Frank Slack, a molecular biologist at Yale University, who was not involved in the study, says that microRNA molecules have been causing a stir among cancer researchers because "their expression patterns seem to give a pretty accurate indication of what type of cancer a patient might have, as well as indicating the potential prognosis of that patient." In fact, microRNAs seem to provide a more specific indicator of cancer type than measuring all the genes expressed in a tumor. However, the usefulness of measuring microRNA is limited if it requires sampling tumors directly. Scientists have been hunting for ways to detect cancer more quickly and easily using biomarkers in the blood or other bodily fluids. Slack says that recent studies showing that microRNAs can be detected in blood are exciting because they suggest that "you might be able to get that same information just from getting the blood from that patient."

Furthermore, Slack says, the Cell Research paper shows that microRNAs have patterns in diabetes and could be useful in other diseases that involve similar changes to microRNA. He says that such a blood marker would be particularly desirable in "diseases where you don't know the site of action or the lesion in the body." Even in a condition like diabetes, for which biomarkers exist, microRNAs might provide missing information, such as predicting a person's susceptibility, Slack adds.

Zhang says that spotting several different microRNAs specific to a disease would offer an advantage over relying on one or two biomarkers, which are not always present in individual cases. Such a biomarker could also be used to track a disease's progression over time and to evaluate a patient's response to a treatment. Zhang says that a patient's specific pattern of blood microRNAs could also serve as the basis for more personalized medicine, helping doctors distinguish between different forms of a disease or patients who are likely to respond differently to a drug.

The current study relied on expensive sequencing technologies, but Zhang says that eventually, microarrays could measure key microRNAs in the blood much more cheaply--tests that biotech companies are already beginning to develop. Slack says that microRNA is "a new kind of marker that will be emerging in the next decade or so" but that controlled studies are needed to see whether microRNA patterns provide reliable predictions about individual patients and also apply to a wide range of diseases.