Metastatic phenotype is regulated by estrogen in thyroid cells

Background: Over 200 million people worldwide are affected by thyroid proliferative diseases, including cancer, adenoma, and goiter, annually. The incidences of thyroid malignancies are three to four times higher in women, suggesting the possible involvement of estrogen. Based on this observed sex bias, we hypothesize that estrogen modulates the growth and metastatic propensity of thyroid cancer cells. Methods: In this study, two thyroid cell lines (Nthy-ori 3-1 and BCPAP) were evaluated for the presence of estrogen receptor (ER) by Western blot analysis and estrogen responsiveness by using a cell proliferation assay. In addition, the effect of estradiol (E₂) on modulation of metastatic phenotype was determined by using in vitro adhesion, migration, and invasion assays. Results: Thyroid cells expressed a functionally active ER-α and ER-β as evidenced by 50-150% enhancement of proliferation in the presence of E₂. E₂ also enhanced adhesion, migration, and invasion of thyroid cells in an in vitro experimental model system that, based on our results, is modulated by β-catenin. Conclusion: Our data provide evidence that the higher incidence of thyroid cancer in women is potentially attributed to the presence of a functional ER that participates in cellular processes contributing to enhanced mitogenic, migratory, and invasive properties of thyroid cells. These findings will enable and foster the possible development of antiestrogenic therapy targeting invasion and migration, thus affecting metastatic propensity.