miRNAs: Optional for Cancer?

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Science  13 Jul 2012:
Vol. 337, Issue 6091, pp. 135
DOI: 10.1126/science.337.6091.135-b

MicroRNAs (miRNAs) are small noncoding RNAs that control the expression of about half of the protein-coding genes in mammals. These regulatory RNAs have been implicated in a wide range of diseases, including cancer, where a large body of evidence suggests that they are essential for tumor survival and growth. The surprising results of a new study invite reexamination of this hypothesis. By genetic methods, Ravi et al. generated mouse sarcoma cells that were completely deficient in DICER1, an enzyme essential for miRNA production, and then experimentally verified the nearly total loss of miRNAs in these cells. In contrast to expectations, when these cells were injected into mice, they retained the ability to form tumors, although the tumors developed at a slower rate than those derived from control cells. Thus, global miRNA loss does not intrinsically preclude tumorigenesis. Whether these results highlight a quirk of tumors derived from mesenchymal cells or also apply to tumors of epithelial origin (which represent the majority of human solid tumors) remains to be determined, but is an important question given the current interest in miRNAs as potential targets for cancer therapy.

Cancer Cell 21, 848 (2012).

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