RXRA and acute myeloid leukemia: The fact that the enhanced differentiation effects of these and the previously described VDD/CA combinations in sensitive AML cell lines were associated with upregulation of both VDR and RXRα protein levels (Figure 7 and [17,35,43]) supports the positive role of the nuclear receptor to vitamin D in the potentiation of VDD-induced differentiation of AML cells by plant polyphenols.