In vitro studies conducted in cancer cell lines derived from many tumors including breast cancer (89), lung cancer (90), colon (91), liposarcoma (92), hematopoietic cancer (93), glioma (94), hepatocarcinoma (95, 96), pancreatic cancer (97), thyroid cancer (98), and prostate cancer (99) have shown that PPAR-γ is often expressed in these cancer cells and that PPAR-γ activation exerts a growth inhibitory effect. This evidence concerns the gene PPARG and thyroid gland carcinoma.