Mechanisms of the growth inhibitory effects of the isoflavonoid biochanin A on LNCaP cells and xenografts.
BACKGROUND
Isoflavones inhibit the growth of some types of tumor cells, including prostate adenocarcinoma. This study used LNCaP cells and xenografts to investigate the mechanisms of the antiproliferative effects of biochanin A, a major isoflavone present in red clover but not soy-derived products.


METHODS
LNCaP cells were exposed to varying doses of biochanin A to evaluate viability, DNA synthesis, and DNA fragmentation (TUNEL) analysis. Regulation of gene expression was determined by using Western immunoblotting and cDNA microarrays. Anti-tumorigenic effects were evaluated by using athymic mice with LNCaP flank tumors.


RESULTS
Biochanin A induced a dose-dependent inhibition of proliferation and [(3)H]thymidine incorporation that correlated with increased DNA fragmentation, indicative of apoptosis. Western blot analyses of cell cycle regulatory proteins revealed that biochanin A significantly decreased expression of cyclin B and p21, whereas flow cytometry showed that cells were accumulating in the G(0)/G(1) phase. cDNA microarray analyses identified 29 down-regulated genes with six reduced below assay detection limits. Eleven genes were up-regulated, including 9 that were undetectable in controls. In mice with LNCaP xenografts, biochanin A significantly reduced tumor size and incidence.


CONCLUSIONS
These results indicate that biochanin A inhibits prostate cancer cell growth through induction of cell cycle arrest and apoptosis. Biochanin A-regulated genes suggest multiple pathways of action. Biochanin A inhibits the incidence and growth of LNCaP xenograft tumors in athymic mice.
Department of Surgery, Division of Urology, University of Florida, College of Medicine, Gainesville, Florida 32610, USA.
Lori
L
Rice
Von G
VG
Samedi
Theresa A
TA
Medrano
Carol A
CA
Sweeney
Henry V
HV
Baker
Anne
A
Stenstrom
Jaime
J
Furman
Kathleen T
KT
Shiverick
D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D018797:Cell Cycle Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D018076:DNA, Complementary / Q000235:genetics; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D020411:Oligonucleotide Array Sequence Analysis; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology* / Q000517:prevention & control; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D016588:Anticarcinogenic Agents; D018797:Cell Cycle Proteins; D018076:DNA, Complementary; D019833:Genistein; C004541:biochanin A