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NCI Funds EDRN Labs to Sustain Biomarker Discovery
NCI has awarded $9.8 million in first-year funding for 17 Biomarkers
Developmental Laboratories within the Early Detection Research Network (EDRN).
Biomarkers are substances found in the blood, other body fluids, or tissues
that alone or in combination may signal the presence of cancer or the risk for
the disease. These laboratories are now charged with discovering new biomarkers
relevant to major cancers and identifying what combinations of biomarkers may
best detect cancer or predict cancer risk.
Other EDRN components are Biomarkers
Validation Laboratories, which work to validate the biomarker tests; Clinical
and Epidemiologic Centers, which conduct the early phases of clinical and
epidemiological research on the application of biomarkers; and the Data
Management and Coordinating Center, which provides logistical, informatics, and
statistical development and support.
These new Biomarkers Developmental
Laboratories have one of the biggest challenges in biomarker research:
searching through hundreds of samples using a variety of technologies to
identify candidate biomarkers. Investigators will examine the human genome
(genetic material), proteome (proteins made by genes), epitome (immune response
biomarkers via antibody-antigen patterns), and metabolome (metabolic pathways
and regulation), looking for potential ways to identify cancer and cancer risk.
In a quest to discover cancer at the earliest stage of progression, biomarkers
are often used as mileposts of cancer progression; they mark the critical
events along the progression pathway from normal, to precancerous, to malignant
cell.
More information on EDRN scientific components and projects, including a
listing of Biomarkers Validation Laboratories, can be found at
http://www3.cancer.gov/prevention/cbrg/edrn/components.html.
BRCA1 Mutation Increases Sensitivity to Chemotherapy
When choosing between chemotherapy agents for patients with breast or ovarian
cancer, until now, clinicians have not had available biomarkers to help guide
their decisions. But a review published in the November 17 Journal of the
National Cancer Institute reveals that BRCA1 gene mutations - biomarkers for
breast and ovarian cancer - are associated with sensitivity to DNA-damaging
chemotherapy and resistance to spindle poisons.
Researchers at Queen's
University Belfast in Northern Ireland (supported by several groups, including
the Research and Development Office of Northern Ireland, Breast Cancer Campaign
UK, and Cancer Research UK) searched preclinical and clinical papers published
between Jan. 1, 1994 and Aug. 31, 2004, finding that BRCA1 is a DNA-damage
response gene as well as a regulator of mitosis, possibly through the
microtubules that help cells divide. As a result of this dual role, tumors that
lack functional BRCA1 may be more sensitive to DNA-damaging chemotherapy agents
such as cisplatin, carboplatin, anthracycline, and cyclophosphamide, but may be
more resistant to drugs that thwart microtubule assembly and function, such as
paclitaxel, docetaxel, vincristine, and vinorelbine, which are known
collectively as spindle poisons. Conversely, tumors that overexpress BRCA1, and
are therefore resistant to DNA-damaging agents, may be vulnerable to spindle
poisons.
Because of conflicting results between preclinical and clinical
studies, however, the authors recommend that these associations be tested
further, and that patients with BRCA1 mutations have this gene sequenced so
that the specific type of mutation they have can be characterized with their
response to DNA-damaging chemotherapy and/or spindle poisons. Ultimately, it is
hoped that BRCA1 mutation analysis can be used as a predictive marker when
choosing chemotherapy options for breast and ovarian cancer patients.
Inverse Association Found Between Selenium and Colorectal Cancer
A study in the November 17 Journal of the National Cancer Institute has found
an inverse relationship between selenium blood levels and adenoma recurrence
risk. Researchers from the Arizona Cancer Center, in collaboration with other
cancer centers and government agencies such as NCI, CDC, and the U.S. Food and
Drug Administration (FDA), as well as medical and public health schools across
the country, found that higher blood selenium concentrations in study
participants were associated with lower risk for developing recurrent adenomas. This study was funded by grants from the U.S. Public
Health Service as well as NCI's Specialized Program of Research Excellence
(SPORE) in gastrointestinal cancer.
Selenium received attention as a possible
cancer preventive agent after initial findings of a trial that examined its
effects on nonmelanoma skin cancer. Other epidemiological studies have had
mixed results; some have shown selenium to have a protective effect against
colorectal cancer, while others have found no association. However, most
individual studies analyzed small sample sizes, resulting in greater
variability of results. This study pooled data from three separate studies in
order to increase the precision of risk estimates.
Selenium concentrations were
measured and baseline characteristics were tabulated from a total of 1,763
blood specimens from trial participants. Adenoma recurrence was analyzed for
each study, as well as for the pooled population. In the pooled analysis, a
linear decrease in the odds of adenoma recurrence was reported with increasing
blood selenium levels higher than 100 ng/ml, and a statistically significant
inverse relationship was observed between blood selenium levels and adenoma
recurrence. Researchers concluded that, based on study results, selenium has a
role in reducing the risk of colorectal adenoma recurrence.
Immunosuppressant Drug May Increase Risk of Lymphoma
Methotrexate (MTX) may promote Epstein-Barr virus (EBV)-positive lymphomas in
rheumatoid arthritis and polymyositis patients by reactivating latent EBV,
according to a study published in the November 17 Journal of the National
Cancer Institute. Supported by grants from NCI, U.S. Public Health Service, and
National Institutes of Health (NIH), researchers from the University of North
Carolina, Chapel Hill, NIH, and the German Research Cancer Centre, also found
that withdrawal of MTX therapy can result in regression in some EBV-positive
lymphomas in patients.
Patients receiving MTX for rheumatoid arthritis or for
polymyositis are at increased risk of developing EBV-associated
lymphoproliferative disorders compared with the general population. EBV
infection is common, with more than 90 percent of the adult population having a
lifelong persistent infection, but normally EBV does not cause B-cell
lymphomas. However, in immunosuppressed patients undergoing MTX therapy, an
increased level of infectious EBV might overwhelm the capacity of the host
immune system to eliminate early EBV-positive tumor cells.
Results from the
study indicated that MTX treatment was found to enhance expression of EBV genes
in two cell types using the doses expected in the serum of rheumatoid arthritis
patients. MXT was also found to induce the release of infectious EBV progeny
from the host cells. The authors conclude that "future studies should explore
whether MTX treatment of other patients, such as those with malignancies, may
increase the risk of EBV reactivation and other EBV-associated tumors."
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