PPARD is located at chromosome 6p21.2, which is a site of gain in estrogen receptor-negative and high-risk breast cancers.39 However, PPARD appears to be expressed mainly in response to factors in the microenvironment such as glucocorticoids (Figure 3b), cytokines40 and signals that activate calcineurin.41 We found it was also increased by low extracellular glucose levels (Figures 3b and 4b) that cause ER stress (Figure 3d). This evidence concerns the gene ESR1 and breast cancer.