RARA and leukemia: These factors include non-random genetic mutations producing chimeric RARα receptors with dominant negative function, such as the leukemia-associated PML-RARα and PLZF-RARα [9 and references within], RARα epigenetic silencing in epithelial cancer cells [10]–[13], and a defective intracellular level of RA consequent to defects of the retinol/RA metabolism/homeostasis [4], [14]–[17].