Science has not yet determined why the prostate cells make PSA. Perhaps it plays a role in the mixing of sperm and seminal fluid. Scientists have discovered conditions that can trigger an increased production of PSA. Prostate cancer is one of those conditions.
A simple laboratory test can be used to measure the PSA level in a man’s bloodstream. The apparent link between prostate cancer and PSA production increased interest among health professionals in that simple blood test. Biotechnology companies began to modify the test, hoping to create a more efficacious assay method.
The development of a PSA assay would begin with the acquisition of a tiny vial of cells. The company that wanted to create a PSA test kit would order frozen cells from a national cell repository. They request cancer cells, cells with the ability to produce large amounts of PSA.
Researchers would culture those cells, so that they divided again and again. Soon the tiny vial of cells had expanded to a cell colony, one with hundreds of cells. The first colony of cells would usually appear in a small plastic flask. Later the cells in that small flask would be transferred to a larger plastic flask.
The cultured cells would attach to the flat plastic surface. The attached cells would release PSA into the culture media, the liquid used to “feed” the cultured cells. The researcher would then have “conditioned media.” A laboratory test would confirm the presence of PSA in that media. Eventually a biochemist would extract the PSA from the conditioned media.
The purified PSA would be used to make antibodies to the PSA. The antibodies would be coated onto the wells of a test kit. The test kit would thus be ready to receive blood samples from male patients, men who wanted to know whether or not they had prostate cancer.
During the performance of a laboratory test, a blood sample with a high level of PSA might be put in one test well. The prostate specific antigen would stick to the PSA antibody. A second PSA antigen would be added to the same well, followed by a second antibody. A labeling agent would then be attached to the antibody. The assay equipment in the lab could be used to determine the amount of label in each well of the test kit.
Each pair of wells would contain the blood sample from a different patient. The amount of label detected in the laboratory would signal the amount of PSA in the patient’s blood. A large amount of PSA would suggest that the patient’s doctor should order a biopsy of the patient’s prostate. Such a biopsy would either confirm or refute the possible presence of tumor cells in the patient’s prostate gland.
A man might learn that he had a high PSA in his bloodstream, but a biopsy revealed no evidence of a prostate tumor. The PSA test had yielded a false positive result.