Development of a serum-based immunoassay for prostate cancer detection.

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Prostate cancer (PC) screening is currently based on evaluation of prostate specific antigen (PSA), however there is insufficient evidence to recommend that average-risk men undergo regular screening. PSA is more prostate specific than cancer specific, and elevated PSA can also be found in benign conditions of the prostate. Our aim is to develop improved non-invasive serum-based immunodiagnostic assays for PC detection and disease management. To this end, we have focused our efforts on: i) developing more sensitive and specific biomarkers for PC screening, and ii) developing biomarkers that allow discrimination between malignant and benign conditions of the prostate, including benign prostate hyperplasia (BPH). We have applied our proprietary technologies to discover and validate a panel of biomarkers using a multiplex screening platform known as Matrix Protein Array Technology (MPAT). The MPAT involves the screening of clinical samples with a large collection of 70,000 distinct polyclonal antibodies. Total proteome from normal, cancer, and benign serum samples was printed on a solid support, and reacted with individual antibodies. Antibody-sample reaction was detected by chemiluminescence, and computer analysis of a CCD-acquired image was applied to quantify each spot. Statistical analysis of the data points thus generated enabled the selection of a panel of biomarkers that are differentially expressed in early and advanced stage of PC versus normal controls, or in BPH versus PC samples and normal controls. Biomarkers were validated on a large number of samples, including 242 serum specimens comprising 73 T1/T2 (early stage PC), 69 T3/T4 (advanced stage PC), 50 BPH, and 50 normal controls, and sensitivity and specificity were determined from receiver operating curves (ROC) using statistical package GB-STAT (Dynamic microsystem). We found BPH specific biomarkers that were significantly elevated in BPH versus cancer and normal samples, and biomarkers that significantly discriminate cancer (early and late stage respectively) versus normal and benign. Sensitivity is ranging from 70-80% at 80% specificity. Biomarkers are being combined to optimize sensitivity. We are fully characterizing these biomarkers, and producing a large supply of monospecific antibodies to develop a serum-based immunodiagnostic assay for detection of BPH, early and advanced PC. These biomarkers may have application in early detection, and disease management of PC. A BPH specific diagnostic test would improve accurate PC detection, and reduce unnecessary biopsies.