PINX1 promotes malignant transformation of thyroid cancer through the activation of the AKT/MAPK/beta-catenin signaling pathway

Although thyroid cancer is the most prevalent endocrine malignancy, overall patients with thyroid cancer have a good long-term survival. However, a small percentage of patients with progressive thyroid cancer have poor outcomes, and the genetic drivers playing a key role thyroid cancer progression are mostly unknown. Here, we investigated the role of the PINX1 in thyroid cancer progression. Interestingly, PINX1 expression was significantly higher in ATC than in PTC in both patients and cell lines. When PINX1 was knockdown in ATC cells, cell proliferation rates, colony formation capacity, and cell cycle progression were significantly reduced. Furthermore, cell motility and the expression of EMT drivers were reduced by PINX1 downregulation. In contrast, the overexpression of PINX1 in PTC cells significantly increased those phenotypes of tumor progression, which demonstrates that PINX1 could promote tumor proliferation and malignant transformation in both PTC and ATC cells. To further understand whether PINX1 is also involved in the progression of PTC to ATC, we examined PI3K/AKT, MAPK, and beta-catenin signaling activation after PINX1 modulation. Decreased PINX1 expression reduced the levels of p-AKT, p-ERK, p-p38, and beta-catenin in ATC cells, but the increase of PINX1 expression upregulated the phosphorylation of AKT, ERK, and p38 and the levels of beta-catenin in PTC cells. These results were all confirmed in xenograft mouse tumors. Our findings suggest that PINX1 regulates thyroid cancer progression by promoting cell proliferation, EMT, and signaling activation, and support the hypothesis that PINX1 could be a prognostic marker and a therapeutic target of thyroid cancer.