A new screening tool developed by scientists in Denmark may help detect the earliest stages of cancer by taking advantage of the body's own defenses. The researchers constructed a microarray system that analyzes patients' blood for a specific class of immune agents called autoantibodies. These are agents that attack the body's own tissue, targeting what they perceive as "foreign" cells, such as specific molecules on the surface of tumors.

The researchers found that, within a limited number of blood samples, the screening test could detect cancer-associated autoantibodies in patients recently diagnosed with prostate, breast, and ovarian cancer. Healthy individuals showed no signs of the immune agents in their blood. Their findings, published in the journal Cancer Research, suggest that autoantibodies may be effective biomarkers for early cancer development.

Normally, the immune system launches an antibody attack in the presence of a foreign invader or antigen, such as a bacteria or virus. However, in some cases, such as in rheumatoid arthritis and diabetes, the immune system turns on the body itself, releasing autoantibodies that attack its own tissues. In the case of cancer, these autoantibodies attack certain antigens on the surface of tumor cells. Hans Wandall, associate professor of cellular and molecular medicine at Copenhagen University in Denmark, says that in the near future, a simple blood test could detect the presence of autoantibodies as a warning sign of cancer.

Physicians can already administer blood tests that screen for certain cancers. These tests detect elevated levels of tumor markers--chemicals associated with tumors that circulate in the blood, such as prostate-specific antigen for prostate cancer, or cancer antigen 125 for ovarian cancer. However, these antigens can also sometimes be made by healthy cells, and have also been found in other, noncancerous diseases, making such tests less than foolproof.

Wandall adds that such tumor antigens are difficult to detect in the early stages of cancer, since these chemicals, once made by the tumor, are sloughed into the bloodstream and eventually absorbed by the liver. "You're fighting an uphill battle, because a tumor might produce a protein, but if it's at the early stages, it will be in small amounts, which will be cleared by the liver," says Wandall. "So that's why we turn to the immune response, which acts as sort of an immunological mirror of what's going on in cancer."

Wandall says the immune system can recognize and seek out tumor antigens, even at low levels, and attack them with autoantibodies that bind to the antigens before they reach the liver. These immune agents can circulate longer and at greater numbers compared to the tumor antigens themselves, making them more easily detectable.