Diagnostic microRNA markers for screening sporadic human colon cancer and active ulcerative colitis in stool and tissue.

By routinely and systematically being able to perform quantitative stem-loop reverse transcriptase followed by TaqMan PCR expression analysis on stool and tissue samples using fifteen human (Homo sapiens, hsa) micro(mi)RNA genes selected by careful analysis of the peer-reviewed literature, we were able to monitor changes at various stages of CRC, allowing for reliable diagnostic screening of colon cancer particularly at the early, pre-malignant stages, and for difficult-to-treat active ulcerative colitis (UC). Although the expression of some of the miRNA genes tested in tissue showed less variability in CRC or UC patients than in stool, the stool by itself appears well-suited to screening. A miRNA approach using stool samples promises to offer more sensitivity and specificity than currently used screening genomic, methylomic or proteomic methods for colon cancer. Larger prospective clinical studies utilizing stool derived from many control, colon cancer or UC patients, to allow for a statistically valid analysis, are now urgently required to standardize test performance and determine the true sensitivity and specificity of the miRNA screening approach, and to provide a numerical underpinning for these diseases as a function of total RNA. Moreover, when a miRNA screening test is combined with analysis of a messenger(m)RNA expression test, which has also been considered in earlier studies to be a highly sensitive and a very specific and reliable transcriptomic approach, as outlined in this article, bioinformatics can be used to correlate microRNA seed data with mRNA target data in order to gain a mechanistic understanding of how miRNAs regulate gene expression, enabling understanding of why these miRNA genes should be informative in a screening test.