CXCL8/CXCR2 signaling mediates bone marrow fibrosis and is a therapeutic target in myelofibrosis.

Proinflammatory signaling is a hallmark feature of human cancer, including in myeloproliferative neoplasms (MPNs), most notably myelofibrosis (MF). Dysregulated inflammatory signaling contributes to fibrotic progression in MF; however, the individual cytokine mediators elicited by malignant MPN cells to promote collagen-producing fibrosis and disease evolution are yet to be fully elucidated. Previously, we identified a critical role for combined constitutive JAK/STAT and aberrant NF-κB proinflammatory signaling in MF development. Using single-cell transcriptional and cytokine-secretion studies of primary cells from patients with MF and the human MPLW515L (hMPLW515L) murine model of MF, we extend our previous work and delineate the role of CXCL8/CXCR2 signaling in MF pathogenesis and bone marrow fibrosis progression. Hematopoietic stem/progenitor cells from patients with MF are enriched for a CXCL8/CXCR2 gene signature and display enhanced proliferation and fitness in response to an exogenous CXCL8 ligand in vitro. Genetic deletion of Cxcr2 in the hMPLW515L-adoptive transfer model abrogates fibrosis and extends overall survival, and pharmacologic inhibition of the CXCR1/2 pathway improves hematologic parameters, attenuates bone marrow fibrosis, and synergizes with JAK inhibitor therapy. Our mechanistic insights provide a rationale for therapeutic targeting of the CXCL8/CXCR2 pathway among patients with MF.

2p15-p16.1 microdeletions encompassing and proximal to BCL11A are associated with elevated HbF in addition to neurologic impairment.

Elevated fetal hemoglobin (HbF) ameliorates the clinical severity of hemoglobinopathies such as ß-thalassemia and sickle cell anemia. Currently, the only curative approach for individuals under chronic transfusion/chelation support therapy is allogeneic stem cell transplantation. However, recent analyses of heritable variations in HbF levels have provided a new therapeutic target for HbF reactivation: the transcriptional repressor BCL11A. Erythroid-specific BCL11A abrogation is now actively being sought as a therapeutic avenue, but the specific impact of such disruption in humans remains to be determined. Although single nucleotide polymorphisms in BCL11A erythroid regulatory elements have been reported, coding mutations are scarcer. It is thus of great interest that patients have recently been described with microdeletions encompassing BCL11A. These patients display neurodevelopmental abnormalities, but whether they show increased HbF has not been reported. We have examined the hematological phenotype, HbF levels, and erythroid BCL11A expression in 3 such patients. Haploinsufficiency of BCL11A induces only partial developmental γ-globin silencing. Of greater interest is that a patient with a downstream deletion exhibits reduced BCL11A expression and increased HbF. Novel erythroid-specific regulatory elements in this region may be required for normal erythroid BCL11A expression, whereas loss of separate elements in the developing brain may explain the neurological phenotype.

Non-cancer uses of histone deacetylase inhibitors: effects on infectious diseases and beta-hemoglobinopathies.

After the approval of suberoylanilide hydroxamic acid (SAHA, vorinostat, Zolinza) for the treatment of cutaneous T cell lymphoma (CTCL), a number of HDAC inhibitors (HDACi) are currently in Phase II or III clinical trials (alone or in combination) for the treatment of a great number of tumors. In addition to these cancer uses, HDACi can be successfully used in non-cancer diseases. In this review we focused on the uses of HDACi in some infectious diseases and beta-hemoglobinopaties. In C. albicans cultures, HDACi increased the frequency of cell switching (a relevant virulence trait) in the white-to-opaque transition, reduced the azole trailing effect through reduction in azole-dependent upregulation of CDR and ERG genes, and inhibited the fluconazole-dependent resistance induction. Moreover, they inhibited germination in several strains, and caused 90% reduction in the adherence of C. albicans to human cultured pneumocytes. In HIV-1-infected cells, the treatment with HDACi reactivates the HIV-1 expression in latent cellular reservoirs. Thus, the use of HDACi as adjuvant to highly active antiretroviral therapy (HAART) can represent a new potential therapeutic strategy to eradicate the viral infection. A number of HDACi have been reported as active against P. falciparum infection. Two recent papers show some 2-aminosuberic acid-based compounds as well as a series of phenylthiazolyl suberoyl hydroxamates as very potent and selective antimalarial agents. Among the many agents capable to perform post-natal reactivation of fetal hemoglobin production, HDACi for their capacity to de-repress gamma-globin gene expression in adult red cell, are presently considered promising molecules for personalized therapy of beta-hemoglobinopathies.