Furthermore, we identified WDR4 as a potent protein which was low expressed and correlated with increased proliferation, reduced senescence and differentiation, and insufficient support for normal hematopoiesis in mesenchymal stromal cells from patients with JAK2V617F-positive essential thrombocythemia.
VEGF expression parallelled VEGFR-1 and resulted increased in Ph- MPNs (NCs: 0.08±0.04; ET: 0.13±0.06; PV: 0.29±0.2; PMF: 0.31±0.15) and higher in post-polycythaemic myelofibrosis and in the fibrotic stage of PMF than in the non-fibrotic phases of both diseases.
The comparison between the cytokine profiles of ET and PV patients showed a statistically significant increase of interleukin (IL)-4, IL-8, granulocyte macrophage-colony stimulating factor, interferon -γ, monocyte chemotactic protein -1, platelet derived growth factor-BB, and vascular endothelial growth factor in the ET group.
We found significantly higher levels of vascular endothelial growth factor (VEGF) and markedly decreased levels of placental growth factor in untreated patients with ET with respect to control subjects.
A haplotype analysis found that the GGT and TGT haplotypes had significantly different distributions between ET and controls (p = 0.041 and 0.041, respectively).
Among the twenty most up- and downregulated genes, ATOX1, DEFB122, GPX8, PRDX2, PRDX6, PTGS1, and SEPP1 were progressively upregulated from ET over PV to PMF, whereas AKR1B1, CYBA, SIRT2, TTN, and UCP2 were progressively downregulated in ET, PV and PMF (all FDR <0.05).
Moreover, significantly more mutated splicing genes (SF3B1, SRSF2 and U2AF1) were present in PMF (0·60 mutated genes/patient) compared to ET (0·15) while no mutations in splicing genes were found in PV.
Our results suggest that: (1) p53 gene mutations occur sporadically in the chronic phase of ET, independent of chemotherapy, and may contribute to the progression to the leukaemic phase in a limited number of ET patients; (2) the RAS genes family does not seem to be involved in the pathogenesis of ET, unlike other bcr/abl negative chronic myeloproliferative diseases (CMPDs).
These data suggested that disruptions of both genes are extremely rare in MPD in chronic phase and that loss of functions in the p53 gene could be involved in progression of MPD such as PV and ET.
These data indicate that inactivation of TP53 is a relatively frequent event associated with the blastic transformation of PV and ET and may be responsible for the tumor progression of these disorders.
JAK2- and CALR-mutated ET have significantly higher fraction of B cells with TLR4 expression when compared to triple-negative ET (p=0.019 and 0.02, respectively).
As compared to the published normal sequence of the TPO gene, one allelic base change in a non-coding region of intron 1 was found in all children with ET and ST, but this was reported as a common finding in normal subjects as well.
More importantly, we demonstrated that this MPL Y252H mutant confers increased TPO/MPL-mediated cell growth and increased cell survival upon cytokine withdrawal in BaF3 cells, indicating it is a disease-driving mutation and may contribute to the development of ET in vivo.
Polycythemia vera is mainly related to JAK2 mutations, whereas a wider mutational spectrum is detected in essential thrombocythemia (ET) with mutations in JAK2, the thrombopoietin (TPO) receptor (MPL), and the calreticulin (CALR) genes.
Although activating mutation in the TPO gene, which leads to overexpression of TPO mRNA, has been reported in familial thrombocythemia, these results suggest that TPO-c-Mpl system may not be directly linked to pathogenesis of sporadic ET.
PRV-1 (polycythemia rubra vera-1), TPO (thrombopoietin), and c-MPL (myeloproliferative leukemia virus oncogene) genes are candidate ET molecular markers because of their implication in the pathogenesis of ET.
Acquired mutations in the juxtamembrane region of MPL (W515K or W515L), the receptor for thrombopoietin, have been described in patients with primary myelofibrosis or essential thrombocythemia, which are chronic myeloproliferative disorders.
Acquired mutations in the juxtamembrane region of MPL (W515L or W515K), the receptor for thrombopoietin, have been reported in patients with primary essential thrombocythemia (ET) or primary myelofibrosis (PMF).