Determining whether a man's prostate cancer is aggressive or slow-growing may one day soon be as simple as a urine test.
Research published this week in Nature identifies a new biological marker in the urine of patients with prostate cancer that indicates whether the cancer is progressing and spreading.
For decades now, one of the biggest challenges doctors have faced with treating prostate cancer is determining if the cancer is aggressive, says senior study author Dr. Arul Chinnaiyan, director of the Michigan Center for Translational Pathology.
"We end up overtreating our patients because physicians don't know which tumors will be slow-growing. With this research, we have identified a potential marker for the aggressive tumors," he says.
Chinnaiyan and colleagues examined the metabolites in the urine of prostate cancer patients compared with that of healthy individuals. They found that sarcosine -- an amino acid derivative -- was present in the urine of patients with prostate cancer and in particularly high levels in those with aggressive forms of the illness.
What's more, the sarcosine levels increased as the tumours grew, suggesting that simply measuring levels of the metabolite itself could aid in making an accurate prognosis for patients.
The team went on to test how sarcosine affected the behavior of cancer cells grown in the laboratory. To their surprise, the researchers found that adding the metabolite to prostate cells caused benign prostate cells to become cancerous, suggesting that the chemical plays an as-yet-not-understood role in metastasis.
They also found that manipulating sarcosine levels in the test tube could alter the course of tumor growth. Conversely, shutting down sarcosine production in cancer cells blocked invasion.
"This really told us that sarcosine is involved biologically in some of the processes of a cancer cell," Chinnaiyan said.
The researchers hope that their findings could one day lead to a simple, non-invasive prostate cancer test. Such a diagnostic tool could complement the current standard test, the prostate-specific antigen, or PSA, test now widely used in prostate cancer patients - or it could replace it altogether.
The researchers caution that their work is still at an early stage, and a test is at least five years away.
The findings may also offer new opportunities for treatment if researchers can learn how to design drugs that block sarcosine.
"Therapeutically, we could envision small molecules or antibodies that might inhibit some of the pathway components that lead to sarcosine up-regulation," explained Chinnaiyan.
