PPARD and neoplasm: Regarding mammary neoplasia, Yuan et al. [36] showed in transgenic animals that activation of PPARβ/δ in the mammary epithelium resulted in progressive histopathologic changes that culminated in the appearance of estrogen receptor- and progesterone receptor-positive and ErbB2-negative infiltrating ductal carcinomas after 12 months in transgenic animals, while treatment with GW501516 shortened the interval until tumor appearance to 5 months.