Glucocorticoid receptor alpha, beta and gamma expression vs in vitro glucocorticod resistance in childhood leukemia.

0.0001). GRbeta could not be detected at the protein level. GRgamma accounted for a median of 2.8% (range 0.95-7.4%) of all GR transcripts. GRalpha (protein and mRNA) and GRbeta (mRNA) expressions or GRalpha/GRbeta ratios did not correlate with in vitro GC resistance in iALL, but GRgamma (mRNA) did (rho=0.52, P=0.007). These results suggest that GRbeta is not involved in GC resistance in childhood leukemia. The association between GRgamma expression and in vitro GC resistance in iALL and the decreased protein/mRNA ratio in rALL, a subgroup resistant to GCs, warrants further exploration

RXRs: collegial partners.

Retinoid X Receptors (RXR) were initially identified as nuclear receptors binding with stereo-selectivity the vitamin A derivative 9-cis retinoic acid, although the relevance of this molecule as endogenous activator of RXRs is still elusive. Importantly, within the nuclear receptor superfamily, RXRs occupy a peculiar place, as they are obligatory partners for a number of other nuclear receptors, thus integrating the corresponding signaling pathways. In this chapter, we describe the structural features allowing RXR to form homo- and heterodimers, and the functional consequences of this unique ability. Furthermore, we discuss the importance of studying RXR activity at a genome-wide level in order to comprehensively address the biological implications of their action that is fundamental to understand to what extent RXRs could be exploited as new therapeutic targets