New Unique Protein Marker For Prostate Cancer Identified

American Cancer Society
Monday, 3 November 2003

A newly identified cellular protein, labeled PCa-24, has been discovered that appears to be highly specific for prostate cancer. The finding comes from a study published in the December 15 issue of the American Cancer Society's peer-reviewed journal CANCER and could open the door to a screening test that clearly distinguishes between prostate cancer and benign prostatic hyperplasia before doctors perform a biopsy. The full study is published online via Wiley InterScience (

Prostate cancer is expected to afflict 220,900 men in 2003, making it the most commonly diagnosed cancer in men over 50 years old. Screening for prostate cancer begins with a test to measure serum levels of prostate specific antigen (PSA) and a digital rectal examination (DRE). PSA values greater than 4 or a DRE that finds prostate nodules can warrant further evaluation with a needle biopsy.

However PSA may also be produced in abnormally high levels by benign prostatic hyperplasia (BPH), a nonmalignant disease causing narrowing of the urethra and difficulty urinating. In addition, almost 35 percent of men with prostate cancer have normal PSA values. Therefore, PSA serum level alone is not a specific marker for prostate cancer and may lead to many unnecessary needle biopsies.

Dr. Brian Liu, assistant professor of surgery/urology at Brigham and Women's Hospital, Division of Urology, led a multidisciplinary team of researchers to use proteomics, the study of all proteins produced by a cell, to further characterize prostate cancer in hopes of identifying a unique marker.

The investigators identified a protein they named PCa-24, a smaller protein than PSA, and found that it appears to be unique to prostate cancer cells. PCa-24 was detected in 94 percent of epithelial cells from prostate cancer but detected neither in normal prostate cells nor in cells of BPH specimens.

The authors say, "We described the presence of what appears to be a unique prostate cancer associated protein, which we will now call PCa-24." They add, "One possible application for our findings is to determine the presence or absence of this protein in serum of patients with prostate cancer versus those with other urologic diseases, including BPH."

Article: "Prostate Carcinoma Tissue Proteomics for Biomarker Discovery," Yaxin Zheng, Ye Xu, Bin Ye, Junyi Lei, Michael H. Weinstein, Michael P. O'Leary, Jerome P. Richie, Samuel C. Mok, and Brian C.-S. Liu, CANCER; December 15, 2003; 98:12.

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