408:Biomarkers, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21; C112352:DLC1 protein, human; D047309:Flavones; D020690:GTPase-Activating Proteins; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D025521:Tumor Suppressor Proteins; D053148:Caspase 3