Drugs Previously Thought to Be Toxic May Stop Spread of
FRIDAY, March 30 (HealthDay News) -- Two drugs previously
thought to be too toxic for human cancer treatment may stop the
growth of cancer cells without killing healthy cells and damaging
DNA when used in small doses, researchers have found.
Unlike conventional chemotherapy drugs, which poison and kill
any rapidly dividing cells by damaging cellular machinery and DNA,
these drugs -- azacitidine (AZA) and decitabine (DAC) --
specifically target cancer stem cells, which cause cancer to spread
and are resistant to most drugs.
"Low doses of AZA and DAC may reactivate genes that stop cancer growth without causing immediate cell killing or DNA damage," Dr. Stephen Baylin, a professor of oncology and deputy director of the Johns Hopkins Kimmel Cancer Center in Baltimore, said in a news release from Hopkins.
Although AZA and DAC were dismissed as too toxic for the
treatment of common cancers, the drugs have been effective in
treating a small number of patients with advanced lung cancer and
myelodysplastic syndrome. Based on those positive clinical
outcomes, the Johns Hopkins researchers decided to re-evaluate the
drugs for use in cancer treatment.
Back in the lab, they treated leukemia, breast cancer, lung
cancer and colon cancer cell lines with low doses of AZA and DAC
for three days. A week later, the treated cells were transplanted
into mice and observed for up to 20 weeks.
The researchers found the anticancer effects of the drugs
continued long after treatment stopped.
After treatment with AZA and DAC, the cancer cells returned to a
more normal state and eventually died, Baylin said.
"Our findings match evidence from recent clinical trials suggesting that the drugs shrink tumors more slowly over time as they repair altered mechanisms in cells and genes return to normal function," Baylin said.
The team noted, however, that more research is needed to
determine exactly how the drugs work.
Clinical trials already have begun among patients in advanced
stages of breast and lung cancer, the researchers said, and trials
in colon cancer patients also are planned.
The researchers noted previous research has shown the drugs
could make other anticancer treatments more effective. The drugs
could become part of a combined treatment approach for certain
cancers, they said.
The findings, which were published recently in the journal
Cancer Cell, are expected to be presented Sunday at a Stand Up to Cancer press event in Chicago.
The U.S. National Cancer Institute provides more information on
cancer stem cells.
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