The Role of PPARs in MDR - a lesson from embryonic development.

One of the most important features of embryonic cells is their resistence to xenobiotics, which provides a natural protection for embryos against these potentially harmful molecules. In this way, embryo cells resemble cancer cells and thus understanding the basis of this phenomenon may contribute to overcoming the multi-drug-resistance (MDR) of some tumours. Peroxisome proliferator-activated receptors (PPARs) are steroid nuclear receptors that regulate diverse biological processes such as lipid and carbohydrate metabolism, development, differentiation, apoptosis, neoplastic transformation, inflammation and regeneration of tissues. Recently it has been found that they may also regulate the expression of some MDR proteins. In this article we summarise the main known relationships between some MDR pumps and three isoforms of PPAR receptors (PPAR-alpha, PPAR-beta/delta, PPAR-gamma). We hypothesize that regulation of MDR proteins by PPAR ligands in embryos could lead to the improvement of cancer treatment.