Scientists have identified a new group of culprits that play a major role in the development of human cancers.

They are tiny bits of ribonucleic acid (RNA) called microRNAs, which control gene activity. Three teams of researchers said on Wednesday microRNA initiates some cancers and could be used to diagnose the illness.

RNA is involved in making proteins in cells.

“These minuscule molecules are now definitely linked to the development of cancer,” Paul Meltzer, of the National Human Genome Research Institute in Maryland, said in a commentary in the science journal Nature.

He added that the three independent studies published in the journal change the landscape of cancer genetics.

Todd Golub and his team at the Dana Farber Cancer Institute in Boston showed that different human cancers have a distinctive microRNA fingerprint.

In a second study scientists at the Cold Spring Harbour Laboratory in New York reported that a certain cluster of microRNAs seem to cause cancer in mice.

The third report, by Joshua Mendell and researchers at The Johns Hopkins University School of Medicine in Maryland, found that some microRNAs cooperate with a gene linked to human cancers.

“Our discovery fits in quite well with the two other labs’ studies on the involvement of microRNAs in cancer,” Mendell said in a statement.

More than 200 microRNAs are known but how they function is still a mystery.

Meltzer said the findings could shed new light on what goes wrong when tumours are formed, how to detect cancers and to select the most appropriate treatment.