MicroRNAs Accurately Identify Tumor Origin

A study has demonstrated microRNAs' significant potential to act as effective biomarkers that may be applied in a diagnostic test designed to identify the primary tumor site in patients with cancer of unknown primary (CUP).

Each year, approximately 70,000 patients in the United States are diagnosed with CUP. A patient typically is diagnosed with CUP only after undergoing a wide range of tests, including imaging tests, which have failed to identify the origin of the cancer. Accurately identifying the origin of a metastasis can be critical in guiding treatment decisions.

MicroRNAs (miRNAs) are naturally occurring, small RNAs that act as master regulators and have the potential to form the basis of a new class of diagnostics and therapeutics. Because many diseases are caused by the abnormal activity of proteins, the ability to selectively regulate protein activity through miRNAs could provide the means to treat a wide range of human diseases. In addition, miRNAs have been shown to have different expression in various pathologic conditions. As a result, these differences may provide novel diagnostic strategies for many diseases.

Rosetta Genomics (Rehovot, Israel) is currently developing a technology that will be the basis of CUP diagnostic tests. In a study reported in the March 23, 2008, online issue of the journal Nature Biotechnology, the scientists described the development and test validation of miRNA expression profiles for identification of tumor origin. miRNA expression was measured in RNA extracted from hundreds of formalin-fixed, paraffin-embedded (FFPE) samples from more than 20 different known primary tumor tissues and metastases. These results were used to build a classifier that assigns a primary site to a cancer sample based on the miRNA expression in the sample. A blinded test set found that the overall sensitivity of this classifier was approximately 85%, with two-thirds of the samples being classified with high-confidence, reaching accuracy exceeding 90% and specificity of 99%.

"Accurately identifying the origin of a metastasis in CUP patients can be critical for determining appropriate treatment, and currently presents a true unmet diagnostic need for patients and physicians,” said Amir Avniel, president and CEO of Rosetta Genomics. "This research demonstrates the tremendous potential of miRNAs as effective biomarkers, and is a significant step towards the development of the first miRNA-based diagnostic tests.”

Rosetta Genomics' research platform, which combines bioinformatics and state-of-the-art laboratory processes, has led to the discovery of hundreds of biologically validated novel human miRNAs. The company is working to develop a full range of miRNA-based diagnostic and therapeutic tools, focusing primarily on cancer and various women's conditions. The company expects that the first miRNA diagnostic tests applying its technology will be launched by Clinical Laboratory Improvement Amendments-
(CLIA)-certified laboratories in the United States in 2008.


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