Co-investigators Andries Zijlstra, an assistant professor at Vanderbilt University Medical Center, and John Lewis, an associate professor at the University of Alberta, said some prostate cancer spreads slowly and does not lead to serious symptoms, while in other patients the cancer metastasizes to other parts of the body and is fatal. Cancer researchers have been searching for biomarkers that indicate which patients should be treated aggressively and which patients can be followed through active surveillance, or watchful waiting.
Zijlstra and colleagues investigated the protein CD151 that facilitates the migration of cancer cells. In prostate cancer cell lines, they discovered that CD151 is free from its normal adhesion partner -- integrin -- another protein that allows a cell to stick to the surrounding tissue. This form of CD151 called "CD151free" proved to be functionally important in cancer.
"It was a big surprise that some of this CD151 protein was now free of that partner and it turns out that it only occurs when a cancer is formed," Zijlstra said in a statement. "What's so novel about this discovery is we're not talking about changing protein expression, which is what we traditionally see. We're talking about a protein that changes its molecular state and detection of that molecular state is an indication of disease progression."
In collaboration with Lewis and colleagues in Alberta, the group looked at tissue samples from 137 patients treated for prostate cancer in Canada over the past 12 years.
The team determined that if patients tested positive for CD151free their cancer recurred and spread earlier than patients without any detectable CD151free.
"Patients who tested positive for the biomarker developed metastasis an average of 10 years earlier than those who tested negative," Lewis said.
The findings were published online ahead of the print edition of Cancer Research.