THE MECHANISM OF SMAD4 INHIBITING EMT AND METASTASIS OF COLORECTAL CANCER

Guangwei Zheng¹, Jiantao Zheng², Zhipeng Fang¹, Yi Zhou¹, Zhenlv Lin^{1, *}

¹Departments of Surgical Emergency, The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian 350005, China - ²Departments of Gastrointestinal Surgery, The First Affiliated Hospital of Fujian Medical University, Fuzhou, Fujian 350005, China

Introduction: To explore the role of Smad4 silencing in epithelial-mesenchymal transition (EMT) of colorectal cancer (CRC) cells and its possible involvement in invasion and metastasis signaling pathways. 

Materials and methods: CRC SW480 cells were transfected with lentiviral particles containing resistant control shRNA and Smad4 shRNA, and the transfected cells were divided into Smad4 silencing group (shRNA-Smad4) and blank control group (NC). Smad4 protein and mRNA levels were determined by western blot and real-time quantitative polymerase chain reaction (RT-qPCR). The cells were treated with 5 ng/ml TGF-β1 for 0 and 48 h, and cell migration and invasion in vitro were measured by wound healing and Transwell assays, respectively. The PCR was used to determine the levels of EMT-related proteins and MMP-9 protein and mRNA. 

Results: Compared with the control group, Smad4 protein and mRNA levels in Smad4-silenced cells were significantly reduced (P<0.05), and a stable Smad4-silenced cell line was successfully established. After the action of TGF-β1, compared with the control group, cell migration and invasion of the shRNA-Smad4 group were significantly enhanced; E-cadherin mRNA levels significantly decreased, and the mRNA levels of Vimentin, Snail, Twist1 and MMP-9 significantly increased (P<0.05). 

Conclusion: Smad4 silencing can promote EMT of CRC SW480 cells, thereby enhancing cell invasion and metastasis, which may be related to the transcriptional regulation on Snail and Twist1 expression.