PPARD and lung cancer: In this context, it is interesting to note that in bone marrow, CYP26B1 functions as a critical regulator of all-trans retinoic acid levels essential for primitive hematopoietic cells to undergo differentiation [34], as well as of the regulatory role of TNFRSF10D in TRAIL-induced cell apoptosis [35], and that polymorphisms of PPARD are related to survival in lung cancer patients [36].