Abstract
Vitamin D and the vitamin D receptor (VDR) complex have been reported to inhibit the growth of several types of tumor; however, their function in papillary thyroid cancer (PCT) remains unknown. In addition, the Wnt/β‑catenin signaling pathway was discovered to serve a critical role in the pathology of PCT. Therefore, the present study aimed to determine the role of the VDR and its association with Wnt/β‑catenin signaling in vitamin D‑treated PTC cells. VDR expression was detected in human PTC cells (including MDA‑T120, MDA‑T85, SNU‑790 and IHH4 cells) and thyroid follicular cells (Nthy‑ori 3‑1 cells). SNU‑790 and IHH4 cells were infected with KD‑VDR or negative control (KD‑NC) lentiviruses, treated with 1,25(OH)2D3 (the active form of vitamin D), and subsequently referred to as the KD‑VDR&vitD and KD‑NC&vitD groups, respectively. Additionally, PTC cells infected with KD‑NC and not treated with 1,25(OH)2D3 were used as the normal control and referred to as the KD‑NC group. VDR mRNA and protein expression levels were increased in MDA‑T120, SNU‑790 and MDA‑T85 cells compared to Nthy‑ori 3‑1 cells, whereas in IHH4 cells, VDR mRNA and protein expression levels were similar to Nthy‑ori 3‑1 cells. In SNU‑790 and IHH4 cells, cell proliferation and invasion were decreased in the KD‑NC&vitD group compared with the KD‑NC group, but increased in the KD‑VDR&vitD group compared with the KD‑NC&vitD group. Cell apoptosis was increased in the KD‑NC&vitD group compared with the KD‑NC group, and decreased in the KD‑VDR&vitD group compared with the KD‑NC&vitD group. Furthermore, the expression levels of Wnt family member 3 and catenin β1 were decreased in the KD‑NC&vitD group compared with the KD‑NC group, but increased in the KD‑VDR&vitD group compared with the KD‑NC&vitD group. In conclusion, the present study revealed that VDR‑KD attenuated the antiproliferative, pro‑apoptotic and anti‑invasive effects of vitamin D in PTC by activating the Wnt/β‑catenin signaling pathway.