[71] where ATRA significantly inhibited the growth of Calu-6 and H460 cells. While this was accompanied by induction of RARβ expression, it had little effect on the growth of H292, SKMES-1 and H661 lung cancer cell lines in which RARβ expression was not induced. In a recent study by Zhang et al. [72], human mesenchymal stem cells were used as a model for stem cell differentiation and together with a number of cancer cell lines, the cellular consequences of modulating RXRα during cell differentiation was determined, in addition to potential connections with the carcinogenesis process. This evidence concerns the gene RARB and lung cancer.