Review date: 17 August 2020
Citation: Expression of small non-coding RNAs in urinary exosomes classifies prostate cancer into indolent and aggressive disease. Wang, W.W. et al., The Journal of Urology 2020.
In Australia, prostate cancer is the second-most common cancer diagnosed in men, and the third highest cause of cancer death.
Early development of prostate cancer usually occurs silently. When symptoms do eventually present, they can be non-specific and might be overlooked. But if prostate cancer is diagnosed early, rates of cure and survival are very high.
Early detection of prostate cancer in asymptomatic men can reduce preventable illness and death. Ideally, we’d have a national screening program, like we do for bowel cancer. The trouble is that available tests are not reliable enough to justify population-based screening of asymptomatic men.
The prostate-specific antigen (PSA) blood test is unsuitable as a stand-alone screening test. The principal concern is that PSA measurement results in a high rate of overdiagnosis; identification of cancers in men whose lives would never have actually been affected, and for whom the consequences of treatment are more troublesome than the cancer itself.
Evolution of the use of PSA testing to guide prostate cancer diagnosis and treatment is ongoing. Combining PSA measurement with new technologies, such as magnetic resonance imaging (MRI), is already leading to improved detection, diagnosis and treatment of prostate cancer, but this approach is unsuitable for widespread screening.
An ideal screening test for prostate cancer would be non-invasive, sensitive, specific and capable of grading disease.
Research published by a USA-based company introduces 3 new tests with great promise for widespread prostate cancer screening.
The company has developed algorithms to analyse levels of small non-coding ribonucleic acids (sncRNAs) in the contents of exosomes collected from urine that correspond to the presence or absence of prostate cancer and allow grading of disease with high sensitivity and specificity. Exosomes are small (30-150 nm) vesicles secreted by most of our body’s cells that provide information about the cells from which they’re derived.
Exosome contents include fats and proteins, as well as DNA (the cell’s genetic material) and RNA (the molecule that translates the genetic message into the production of proteins) from the original cell. Small non-coding RNAs are short lengths of RNA that do not result in production of proteins themselves, but regulate the translation of genes into other proteins by interacting with their messenger RNAs.
Exosomes are reasonably easy to isolate from urine, and the extraction and measurement of sncRNA levels from them is achievable using commercially available laboratory kits.
The researchers used data from over 800 men to identify sncRNAs associated with the presence of prostate cancer, and its grade, and develop their algorithms. They then applied their tests to data from another 600 patients for validation.
The laboratory measurements, data analysis techniques and clinical studies used to develop the new urine tests for prostate cancer are a great example of how fundamental scientific discovery and technological advances can improve healthcare.
Accurate, non-invasive detection and staging of prostate cancer that can be offered widely will allow the best possible outcomes for all men.