Although there is a growing interest in developing circulating microRNA (miRNA) as noninvasive diagnostic biomarkers for the detection of high-risk colorectal adenomas and early-stage CRCs, but the comparative diagnostic significance of serum vs. exosomal miRNAs remains unexplored.
Based upon published literature, researchers from Mie University, Japan performed an initial discovery step by investigating the expression of a miRNA panel in 20 normal colonic mucosa, 27 adenomas, and 19 CRC tissues. They performed subsequent validation by quantifying expression of candidate miRNAs in total serum and in exosomes from 26 adenoma patients and 47 healthy controls, and evaluated their clinical significance and potential diagnostic value in colorectal adenomas.
The researchers observed that the expression of four miRNAs, miR-21, miR-29a, miR-92a, and miR-135b, was significantly higher in colorectal adenomas vs. normal colonic mucosa. During validation, expression of miR-21, miR-29a and miR-92a in serum was significantly higher in adenomas vs. healthy controls, significantly correlated with adenoma size and total adenoma number within the colorectum, and significantly discriminated patients with advanced adenomas. In contrast, although exosomal miR-21 and miR-29a levels in adenoma patients were significantly higher than those of healthy volunteers, only exosomal miR-21 significantly correlated with adenoma size and total adenoma number, and could discriminate patients with high-risk adenomas.
Scatter plots showing the correlation between serum or exosomal
miRNAs levels and maximum diameter of adenomas
Positive correlation between maximum diameter of adenomas and (A) serum miR-21 levels (rho = 0.422; P = 0.0002); (B) serum miR-29a levels (rho = 0.305; P = 0.0092); (C) serum miR-92a levels (rho = 0.413; P = 0.0003); (D) exosomal miR-21 levels (rho = 0.435; P = 0.0001). No significant correlation between maximum diameter of adenomas and (E) exosomal miR-29a levels (rho = 0.223; P = 0.0593); (F) exosomal miR-92a levels (rho = 0.108; P = 0.3654). Data were analyzed using the Spearman correlation test.