Hydroxyurea-inducible SAR1 gene acts through the Giα/JNK/Jun pathway to regulate γ-globin expression

Hydroxyurea inhibits proliferation and stimulates apoptosis through inducible nitric oxide synthase in erythroid cells

Hydroxyurea (hydroxycarbamide, HU) arrests cells in the S-phase by inhibiting ribonucleotide reductase and DNA synthesis, significantly contributing to the release of nitric oxide (NO). We investigated the involvement of inducible NO synthase (NOS2) in the cytostatic effect of HU using in vitro shRNA-induced knockdown of the NOS2 transcript (NOS2kd) or a specific NOS2 inhibitor (1400W) in human erythroleukemic HEL92.1.7 cells, as well as murine erythroid progenitors (mERPs) from HU-treated wild-type (WT) and Nos2 knockout (Nos2-/-) mice. Over the long-term, HU increased NOS2 expression in HEL92.1.7 cells (via nuclear factor kappa B [NFκB] signaling) and in mERP. In the short-term, HU increased the activity of human recombinant and erythroleukemic cell-derived NOS2, as confirmed by NO metabolite nitrite/citrulline production. In silico molecular docking predicted that HU binds to the NOS2 active site and substrate L-arginine via hydrogen bonds. Molecular dynamics simulations showed reduced rigidity of the NOS2 active site upon interaction with HU, indicating stabilization of the enzyme-substrate complex. Both 1400W and NOS2kd prevented the in vitro reduction in proliferation and induction of apoptosis in HEL92.1.7 cells by HU. NOS2kd preferentially blocked early apoptosis and HU-induced S-phase arrest in HEL92.1.7 cells. The HU-induced decrease in proliferation and stimulation of early apoptosis in mERP were prevented in Nos2-/- mice and by 1400W in WT mice. This study demonstrated that HU induces NOS2 activity through direct interaction and increased protein expression via NFκB signaling. Moreover, NOS2 mediates the HU-induced inhibition of proliferation and stimulation of apoptosis in erythroid cells.

SAR1A Induces Cell Growth and Epithelial-Mesenchymal Transition Through the PI3K/AKT/mTOR Pathway in Head and Neck Squamous Cell Carcinoma: An In Vitro and In Vivo Study

OBJECTIVES

Head and neck squamous cell carcinoma (HNSCC) ranks sixth globally, with a 50% five-year survival rate. SAR1A exhibits high expression levels in various tumor types, yet its specific role in HNSCC remains to be clarified.

METHODS

In vitro assays, such as CCK8, EdU, colony formation, wound-healing, transwell, and Western blotting analyses, as well as in vivo assays, such as tumor xenografts and lung metastasis models, were conducted to evaluate the impacts of SAR1A on HNSCC proliferation, migration, and invasion. Transcriptome sequencing and KEGG enrichment pathway analysis revealed evident alterations in the PI3K/AKT/mTOR(PAM) pathways. LY294002 (a PI3K/AKT inhibitor) was used to investigate the role of the PAM pathway in proliferation, migration, and invasion in HNSCC.

RESULTS

Univariate and multivariate Cox regression were conducted to screen SAR1A as a gene prognostic biomarker in HNSCC, and it was validated in the Cancer Genome Atlas (TCGA) database. Functional assays demonstrated that the depletion of SAR1A leads to suppressed proliferation, migration, and invasion of HNSCC cells. This is accompanied by a decrease in the expression of epithelial-mesenchymal transition (EMT)-related markers in HNSCC cell lines. In addition, the diminished capacities of proliferation, migration, and invasion observed in SAR1A knockdown cells were reversed upon the overexpression of SAR1A. Furthermore, RNA-seq and KEGG enrichment analysis demonstrated a significant alteration in the PAM pathway following SAR1A knockdown. LY294002 effectively mitigated the increased proliferation, migration, and invasion induced by SAR1A overexpression.

CONCLUSIONS

SAR1A facilitates HNSCC proliferation and EMT via the PI3K/AKT/mTOR pathway.

Ginsenoside Rg1 promotes fetal hemoglobin production in vitro: A potential therapeutic avenue for β-thalassemia

β-thalassemia, a globally prevalent genetic disorder, urgently requires innovative treatment options. Fetal hemoglobin (HbF) induction stands as a key therapeutic approach. This investigation focused on Ginsenoside Rg1 from the Panax genus for HbF induction. Employing K562 cells and human erythroid precursor cells (ErPCs) derived from neonatal cord blood, the study tested Rg1 at different concentrations. We measured its effects on γ-globin mRNA levels and HbF expression, alongside assessments of cell proliferation and differentiation. In K562 cells, Rg1 at 400 μM significantly increased γ-globin mRNA expression by 4.24 ± 1.08-fold compared to the control. In ErPCs, the 800 μM concentration was most effective, leading to an over 80% increase in F-cells and a marked upregulation in HbF expression. Notably, Rg1 did not adversely affect cell proliferation or differentiation, with the 200 μM concentration showing an increase in γ-globin mRNA by 2.33 ± 0.58-fold, and the 800 μM concentration enhancing HbF expression by 2.59 ± 0.03-fold in K562 cells. Our results underscore Rg1's potential as an effective and safer alternative for β-thalassemia treatment. By significantly enhancing HbF levels without cytotoxicity, Rg1 offers a notable advantage over traditional treatments like Hydroxyurea. While promising, these in vitro findings warrant further in vivo exploration to confirm Rg1's therapeutic efficacy and to unravel its underlying mechanistic pathways.

Kruppel-like factor 1-GATA1 fusion protein improves the sickle cell disease phenotype in mice both in vitro and in vivo

Sickle cell disease (SCD) and β-thalassemia are among the most common genetic disorders worldwide, affecting global health and mortality. Hemoglobin A2 (HbA2, α2δ2) is expressed at a low level in adult blood due to the lack of the Kruppel-like factor 1 (KLF1) binding motif in the δ-globin promoter region. However, HbA2 is fully functional as an oxygen transporter, and could be a valid antisickling agent in SCD, as well as a substitute for hemoglobin A in β-thalassemia. We have previously demonstrated that KLF1-GATA1 fusion protein could interact with the δ-globin promoter and increase δ-globin expression in human primary CD34+ cells. We report the effects of 2 KLF1-GATA1 fusion proteins on hemoglobin expression, as well as SCD phenotypic correction in vitro and in vivo. Forced expression of KLF1-GATA1 fusion protein enhanced δ-globin gene and HbA2 expression, as well as reduced hypoxia-related sickling, in erythroid cells cultured from both human sickle CD34+ cells and SCD mouse hematopoietic stem cells (HSCs). The fusion proteins had no impact on erythroid cell differentiation, proliferation, and enucleation. Transplantation of highly purified SCD mouse HSCs expressing KLF1-GATA1 fusion protein into SCD mice lessened the severity of the anemia, reduced the sickling of red blood cells, improved SCD-related pathological alterations in spleen, kidney, and liver, and restored urine-concentrating ability in recipient mice. Taken together, these results indicate that the use of KLF1-GATA1 fusion constructs may represent a new gene therapy approach for hemoglobinopathies.

Transmembrane Protein ANTXR1 Regulates γ-Globin Expression by Targeting the Wnt/β-Catenin Signaling Pathway

Reactivation of fetal hemoglobin (HbF, α2γ2) alleviates clinical symptoms in patients with β-thalassemia and sickle cell disease, although the regulatory mechanisms of γ-globin expression have not yet been fully elucidated. Recent studies found that interfering with the expression of the membrane protein ANTXR1 gene upregulated γ-globin levels. However, the exact mechanism by which ANTXR1 regulates γ-globin levels remains unclear. Our study showed that overexpression and knockdown of ANTXR1 in K562, cord blood CD34⁺, and HUDEP-2 cells decreased and increased γ-globin expression, respectively. ANTXR1 regulates the reactivation of fetal hemoglobin (HbF, α2γ2) in K562, cord blood CD34⁺, and adult peripheral blood CD34⁺ cells through interaction with LRP6 to promote the nuclear entry of β-catenin and activate the Wnt/β-catenin signaling pathway. The overexpression or knockdown of ANTXR1 on γ-globin and Wnt/β-catenin signaling in K562 cells was reversed by the inhibitor XAV939 and the activator LiCl, respectively, where XAV939 inhibits the transcription of β-catenin in the Wnt pathway, but LiCl inhibits GSK3-β. We also showed that the binding ability of the rank4 site in the transcriptional regulatory region of the SOX6 gene to c-Jun was significantly increased after overexpression of ANTXR1 in K562 cells. SOX6 protein expression was increased significantly after overexpression of the c-Jun gene, indicating that the transcription factor c-Jun initiated the transcription of SOX6, thereby silencing γ-globin. Our findings may provide a new intervention target for the treatment of β-hemoglobinopathies.

Pharmacological Induction of Fetal Hemoglobin in β-Thalassemia and Sickle Cell Disease: An Updated Perspective

A significant amount of attention has recently been devoted to the mechanisms involved in hemoglobin (Hb) switching, as it has previously been established that the induction of fetal hemoglobin (HbF) production in significant amounts can reduce the severity of the clinical course in diseases such as β-thalassemia and sickle cell disease (SCD). While the induction of HbF using lentiviral and genome-editing strategies has been made possible, they present limitations. Meanwhile, progress in the use of pharmacologic agents for HbF induction and the identification of novel HbF-inducing strategies has been made possible as a result of a better understanding of γ-globin regulation. In this review, we will provide an update on all current pharmacological inducer agents of HbF in β-thalassemia and SCD in addition to the ongoing research into other novel, and potentially therapeutic, HbF-inducing agents.

Molecular Determination of Vascular Endothelial Growth Factor, miRNA-423 Gene Abnormalities by Utilizing ARMS-PCR and Their Association with Fetal Hemoglobin Expression in the Patients with Sickle Cell Disease

Recent studies have indicated that microRNA and VEGF are considered to be genetic modifiers and are associated with elevated levels of fetal haemoglobin HbF, and thus they reduce the clinical impact of sickle haemoglobin (HbS) patients. This cross-sectional study was performed on clinical confirmed subjects of SCD cases. miR-423-rs6505162 C>T and VEGF-2578 C>A genotyping was conducted by ARMS-PCR in SCD and healthy controls. A strong clinical significance was reported while comparing the association of miR-423 C>T genotypes between SCD patients and controls (p = 0.031). The microRNA-423 AA genotype was associated with an increased severity of SCD in codominant model with odd ratio (OR = 2.36, 95% CI, (1.15–4.84), p = 0.018) and similarly a significant association was observed in recessive inheritance model for microRNA-423 AA vs (CC+CA) genotypes (OR = 2.19, 95% CI, (1.32–3.62), p < 0.002). The A allele was associated with SCD severity (OR = 1.57, 95% CI, (1.13–2.19), p < 0.007). The distribution of VEGF-2578 C>A genotypes between SCD patients and healthy controls was significant (p < 0.013). Our results indicated that in the codominant model, the VEGF-2578-CA genotype was strongly associated with increased SCD severity with OR = 2.56, 95% CI, (1.36–4.82), p < 0.003. The higher expression of HbA1 (65.9%), HbA2 (4.40%), was reported in SCD patients carrying miR-423-AA genotype than miR-423 CA genotype in SCD patients carrying miR-423 CA genotype HbA1 (59.98%), HbA2 (3.74%) whereas SCD patients carrying miR-423 CA genotype has higher expression of HbF (0.98%) and HbS (38.1%) than in the patients carrying AA genotype HbF (0.60%), HbS (36.1%). ARMS-PCR has been proven to be rapid, inexpensive and is highly applicable to gene mutation screening in laboratories and clinical practices. This research highlights the significance of elucidating genetic determinants that play roles in the amelioration of the HbF levels that is used as an indicator of severity of clinical complications of the monogenic disease. Further well-designed studies with larger sample sizes are necessary to confirm our findings.

Tenofovir disoproxil fumarate-mediated γ-globin induction is correlated with the suppression of trans-acting factors in CD34+ progenitor cells: A role in the reactivation of fetal hemoglobin

Sickle-cell disease (SCD) and β-thalassemia are public health issues that affect people all over the world. Fetal hemoglobin (HbF) induction is a molecular intervention, including hydroxyurea, which has made an effort to improve current treatment. Tenofovir disoproxil fumarate (TDF) is formerly reported with improving levels of hemoglobin, mean corpuscular hemoglobin (MCH), and mean corpuscular volume (MCV). Hence, in this preclinical investigation, human peripheral whole blood-derived CD34⁺ progenitor cells were cultured to prove the efficacy of TDF on erythroid proliferation, differentiation, γ-globin gene expression regulation, and ultimately HbF production. We observed that TDF increased the proliferation of immature erythroid cells, delayed the terminal erythroid maturation without cytotoxicity as correlated with other HbF inducers. Here, the presented data show that TDF can induce HbF expression by up-regulating the γ-globin gene transcription up to 7.1 ± 0.46-fold and subsequently increased the F-cells (10.79 ± 1.9-fold) population in terminally differentiated erythroid cells. Furthermore, our findings demonstrated that TDF-mediated γ-globin gene induction and HbF production was associated with down-fold regulation of BCL11A and SOX6, and their corresponding trans-acting regulators, FOP, KLF1, and GATA1. Collectively, our findings suggest TDF as an effective inducer of HbF in CD34⁺ cells and pave the way to put forward the assessment of TDF as a new potential therapy in treating β-hemoglobinopathies.

Cilostazol-mediated reversion of γ-globin silencing is associated with a high level of HbF production: A potential therapeutic candidate for β-globin disorders

Reversal of fetal hemoglobin (HbF) silencing is an attractive therapeutic intervention for β-thalassemia and sickle cell anemia. The current study proposes the therapeutic of repurposing of cilostazol, an FDA-approved antithrombotic agent, as a promising HbF inducer. Preliminary, we report that cilostazol induced erythroid differentiation and hemoglobinization of human erythroleukemia K562 cells. The erythroid differentiation was accompanied by increased expression of γ-globin mRNA transcripts and HbF production. Cilostazol induced erythroid differentiation and HbF production, without significantly affecting proliferation and viability of hemoglobin producing cells at maximum erythroid inducing concentration. Moreover, we investigated the effect of cilostazol on human β- and γ-globin transgenes in in vivo β-YAC transgenic mice, harboring human β-locus along with β-LCR. A good in vitro correlation was found with substantial up-regulation in fetal globin mRNA; whereas, the β-globin gene expression was not significantly changed. F-cells, analysis in the peripheral blood of cilostazol-treated mice, revealed a significant increase in the F-cells population as compared with sham control groups. Together, these findings support the potential of cilostazol as an HbF inducer, which can be evaluated further to develop a new HbF inducer.

Synthesis and Erythroid Induction Activity of New Thiourea Derivatives

BACKGROUND

The use of medicinal agents to augment the fetal hemoglobin (HbF) accretion is an important approach for the treatment of sickle-cell anemia and β-thalassemia. HbF inducers have the potential to reduce the clinical symptoms and blood transfusion dependence in the patients of β- hemoglobinopathies.

OBJECTIVE

The current study was aimed to examine the erythroid induction potential of newly synthesized thiourea derivatives.

METHODS

Thiourea derivatives 1-27 were synthesized by using environmentally friendly methods. Compounds 3, 10 and 22 were found to be new. The structures of synthesized derivatives were deduced by using various spectroscopic techniques. These derivatives were then evaluated for their erythroid induction using the human erythroleukemic K562 cell line, as a model. The benzidine-H2O2 assay was used to evaluate erythroid induction, while HbF expression was studied through immunocytochemistry using the Anti-HbF antibody. Cytotoxicity of compounds 1-27 was also evaluated on mouse fibroblast 3T3 cell line and cancer Hela cell line using MTT assay.

RESULT

All the compounds (1-27) have not been reported for their erythroid induction activity previously. Compounds 1, 2, and 3 were found to be the potent erythroid inducing agents with % induction of 45± 6.9, 44± 5.9, and 41± 6.1, at 1.56, 0.78, and 0.78 μM concentrations, respectively, as compared to untreated control (12 ± 1 % induction). Furthermore, compound 1, 2, and 3 significantly induced fetal hemoglobin the expression up to 4.2-fold, 4.06-fold, and 3.52-fold, respectively, as compared to untreated control. Moreover, the compounds 1-4, 6-9, 11, 12, 15, 17, 19, 22, 23, and 25 were found to be non-cytotoxic against the 3T3 cell line.

CONCLUSION

This study signifies that the compounds reported here may serve as the starting point for the designing and development of new fetal hemoglobin inducers for the treatment of β- hemoglobinopathies.

A comprehensive review of hydroxyurea for β-haemoglobinopathies: the role revisited during COVID-19 pandemic

Background

Hydroxyurea is one of the earliest drugs that showed promise in the management of haemoglobinopathies that include β-thalassaemia and sickle cell disease. Despite this, many aspects of hydroxyurea are either unknown or understudied; specifically, its usefulness in β-thalassaemia major and haemoglobin E β-thalassaemia is unclear. However, during COVID-19 pandemic, it has become a valuable adjunct to transfusion therapy in patients with β-haemoglobinopathies. In this review, we aim to explore the available in vitro and in vivo mechanistic data and the clinical utility of hydroxyurea in β-haemoglobinopathies with a special emphasis on its usefulness during the COVID-19 pandemic.

Main body

Hydroxyurea is an S-phase-specific drug that reversibly inhibits ribonucleoside diphosphate reductase enzyme which catalyses an essential step in the DNA biosynthesis. In human erythroid cells, it induces the expression of γ-globin, a fetal globin gene that is suppressed after birth. Through several molecular pathways described in this review, hydroxyurea exerts many favourable effects on the haemoglobin content, red blood cell indices, ineffective erythropoiesis, and blood rheology in patients with β-haemoglobinopathies. Currently, it is recommended for sickle cell disease and non-transfusion dependent β-thalassaemia. A number of clinical trials are ongoing to evaluate its usefulness in transfusion dependent β-thalassaemia. During the COVID-19 pandemic, it was widely used as an adjunct to transfusion therapy due to limitations in the availability of blood and logistical disturbances. Thus, it has become clear that hydroxyurea could play a remarkable role in reducing transfusion requirements of patients with haemoglobinopathies, especially when donor blood is a limited resource.

Conclusion

Hydroxyurea is a well-tolerated oral drug which has been in use for many decades. Through its actions of reversible inhibition of ribonucleoside diphosphate reductase enzyme and fetal haemoglobin induction, it exerts many favourable effects on patients with β-haemoglobinopathies. It is currently approved for the treatment of sickle cell disease and non-transfusion dependent β-thalassaemia. Also, there are various observations to suggest that hydroxyurea is an important adjunct in the treatment of transfusion dependent β-thalassaemia which should be confirmed by randomised clinical trials.

Erythrocyte microRNAs: a tiny magic bullet with great potential for sickle cell disease therapy

Sickle cell disease (SCD) is a severe hereditary blood disorder caused by a mutation of the beta-globin gene, which results in a substantial reduction in life expectancy. Many studies are focused on various novel therapeutic strategies that include re-activation of the γ-globin gene. Among them, expression therapy caused by the fetal hemoglobin (HbF) at a later age is highly successful. The induction of HbF is one of the dominant genetic modulators of the hematological and clinical characteristics of SCD. In fact, HbF compensates for the abnormal beta chain and has an ameliorant effect on clinical complications. Erythropoiesis is a multi-step process that involves the proliferation and differentiation of a small population of hematopoietic stem cells and is affected by several factors, including signaling pathways, transcription factors, and small non-coding RNAs (miRNAs). miRNAs play a regulatory role through complex networks that control several epigenetic mechanisms as well as the post-transcriptional regulation of multiple genes. In this review, we briefly describe the current understanding of interactions between miRNAs, their molecular targets, and their regulatory effects in HbF induction in SCD.

Hydroxyurea-Induced miRNA Expression in Sickle Cell Disease Patients in Africa

Hydroxyurea (HU) is clinically beneficial in sickle cell disease (SCD) through fetal hemoglobin (HbF) induction; however, the mechanism of HU is not yet fully elucidated. Selected miRNAs have been associated with HU-induced HbF production. We have investigated differential HU-induced global miRNA expression in peripheral blood of adult SCD patients in patients from Congo, living in South Africa. We found 22 of 798 miRNAs evaluated that were differentially expressed under HU treatment, with the majority (13/22) being functionally associated with HbF-regulatory genes, including BCL11A (miR-148b-3p, miR-32-5p, miR-340-5p, and miR-29c-3p), MYB (miR-105-5p), and KLF-3 (miR-106b-5), and SP1 (miR-29b-3p, miR-625-5p, miR-324-5p, miR-125a-5p, miR-99b-5p, miR-374b-5p, and miR-145-5p). The preliminary study provides potential additional miRNA candidates for therapeutic exploration.

Thiourea derivatives induce fetal hemoglobin production in-vitro: A new class of potential therapeutic agents for β-thalassemia

Fetal hemoglobin (HbF) induction is a cost-effective therapeutic approach for the treatment of β-hemoglobinopathies like β-thalassemia and sickle cell anemia. The present study discusses the potential of thiourea derivatives as new class of compounds that induce the fetal hemoglobin production. HbF inducing effect of thiourea derivatives was studied using experimental cell system, the human erythroleukemic K562 cell line. Erythroid induction of K562 cells was studied by the benzidine/H₂O₂ reaction, total hemoglobin production was estimated by plasma hemoglobin assay kit, and γ-globin gene expression by RT-qPCR, whereas fetal hemoglobin production was estimated by flow cytometry and immunofluorescence microscopy. The results indicated that newly synthesized thiourea derivative are potent inducers of erythroid differentiation of K562 cells with an increased γ-globin gene expression and fetal hemoglobin production. Moreover, these compounds showed no cytotoxic effect and inhibition on K562 cells at HbF inducing concentrations. It is important to note that hydroxyurea is a cytotoxic chemotherapeutic agent and have deleterious side effects, reflecting the need to identify new safe and effective HbF induces. These results signify thiourea derivatives as promising HbF inducers, with the potential to be studied against hematological disorders, including β-thalassemia and sickle cell anemia.

Characterization of natural killer cells expressing markers associated with maturity and cytotoxicity in children and young adults with sickle cell disease

BACKGROUND

Sickle cell disease (SCD) is increasingly recognized as a red blood cell disorder modulated by abnormally increased inflammation. We have previously shown that in patients with SCD not on a disease-modifying therapy (hydroxyurea or chronic transfusions), natural killer (NK) cell numbers are increased. In the current study, we further investigated the NK cell function to determine if there was evidence of increased activation and cytotoxicity.

PROCEDURE

We conducted a cross-sectional study of 44 patients with HbSS/HbSβ⁰ thalassemia at steady state (hydroxyurea = 13, chronic transfusion = 11, no disease-modifying therapy = 20) and 23 healthy controls. Using a fresh blood sample, NK immunophenotyping was performed as follows: NK cells (CD3^- CD56⁺ lymphocytes) were evaluated for makers associated with activation (NKG2D, NKp30, NKp44, and CD69) and maturity (CD57, killer immunoglobulin-like receptors (KIR), and CD56dim). Degranulation and cytotoxicity assays were performed to evaluate NK cell function.

RESULTS

Patients with SCD who were not on disease-modifying therapy had a higher number of NK cells with an immunophenotype associated with increased cytotoxicity (NKG2D⁺ , NKp30⁺ , CD56dim⁺ , and KIR⁺ NK cells) compared with healthy controls and patients on hydroxyurea. NK cells from SCD patients not on disease-modifying therapy demonstrated significantly increased cytotoxicity (measured by assaying NK cell killing of the K562 cell line) compared with healthy controls (P = 0.005). Notably, NK cell cytotoxicity against K562 cells in the hydroxyurea or chronic transfusion patients was not significantly different from that in healthy controls.

CONCLUSION

SCD is associated with increased NK cell function as well as increased NK cell numbers, which appears to be normalized with disease-modifying therapy.

Unravelling pathways downstream Sox6 induction in K562 erythroid cells by proteomic analysis

The Sox6 transcription factor is crucial for terminal maturation of definitive red blood cells. Sox6-null mouse fetuses present misshapen and nucleated erythrocytes, due to impaired actin assembly and cytoskeleton stability. These defects are accompanied with a reduced survival of Sox6^−/− red blood cells, resulting in a compensated anemia. Sox6-overexpression in K562 cells and in human primary ex vivo erythroid cultures enhances erythroid differentiation and leads to hemoglobinization, the hallmark of erythroid maturation. To obtain an overview on processes downstream to Sox6 expression, we performed a differential proteomic analysis on human erythroid K562 cells overexpressing Sox6. Sox6-overexpression induces dysregulation of 64 proteins, involved in cytoskeleton remodeling and in protein synthesis, folding and trafficking, key processes for erythroid maturation. Moreover, 43 out of 64 genes encoding for differentially expressed proteins contain within their proximal regulatory regions sites that are bound by SOX6 according to ENCODE ChIP-seq datasets and are possible direct SOX6 targets. SAR1B, one of the most induced proteins upon Sox6 overexpression, shares a conserved regulatory module, composed by a double SOX6 binding site and a GATA1 consensus, with the adjacent SEC24 A gene. Since both genes encode for COPII components, this element could concur to the coordinated expression of these proteins during erythropoiesis.

Sickle cell disease

Sickle cell disease is a common and life-threatening haematological disorder that affects millions of people worldwide. Abnormal sickle-shaped erythrocytes disrupt blood flow in small vessels, and this vaso-occlusion leads to distal tissue ischaemia and inflammation, with symptoms defining the acute painful sickle-cell crisis. Repeated sickling and ongoing haemolytic anaemia, even when subclinical, lead to parenchymal injury and chronic organ damage, causing substantial morbidity and early mortality. Currently available treatments are limited to transfusions and hydroxycarbamide, although stem cell transplantation might be a potentially curative therapy. Several new therapeutic options are in development, including gene therapy and gene editing. Recent advances include systematic universal screening for stroke risk, improved management of iron overload using oral chelators and non-invasive MRI measurements, and point-of-care diagnostic devices. Controversies include the role of haemolysis in sickle cell disease pathophysiology, optimal management of pregnancy, and strategies to prevent cerebrovascular disease.

SAR1a promoter polymorphisms are not associated with fetal hemoglobin in patients with sickle cell disease from Cameroon

Background

Reactivation of adult hemoglobin (HbF) is currently a dominant therapeutic approach to sickle cell disease (SCD). In this study, we have investigated among SCD patients from Cameroon, the association of HbF level and variants in the HU-inducible small guanosine triphosphate-binding protein, secretion-associated and RAS-related (SAR1a) protein, previously shown to be associated with HbF after HU treatment in African American SCD patients.

Results

Only patients >5 years old were included; hemoglobin electrophoresis and a full blood count were conducted upon arrival at the hospital. RFLP-PCR was used to describe the HBB gene haplotypes and Gap PCR to investigate the 3.7 kb α-globin gene deletion. The iPLEX Gold Sequenom Mass Genotyping Array and cycle sequencing were used for the genotyping of four selected SNPs in SAR1a (rs2310991; rs4282891; rs76901216 and rs76901220). Genetic analysis was performed using an additive genetic model, under a generalized linear regression framework. 484 patients were studied. No associations were observed between any of the promoter variants and baseline HbF, clinical events or other hematological indices.

Conclusion

The results of this study could be explained by possible population-specificity of some tagging genomic variants associated with HbF production and illustrated the complexity of replicating HbF-promoting variants association results across African populations.

Key Pharmacogenomic Considerations for Sickle Cell Disease Patients

Sickle cell disease (SCD), although a monogenic disease, exhibits a complex clinical phenotype that hampers optimum patient stratification and disease management, especially on hydroxyurea treatment. Moreover, theranostics, the combination of diagnostics to individualize and optimize therapeutic interventions, has not been firmly on the forefront of SCD research and clinical management to date. We suggest that if tailor-made theranostics in SCD is envisaged, pharmacogenomics is anticipated to be the way forward. Herein, we present the current key pharmacogenomic opportunities and challenges in SCD, considering population variation, ethics, and socioeconomic aspects. We focus on pharmacogenomics and pain management, genethics, and cost-effectiveness in SCD. We searched for and synthesized data from PubMed and Google Scholar, and the references from relevant articles, using the keywords "pharmacogenomics," "sickle cell disease," "hydroxyurea," "ethics," "pain management," "morphine metabolism," "opioids," "pharmacogenomics and chronic pain," "cost-effectiveness," and "economic evaluation." Only articles published in English were included. So far, when pharmacogenomics in SCD has been considered, interindividual variability in hydroxyurea response/toxicity has been of primary interest. We underscore the need to extend pharmacogenomic considerations on other therapeutic interventions currently present using a holistic patient-centric approach, and taking disease complications into account as well. Furthermore, we raise awareness toward socioeconomic, ethical, and population differences in the way sickle cell pharmacogenomics might unfold in the future. If pharmacogenomics in SCD is to be used in the clinic in an evidence-based manner, cost-effectiveness and population-specific empirical ethics data are urgently needed.

Sickle Cell Disease: A Brief Update

Sickle cell disease (SCD) is an inherited monogenic disease characterized by misshapen red blood cells that causes vaso-occlusive disease, vasculopathy, and systemic inflammation. Approximately 300,000 infants are born per year with SCD globally. Acute, chronic, and acute-on-chronic complications contribute to end-organ damage and adversely affect quantity and quality of life. Hematopoietic stem cell transplantation is the only cure available today, but is not feasible for the vast majority of people suffering from SCD. Fortunately, new therapies are in late clinical trials and more are in the pipeline, offering hope for this unfortunate disease, which has increasing global burden.

Studies of novel variants associated with Hb F in Sardinians and Tanzanians in sickle cell disease patients from Cameroon

High level of Hb F has been shown to improve survival in sickle cell disease. Among 453 Cameroonians with sickle cell disease, we have investigated 18 selected single-nucleotide polymorphisms (SNPs) in novel and suggestive loci associated with Hb F level identified through a genomewide association study in sickle cell disease patients in Tanzania, and whole-genome sequencing of a population from Sardinia. Seven of 10 variants reported in Sardinians were either monomorphic or very rare in the Cameroonians. No associations were observed with any SNPs and Hb F levels in Cameroonians affected by sickle cell disease. The present study illustrates the complexity of replicating Hb F-promoting variants association results across populations.

Correlation of SIN3A genomic variants with β-hemoglobinopathies disease severity and hydroxyurea treatment efficacy

AIMS

Hemoglobinopathies, particularly β-thalassemia and sickle cell disease, are characterized by great phenotypic variability in terms of disease severity, while notable differences have been observed in hydroxyurea treatment efficacy. In both cases, the observed phenotypic diversity is mostly dependent on the elevated fetal hemoglobin levels, resulting from the persistent fetal globin gene expression in the adult erythroid stage orchestrated by intricate mechanisms that still remain only partly understood. We have previously shown that several protein factors act as modifiers of fetal hemoglobin production, exerting their effect via different pathways.

MATERIALS & METHODS

Here, we explored whether SIN3A could act as a modifier of fetal globin gene expression, as it interacts with KLF10, a known modifier of fetal hemoglobin production.

RESULTS

We show that SIN3A genomic variants are associated both with β-thalassemia disease severity (rs11072544) as well as hydroxyurea treatment response (rs7166737) in β-hemoglobinopathies patients.

CONCLUSION

Our findings further underline that fetal hemoglobin production is the result of a complex interplay in which several human globin gene cluster variants interact with protein factors encoded by modifier genes to produce the observed clinical outcome.

An Expert Review of Pharmacogenomics of Sickle Cell Disease Therapeutics: Not Yet Ready for Global Precision Medicine

Sickle cell disease (SCD) is a blood disease caused by a single nucleotide substitution (T > A) in the beta globin gene on chromosome 11. The single point mutation (Glu6Val) promotes polymerization of hemoglobin S (HbS) and causes sickling of erythrocytes. Vaso-occlusive painful crises are associated with recurrent and long-term use of analgesics/opioids and hydroxyurea (HU) by people living with SCD. The present analysis offers a state-of-the-art expert review of the effectiveness of pharmacogenomics/genetics of pain management in SCD, with specific focus on HU and opioids. The literature search used the following keywords: SCD, pharmacogenomics, pharmacogenetics, pain, antalgics, opioids, morphine, and HU. The literature was scanned until March 2016, with specific inclusion of targeted landmark and background articles on SCD. Surprisingly, our review identified only a limited number of studies that addressed the genetic/genomic basis of variable responses to pain (e.g., variants in OPRM1, HMOX-1, GCH1, VEGFA COMT genes), and pharmacogenomics of antalgics and opioids (e.g., variants in OPRM1, STAT6, ABCB1, and COMT genes) in SCD. There has been greater progress made toward identifying the key genomic variants, mainly in BCL11A, HBS1L-MYB, or SAR1, which contribute to response to HU treatment. However, the complete picture on pharmacogenomic determinants of the above therapeutic phenotypes remains elusive. Strikingly, no study has been conducted in sub-Saharan Africa where majority of the patients with SCD live. This alerts the broader global life sciences community toward the existing disparities in optimal and ethical targeting of research and innovation investments for SCD specifically and precision medicine and pharmacology research broadly.

Cellular therapy for sickle cell disease

Sickle cell disease (SCD) is a monogenic red cell disorder affecting more than 300 000 annual births worldwide and leading to significant organ toxicity and premature mortality. Although chronic therapies such as hydroxyurea have improved outcomes, more durable therapeutic and curative options are still being investigated. Newer understanding of the disease has implicated invariant natural killer T cells as a critical immune profile that potentiates SCD. Hence, targeting this cell population may offer a new approach to disease management. Hematopoietic stem cell transplant is a curative option for patients with SCD, but the under-representation of minorities on the unrelated donor registry means that this is not a feasible option for more than 75% of patients. Work in this area has therefore focused on increasing the donor pool and decreasing transplant-related toxicities to make this a treatment option for the majority of patients with SCD. This review focuses on the currently available cell and gene therapies for patients with SCD and acknowledges that newer gene-editing approaches to improve gene therapy efficiency and safety are the next wave of potentially curative approaches.

Hydroxyurea down-regulates BCL11A, KLF-1 and MYB through miRNA-mediated actions to induce γ-globin expression: implications for new therapeutic approaches of sickle cell disease

Background

The major therapeutic benefit of hydroxyurea, the only FDA-approved pharmacologic treatment for sickle cell disease (SCD), is directly related to fetal hemoglobin (HbF) production that leads to significant reduction of morbidity and mortality. However, potential adverse effects such as infertility, susceptibility to infections, or teratogenic effect have been subject of concerns. Therefore, understanding HU molecular mechanisms of action, could lead to alternative therapeutic agents to increase HbF with less toxicity. This paper investigated whether HU-induced HbF could operate through post-transcriptional miRNAs regulation of BCL11A, KLF-1 and MYB, potent negative regulators of HbF. Both ex vivo differentiated primary erythroid cells from seven unrelated individuals, and K562 cells were treated with hydroxyurea (100 μM) and changes in BCL11A, KLF-1, GATA-1, MYB, β- and γ-globin gene expression were investigated. To explore potential mechanisms of post-transcriptional regulation, changes in expression of seven targeted miRNAs, previously associated with basal γ-globin expression were examined using miScript primer assays. In addition, K562 cells were transfected with miScript miRNA inhibitors/anti-miRNAs followed by Western Blot analysis to assess the effect on HbF protein levels. Direct interaction between miRNAs and the MYB 3′-untranslated region (UTR) was also investigated by a dual-luciferase reporter assays.

Results

Down-regulation of BCL11A and MYB was associated with a sevenfold increase in γ-globin expression in both primary and K562 cells (p < 0.003). Similarly, KLF-1 was down-regulated in both cell models, corresponding to the repressed expression of BCL11A and β-globin gene (p < 0.04). HU induced differential expression of all miRNAs in both cell models, particularly miR-15a, miR-16, miR-26b and miR-151-3p. An HU-induced miRNAs-mediated mechanism of HbF regulation was illustrated with the inhibition of miR-26b and -151-3p resulting in reduced HbF protein levels. There was direct interaction between miR-26b with the MYB 3′-untranslated region (UTR).

Conclusions

These experiments have shown the association between critical regulators of γ-globin expression (MYB, BCL11A and KLF-1) and specific miRNAs; in response to HU, and demonstrated a mechanism of HbF production through HU-induced miRNAs inhibition of MYB. The role of miRNAs-mediated post-transcriptional regulation of HbF provides potential targets for new treatments of SCD that may minimize alterations to the cellular transcriptome.

Electronic supplementary material

The online version of this article (doi:10.1186/s40169-016-0092-7) contains supplementary material, which is available to authorized users.

Pomalidomide reverses γ-globin silencing through the transcriptional reprogramming of adult hematopoietic progenitors

Current therapeutic strategies for sickle cell anemia are aimed at reactivating fetal hemoglobin. Pomalidomide, a third-generation immunomodulatory drug, was proposed to induce fetal hemoglobin production by an unknown mechanism. Here, we report that pomalidomide induced a fetal-like erythroid differentiation program, leading to a reversion of γ-globin silencing in adult human erythroblasts. Pomalidomide acted early by transiently delaying erythropoiesis at the burst-forming unit-erythroid/colony-forming unit-erythroid transition, but without affecting terminal differentiation. Further, the transcription networks involved in γ-globin repression were selectively and differentially affected by pomalidomide including BCL11A, SOX6, IKZF1, KLF1, and LSD1. IKAROS (IKZF1), a known target of pomalidomide, was degraded by the proteasome, but was not the key effector of this program, because genetic ablation of IKZF1 did not phenocopy pomalidomide treatment. Notably, the pomalidomide-induced reprogramming was conserved in hematopoietic progenitors from individuals with sickle cell anemia. Moreover, multiple myeloma patients treated with pomalidomide demonstrated increased in vivo γ-globin levels in their erythrocytes. Together, these data reveal the molecular mechanisms by which pomalidomide reactivates fetal hemoglobin, reinforcing its potential as a treatment for patients with β-hemoglobinopathies.

A systematic review of known mechanisms of hydroxyurea-induced fetal hemoglobin for treatment of sickle cell disease

AIM

To report on molecular mechanisms of fetal hemoglobin (HbF) induction by hydroxyurea (HU) for the treatment of sickle cell disease.

STUDY DESIGN

Systematic review.

RESULTS

Studies have provided consistent associations between genomic variations in HbF-promoting loci and variable HbF level in response to HU. Numerous signal transduction pathways have been implicated, through the identification of key genomic variants in BCL11A, HBS1L-MYB, SAR1 or XmnI polymorphism that predispose the response to the treatment, and signal transduction pathways that modulate γ-globin expression (cAMP/cGMP; Giα/c-Jun N-terminal kinase/Jun; methylation and miRNA). Three main molecular pathways have been reported: i) Epigenetic modifications, transcriptional events and signaling pathways involved in HU-mediated response, ii) Signaling pathways involving HU-mediated response and iii) Post-transcriptional pathways (regulation by miRNAs).

CONCLUSIONS

The complete picture of HU-mediated mechanisms of HbF production in Sickle Cell Disease remains elusive. Research on post-transcriptional mechanisms could lead to therapeutic targets that may minimize alterations to the cellular transcriptome.