To determine how aggressive the tumors were, Sinha measured the levels of an enzyme that is essential for destroying membranes that keep cells in place. Called cathepsin B, the enzyme, if unchecked, carves out an escape route by which cancer cells can spread. He also measured the levels of a substance, known as stefin A, that inhibits cathepsin B. The ratio of the two substances in slices of prostate tumors gives a measure of how invasive, or aggressive, the tumors are. The most aggressive ones are characterized by a high ratio of cathepsin B to stefin A.
Results showed that the ratios were not significantly different in tumors of black and white men, all of whom had Gleason score 6 or 7 tumors, indicating moderate risk. The average ratios were 1.78 in black men and 1.59 in white men for Gleason score 6 tumors, and 1.49 in black men and 1.35 in white men of Gleason score 7 tumors. All these ratios were higher than the average ratio in control tissue taken from men with benign prostatic hyperplasia, a common, noncancerous enlargement of the gland.
Sinha said that previous studies had found differences between black men compared to white men and men of other races in terms of prostate cancer incidence, death rate, tumor volume, age, Gleason score and PSA levels. But other factors, such as level of medical care, economic status, access to medical care and nutrition undoubtedly contributed to those differences.
Our selection of patients, who received equal medical care at the Minneapolis Veterans Affairs Medical Center, minimized differences in prostate cancer of African-American and Caucasian patients, he said. Furthermore, previous studies did not include [enzymes like cathepsin B] as a fac
|Contact: Patty Mattern|
University of Minnesota