Background and purpose: miRNA plays important roles in tumorigenesis. It has been reported that many kinds of serum miRNA serve as markers for tumor diagnosis and screening. This study aimed to detect the expression of serum miRNA-31 (miR-31) in colorectal cancer patients and to explore the effect of miR-31 on cell proliferation

apoptosis and cell cycle distribution. Methods: The expressions of miR-31 in 40 cases of colorectal cancer serum and 35 cases of the healthy control were examined by r

eal-time fluorescent quantitative polymerase chain reaction (RTFQ-PCR). The correlation between miR-31 expression and clinicopathological features of colorectal cancer (including age

gender

depth of infiltration

lymph node metastasis

clinical stage) were further analyzed. The miR-31 mimics

inhibitor and miR-control (negative control) were transfected into HCT116 cells. The effect of miR-31 on cell proliferation was evaluated by CCK-8 method. Flow cytometry was used to examine the change of cell apoptosis and cell cycle. Results: Relative expression of serum miR-31 was significantly increased in cancer patients compared with healthy controls (P0.01). Expression of serum miR-31 was higher in poorly differentiated carcinoma than that in well or moderately differentiated carcinoma (P0.05). No correlation was found between serum miR-31 expression and other clinicopathological variables. CCK 8 assay showed that after transfection with miR-31 mimics

the cell proliferation was increased

compared with miR-31 inhibitor and negative control group. Meantime

the apoptotic cell number was significantly decreased

particularly in late apoptosis. The cell number of G

1

stage was remarkably increased in miR-31 inhibitor group

compared with miR-31mimics and negative control group. Conclusion: The expression of serum miR-31 is higher in colorectal cancer. miR-31 can promote cell proliferation and inhibit the apoptosis of HCT116 cells. It might be a potential biomarker for colorectal cancer.