Human breast cancer cells express PPARγ [158] and can be targeted, forexample, with TZD, and a range of other PPARγ ligands to induce differentiation andinhibition of cell growth both in vitro and in xenograft models, effects which can be enhanced bycotreatment with either retinoids, TGFβ or TNFα [110, 111, 113, 114, 130, 158–163].For example, PPARγ ligands plus selective retinoid ligandsconverge on targets, such as RARβ, which is known to act as a tumorsuppressor and is commonly silenced in malignancy [164]. Here, PPARG is linked to breast cancer.