MicroRNAs Can Also Act as Tumor Suppressors

Scientists have found that microRNAs, a form of genetic material, can function as tumor suppressors in laboratory studies.

In the May 1, 2007, issue of the journal Genes & Development, researchers Drs. Yong Sun Lee and Anindya Dutta from the University of Virginia (UVa; Charlottesville, VA, USA) have shown that microRNAs can inhibit the overexpression of a gene called HMGA2. This gene is related to creation of fatty tissue and specific tumors, as well as diet-induced obesity.

MicroRNA is a single-stranded RNA that is typically only 20-25 nucleotides long and is related to regulating the expression of other genes. "Overexpression of the HMGA2 gene is an essential feature of many medically significant tumors, such as uterine fibroids,” explained Dr. Dutta. "It is very exciting to realize that microRNAs have an important role in suppressing the overexpression of HMGA2. Thus, they may also have a role in causing, and perhaps curing, a disease that is responsible for the vast majority of hysterectomies in the Western world.”

By studying chromosomal HMGA2 translocations that are tied to human tumors, the researchers discovered that, in healthy cells, a microRNA called let-7 binds to the 3' end of the HMGA2 mRNA transcript and suppresses its expression in the cell cytosol. However, chromosomal breaks that shorten the 3' end of the HMGA2 transcript and prevent let-7 binding, result in abnormally high levels of HMGA2 expression and the formation of tumors (tumorigenesis).

This study, according to the researchers, establishes that HMGA2 is a target of let-7, and that the let-7 microRNA functions as a tumor suppressor to prevent cancer formation in healthy cells.


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