Investigation of MicroRNA-21 Expression Levels in Serum and Stool as a Potential Non-Invasive Biomarker for Diagnosis of Colorectal Cancer

Abstract

Background: Most cancer studies focus on exploring non-invasive biomarkers for cancer detection. In the present study, we sought to investigate the expression level of microRNA-21 (miR-21), as a potential diagnostic marker, in serum and stool samples from 40 patients with colorectal cancer (CRC) and 40 healthy controls.

Methods: Quantitative real-time RT-PCR was applied to determine the relative expression level of miR-21 in serum and stool. At the same time, the sensitivity and specificity of this marker was evaluated by receiver operating characteristic (ROC) curve analysis.

Results: miR-21 expression levels of serum and stool were up-regulated 12.1 (P<0.05, 95% CI: 5.774-34.045) and 10.0 (P<0.05, 95% CI: 0.351-16.260) times in CRC patients, respectively, when compared to the control group. The sensitivity and specificity of miR-21 was found to be 86.05% and 72.97%, respectively (an area under the ROC curve [AUC] of 0.783). The stool miR-21 level in CRC patients was much higher than that in the healthy controls, showing a sensitivity of 86.05% and a specificity of 81.08% (AUC: 0.829). The expression level of miR-21 in stool was able to significantly distinguish CRC tumor, node, metastasis stages III-IV from stages I-II, with a sensitivity and specificity of 88.1% and 81.6%, respectively (AUC: 0.872).

Conclusion: The results of this study indicated that miR-21 expression levels in serum and stool can be considered as a potential diagnostic biomarker for the diagnosis of CRC patients. However, more studies are required to confirm the validity of miR-21 as a valuable non-invasive diagnostic tool for CRC.

Keywords: Serum; Stool; miR-21; Biomarker; Colorectal Cancer (CRC).

Fig. 1

qPCR Melting Curve for serum miR-21 levels in CRC patients. The miR-21 amplicon shows a single peak, representing a pure, single amplicon.

Fig. 2

miR-21 expression level in serum and stool based on patients’ clinical TNM stages. Results of kruskal-wallis test show that A) Serum miR-21 levels represent no obvious increase in patients with stage IV, ascompared to those with stage III (P>0.05), while a significant increase was found between patients with stages I and II (P<0.05); B)The expression level of miR-21 in stool can be considered as a promising marker to distinguish TNM stages III and IV from stages I or II (P<0.05), while unable to discriminate stage III from stage IV (P>0.05).

Fig. 3

Receiver operating characteristic (ROC) curve analysis to evaluate serum and stool miR-21 expression levels for the detection of CRC patients. A) Serum miR-21 level for the detection of CRC patients; the area under the ROC curve (AUC): 0.783, Youden index: 0.590, sensitivity: 86.05%, and specificity: 72.97%; B) Stool miR-21 level for the detection of CRC patients, AUC: 0.829, Youden index: 0.671, sensitivity: 86.05%, and specificity: 81.08%; C)Serum miR-21 expression level for the detection of tumor, node, metastasis (TNM) stages in CRC patients, AUC: 0.794, Youden index: 0.617, sensitivity: 88.10%, and specificity: %73.68; D) Stool miR-21 expression level for the detection of TNM stages in CRC patients, AUC: 0.872, Youden index: 0.696, sensitivity: 88.10%, and specificity: 81.58%.