New marker for prostate cancer gives hope for more accurate diagnosis than PSA test

18 May 2011

Researchers at Uppsala University have discovered a promising new  marker for diagnosing prostate cancer.

The research team, led by Professor Ulf Landegren of the University's Department of Immunology, Genetics, and Pathology, discovered a unique method for detecting prostate cancer that could lead to more reliable diagnoses and fewer unnecessary operations. The study has been published in the Proceedings of the National Academy of Sciences (PNAS),

The PSA test that is currently commonly used for diagnosing prostate cancer has been criticized for giving false positive responses, leading to unnecessary operations. There is therefore great interest in finding new and better biomarkers.

Masood Kamali-Moghaddam, a member of the research team, said, "In the limited patient material examined in the study, blood levels of so-called prostasomes seem to correlate more closely with the severity of the disease than do PSA levels."

The team has previously developed a uniquely specific and sensitive method, called proximity ligation, for effective determination of proteins, and the method has now been adapted for detecting prostasomes.

One of the co-authors of the present study, Professor Gunnar Ronquist, showed 30 years ago that prostate cells pump out large quantities of a tiny membrane-coated particle in semen, which he named prostasomes. The hypothesis is that, in cancer, rather than winding up in semen, prostasomes are pumped out into the surrounding cancer tissue in invasive cancer. Therefore, prostasomes could be expected to occur at elevated levels in blood in cases of prostate cancer.

It was not possible to detect prostasomes in blood peviously, but the researchers devised a unique test that requires several different antibodies to simultaneously recognize proteins on the surface of the prostasomes, and this allowed them to detect elevated levels of prostasomes in the blood of patients with prostate cancer.

“We are hopeful that this type of marker will prove valuable not only for prostate cancer but also in several other common tumor types,” says Masood Kamali-Moghaddam.

Reference

1. Gholamreza Tavoosidana et al. Multiple recognition assay reveals prostasomes as promising plasma biomarkers for prostate cancer. PNAS 2011; published ahead of print May 9, 2011, doi:10.1073/pnas.1019330108