To examine whether IGFBP7 is functionally involved in the development and progression of thyroid cancer, we used two undifferentiated human anaplastic thyroid carcinoma cell lines, ARO and FRO, both of which have undetectable levels of IGFBP7, to ectopically overexpress IGFBP7, and we employed one differentiated follicular human thyroid carcinoma cell line, WRO, which shows moderate IGFBP7 expression, to ectopically overexpress and knockdown IGFBP7 (Fig. 2a). Here, IGFBP7 is linked to thyroid cancer.