Circulating miR-221 directly amplified from plasma is a potential diagnostic and prognostic marker of colorectal cancer and is correlated with p53 expression

Background and Aim: Circulating miRNAs exist in serum and plasma and they can be used as a potential noninvasive molecular marker for colorectal cancer (CRC) diagnosis. The present study was to test the availability of direct amplification of miRNAs from plasma without RNA extraction, and to evaluate its clinical application value in CRC. Methods: Plasma miR‐21, miR‐221 and miR‐222 levels were determined in 103 CRC patients and 37 healthy normal controls by quantitative reverse transcription‐polymerase chain reaction. Immunohistochemical staining for p53, carcinoembryonic antigen (CEA), estrogen receptor (ER) and progesterone receptor (PR) was carried out in the same CRC patient cohort. The correlation between miR‐221 levels and protein levels of p53, CEA, ER and PR, clinicopathological features or overall survival was analyzed. Results: A standard curve shows a good linearity between the log of sample input and CT values over three orders of magnitude of plasma miR‐21, miR‐221 and miR‐222. ROC curve analysis reveals that the plasma levels of miR‐221 is a potential biomarker for differentiating CRC patients from controls. Kaplan–Meier curve assessment shows that the elevated plasma miR‐221 level is a significant prognostic factor for poor overall survival in CRC patients. The immunohistochemistry analysis demonstrates a significant correlation between plasma miR‐221 level and p53 expression. Conclusions: The direct amplification of plasma miR‐221 can be used as a potential noninvasive molecular marker for diagnosis and prognosis of CRC and is correlated with p53 expression.