RXRA and cancer: In addition to its classical role as cell cycle promoter, cyclin D1 has been reported to be involved in cancer drug resistance by being suppressed by a miRNA (let-7b), to be essential for migration in macrophages [49, 50] and might be indirectly involved in monocytic differentiation via inhibition of PPAR-gamma function [31], as the PPAR-gamma/retinoid X receptor-alpha heterodimer in myelomonocytic cell lines is known to induce monocytic differentiation [32].