M2‐like tumor‐associated macrophages‐secreted Wnt1 and Wnt3a promotes dedifferentiation and metastasis via activating β‐catenin pathway in thyroid cancer

Background Thyroid carcinoma (TC) has been a global issue for its rapid increasing incidence worldwide. Although most TC was not so aggressive with a good prognosis, treatment against anaplastic TC was relatively limited and the mechanisms are not well elucidated yet. Methods TC cell lines (IHH4 and TPC‐1) were used. Flow cytometry was used to identify the surface marker of M2‐like tumor‐associated macrophages (TAMs) from cell culture. Quantitative real‐time polymerase chain reaction, western blot analysis, immunostaining, and immunohistochemistry were used to detect the expression of Wnt1, Wnt3a, components of Wnt/β‐catenin pathway, and proliferation/epithelial–mesenchymal transition (EMT)‐related proteins. Alkaline phosphatase activity assay, colony formation assay, and transwell assay were used to examine the roles of Wnt1, Wnt3a, and β‐catenin pathway in cell dedifferentiation, proliferation, migration, and invasion of TC cells, respectively. Subcutaneous tumor growth was monitored in nude mice. Results Coculture with M2‐like TAMs facilitated dedifferentiation, proliferation, migration, and invasion in TC cells. EMT and proliferation‐related proteins were also promoted in cocultured TC cells. The level of Wnt1 and Wnt3a was increased in the coculture system. Block of Wnt1 or Wnt3a suppressed malignant behaviors in cocultured tumor cells. Furthermore, Wnt1 or Wnt3a knockdown inhibited Wnt/β‐catenin signaling pathway, and suppressed EMT and proliferation‐related signals in cocultured tumor cells. Knockdown of Wnt1 or Wnt3a inhibited tumor growth in xenograft model. Conclusion M2‐like TAMs promoted dedifferentiation, proliferation, and metastasis of TC by Wnt1 and Wnt3a secretion and ensuing β‐catenin activation.