Newly identified members of the enzyme family that includes prostate-specific antigen show promise as potential biomarkers for ovarian cancer, according to a presentation at the annual meeting of the American Association of Clinical Chemistry. The kallikreins are a subgroup of an enzyme family called serine proteases. Kallikreins are expressed widely in the body, especially in hormone dependent tissues such as those of the testes, ovaries, and breast.

In the current work, Canadian researchers led by Eleftherios P. Diamandis, M.D., Ph.D, showed that newly identified members of the human kallikrein family -- such as hK5, hK6, hK7, hK8, hK10, and hK11 ? have promise as biomarkers for ovarian cancer. The research group had hypothesized that the newly identified proteins make up an enzyme cascade that is overexpressed in ovarian cancer cells, resulting in elevated levels of the enzymes that are part of the cascade.

The team examined serum samples collected 5 to 10 years ago from women with advanced-stage ovarian cancer. The medical history included clinical information such as stage, grade, and survival rate. Investigators correlated the levels of certain kallikreins with clinical pathological findings and found that many of the kallikreins that were abundant in the blood samples were associated with unfavorable prognostic markers such as advanced-stage or higher-grade disease. The researchers also discovered that patients who had higher elevations had shorter overall survival than those who had no elevation.

A current screening procedure using a biomarker called CA125 and ultrasound examination shows low sensitivity in detecting early-stage disease; Diamandis believes research on kallikrein expression patterns in women with early-stage disease may result in identification of biomarkers that can be used in combination with the current screening technique to diagnose the disease before it has become widespread.