Prognostic implications of serum microRNA-21 in colorectal cancer

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).

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.

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.

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.