Abstract
MicroRNAs (miRNAs or miRs) have been advocated as potentially robust and highly stable biomarkers of diverse disease conditions including cancer. The primary aim of this study was two-fold: i) to profile the expression levels of selected mature miRNA signature genes, such as miR-145, miR-195, miR-29 and miR-92, in a paired-study design of 20 colorectal cancer (CRC) tissues from patients versus adjacent neoplasm-free mucosal tissues employing reverse transcription-quantitative polymerase chain reaction; and ii) to examine their expression level in the plasma of the same CRC patients in relation to the age-matched plasma of healthy controls. Statistically significant (P<0.01) increases in miR-29 (2.5) and miR-92 (2.6) were observed in CRC tissues compared with adjacent neoplasm-free mucosal tissues. Profiling of CRC plasma samples showed that the expression levels of circulating miR-29 and miR-92 were significantly higher (P<0.01) than in the age-matched normal plasma. By contrast, miR-145 and miR-195 exhibited significant (P<0.05) decreases in their mean expression levels in CRC tissue samples in relation to the normal tissues. The mean expression levels of miR-145 and miR-195 were significantly lower (P<0.05) in CRC plasma than the healthy controls. Distinct stage-dependent changes in the expression level of the four miRNA gene profiles were observed between stages II and IV plasma of CRC patients relative to the control plasma. Taken together, the results clearly reflect a similar trend for the four miRNA expression levels in tissue and plasma as well as the positive correlation in the levels of miRNAs in tissues and plasma. These findings may be useful to clarify the molecular mechanisms underlying colorectal carcinogenesis and to underscore the potential of the investigated miRNAs as novel early diagnostic biomarkers of CRC.