Recently, it has been shown that activation of PPARγ by J2 series cyclopentenone prostaglandins (cyPGs), especially 15-deoxy-D12,14-prostaglandin J2 (15d-PGJ2) or synthetic agents, such as antidiabetic thiazolidinediones, causes anti-proliferation, apoptosis, differentiation, and anti-inflammation of certain types of cancer cells [40]. This evidence concerns the gene PPARG and cancer.