Lab test for microRNAs may help detect cancer

This laboratory study was performed by Patrick Mitchell, Rachael Parkin, Evan Kroh and colleagues from the Fred Hutchison Cancer Research Center and three other institutes in Seattle. It was published online in the Proceedings of the National Academy of Sciences on 28 July 2008.

The researchers showed that blood plasma contained microRNA molecules that unlike RNA are remarkably stable. They also found that the levels in serum were similar to those in plasma.

The team then looked for tumour microRNA in blood after grafting human prostate cancer cells into mice. Tumour microRNA was readily detected in the blood of the grafted mice but not in that from a control group.

Finally, to discover whether these molecules might be useful for diagnosis in humans, they searched published literature and found six microRNAs that had been identified in prostate cancer cells but were not present in healthy blood.  They compared the levels of these in pooled serum samples from 25 men with prostate cancer metastases with the levels in pooled serum from 25 healthy controls. A microRNA called miR-141 showed the largest difference, so it was used to examine each serum individually. The miR-141 molecule was detected in 15 of the 25 sera from cancer patients but in none of the sera from healthy men.

Clearly, the study was of a relatively small number of men with advanced prostate cancer and future work will need to increase the sensitivity of the test, to examine a larger number of men with earlier prostate cancer and to see if the test can be applied to other cancers. The measurement of blood microRNAs is a promising new approach to cancer diagnosis.