Detection of miR-92a and miR-21 in stool samples as potential screening biomarkers for colorectal cancer and polyps

The detection of molecular markers in stool samples is a potential strategy for colorectal cancer (CRC) screening. This study evaluated the feasibility of detecting miR-21 and miR-92a in stool samples of patients with CRC or polyps.The reproducibility of detection and stability of stool-based microRNA were evaluated. Stool samples were collected from 88 patients with CRC, 57 patients with colorectal polyps and 101 healthy controls. MiRNA levels in CRC tissues and stool samples were detected by real-time quantitative reverse transcription PCR. Stool miR-21 and miR-92a levels were compared before and after the removal of tumour or advanced adenoma.The study demonstrated that stool-based miRNA were stable with highly reproducible detection. The expression of miR-21 and miR-92a was significantly higher in CRC tissues compared with their adjacent normal tissues (p<0.0001). Patients with CRC had a significantly higher stool miR-21 level (p<0.01) and miR-92a level (p<0.0001) compared with normal controls. Stool miR-92a, but not miR-21, was significantly higher in patients with polyps than in controls (p<0.0001). At a cut-off value of 435 copies/ng of stool RNA, miR-92a had a sensitivity of 71.6% and 56.1% for CRC and polyp, respectively, and a specificity of 73.3%. In addition, the stool miR-92a level demonstrated a higher sensitivity for distal CRC than proximal CRC (p<0.05), and a higher sensitivity for advanced adenoma than minor polyps (p<0.05). Removal of tumour resulted in reduced stool miR-21 and miR-92a levels (p<0.01), and the removal of advanced adenoma resulted in a reduction of the stool miR-92a level (p<0.05).Stool miRNA are useful for screening CRC and polyps.