TINY slugs of RNA dismissed as insignificant until recently appear to play an important role in the development of human cancer.
The main task of RNA was thought to be carrying the information for making proteins. But much smaller pieces called microRNAs are emerging as key players in cells (New 杏吧原创, 27 November 2004, p 36). Now three studies in Nature (vol 435, p 828, 834 and 839) provide the strongest evidence yet that microRNAs can trigger cancers when they go awry.
Gregory Hannon鈥檚 team at the Cold Spring Harbor Laboratory in New York state report finding a cluster of microRNAs that appear to trigger blood cancers in mice. In the second study, Todd Golub鈥檚 team at the Dana-Farber Cancer Institute in Boston has found that each type of human tumour has its own distinctive 鈥渇ingerprint鈥� of microRNAs, a finding that could lead to better diagnosis of cancers.
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Also, cancerous tissue usually contained less microRNA than healthy tissue, suggesting that it plays a role in preventing cancers. Finally, Joshua Mendell鈥檚 team at the Johns Hopkins University School of Medicine in Baltimore established that microRNAs help to regulate the gene c-Myc. Problems with c-Myc are implicated in 15 per cent of human cancers.
鈥淭he evidence has been building, but without concrete links till now,鈥� says Sam Griffiths-Jones of the Wellcome Trust Sanger Institute in Cambridge, who is curator of a global microRNA registry. Since microRNAs seem to orchestrate cells鈥� fate, it is no surprise that cancer can result if they malfunction, he says.
