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Alternative splicing of the primary glucocorticoid receptor (GR) transcript, resulting in glucocorticoid receptor alpha GRalpha, glucocorticoid receptor beta GRbeta and glucocorticoid receptor gamma GRgamma, may influence glucocorticoid (GC) resistance in childhood leukemia. To test this hypothesis, we determined GRalpha/beta protein and GRalpha/beta/gamma mRNA expression levels in 43 initial acute lymphoblastic leukemia (iALL), 10 initial myeloid leukemia (iAML), 11 relapsed ALL (rALL) samples and one rAML sample. The results were correlated with in vitro GC resistance. GRalpha mRNA correlated with protein expression (rho=0.39-0.56, P<0.05), but the protein to mRNA ratio was median 2.2-fold lower in rALL than in iALL (P<0.05). GRbeta mRNA was median 137-fold lower than GRalpha mRNA and correlated with GRalpha mRNA expression (rho=0.71, P<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.

We have found that, in addition to Bcl-2 and Bax, the expression levels of apoptosis inducers (Bad, Bak) and inhibitors (Bcl-xL, Mcl-1) were highly variable in blasts from 78 children with newly diagnosed acute lymphoblastic leukemia (ALL). The patients were enrolled in the national study ALL-7 of the Dutch Childhood Leukemia Study Group. In contrast to Bcl-2 that inversely correlated with %S-phase cells and WBC, and was lower in T than in B-lineage ALL, the Bcl-2 family members were not found to be associated with features at presentation. These expression levels were also compared with drug resistance in in vitro MTT (methyl-thiazol-tetrazolium) assays for prednisolone, vincristine and asparaginase in 46 children. Protein expression levels of the Bcl-2 family were not found to correlate with in vitroresistance to the individual drugs or the combined drug resistance profile. In addition, neither peripheral blast reduction after 1 week of prednisone monotherapy nor long-term disease-free interval or survival showed a correlation with protein expression. Our results indicate that the anti-proliferative function of Bcl-2 dominates its anti-apoptotic function in ALL, but neither Bcl-2 nor the Bcl-2 family members gained prognostic information in the risk-adapted protocol ALL-7.