Calcitriol Inhibits Malignancy of Thyroid Cancer Cells by Inhibiting Anoikis Resistance via COX2/YAP1 Hippo Signaling

Abstract

Background: Thyroid cancer (TC) is the commonest carcinoma of the endocrine system. Calcitriol (Cal) can regulate the proliferation and differentiation of TC. Therefore, we aim to explore whether cyclooxygenase 2 (COX2) and hippo signaling are correlated with Cal treatment for TC. Methods: Human TC cell lines were treated with different concentrations of Cal for 24 h and transfected with overexpression plasmids of COX2 and Yes-associated protein 1 (YAP1) by lipofection. The following assays, namely, cell counting kit-8, colony formation, Transwell, and anoikis assays, were adopted to determine TC cells malignant phenotypes including viability, proliferation, migration/invasion, and anoikis. The expression location of YAP1 was detected by immunofluorescence staining. Quantitative real-time polymerase chain reaction or Western blot was used to quantify the messenger RNA (mRNA) or protein expression levels of examined genes in TC cells. Results: Cal inhibited viability, colony formation, migration, invasion and COX2 expression but promoted anoikis in TC cells. The translocation of YAP1 from the cytoplasm to the nucleus was blocked by Cal treatment. Meanwhile, Cal decreased the levels of B cell lymphoma-2 (Bcl-2), YAP1, transcriptional coactivator with postsynaptic density-95/discs large/zonula occludens-1-binding motif (TAZ), connective tissue growth factor (CTGF), cysteine-rich angiogenic inducer 61 (CYR61), SRY (Sex-Determining Region Y)-Box 9 (SOX9) and ankyrin repeat domain 1 (ANKRD1), but increased those of Bcl-2-associated X (Bax), phosphorylated (p)-large tumor suppressor kinase 1 (p-LATS1), p-macrophage stimulating 1/2 (MST1/2), and p-Yes-associated protein 1 (p-YAP1) in TC cells. However, overexpression of COX2 or YAP1 counteracted the effects of Cal on TC cells. Conclusions: Cal suppresses the proliferation and metastasis of TC cells by diminishing anoikis resistance via targeting COX2/YAP1 hippo signaling.