1,25-Dihydroxy vitamin D3 inhibits the Ras-MEK-ERK pathway and regulates proliferation and apoptosis of papillary thyroid carcinoma.

Objective: To explore the effects of 1,25-dihydroxy vitamin D3 [1,25-(OH)D] on the proliferation and apoptosis of papillary thyroid carcinoma and to investigate its possible mechanism.

Materials And Methods: The papillary thyroid carcinoma cell line TPC-1 was cultured, and the cells were divided into control group, the 1,25-(OH)D group, and the 1,25-(OH)D + ML-098 (Ras agonist) group. Cell proliferation was observed by MTT. The colony formation viability of cells was detected by the plate cloning assay. Cell migration was observed by the scratch assay. Apoptosis was detected by flow cytometry. The expression of Ki67 and Caspase-3, and the activity of Ras-MEK-ERK pathway were detected by western blot.

Results: Compared with the Control group, the proliferation, colony formation and migration ability of cells in the drug group were significantly decreased. The number of apoptotic cells was significantly increased, the expression of Ki67 protein was decreased, and the expression of Caspase-3 protein was upregulated. The phosphorylation levels of Ras, p-ERK1/2, and p-MEK were decreased. Compared with the drug group, the cloning and migration biological activity of cells in the 1,25-(OH)D + ML-098 group was significantly enhanced (p < 0.05). The number of apoptotic cells was decreased, while the Ki67 protein level was increased. In addition, the Caspase-3 protein level was decreased, and the Ras-MEK-ERK level was also enhanced. Furthermore, the antitumor activity of 1,25-(OH)D was reversed by the Ras agonist ML-098.

Conclusion: 1,25-(OH)D can inhibit the activity and promote apoptosis of the papillary thyroid carcinoma cell line TPC-1, and its mechanism may be related to the inhibition of the Ras-MEK-ERK pathway activity, thus affecting the proliferation and expression of apoptosis-related proteins.