There is a lot of interest in microRNAs and related small RNAs in the general scientific community. In spite of the interest, very little is known about the biological function of microRNAs. Since the early stages in the field, there has been speculation that microRNAs may be causative for human disease, including cancer.

Our paper provides solid evidence that indeed, some microRNAs are oncogenic. This information provides an important missing link in our understanding of the molecular causes of cancer. There is also interest in using microRNA inhibitors as anti-cancer therapeutics.

We have found a new class of genes that can cause cancer. The novelty lies in the fact that these genes do not code for protein, but generate regulatory RNAs.

The traditional way to think about genes is that they are used to make proteins. The search for cancer-causing genes has therefore focused on genes that make proteins. Recent work has illuminated a new class of genes that do not make proteins. Rather, they make biologically active small RNAs, called microRNAs. These small RNAs control the production of many proteins in the cell.

We have been studying microRNAs and are interested in the role they play in cancer. This publication describes the identification of several microRNA genes that are elevated in cancer, and can promote cancer in a mouse model. This is the first functional evidence that small RNAs can cause cancer. It increases our understanding of this complex disease and may provide new approaches for therapy.

Greg Hannon—of Cold Spring Harbor Lab—and I, have been studying small RNA pathways since the early stages of the field. We have made many important contributions in these last six years. Of course there have been, and still are, many obstacles.

Small RNAs represent a new way of looking at gene regulation, and we are still learning the basic biology. This work requires novel approaches; however, many bright scientists are converging on the field and this is accelerating progress.

This work reveals new players in the molecular pathways of cancer. Inhibitors of small RNAs have already been developed, which means we can immediately look at the possibility of using them for anti-cancer therapies. The implications are primarily medical, rather than political.