Glucocorticoid-induced glucocorticoid-receptor expression and promoter usage is not linked to glucocorticoid resistance in childhood ALL

Abstract

Glucocorticoid (GC) resistance is an adverse prognostic factor in childhood acute lymphoblastic leukemia (ALL), but little is known about causes of GC resistance. Up-regulation of the glucocorticoid receptor (GR) has been suggested as an essential step to the induction of apoptosis in leukemic cells. In this study we investigated whether baseline mRNA expression levels of the 5 different GR promoter transcripts (1A1, 1A2, 1A3, 1B, and 1C) or differences in the degree of regulation of the GR or GR promoter transcripts upon GC exposure are related to GC resistance. Therefore, mRNA levels of the 5 GR promoter transcripts and of the GR were measured by quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR; Taqman) technology in primary ALL cells prior to and after 3, 8, and 24 hours of prednisolone exposure. GR expression is induced upon GC exposure in primary ALL patient samples, which is opposite to what is found in tissues in which GCs do not induce apoptosis. GC resistance in childhood ALL cannot be attributed to an inability of resistant cells to up-regulate the expression of the GR upon GC exposure, nor to differences in GR promoter usage (at baseline and upon GC exposure). (Blood.

Levels of glucocorticoid receptor and its ligand determine sensitivity and kinetics of glucocorticoid-induced leukemia apoptosis

“…4 Both Btk and BAG3 have been shown to modulate apoptosis and tumor growth in B-lymphoid neoplastic cells. 2,3,5,6,8 We therefore investigated whether the two proteins interacted in human B-lymphoma cells of the DeFew line. Cells were stimulated with b-phenylethyl isothiocyanate (PEITC) that induces oxidative stress; total lysates were obtained, immunoprecipitated with an anti-Btk antibody and analyzed with an anti-BAG3 antibody in immunoblotting.…”

“…More recently, one study showed that a higher number of GR binding sites was associated with a larger percent change in absolute peripheral blood blasts after a 3-day treatment with corticosteroids 7 but others concluded that GC sensitivity is independent of basal GR expression and/or GR auto-induction in childhood ALL patients. 8 To assess the role of GR expression levels and GR autoinduction on GC sensitivity we generated an in vitro model in which GR expression and regulation can be experimentally controlled. To this end, we first derived GC-resistant derivatives of the GC-sensitive CEM-C7H2-2C8 T-ALL cell line (that constitutively expresses a reverse tetracycline-activated transactivator protein, rtTA) by selection culture in 10 -6 M dexamethasone.…”

An oncogenic role of miR-142-3p in human T-cell acute lymphoblastic leukemia (T-ALL) by targeting glucocorticoid receptor-α and cAMP/PKA pathways

“…Although GR mutation may cause resistance, mutations in leukemic patients are rare and may not have a main role in GC resistance. 38 Tissing et al 39 show that there is no difference in the degree of regulation of GR mRNA between GC-sensitive and GC-resistant leukemic samples upon GC exposure, indicating a possibility of posttranscriptional regulation of GR expression. Here, we demonstrate such possibility by miR-142-3p targeting the 3 0 -UTR of GR mRNA in T-ALL cells, including the Jurkat cell line.…”

Transcriptional control of the glucocorticoid receptor: CpG islands, epigenetics and more

“…Although 1A containing 8 transcripts correspond to only about 10% of all GR transcripts [42], their contribution to 9 the tissue-specific response to GC treatment was considered essential [16,24]. The 10 human promoter 1A also has a functional binding site for Interferon Regulatory Factors 11 (IRF-1 and IRF-2), however IFNγ stimulation of CEM-C7 cells did not increase 1A 12 transcript levels, nor did it alter their susceptibility to GC-mediated apoptosis [45].…”

“…Expression of the 1A transcripts appears to be limited to the 14 immune system in both humans and rodents. The human 1A3 transcript is widely 15 expressed in both acute lymphoblastic leukemia (ALL) cell lines and in children with this 16 malignancy [16,20,25,[41][42][43]. Similarly, exon 1I is used predominantly in T cells, 17…”