Genomic signature of Fanconi anaemia DNA repair pathway deficiency in cancer.

Fanconi anaemia (FA), a model syndrome of genome instability, is caused by a deficiency in DNA interstrand crosslink repair resulting in chromosome breakage1-3. The FA repair pathway protects against endogenous and exogenous carcinogenic aldehydes4-7. Individuals with FA are hundreds to thousands fold more likely to develop head and neck (HNSCC), oesophageal and anogenital squamous cell carcinomas8 (SCCs). Molecular studies of SCCs from individuals with FA (FA SCCs) are limited, and it is unclear how FA SCCs relate to sporadic HNSCCs primarily driven by tobacco and alcohol exposure or infection with human papillomavirus9 (HPV). Here, by sequencing genomes and exomes of FA SCCs, we demonstrate that the primary genomic signature of FA repair deficiency is the presence of high numbers of structural variants. Structural variants are enriched for small deletions, unbalanced translocations and fold-back inversions, and are often connected, thereby forming complex rearrangements. They arise in the context of TP53 loss, but not in the context of HPV infection, and lead to somatic copy-number alterations of HNSCC driver genes. We further show that FA pathway deficiency may lead to epithelial-to-mesenchymal transition and enhanced keratinocyte-intrinsic inflammatory signalling, which would contribute to the aggressive nature of FA SCCs. We propose that the genomic instability in sporadic HPV-negative HNSCC may arise as a result of the FA repair pathway being overwhelmed by DNA interstrand crosslink damage caused by alcohol and tobacco-derived aldehydes, making FA SCC a powerful model to study tumorigenesis resulting from DNA-crosslinking damage.

Alloengraftment without significant toxicity or GVHD in CD45 antibody-drug conjugate-conditioned Fanconi anemia mice.

ABSTRACT: Fanconi anemia (FA) is an inherited DNA repair disorder characterized by bone marrow (BM) failure, developmental abnormalities, myelodysplasia, leukemia, and solid tumor predisposition. Allogeneic hematopoietic stem cell transplantation (allo-HSCT), a mainstay treatment, is limited by conditioning regimen-related toxicity and graft-versus-host disease (GVHD). Antibody-drug conjugates (ADCs) targeting hematopoietic stem cells (HSCs) can open marrow niches permitting donor stem cell alloengraftment. Here, we report that single dose anti-mouse CD45-targeted ADC (CD45-ADC) facilitated stable, multilineage chimerism in 3 distinct FA mouse models representing 90% of FA complementation groups. CD45-ADC profoundly depleted host stem cell enriched Lineage-Sca1+cKit+ cells within 48 hours. Fanca-/- recipients of minor-mismatched BM and single dose CD45-ADC had peripheral blood (PB) mean donor chimerism >90%; donor HSCs alloengraftment was verified in secondary recipients. In Fancc-/- and Fancg-/- recipients of fully allogeneic grafts, PB mean donor chimerism was 60% to 80% and 70% to 80%, respectively. The mean percent donor chimerism in BM and spleen mirrored PB results. CD45-ADC-conditioned mice did not have clinical toxicity. A transient <2.5-fold increase in hepatocellular enzymes and mild-to-moderate histopathological changes were seen. Under GVHD allo-HSCT conditions, wild-type and Fanca-/- recipients of CD45-ADC had markedly reduced GVHD lethality compared with lethal irradiation. Moreover, single dose anti-human CD45-ADC given to rhesus macaque nonhuman primates on days -6 or -10 was at least as myeloablative as lethal irradiation. These data suggest that CD45-ADC can potently promote donor alloengraftment and hematopoiesis without significant toxicity or severe GVHD, as seen with lethal irradiation, providing strong support for clinical trial considerations in highly vulnerable patients with FA.

Prevention of acute GVHD using an orthogonal IL-2/IL-2Rß system to selectively expand regulatory T cells in vivo.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative option for patients with hematological disorders and bone marrow (BM) failure syndromes. Graft-versus-host disease (GVHD) remains a leading cause of morbidity posttransplant. Regulatory T cell (Treg) therapies are efficacious in ameliorating GVHD but limited by variable suppressive capacities and the need for a high therapeutic dose. Here, we sought to expand Treg in vivo by expressing an orthogonal interleukin 2 receptor ß (oIL-2Rß) that would selectively interact with oIL-2 cytokine and not wild-type (WT) IL-2. To test whether the orthogonal system would preferentially drive donor Treg expansion, we used a murine major histocompatibility complex-disparate GVHD model of lethally irradiated BALB/c mice given T cell-depleted BM from C57BL/6 (B6) mice alone or together with B6Foxp3+GFP+ Treg or oIL-2Rß-transduced Treg at low cell numbers that typically do not control GVHD with WT Treg. On day 2, B6 activated T cells (Tcons) were injected to induce GVHD. Recipients were treated with phosphate-buffered saline (PBS) or oIL-2 daily for 14 days, then 3 times weekly for an additional 14 days. Mice treated with oIL-2Rß Treg and oIL-2 compared with those treated with PBS had enhanced GVHD survival, in vivo selective expansion of Tregs, and greater suppression of Tcon expansion in secondary lymphoid organs and intestines. Importantly, oIL-2Rß Treg maintained graft-versus-tumor (GVT) responses in 2 distinct tumor models (A20 and MLL-AF9). These data demonstrate a novel approach to enhance the efficacy of Treg therapy in allo-HSCT using an oIL-2/oIL-2Rß system that allows for selective in vivo expansion of Treg leading to GVHD protection and GVT maintenance.

Substrate Specificities of Variants of Barley (1,3)- and (1,3;1,4)-ß-d-Glucanases Resulting from Mutagenesis and Segment Hybridization.

Barley (1,3;1,4)-ß-d-glucanase is believed to have evolved from an ancestral monocotyledon (1,3)-ß-d-glucanase, enabling the hydrolysis of (1,3;1,4)-ß-d-glucans in the cell walls of leaves and germinating grains. In the present study, we investigated the substrate specificities of variants of the barley enzymes (1,3;1,4)-ß-d-glucan endohydrolase [(1,3;1,4)-ß-d-glucanase] isoenzyme EII (HvEII) and (1,3)-ß-d-glucan endohydrolase [(1,3)-ß-d-glucanase] isoenzyme GII (HvGII) obtained by protein segment hybridization and site-directed mutagenesis. Using protein segment hybridization, we obtained three variants of HvEII in which the substrate specificity was that of a (1,3)-ß-d-glucanase and one variant that hydrolyzed both (1,3)-ß-d-glucans and (1,3;1,4)-ß-d-glucans; the wild-type enzyme hydrolyzed only (1,3;1,4)-ß-d-glucans. Using substitutions of specific amino acid residues, we obtained one variant of HvEII that hydrolyzed both substrates. However, neither protein segment hybridization nor substitutions of specific amino acid residues gave variants of HvGII that could hydrolyze (1,3;1,4)-ß-d-glucans; the wild-type enzyme hydrolyzed only (1,3)-ß-d-glucans. Other HvEII and HvGII variants showed changes in specific activity and their ability to degrade the (1,3;1,4)-ß-d-glucans or (1,3)-ß-d-glucans to larger oligosaccharides. We also used molecular dynamics simulations to identify amino-acid residues or structural regions of wild-type HvEII and HvGII that interact with (1,3;1,4)-ß-d-glucans and (1,3)-ß-d-glucans, respectively, and may be responsible for the substrate specificities of the two enzymes.

A CD45-targeted antibody-drug conjugate successfully conditions for allogeneic hematopoietic stem cell transplantation in mice.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially curative treatment of patients with nonmalignant or malignant blood disorders. Its success has been limited by graft-versus-host disease (GVHD). Current systemic nontargeted conditioning regimens mediate tissue injury and potentially incite and amplify GVHD, limiting the use of this potentially curative treatment beyond malignant disorders. Minimizing systemic nontargeted conditioning while achieving alloengraftment without global immune suppression is highly desirable. Antibody-drug-conjugates (ADCs) targeting hematopoietic cells can specifically deplete host stem and immune cells and enable alloengraftment. We report an anti-mouse CD45-targeted-ADC (CD45-ADC) that facilitates stable murine multilineage donor cell engraftment. Conditioning with CD45-ADC (3 mg/kg) was effective as a single agent in both congenic and minor-mismatch transplant models resulting in full donor chimerism comparable to lethal total body irradiation (TBI). In an MHC-disparate allo-HSCT model, pretransplant CD45-ADC (3 mg/kg) combined with low-dose TBI (150 cGy) and a short course of costimulatory blockade with anti-CD40 ligand antibody enabled 89% of recipients to achieve stable alloengraftment (mean value: 72%). When CD45-ADC was combined with pretransplant TBI (50 cGy) and posttransplant rapamycin, cyclophosphamide (Cytoxan), or a JAK inhibitor, 90% to 100% of recipients achieved stable chimerism (mean: 77%, 59%, 78%, respectively). At a higher dose (5 mg/kg), CD45-ADC as a single agent was sufficient for rapid, high-level multilineage chimerism sustained through the 22 weeks observation period. Therefore, CD45-ADC has the potential utility to confer the benefit of fully myeloablative conditioning but with substantially reduced toxicity when given as a single agent or at lower doses in conjunction with reduced-intensity conditioning.

Development of specific growth charts for children with Fanconi anemia.

Patients with Fanconi anemia (FA) are often perceived to have poor growth when general population growth curves are utilized. We hypothesize that FA patients have unique growth and aimed to create FA-specific growth charts. Height and weight data from ages 0 to 20 years were extracted from medical records of patients treated at the Fanconi Anemia Comprehensive Care Clinic at the University of Minnesota. Height, weight, and BMI growth curves were generated and fitted to reference percentiles using the Lambda-Mu-Sigma method. FA-specific percentiles were compared to WHO standards for ages 0-2 and CDC references for ages 2-20. In FA males, the 50th height- and weight-for-age percentiles overlap with the 3rd reference percentile. In FA females, only the 50th height-for-age percentile overlaps with the 3rd reference percentile. For weight, FA females show progressive growth failure between 6 and 24 months followed by stabilization around the 50th percentile. The FA BMI-for-age percentiles show similar patterns to the weight-for-age percentiles but have different timing of onset of adiposity rebound and broader variability in females. Growth in FA patients follows a different trajectory than available normative curves. FA-specific growth charts may be useful to better guide accurate growth expectations, evaluations, and treatment.

A prospective study of posttransplant cyclophosphamide for unrelated donor peripheral blood stem cell transplant with special attention to graft content and the impact of a higher γδ T cell dose.

Posttransplant cyclophosphamide (PtCy) has been shown to decrease post-hematopoietic stem cell transplant acute and chronic graft-versus-host disease (GVHD). In this study, PtCy was used in 44 patients along with mycophenolate and tacrolimus with HLA matched (29) and mismatched (15) unrelated donors to determine the impact of graft content on outcome; thus, all patients had flow cytometric analysis of their graft content including the number of B cells, NK cells, and various T cell subsets. Higher γδ T cell dose was associated with the development of acute GVHD (p = .0038). For PtCy, further studies of the cell product along with further graft manipulation, such as selective γδ T cell depletion, could potentially improve outcomes.

A Dominant Mutation in Human RAD51 Reveals Its Function in DNA Interstrand Crosslink Repair Independent of Homologous Recombination.

Repair of DNA interstrand crosslinks requires action of multiple DNA repair pathways, including homologous recombination. Here, we report a de novo heterozygous T131P mutation in RAD51/FANCR, the key recombinase essential for homologous recombination, in a patient with Fanconi anemia-like phenotype. In vitro, RAD51-T131P displays DNA-independent ATPase activity, no DNA pairing capacity, and a co-dominant-negative effect on RAD51 recombinase function. However, the patient cells are homologous recombination proficient due to the low ratio of mutant to wild-type RAD51 in cells. Instead, patient cells are sensitive to crosslinking agents and display hyperphosphorylation of Replication Protein A due to increased activity of DNA2 and WRN at the DNA interstrand crosslinks. Thus, proper RAD51 function is important during DNA interstrand crosslink repair outside of homologous recombination. Our study provides a molecular basis for how RAD51 and its associated factors may operate in a homologous recombination-independent manner to maintain genomic integrity.

H3K36 methylation promotes longevity by enhancing transcriptional fidelity.

Epigenetic mechanisms, including histone post-translational modifications, control longevity in diverse organisms. Relatedly, loss of proper transcriptional regulation on a global scale is an emerging phenomenon of shortened life span, but the specific mechanisms linking these observations remain to be uncovered. Here, we describe a life span screen in Saccharomyces cerevisiae that is designed to identify amino acid residues of histones that regulate yeast replicative aging. Our results reveal that lack of sustained histone H3K36 methylation is commensurate with increased cryptic transcription in a subset of genes in old cells and with shorter life span. In contrast, deletion of the K36me2/3 demethylase Rph1 increases H3K36me3 within these genes, suppresses cryptic transcript initiation, and extends life span. We show that this aging phenomenon is conserved, as cryptic transcription also increases in old worms. We propose that epigenetic misregulation in aging cells leads to loss of transcriptional precision that is detrimental to life span, and, importantly, this acceleration in aging can be reversed by restoring transcriptional fidelity.

Evaluating Responses to Gluten Challenge: A Randomized, Double-Blind, 2-Dose Gluten Challenge Trial.

BACKGROUND & AIMS: Gluten challenge is used to diagnose celiac disease (CeD) and for clinical research. Sustained gluten exposure reliably induces histologic changes but is burdensome. We investigated the relative abilities of multiple biomarkers to assess disease activity induced by 2 gluten doses, and aimed to identify biomarkers to supplement or replace histology. METHODS: In this randomized, double-blind, 2-dose gluten-challenge trial conducted in 2 US centers (Boston, MA), 14 adults with biopsy-proven CeD were randomized to 3 g or 10 g gluten/d for 14 days. The study was powered to detect changes in villous height to crypt depth, and stopped at planned interim analysis on reaching this end point. Additional end points included gluten-specific cluster of differentiation (CD)4 T-cell analysis with HLA-DQ2-gluten tetramers and enzyme-linked immune absorbent spot, gut-homing CD8 T cells, interleukin-2, symptoms, video capsule endoscopy, intraepithelial leukocytes, and tissue multiplex immunofluorescence. RESULTS: All assessments showed changes with gluten challenge. However, time to maximal change, change magnitude, and gluten dose-response relationship varied. Villous height to crypt depth, video capsule endoscopy enteropathy score, enzyme-linked immune absorbent spot, gut-homing CD8 T cells, intraepithelial leukocyte counts, and HLA-DQ2-restricted gluten-specific CD4 T cells showed significant changes from baseline at 10 g gluten only; symptoms were significant at 3 g. Symptoms and plasma interleukin-2 levels increased significantly or near significantly at both doses. Interleukin-2 appeared to be the earliest, most sensitive marker of acute gluten exposure. CONCLUSIONS: Modern biomarkers are sensitive and responsive to gluten exposure, potentially allowing less invasive, lower-dose, shorter-duration gluten ingestion. This work provides a preliminary framework for rational design of gluten challenge for CeD research. ClinicalTrials.gov number, NCT03409796.

Risk score to predict event-free survival after hematopoietic cell transplant for sickle cell disease.

We developed a risk score to predict event-free survival (EFS) after allogeneic hematopoietic cell transplantation for sickle cell disease. The study population (n = 1425) was randomly split into training (n = 1070) and validation (n = 355) cohorts. Risk factors were identified and validated via Cox regression models. Two risk factors of 9 evaluated were predictive for EFS: age at transplantation and donor type. On the basis of the training cohort, patients age 12 years or younger with an HLA-matched sibling donor were at the lowest risk with a 3-year EFS of 92% (score, 0). Patients age 13 years or older with an HLA-matched sibling donor or age 12 years or younger with an HLA-matched unrelated donor were at intermediate risk (3-year EFS, 87%; score, 1). All other groups, including patients of any age with a haploidentical relative or HLA-mismatched unrelated donor and patients age 13 years or older with an HLA-matched unrelated donor were high risk (3-year EFS, 57%; score, 2 or 3). These findings were confirmed in the validation cohort. This simple risk score may guide patients with sickle cell disease and hematologists who are considering allogeneic transplantation as a curative treatment relative to other available contemporary treatments.

Complications and owner satisfaction associated with limb amputation in cats: 59 cases (2007-2017).

BACKGROUND: Limb amputation may be recommended in domestic cats following a severe injury or disease. The purpose of the study was to report the signalment, the complications, recovery outcome, owner satisfaction and expectations of domestic cats following limb amputation. RESULTS: Medical records of 3 specialty hospitals were reviewed for cats that received a single limb amputation in a 10 year period (2007-2017). These cat owners were contacted, and 59 owners completed surveys, comprising the study population. The most common reasons for limb amputation were neoplasia (54.2%, 32/59), traumatic injury (40.7%, 24/59), bone or joint infection (3.4%, 2/59), and thromboembolism (1.7%, 1/59). Thirty-four cats (57.6%) had postoperative complications. Of the fifty-nine surveys, 52.5% reported minor complications and 5.1% reported major complications. There were no differences in postoperative complication rates for thoracic versus pelvic limb amputations. All owners reported either excellent (77.9%, 46/59), good (20.3% 12/59), or fair (1.7%, 1/59) satisfaction with the procedure. Based on their previous experiences, 84.7% (50/59) of owners would elect limb amputation if medically warranted for another pet. The remaining 15.3% of owners who would not elect limb amputation again had experienced death of their pet with a median survival time of 183 days. CONCLUSION: Owners reported a positive satisfaction when considering complications, recovery outcome, and expectations. This study can be used by veterinarians to guide cat owners in the decision making process of limb amputation.

Withdrawal from cocaine conditioning progressively alters AMPA receptor-mediated transmission in the ventral hippocampus.

Drugs of abuse, such as cocaine, produce aberrant changes in synaptic transmission and plasticity that emerge throughout withdrawal. One region of the brain that displays a high degree of synaptic plasticity, as well as connectivity with mesolimbic structures such as the nucleus accumbens, is the ventral hippocampus (vH). Here, we investigated the effects of an escalating cocaine dosing schedule on vH CA1 excitatory transmission by measuring place preference and recording excitatory postsynaptic currents (EPSCs) at three different withdrawal time points: withdrawal day (WD) 2, 9 or 28. Behaviourally, this escalating cocaine-conditioning protocol was capable of producing conditioned place preference that persisted through WD28. Physiologically, cocaine conditioning produced an increase in vH excitatory transmission on WD2 that appeared to be the result of an increase in calcium-impermeable (CI)-AMPA receptor density. Excitatory transmission was still enhanced in cocaine-treated animals on WD9; however, a significant increase in the contribution of calcium-permeable (CP)-AMPA receptors to EPSCs was detected as compared with WD2. By WD28, these CP-AMPA receptors provided a major contribution to vH CA1 excitatory transmission, resulting in synaptic responses distinct from WD2 and WD9. Taken together, these results highlight progressive changes in vH synaptic transmission during withdrawal that may enhance cocaine contextual associations.

Correction of Fanconi Anemia Mutations Using Digital Genome Engineering.

Fanconi anemia (FA) is a rare genetic disease in which genes essential for DNA repair are mutated. Both the interstrand crosslink (ICL) and double-strand break (DSB) repair pathways are disrupted in FA, leading to patient bone marrow failure (BMF) and cancer predisposition. The only curative therapy for the hematological manifestations of FA is an allogeneic hematopoietic cell transplant (HCT); however, many (>70%) patients lack a suitable human leukocyte antigen (HLA)-matched donor, often resulting in increased rates of graft-versus-host disease (GvHD) and, potentially, the exacerbation of cancer risk. Successful engraftment of gene-corrected autologous hematopoietic stem cells (HSC) circumvents the need for an allogeneic HCT and has been achieved in other genetic diseases using targeted nucleases to induce site specific DSBs and the correction of mutated genes through homology-directed repair (HDR). However, this process is extremely inefficient in FA cells, as they are inherently deficient in DNA repair. Here, we demonstrate the correction of FANCA mutations in primary patient cells using 'digital' genome editing with the cytosine and adenine base editors (BEs). These Cas9-based tools allow for C:G > T:A or A:T > C:G base transitions without the induction of a toxic DSB or the need for a DNA donor molecule. These genetic corrections or conservative codon substitution strategies lead to phenotypic rescue as illustrated by a resistance to the alkylating crosslinking agent Mitomycin C (MMC). Further, FANCA protein expression was restored, and an intact FA pathway was demonstrated by downstream FANCD2 monoubiquitination induction. This BE digital correction strategy will enable the use of gene-corrected FA patient hematopoietic stem and progenitor cells (HSPCs) for autologous HCT, obviating the risks associated with allogeneic HCT and DSB induction during autologous HSC gene therapy.

SBML Level 3: an extensible format for the exchange and reuse of biological models.

Systems biology has experienced dramatic growth in the number, size, and complexity of computational models. To reproduce simulation results and reuse models, researchers must exchange unambiguous model descriptions. We review the latest edition of the Systems Biology Markup Language (SBML), a format designed for this purpose. A community of modelers and software authors developed SBML Level 3 over the past decade. Its modular form consists of a core suited to representing reaction-based models and packages that extend the core with features suited to other model types including constraint-based models, reaction-diffusion models, logical network models, and rule-based models. The format leverages two decades of SBML and a rich software ecosystem that transformed how systems biologists build and interact with models. More recently, the rise of multiscale models of whole cells and organs, and new data sources such as single-cell measurements and live imaging, has precipitated new ways of integrating data with models. We provide our perspectives on the challenges presented by these developments and how SBML Level 3 provides the foundation needed to support this evolution.

Transferrin receptor 1 controls systemic iron homeostasis by fine-tuning hepcidin expression to hepatocellular iron load.

Transferrin receptor 1 (Tfr1) mediates uptake of circulating transferrin-bound iron to developing erythroid cells and other cell types. Its critical physiological function is highlighted by the embryonic lethal phenotype of Tfr1-knockout (Tfrc-/-) mice and the pathologies of several tissue-specific knockouts. We generated TfrcAlb-Cre mice bearing hepatocyte-specific ablation of Tfr1 to explore implications in hepatocellular and systemic iron homeostasis. TfrcAlb-Cre mice are viable and do not display any apparent liver pathology. Nevertheless, their liver iron content (LIC) is lower compared with that of control Tfrcfl/fl littermates as a result of the reduced capacity of Tfr1-deficient hepatocytes to internalize iron from transferrin. Even though liver Hamp messenger RNA (mRNA) and serum hepcidin levels do not differ between TfrcAlb-Cre and Tfrcfl/fl mice, Hamp/LIC and hepcidin/LIC ratios are significantly higher in the former. Importantly, this is accompanied by modest hypoferremia and microcytosis, and it predisposes TfrcAlb-Cre mice to iron-deficiency anemia. TfrcAlb-Cre mice appropriately regulate Hamp expression following dietary iron manipulations or holo-transferrin injection. Holo-transferrin also triggers proper induction of Hamp mRNA, ferritin, and Tfr2 in primary TfrcAlb-Cre hepatocytes. We further show that these cells can acquire 59Fe from 59Fe-transferrin, presumably via Tfr2. We conclude that Tfr1 is redundant for basal hepatocellular iron supply but essential for fine-tuning hepcidin responses according to the iron load of hepatocytes. Our data are consistent with an inhibitory function of Tfr1 on iron signaling to hepcidin via its interaction with Hfe. Moreover, they highlight hepatocellular Tfr1 as a link between cellular and systemic iron-regulatory pathways.

Multiply restimulated human thymic regulatory T cells express distinct signature regulatory T-cell transcription factors without evidence of exhaustion.

BACKGROUND AIMS: Adoptive transfer of suppressive CD4+CD25+ thymic regulatory T cells (tTregs) can control auto- and alloimmune responses but typically requires in vitro expansion to reach the target cell number for efficacy. Although the adoptive transfer of expanded tTregs purified from umbilical cord blood ameliorates graft-versus-host disease in patients receiving hematopoietic stem cell transplantation for lymphohematopoietic malignancy, individual Treg products of 100 × 106 cells/kg are manufactured over an extended 19-day time period using a process that yields variable products and is both laborious and costly. These limitations could be overcome with the availability of 'off the shelf' Treg. RESULTS: Previously, the authors reported a repetitive restimulation expansion protocol that maintains Treg phenotype (CD4+25++127-Foxp3+), potentially providing hundreds to thousands of patient infusions. However, repetitive stimulation of effector T cells induces a well-defined program of exhaustion that leads to reduced T-cell survival and function. Unexpectedly, the authors found that multiply stimulated human tTregs do not develop an exhaustion signature and instead maintain their Treg gene expression pattern. The authors also found that tTregs expanded with one or two rounds of stimulation and tTregs expanded with three or five rounds of stimulation preferentially express distinct subsets of a group of five transcription factors that lock in Treg Foxp3expression, Treg stability and suppressor function. Multiply restimulated Tregs also had increased transcripts characteristic of T follicular regulatory cells, a Treg subset. DISCUSSION: These data demonstrate that repetitively expanded human tTregs have a Treg-locking transcription factor with stable FoxP3 and without the classical T-cell exhaustion gene expression profile-desirable properties that support the possibility of off-the-shelf Treg therapeutics.

Weight-based mycophenolate mofetil dosing predicts acute GVHD and relapse after allogeneic hematopoietic cell transplantation.

OBJECTIVES: Higher MMF dose can reduce acute GVHD risk after allogeneic hematopoietic cell transplantation (HCT). We examined the effect of MMF dose, relative to patient actual body weight (mg/kg/day), on outcomes of 680 adults after HCT. METHODS: MMF was combined with cyclosporine (n = 599) or sirolimus (n = 81). We divided MMF dose/kg/day in quartiles. RESULTS: The median time to grade II-IV acute GVHD was 32 days. The incidence of grade II-IV acute GVHD at day 30 was 30% in 1st (<29), 20% in 2nd (29-34), 16% in 3rd (35-41), and 19% in 4th (≥42) quartile (P < .01). Corresponding relapse incidence at 1 year was 16%, 25%, 27%, and 31%, respectively (P = .01). In multivariate analysis, as compared to 1st quartile, higher dose of weight-based MMF reduced grade II-IV acute GVHD (HR = 0.64 for 2nd, HR = 0.48 for 3rd, and HR = 0.55 for 4th quartile), but increased the risk of relapse (HR = 1.63 for 2nd, HR = 1.75 for 3rd, and HR = 2.31 for 4th quartile). CONCLUSIONS: Weight-based MMF dose had no significant impact on engraftment, chronic GVHD, or survival. These data suggest that higher weight-based MMF dose reduces the risk of acute GVHD at the expense of increased relapse and supports conducting prospective studies to optimize MMF dosing after HCT.

Guidelines for Cord Blood Unit Selection.

Optimal cord blood (CB) unit selection is critical to maximize the likelihood of successful engraftment and survival after CB transplantation (CBT). However, unit selection can be complex because multiple characteristics must be considered including unit cell dose, donor-recipient human leukocyte antigen (HLA) match, and unit quality. This review provides evidence-based and experience-based comprehensive guidelines for CB unit selection. Topics addressed include the use of both the TNC and the CD34+ cell dose, as well as the CD34+ cell to TNC content ratio to evaluate unit progenitor cell content and engraftment potential, the acceptable TNC and CD34+ cell dose criteria that define an adequate single-unit graft, and the indication and acceptable cell dose criteria for double-unit grafts. The acceptable criteria for 6-loci (HLA-A, -B antigen, -DRB1 allele) and 8-allele (HLA-A, -B, -C, -DRB1) donor-recipient HLA match, the evaluation of patients with donor-specific HLA antibodies, and the multiple determinants of unit quality are also reviewed in detail. Finally, a practical step-by-step guide to CB searches and the principles that guide ultimate graft selection are outlined.

Low Nonrelapse Mortality after HLA-Matched Related 2-Step Hematopoietic Stem Cell Transplantation Using Cyclophosphamide for Graft-versus-Host Disease Prophylaxis and the Potential Impact of Non- Cyclophosphamide-Exposed T Cells on Outcomes.

The use of cyclophosphamide (CY) for bidirectional tolerization of recipient and donor T cells is associated with reduced rates of graft-versus-host disease (GVHD) and nonrelapse mortality (NRM) after HLA-matched hematopoietic stem cell transplantation (HSCT). However, recurrent disease remains the primary barrier to long-term survival. We extended our 2-step approach to HLA-matched related HSCT using a radiation-based myeloablative conditioning regimen combined with a high dose of T cells in an attempt to reduce relapse rates while maintaining the beneficial effects of CY tolerization. After conditioning, patients received their grafts in 2 components: (1) a fixed dose of 2 × 108/kg T cells, followed 2 days later by CY, and (2) a CD34-selected graft containing a small residual amount of non-CY-exposed T cells, at a median dose of 2.98 × 103/kg. Forty-six patients with hematologic malignancies were treated. Despite the myeloablative conditioning regimen and use of high T cell doses, the cumulative incidences of grade II-IV acute GVHD, chronic GVHD, and NRM at 1 year and 5 years were very low, at 13%, 9%, and 4.3%, respectively. This contributed to a high overall survival of 89.1% at 1 year and 65.8% at 5 years. Relapse was the primary cause of mortality, with a cumulative incidence of 23.9% at 1 year and 45.7% at 5 years. In a post hoc analysis, relapse rates were significantly lower in patients receiving greater than versus those receiving less than the group median of non-CY-exposed residual T cells in the CD34 product (19.3% versus 58.1%; P = .009), without a concomitant increase in NRM. In its current form, this 2-step regimen was highly tolerable, but strategies to reduce relapse, potentially the addition of T cells not exposed to CY, are needed.