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Treatment May Speed Prostate Cancer
Aug. 28, 2008 -- Hormone therapy, the most common treatment for advanced prostate cancer, can boomerang to make the cancer more deadly, mouse studies suggest.
The finding "may revolutionize the way we combat prostate cancer," suggest University of Rochester researchers Chawnshang Chang, PhD, Edward M. Messing, MD, and colleagues.
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It's well known that male sex hormones promote the growth of prostate cancer. That's why doctors use hormone therapy -- chemical or physical castration -- to shut off these tumor-promoting androgens.
But Chang's team finds that in different types of prostate cancer cells, androgens actually inhibit prostate cancer. When these tumor cells don't get androgens, they become more aggressive and more invasive.
The lining of the prostate is made up of epithelial cells. The fibrous body of the prostate is made up of stromal cells. On their surfaces, both cell types have triggers -- androgen receptors -- that fire when they encounter sex hormones. Triggering androgen receptors has different effects in each cell type.
"The androgen receptor in the stromal cells always turns the cancer on," Messing tells WebMD. "The androgen receptor in the epithelial cells, at least in the animal models we studied, tends to inhibit cancer."
This, Messing says, helps explain why hormone therapy always works at first but then tends to lose its cancer-inhibiting effect over time.
Since the cancer-promoting effect of androgens is strongest in the earlier stages of cancer, hormone therapy does more good than harm. But as the cancer spreads to distant sites, Messing says, the cancer-inhibiting effect of androgens may become more important. At this point, hormone therapy may do more harm than good.
How can the same hormones have two opposite effects?
"Anyone who has been around teen boys and older men knows that androgen receptors in different parts of the body cause different effects," Messing says. "Androgen receptors on the scalp make older men lose their hair, while androgen receptors on the face make teenagers grow beards. So androgen receptors can do different things in different places."
Doctors have long known that hormone therapy has different effects at different times in different parts of the body, says Peter Nieh, MD, director of the Uro-Oncology Center at Emory University, Atlanta.
"We'd all like to find a silver bullet that attacks one thing but does not hurt anything else. The problem is there is always collateral damage," Nieh tells WebMD.
Chang's team demonstrated the opposite effects of androgen receptors in cell-culture studies and in studies of prostate-cancer-prone mice that lacked androgen receptors only in their prostate epithelial cells. These mice had much more aggressive cancer, apparently because they lost the ability to respond to the cancer-inhibiting effects of androgens.
The researchers also point to studies of prostate glands removed from men with prostate cancer. There were significantly fewer androgen receptors in metastatic prostate cancers than in early prostate cancers or in normal prostate cells.
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Uroxatral® (alfuzosin HCl 10 mg extended-release tablets) is an alpha1-blocker for the treatment of the signs and symptoms of BPH.
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Do not take UROXATRAL if you have liver problems or if you are taking antifungal drugs like ketoconazole or itraconazole, or HIV drugs like ritonavir.
UROXATRAL can cause a sudden drop in blood pressure, especially when starting treatment. This may lead to fainting, dizziness, and lightheadedness. Do not drive, operate machinery, or do any dangerous activity until you know how UROXATRAL will affect you. This is especially important if you already have a problem with low blood pressure or take medicines to treat high blood pressure. There may be an increased risk of low blood pressure and fainting when taking UROXATRAL in combination with blood pressure medication or nitrates, or erectile dysfunction medication.
If considering cataract surgery (clouding of the eyes), tell your eye surgeon that you are currently taking UROXATRAL or have previously been treated with an alpha-blocker.
Before taking UROXATRAL, tell your doctor if you have kidney problems.
Also, tell your doctor if you or any family member(s) have or take medications for a rare heart condition known as congenital prolongation of the QT interval.
BPH and prostate cancer can cause the same symptoms. However, UROXATRAL is not a treatment for prostate cancer.
The most common side effects with UROXATRAL are dizziness, upper respiratory tract infection, headache, and tiredness.
Please see UROXATRAL full prescribing information.
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