Objective  To analyze the effect of collagen triple helix repeat containing 1 (CTHRC1) on the biological characteristics of the colorectal cancer cells and its possible regulatory mechanism.

  Methods  Real-time PCR was used to detect the mRNA levels of CTHRC1 by overexpression or inhibition of miR-520d-5P. Dual Luciferase assay was used to assess the binding of miR-520d-5P to the CTHRC1 3'-UTR. Western blot analysis was performed to detect the protein levels of CTHRC1 in 6 human colorectal cancer (CRC) cell lines and paired colorectal cancer tissues. Following the stable transfection of CTHRC1 in CRC cell lines, the proliferative and the invasive ability of CTHRC1 were analyzed by in vitro CCK-8 assay and invasion assay, respectively.

  Results  MiR-520d-5P expression in normal tissues was significantly higher than the paired cancer tissues (P < 0.001), and the CTHRC1 expression in cancer tissues was significantly higher than the paired normal tissues (P < 0.001), indicating a negative correlation between their expression. We also observed that the CTHRC1 protein levels were lower in the miR-520d-5P mimics group and higher in the miR-520d-5P inhibitor group. Dual Luciferase assay confirmed that miR-520d-5P targets the 3'-UTR of CTHRC1. In vitro CCK-8 assay demonstrated a decreased proliferation in CRC Cells (SW480, SW620) overexpressing CTHRC1. Results from the in vitro invasion assay showed that the cells transfected with CTHRC1 were significantly more invasive (P < 0.05). The results showed that protein expression of gene CTHRC1 in primary cancer tissues was significantly higher than the paired normal tissues (P=0.003).

  Conclusions  CTHRC1 protein expression is negatively regulated by miR-520d-5P in colorectal cancer. Furthermore, CTHRC1 enhances the invasiveness and decreases the proliferation of CRC cell lines.