The expression of p53 in breast adipose stromal cells is downregulated by obesity-induced prostaglandin E2 (PGE2), which results in a local upregulation of aromatase activity and estrogen production [31], and estrogen receptor has also been demonstrated to downregulate p53 and cause tumor cell proliferation [31, 32]. The gene discussed is CYP19A1; the disease is obesity due to melanocortin 4 receptor deficiency.