Mechanism of RET gene mediated EGFR signaling pathway on epithelial-mesenchymal transition, proliferation and apoptosis of papillary thyroid carcinoma cells

Y.-L. Zhao, B.-Q. Yuan, G.-S. Shen

Department of Endocrinology, Suizhou Hospital Affiliated to Hubei University of Medicine, Suizhou City, Hubei Province, P.R. China. 835282310@qq.com

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• Oncology

OBJECTIVE: To explore the mechanism of RET gene mediated EGFR signaling pathway on the epithelial-mesenchymal transition (EMT), proliferation and apoptosis of papillary thyroid carcinoma (PTC) cells.
PATIENTS AND METHODS: PTC TPC-1 cells and human normal thyroid follicular epithelial cells Nthy-ori 3-1 were collected to identify the expression of RET in PTC. Seven groups were divided according to different transfection protocols, including blank group, negative control group, si-RET group, oe-RET group, AG-490 group, NSC 228155 group, and si-RET + NSC 228155 group. After transfection, qRT-PCR was used to identify whether the transfection was successful or not. qRT-PCR and Western blot were performed to detect the mRNA and protein expressions of RET, EGFR signaling pathway related genes, and EMT related genes. Cell migration, invasion, proliferation and apoptosis abilities were further detected by CCK8, cell scratch, transwell and flow cytometry assays, respectively.
RESULTS: RET gene was highly expressed in PTC cells (p<0.05). Compared with blank group, oe-RET group and NSC 228155 group had activated EGFR signaling pathway manifesting in the increased expression of EGFR, p-Src, p-FAK, accelerated EMT showing in the increased expression of N-cadherin and Vimentin expression, but decreased E-cadherin expression, increased cell migration, invasion and proliferation, while decreased apoptosis (all p<0.05); si-RET group and AG-490 group had inhibited activation of EGFR signaling pathway, suppressed EMT, decreased cell migration, invasion and proliferation, while increased apoptosis (all p<0.05); while no evident difference was found in si-RET + NSC 228155 group (all p>0.05). Meanwhile, compared with si-RET group, si-RET + NSC 228155 group showed activated EGFR signaling pathway, accelerated EMT, increased abilities of cell migration, invasion and proliferation, while decreased apoptosis (all p<0.05).
CONCLUSIONS: RET gene is highly expressed in PTC acting as an oncogene. Silencing RET gene expression may inhibit the invasion and promote the apoptosis of PTC cells by inhibiting the activation of EGFR signaling pathway and mediating the process of EMT. It suggests that RET may offer the possibility of a promising therapeutic target for the treatment of PTC on the basis of the explored mechanism.

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