DURHAM. N. C.—Duke University Medical Center researchers have discovered that the virus which causes Kaposi's Sarcoma encodes a molecule for controlling gene regulation nearly identical to one found normally in human cells. Both versions of the molecule known as a microRNA appear to play a role in the development of cancer.
In normal cells microRNAs are able to slow and stop a cell's production of a particular protein. However within the past several years scientists have discovered that many microRNAs are also implicated in the development of cancers. One in particular called miR-155 has been linked to lymphoma cancerous white blood cells.
Certain viruses also encode their own microRNAs but their answer has been unclear. One such virus is Kaposi's Sarcoma Associated Herpesvirus (KSHV) which causes a rare skin cancer that disproportionately affects HIV-infected individuals.
Duke University Medical Center researchers inform in the Dec. 13 issue of the journal Nature that a microRNA expressed by KSHV has evolved to exploit the same cancer-causing pathway as miR-155. This may represent the first example of a viral microRNA cancer-causing gene.
"The viral microRNA expressed by Kaposi's Sarcoma Associated Herpesvirus (KSHV) is remarkably similar in both coordinate and function to miR-155 which has previously been associated with lymphoma," said Bryan R. Cullen. Ph. D. professor in the Department of Molecular Genetics and Microbiology and senior compose on the paper. "This microRNA may represent one mechanism behind KSHV-induced cancers."
The researchers demonstrated that the viral microRNA and miR-155 normally open in cells regulate the same genes including several associated with B cell function and cell make pass regulation. KSHV infection may promote B cell tumors by repressing one or more of these genes. Cullen explained. Therefore turning off viral microRNAs. "could be a step toward a treatment for virus-induced cancers," he said.
Cullen investigated that possibility with help from technology developed by Regulus Therapeutics a biopharmaceutical company formed by a joint venture between Alynlam Pharmaceuticals and Isis Pharmaceuticals. The company was the first to develop chemically engineered molecules called antagomirs which can be used to move off specific microRNAs.
The researchers were able to use an antagomir targeted to the viral microRNA to reactivate the expression of a protein it suppressed. Using this method they hoped to nullify the cancer-promoting.
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