foodconsumer.org: PARP blockers effective in treating hard-to-treat breast cancers

PARP blockers effective in treating hard-to-treat breast cancers
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admin on 05/31/2009 21:27:00
 
Sunday May 31, 2009 (foodconsumer.org) -- Studies presented Sunday at the annual
meeting of the American Society of Clinical Oncology in Orlando suggest that
experimental cancer drugs may be used to treat some of the most aggressive forms
of breast cancer  such as triple negative breast cancers, and possibly ovarian
cancer as well.
The experimental cancer drugs, known as PARP inhibitors, block the ability of
cancer cells to repair DNA damage caused by treatment and prevent the cancer
from coming back and/or shrink its size, which is the purpose of conventional
cancer treatments.
In one study, Joyce O'Shaughnessy of the Baylor Charles A. Sammons Cancer Center
tested on 116 triple negative patients a PARP inhibitor made by BiPar Sciences
Inc., which was acquired by Sanofi-Aventis early this year for $500 million.
The patients who received the new cancer drug along with chemo lived 3.5 months
longer than those who just got chemotherapy.
Eric Winer at the Dana-Farber Cancer Institute was quoted by Forbes as saying
"This is one of the most exciting results we have seen in a long time."
One study tested a PARP inhibitor developed by one of Sanofi's competitors,
AstraZeneca.  In patients who carried mutations in the BRCA1 or BRCA2 genes, the
AstraZeneca drug shrunk the size of breast cancer in 41 percent of patients with
the mutations.
And another study showed the drug also helped ovarian cancer patients.
The PARP inhibitors may not work in all breast cancer patients as "most breast
tumors aren't driven by aberrant DNA repair," Forbes reports.
"One of the key things is to match the cancer drug to the right patient
population," Alan Ashworth at the Institute of Cancer Research in London was
quoted as saying.  Ashworth early on carried out an experiment suggesting that
patients with BRCA mutations might be susceptible to PARP inhibitors.
PARP stands for Poly(ADP-ribose) polymerase, a zinc-finger DNA-binding enzyme
that is activated by binding to DNA breaks.
A total of 18 PARPs have been identified, although PARP-1 and PARP-2 are the
most abundant, according to a review written by Nicola J. Curtin (University of
Newcastle-upon- Tyne) and published in 2005 in Expert Reviews in Molecular
Medicine.
The new drugs can disable cancer cells' resistance to cytotoxic therapy and
potentially improve the efficacy of cancer treatments.
Breast cancer occurs in tissues of the breast, usually the ducts or tubes that
carry milk to the nipple and lobules or glands that make milk. The National
Cancer Institute says that 194,280 Americans are expected to be diagnosed and
40,610 will die from the disease in 2009.
(By david Liu and edited by Rachel Stockton)