A validated pediatric disease risk index for allogeneic hematopoietic cell transplantation

A disease risk index (DRI) that was developed for adults with hematologic malignancy who were undergoing hematopoietic cell transplantation is also being used to stratify children and adolescents by disease risk. Therefore, to develop and validate a DRI that can be used to stratify those with AML and ALL by their disease risk, we analyzed 2569 patients aged <18 years with acute myeloid (AML; n = 1224) or lymphoblastic (ALL; n = 1345) leukemia who underwent hematopoietic cell transplantation. Training and validation subsets for each disease were generated randomly with 1:1 assignment to the subsets, and separate prognostic models were derived for each disease. For AML, 4 risk groups were identified based on age, cytogenetic risk, and disease status, including minimal residual disease status at transplantation. The 5-year leukemia-free survival for low (0 points), intermediate (2, 3, 5), high (7, 8), and very high (>8) risk groups was 78%, 53%, 40%, and 25%, respectively (P < .0001). For ALL, 3 risk groups were identified based on age and disease status, including minimal residual disease status at transplantation. The 5-year leukemia-free survival for low (0 points), intermediate (2-4), and high (≥5) risk groups was 68%, 51%, and 33%, respectively (P < .0001). We confirmed that the risk groups could be applied to overall survival, with 5-year survival ranging from 80% to 33% and 73% to 42% for AML and ALL, respectively (P < .0001). This validated pediatric DRI, which includes age and residual disease status, can be used to facilitate prognostication and stratification of children with AML and ALL for allogeneic transplantation.

Targeting Tumor-Associated Macrophages in the Pediatric Sarcoma Tumor Microenvironment

For many pediatric sarcoma patients, multi-modal therapy including chemotherapy, radiation, and surgery is sufficient to cure their disease. However, event-free and overall survival rates for patients with more advanced disease are grim, necessitating the development of novel therapeutic approaches. Within many pediatric sarcomas, the normal immune response, including recognition and destruction of cancer cells, is lost due to the highly immune suppressive tumor microenvironment (TME). In this setting, tumor cells evade immune detection and capitalize on the immune suppressed microenvironment, leading to unchecked proliferation and metastasis. Recent preclinical and clinical approaches are aimed at understanding this immune suppressive microenvironment and employing cancer immunotherapy in an attempt to overcome this, by renewing the ability of the immune system to recognize and destroy cancer cells. While there are several factors that drive the attenuation of immune responses in the sarcoma TME, one of the most remarkable are tumor associated macrophage (TAMs). TAMs suppress immune cytolytic function, promote tumor growth and metastases, and are generally associated with a poor prognosis in most pediatric sarcoma subtypes. In this review, we summarize the mechanisms underlying TAM-facilitated immune evasion and tumorigenesis and discuss the potential therapeutic application of TAM-focused drugs in the treatment of pediatric sarcomas.

Human innate lymphoid cell precursors express CD48 that modulates ILC differentiation through 2B4 signaling

Innate lymphoid cells (ILCs) develop from common lymphoid progenitors (CLPs), which further differentiate into the common ILC progenitor (CILP) that can give rise to both ILCs and natural killer (NK) cells. Murine ILC intermediates have recently been characterized, but the human counterparts and their developmental trajectories have not yet been identified, largely due to the lack of homologous surface receptors in both organisms. Here, we show that human CILPs (CD34⁺CD117⁺α4β7⁺Lin^-) acquire CD48 and CD52, which define NK progenitors (NKPs) and ILC precursors (ILCPs). Two distinct NK cell subsets were generated in vitro from CD34⁺CD117⁺α4β7⁺Lin^-CD48^-CD52⁺ and CD34⁺CD117⁺α4β7⁺Lin^-CD48⁺CD52⁺ NKPs, respectively. Independent of NKPs, ILCPs exist in the CD34⁺CD117⁺α4β7⁺Lin^-CD48⁺CD52⁺ subset and give rise to ILC1s, ILC2s, and NCR⁺ ILC3s, whereas CD34⁺CD117⁺α4β7⁺Lin^-CD48⁺CD52^- ILCPs give rise to a distinct subset of ILC3s that have lymphoid tissue inducer (LTi)-like properties. In addition, CD48-expressing CD34⁺CD117⁺α4β7⁺Lin^- precursors give rise to tissue-associated ILCs in vivo. We also observed that the interaction of 2B4 with CD48 induced differentiation of ILC2s, and together, these findings show that expression of CD48 by human ILCPs modulates ILC differentiation.

Glycemic variability is associated with poor outcomes in pediatric hematopoietic stem cell transplant patients

BACKGROUND

Among pediatric hematopoietic stem cell transplant (HSCT) recipients, abnormal glycemic control is shown to be associated with increased risk of transplant-related mortality, death from any cause, risk of infection, increased hospitalized, and intensive care days. Independent effects of higher glycemic variability, a component of glycemic control, have not been described. This study aimed to characterize risk factors for, and consequences of, higher glycemic variability in HSCT patients.

PROCEDURE

Medical records for a cohort of 344 patients, age 0-30 years, who underwent first HSCT from 2007 to 2016 at Children's Hospital Colorado were retrospectively reviewed. Glucose coefficients of variation (CV) were analyzed for HSCT days -14 to 0 and 0-30, and patients were assessed for potential risk factors and outcomes.

RESULTS

Roughly one-third of patients had pre-HSCT and day 0-30 glucose CV above the reported healthy adult range. Independent of HSCT type, doubling of pre-HSCT glucose CV was associated with a 4.91-fold (95% confidence interval [CI], 1.40-17.24) increased hazard of infection, as well as increased risk for intensive care hospitalization for allogenic HSCT patients. Multivariable analysis demonstrated that allogeneic HSCT patients had a 1.40- and 1.38-fold (95% CI, 0.98-1.99 and 1.00-1.91) increased hazard of death for every doubling of pre-HSCT and day 0-30 glucose CV, respectively.

CONCLUSIONS

Just as with higher mean glucose, higher glycemic variability in the pediatric HSCT population is independently associated with significantly increased morbidity. Additional research is required to evaluate the utility of glucose control to mitigate these relationships and improve HSCT outcomes.

Therapeutic effect of TRC105 and decitabine combination in AML xenografts

Acute myeloid leukemia (AML) is an aggressive hematologic malignancy, often characterized by poor prognosis following standard induction therapy. The hypomethylating agent decitabine (DAC) is an alternative treatment for elderly and relapsed/refractory AML patients, yet responses following DAC monotherapy are still modest. The transforming growth factor-β (TGF-β) receptor CD105 (endoglin) is expressed in various hematopoietic malignancies, and high CD105 expression correlates with poor prognosis in AML patients. Using a xenograft model, we have recently demonstrated that targeting CD105⁺ AML blasts with the TRC105 monoclonal antibody inhibits leukemia progression. Here we investigated whether administration of TRC105 along with DAC could represent a novel therapeutic option for relapsed/refractory AML. Our data show that the DAC/TRC105 combination results in a more durable anti-leukemic effect in AML xenografts compared to DAC monotherapy. Moreover, the DAC/TRC105 combination enhanced reactive oxygen species (ROS) activity, which correlated with reduced leukemia burden. RNA-sequencing studies suggest that TRC105 may alter TGF-β activity in AML blasts. Taken together, these findings provide rationale for the clinical evaluation of TRC105 in combination with DAC in AML patients.

Autoimmune cytopenias following allogeneic hematopoietic stem cell transplant in pediatric patients: Response to therapy and late effects

BACKGROUND

Autoimmune cytopenias (AICs) are rare, but serious complications of allogeneic hematopoietic cell transplantation (allo-HSCT).

PROCEDURE

We performed a case-control study using 20 pediatric AIC cases and 40 controls, matched by stem cell source and primary indication comparing clinical and transplant characteristics, treatment, outcomes, and late effects.

RESULTS

Cases were more likely to be human leukocyte antigen mismatched (P = 0.04). There was no difference in conditioning regimen, serotherapy use, graft-versus-host disease (GVHD) prophylaxis, incidence of acute or chronic GVHD, ABO compatibility, infections, and donor engraftment. The median time to AIC onset was 219 days (range, 97-1205 days) and AIC resolution was 365 days (range, 10 days to 2737.5 days). First-line therapies for AIC patients most commonly included corticosteroids (75%) and rituximab (55%). Only 25% of patients responded to first-line treatment. At a median of 611.5 days from last rituximab dose, 82.5% patients were still receiving intravenous immune globulin for hypogammaglobulinemia compared with 2.5% of controls (P < 0.0001). Iron overload was higher in AIC patients (P = 0.0004), as was avascular necrosis (P = 0.04). There was no difference in overall survival at one year after HSCT (85% vs 82.5%). Two patients with refractory autoimmune hemolytic anemia responded to daratumumab and had resolution of B-cell aplasia.

CONCLUSIONS

In this study, we find poor initial responses to AIC-directed therapies and significant late effects.

Prolactin Acts on Myeloid Progenitors to Modulate SMAD7 Expression and Enhance Hematopoietic Stem Cell Differentiation into the NK Cell Lineage

Numerous cell types modulate hematopoiesis through soluble and membrane bound molecules. Whether developing hematopoietic progenitors of a particular lineage modulate the differentiation of other hematopoietic lineages is largely unknown. Here we aimed to investigate the influence of myeloid progenitors on CD34+ cell differentiation into CD56+ innate lymphocytes. Sorted CD34+ cells cultured in the presence of stem cell factor (SCF) and FMS-like tyrosine kinase 3 ligand (FLT3L) give rise to numerous cell types, including progenitors that expressed the prolactin receptor (PRLR). These CD34+PRLR+ myeloid-lineage progenitors were derived from granulocyte monocyte precursors (GMPs) and could develop into granulocytes in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro. Moreover, CD34+PRLR+ myeloid progenitors lacked lymphoid developmental potential, but when stimulated with prolactin (PRL) they increased the differentiation of other CD34+ cell populations into the NK lineage in a non-contact dependent manner. Both mRNA and protein analyses show that PRL increased mothers against decapentaplegic homolog 7 (SMAD7) in CD34+PRLR+ myeloid cells, which reduced the production of transforming growth factor beta 1 (TGF-β1), a cytokine known to inhibit CD56+ cell development. Thus, we uncover an axis whereby CD34+PRLR+ GMPs inhibit CD56+ lineage development through TGF-β1 production and PRL stimulation leads to SMAD7 activation, repression of TGF-β1, resulting in CD56+ cell development.

Mesenchymal stromal cells shape the MDS microenvironment by inducing suppressive monocytes that dampen NK cell function

Altered BM hematopoiesis and immune suppression are hallmarks of myelodysplastic syndrome (MDS). While the BM microenvironment influences malignant hematopoiesis, the mechanism leading to MDS-associated immune suppression is unknown. We tested whether mesenchymal stromal cells (MSCs) contribute to this process. Here, we developed a model to study cultured MSCs from patients with MDS (MDS-MSCs) compared with those from aged-matched normal controls for regulation of immune function. MDS-MSCs and healthy donor MSCs (HD-MSCs) exhibited a similar in vitro phenotype, and neither had a direct effect on NK cell function. However, when MDS- and HD-MSCs were cultured with monocytes, only the MDS-MSCs acquired phenotypic and metabolic properties of myeloid-derived suppressor cells (MDSCs), with resulting suppression of NK cell function, along with T cell proliferation. A MSC transcriptome was observed in MDS-MSCs compared with HD-MSCs, including increased expression of the ROS regulator, ENC1. High ENC1 expression in MDS-MSCs induced suppressive monocytes with increased INHBA, a gene that encodes for a member of the TGF-β superfamily of proteins. These monocytes also had reduced expression of the TGF-β transcriptional repressor MAB21L2, further adding to their immune-suppressive function. Silencing ENC1 or inhibiting ROS production in MDS-MSCs abrogated the suppressive function of MDS-MSC-conditioned monocytes. In addition, silencing MAB21L2 in healthy MSC-conditioned monocytes mimicked the MDS-MSC-suppressive transformation of monocytes. Our data demonstrate that MDS-MSCs are responsible for inducing an immune-suppressive microenvironment in MDS through an indirect mechanism involving monocytes.

Donor HLA-E Status Associates with Disease-Free Survival and Transplant-Related Mortality after Non In Vivo T Cell-Depleted HSCT for Acute Leukemia

Previous studies have suggested that HLA-E may have a significant role in the outcome of matched unrelated hematopoietic stem cell transplantation (HSCT), especially for patients with acute leukemia. We used Center for International Blood and Marrow Transplant Research data and samples of 1840 adult patients with acute leukemia and their 10/10 HLA-matched unrelated donors to investigate the impact of HLA-E matching status as well as of donor/recipient (D/R) HLA-E genotype on post-HSCT outcome. Both patients and donors were HLA-E genotyped by next-generation sequencing. All patients received their first transplant in complete remission between 2000 and 2015. Median follow-up time was 90 months. Overall survival, disease-free survival (DFS), transplant-related mortality (TRM), and relapse incidence were primary endpoints with statistical significance set at .01. D/R HLA-E genotype analysis revealed a significant association of donor HLA-E*01:03/01:03 genotype with DFS (hazard ratio [HR] = 1.35, P = .0006) and TRM (HR = 1.41, P = .0058) in patients who received T cell replete (ie, without in vivo T cell depletion) transplants (n = 1297). As for D/R HLA-E matching, we did not identify any significant effect on any of the clinical outcome endpoints. In conclusion, this is the largest study to date reporting an improvement of DFS and TRM after matched unrelated HSCT by avoidance of HLA-E*01:03 homozygous donors in patients transplanted with T cell replete grafts for acute leukemia.

Single-Cell Gene Expression Analyses Reveal Distinct Self-Renewing and Proliferating Subsets in the Leukemia Stem Cell Compartment in Acute Myeloid Leukemia

Standard chemotherapy for acute myeloid leukemia (AML) targets proliferative cells and efficiently induces complete remission; however, many patients relapse and die of their disease. Relapse is caused by leukemia stem cells (LSC), the cells with self-renewal capacity. Self-renewal and proliferation are separate functions in normal hematopoietic stem cells (HSC) in steady-state conditions. If these functions are also separate functions in LSCs, then antiproliferative therapies may fail to target self-renewal, allowing for relapse. We investigated whether proliferation and self-renewal are separate functions in LSCs as they often are in HSCs. Distinct transcriptional profiles within LSCs of Mll-AF9/NRAS^G12V murine AML were identified using single-cell RNA sequencing. Single-cell qPCR revealed that these genes were also differentially expressed in primary human LSCs and normal human HSPCs. A smaller subset of these genes was upregulated in LSCs relative to HSPCs; this subset of genes constitutes "LSC-specific" genes in human AML. To assess the differences between these profiles, we identified cell surface markers, CD69 and CD36, whose genes were differentially expressed between these profiles. In vivo mouse reconstitution assays resealed that only CD69^High LSCs were capable of self-renewal and were poorly proliferative. In contrast, CD36^High LSCs were unable to transplant leukemia but were highly proliferative. These data demonstrate that the transcriptional foundations of self-renewal and proliferation are distinct in LSCs as they often are in normal stem cells and suggest that therapeutic strategies that target self-renewal, in addition to proliferation, are critical to prevent relapse and improve survival in AML. SIGNIFICANCE: These findings define and functionally validate a self-renewal gene profile of leukemia stem cells at the single-cell level and demonstrate that self-renewal and proliferation are distinct in AML. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/3/458/F1.large.jpg.

Molecular Correlates of Socioeconomic Status and Clinical Outcomes Following Hematopoietic Cell Transplantation for Leukemia

Background

Clinical outcomes among allogeneic hematopoietic cell transplant (HCT) recipients are negatively affected by low socioeconomic status (SES), yet the biological mechanisms accounting for this health disparity remain to be elucidated. Among unrelated donor HCT recipients with acute myelogenous leukemia, one recent pilot study linked low SES to increased expression of a stress-related gene expression profile known as the conserved transcriptional response to adversity (CTRA) in peripheral blood mononuclear cells, which involves up-regulation of pro-inflammatory genes and down-regulation of genes involved in type I interferon response and antibody synthesis.

Methods

This study examined these relationships using additional measures in a larger archival sample of 261 adults who received an unrelated donor HCT for acute myelogenous leukemia to 1) identify cellular and molecular mechanisms involved in SES-related differences in pre-transplant leukocyte transcriptome profiles, and 2) evaluate pre-transplant CTRA biology associations with clinical outcomes through multivariable analysis controlling for demographic-, disease-, and transplant-related covariates.

Results

Low SES individuals showed increases in classic monocyte activation and pro-inflammatory transcription control pathways as well as decreases in activation of nonclassic monocytes, all consistent with the CTRA biological pattern. Transplant recipients in the highest or lowest quartiles of the CTRA pro-inflammatory gene component had a more than 2-fold elevated hazard of relapse (hazard ratio [HR] = 2.47, 95% confidence interval [CI] = 1.44 to 4.24), P = .001; HR = 2.52, 95% CI = 1.46 to 4.34, P = .001) and more than 20% reduction in leukemia-free survival (HR = 1.57, 95% CI = 1.08 to 2.28, P = .012; HR = 1.49, 95% CI = 1.04 to 2.15, P = .03) compared with the middle quartiles.

Conclusions

These findings identify SES- and CTRA-associated myeloid- and inflammation-related transcriptome signatures in recipient pre-transplant blood samples as a potential novel predictive biomarker of HCT-related clinical outcomes.

The Human TET2 Gene Contains Three Distinct Promoter Regions With Differing Tissue and Developmental Specificities

Tet methylcytosine dioxygenase 2 (TET2) is a tumor suppressor gene that is inactivated in a wide range of hematological cancers. TET2 enzymatic activity converts 5-methylcytosine (5-mC) into 5-hydroxymethylcytosine (5-hmC), an essential step in DNA demethylation. Human TET2 is highly expressed in pluripotent cells and down-regulated in differentiated cells: however, transcriptional regulation of the human TET2 gene has not been investigated in detail. Here we define three promoters within a 2.5 kb region located ∼ 87 kb upstream of the first TET2 coding exon. The three promoters, designated as Pro1, Pro2, and Pro3, generate three alternative first exons, and their presence in TET2 mRNAs varies with cell type and developmental stage. In general, all three TET2 transcripts are more highly expressed in human tissues rich in hematopoietic stem cells, such as spleen and bone marrow, compared to other tissues, such as brain and kidney. Transcripts from Pro2 are expressed by a broad range of tissues and at a significantly higher level than Pro1 or Pro3 transcripts. Pro3 transcripts were highly expressed by embryoid bodies generated from the H9 ES cell line, and the major Pro3 transcript is an alternatively spliced mRNA isoform that produces a truncated TET2 protein lacking the catalytic domain. Our study demonstrates distinct tissue-specific mechanisms of TET2 transcriptional regulation during early pluripotent states and in differentiated cell types.

A novel human IL2RB mutation results in T and NK cell-driven immune dysregulation

A novel homozygous mutation in human IL2RB results in decreased IL-2Rβ protein expression and dysregulated IL-2/15 signaling. This hypomorphic mutation leads to decreased regulatory T cell frequency and an abnormal NK cell compartment, with clinical manifestations of autoimmunity and susceptibility to CMV.

The pleiotropic actions of interleukin-2 (IL-2) are essential for regulation of immune responses and maintenance of immune tolerance. The IL-2 receptor (IL-2R) is composed of IL-2Rα, IL-2Rβ, and IL-2Rγ subunits, with defects in IL-2Rα and IL-2Rγ and their downstream signaling effectors resulting in known primary immunodeficiency disorders. Here, we report the first human defect in IL-2Rβ, occurring in two infant siblings with a homozygous IL2RB mutation in the WSXWS motif, manifesting as multisystem autoimmunity and susceptibility to CMV infection. The hypomorphic mutation results in diminished IL-2Rβ surface expression and dysregulated IL-2/15 signaling, with an anticipated reduction in regulatory T cells. However, in contrast to the IL-2Rβ^−/− animal model, which lacks NK cells, these siblings demonstrate an expansion of NK cells, particularly the CD56^bright subset, and a lack of terminally differentiated NK cells. Thus, the early-onset autoimmunity and immunodeficiency are linked to functional deficits arising from altered IL-2Rβ expression and signaling in T and NK cells.

Mixed vs full donor engraftment early after hematopoietic cell transplant: Impact on incidence and control of cytomegalovirus infection

Recovery of cytomegalovirus (CMV)-specific immunity after hematopoietic cell transplantation (HCT) is essential in controlling CMV infection. We hypothesize that mixed donor engraftment as measured by chimerism at day 30 in CMV D(+) HCTs and full chimerism in CMV D(-) HCTs will be predictive of CMV reactivation. Prospectively collected data for 407 CMV R+ HCT recipients transplanted from 2006 to 2014 at the University of Minnesota were retrospectively analyzed. Full and mixed donor engraftment were defined as ≥95% or <95% donor cells at day 30, respectively. Source of engraftment determination included preferentially peripheral blood CD3 fraction, then myeloid cell fraction (CD15+), then bone marrow. In 407 CMV R+ subjects, 77% (n = 313) were CMV D(-) cells from umbilical cord blood (n = 209), peripheral blood (n = 58) or marrow (n = 46). Fifty three per cent received reduced intensity conditioning (RIC). At day +30, full donor engraftment was seen in 82% of myeloablative and 55% of RIC transplants. The cumulative incidence of CMV infection 1-year after transplant was not different in patients with full (54%, n = 276) or mixed (53%, n = 131) donor engraftment. Control of CMV did not significantly differ among the two groups. In multiple regression analysis, there was no significant association between donor engraftment (mixed or full) and incidence or control of CMV.

Transient Expression of GATA3 in Hematopoietic Stem Cells Facilitates Helper Innate Lymphoid Cell Differentiation

Helper Innate lymphoid cells (ILCs) are tissue resident lymphocytes that play a critical role in a number of biological processes. Several transcription factors are required for the differentiation of hematopoietic stem cells (HSCs) into ILCs. Recent studies demonstrate GATA3 as a transcriptional regulator that plays an essential role in ILC development. We aimed to modulate the differentiation of human cord blood-derived CD34⁺ cells into ILCs by transient and ectopic expression of mRNA encoding transcription factors known to be important for ILC lineage differentiation, including GATA3, TOX, NFIL3, ID2, and RORγt. Using this experimental protocol, only GATA3 significantly modulated HSCs to differentiate into helper ILCs. Transient overexpression of GATA3 drove the emergence of CD34⁺α4β7⁺ early ILC progenitors during the first few days of culture. These ILC progenitors further acquired IL-7Rα and CD117 to give rise to immediate ILC precursors. In support of these findings, analysis of the genes induced by GATA3 in HSCs showed an upregulation of those associated with ILC development. Moreover, we show GATA3 also acts on more committed progenitors and significantly shifts the differentiation of progenitors away from the ILC1/NK lineage to the ILC2 and ILC3 lineage. In summary, transient overexpression of GATA3 mRNA in CD34⁺ HSCs enhances the differentiation of HSCs into the helper ILC lineages, at the expense of NK cell development.

Safety and feasibility of outpatient autologous stem cell transplantation in pediatric patients with primary central nervous system tumors

High-dose chemotherapy with autologous hematopoietic stem cell transplantation (autoHSCT) is a well-established treatment for pediatric central nervous system (CNS) tumors. Given the risks of toxicity and infection, pediatric autoHSCT has been historically performed on hospitalized children. As our practice evolved, some patients were transplanted as outpatients. We performed a retrospective cohort analysis of 37 patients who received 90 transplant procedures (49 outpatient and 41 inpatient) at Children’s Hospital Colorado. The most common primary diagnosis was medulloblastoma (51.4%). Of the patients transplanted as outpatients, 69.4% were admitted for fever and neutropenia and had a median time to hospitalization of day +6, with fever and neutropenia being the most common reasons for admission. The median time to neutrophil engraftment was the same in both cohorts, 11 days. Median time to platelet engraftment was 13 days (8–82 days) vs 16 days (8–106 days) (p = 0.0008). At day +100, the transplant-related mortality (TRM) was 0% for both the cohorts. At a median follow-up of 1.7 years, overall survival (OS) for all patients was 66.1% and TRM was 0% for both the cohorts. Outpatient autoHSCT for properly selected children with CNS tumors is safe and effective.