The spread of tumor cells from the developmental site of origin in the body to other tissue locations is a process called metastasis. An estimated 2% to 5% of all cancers diagnosed may be metastasized carcinoma of unknown primary origin (CUP). Preferred treatment and prognosis is dependent on determining the site of origin of the carcinoma. Recent research implicates microRNAs (miRNAs) as potential biomarkers for determining the primary site of origin for metastasized tumors. miRNAs are small molecules of RNA 21 to 23 nucleotides in length that do not code for proteins but function to regulate expression of important genes that play a role in cell development, evolution, differentiation, proliferation, embryogenesis, and apoptosis. Research supports use of expression profiles or signatures of miRNAs in tumors to determine the original tissue type of cancers for which the origin is unknown. miRNA expression profiling is most often performed using microarray assays, while alternative methods often include less high-throughput methods, such as quantitative real-time polymerase chain reaction (PCR), or bead-based flow cytometry. Rosetta Genomics has developed the miRview mets assay using microarray analysis to
profile miRNA expression from tumor samples. Prometheus Laboratories has acquired commercial rights in the United States to all of the Rosetta Genomics miRNA assays, including the miRview mets.