[ß-catenin nuclear translocation represses thyroid cancer stem cells differentiating into cells with sodium-iodine symporter functional expression].

Objective: To confirm whether ß-catenin nuclear translocation in thyroid cancer stem cells can differentiate into thyroid cancer cells without functional membrane expression of sodium-iodine transporter (NIS) and be resistant to iodide 131 treatment. Methods: Thyroid cancer stem cells were firstly isolated as a side population (SP) from human thyroid cancer cell line FTC133. The SP cells from FTC133 were transfected with ß-catenin, and then differentiated. The cells were further collected for Western blot, Transwell and MTT assay to investigate the epithelial-mesenchymal transition (EMT) characteristics, tumor growth, invasion, and iodine uptake potency in vitro. Functional NIS expression and iodide uptake in differentiated cells were detected with immunofluorescent staining and iodide uptake assay, respectively. Subcutaneous severe combined immunodeficient (SCID) mice tumor model was induced with differentiated cancer cells to explore the in vivo effect of radioiodine treatment. Further immunohistochemical staining was performed to reveal the changes of functional proteins involved in tumor radioiodine treatment. Results: Side population was isolated from FTC133 accounting for about 0.03%, with high expression of stem cell markers and decreased expression of differentiated cell markers. Western blot showed prominent EMT phenotype in the differentiated cells from ß-catenin transfected stem cell model, with absence of epithelial expression of E-cadherin and cytokeratin 18, as well as abnormal expression of vimentin,fibronectin and urokinase-type plasminogen activator. Moreover,compared with cells differentiated from untransfected or empty plasmid transfected stem cells, in vitro proliferation markedly increased 85.4% and 81.0%, respectively (both P<0.01); while in vitro invasion augmented 78.8% and 84.4%, respectively (both P<0.01). Immunofluorescent staining identified that, after transfected with ß-catenin, differentiated cells underwent ß-catenin nuclear translocation and NIS localization transferred from membrane to plasma, compared with cells from untransfected or empty plasmid transfected stem cells. Cell iodide uptake in vitro decreased about 52.8% and 45.2%, respectively (both P<0.01). Furthermore, in vivo experiment further demonstrated that, cells differentiated from ß-catenin transfected stem cells were found with much higher tumor proliferation,tumor growth rate and larger tumor mass after radioiodine 131 treatment (both P<0.05). Conclusion: Induction of ß-catenin nuclear translocation in stem cells may generate differentiated thyroid cancer cells that are not sensitive to radioiodine treatment.

[All-trans retinoic acid improves iodine uptake of thyroid cancer cells via repressing transcriptional activity of ß-catenin].

OBJECTIVE: To determine whether all-trans retinoic acid (ATRA) could improve iodine uptake via repressing transcriptional activity of ß-catenin in thyroid cancer cells. METHODS: Three kinds of treatment models were firstly established with alcohol, ATRA, and transfection of ß-catenin shRNA in undifferentiated human thyroid cancer cell line-SW1736.Then the expressions of sodium iodide symporter (NIS), ß-catenin and its regulating factors, epithelial-mensechymal transition (EMT)-phenotype, invasion and metastasis associated proteins were further measured in above three cell models.After that, the influence of ATRA on the functional expression of NIS, iodine uptake potency, tumor growth curve and treatment effect inducing by radioactive iodine was comparatively analyzed in vitro and in vivo trials. RESULTS: After treated with ATRA, transcriptional activity of ß-catenin decreased by downregulating phosphorylation of ß-catenin Ser45, Y654 and GSK-3ß Ser9. Additionally, ATRA effectively upregulated the protein level of NIS, and reversed EMT phenotype in alcohol treated cells, with absence in epithelial expression of E-cadherin and cytokeratin 18, as well as abnormal expression of Vimentin, urinary plasminogen activator (uPA), uPAR and Fibronectin.Compared with alcohol-treated group, both in vitro proliferation and invasion potential of ATRA treated cells markedly decreased (all P<0.05), and iodine uptake in vitro increased about 3.5-folds (P=0.007). In ATRA-treated animal model, tumor growth potential and tumor mass were significantly inhibited by radio-iodine ((131)I) treatment (all P<0.05). CONCLUSIONS: ATRA can increase functional expression of NIS via downregulating transcriptional activity of ß-catenin and promote isotope sensitivity to radio-iodine in human undifferentiated thyroid cancer.