Langerhans cell histiocytosis: NACHO update on progress, chaos, and opportunity on the path to rational cures

Langerhans cell histiocytosis (LCH) is a myeloid neoplastic disorder characterized by lesions with CD1a-positive/Langerin (CD207)-positive histiocytes and inflammatory infiltrate that can cause local tissue damage and systemic inflammation. Clinical presentations range from single lesions with minimal impact to life-threatening disseminated disease. Therapy for systemic LCH has been established through serial trials empirically testing different chemotherapy agents and durations of therapy. However, fewer than 50% of patients who have disseminated disease are cured with the current standard-of-care vinblastine/prednisone/(mercaptopurine), and treatment failure is associated with long-term morbidity, including the risk of LCH-associated neurodegeneration. Historically, the nature of LCH-whether a reactive condition versus a neoplastic/malignant condition-was uncertain. Over the past 15 years, seminal discoveries have broadly defined LCH pathogenesis; specifically, activating mitogen-activated protein kinase pathway mutations (most frequently, BRAFV600E) in myeloid precursors drive lesion formation. LCH therefore is a clonal neoplastic disorder, although secondary inflammatory features contribute to the disease. These paradigm-changing insights offer a promise of rational cures for patients based on individual mutations, clonal reservoirs, and extent of disease. However, the pace of clinical trial development behind lags the kinetics of translational discovery. In this review, the authors discuss the current understanding of LCH biology, clinical characteristics, therapeutic strategies, and opportunities to improve outcomes for every patient through coordinated agent prioritization and clinical trial efforts.

Evaluation of Culture Conducive to Academic Success by Gender at a Comprehensive Cancer Center

INTRODUCTION

The primary objective of this study was to determine whether workplace culture in academic oncology differed by gender, during the COVID-19 pandemic.

MATERIALS AND METHODS

We used the Culture Conducive to Women's Academic Success (CCWAS), a validated survey tool, to investigate the academic climate at an NCI-designated Cancer Center. We adapted the CCWAS to be applicable to people of all genders. The full membership of the Cancer Center was surveyed (total faculty = 429). The questions in each of 4 CCWAS domains (equal access to opportunities, work-life balance, freedom from gender bias, and leadership support) were scored using a 5-point Likert scale. Median score and interquartile ranges for each domain were calculated.

RESULTS

A total of 168 respondents (men = 58, women = 106, n = 4 not disclosed) submitted survey responses. The response rate was 39% overall and 70% among women faculty. We found significant differences in perceptions of workplace culture by gender, both in responses to individual questions and in the overall score in the following domains: equal access to opportunities, work-life balance, and leader support, and in the total score for the CCWAS.

CONCLUSIONS

Our survey is the first of its kind completed during the COVID-19 pandemic at an NCI-designated Cancer Center, in which myriad factors contributed to burnout and workplace challenges. These results point to specific issues that detract from the success of women pursuing careers in academic oncology. Identifying these issues can be used to design and implement solutions to improve workforce culture, mitigate gender bias, and retain faculty.

Pre-and post-HSCT use of TKI therapy for fusion-driven B-ALL: A case series of five pediatric, adolescent and young adult patients

BACKGROUND

The development of tyrosine kinase inhibitors (TKIs) has significantly improved survival rates among patients with Philadelphia chromosome (Ph+) B cell acute lymphoblastic leukemia (B-ALL). Ph-like B-ALL patients lack the BCR::ABL1 translocation but share gene expression profiles with Ph+ B-ALL. The role of TKIs for Ph-like patients pre- and post-hematopoietic stem cell transplantation (HSCT) is not yet clear.

CASE

Here we present five cases of pediatric, adolescent, and young adult patients who presented with Ph-like B-ALL or CML in B-ALL blast phase who were treated with personalized TKI regimens pre- and post-HSCT.

CONCLUSION

This report describes several novel Ph-like fusions as well as combinations of TKIs with chemotherapy or immunotherapy not yet reported in the pediatric population. This case series provides real-world experience highlighting the potential application of pre- and post-HSCT use of TKIs in a subset of patients with targetable fusions.

Framework humanization optimizes potency of anti-CD72 nanobody CAR-T cells for B-cell malignancies

BACKGROUND

Approximately 50% of patients who receive anti-CD19 CAR-T cells relapse, and new immunotherapeutic targets are urgently needed. We recently described CD72 as a promising target in B-cell malignancies and developed nanobody-based CAR-T cells (nanoCARs) against it. This cellular therapy design is understudied compared with scFv-based CAR-T cells, but has recently become of significant interest given the first regulatory approval of a nanoCAR in multiple myeloma.

METHODS

We humanized our previous nanobody framework regions, derived from llama, to generate a series of humanized anti-CD72 nanobodies. These nanobody binders were inserted into second-generation CD72 CAR-T cells and were evaluated against preclinical models of B cell acute lymphoblastic leukemia and B cell non-Hodgkin's lymphoma in vitro and in vivo. Humanized CD72 nanoCARs were compared with parental ("NbD4") CD72 nanoCARs and the clinically approved CD19-directed CAR-T construct tisangenlecleucel. RNA-sequencing, flow cytometry, and cytokine secretion profiling were used to determine differences between the different CAR constructs. We then used affinity maturation on the parental NbD4 construct to generate high affinity binders against CD72 to test if higher affinity to CD72 improved antitumor potency.

RESULTS

Toward clinical translation, here we humanize our previous nanobody framework regions, derived from llama, and surprisingly discover a clone ("H24") with enhanced potency against B-cell tumors, including patient-derived samples after CD19 CAR-T relapse. Potentially underpinning improved potency, H24 has moderately higher binding affinity to CD72 compared with a fully llama framework. However, further affinity maturation (KD<1 nM) did not lead to improvement in cytotoxicity. After treatment with H24 nanoCARs, in vivo relapse was accompanied by CD72 antigen downregulation which was partially reversible. The H24 nanobody clone was found to have no off-target binding and is therefore designated as a true clinical candidate.

CONCLUSION

This work supports translation of H24 CD72 nanoCARs for refractory B-cell malignancies, reveals potential mechanisms of resistance, and unexpectedly demonstrates that nanoCAR potency can be improved by framework alterations alone. These findings may have implications for future engineering of nanobody-based cellular therapies.

Mature B-cell lymphomas in adolescents and young adults

Pediatric non-Hodgkin lymphoma includes over 30 histologies (many with subtypes), with approximately 800 cases per year in the US, compared to >60,000 cases of adult NHL annually. Improvements in survival in pediatric and adolescent mature B cell NHL over the past 5 decades align with the overall success of the cooperative trial model with dramatic improvements in outcomes through dose escalation of chemotherapy and, more recently, targeted therapy with rituximab. Pediatric dose-intense strategies carry risks of long-term consequences, but treatment failure is nearly universally fatal. By comparison, adult mature B cell lymphoma is typically less aggressive and treated with less intense chemotherapy. Optimizing therapy for adolescents and young adults remains a major challenge that requires creative solutions, including engineering study groups to combine biologically comparable adult and pediatric populations and developing effective salvage strategies that will ultimately be required for investigations of front-line dose reduction. In this review, we discuss challenges and opportunities for improving outcomes for adolescents and young adults with high-grade mature B cell lymphomas, diffuse large B cell lymphoma, and primary mediastinal B cell lymphoma.

Tisagenlecleucel utilisation and outcomes across refractory, first relapse and multiply relapsed B-cell acute lymphoblastic leukemia: a retrospective analysis of real-world patterns

Background

Tisagenlecleucel was approved by the Food and Drug Administration (FDA) in 2017 for refractory B-cell acute lymphoblastic leukemia (B-ALL) and B-ALL in ≥2nd relapse. Outcomes of patients receiving commercial tisagenlecleucel upon 1st relapse have yet to be established. We aimed to report real-world tisagenlecleucel utilisation patterns and outcomes across indications, specifically including patients treated in 1st relapse, an indication omitted from formal FDA approval.

Methods

We conducted a retrospective analysis of real-world tisagenlecleucel utilisation patterns across 185 children and young adults treated between August 30, 2017 and March 6, 2020 from centres participating in the Pediatric Real-World CAR Consortium (PRWCC), within the United States. We described definitions of refractory B-ALL used in the real-world setting and categorised patients by reported Chimeric Antigen Receptor (CAR) T-cell indication, including refractory, 1st relapse and ≥2nd relapse B-ALL. We analysed baseline patient characteristics and post-tisagenlecleucel outcomes across defined cohorts.

Findings

Thirty-six percent (n = 67) of our cohort received tisagenlecleucel following 1st relapse. Of 66 evaluable patients, 56 (85%, 95% CI 74-92%) achieved morphologic complete response. Overall-survival (OS) and event-free survival (EFS) at 1-year were 69%, (95% CI 58-82%) and 49%, (95% CI 37-64%), respectively, with survival outcomes statistically comparable to remaining patients (OS; p = 0.14, EFS; p = 0.39). Notably, toxicity was increased in this cohort, warranting further study. Interestingly, of 30 patients treated for upfront refractory disease, 23 (77%, 95% CI 58-90%) had flow cytometry and/or next-generation sequencing (NGS) minimum residual disease (MRD)-only disease at the end of induction, not meeting the historic morphologic definition of refractory.

Interpretation

Our findings suggested that tisagenlecleucel response and survival rates overlap across patients treated with upfront refractory B-ALL, B-ALL ≥2nd relapse and B-ALL in 1st relapse. We additionally highlighted that definitions of refractory B-ALL are evolving beyond morphologic measures of residual disease.

Funding

St. Baldrick's/Stand Up 2 Cancer, Parker Institute for Cancer Immunotherapy, Virginia and D.K. Ludwig Fund for Cancer Research.

Mediport use as an acceptable standard for CAR T cell infusion

Introduction

Mediport use as a clinical option for the administration of chimeric antigen receptor T cell (CAR T cell) therapy in patients with B-cell malignancies has yet to be standardized. Concern for mediport dislodgement, cell infiltration, and ineffective therapy delivery to systemic circulation has resulted in variable practice with intravenous administration of CAR T cell therapy. With CAR T cell commercialization, it is important to establish practice standards for CAR T cell delivery. We conducted a study to establish usage patterns of mediports in the clinical setting and provide a standard of care recommendation for mediport use as an acceptable form of access for CAR T cell infusions.

Methods

In this retrospective cohort study, data on mediport use and infiltration rate was collected from a survey across 34 medical centers in the Pediatric Real-World CAR Consortium, capturing 504 CAR T cell infusion routes across 489 patients. Data represents the largest, and to our knowledge sole, report on clinical CAR T cell infusion practice patterns since FDA approval and CAR T cell commercialization in 2017.

Results

Across 34 sites, all reported tunneled central venous catheters, including Broviac® and Hickman® catheters, as accepted standard venous options for CAR T cell infusion. Use of mediports as a standard clinical practice was reported in 29 of 34 sites (85%). Of 489 evaluable patients with reported route of CAR T cell infusion, 184 patients were infused using mediports, with no reported incidences of CAR T cell infiltration.

Discussion/Conclusion

Based on current clinical practice, mediports are a commonly utilized form of access for CAR T cell therapy administration. These findings support the safe practice of mediport usage as an accepted standard line option for CAR T cell infusion.

Children's Oncology Group's 2023 blueprint for research: Non-Hodgkin lymphoma

Pediatric non-Hodgkin lymphoma (NHL) includes over 30 histologies (many with subtypes), with approximately 800 cases per year in the United States. Improvements in survival in NHL over the past 5 decades align with the overall success of the cooperative trial model with dramatic improvements in outcomes. As an example, survival for advanced Burkitt lymphoma is now >95%. Major remaining challenges include survival for relapsed and refractory disease and long-term morbidity in NHL survivors. Langerhans cell histiocytosis (LCH) was added to the NHL Committee portfolio in recognition of LCH as a neoplastic disorder and the tremendous unmet need for improved outcomes. The goal of the Children' Oncology Group NHL Committee is to identify optimal cures for every child and young adult with NHL (and LCH). Further advances will require creative solutions, including engineering study groups to combine rare populations, biology-based eligibility, alternative endpoints, facilitating international collaborations, and coordinated correlative biology.

HLH-like toxicities predict poor survival after the use of tisagenlecleucel in children and young adults with B-ALL

Chimeric antigen receptor-associated hemophagocytic lymphohistiocytosis (HLH)-like toxicities (LTs) involving hyperferritinemia, multiorgan dysfunction, coagulopathy, and/or hemophagocytosis are described as occurring in a subset of patients with cytokine release syndrome (CRS). Case series report poor outcomes for those with B-cell acute lymphoblastic leukemia (B-ALL) who develop HLH-LTs, although larger outcomes analyses of children and young adults (CAYAs) with B-ALL who develop these toxicities after the administration of commercially available tisagenlecleucel are not described. Using a multi-institutional database of 185 CAYAs with B-ALL, we conducted a retrospective cohort study including groups that developed HLH-LTs, high-grade (HG) CRS without HLH-LTs, or no to low-grade (NLG) CRS without HLH-LTs. Primary objectives included characterizing the incidence, outcomes, and preinfusion factors associated with HLH-LTs. Among 185 CAYAs infused with tisagenlecleucel, 26 (14.1%) met the criteria for HLH-LTs. One-year overall survival and relapse-free survival were 25.7% and 4.7%, respectively, in those with HLH-LTs compared with 80.1% and 57.6%, respectively, in those without. In multivariable analysis for death, meeting criteria for HLH-LTs carried a hazard ratio of 4.61 (95% confidence interval, 2.41-8.83), controlling for disease burden, age, and sex. Patients who developed HLH-LTs had higher pretisagenlecleucel disease burden, ferritin, and C-reactive protein levels and lower platelet and absolute neutrophil counts than patients with HG- or NLG-CRS without HLH-LTs. Overall, CAYAs with B-ALL who developed HLH-LTs after tisagenlecleucel experienced high rates of relapse and nonrelapse mortality, indicating the urgent need for further investigations into prevention and optimal management of patients who develop HLH-LTs after tisagenlecleucel.

How I approach B-lymphoblastic lymphoma in children

There are limited data pertaining to the prognostic features and optimal therapeutic approach for the 20%-25% of children with lymphoblastic lymphoma (LLy) who have the B-lymphoblastic subtype. Outcomes are favorable following treatment modeled after acute lymphoblastic leukemia (ALL) regimens, but prognosis is dismal after relapse, and there are no established features for predicting therapy response. Ongoing US and international trials will include the largest cohort of uniformly treated patients with B-LLy to date, providing an opportunity to define clinical and molecular predictors of relapse and to establish a standard of care for treatment to improve outcomes for this rare pediatric cancer.

Allowing Relationships to Unfold: Consult Reason and Topics Discussed in Initial and Subsequent Palliative Care Visits Among Children Who Died From Relapsed/Refractory Cancer

Background: Children with relapsed/refractory cancer have a myriad of palliative care needs. While pediatric oncology clinicians meet many of these needs, studies suggest that these children often have distressing symptoms and that families feel unprepared for their child's end-of-life (EOL). Oncology clinicians cite barriers to pediatric palliative care (PPC) consultation, including concerns that PPC teams will upset families with EOL discussions. This study evaluated topics addressed by PPC teams over the course of their relationship with children who died from cancer. Methods: Retrospective chart review of children who were diagnosed with relapsed/refractory cancer, received PPC consultation at an academic children's hospital, and died between January 2008 and January 2017. Information was extracted regarding the child's treatment, EOL care, and the content of PPC consultation over the course of the team's relationship with the child/family. Results: Fifty-six children were included in the analysis. The most frequent reasons for the initial consult were pain (n = 31, 55%) and non-pain symptom management (n = 18, 32%). At the initial consult, the PPC team most often discussed symptom management and psychosocial support. Prognosis was not discussed in any initial consult. Over subsequent visits, the PPC team expanded their scope of discussion to include goals of care, advance care planning, and hospice. Discussion: Concerns from oncology clinicians that PPC teams will extend beyond the reasons for initial consult into prognostic/EOL discussions at the first visit may be unfounded. Greater familiarity with PPC team practices may facilitate more timely consultation of PPC and its complementary set of services.

Outcomes After Nonresponse and Relapse Post-Tisagenlecleucel in Children, Adolescents, and Young Adults With B-Cell Acute Lymphoblastic Leukemia

PURPOSE

Nonresponse and relapse after CD19-chimeric antigen receptor (CAR) T-cell therapy continue to challenge survival outcomes. Phase II landmark data from the ELIANA trial demonstrated nonresponse and relapse rates of 14.5% and 28%, respectively, whereas use in the real-world setting showed nonresponse and relapse rates of 15% and 37%. Outcome analyses describing fate after post-CAR nonresponse and relapse remain limited. Here, we aim to establish survival outcomes after nonresponse and both CD19+ and CD19- relapses and explore treatment variables associated with inferior survival.

METHODS

We conducted a retrospective multi-institutional study of 80 children and young adults with B-cell acute lymphoblastic leukemia experiencing nonresponse (n = 23) or relapse (n = 57) after tisagenlecleucel. We analyze associations between baseline characteristics and these outcomes and establish survival rates and salvage approaches.

RESULTS

The overall survival (OS) at 12 months was 19% across nonresponders (n = 23; 95% CI, 7 to 50). Ninety-five percent of patients with nonresponse had high preinfusion disease burden. Among 156 morphologic responders, the cumulative incidence of relapse was 37% (95% CI, 30 to 47) at 12 months (CD19+; 21% [15 to 29], CD19-; 16% [11 to 24], median follow-up; 380 days). Across 57 patients experiencing relapse, the OS was 52% (95% CI, 38 to 71) at 12 months after time of relapse. Notably, CD19- relapse was associated with significantly decreased OS as compared with patients who relapsed with conserved CD19 expression (CD19- 12-month OS; 30% [14 to 66], CD19+ 12-month OS; 68% [49 to 92], P = .0068). Inotuzumab, CAR reinfusion, and chemotherapy were used as postrelapse salvage therapy with greatest frequency, yet high variability in treatment sequencing and responses limits efficacy analysis across salvage approaches.

CONCLUSION

We describe poor survival across patients experiencing nonresponse to tisagenlecleucel. In the post-tisagenlecleucel relapse setting, patients can be salvaged; however, CD19- relapse is distinctly associated with decreased survival outcomes.

Pre-clerkship Teaching and Learning in the Virtual Learning Environment: Lessons Learned and Future Directions

In response to the COVID-19 pandemic, we developed and implemented a theory-informed process to adapt a comprehensive pre-clerkship medical school curriculum to run in the virtual learning environment utilizing sociocultural learning theory and cognitive load theory. Of 124 student respondents, 45% rated virtual learning as very or extremely effective, and 49% as moderately effective. Positive aspects of virtual learning included effectiveness of chat moderators, displaying pronouns on Zoom, active learning technology, and captioning and transcription. Negative aspects included access to technology and feeling isolated from community. Overall course ratings, examination performance, and work hours did not differ pre- and post-implementation.

Disease Burden Affects Outcomes in Pediatric and Young Adult B-Cell Lymphoblastic Leukemia After Commercial Tisagenlecleucel: A Pediatric Real-World Chimeric Antigen Receptor Consortium Report

PURPOSE

Tisagenlecleucel is a CD19-specific chimeric antigen receptor T-cell therapy, US Food and Drug Administration-approved for children, adolescents, and young adults (CAYA) with relapsed and/or refractory (RR) B-cell acute lymphoblastic leukemia (B-ALL). The US Food and Drug Administration registration for tisagenlecleucel was based on a complete response (CR) rate of 81%, 12-month overall survival (OS) of 76%, and event-free survival (EFS) of 50%. We report clinical outcomes and analyze covariates of outcomes after commercial tisagenlecleucel.

METHODS

We conducted a retrospective, multi-institutional study of CAYA with RR B-ALL across 15 US institutions, who underwent leukapheresis shipment to Novartis for commercial tisagenlecleucel. A total of 200 patients were included in an intent-to-treat response analysis, and 185 infused patients were analyzed for survival and toxicity.

RESULTS

Intent-to-treat analysis demonstrates a 79% morphologic CR rate (95% CI, 72 to 84). The infused cohort had an 85% CR (95% CI, 79 to 89) and 12-month OS of 72% and EFS of 50%, with 335 days of median follow-up. Notably, 48% of patients had low-disease burden (< 5% bone marrow lymphoblasts, no CNS3, or other extramedullary disease), or undetectable disease, pretisagenlecleucel. Univariate and multivariate analyses associate high-disease burden (HB, ≥ 5% bone marrow lymphoblasts, CNS3, or non-CNS extramedullary) with inferior outcomes, with a 12-month OS of 58% and EFS of 31% compared with low-disease burden (OS; 85%, EFS; 70%) and undetectable disease (OS; 95%, EFS; 72%; P < .0001 for OS and EFS). Grade ≥ 3 cytokine release syndrome and neurotoxicity rates were 21% and 7% overall and 35% and 9% in patients with HB, respectively.

CONCLUSION

Commercial tisagenlecleucel in CAYA RR B-ALL demonstrates efficacy and tolerability. This first analysis of commercial tisagenlecleucel stratified by disease burden identifies HB preinfusion to associate with inferior OS and EFS and increased toxicity.

Tisagenlecleucel outcomes in relapsed/refractory extramedullary ALL: a Pediatric Real World CAR Consortium Report

Chimeric antigen receptor (CAR) T cells have transformed the therapeutic options for relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia. Data for CAR therapy in extramedullary (EM) involvement are limited. Retrospective data were abstracted from the Pediatric Real World CAR Consortium (PRWCC) of 184 infused patients from 15 US institutions. Response (complete response) rate, overall survival (OS), relapse-free survival (RFS), and duration of B-cell aplasia (BCA) in patients referred for tisagenlecleucel with EM disease (both central nervous system (CNS)3 and non-CNS EM) were compared with bone marrow (BM) only. Patients with CNS disease were further stratified for comparison. Outcomes are reported on 55 patients with EM disease before CAR therapy (CNS3, n = 40; non-CNS EM, n = 15). The median age at infusion in the CNS cohort was 10 years (range, <1-25 years), and in the non-CNS EM cohort it was 13 years (range, 2-26 years). In patients with CNS disease, 88% (35 of 40) achieved a complete response vs only 66% (10 of 15) with non-CNS EM disease. Patients with CNS disease (both with and without BM involvement) had 24-month OS outcomes comparable to those of non-CNS EM or BM only (P = .41). There was no difference in 12-month RFS between CNS, non-CNS EM, or BM-only patients (P = .92). No increased toxicity was seen with CNS or non-CNS EM disease (P = .3). Active CNS disease at time of infusion did not affect outcomes. Isolated CNS disease trended toward improved OS compared with combined CNS and BM (P = .12). R/R EM disease can be effectively treated with tisagenlecleucel; toxicity, relapse, and survival rates are comparable to those of patients with BM-only disease. Outcomes for isolated CNS relapse are encouraging.

Ibrutinib significantly inhibited Bruton's tyrosine kinase (BTK) phosphorylation,in-vitro proliferation and enhanced overall survival in a preclinical Burkitt lymphoma (BL) model

Pediatric and adult patients with recurrent/refractory Burkitt lymphoma (BL) continue to have poor outcomes, emphasizing the need for newer therapeutic agents. Bruton's tyrosine kinase (BTK) is activated following B-cell receptor stimulation and in part regulates normal B-cell development. Ibrutinib, a selective and irreversible BTK inhibitor, has been efficacious in chronic lymphocytic leukemia (CLL), mantle cell lymphoma (MCL), Waldenström's macroglobulinemia, and marginal zone lymphoma. In this study, we investigated the efficacy of ibrutinib alone and in selective adjuvant combinations against BL in-vitro and in a human BL xenografted immune-deficient NOD.Cg-Prkdc^scidIl2rg^tm1Wjl/SzJ (NSG) mouse model. Our data demonstrated that phospho-BTK level was significantly reduced in BL cells treated with ibrutinib (p < 0.001). Moreover, we observed a significant decrease in cell proliferation as well as significant decrease in IC₅₀ of ibrutinib in combination with dexamethasone, rituximab, obinutuzumab, carfilzomib, and doxorubicin (p < 0.001). In-vivo studies demonstrated ibrutinib treated mice had a significantly prolonged survival with median survival of mice following ibrutinib treatment (32 days) (24 days) (p < 0.02). In conclusion, our findings demonstrate the significant in-vitro and preclinical in-vivo effects of ibrutinib in BL. Based on our preclinical results in this investigation, there is an on-going clinical trial comparing overall survival in children and adolescents with relapsed/refractory BL treated with chemoimmunotherapy with or without ibrutinib (NCT02703272).

Evaluation and treatment of Langerhans cell histiocytosis patients with central nervous system abnormalities: Current views and new vistas

Central nervous system (CNS) involvement in Langerhans cell histiocytosis (LCH) can include mass lesions of the hypothalamic pituitary axis, choroid plexus, cerebrum, and cerebellum or magnetic resonance imaging (MRI) signal abnormalities of the cerebellum, pons, and basal ganglia. The term neurodegenerative (ND) CNS-LCH has been given to the MRI signal abnormalities and neurologic dysfunction, although initially patients may have no clinical symptoms. Standardized evaluations to better understand the natural history and response to therapy are needed. We propose guidelines for clinical, radiologic, and physiologic tests as a framework for developing the best methods of evaluation, which can then be tested in prospective treatment protocols.

Role of the transcription factor Ikaros in development of autoimmune disease

The etiology of autoimmune disease is not fully understood, but disease development is believed to be due to a combination of genetic predispositions and environmental factors. Ikaros is a transcription factor that is an important regulator of hematopoiesis and critical for development of B cells. Recent genome wide association studies have found that several autoimmune diseases are associated with SNPs annotated to the Ikaros gene (IKZF1), as well as the closely related Ikaros family member Aiolos (IKZF3). Mouse models of autoimmunity are important research tools, and we recently reported the generation of two new Ikaros-mutant mice, with targeted deletions of the exons encoding the DNA-binding zinc finger 1 (ZnF1) or ZnF4 (Schjerven et al., 2013). These deletions did not abolish B-cell development, but rather illuminated differential roles of Ikaros at different stages of early B-cell development. Interestingly, we found that one of these mouse strains displayed very high levels of serum Anti-Nuclear Antibodies (ANA), indicative of autoimmune disease. Furthermore, we found by ex vivo studies that while wt spleen B cells require a “second signal” such as CD40L in addition to BCR stimulation (by anti-IgM), Ikaros-mutant B cells became activated and proliferated upon BCR stimulation alone without any externally added “second signal”. We hypothesize that Ikaros is important to limit autoimmunity and prevent auto reactive B cells by setting a requirement for the “second signal” in adaptive immune-recognition. Results will be presented from ongoing investigation using in vivo analysis of the autoimmune-related phenotype, and ex vivo analysis of Ikaros-dependent molecular mechanisms underlying the response to stimuli in B cells.

Abstract 2608: Ibrutinib significantly improves survival in a human Burkitt lymphoma (BL) xenograft NSG mouse model: Ibrutinib may be a potential adjuvant agent in the treatment of BL

BACKGROUND:

Burkitt lymphoma (BL) represents approximately 40% of all childhood and adolescent non-Hodgkin lymphoma (Miles/Cairo, BJH, 2012). Children with relapsed or progressive BL develop chemotherapy-resistant disease and can rarely be cured with salvage therapy (Cairo et al, JCO, 2012). Bruton's tyrosine kinase (BTK) is a regulator of normal B-cell development and is activated upon B-cell receptor (BCR) stimulation. Chronic active BCR signaling through BTK activation can be inhibited by the selective and covalent BTK inhibitor, ibrutinib (Young et al, Nat Rev, 2013). Ibrutinib has been highly effective in the treatment of refractory patients with CLL and MCL and has been approved by the FDA for patients with CLL or MCL who have received at least one prior therapy (USPI) (Byrd et al, NEJM, 2013 and Wang et al, NEJM, 2013). BL, however, is associated with tonic or possibly chronic active BCR signaling; while, both CLL and MCL have chronic active BCR signaling. We have previously demonstrated ibrutinib significantly decrease BL proliferation and viability in vitro (Lee/Cairo et al, ASH, 2014)

OBJECTIVE:

We hypothesize that ibrutinib may be a potential adjuvant agent in the treatment of BL. Therefore, we investigated the in vivo anti-tumor activity of ibrutinib in BL xenografted NOD/SCID (NSG) mice.

METHODS:

The luciferase expression plasmid (ffluc-Zeo), kindly provided by L. Cooper, MD) was transfected into Raji cells. Cells were subcutaneously injected into NSG mice (6-8wks old, NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ, Jackson lab). Tumor cells engraftment and progression were examined by Bioluminescent Imaging using the Xenogen IVIS-200 (Caliper Life Sciences). Mice were orally gavaged with vehicle control or Ibrutinib (1.25, 12.5 and 25mg/kg/day, generously provided by Janssen R&D, LLC) for 10 days. Statistical probability of survival and curve were determined by Kaplan Meier method.

RESULTS:

We observed a significant decrease in tumor luminescence intensity following ibrutinib treated BL xenografted NSG mice at day 20 (12.5mg/kg, p&lt;0.001 and 25mg/kg, p&lt;0.05) and at day 25 (12.5mg/kg, p&lt;0.05 and 25mg/kg, p&lt;0.05) compared to vehicle control. Furthermore, ibrutinib (12.5 mg/kg) treated mice significantly prolonged survival compared to vehicle control mice (p&lt;0.05). The median survival of mice following ibrutinib treatment (1.25, 12.5 and 25 mg/kg) were 31.5, 37.5 and 22.5 days, respectively, compared to control (24 days).

CONCLUSIONS:

Ibrutinib significantly decreased tumor progression and significantly increased the survival in BL xenografted NSG mice following 12.5mg/kg ibrutinib treatment. These results indicate that ibrutinib may be a potential adjuvant agent therapy in the treatment of BL. Future directions will be investigated the efficacy of ibrutinib in combination with dexamethasone in BL xenografted NSG mice.

Citation Format: Sanghoon Lee, Changhong Yin, Timmy O'Connell, Matthew Barth, Janet Ayello, Lauren Harrison, Carmella van de Ven, Rodney Miles, Paul Galardy, Stanton C. Goldman, Megan Lim, Michelle Hermiston, Linda McAllister-Lucas, Lisa G. Roth, Sherrie L. Perkins, Mitchell S. Cairo. Ibrutinib significantly improves survival in a human Burkitt lymphoma (BL) xenograft NSG mouse model: Ibrutinib may be a potential adjuvant agent in the treatment of BL. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2608. doi:10.1158/1538-7445.AM2015-2608

Differential responses to autoantibody deposition in CD45E613R BALB/c and C57Bl/6-129 F1 glomeruli is mediated by alterations in the autoantibody repertoire and inflammatory renal mononuclear cells (BA3P.110)

The mechanisms regulating the transition from autoreactivity to autoimmunity are poorly understood. CD45E613R mice express a point mutation in the juxtamembrane wedge that results in dysregulated phosphatase activity. Despite similar hyperactive ITAM-mediated signaling in multiple cell lineages, the phenotypic consequences of this mutation vary with genetic context. While both BALB/c and C57Bl/6-129 F1 CD45E613R mice develop similar high titer anti-nuclear antibodies (ANA) and immune complex deposition in the glomeruli, only F1 mice develop glomerulonephritis (GN). Here, we leverage these distinct phenotypes in the context of a common point mutation to define mechanisms leading to GN. BALB/c ANA are primarily anti-dsDNA while F1 ANA are anti-dsDNA, -H3 and -Sm/RNP. Consistent with this profile, F1 B cells have increased TLR7/9 signaling. Treatment of RAW264.7 cells with aged F1 but not BALB/c CD45E613R sera induces an inflammatory phenotype. Additionally, IL-10, IL-12, MCP-1 and RANTES are elevated in aged F1 CD45E613R mice. Analysis of young, autoantibody-free mice shows increased CD11b+ CD11c+ F4/80+ renal mononuclear cells surrounding F1 but not BALB/c CD45E613R glomeruli. Upon stimulation, only F1 CD45E613R renal mononuclear cells produce TNFα and IFNγ. Together, these data support a model in which an expanded antibody repertoire combined with altered kidney immune cell subsets and altered cytokines mediate the transition from autoreactivity to autoimmunity.

Preliminary analysis of the contributions of major histocompatibility complex-H2 to autoantibody production in a murine model of systemic lupus erythematosus. (BA3P.116)

The stochastic and heterogeneous nature of Systemic Lupus Erythematosus (SLE) supports a model whereby multiple genetic and/or environmental hits culminate in loss of tolerance and autoantibody production. Consistent with this model, the phenotype of CD45E613R mice that contain a single point mutation in the juxtamembrane wedge of CD45 depends on genetic context. Despite similar dysregulated phosphatase activity in all immune cells, CD45E613R mice on a C57Bl/6 (B6) background have no overt phenotype while BALB/c (BA) mice develop anti-double stranded (ds) DNA antibodies. An unbiased genome-wide screen for modifiers of autoantibody production between CD45E613R B6 and BA mice identified two candidate loci: Wedge Associated Modifier (Wam) 1 on Chromosome (Chr) 9 encompassing tlr9 and Wam2 on Chr 17 encompassing MHC H2. Previous work has shown that the hyporesponsive BA TLR9 allele permits anti-ds DNA antibodies while the B6 TLR9 allele is resistant. Here, we analyze the contribution of the MHC to this phenotype. CD45E613R BALB/c mice congenic for the B6 H2 locus develop anti-Sm antibodies while B6 mice congenic for the BALB/c H2 locus develop anti-Sm and anti-dsDNA antibodies. H2 congenic CD45E613R BALB/c mice have increased transitional B cells and a trend in increased B1 cells compared to congenic B6 mice. Thus, we hypothesize that MHC influences autoantibody specificity.

The structural wedge domain of the receptor-like tyrosine phosphatase CD45 enforces B cell tolerance by regulating substrate specificity

CD45 is a receptor-like tyrosine phosphatase that positively regulates BCR signaling by dephosphorylating the inhibitory tyrosine of the Src family kinases. We showed previously that a single point mutation, E613R, introduced into the cytoplasmic membrane-proximal "wedge" domain of CD45 is sufficient to drive a lupus-like autoimmune disease on a susceptible genetic background. To clarify the molecular mechanism of this disease, we took advantage of a unique allelic series of mice in which the expression of CD45 is varied across a broad range. Although both E613R B cells and those with supraphysiologic CD45 expression exhibited hyperresponsive BCR signaling, they did so by opposite regulation of the Src family kinase Lyn. We demonstrated that the E613R allele of CD45 does not function as a hyper- or hypomorphic allele but rather alters the substrate specificity of CD45 for Lyn. Despite similarly enhancing BCR signaling, only B cells with supraphysiologic CD45 expression became anergic, whereas only mice harboring the E613R mutation developed frank autoimmunity on a susceptible genetic background. We showed that selective impairment of a Lyn-dependent negative-regulatory circuit in E613R B cells drove autoimmunity in E613R mice. This demonstrates that relaxing negative regulation of BCR signaling, rather than enhancing positive regulation, is critical for driving autoimmunity in this system.

Cellular and molecular mechanisms for lupus nephritis in a mouse model of systemic lupus erythematosus (159.4)

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disorder with a range of presentations. Lupus nephritis is a particularly severe feature of SLE that predicts a poor outcome. Currently, it is unclear why some patients develop severe end organ disease while others have a relatively benign course. The CD45E613R mouse is a tractable model of SLE to study the transition from autoreactivity to autoimmunity. These mice express a single amino acid substitution (E613R) in the juxtamembrane wedge of CD45 that results in dysregulated phosphatase activity in all hematopoietic cells. Mirroring the variable presentation of human SLE, the phenotype of CD45E613R mice varies with genetic background. CD45E613R mice backcrossed to C57BL/6 (B6) or 129/Sv backgrounds fail to develop autoantibodies or end organ damage while F1 B6-129 CD45E613R mice develop high titer auto-antibodies and severe nephritis. Interestingly, BALB/c CD45E613R mice develop auto-antibodies but no nephritis. Using cytokine arrays and flow cytometry, we identified dysregulated cytokines and immune cell subsets in F1 B6-129 CD45E613R mice relative to the parental strains and wild-type controls. Classical inflammatory cytokines IL-1a and TNF-a were elevated in B6-129 F1 wedge mice. In contrast, MIP-1a and GM-CSF were most elevated in BALB/c wedge mice, implicating a protective effect. Uncovering new biomarkers and understanding disease pathogenesis should provide new insights into therapies for lupus nephritis.

Donor myocardial infarction impairs the therapeutic potential of bone marrow cells by an interleukin-1-mediated inflammatory response

Delivery of bone marrow cells (BMCs) to the heart has substantially improved cardiac function in most rodent models of myocardial infarction (MI), but clinical trials of BMC therapy have led to only modest improvements. Rodent models typically involve intramyocardial injection of BMCs from distinct donor individuals who are healthy. In contrast, autologous BMCs from individuals after MI are used for clinical trials. Using BMCs from donor mice after MI, we discovered that recent MI impaired BMC therapeutic efficacy. MI led to myocardial inflammation and an increased inflammatory state in the bone marrow, changing the BMC composition and reducing their efficacy. Injection of a general anti-inflammatory drug or a specific interleukin-1 inhibitor to donor mice after MI prevented this impairment. Our findings offer an explanation of why human trials have not matched the success of rodent experiments and suggest potential strategies to improve the success of clinical autologous BMC therapy.

An activating mutation in CD45 generates a novel murine model of hemophagocytic disorders in the context of a MHC Class 1 restricted TCR. (109.11)

Hemophagocytic syndromes encompass a spectrum of life-threatening disorders characterized by severe systemic inflammation and mechanistically are not well understood. We inadvertently generated a novel mouse model that shares many characteristics of these hyperinflammatory conditions. Expression of a single activating point mutation (E613R) in the receptor protein tyrosine phosphatase CD45 results in a lupus-like phenotype on a mixed C57Bl/6 (B6)-129/Sv genetic background. However, CD45E613R mice on an inbred B6 background show no stigmata of disease despite inappropriate regulation of signals emanating from CD45’s substrates, the src family kinases. Surprisingly, introduction of a MHC class I restricted T cell receptor specific for ovalbumin (OT1) into B6 CD45E613R mice results in a severe hyperinflammatory disease reminiscent of hemophagocytic syndromes. Disease is maintained in RAG1 deficient CD45E613R/OTI mice implicating myeloid and/or CD8 T cells in disease pathogenesis. Using an adoptive transfer approach, we find CD45E613R/OT1 CD8 T cells are necessary and sufficient for this phenotype. Further analysis of CD45E613R/OT1 T cells indicates that they are inappropriately activated, secrete excessive levels of interferon gamma, and have defective cytolytic function. These intriguing results support further analysis of the role of src family kinase mediated signaling networks in hemophagocytic disorders.

Impact of TLR9 on hyper-responsive ITAM signaling in a mouse model of SLE (47.24)

Anti-nuclear autoantibody (ANA) production by autoreactive B cells is a hallmark symptom of the autoimmune disease Systemic Lupus Erythematosus (SLE), which has a complex genetic etiology with environmental influences. In the CD45E613R knock-in mouse model of SLE, mice homozygous for an activating point mutation in CD45 develop high titer anti-dsDNA autoantibodies on the BALB/c (BA) and not the C57BL6/J (B6) or 129/Sv genetic backgrounds despite hyper-responsive ITAM signaling in several immune lineages in each genetic background. A screen for genetic modifiers of autoantibody production identified the candidate gene Tlr9. Sequence analysis of B6 and BA alleles of Tlr9 indicate several point mutations, resulting in five amino acid substitutions in TLR9. Splenic CD11b+ myeloid cells from BA express lower levels of TLR9 and BA-derived BMDCs are less responsive to synthetic TLR9 ligand CpG DNA. BA B cells are also less responsive to TLR9-mediated signaling than B6 B cells despite similar levels of TLR9 protein, indicating the BA TLR9 allele is hypo-responsive. Genetic ablation of TLR9 in CD45E613R mice on the non-autoreactive B6 genetic background augments disease, with mice developing splenomegaly and increased frequencies of memory T cells by 3 months of age. Some aged animals also developed ANAs, supporting the hypothesis that reduced TLR9 responsiveness permits increased autoreactivity in the context of hyper-responsive ITAM signaling.

PTPN22 deficiency cooperates with the CD45 E613R allele to break tolerance on a non-autoimmune background

Pep and CD45 are tyrosine phosphatases whose targets include the Src-family kinases, critical mediators of Ag receptor signaling. A polymorphism in PTPN22, the gene that encodes the human Pep orthologue Lyp, confers susceptibility to multiple human autoimmune diseases in the context of complex genetic backgrounds. However, the functional significance of the R620W risk allele is not clear. We report that misexpression of wild-type or R620W Pep/Lyp in Jurkat cells, in the context of its binding partner Csk, unmasks the risk allele as a hypomorph. It has been shown previously that although Pep-deficient mice on the B6 background have hyperresponsive memory T cells, autoimmunity does not develop. Mice containing a point mutation in the CD45 juxtamembrane wedge domain (E613R) develop a B cell-driven, lupus-like disease on the mixed 129/B6 background, but not on the B6 background. We studied the ability of Pep deficiency to act as a genetic modifier of the CD45 E613R mutation on the nonautoimmune B6 background to understand how complex susceptibility loci might interact in autoimmunity. In this study we report that double mutant mice develop a lupus-like disease as well as lymphadenopathy, polyclonal lymphocyte activation, and accelerated memory T cell formation. Following Ag receptor stimulation, peripheral B cells in the double mutant mice phenocopy hyperresponsive CD45 E613R B cells, whereas peripheral T cells respond like Pep(-/-) T cells. These studies suggest that Pep(-/-) T cells in the context of a susceptible microenvironment can drive hyperresponsive CD45 E613R B cells to break tolerance.

PTPN22 deficiency cooperates with the CD45 E613R wedge allele to break tolerance on a non-autoimmune background (49.18)

Pep and CD45 are tyrosine phosphatases whose targets include the Src-family kinases, critical mediators of antigen receptor signaling. A polymorphism in PTPN22, the gene that encodes the human Pep ortholog Lyp, confers susceptibility to multiple human autoimmune diseases. However, the significance of the R620W risk allele is not clear. We report that misexpression of wild type or R620W Lyp/Pep in Jurkat cells, in the context of their binding partner Csk, unmasks the risk allele as a hypomorph.

Although Pep deficient mice on the B6 background have hyper-responsive memory T cells, they fail to develop autoimmune disease. Mice containing a point mutation in CD45 (E613R) develop a B cell-driven lupus-like disease on the mixed 129/B6, but not on the B6 background. To model in mice how human susceptibility loci such as PTPN22 cooperate to provoke autoimmune disease, we studied the ability of Pep deficiency to act as a genetic modifier of the CD45 E613R mutation on the non-autoimmune B6 background.

Double mutant mice develop a lupus-like disease as well as a lymphoproliferative syndrome. Following antigen receptor stimulation, peripheral B cells in the double mutant mice phenocopy hyper-responsive CD45 E613R B cells, whereas peripheral T cells respond like Pep-/- T cells. These studies suggest that Pep-/- T cells in the context of a susceptible microenvironment can drive hyper-responsive CD45 E613R B cells to break tolerance.

Isolation of mutants defective in early steps of meiotic recombination in the yeast Saccharomyces cerevisiae

Using a selection based upon the ability of early Rec- mutations (e.g., rad50) to rescue the meiotic lethality of a rad52 spo13 strain, we have isolated 177 mutants. Analysis of 56 of these has generated alleles of the known Rec genes SPO11, ME14 and MER1, as well as defining five new genes: REC102, REC104, REC107, REC113 and REC114. Mutations in all of the new genes appear to specifically affect meiosis; they do not have any detectable mitotic phenotype. Mutations in REC102, REC104 and REC107 reduce meiotic recombination several hundred fold. No alleles of RED1 or HOP1 were isolated, consistent with the proposal that these genes may be primarily involved with chromosome pairing and not exchange.