Insulin‐like growth factor 1 promotes proliferation and invasion of papillary thyroid cancer through the STAT3 pathway

BACKGROUND: Papillary thyroid cancer (PTC) is a kind of thyroid cancer. Previous studies showed that insulin‐like growth factor‐1 (IGF1) plays an important role in tumorigenesis, development, invasion, and metastasis. However, the function of IGF1 in PTC progression remains unclear. METHODS: Seventy‐three pairs of PTC tissue specimens and adjacent normal specimens form and normal cell line and PTC cell lines were collected in this study. The immunohistochemistry (IHC) assay was performed to test the expression of IGF1. The RNA isolation and quantitative real‐time PCR assays (qRT‐PCR assays) and Western blot analysis were used to test mRNA and protein expression. Cell proliferation assay, EdU assay, flow cytometry assay, wound healing assay, and Transwell invasion assay were performed to test cell proliferation, invasion, and apoptosis. RESULTS: We found that the expression of IGF1 in PTC tissue samples was higher than that in adjacent normal specimens and was significantly associated with tumor size, TNM staging, and lymph node metastasis. Furthermore, IGF1 treatment significantly increased cell viability in a dose‐dependent manner. EdU assay also demonstrated the effect of IGF1 on the proliferation of BCPAP and TPC1 cells. Moreover, IGF1 treatment effectively increased the invasive capacity of BCPAP and TPC1 cells. More importantly, IGF1 treatment could significantly enhance the phosphorylation of STAT3 in BCPAP and TPC1 cells. Moreover, cryptotanshinone (Cryp) treatment reversed the effect of IGF1 treatment on cell viability and invasion of BCPAP and TPC1 cells. CONCLUSION: Collectively, IGF1 promotes proliferation and invasion of PTC progression through the STAT3 signaling pathway.