One of the most important unsolved problems in prostate cancer today is to find a way predict the eventual outcome of an individual?s prostate cancer at the time he is first diagnosed. Although the PSA test has allowed considerably earlier diagnosis of prostate cancer, a positive PSA only tells that there is prostate cancer present today. It does not predict what will happen to that cancer tomorrow. What is necessary is to find prognostic markers that will tell which tumors will stay confined to the prostate over time and which are at risk for metastasis. In prostate cancer, a marker may be considered predictive if it can distinguish which patients require immediate treatment and which patients can safely be monitored over time without immediate radiation or surgery.

The best diagnostic markers are those that distinguish an early tumor from normal tissue. If such a marker is present in a tumor or in the blood of a patient, then a tumor is likely present. The best predictive markers may be those that arise later in the course of tumor development; those that arise around the time that the tumor is becoming metastatic. The presence of such markers at the time of diagnosis may be sufficient to indicate that a patient is at risk of developing cancer metastases. We have made an effort to find such markers for human prostate cancer.

We have found one marker that appears promising as a predictive marker for prostate cancer. Called thymosin beta 15 or TB15, this molecule regulates the rate of movement of prostate cancer cells. Normal cells and early cancer cells make no TB15. As cells become metastatic, the levels of TB15 begin to rise and the cells become able to move faster (Bao L, Loda, M, Janmey PA, Anand-Apte B, Zetter BR. Thymosin _15: A novel regulator of tumor cell motility upregulated in metastatic prostate cancer. Nature Medicine. 1996; 2:1322-1328). Rapid movement is an important component of metastatic tumor cells (Please see the section of this web site on "cell migration").