There was a lot of DNA, 90% or so that used to be called junk DNA. Seems odd that no one would wonder what the purpose of that 90% was. Well, researchers have recently realized that like the other 10%, it creates RNA. But, whereas the 10% creates RNA that codes for proteins, the other 90% is called noncoding RNA. Some is called microRNA (miRNA) and others are called long noncoding RNAs (lncRNA), both names being descriptive.
Noncoding RNA Function
So what does this 90% do? It is involved in epigenetic mechanisms, gene expression and protein activity. It does this for both normal functioning and in disease states like cancer.
In other words, these RNAs regulate protein activity and gene function. So, the race is on to discover what all these RNAs do and see if they can be used as a diagnostic test for disease or infection or if they can be used as a treatment.
Example
In one example involving patients with hepatitis C, an miRNA, miR-122 was targeted. A drug called miravirsen, which is an antisense oligonucleotide, was used to treat the patients. It binds with miR-122 and keeps it from working. But hepatitis C needs it to replicate and also for stability, which should cure or reduce the affect of the hepatitis C. It is still in trials, so the final results aren’t know yet.
Cancer
Cancer is a major of study. Because noncoding RNAs are so ubiquitous, they are not only involved in just about every aspect of normal functioning, they are involved in almost every aspect of cancer as well: initiation, progression and proliferation and metastasis.
Dr. Calin at MD Anderson Cancer Center at the University of Texas is looking for miRNAs that are in the range of 21-22 nucleotides long. If these can be associated with certain cancers or stages of cancers, they will have great benefit as a diagnostic tool. They are of interest because they are not only found in the tumors but also circulating in the blood and other bodily fluids.
The technology has progressed enough that it isn’t holding back discovery as much designing and running studies that prove the predictive value of the biomarkers.
Therapeutic Use Issues
It is one thing to use a noncoding RNA as a diagnostic tool. You can look for variations from normal levels. But to use them for therapeutic tools is a lot trickier. Usually, one of these RNAs has roles in many pathways. So if you disrupt it to fix something in one pathway, you may mess up something else in a number of other pathways. So you need to look for an RNA that very specific activity.