Asma Farag

Bio: Asma Farag is an academic researcher. The author has contributed to research in topics: Anemia & Pharmacogenetics. The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

Response to hydroxyurea among Kuwaiti patients with sickle cell disease and elevated baseline HbF levels.

Abstract: complications. JAK2V617F mutation primarily affects the proliferation of the red cell lineage but its impact on the phenotype of circulating RBCs is poorly documented. Our group showed increased adhesion of PV RBCs to endothelial cells mediated by erythroid Lu/BCAM and endothelial laminin a5 chain [4]. Recently, we showed that this abnormal adhesion stems from JAK2V617F-mediated Lu/BCAM activation through a Rap1/Akt signaling pathway [5]. Blocking this pathway by JAK2 specific inhibitors led to significant decrease of PV RBC adhesion [5]. Here, we extended our findings by a quantitative analysis to determine the relationship between the rate of RBC adhesion to laminin and the JAK2V617F allele burden. We first asked whether variation between patients in RBC adhesion was related to Lu/BCAM expression on the surface of PV RBCs. Indeed, Lu/BCAM erythroid expression is heterogeneous within the same individual, including a variable surface expression level and a proportion of Lu/BCAM-negative RBCs. We performed adhesion assays with blood samples from 17 JAK2V617F-positive PV patients, with no cytotoxic antiproliferative treatment, and determined the number of RBCs adhering to laminin at 3 dyn/cm. The adhesion values were variable, ranging from 14 to 1021 RBCs/mm (Supporting Information Table S1). The percentage of Lu/BCAM-positive RBCs as assessed by flow cytometry ranged from 38% to 90%, and the expression level, estimated by the mean fluorescence intensity (MFI), from 1249 to 3153 (Supporting Information Table S1). The number of adherent RBCs was plotted against the percentage of Lu/BCAM-positive RBCs or the MFI of each blood sample. We found no correlation between the number of adherent RBCs and the percentage of Lu/BCAM-positive RBCs (r 5 0.468 and P 5 0.058 at 3 dyn/cm, Fig. 1A), and between RBC adhesion and Lu/BCAM MFI values (r 5 0.345 and P 5 0.174 at 3 dyn/cm, Fig. 1B). These results indicated that Lu/ BCAM expression alone did not account for the variability of PV RBC adhesion, in accordance with the role of Lu/BCAM phosphorylation in the adhesion of PV RBCs to laminin [5]. Because Lu/BCAM phosphorylation is driven by a JAK2V617F-dependent pathway in PV RBCs [5], we asked whether RBC adhesion was influenced by JAK2V617F expression level. To date the most commonly used tool for evaluating the mutational load in one individual is by measuring the mutant allele burden in blood cell DNA. The JAK2V617F allele burden was determined for the 17 PV patients using an allele specific quantitative PCR (MutaquantVR , Qiagen) and ranged from 20 to 68% (Supporting Information Table S1). RBC adhesion values were plotted against the percentage of JAK2V617F. Statistical analysis showed a significant correlation between RBC adhesion and JAK2V617F percentage (r 5 0.571 and P 5 0.016, Fig. 1C) that was improved when the interval of Lu/ BCAM-positive RBCs was restricted to 65–90% (r 5 0.849 and P 5 0.0009, n 5 11 patients), indicating that for equivalent Lu/BCAM expression, higher JAK2V617F levels would drive higher RBC adhesion to laminin (Fig. 1D). As RBCs are enucleated, it is not possible to estimate the level of JAK2V617F using DNA or RNA based PCR assays. However, clonogenic assays showed that patients with higher JAK2V617F mutant allele burden in blood DNA carried more mutated erythroid progenitor cells [6]. Our study revealed RBC adhesion as a biological marker to estimate the V617F mutational load at the protein level in PV RBCs; although indirect, this marker has the potential of informing about the functional level of JAK2V617F in the circulation. This functional assay should be evaluated in a prospective study because it is a rapid and routinely manageable tool to estimate the mutant kinase activity in PV RBCs, which may help assessing the disease progression and the risk of evolution, in particular of thrombotic events in which abnormal adhesion of JAK2V617F-positive RBCs to endothelium could play a role. Furthermore, such a tool may be important to monitor the efficacy of JAK2 inhibitors in PV patients during the very early stages of their treatment by assessing the effect of these inhibitors on JAK2V617F activity in RBCs very shortly after their administration giving important information on their pharmacokinetics in the blood circulation. A European patent application (n8 EP13305131.8) was filed for this study, with the international extension n8 PCT/EP2014/052153.

Genetic Modifiers of Fetal Haemoglobin in Sickle Cell Disease.

Abstract: Fetal haemoglobin (HbF) levels have a clinically beneficial effect on sickle cell disease (SCD). Patients with SCD demonstrate extreme variability in HbF levels (1–30%), a large part of which is likely genetically determined. The main genetic modifier loci for HbF persistence, HBS1L-MYB, BCL11A and the β-globin gene cluster in adults also act in SCD patients. Their effects are, however, modified significantly by a disease pathology that includes a drastically shortened erythrocyte lifespan with an enhanced survival of those red blood cells that carry HbF (F cells). We propose a model of how HbF modifier genes and disease pathology interact to shape HbF levels measured in patients. We review current knowledge on the action of these loci in SCD, their genetic architecture, and their putative functional components. At each locus, one strong candidate for a causative, functional DNA change has been proposed: Xmn1-HBG2 at the β-globin cluster, rs1427407 at BCL11A and the 3 bp deletion rs66650371 at HBS1L-MYB. These, however, explain only part of the impact of these loci and additional variants are yet to be identified. Further progress in understanding the genetic control of HbF levels requires that confounding factors inherent in SCD, such as ethnic complexity, the role of F cells and the influence of drugs, are suitably addressed. This will depend on international collaboration and on large, well-characterised patient cohorts with genome-wide single-nucleotide polymorphism or sequence data.

Osteonecrosis in sickle cell disease: an update on risk factors, diagnosis, and management.

Abstract: Osteonecrosis, a form of ischemic bone injury that leads to degenerative joint disease, affects ∼30% of people with sickle cell disease. Although osteonecrosis most commonly affects the femoral head (often bilaterally, with asymmetric clinical and radiographic progression), many people with sickle cell disease also present with multifocal joint involvement. We present the case of a young woman with bilateral osteonecrosis of the femoral head at varying stages of progression; we also highlight other important comorbid complications (eg, chronic pain requiring long-term opioids, debility, and social isolation) and postoperative outcomes. In this review, partly based on recommendations on osteonecrosis management from the 2014 evidence-based report on sickle cell disease from the National Heart, Lung and Blood Institutes, we also discuss early signs or symptoms of osteonecrosis of the femoral head, radiographic diagnosis and staging criteria, hydroxyurea effect on progression to femoral head collapse, and surgical outcomes of total hip arthroplasty in the modern era. In summary, we failed to find an association between hydroxyurea use and femoral head osteonecrosis; we also showed that evidence-based perioperative sickle cell disease management resulted in superior postoperative outcomes after cementless total hip arthroplasty in sickle cell-related osteonecrosis of the femoral head.

Hydroxyurea in the management of sickle cell disease: pharmacogenomics and enzymatic metabolism.

Abstract: Hydroxyurea (HU) was approved to be used in the treatment of sickle cell disease (SCD) because of its anti-sickling potential. However, there is variability in HU response among SCD patients and this can be due to physiological, socioeconomic, environmental, metabolic and/or genetic factors. The present review focuses on the latter two. Three quantitative trait loci, HBG2, BCL11A and HMIP, have been suggested as important markers for HU response. Other genes (ASS1, KLF10, HAO2, MAP3K5, PDE7B, TOX, NOS1, NOS2A, FLT1, ARG1, ARG2, UGT1A1, OR51B5/6, SIN3A, SALL2, SAR1A, UTB, OCTN1, CYP2C9, AQP9, MPO, CYP2E1, and GSTT1) have also been considered. Studies implicate catalase, urease, horseradish peroxidase and enzymes of CYP450 family in HU metabolism. However, little is known about these enzymes. Therefore, further studies are needed to elucidate the metabolic pathway of HU, which will facilitate pharmacogenomic studies and help in identification of candidate genes for predicting HU response.

Hydroxyurea: Pattern of Use, Patient Adherence, and Safety Profile in Patients with Sickle Cell Disease in Oman.

Abstract: Objectives Many barriers contribute to the underutilization of hydroxyurea (HU) in the treatment of sickle cell disease (SCD), and adherence to its use is often reported to be suboptimal. It is important to have information on the safety of HU in patients with SCD. Our study assessed the pattern of use, patients' adherence to medication, discontinuation of use, and safety of HU in patients with SCD. Methods This cross-sectional study was conducted in the department of medicine of a referral hospital in Oman over five months and included a review of patient files and patient interview. Approval was obtained from the Regional Research and Ethics Committee of the A'Dakhiliyah Governorate and the hospital administration. The parameters were compared between groups using the chi-square test. Results Of 298 patients studied, 128 (43.0%) had used HU at some points. The difference in the prevalence of HU use was statistically significant based only on age (p = 0.014), with younger patients more likely to be currently using HU or used HU in the past. The majority of patients were adherent (82.5%) based on self-reported adherence. The prevalence of discontinuation (temporary or permanent) of HU use was high (57.0%), and suspected adverse drug reaction (ADR) was the most common reason. Among those who had never used HU, 33.7% of patients had an indication for the initiation of HU. A quarter of patients who used HU developed a suspected ADR, with blood abnormalities being the commonest. The duration of HU use influenced ADR prevalence (p = 0.015). Conclusions Among the current users of HU, the majority of the patients were adherent based on self-reported medication adherence. The prevalence of discontinuation of HU use and instances of non-initiation of HU among those indicated were high. A larger study, ideally of a prospective nature, in various governorates of Oman, would provide a wider picture at the national level.

The Sub-Phenotypes of Sickle Cell Disease in Kuwait.

Abstract: Kuwaiti patients with sickle cell disease generally have a mild phenotype, but exhibit considerable heterogeneity, in spite of high Hb F levels. We have carried out a cross-sectional study of patie...