The dominant negative β isoform of the glucocorticoid receptor is uniquely expressed in erythroid cells expanded from polycythemia vera patients

Abstract

Glucocorticoid receptor (GR) agonists increase erythropoiesis in vivo and in vitro.To clarify the effect of the dominant negative GR␤ isoform (unable to bind STAT-5) on erythropoiesis, erythroblast (EB) expansion cultures of mononuclear cells from 18 healthy (nondiseased) donors (NDs) and 16 patients with polycythemia vera (PV) were studied. GR␤ was expressed in all PV EBs but only in EBs from 1 ND. The A3669G polymorphism, which stabilizes GR␤ mRNA, had greater frequency in PV (55%; n ‫؍‬ 22; P ‫؍‬ .0028) and myelofibrosis (35%; n ‫؍‬ 20) patients than in NDs (9%; n ‫؍‬ 22) or patients with essential thrombocythemia (6%; n ‫؍‬ 15). Dexamethasone stimulation of ND cultures increased the number of immature EBs characterized by low GATA1 and ␤-globin expression, but PV cultures generated great numbers of immature EBs with low levels of GATA1 and ␤-globin irrespective of dexamethasone stimulation. In ND EBs, STAT-5 was not phosphorylated after dexamethasone and erythropoietin treatment and did not form transcriptionally active complexes with GR␣, whereas in PV EBs, STAT-5 was constitutively phosphorylated, but the formation of GR/STAT-5 complexes was prevented by expression of GR␤. These data indicate that GR␤ expression and the presence of A3669G likely contribute to development of erythrocytosis in PV and provide a potential target for identification of novel therapeutic agents. (Blood. 2011;118(2):425-436) IntroductionPolycythemia vera (PV) is a Philadelphia chromosome-negative myeloproliferative neoplasm (MPN) characterized by increased production of erythroid cells. 1 As in other MPNs, PV is associated with a gain-of-function mutation (JAK2V617F) of the JAK2 gene. [2][3][4] JAK2 is the first transduction element of many hematopoietic growth factor receptors, including the receptor for erythropoietin, the primary growth factor that controls erythroid cell production. 5 The observation that inhibition of JAK2V617F abrogates erythropoietin-independent growth of erythroid progenitors suggested the hypothesis that in PV, increased erythroid production is caused by constitutive activation of erythropoietin receptor signaling (STAT-5 and/or PI3K/Akt). [6][7][8] Because low and high levels of STAT-5 activation favor maturation and proliferation, respectively, in normal hematopoietic cells, 9,10 the presence of the JAK2V617F mutation in PV may increase the intrinsic proliferative potential of erythroid cells by increasing This concept is indirectly supported by the observation that hematopoietic progenitor cells from PV patients generate greater numbers of erythroblasts (EBs) in liquid culture than cells from healthy (nondiseased) donors (NDs). 7,12 In addition to erythropoietin, erythroid proliferation is also controlled by nuclear receptors such as the glucocorticoid receptor (GR). Evidence for this regulatory role is provided by clinical observations and in vitro studies of cultured EBs. Patients may develop erythrocytosis as the first manifestation of Cushing syndrome. 13 In addition, 50% of patients with Diamond-...

Glucocorticoid Receptor β Stimulates Akt1 Growth Pathway by Attenuation of PTEN

“…The impedimentary action of GR␤ on GR␣ was recently demonstrated by Varricchio et al in polycythemia vera (PV) patients, which have increased erythroid cell growth (42). This study found that PV patients have a polymorphism in the human GR gene that leads to the stabilization of the GR␤ mRNA, resulting in higher protein levels.…”

Increased frequency of the glucocorticoid receptor A3669G (rs6198) polymorphism in patients with Diamond-Blackfan anemia

“…7 In this issue of Blood, we describe that the frequency of the A3669G SNP is increased in polycythemia vera (PV; 55%) and that erythroblasts expanded in vitro from these patients express GR␤ and do not respond to corticosteroids. 8 Based on these and other observations, we suggest that GR␤ may represent a "host genetic modifier" that in combination with JAK2 mutations determines erythrocytosis.…”

“…10 Clinical management of DBA includes corticosteroid therapy and for the 40% of patients who, for reasons still to be understood, do not respond to corticosteroids, red cell transfusions and/or hematopoietic stem cell transplantation. 11 The increased frequency of the A3669G SNP in PV patients whose erythroid cells did not respond to corticosteroids in vitro 8 prompted us to determine the frequency of this SNP in DBA patients. A total of 58 patients were analyzed, of whom 86% (n ϭ 50) presented mutations in RPL5, RPL11, RPS19, and RPS26.…”

“…In the case of 44 DBA patients, the frequency of the SNP was detected by genomic PCR amplification followed by direct sequencing. 8 All the DBA patients and the nondiseased donors were also genotyped by restriction fragment length polymorphism analyses using previously published amplification primers 5 and SwaI. Genotype distributions and allele frequencies were analyzed according to the Fisher exact test and 2 , respectively.…”

EpCAM- AN OLD CANCER ANTIGEN, TURNED ONCOGENIC RECEPTOR AND ITS TAGETING IMMUNOTHERAPY

“…Oncogenic receptor AR variants（Pca) [24][25] ; ER pro-neoplastic signaling [26][27] , neoplastic ESR1-CCDC170 fusion(also oncogenic receptor ERalpha fusion)（breast cancer) 7,28 ;GRβ aberrant signaling（Cushing's disease,erythrocytosis, GR + breast cancer, Nelson's syndrome) [29][30][31] ; FSH/FSH receptor oncogenic signaling（preneoplastic ovarian surface epithelial cells)…”