Warts, Hypogammaglobulinemia, Infections, And Myelokathexis Research Articles

CXCR4: from B-cell development to B cell-mediated diseases.

Chemokine receptors are members of the G protein-coupled receptor superfamily. The C-X-C chemokine receptor type 4 (CXCR4), one of the most studied chemokine receptors, is widely expressed in hematopoietic and immune cell populations. It is involved in leukocyte trafficking in lymphoid organs and inflammatory sites through its interaction with its natural ligand CXCL12. CXCR4 assumes a pivotal role in B-cell development, ranging from early progenitors to the differentiation of antibody-secreting cells. This review emphasizes the significance of CXCR4 across the various stages of B-cell development, including central tolerance, and delves into the association between CXCR4 and B cell-mediated disorders, from immunodeficiencies such as WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome to autoimmune diseases such as systemic lupus erythematosus. The potential of CXCR4 as a therapeutic target is discussed, especially through the identification of novel molecules capable of modulating specific pockets of the CXCR4 molecule. These insights provide a basis for innovative therapeutic approaches in the field.

Mavorixafor for Patients with Chronic Neutropenic Disorders Treated with G-CSF: Preliminary Response Data and G-CSF Dose Reduction in an Ongoing Phase 2, Open-Label, Multicenter Study Support Reduction in G-CSF Dosing

Introduction: Chronic neutropenia (CN) encompasses multiple disorders characterized by an absolute neutrophil count (ANC) <1500 cells/µL for >3 months, leading to increased susceptibility to recurrent and/or severe infections. CN can be sub-classified as congenital neutropenia defined by genetic variants ( ELANE variants are the most common), cyclic neutropenia (CyN) supported by documentation of ANC cycling with reciprocal monocytosis most often associated with certain ELANE variants, or chronic idiopathic neutropenia (CIN) defined as acquired neutropenia without an identifiable cause. The current treatment approach for CN involves long-term use of injectable granulocyte colony-stimulating factor (G-CSF), which can have associated adverse events (AEs) [Donadieu J. Expert Rev Hematol. 2021; Fioredda F. Hemasphere. 2023; Newburger PE. Semin Hematol. 2013]. Therefore, efforts are under way to discover other therapies for CN. In a phase 3 trial (NCT03995108), mavorixafor, an investigational oral CXCR4 antagonist, showed durable increases in ANC and reduction in total infection rate and severity in people with WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome [Badolato R. Clin Immunol. 2023]. Mavorixafor is being studied in a phase 2 trial for chronic neutropenic disorders (NCT04154488) [Warren JT. Blood. 2022] to evaluate the durability, safety, and tolerability of chronic dosing of mavorixafor with or without concurrent G-CSF. Here, we describe preliminary results for 3 participants in the ongoing phase 2 trial. Methods: Individuals (aged ≥12 years) with diagnosis of congenital neutropenia, CyN, or CIN ≥6 months prior and ANC <1000/µL (or no lower limit but <10,000/µL if on G-CSF) at screening visits were enrolled in the phase 2 trial. Eligible adult participants received once-daily 400 mg of mavorixafor while adolescents received weight-based dosing (>50 kg, 400mg; ≤50 kg, 200 mg) for 6 months with or without G-CSF. Participants already on G-CSF continued their individualized G-CSF dosing for ≥8 weeks, followed by potential dose and/or frequency reduction based on monthly ANC assessments. Hematologic parameters, including ANC, were assessed over 8 hours on day 1 and at months 1 and 3, with continued assessment at month 6. At months 2 and 4 (assessment to continue at month 5), hematologic parameters were assessed within 2 to 4 hours of dosing to reduce trial burden. Results: Data are reported as of July 17, 2023. Preliminary data from the first 3 participants on G-CSF receiving chronic once-daily oral mavorixafor for at least 2 months showed increases in mean ANC compared with baseline (BL) at all time points assessed in all participants. ANCs reached normal ranges for all participants. Increases in ANC supported physicians' decisions to reduce G-CSF dosing. Two participants (P1 and P2) with CIN achieved increases in ANC that enabled initiation of G-CSF tapering at month 2. For P1, G-CSF dose was tapered to 50% at month 2, and further G-CSF tapering occurred at month 3. ANC remained within normal ranges during this period. At month 4, G-CSF dosing was fully withdrawn, and the participant continued daily mavorixafor monotherapy. For P2, ANC increased ~3x baseline by month 2. G-CSF dose was tapered to 50% after month 2. ANC remained within normal ranges during this period. At month 3, G-CSF dosing was fully withdrawn, and the participant continued daily mavorixafor monotherapy with an ANC ~1000 cells/µL. A third participant (P3) with CyN receiving mavorixafor daily with concurrent G-CSF showed increases in ANC over BL for 4 months. All 3 participants remain on study, and have not experienced any serious AEs Conclusions: Our report shows that chronic treatment with oral, once-daily mavorixafor in combination with G-CSF resulted in durable increases in ANC compared with BL for ≥3 months in 3 study participants. Reduction of injectable G-CSF dosing was implemented in 2 study participants with CIN following robust ANC increase observed after the first 2 months of combination treatment. These preliminary data also support the safety of concomitant treatment with G-CSF and mavorixafor. Additional data from the ongoing phase 2 study will further elucidate the potential of daily, oral mavorixafor as a treatment for CN to reduce the burden and associated AEs of injectable G-CSF. A phase 3 trial of people with CN is being planned.

An unlucky WHIMsical child – A case report

Immunodeficiency in children often has the worst prognosis and there are varied primary and secondary causes for immunodeficiency. Warts Hypogammaglobulinemia, Infections, and Myelokathexis (WHIM) syndrome is a congenital immune deficiency that increases the likelihood of human papillomavirus infection (Warts), a low white blood cell count, hypogammaglobulinemia, and bone marrow myelokathexis. We present the case of a 3-year-old child brought by an orphanage caretaker with a history of recurrent swelling in both eyelids, multiple skin lesions all over the body, and recurrent respiratory tract infections. The child has been treated with native medications elsewhere with no improvement noted. Work up done for immune deficient states and bone marrow evaluation revealed myelokathexis with neutropenia/lymphopenia which made the possibility of WHIM syndrome. Treatment with colony stimulating factor has been initiated but could not be continued due to financial constraints. This report emphasis on the need for work-up to make early diagnosis and intervention of the disease as such than treating only their manifestations.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome and tetralogy of fallot; Case report and literature review

WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome is a rare primary immunodeficiency disorder characterized by susceptibility to human papillomavirus (HPV) infections, neutropenia, and hypogammaglobulinemia. WHIM syndrome is caused by a gain-of-function mutation CXCR4, leading to increased responsiveness of neutrophils and lymphocytes to CXCL12. This results in an accumulation of atypical hypersegmented mature neutrophils in the bone marrow and peripheral blood neutropenia. This case report discusses a 10-year-old girl who was diagnosed with WHIM syndrome at the age of four years following Haemophilus influenzae meningitis. She was found to have Tetralogy of Fallot at birth, which was surgically repaired when she was one year old. She was also found to have significant neutropenia during surgery and received multiple doses of G-CSF with a good response. She presented to the hospital at the age of four years with fever, neck stiffness, lethargy, and headache and was diagnosed with H. influenzae meningitis. Her immunology workup revealed significant neutropenia and hypogammaglobulinemia, as well as low antibody levels to H. influenza type B, tetanus toxoid, and Streptococcus pneumonia, despite up-to-date vaccination. Furthermore, decreased levels of T cells and B cells were detected. The patient was started on IgG replacement therapy and Bactrim prophylaxis. Bone marrow biopsy revealed granulocytic hyperplasia and occasional hypersegmented neutrophils, suggesting myelokathexis. Genetic testing revealed a heterozygous CXCR4 mutation with a premature stop codon (p.Ser338Ter), confirming the diagnosis of WHIM syndrome. This case report highlights the association of WHIM syndrome with congenital heart defects, such as Tetralogy of Fallot. A literature review revealed three other cases of congenital heart defects in patients with WHIM syndrome, indicating a potential role for CXCR4 and CXCL12 in septum formation. The rarity of the disorder and the lack of a universal screening tool makes the diagnosis of WHIM syndrome difficult. Therefore, physicians should consider WHIM syndrome in patients with congenital heart defects, particularly if they have recurrent HPV infections, neutropenia, and hypogammaglobulinemia.

Respiratory symptoms of COVID-19 in an adolescent patient with WHIM syndrome: a clinical case

In case of coronavirus disease 2019 (COVID-19) in children suffering from primary immunodeficiency, the last one can be an aggravating or a mitigating factor of the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome is usually classified as severe congenital neutropenia, but most patients have multiple leukocyte deficits, even panleukopenia, and therefore it can also be classified as severe combined immunodeficiency. B-lymphopenia is especially severe, and this probably partly explains the hypogammaglobulinemia. This rare disease, caused by autosomal dominant mutations, is a combined variant of immunodeficiency, which includes myelokathexis, susceptibility to infections, and hypogammaglobulinemia. Myelokathexis is a unique form of acyclic severe congenital neutropenia caused by the accumulation of mature and degenerative neutrophils in the bone marrow. Monocytopenia and lymphopenia, especially B-lymphopenia, also occur. In some patients, there are defects in the development of the cardiovascular, genitourinary and nervous systems, which in general can contribute to the extremely severe course of infectious inflammatory process, in particular due to the SARS-CoV-2. Objective: to analyze the clinical and laboratory peculiarities of coronavirus disease caused by SARS-CoV-2 in immunosuppressed patients on the example of a clinical case of COVID-19 in a child with previously diagnosed WHIM syndrome. Materials and methods. The article presents our own observation of coronavirus disease in a female adolescent suffering from previously verified primary immunodeficiency (WHIM syndrome) in the period after surgical routine correction of patent ductus arteriosus. On the 2nd day of sudden disease onset, the child was hospitalized in moderate condition with signs of airway inflammation as rhinopharyngitis and obstructive bronchitis. Results. Laboratory tests showed leukopenia, absolute neutropenia, increased levels of procalcitonin, C-reactive protein, D-dimer in serum and a reduction of activated partial thromboplastin time. The treatment included hydrobalance protection per os and by infusion, systemic and topical inhalation therapy with a short steroids course, antibacterial therapy as fourth generation cephalosporins, intravenous granulocyte colony stimulating factor, and symptomatic treatment. The girl’s condition became progressively better, she was discharged from the hospital on the 7th day to continue treatment at the outpatient settings. Conclusions. The severity of respiratory pathology and the prognosis of COVID-19 depend on the immunodeficiency type and compromised part of immune system, as well as the heterogeneity of new SARS-CoV-2 strains. The aggravating/protective role of primary immunodeficiency, in particular WHIM syndrome, in determining COVID-19 severity is currently limited because of small number of observations and requires further data collection. The presented clinical case describes the classic moderate coronavirus disease as airway infection in an adolescent suffering from primary immunodeficiency.

Dysregulated stem cell niches and altered lymphocyte recirculation cause B and T cell lymphopenia in WHIM syndrome.

Gain-of-function (GOF) mutations in CXCR4 cause WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome, characterized by infections, leukocyte retention in bone marrow (BM), and blood leukopenias. B lymphopenia is evident at early progenitor stages, yet why do CXCR4 GOF mutations that cause B (and T) lymphopenia remain obscure? Using a CXCR4 R334X GOF mouse model of WHIM syndrome, we showed that lymphopoiesis is reduced because of a dysregulated mesenchymal stem cell (MSC) transcriptome characterized by a switch from an adipogenic to an osteolineage-prone program with limited lymphopoietic activity. We identify lymphotoxin beta receptor (LTβR) as a critical pathway promoting interleukin-7 (IL-7) down-regulation in MSCs. Blocking LTβR or CXCR4 signaling restored IL-7 production and B cell development in WHIM mice. LTβR blocking also increased production of IL-7 and B cell activating factor (BAFF) in secondary lymphoid organs (SLOs), increasing B and T cell numbers in the periphery. These studies revealed that LTβR signaling in BM MSCs and SLO stromal cells limits the lymphocyte compartment size.

Application of an Artificial Intelligence/Machine Learning Model for Estimating Potential US Prevalence of WHIM Syndrome, a Rare Immunodeficiency, from Insurance Claims Data

Introduction: WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome is an inborn error of immunity characterized as a primary immunodeficiency with neutropenia-but the acronym does not reflect the broad spectrum of disease manifestations that patients may experience. A WHIM syndrome diagnosis may be confirmed clinically by the presence of myelokathexis, the retention of white blood cells in the bone marrow, or by identification of a known pathogenic gain-of-function mutation in the CXCR4 gene coding for the CXCR4 receptor. Diagnosis of WHIM syndrome is thought to be frequently missed because of low disease awareness, missed identification of myelokathexis, and lack of routine genetic testing (Al Ustwani O, et al. Br J Haematol. 2014:164;15-23; Dotta L, et al. Curr Mol Med. 2011;11:317-325; Heusinkveld L, et al. Exp Opin Orphan Drugs. 2017;5(10):813-825). The prevalence of WHIM syndrome has never been systematically studied and is unknown. Determination of prevalence via insurance claims data is hindered by the absence of an International Classification of Diseases (ICD)-10 code for WHIM syndrome as well as inconsistent coding for key symptoms of WHIM syndrome, which are variably penetrant. This study applied an artificial intelligence (AI)/machine learning (ML) model to estimate the potential prevalence of WHIM syndrome using a large US insurance claims database.Methods: A deidentified, longitudinal, patient-level US claims database of >300 million lives was used for this study. Thirty-two patients with genetically confirmed WHIM syndrome were identified from the claims database by linking deidentified patients to known physicians and matching clinical and demographic features. Using this group as a positive training class, an AI/ML model was deployed to identify patients with WHIM look-alike clinical phenotypes in the database. Patients were further filtered based on clinical features to generate low (presence of warts, history of infections, and hypogammaglobulinemia) and high (presence of warts, history of infections, and coding associated with immunodeficiency) prevalence estimates; a final prevalence number for the US was projected to account for incomplete coverage of the US population in the claims database. Finally, insurance codes for disease symptoms, treatments, and management were analyzed to investigate the burden of disease in patients identified by the model.Results: The model showed a high predictive value for distinguishing patients with known WHIM syndrome from a random sample of age-matched patients in the database (area under the curve [AUC] of receiver operating characteristic [ROC] plot, >0.99) as well as a control group of patients with ICD-10 codes defining immunodeficiency conditions (AUC of ROC plot, 0.99). The model generated estimates ranging from 1803 (low) to 3718 (high) patients with WHIM look-alike phenotype in the US. Analysis of medical history in the high-estimate WHIM look-alike group revealed symptomatic and severe disease, as evidenced by ≥1 instance of use of granulocyte colony-stimulating factor (41%) or intravenous immunoglobulin (46%) therapy (both <1% in control group), need for respiratory services (82% vs 8% in control group), presence of hearing loss (18% vs 1% in control group), and high annual utilization of emergency (51%) and hospital (44%) services (vs 8% and 1%, respectively, in control group).Conclusions: The methodology used here provides an approach to explore the prevalence of rare diseases that are often mis- or under-diagnosed and are not captured with a unique ICD-10 code. This study estimates a prevalence of 1803 to 3718 WHIM look-alike patients in the US, supporting the possibility that there may be ≤~3700 patients with either diagnosed or undiagnosed WHIM syndrome in the US. An analysis of the medical history of the WHIM look-alike patients revealed a history of symptomatic and severe disease and a high unmet medical need. Since it is not feasible to definitively confirm a WHIM diagnosis in the look-alike group, it is possible that some of these look-alike patients may have diagnosed or undiagnosed WHIM syndrome, while others may have a clinical phenotype consistent with WHIM syndrome without meeting its classic diagnostic criteria. DisclosuresGarabedian: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Neri: X4 Pharmaceuticals: Current Employment. Seng: X4 Pharmaceuticals: Current Employment. Jones: Real Chemistry (Formerly Swoop/IPM): Current Employment, Other: I was paid salary to perform secondary research project work for client “X4” which resulted in this publication.

Global Phase 3, Randomized, Placebo-Controlled Trial with Open-Label Extension Evaluating the Oral CXCR4 Antagonist Mavorixafor in Patients with WHIM Syndrome (4WHIM): Trial Design and Enrollment

Global Phase 3, Randomized, Placebo-Controlled Trial with Open-Label Extension Evaluating the Oral CXCR4 Antagonist Mavorixafor in Patients with WHIM Syndrome (4WHIM): Trial Design and Enrollment

Mavorixafor, an Oral CXCR4 Antagonist, for Treatment of Patients with WHIM Syndrome: Results from the Long-Term Extension of the Open-Label Phase 2 Study

Background: WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome is a rare, autosomal-dominant primary immunodeficiency. Gain-of-function (GOF) mutations in the CXCR4 gene are the most common cause of WHIM syndrome, manifesting as panleukopenia with severe neutropenia, lymphopenia, and monocytopenia, recurrent bacterial infections, unusual susceptibility to human papillomavirus infections with intractable mucocutaneous warts, and increased risk of malignancy (McDermott DH, et al. Immunol Rev. 2019;2878:91-102). Mavorixafor is an investigational, small-molecule, selective antagonist of the CXCR4 receptor being developed as an oral, once-daily (QD) treatment for patients with WHIM syndrome (Dale DC, et al. Blood. 2020;136(26):2994-3003).Objective: We present an update on the clinical outcomes of patients with WHIM syndrome who continued in the long-term extension of the phase 2 study, highlighting long-term safety and efficacy.Methods: A long-term extension is ongoing as part of the open-label, prospective, dose-escalation, phase 2 study evaluating the safety and efficacy of mavorixafor (NCT03005327) in adults with WHIM syndrome. Individuals with a pathogenic GOF CXCR4 mutation and absolute neutrophil count ≤400/μL and/or absolute lymphocyte count ≤650/μL were included. All provided written informed consent. The primary objectives were to evaluate safety and tolerability and assess safe dosage. Exploratory efficacy end points included changes in infection rates, number of cutaneous warts, and white blood cell counts, compared to baseline. Researchers completed detailed interviews of 4 participants continuing in the study to assess their overall study experience and perceived treatment effects.Results: Five of 8 patients in the dose-finding phase 2 study entered into the long-term extension (LTE); median treatment duration was 148.4 weeks. One patient left the LTE because of study fatigue, and all 5 patients had dose escalation to 400 mg oral QD as of May 2021. As of the November 2020 data cutoff, annualized infection rates decreased from 5.6/year at study baseline to 2.2/year at 40 months' treatment, providing evidence of persistent reduction of infections over time. At doses of 300 and 400mg QD (n=7), the mean time above threshold for ANC and ALC were 12.7 hours (SD ± 9.8) and 16.9 hours (SD ± 5.9) compared to 2.1 hours (SD ± 3.3) and 11.5 hours (SD ± 5.9) at doses ≤200 mg QD, respectively. One patient experienced a 79% reduction in warts. Safety data review at May 2021 showed that there were 12 minor treatment-emergent adverse events (grade 1) with long-term treatment (46 months), no treatment-related infections of grade 3 or higher, no treatment-related serious adverse events, and no clinically significant laboratory abnormalities with mavorixafor treatment. Patient interviews revealed that all 4 LTE participants experienced good tolerability of mavorixafor and decreased frequency, severity, and duration of infections and decreased hospital/doctor visits. Three of 4 participants reported previous need for prophylactic treatment to prevent infection of minor wounds, but with mavorixafor, minor wounds healed without infection or need for prophylaxis. The mechanism of action of mavorixafor was of interest to 3 of 4 participants, who found it important that treatment address the underlying cause of disease, not simply the symptoms. Two participants reported a QOL improvement, and the other 2 reported that WHIM syndrome never affected their QOLConclusion: Ongoing long-term treatment of adults with WHIM syndrome with mavorixafor 300 to 400mg shows durable increase in neutrophils and lymphocytes and sustained improvements in infections and warts. Detailed patient interviews for patient global impression of changes are consistent with sustained clinical benefit of long-term treatment. Mavorixafor has the potential to be a safe, effective, and long-term therapy targeting the underlying cause of WHIM syndrome. A global phase 3 registrational study is ongoing. DisclosuresDale: X4 Pharmaceuticals: Consultancy, Honoraria, Research Funding. Firkin: X4 Pharmaceuticals: Research Funding. Bolyard: X4 Pharmaceuticals: Research Funding. Tang: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Jiang: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. MacLeod: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Cadavid: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company. Hu: X4 Pharmaceuticals: Current Employment, Current equity holder in publicly-traded company.

Mesenchymal Stem/Stromal Cells Overexpressing CXCR4R334X Revealed Enhanced Migration: A Lesson Learned from the Pathogenesis of WHIM Syndrome

C-X-C chemokine receptor type 4 (CXCR4), initially recognized as a co-receptor for HIV, contributes to several disorders, including the WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome. CXCR4 binds to its ligand SDF-1 to make an axis involved in the homing property of stem cells. This study aimed to employ WHIM syndrome pathogenesis as an inspirational approach to reinforce cell therapies. Wild type and WHIM-type variants of the CXCR4 gene were chemically synthesized and cloned in the pCDH-513B-1 lentiviral vector. Molecular cloning of the synthetic genes was confirmed by DNA sequencing, and expression of both types of CXCR4 at the protein level was confirmed by western blotting in HEK293T cells. Human adipose-derived mesenchymal stem cells (Ad-MSCs) were isolated, characterized, and subjected to lentiviral transduction with Wild type and WHIM-type variants of CXCR4. The presence of copGFP-positive MSCs confirmed the high efficiency of transduction. The migration ability of both groups of transduced cells was then assessed by transwell migration assay in the presence or absence of a CXCR4-blocking agent. Our qRT-PCR results showed overexpression of CXCR4 at mRNA level in both groups of transduced MSCs, and expression of WHIM-type CXCR4 was significantly higher than Wild type CXCR4 (P<0.05). Our results indicated that the migration of genetically modified MSCs expressing WHIM-type CXCR4 had significantly enhanced towards SDF1 in comparison with Wild type CXCR4 (P<0.05), while it was reduced after treatment with CXCR4 antagonist. These data suggest that overexpression of WHIM-type CXCR4 could lead to enhanced and sustained expression of CXCR4 on human MSCs, which would increase their homing capability; hence it might be an appropriate strategy to improve the efficiency of cell-based therapies.

Effect of the CXCR4 antagonist plerixafor on endogenous neutrophil dynamics in the bone marrow, lung and spleen.

Treatment with the CXCR4 antagonist, plerixafor (AMD3100), has been proposed for clinical use in patients with WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome and in pulmonary fibrosis. However, there is controversy with respect to the impact of plerixafor on neutrophil dynamics in the lung, which may affect its safety profile. In this study, we investigated the kinetics of endogenous neutrophils by direct imaging, using confocal intravital microscopy in mouse bone marrow, spleen, and lungs. Neutrophils are observed increasing their velocity and exiting the bone marrow following plerixafor administration, with a concomitant increase in neutrophil numbers in the blood and spleen, while the marginated pool of neutrophils in the lung microvasculature remained unchanged in terms of numbers and cell velocity. Use of autologous radiolabeled neutrophils and SPECT/CT imaging in healthy volunteers showed that plerixafor did not affect GM-CSF-primed neutrophil entrapment or release in the lungs. Taken together, these data suggest that plerixafor causes neutrophil mobilization from the bone marrow but does not impact on lung marginated neutrophil dynamics and thus is unlikely to compromise respiratory host defense both in humans and mice.

Enhancement of stem cell engraftment on a WHIM.

WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome is a genetic autoimmune disorder that results from gain-of-function mutations in the gene encoding chemokine receptor CXCR4. A previous study characterized a patient with WHIM who underwent a chromothriptic event that resulted in spontaneous deletion of the WHIM allele in a single hematopoietic stem cell and subsequent cure of the disease. In this issue of the JCI, Gao et al. extend this work and show that Cxcl4-haplosufficient bone marrow has a selective advantage for long-term engraftment in murine WHIM models. Moreover, successful engraftment occurred without prior conditioning of recipients. Together, these results have important implications for improving hematopoietic stem/progenitor cell transplant not only for patients with WHIM but also for all patients who may require the procedure.

Cxcr4-haploinsufficient bone marrow transplantation corrects leukopenia in an unconditioned WHIM syndrome model.

For gene therapy of gain-of-function autosomal dominant diseases, either correcting or deleting the disease allele is potentially curative. To test whether there may be an advantage of one approach over the other for WHIM (warts, hypogammaglobulinemia, infections, and myelokathexis) syndrome - a primary immunodeficiency disorder caused by gain-of-function autosomal dominant mutations in chemokine receptor CXCR4 - we performed competitive transplantation experiments using both lethally irradiated WT (Cxcr4+/+) and unconditioned WHIM (Cxcr4+/w) recipient mice. In both models, hematopoietic reconstitution was markedly superior using BM cells from donors hemizygous for Cxcr4 (Cxcr4+/o) compared with BM cells from Cxcr4+/+ donors. Remarkably, only approximately 6% Cxcr4+/o hematopoietic stem cell (HSC) chimerism after transplantation in unconditioned Cxcr4+/w recipient BM supported more than 70% long-term donor myeloid chimerism in blood and corrected myeloid cell deficiency in blood. Donor Cxcr4+/o HSCs differentiated normally and did not undergo exhaustion as late as 465 days after transplantation. Thus, disease allele deletion resulting in Cxcr4 haploinsufficiency was superior to disease allele repair in a mouse model of gene therapy for WHIM syndrome, allowing correction of leukopenia without recipient conditioning.

Novel Role for NFAT3 in ERK-Mediated Regulation of CXCR4

The G-protein coupled chemokine (C-X-C motif) receptor CXCR4 is linked to cancer, HIV, and WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome. While CXCR4 is reported to be overexpressed in multiple human cancer types and many hematological cancer cell lines, we have observed poor in vitro cell surface expression of CXCR4 in many solid tumor cell lines. We explore further the possible factors and pathways involved in regulating CXCR4 expression. Here, we showed that MEK-ERK signaling pathway and NFAT3 transcriptional factor plays a novel role in regulating CXCR4 expression. When cultured as 3D spheroids, HeyA8 ovarian tumor cells showed a dramatic increase in surface CXCR4 protein levels as well as mRNA transcripts. Furthermore, HeyA8 3D spheroids showed a decrease in phospho-ERK levels when compared to adherent cells. The treatment of adherent HeyA8 cells with an inhibitor of the MEK-ERK pathway, U0126, resulted in a significant increase in surface CXCR4 expression. Additional investigation using the PCR array assay comparing adherent to 3D spheroid showed a wide range of transcription factors being up-regulated, most notably a> 20 fold increase in NFAT3 transcription factor mRNA. Finally, chromatin immunoprecipitation (ChIP) analysis showed that direct binding of NFAT3 on the CXCR4 promoter corresponds to increased CXCR4 expression in HeyA8 ovarian cell line. Taken together, our results suggest that high phospho-ERK levels and NFAT3 expression plays a novel role in regulating CXCR4 expression.

The WHIM-like CXCR4(S338X) somatic mutation activates AKT and ERK, and promotes resistance to ibrutinib and other agents used in the treatment of Waldenstrom's Macroglobulinemia.

CXCR4(WHIM) somatic mutations are common Waldenstrom's Macroglobulinemia (WM), and are associated with clinical resistance to ibrutinib. We engineered WM cells to express the most common WHIM (Warts, Hypogammaglobulinemia, Infections and Myelokathexis), CXCR(S338X) mutation in WM. Following SDF-1a stimulation, CXCR4(S338X) WM cells exhibited decreased receptor internalization, enhanced and sustained AKT kinase (AKT) and extracellular regulated kinase (ERK) signaling, decreased poly (ADP-ribose) polymerase and caspase 3 cleavage, and decreased Annexin V staining versus CXCR4 wild-type (WT) cells. CXCR4(S338X)-related signaling and survival effects were blocked by the CXCR4 inhibitor AMD3100. SDF-1a-treated CXCR4(S338X) WM cells showed sustained AKT and ERK activation and decreased apoptotic changes versus CXCR4(WT) cells following ibrutinib treatment, findings which were also reversed by AMD3100. AKT or ERK antagonists restored ibrutinib-triggered apoptotic changes in SDF-1a-treated CXCR4(S338X) WM cells demonstrating their role in SDF-1a-mediated ibrutinib resistance. Enhanced bone marrow pAKT staining was also evident in CXCR4(WHIM) versus CXCR4(WT) WM patients, and remained active despite ibrutinib therapy in CXCR4(WHIM) patients. Last, CXCR4(S338X) WM cells showed varying levels of resistance to other WM relevant therapeutics, including bendamustine, fludarabine, bortezomib and idelalisib in the presence of SDF-1a. These studies demonstrate a functional role for CXCR4(WHIM) mutations, and provide a framework for investigation of CXCR4 inhibitors in WM.

Somatic mutations in MYD88 and CXCR4 are determinants of clinical presentation and overall survival in Waldenström macroglobulinemia

AbstractWhole genome sequencing has revealed activating somatic mutations in MYD88 (L265P) and CXCR4 in Waldenström macroglobulinemia (WM). CXCR4 somatic mutations in WM are the first ever reported in human cancer and are similar to nonsense (NS) and frameshift (FS) germline mutations found in warts, hypogammaglobulinemia, infections and myelokathexis (WHIM) syndrome. We genotyped lymphoplasmacytic cells from 175 WM patients and observed significantly higher bone marrow (BM) disease involvement, serum immunoglobulin-M levels, and symptomatic disease requiring therapy, including hyperviscosity syndrome in those patients with MYD88L265PCXCR4WHIM/NS mutations (P < .03). Patients with MYD88L265PCXCR4WHIM/FS or MYD88L265PCXCR4WILDTYPE (WT) had intermediate BM and serum immunoglobulin-M levels; those with MYD88WTCXCR4WT showed lowest BM disease burden. Fewer patients with MYD88L265P and CXCR4WHIM/FS or NS vs MYD88L265PCXCR4WT presented with adenopathy (P < .01), further delineating differences in disease tropism based on CXCR4 status. Neither MYD88 nor CXCR4 mutations correlated with SDF-1a (RS1801157) polymorphisms in 54 patients who were genotyped for these variants. Unexpectedly, risk of death was not impacted by CXCR4 mutation status, but by MYD88WT status (hazard ratio 10.54; 95% confidence interval 2.4-46.2, P = .0018). Somatic mutations in MYD88 and CXCR4 are important determinants of clinical presentation and impact overall survival in WM. Targeted therapies directed against MYD88 and/or CXCR4 signaling may provide a personalized treatment approach to WM.

Inhibitors of CXC chemokine receptor type 4

The CXC chemokine receptor type 4 (CXCR4), which is a G-protein coupled receptor, and its ligand CXCL12 play an important role in neutrophil homeostasis and inflammation. This review focuses on involvement of the CXCL12/CXCR4 axis in inflammation and different inflammatory diseases and depicts that blocking CXCR4 is an attractive therapeutic strategy. Binding of CXCL12 to CXCR4 retains immature neutrophils in the bone marrow and also participates in leukocyte recruitment into inflamed tissue. The CXCL12/CXCR4 axis is also involved in several inflammatory processes and diseases including the WHIM (warts, hypogammaglobulinemia, infections and myelokathexis) syndrome, HIV, autoimmune disorders, ischemic injury, and pulmonary fibrosis. Based on these findings, blocking CXCR4 seems to be a therapeutic strategy in inflammatory diseases. Several promising CXCR4 antagonists are in different stages of development and clinical trials. Currently, only plerixafor (AMD3100) has been approved for short-term application.

Abstract 1801: ERK-mediated regulation of NFAT3 enhances CXCR4 expression in HeyA8 ovarian cell line.

Abstract The G-protein coupled chemokine (C-X-C motif) receptor CXCR4 is linked to cancer, HIV, and WHIM (Warts, Hypogammaglobulinemia, Infections, and Myelokathexis) syndrome. While CXCR4 is widely studied and characterized extensively to be over-expressed in multiple human tumor tissues, we have seen poor surface CXCR4 expression in many solid tumor cell lines in vitro. To better understand how CXCR4 is regulated, cells grown under 3-D spheroid conditions were compared to normal adherent culturing conditions. When cultured as 3D spheroids, HeyA8 cells showed a dramatic increase in surface CXCR4 protein levels as well as mRNA transcripts. Furthermore, HeyA8 3D spheroids showed a decrease in pERK levels when compared to adherent cells. Using an inhibitor of the MEK-ERK pathway, the treatment of adherent HeyA8 cells with U0126 resulted in a significant increase in surface CXCR4 expression similar to 3D spheroids. Additional investigation using PCR array showed a wide range of transcription factors being up-regulated but notably a &amp;gt; 20 fold increase in NFAT3 transcription factor. Using a calcineurin inhibitor, cyclosporin A diminished the U0126 treated up-regulation of CXCR4 surface expression. Finally, Chromatin Immunoprecipitation analysis showed direct binding of NFAT3 on the CXCR4 promoter to increase CXCR4 expression in HeyA8 ovarian cell line. Taken together, our results suggest that phospho-ERK levels regulate CXCR4 expression through the NFAT3 signaling pathway. Citation Format: Keven Huang, Christine Kiefer, Adeela Kamal. ERK-mediated regulation of NFAT3 enhances CXCR4 expression in HeyA8 ovarian cell line. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1801. doi:10.1158/1538-7445.AM2013-1801 Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Whole Genome Sequencing Identifies Recurring Somatic Mutations in the C-Terminal Domain of CXCR4, Including a Gain of Function Mutation in Waldenstrom's Macroglobinemia.

Abstract 2715 Introduction:Waldenstrom's Macroglobulinemia (WM) is an indolent non-Hodgkin's lymphoma characterized by the accumulation of IgM secreting lymphoplasmacytic cells (LPC) in the bone marrow. Using paired normal/WM lymphoplasmacytic cell paired tissues and whole genome sequencing (WGS), we identified somatic mutations in the CXC chemokine receptor 4 (CXCR4) gene which were present in 16/55 (29%) WM patients. CXCR4 is a G-protein-coupled receptor, together with its ligand, the stromal cell- derived factor-1(CXCL12/SDF-1), play an important role in leukocyte and lymphocyte hematopoiesis and trafficking. Upon SDF-1 stimulation, CXCR4 is phosphorylated and interacts with b-arrestins, which then trigger extracellular signal-regulated kinase (ERK) MAPKs and chemotaxis. CXCR4 signaling is then terminated through receptor internalization which is mediated via phosphorylation of its C-terminal tail. Methods:Sanger sequencing was used to validate WGS results. To clarify the functional significance of one of the most common somatic mutation identified (C1013G), cloning by PCR was undertaken from CD19+ bone marrow cells from a WM patient with the C1013G CXCR4 (C1013G-CXCR4) mutation. Wild type (WT) and C1013G-CXCR4 cDNAs were subcloned into plenti-IRES-GFP vector, and transduced using an optimized lentiviral based strategy for WM cells into BCWM.1 WM cells. Five days after transduction, GFP positive cells were sorted and used for functional studies. Surface expression of CXCR4 was determined by FACS using PE-conjugated anti-CXCR4 monoclonal antibody 12G5. CXCR4 internalization was studied by comparing CXCR4 surface expression before and after SDF-1 stimulation. Chemotaxis studies were performed using a transwell assay. The expression of phosphorylated ERK1/2 and total ERK2 was determined by western blot. Results:Validated somatic mutations in CXCR4 were all present in the C-terminal domain and included premature stop codons (C1013A; C1013G), and frameshift mutations. Importantly, the identified mutations are similar to those reported in the germline of patients with WHIM (Warts, Hypogammaglobulinemia, Infections and Myelokathexis) Syndrome, a dominant autosomal genetic disorder caused by tonic CXCR4 activation by impairment of CXCR4 internalization, and stimulation of G-protein-dependent responses, and chemotaxis. Consistent with such a role, SDF-1a stimulation showed decreased internalization of CXCR4 in C1013G-CXCR4 versus WT CXCR4 transduced BCWM.1 WM cells. SDF-1a stimulated ERK1/2 phosphorylation was also more robust C1013G-CXCR4 versus WT CXCR4 expressing cells. Lastly, C1013G-CXCR4 transduced cells displayed stronger migratory response toward SDF-1a versus WT CXCR4 expressing BCWM.1 cells. Conclusions:C-terminal domain somatic mutations are common in WM and overlap with germline mutation identified in WHIM syndrome. Moreover, the most common of these mutations (C1013G) confers gain of function including decreased CXCR4 internalization, more robust ERK ½ phosphorylation, and chemotaxis. The findings provide new insights into the pathogenesis of WM, and a framework for the study of CXCR4 inhibitors for WM therapy. Disclosures:Treon:Onyx: Membership on an entity's Board of Directors or advisory committees; Millennium: Membership on an entity's Board of Directors or advisory committees.

A report of WHIM syndrome (myelokathexis)

A report of WHIM syndrome (myelokathexis)