Abstract
Prostate-specific antigen lacks specificity for prostate cancer, so the identification and characterization of a unique blood-based marker for the disease would provide for a more accurate diagnosis, reducing both unnecessary biopsies and patient uncertainty. We previously identified a novel biomarker for prostate cancer, early prostate cancer antigen (EPCA). EPCA antibodies positively stained the negative biopsies of men who, as much as 5 years later, were diagnosed with prostate cancer. The goal of this study was to determine whether EPCA antibodies could be used in a clinically applicable plasma-based immunoassay to specifically detect prostate cancer. Using an EPCA-based ELISA, the protein was measured in the plasma of 46 individuals, including prostate cancer patients, healthy individuals, other cancer patients, spinal cord injury victims, and patients with prostatitis. With a predetermined cutoff value of 1.7 absorbance at 450 nm, only the prostate cancer population, as a whole, expressed plasma-EPCA levels above the cutoff. Statistical analysis showed a significant difference in EPCA levels between the prostate cancer population and each of the other groups, specifically the healthy donors (P < 0.0001), bladder cancer patients (P = 0.03), and spinal cord injury patients (P = 0.001). Sensitivity of the EPCA assay for prostate cancer patients was 92% whereas the overall specificity was 94%. Specificity for the healthy donors was 100%. Although larger trials are required, this initial study shows the potential of EPCA to serve as a highly specific blood-based marker for prostate cancer. EPCA, when coupled with prostate-specific antigen, may help reduce the number of both unnecessary biopsies and undetected prostate tumors.
Highlights
The identification of specific cancer biomarkers can have a significant effect on the prognosis, diagnosis, and treatment options for patients
We have developed a urine assay for the detection of bladder cancer based on BLCA-4, which is one of six unique bladder cancer nuclear matrix proteins (NMP) identified in our laboratory [8]
Using anti-early prostate cancer antigen (EPCA) antibodies previously described [9], we developed an indirect ELISA to measure the level of EPCA in the plasma of various patient populations
Summary
The identification of specific cancer biomarkers can have a significant effect on the prognosis, diagnosis, and treatment options for patients. Prostate cancer is the most commonly diagnosed cancer in men living in the United States, and it is the second leading cause of cancer death in that same population [1]. Prostate-specific antigen (PSA) and digital rectal exams remain the hallmark assessments for screening individuals for prostate cancer. The combined use of these diagnostic techniques has changed the clinical course of the disease by allowing for an earlier detection of tumors [2]. PSA has limited specificity in that it is not a tumor marker, but a protease that is normally expressed in the organ. Abnormal PSA values, those in the 4 to
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