Biomarkers

A lot of hope for really early detection of cancers is pinned on finding molecular indicators of them–ie, biomarkers. Here’s an update from a Technology Review article:

Many of today’s tools for screening and diagnosing cancer are crude at best.
So researchers are working to find more-sensitive tests based on specific
molecules–called "biomarkers"–that are early signs of tumors and whose
concentration could, ideally, be measured in bodily fluids like blood.

While much of that research has focused on protein biomarkers, some of the first
molecular tests to arrive on the market may be ones that look instead at a
phenomenon called DNA methylation…

DNA methylation occurs when methyl groups–carbon atoms surrounded by three
hydrogen atoms each–attach to a gene without changing its actual sequence.
Methylation can alter a gene’s behavior by, for instance, turning it off, and
aberrant patterns of methylation are involved in almost all types of cancer.
What’s more, abnormal methylation happens early on in the disease process, which
makes it "a highly promising biomarker for cancer," says Stephen Baylin, an
oncology professor at the Johns Hopkins School of Medicine. Researchers have so
far identified some 40 to 50 genes whose methylation patterns play a role in the
development of cancer.

…[a] test, which OncoMethylome expects to commercialize by next year, would detect
methylation in biopsied prostate tissue. The current method of
diagnosis–examination of the tissue under a microscope–misses up to 30 percent
of cancers, so the new test would be used to confirm that cancer really was
absent in biopsies that appeared normal.

OncoMethylome is developing another set of tests to screen patients for
cancer before they reach the stage where a biopsy is called for. These screening
tests would look at patterns of methylation in two to five genes from DNA in
blood, urine, or saliva. The tests, which won’t be available for at least
another two years, are designed to detect early signs of cancers of the ovary,
bladder, prostate, and lung….

Like most other screening tools, these bodily-fluid tests will likely not
offer definitive results; positive tests would still need to be confirmed.
However, DNA-methylation screening is designed to be highly accurate in
identifying the people who really don’t have cancer so that they won’t
needlessly undergo more invasive and expensive testing such as colonoscopy.
Still, the tests will first need to be fast and cheap enough for routine use in
hospitals and diagnostic labs. — By Corie Lok