PPARD and cancer: PPAR beta/delta expression is often upregulated and promotes cancer progression in many major human cancers such as colon, lung, breast, and gastric cancers [70–73], which suggests a crucial role of PPAR beta/delta in cancer cells even though there exist some conflicting studies indicating that the functional role of PPAR beta/delta in tumorigenesis or carcinogenesis still remains highly controversial [74–77] and dependent on specific tumor or cancer cell types.