Study Reveals Abundance of microRNAs in Colorectal Cancer Cells
A group of researchers from academia and industry said this week that a broad experimental analysis of human microRNAs has uncovered 200 known mature miRNAs, 133 novel miRNA candidates, and 112 previously uncharacterized miRNA forms from human colorectal cancer cells.
The results suggest that the human genome contains significantly more miRNAs than have been currently identified, according to the researchers, whose study will appear in the March 7 issue of the Proceedings of the National Academy of Sciences.
According to the PNAS paper, the researchers used an analytical technique termed miRage, or miRNA serial analysis of gene expression, which involves isolating 18- to 26-base RNA molecules to which specialized linkers are ligated, and which are then reverse-transcribed into cDNA. Subsequent steps in the miRage process — including using PCR to amplify the cDNA mixture, tag purificaition, concatenation, cloning, and sequencing — are performed using SAGE methodology optimized for small RNA species.
The researchers used the miRage process to analyze cDNA tags from four human colorectal cancers and two matching samples of normal colonic mucosa, the paper states. "Comparing these tags to the existing miRNA database identified 68,376 tags matching known miRNA sequences. These represent the largest collection of human miRNA sequences identified to date, because all previous human miRNA cloning analyses in aggregate have analyzed [fewer than] 2,000 miRNA molecules."
The paper's authors note that "the identified miRNA tags matched 200 of the mature miRNAs present in the public miRBase database … and 52 of these were expressed at significantly different levels between tumor cells and normal colonic epithelium. Importantly, of the already catalogued miRNAs, these results provide novel experimental evidence for 62 miRNAs whose presence in this database was based solely on phylogenetic predictions."
The paper's authors added that "in addition to detecting known or predicted miRNAs, 1,411 of the miRage tags represented 100 previously unrecognized miRNA forms of known miRNAs."
In order to help evaluate candidate miRNAs, the researchers also "disrupted the Dicer locus in three human colorectal cancer cell lines, and examined known and novel miRNAs in these cells," the PNAS paper states. Their observations were consistent with "the conclusion that Dicer is required for the biogenesis of a subset of known and novel miRNAs."
The researchers conclude in the PNAS paper that their "studies have provided experimental evidence that the human genome contains a much larger number of miRNAs than previously appreciated … [and that] many novel miRNAs remain to be identified."
They add that because their experiments focused on cells from one tissue type, miRage analyses in other cell and tissue types will likely "be equally informative."
The research published in PNAS was conducted by researchers at The Sidney Kimmel Comprehensive Cancer Center; the Howard Hughes Medical Institute; Johns Hopkins Medical Institutes; Rosetta Genomics, Ambion Diagnostics (soon to be Asuragen), Merck unit Rosetta Inpharmatics, and Indivumed; and the Center for Cancer Research at the Israelitic Hospital.
Luminex Licenses MIT IP as 'Prelude' to Entry Into microRNA Space
Luminex said this week that it has obtained a non-exclusive license from the Massachusetts Institute of Technology to intellectual property the company will use to develop and commercialize microRNA assays and related products.
According to the company, the rights and potential applications of the IP cover both life science research and clinical diagnostics. Terms of the deal were not disclosed.
Randel Marfin, vice president of the Luminex bioscience group, said the deal is "the prelude to microRNA products" for the company.
"There are no microRNA products commercially available with Luminex today," he told RNAi News this week, adding that miRNA products for the life sciences market are under development.
He declined to comment on specifically what form those products may take, but noted that Luminex is also evaluating the miRNA diagnostics field.