Prostasome ELISA - a potential marker for prostate cancer diagnosis

Abstract The prostate gland, a male organ, situated right under the urine bladder, is involved in male reproduction. It can also be the place for more or less serious diseases such as inflammation, abnormal growth and cancer. Especially prostate cancer is very common in the Western world. Today PSA is the most widely used marker for detection of prostate cancer. Unfortunately, this method is not specific enough. Therefore, there is a need for a better marker for screening of malignant prostate cancer. The marker should be specific both for the organ prostate and for the cancer disease. One promising marker is the prostasome, a small vesicle emanating from epithelial cells in the ejaculatory ducts in the prostate. The aim of this project was to set up an ELISA and test a number of antibodies for their ability to work as suitable capture or detection antibodies. As blocking agent different concentrations of BSA were tested. Biotin-Streptavidin conjugate was used in the detection step. Two surface proteins, PSCA and PSMA were used as capture antigens; they are specific for prostasomes. Clusterin, a prostasomal surface-bound protein, was used as antigen for the secondary antibody in the assay. With this experimental setup the detection limit was 2500ng/mL, which is probably not enough to detect prostasomes in cancer. The development of the ELISA did not reach its final stage, a ready-to-use assay, during this project. We have not yet the knowledge of optimal antibody concentrations and the other test parameters are also at experimental state.