Abstract: Objective To explore the expression levels of microRNA(miR)-514b-3p and miR-599 in the serum of patients with Colorectal Cancer (CRC), and to analyze their correlations with the clinicopathological characteristics and prognosis of the patients.Methods A total of 213 CRC patients diagnosed by pathology in our hospital from January 2019 to March 2022 were prospectively selected as the CRC group.Another 109 healthy individuals who underwent physical examinations during the same period were selected as the control group.According to the follow-up results, the patients were divided into the survival group (n=134) and the death group (n=79).Compare the expression levels of serum miR-514b-3p and miR-599 in each group of subjects; Compare the expression differences of miRNAs in CRC patients with different pathological features.The Kaplan-Meier curve and log-rank test were used to deeply explore the association between serum miRNAs expression and prognosis.the ROC Curve and the Area Under the Curve (AUC) were used to evaluate the predictive efficacy of miRNAs for CRC and its prognosis.Cox proportional Cox regression analysis was used to analyze the influencing factors related to the prognosis of CRC patients.Results The serum miR-514b-3p in the CRC group and the control group were 1.56 ±0.51 and 3.45±1.95 respectively, and miR-599 were 1.91±0.51 and 3.97±1.57 respectively.There was a statistically significant difference between the two groups (P<0.05).The expression levels of serum miR-514b-3p and miR-599 in CRC patients were closely related to tumor size, invasion depth, TNM stage, lymph node metastasis, distant metastasis, degree of differentiation and CEA (P<0.05).Compared with the survival group, the levels of serum miR-514b-3p and miR-599 in the death group were significantly decreased (P<0.05).The ROC results showed that the AUC of the combined prediction of CRC by miR-514b-3p and miR-599 was 0.986, which was significantly higher than that of miR-514b-3p (Z=3.921, P < 0.001) and miR-599 (Z=4.571, P<0.001) when used alone.The AUC of the combined prediction of the above indicators for the prognosis of CRC patients was 0.936, which was significantly higher than that of miR-514b-3p (Z=3.697, P<0.001) and miR-599 (Z=5.217, P<0.001) when used alone.The Kaplan-Meier survival curve results showed that there were statistically significant differences between the high-expression and low-expression groups of each index (log-rank χ2=57.386, 46.790, P<0.05).Multivariate Cox regression analysis indicated that lower levels of miR-514b-3p and miR-599 were both independent risk factors for poor prognosis in CRC patients (P<0.05).Conclusion The expression levels of miR-514b-3p and miR-599 in the serum of CRC patients were significantly decreased.Both can be used as independent molecular markers for evaluating the pathological progression of patients and predicting poor prognosis, and the combined detection has higher clinical diagnostic and prognostic predictive value.

Key words: colorectal cancer; microRNA-514b-3p; microRNA-599; prognosis; clinicopathologic feature