Genistein from Soy Reduces Prostate Cancer Growth in Mice, Cell culture
New York, June 2, 2001 (PSA Rising) -- Genistein, a chemical found in soy, slowed prostate cancer growth in mice and caused prostate cancer cells to die in studies conducted at the UC Davis Cancer Center.
Genistein is one of two compounds in soy that belong to a family of chemicals known as
isoflavones. Isoflavones are phytoestrogens, plant-based chemicals that mimic the effects of
estrogen in the body. Researchers theorize that the prevalence of soy in Asian diets may be one
reason why men in Asia have a lower rate of prostate cancer than men in the United States.
Ralph deVere White, director of the UC Davis Cancer Center and chair of the Department of Urology at the UC Davis Medical Center, will present the results of these studies at the annual meeting of the American Urological Association in Anaheim on June 2-7.
For the UC Davis study, scientists tested a commercially made extract of genistein on mice bred to develop prostate cancer and on metastatic prostate cancer cell lines.
In mice, genistein reduced prostate cancer tumor growth. In tissue culture, genistein increased the production of p21, a gene that regulates cell growth, and
it reduced the production of vascular endothelial growth factor (VEGF), a protein that helps cancer grow. These factors caused cancer cells to die, a process known as apoptosis.
"WeÂve identified the mechanisms by which genistein may work in prostate cancer, and itÂs consistent with other studies of soy," said deVere White. "While we are encouraged by these results, we need to test genistein in patients with prostate cancer to be certain of its effectiveness."
Many prostate cancer patients take over the counter low-dose Genistein as a dietary supplement on the basis of earlier evidence. High concentrations
of genistein, according to a Detroit
team led by Dr. Kenneth Pienta, block PSA
expression in androgen-independent VeCaP cells.
Pienta's team showed that genistein inhibits
cell proliferation independent of PSA signaling
pathways. This, Pienta says, supports "the role of
genistein as a chemopreventive/ therapeutic agent
for prostate cancer irrespective of androgen
responsiveness."
The UC Davis researchers lead by de Vere White are now evaluating the effects of genistein in men who have been diagnosed with slow-growing prostate cancer. The cancer center will ultimately enroll 70 men in the pilot study to see if genistein lowers levels of prostate specific antigen (PSA), a tumor marker for prostate cancer.
Men who have chosen not to receive treatment for prostate cancer or who have undergone treatment and whose PSA levels are rising slowly are eligible to participate in the trial. Volunteers, depending on their body weight, will take up to five grams of genistein daily for six months. Results will be known in a year.
It is unlikely genistein would become a stand-alone treatment for prostate cancer, said deVere White. "But we hope it could be used in conjunction with conventional therapy or as a preventive drug, if it indeed lowers PSA."
LINKS to related reports
Int J Oncol 2000 Jun;16(6):1091-7 Inhibition of
prostate specific antigen expression by genistein in
prostate cancer cells. Davis JN, Muqim N, Bhuiyan
M, Kucuk O, Pienta KJ, Sarkar FH Department of
Cancer Biology, Karmanos Cancer Institute, Wayne
State University, Detroit, MI 48201, USA
E-mail [email protected]
