Blood is a readily available and rich source of biomarkers that have the potential for use in diagnostics and companion diagnostics development, disease characterization and monitoring, and predictive drug response and toxicity analysis. Serum profiling using a variety of techniques to identify disease- or treatment-related proteins, antibodies, or oligonucleotides is leading to the identification of well-defined biosignatures and patterns of biomarker expression that are playing an important role in research, preclinical testing, patient stratification for clinical trials, therapeutic assessment, and increasingly in commercial diagnostic and prognostic applications and in drug selection.
At the American Association for Cancer Research annual meeting, Exiqon will present data from its diagnostic program aimed at early detection of colorectal cancer (CRC). The company applied its miRCURY LNA™ Universal RT microRNA PCR system to detect a miRNA signature in blood plasma indicative of CRC. The signature was derived from comparisons of profiles of several hundred miRNAs in about 200 patients with CRC and a comparably sized control group.
By the end of 2011, Exiqon expects to complete a validation study that will include about 5,000 patient samples. “It is hoped that this will eventually lead to a blood sample miRNA-based test that will identify patients at high risk of having early-stage (0-II) CRC with significantly greater precision than the currently used—but not very accurate—fecal occult blood test, which also suffers from poor patient adherence,” says Niels Montano Frandsen, Ph.D., product manager at Exiqon.
Patients identified as high-risk would be referred for follow-up testing such as colonoscopy.
Dr. Frandsen believes that despite the challenge of detecting miRNAs due to their small size, they “have all the hallmarks of a new class of powerful diagnostic and prognostic biomarkers of disease, drug efficacy, and toxicity.”
He notes their stability in clinical sample material such as FFPE tissue samples, blood serum and plasma, and urine. “We have found that miRNA levels in plasma are virtually unaffected by sample handling; samples can be left at room temperature for extended periods and thaw/frozen multiple times with no effect.”
Exiqon’s miRCURY system incorporates a universal cDNA synthesis reaction followed by PCR amplification with two miRNA-specific primers, which is possible through the use of LNA technology. The use of SYBR Green enables melt-curve analysis, which allows for verification of the amplification products.
The company currently offers two human miRNA panels and one mouse/rat panel, each containing 370 miRNAs on a 386-well plate, and will soon launch a second mouse/rat panel. In addition, toward mid-year, Exiqon plans to introduce its new Pick-a-Mix customized panels for which customers can specify a set of desired miRNAs and design a panel for a specific disease indication.