Expression Profiles of 16 Genes Predict Prostate Carcinoma Relapse and Disease Free Survival Using Universal Bead Arrays
April 5, 2006 - Researchers say that a chip that measures expression of 16 genes provides much needed prognostic information for prostate cancer patients who fall in the “gray zone” of traditional tests.
This experimental “universal bead array” test, which is designed to be low cost and easy to administer, appears to be a better predictor of relapse and disease-free survival than the Gleason Score, according to lead author Jessica Wang-Rodriguez, M.D., associate clinical professor of Pathology at the University of California, San Diego.
The 50 year-old Gleason Score, which assigns a progressive score of 1-10, based on how differentiated the cells look in a prostate cancer sample, works fairly well when the score is either very low or very high, but the prognosis for men who have scores in the mid-range is difficult to predict, Wang-Rodriguez said.
“It is very difficult to predict relapse and cancer recurrence in men who have a score of 6 or 7,” she said. “Half of patients with these scores do well, and the other half don't, but we cannot now predict who will fall into those groups.”
Believing that a gene microarray test might provide additional information, a team of researchers led by Wang-Rodriguez picked 512 genes from the scientific literature that seemed to play a role in prostate cancer. They tested their expression on paraffin-embedded tumor samples taken from 71 patients, as well as on 41 control samples (non-cancerous prostate tissue taken from the same group of patients).
From this, they identified 16 candidate genes to further analyze. Ten of the genes were positively correlated to cancer progression, and six were negatively correlated, she said, and when tested, the combination generated a gene expression score that provided a better predictor of relapse than the Gleason score. “This gene expression score appears to give us additional prognostic information that current technology cannot provide, and that will help us treat patients accordingly,” she said.
The assay they used was developed by Illumina Inc., of San Diego, which also funded this study. It uses fine optic beads and needs only tiny amount of DNA and RNA, Wang-Rodriguez said, and up to 96 different tests can be put on a single tray. “Having batches of samples together in a single assay that can then be read automatically makes it easy for routine clinical use,” she said. “The test has a lot of potential, but needs to be further studied and validated.”