RESUMEN
BACKGROUND AND OBJECTIVES: MicroRNAs (miRNAs) are small, noncoding RNAs that are involved in carcinogenesis through postranscriptional gene regulatory activity. Few studies have focused on the detection of miR-21 in serum rather than in tissue. The current study aimed to measure serum miR-21 expression levels and to evaluate their association with the outcome of colorectal cancer (CRC). METHODS: Blood samples were collected from 102 CRC patients undergoing surgery with curative intent. The expression levels of miR-21 were measured using a quantitative reverse transcription polymerase chain reaction (qRT-PCR). The results were analysed to assess the relationship between serum miR-21 levels and patient survival. RESULTS: A univariate analysis revealed that lower expression levels of serum miR-21 were associated with higher local recurrence (P = 0.025) and mortality (P = 0.029). A logistic regression analysis demonstrated that the relative overexpression of miR-21 (expression > 1) was associated with a 51% reduction in the risk of recurrence. A Cox regression analysis identified miR-21 expression as an independent predictor of survival (P = 0.048); a relative increase in miR-21 expression (>1) was associated with a 50% reduction in the risk of mortality. CONCLUSION: The expression level of serum miR-21 correlates with the recurrence and mortality of CRC patients. Our results suggest that circulating serum miR-21 is a promising prognostic tumour marker, and they highlight the potential clinical utility of miR-21 expression as a prognostic marker for CRC prognosis.