TUESDAY, June 3 (HealthDay News) -- U.S. researchers have
uncovered new information about how metastatic prostate cancer
becomes resistant to androgen-deprivation therapy, which suppresses
circulating testosterone, the hormone that promotes prostate cancer
growth.
Androgen therapy, which involves the use of surgical castration
or medical castration with testosterone-blocking drugs, does extend
survival time for patients, but it isn't a cure. Eventually, the
cancer becomes resistant to androgen deprivation and continues to
grow.
"We found that despite the suppression of circulating androgen
levels to very low or castrate levels, metastatic prostate tumors
are themselves able to maintain significant levels of testosterone,
which fuels the growth of the cancer," Dr. Elahe Mostaghel, a
clinical research association at Seattle's Fred Hutchinson Cancer
Research Center, said in a prepared statement.
Mostaghel and colleagues found that testosterone levels in
metastatic prostate tumors (cancer that's spread from the prostate
to other parts of the body) from castrate men who'd just died were
four times higher than in benign and cancerous prostate tissue in
men with normal circulating androgen levels.
They also discovered that metastatic prostate tumor tissue
contains the genetic information needed to make the proteins that
produce testosterone and other androgen hormones.
"We not only found that metastatic tumor tissues have high
enough androgen levels within them to support continued growth of
the tumor cells, but also a critically important reason behind why
those androgens are there -- the discovery that the gene pathways
for synthesizing androgens from cholesterol appear to be present in
the distant tumor sites. This finding will allow us to start honing
in on the specific source of those androgens and how we can
eliminate them," Mostaghel said.
"As we develop new drug targets, we will need to focus on
enzymes that seem to be active in the tumor itself. This offers a
new way of looking at hormone suppression. In addition to systemic
suppression, it suggests we also need to target hormone suppression
much more specifically, inside the tumor itself."
The study was published in the June 1 issue of
Cancer Research.
More information
The National Cancer Institute has more about
prostate cancer treatment.
