Exogenetic expression of miR-138 suppresses CRC cell metastasis in vivo. (A) Establishment of the stable cell lines overexpressing miR-138. The expression of miR-138 was markedly increased in the lentiviral vector-mediated miR-138-expressing stable cell line HCT116-miR138 compared with the control stable cell line HCT116-Control. **P < 0.05. (B) Representative lungs subjected to the indicated treatments. The metastatic nodules are indicated with arrows. (C) Representative results of hematoxylin and eosin staining of metastatic nodules in the lung are shown. Metastatic nodules are indicated with arrows. (D) Number of metastatic nodules in the lungs of mice. The nodules were examined under a microscope. **P < 0.01, n = 8.