Late Relapse after Allogeneic Stem Cell Transplantation in Patients Treated for Acute Myeloid Leukemia: Relapse Incidence, Characteristics, Role of Conditioning Regimen, and Outcome

Late relapse, beyond 2 years following alloHSCT for AML, is rare. Among the 376 patients allografted for AML in our center between 1990 and 2016, 142 (38%) relapsed. The majority (68%) of relapses occurred during the first year following transplantation. Beyond 2 years after alloHSCT, relapse was observed in 26 patients, representing 6.9% of the whole transplanted cohort and 18.3% of the relapsing patients. Cytogenetics at relapse was available in 21 patients and remained for 15 of them concordant to that at diagnosis. The majority (85.7%) of the patients were in CR prior to transplant. Thirteen patients had grade 1-2 acute GvHD, while 13 other patients had grade 3-4 acute GvHD. None of these patients subsequently developed chronic GvHD. In multivariate analyses, a predictive factor of the absence of relapse 2 years after transplantation was the development of extensive chronic GVHD. Salvage therapy achieved new CR in 77% of these patients. We conclude that late relapse can affect a significant minority of patients allografted for AML, and the intensity of the conditioning regimen does not seem to have an impact on these relapses. Moreover, we were able to show that those patients can receive effective salvage therapy.

Successful treatment of congenital erythropoietic porphyria using matched unrelated hematopoietic stem cell transplantation in an adult: A case report

Congenital erythropoietic porphyria (CEP), or Gunther disease, is a rare genetic disease responsible for severe dermatologic, hepatic and/or haematological damages related to the deficient activity of the uroporphyrinogen III synthase. Allogeneic stem cell transplantation (Allo-SCT) represents the only curative treatment and few allotransplanted cases have been reported in children but not in adults. Here we report for the first time the successful cure of a 46-year old man with CEP with a 5-year follow-up after Allo-SCT.

Phase I study of zoledronic acid combined with escalated doses of interleukine-2 for early in vivo generation of Vγ9Vδ2 T-cells after haploidentical stem cell transplant with posttransplant cyclophosphamide

The presence of donor Vγ9Vδ2 T-cells after haploidentical hematopoietic stem cell transplant (h-HSCT) has been associated with improved disease-free survival. These cells kill tumor cells in a non-MHC restricted manner, do not induce graft-versus-host disease (GVHD), and can be generated by stimulation with zoledronic acid (ZA) in combination with interleukin-2 (IL-2). This monocentric phase I, open-label, dose-escalating study (ClinicalTrials.gov: NCT03862833) aimed at evaluating the safety and possibility to generate Vγ9Vδ2 T-cells early after h-HSCT. It applied a standard 3 + 3 protocol to determine the maximum tolerated dose (MTD) of increasing low-doses of IL-2 (5 days [d] per week, 4 weeks) in combination with a single dose of ZA, starting both the first Monday after d + 15 posttransplant. Vγ9Vδ2 T-cell monitoring was performed by multiparameter flow cytometry on blood samples and compared with a control cohort of h-HSCT recipients. Twenty-six patients were included between April 2019 and September 2022, 16 of whom being ultimately treated and seven being controls who received h-HSCT only. At the three dose levels tested, 1, 0, and 1 dose-limiting toxicities were observed. MTD was not reached. A significantly higher number of Vγ9Vδ2 T-cells was observed during IL-2 treatment compared with controls. In conclusion, early in vivo generation of Vγ9Vδ2 T-cells is feasible after h-HSCT by using a combination of ZA and repeated IL-2 infusions. This study paves the way to a future phase 2 study, with the hope to document lesser posttransplant relapse with this particular adaptive immunotherapy.

Assessment of monocytic-myeloid-derived suppressive cells (M-MDSC) before and after allogeneic hematopoietic stem cell transplantation in acute leukemia patients

In this monocentric prospective study, the influence on long-term outcomes of peripheral blood levels of monocytic-myeloid-derived suppressive cells (M-MDSC) was investigated in 56 patients with acute leukemia (myeloid n = 47; lymphoid n = 9) before and after (Days+60/+90) allogeneic hematopoietic stem cell transplantation (Allo-HSCT). A risk of relapse was found to be associated with a level of pregraft M-MDSC above 1.4% by ROC curve analysis. In multivariate analysis, this threshold retained a strong statistical significance (HR: 5.94 [2.09-16.87], p = 0.001). Considering only the group of patients who were in complete remission prior to Allo-HSCT (n = 44), a significant prediction of relapse was found to be associated, in multivariate analysis, with a level of pregraft M-MDSC above 1.4% (HR: 55.01 [14.95-202.37], p < 0.001) together with pregraft-positive measurable -residual disease (MRD) (HR: 11.04 [1.89-64.67], p = 0.008). A poorer OS (HR: 6.05 [1.24-29.59], p = 0.026) and disease-free survival (HR: 6.52 [1.41-30.19], p = 0.016) were also associated with higher levels of pregraft M-MDSC. Remarkably, no relapse occurred in patients with pregraft-negative MRD and ≤1.4% of M-MDSC (vs. a 3-year relapse rate of 60% for others, p = 0.004). Patients developing grade 3-4 acute graft-versus-host-disease (GVHD, median occurrence: day+30 posttransplant) showed significantly higher levels of M-MDSC% at days +60 and +90, suggesting a possible amplification of these immunosuppressive cells as a reaction to GVHD. In conclusion, this prospective study demonstrates a negative impact of higher proportions of peripheral M-MDSC before Allo-HSCT in leukemic patients. This paves the way to potential therapeutic intervention to decrease M-MDSC levels before Allo-HSCT and thus perhaps the incidence of relapse in such patients.

Tocilizumab in combination with a standard induction chemotherapy in acute myeloid leukaemia patients (TOCILAM study): a single-centre, single-arm, phase 1 trial

Background

In acute myeloid leukaemia (AML), interleukin-6 (IL-6) promotes chemo-resistance and its levels correlate with poor prognosis. IL-6 blockade may represent a promising therapeutic strategy. We aimed to test, tocilizumab, an anti-IL-6 receptor (R) monoclonal antibody in combination with standard intensive AML induction chemotherapy.

Methods

This investigator-initiated single-centre phase 1 trial was conducted at Nantes University Hospital in France. According to a continual reassessment method, three escalating doses were tested of intravenous (IV) tocilizumab (4, 6, and 8 mg/kg) administered at day (d) 8 of a standard AML induction chemotherapy (IV idarubicine 8 mg/m2 d1 to d5 + IV cytarabine 100 mg/m2 d1 to d7). All adults (aged ≥ 18 years) with an Eastern Cooperative Oncology Group performance status of 0-2 and with a newly diagnosed (excluding patients with a favourable risk according to ELN-2017 classification if <60 year-old) or a relapsed/refractory AML were eligible. The primary objective was to determine the maximum tolerated dose of tocilizumab to administrate with a standard intensive AML induction. Safety outcomes were continuously monitored for at each participant contact. This trial is registered with ClinicalTrials.gov, NCT04547062.

Findings

Between Dec 29, 2020 and Dec 1, 2022, 12 patients were enrolled, of whom 75% had an ELN-2017 high-risk profile, and were treated with tocilizumab- two patients at 4 mg/kg, two at 6 mg/kg and eight at 8 mg/kg of tocilizumab. No dose-limiting toxicity related to tocilizumab was documented. There were nine serious adverse events, none of which were related to tocilizumab, and there was no treatment-related deaths. MTD was thus not reached. Two deaths occurred during induction. In the remaining ten evaluable patients, nine responded to treatment.

Interpretation

The combination of tocilizumab with standard AML intensive induction appears to be safe and resulting responses are encouraging. A dose of 8 mg/kg of tocilizumab given at day 8 of induction could be used for further phase 2/3 studies.

Funding

The Leucémie Espoir Atlantique Famille (LEAF)-"Tous avec Fabien" association.

Non-Expressed Donor KIR3DL1 Alleles May Represent a Risk Factor for Relapse after T-Replete Haploidentical Hematopoietic Stem Cell Transplantation

KIR3DL1 alleles are expressed at different levels on the natural killer (NK) cell surface. In particular, the non-expressed KIR3DL1*004 allele appears to be common in Caucasian populations. However, the overall distribution of non-expressed KIR3DL1 alleles and their clinical relevance after T-replete haploidentical hematopoietic stem cell transplantation (hHSCT) with post-transplant cyclophosphamide remain poorly documented in European populations. In a cohort of French blood donors (N = 278), we compared the distribution of expressed and non-expressed KIR3DL1 alleles using next-generation sequencing (NGS) technology combined with multi-color flow cytometry. We confirmed the predominance of the non-expressed KIR3DL1*004 allele. Using allele-specific constructs, the phenotype and function of the uncommon KIR3DL1*019 allotype were characterized using the Jurkat T cell line and NKL transfectants. Although poorly expressed on the NK cell surface, KIR3DL1*019 is retained within NK cells, where it induces missing self-recognition of the Bw4 epitope. Transposing our in vitro observations to a cohort of hHSCT patients (N = 186) led us to observe that non-expressed KIR3DL1 HSC grafts increased the incidence of relapse in patients with myeloid diseases. Non-expressed KIR3DL1 alleles could, therefore, influence the outcome of hHSCT.

Post-transplant cyclophosphamide as sole GHVD prophylaxis after matched reduced-intensity conditioning allotransplant

BACKGROUND

Post-transplant cyclophosphamide (PTCY) alone as graft-versus-host disease (GVHD) prophylaxis may avoid/reduce short- and mid-term toxicities of drugs commonly used for GVHD prophylaxis, accelerate immune reconstitution after the graft to decrease infections and facilitate the early integration of adjunct maintenance therapies to prevent relapse.

OBJECTIVE

A prospective phase 2 study was designed in order to assess the feasibility and safety of PTCY as a sole GVHD prophylaxis in adult patients receiving a Baltimore-based reduced-intensity conditioning (RIC) peripheral blood (PB) allogeneic hematopoietic stem cell transplantation (Allo-HSCT) with a matched donor.

STUDY DESIGN

Patients were planned to be included stepwise up to 59 evaluable PTCY recipients, in order to be able to stop the protocol in case of excessive corticosteroid resistant grade 3-4 severe acute GVHD (aGVHD). Because a high incidence of grade 2-4 aGVHD was observed after analysis of the first 27 patients, the protocol was amended to test the addition of 1 day of anti-thymoglobulin to PTCY. In spite of this, the trial had to be stopped after 38 treated patients, because of an unacceptable rate of grade 3-4 aGVHD. Donors were matched related to 12 patients and unrelated to 26.

RESULTS

With a median follow-up of 29.6 months, 2-year overall, disease-free and GVHD-free relapse-free (GRFS) survivals were respectively 65.4%, 62.1% and 46.9%. Cumulative incidences of grade 2-4 and 3-4 aGVHD at day 100 were 52.6% and 21.1%, respectively, while that of moderate/severe chronic(c) GVHD was 15.7% at 2 years. Addition of ATG to PTCY did influence neither aGVHD, cGVHD nor GRFS.

CONCLUSION

Despite paradoxically good survivals, especially GRFS, this study failed to demonstrate that PTCY (± ATG) alone can be used for Baltimore-based RIC PB Allo-HSCT with matched donors. Other combinations should be tested to try and avoid long-term use of immunosuppressive drugs following Allo-HSCT in this setting.

Assessment of COVID-19 Incidence and Severity Among Recipients of Allogenic Stem Cell Transplant After 1 or 2 mRNA Booster Doses During the Omicron Wave in France

This cohort study assesses the incidence and severity of COVID-19 among vaccinated recipients of allogenic stem cell transplant in a single center after 1 or 2 messenger RNA booster doses during the Omicron wave in France.

Effectiveness of a third dose of BNT162b2 anti-SARS-CoV-2 mRNA vaccine over a 6-month follow-up period in allogenic hematopoietic stem cells recipients

This study reports the effectiveness of three injections of BNT162b2 anti-SARS-CoV-2 mRNA vaccine in 141 Allo-HSCT recipients with a median follow-up of 6 months post-third shot. We demonstrate a long-term high protection of Allo-HSCT recipients since only 2 infections and one death related to COVID-19 occurred.

Peripheral levels of monocytic myeloid-derived suppressive cells before and after first induction predict relapse and survivals in AML patients

Myeloid Derived Suppressive Cells (MDSC) are capable to suppress innate and adaptive immune responses, thus favouring solid cancer progression. However, little is known about the role of MDSC in acute myeloid leukaemia (AML). In this monocentric prospective study, 73 adult AML patients, eligible for first‐line intensive chemotherapy, were included with the aim to study the influence on long‐term outcomes of peripheral blood (PB) levels of monocytic (M) MDSC (M‐MDSC) assessed by flow cytometry. A percentage of peripheral M‐MDSC higher than 0.55% of leukocytes at diagnosis and a decrease of M‐MDSC% after induction came out both as independent negative prognostic factors for leukaemia‐free and overall survival.

Strong SARS-CoV-2 T-Cell Responses after One or Two COVID-19 Vaccine Boosters in Allogeneic Hematopoietic Stem Cell Recipients

A full exploration of immune responses is deserved after anti-SARS-CoV-2 vaccination and boosters, especially in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT). Although several reports indicate successful humoral responses in such patients, the literature is scarce on cellular specific immunity. Here, both B- (antibodies) and T-cell responses were explored after one (V3 n = 40) or two (V4 n = 12) BNT162b2 mRNA vaccine boosters in 52 allo-HSCT recipients at a median of 755 days post-transplant (<1 year n = 9). Results were compared with those of 12 controls who had received only one booster (BNT162b2 n = 6; mRNA-1273 n = 6). All controls developed protective antibody levels (>250 BAU/mL) and anti-spike T-cell responses. Similarly, 81% of the patients developed protective antibody levels, without difference between V3 and V4 (82.5% vs. 75%, p = 0.63), and 85% displayed T-cell responses. The median frequency of anti-spike T cells did not differ either between controls or the whole cohort of patients, although it was significantly lower for V3 (but not V4) patients. COVID-19 infections were solely observed in individuals having received only one booster. These results indicate that four vaccine injections help to achieve a satisfactory level of both humoral and cellular immune protection in allo-HSCT patients.

Dramatic recovery after etoposide phosphate infusion for hemophagocytic lymphohistiocytosis/macrophage activation syndrome following treatment with tisagenlecleucel in a young patient with relapsed acute lymphoblastic leukemia: a case report

The occurrence of a secondary hemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS) after CAR-T cells infusion is very rare and mostly fatal. Treatment recommendations for such a complication are not yet established. Here we report the dramatic recovery of a HLH/MAS following tisagenlecleucel infusion in a young patient with relapsed acute lymphoblastic leukemia using etoposide phosphate (EP). We propose that monitoring for the occurrence of HLH/MAS should be part of surveillance after CAR T-cells infusion and that EP treatment appears to be useful to control this severe and rare complication.

Anti‐SARS‐CoV‐2 vaccines in recipient and/or donor before allotransplant

The impact of pre‐transplant anti‐severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2) vaccine in 20 recipients of allogeneic hematopoietic stem cell transplantation (Allo‐HSCT) and/or their donors is reported here, showing that the persistence of anti‐SARS‐CoV‐2 antibodies can be detected in almost all patients, whatever the type of vaccine used, and up to 9 months post transplant. Also, an anti‐SARS‐CoV‐2 spike glycoprotein CD3+ T‐cell response could be detected in six (35%) of 17 evaluable patients. This study provides a rationale to consider anti‐SARS‐CoV‐2 vaccination of both recipients and donors before Allo‐HSCT.

B Cell Aplasia Is the Most Powerful Predictive Marker for Poor Humoral Response after BNT162b2 mRNA SARS-CoV-2 Vaccination in Recipients of Allogeneic Hematopoietic Stem Cell Transplantation

Little is known about the immune response to SARS-CoV-2 vaccination in recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, several studies have reported that adequate protection could be provided to this population. The purpose of this study was to evaluate which factors can predict the efficacy of SARS-CoV-2 vaccination in these specifically immunosuppressed patients. Specific anti-Spike (S) antibody responses were assessed in a cohort of 117 allo-HSCT recipients after 2 injections of BNT162b2 mRNA SARS-CoV-2 vaccine (V1 and V2). Factors considered liable to influence the antibody response and analyzed in this series were the interval between allo-HSCT and V1, donor source, recipient and donor age, current immunosuppressive/chemotherapy (I/C) treatment, and levels of CD4⁺and CD8⁺ T cells, B cells, and natural killer cells at the time of V1. Overall, the S-antibody response rate, evaluated at a median of 35 days after V2, was 82.9% for the entire cohort, with 71 patients (61%) reaching the highest titer. In univariate analysis, a lower pre-V1 median total lymphocyte count, lower CD4⁺ T cell and B cell counts, ongoing I/C treatment, and a haploidentical donor were characteristic of nonhumoral responders. However, multiparameter analysis showed that B cell aplasia was the sole factor predicting the absence of a specific immune response (odds ratio, 0.01; 95% confidence interval, 0.00 to 0.10; P < 10^-3). Indeed, the rate of humoral response was 9.1% in patients with B cell aplasia versus 95.9% in patients with a B cell count >0 (P < 10^-9). These results advocate for the administration of anti-SARS-CoV-2 vaccination in allo-HSCT recipients as early as peripheral B cell levels can be detected, and also suggest the need for close monitoring of B-cell reconstitution after Allo-HSCT.

Two-dimensional square and hexagonal oxide quasicrystal approximants in SrTiO3 films grown on Pt(111)/Al2O3(0001)

The formation of two-dimensional oxide dodecagonal quasicrystals as well as related complex approximant phases was recently reported in thin films derived from BaTiO₃ or SrTiO₃ perovskites deposited on (111)-oriented Pt single crystals. Here, we use an all-thin-film approach in which the single crystal is replaced by a 10 nm thick Pt(111) buffer layer grown by molecular beam epitaxy on an Al₂O₃(0001) substrate. An ultra-thin film of SrTiO₃ was subsequently deposited by pulsed laser deposition. The film stacking and structure are fully characterized by diffraction and microscopy techniques. We report the discovery of two new complex phases obtained by reduction of this system through high temperature annealing under ultrahigh vacuum conditions. The formation of a new large square approximant with a lattice parameter equal to 44.4 Å is evidenced by low-energy electron diffraction and scanning tunneling microscopy (STM). Additionally, a new 2D hexagonal approximant phase with a lattice parameter of 28 Å has been observed depending on the preparation conditions. Both phases can be described by two different tilings constructed with the same basic square, triangle and rhombus tiles possessing a common edge length of about 6.7 Å. Using the tiling built from high resolution STM images, we propose an atomic model for each approximant which accounts for the experimental observations. Indeed, the STM images simulated using these models are found to be in excellent agreement with the experimental ones, the bright protrusions being attributed to the topmost Sr atoms. In addition our theoretical approach shows that the adhesion of the oxide layer is rather strong (-0.30 eV Å^-2). This is attributed to charge transfer, from the most electropositive elements (Sr and Ti) to the most electronegative ones (Pt and O), and to hybridization with Pt-states. Density of states calculations indicate differences in the electronic structure of the two approximants, suggesting different chemical and physical properties. This all-thin-film approach may be useful to explore the formation of complex two-dimensional oxide phases in other metal-oxide combinations.

Impact of allogeneic stem cell transplantation comorbidity indexes after haplotransplant using post-transplant cyclophosphamide

Background

Three different scoring systems have been developed to assess pre‐transplant comorbidity in allogeneic hematopoietic stem cell transplantation (Allo‐HSCT): the Hematopoietic Cell Transplantation‐Specific Comorbidity Index, the Comorbidity/Age index, and the Augmented Comorbidity/Age index. All were devised to predict overall survival (OS) and disease‐free survival (DFS) survivals and non‐relapse mortality (NRM) in patients receiving HLA‐matched Allo‐HSCT, but their performance has scarcely been studied in the haploidentical Allo‐HSCT setting with post‐transplant cyclophosphamide, a procedure in constant expansion worldwide.

Methods

To address this issue, their impact on survivals and NRM was examined in a cohort of 223 patients treated with haploidentical Allo‐HSCT in four different centers.

Results

With a median follow‐up of 35.6 months, 3‐year OS, DFS, and NRM were 48.1% ± 4%, 46.3% ± 4%, and 30.0% ± 3%, respectively. No impact was found for any of the three comorbidity scores in univariate analysis. In multivariate analyses, the only three factors associated with lower OS were DRI (p < 0.001), an older age of recipients (≥55 years old, p = 0.02) and of donors (≥40 years old, p = 0.005). Older donor age was also associated with lower DFS and higher NRM.

Conclusion

The comorbidity scores do not predict survivals nor NRM in haploidentical Allo‐HSCT with PTCY, suggesting that pre‐transplant comorbidities should not be a contra‐indication to this procedure.

Deep-Learning Assessed Muscular Hypodensity Independently Predicts Mortality in DLBCL Patients Younger Than 60 Years

Simple Summary

Cachexia is a major cause of mortality in cancer patients and is characterized by a continuous skeletal muscle loss. Muscle depletion assessed by computed tomography (CT) is a predictive marker in solid tumors but has never been assessed in non-Hodgkin’s lymphoma. Despite software improvements, its measurement remains highly time-consuming and cannot be performed in clinical practice. We report the development of a CT segmentation algorithm based on convolutional neural networks. It automates the extraction of anthropometric data from pretherapeutic CT to assess precise body composition of young diffuse large B cell lymphoma (DLBCL) patients at the time of diagnosis. In this population, muscle hypodensity appears to be an independent risk factor for mortality, and can be estimated at diagnosis with this new tool.

Abstract

Background. Muscle depletion (MD) assessed by computed tomography (CT) has been shown to be a predictive marker in solid tumors, but has not been assessed in non-Hodgkin’s lymphomas. Despite software improvements, MD measurement remains highly time-consuming and cannot be used in clinical practice. Methods. This study reports the development of a Deep-Learning automatic segmentation algorithm (DLASA) to measure MD, and investigate its predictive value in a cohort of 656 diffuse large B cell lymphoma (DLBCL) patients included in the GAINED phase III prospective trial (NCT01659099). Results. After training on a series of 190 patients, the DLASA achieved a Dice coefficient of 0.97 ± 0.03. In the cohort, the median skeletal muscle index was 50.2 cm²/m² and median muscle attenuation (MA) was 36.1 Hounsfield units (HU). No impact of sarcopenia was found on either progression free survival (PFS) or overall survival (OS). Muscular hypodensity, defined as MA below the tenth percentile according to sex, was associated with a lower OS and PFS, respectively (HR = 2.80 (95% CI 1.58–4.95), p < 0.001, and HR = 2.22 (95% CI 1.43–3.45), p < 0.001). Muscular hypodensity appears to be an independent risk factor for mortality in DLBCL and because of DLASA can be estimated in routine practice.

Early Post-Transplantation Serum Ferritin Level Predicts Survival in Recipients of Haploidentical Stem Cell Transplantation Using Post-Transplantation Cyclophosphamide as Graft-versus-Host Disease Prophylaxis

The negative impact of high serum ferritin level (SFL) before and after allogeneic hematopoietic cell transplantation (allo-HSCT) on outcomes is well recognized. However, it is poorly documented in adults undergoing haploidentical HSCT (haplo-HSCT) with post-transplantation cyclophosphamide (PTCY) for hematologic malignancies. The main objective was to assess the impact of pretransplantation and post-transplantation SFL on overall survival (OS), disease-free survival (DFS), and nonrelapse mortality (NRM) in patients undergoing haplo-HSCT with PTCY. The secondary objective was to identify factors associated with outcomes after transplantation by comparing SFL with other parameters related to the status of patients or donors. This multicentric retrospective study included 223 consecutive patients who underwent haplo-HSCT with PTCY in 4 French centers (Nantes, Angers, Besançon, and Brest) between October 2013 and January 2020. The impact of SFL on OS, DFS, and NRM at different time points was assessed based on receiver operating characteristic curves. With a median follow-up of 37.6 months (interquartile range, 23.5 to 51.0 months), 3-year OS, DFS, and NRM were 48.1 ± 4%, 46.3 ± 4%, and 30.0 ± 3%, respectively. Pretransplantation SFL had no impact on outcomes irrespective of the cutoff tested. Considering patients alive at 3 months post-transplantation, an SFL ≥3500 µg/L at 3 months was statistically significantly associated with worse 3-year OS (32.7 ± 8.7% versus 53.4 ± 7.2%; P = .01) and DFS (30.1 ± 8.2% versus 53.1 ± 7.1%; P = .008), with a trend toward higher NRM (33.2 ± 8.6% versus 17.6 ± 5.4%; P = .10). Similarly, high SFL (≥2700 µg/L) at 6 months post-transplantation was associated with worse 3-year OS (56.1 ± 9.1% versus 79.2 ± 6.0%; P = .02) and DFS (53.6 ± 8.7% versus 74.9 ± 6.2%; P = .01), with a trend toward higher NRM (21.4 ± 7.4% versus 8.2 ± 4.0%; P = .10). In multivariate analysis, high 3-month and 6-month FL remained associated with lower OS and DFS, with a trend toward higher NRM. Pretransplantation SFL appears to have no impact on outcomes in haplo-HSCT with PTCY, in contrast to what is documented in the matched allo-HSCT setting. In contrast, in the haplo-HSCT setting, high SFL early post-transplantation is associated with lower survival and a trend toward higher NRM.

Low number of KIR ligands in lymphoma patients favors a good rituximab-dependent NK cell response

The antibody-dependent cellular cytotoxicity (ADCC) effector function of natural killer (NK) cells is one of the known mechanisms of action for rituximab-based anti-cancer immunotherapy. Inhibition of the ADCC function of NK cells through interactions between inhibitory killer cell immunoglobulin-like receptors (KIRs) and HLA class I ligands is associated with resistance of cancers to rituximab. In this study, we deeply investigated the impact of KIR, HLA class I, and CD16 genotypes on rituximab-dependent NK cell responses in both an in vitro cellular model from healthy blood donors and ex vivo rituximab-treated non-Hodgkin lymphoma (NHL) patients. We highlight that an HLA environment with limited KIR ligands is beneficial to promoting a higher frequency of KIR⁺ NK cells including both educated and uneducated NK cells, two NK cell compartments that demonstrate higher rituximab-dependent degranulation than KIR⁻ NK cells. In contrast, a substantial KIR ligand environment favors a higher frequency of poorly effective KIR⁻ NK cells and numerous functional KIR/HLA inhibitions of educated KIR⁺ NK cells. These phenomena explain why NHL patients with limited KIR ligands respond better to rituximab. In this HLA environment, CD16 polymorphism appears to have a collateral effect. Furthermore, we show the synergic effect of KIR2DS1, which strongly potentiates NK cell ADCC from C2⁻ blood donors against C2⁺ target cells. Taken together, these results pave the way for stronger prediction of rituximab responses for NHL patients. HLA class I typing and peripheral blood KIR⁺ NK cell frequency could be simple and useful markers for predicting rituximab response.

Safety and immunogenicity of a first dose of SARS-CoV-2 mRNA vaccine in allogeneic hematopoietic stem-cells recipients

This was a monocentric prospective study testing the efficacy and safety of a first injection of BNT162b2 (Pfizer‐BioNTech) in 112 Allo‐HSCT patients. Antibody response to SARS‐CoV‐2 spike protein receptor‐binding domain was tested at the time of the second injection (Roche Elecsys). The study also included a non‐randomized control arm of 26 healthy controls. This study shows that a first dose of SARS‐CoV‐2 messenger RNA vaccine is safe and provides a 55% rate of seroconversion in allotransplanted patients compared to 100% for the controls (p < 0.001). Factors influencing the absence of response in patients were recent transplantation (<2 years), lymphopenia (<1 × 10⁹/L) and immunosuppressive treatment or chemotherapy at the time of vaccination.

Monoclonal antibodies as an addition to current myeloma therapy strategies

INTRODUCTION

Immunotherapy has emerged as a major class in the therapeutic arsenal of multiple myeloma. Cell-based immunotherapy (CAR T-cells) and monoclonal antibody-based immunotherapy (naked monoclonal antibodies, antibody-drug conjugates, and bispecific T-cell engagers) are the two cornerstones of this novel approach for myeloma patients. Among numerous targets evaluated in the previous decade; CD38, SLAMF7, and, more recently, BCMA stand as the most promising.

AREAS COVERED

This review presents and discusses the currently available data regarding monoclonal antibodies in the treatment of multiple myeloma.

EXPERT OPINION

Anti-CD38-naked monoclonal antibodies have become a standard-of-care in multiple myeloma, greatly improving the depth and duration of response when combined with conventional therapy. Elotuzumab is approved in the relapse setting in combination with pomalidomide and maybe an interesting option in patients whose disease became refractory to anti-CD38 monoclonal antibodies. Anti-BCMA drug conjugates and bispecific T-cell engager antibodies are promising new molecules in the multiple myeloma armamentarium.

Antithymocyte globulin administration in patients with profound lymphopenia receiving a PBSC purine analog/busulfan-based conditioning regimen allograft

Graft-versus host disease (GVHD) remains one of the main causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (ASCT). Prophylactic T cell depletion via antithymocyte globulin (ATG) during ASCT conditioning is one of the standards of care for GVHD prophylaxis, although the optimal dosing strategy is still unclear. Recent studies have reported that absolute lymphocyte count at the time of ATG administration could predict survivals in ASCT from unrelated donors. Here this issue was examined in 116 patients receiving peripheral blood stem cells (PBSC) ASCT with purine analog/busulfan-based conditioning regimens between 2009 and 2019 in our department. The impact of lymphopenia at the time of ATG administration was evaluated in terms of overall survival, disease-free survival and GVHD-free/relapse-free survival. After a median follow-up of 4 years, no adverse effect of a profound lymphopenia was observed on patients' outcome. Notably, a reduced dose of ATG in patients with profound lymphopenia did not translate into better survivals. This study indicates that ATG can be administered whatever the recipient's lymphocyte counts in patients receiving a PBSC purine analog/busulfan-based conditioning regimen ASCT.

Restoring Apoptosis with BH3 Mimetics in Mature B-Cell Malignancies

Apoptosis is a highly conserved mechanism enabling the removal of unwanted cells. Mitochondrial apoptosis is governed by the B-cell lymphoma (BCL-2) family, including anti-apoptotic and pro-apoptotic proteins. Apoptosis evasion by dysregulation of anti-apoptotic BCL-2 members (BCL-2, MCL-1, BCL-XL) is a common hallmark in cancers. To divert this dysregulation into vulnerability, researchers have developed BH3 mimetics, which are small molecules that restore effective apoptosis in neoplastic cells by interfering with anti-apoptotic proteins. Among them, venetoclax is a potent and selective BCL-2 inhibitor, which has demonstrated the strongest clinical activity in mature B-cell malignancies, including chronic lymphoid leukemia, mantle-cell lymphoma, and multiple myeloma. Nevertheless, mechanisms of primary and acquired resistance have been recently described and several features such as cytogenetic abnormalities, BCL-2 family expression, and ex vivo drug testing have to be considered for predicting sensitivity to BH3 mimetics and helping in the identification of patients able to respond. The medical need to overcome resistance to BH3 mimetics supports the evaluation of innovative combination strategies. Novel agents including MCL-1 targeting BH3 mimetics are currently evaluated and may represent new therapeutic options in the field. The present review summarizes the current knowledge regarding venetoclax and other BH3 mimetics for the treatment of mature B-cell malignancies.

Pomalidomide, cyclophosphamide, and dexamethasone for relapsed/refractory multiple myeloma patients in a real-life setting: a single-center retrospective study

Pomalidomide dexamethasone is a standard of care for relapsed multiple myeloma (MM) patients who received at least two prior lines of therapy, including both lenalidomide and proteasome inhibitors (PI). We report here a real-life single-center series of 49 consecutive patients with relapsed and refractory MM treated with the triplet pomalidomide cyclophosphamide dexamethasone (PCD) combination. The median of prior lines of therapy was 3 and all patients were previously exposed to proteasome inhibitors and lenalidomide. The overall response rate was 76%, including 27% very good partial response or better. With a median follow-up of 16 months, the median progression-free survival (PFS) was 7.3 months and the median overall survival was not reached. Regarding safety, most frequent toxicity was hematologic, including 37% grade 3-4 cytopenias. Nine patients (18%) discontinued therapy due to adverse event. Our study confirms that PCD combination is feasible and results in favorable response rate and PFS in comparison with pomalidomide dexamethasone alone.

Defining and validating a Body Skin Discomfort Index (BSDI)

OBJECTIVE

To understand the drivers of body skin discomfort and to validate a new index to assess its severity. This index should be sensitive enough to capture changes in response to treatment.

METHODS

Previous consumer studies suggested seven potential main dimensions behind skin discomfort. Four of them refer to self-declarations (stinging, itching, warming and tightening), whereas three can be assessed by a dermatologist (skin dryness, redness and desquamation). Intensity and frequency or extent of these items were measured using 0-9 ordinal scales. To generate the data for validation of a new index based on the 7 items, a group of 49 subjects complaining of skin discomfort was followed up for 5 weeks: 1-week without product application to check reproducibility, followed by 4 weeks of treatment to evaluate sensitivity to change. Items not significantly reported at baseline or with changes because of treatment not sufficiently correlated with the overall change measured by the index were discarded. A control group of 49 subjects presenting no discomfort at all was also included to check the capacity of our index to discriminate both groups. The final index (Body Skin Discomfort Index, BSDI) was normalized to facilitate the clinical interpretation of the results.

RESULTS

After discarding warming and skin redness, the BSDI is finally a five-dimension score calculated as follows: (TI + TF + SI + SF + ItI + ItF + DI + DE + DqI + DqE) 9 9/90 where T, S, It, D and Dq refer to tightness, stinging, itching, dryness, desquamation respectively, and I, F or E refers to intensity, frequency or extent. The final BSDI score displayed a good capacity to discriminate people with skin discomfort from people with 'normal skin', a good reproducibility (intraclass coefficient correlation ICC = 0.85) and a good sensitivity to detect change because of treatment (Difference vs. Baseline of 2.63 on a 0-9 scale).

CONCLUSION

The developed index, BSDI, is a reliable way to address the measurement issue of the multidimensional skin discomfort syndrome. It thus should simplify the evaluation of cosmetic products effect and helps to compare products dedicated to body cleansing.

On the cation dependence of interlamellar and interparticular water and swelling in smectite clays

The osmotic character of long-range interlamellar swelling in smectite clays is widely accepted and has been evidenced in the interlayer space by X-ray diffraction. Such a behavior in mesopores was not experimentally confirmed until the determination of the mesopore size distribution in Na-montmorillonite prepared from MX80 bentonite using thermoporometry experiments. This is confirmed here for other montmorillonite samples where the interlayer cations are alkaline and Ca(2+) cations. The nature of the interlayer cation is found as strongly influencing the behavior of the size and the swelling of mesopores. These results are supported by the BJH (Barrett, Joyner and Halenda) pore radius values issued from the nitrogen adsorption-desorption isotherms at the dry state. Thermoporometry results as a function of relative humidity ranging from 11% to 97% have shown an evolution of the mesopore sizes for a purified Na-montmorillonite. New thermoporometry data are presented in this article and confirm that the interparticle spaces in K-, Cs-, or Ca-montmorillonites are not strongly modified for all the range of relative humidity: the swelling is not observed or is strongly limited. It appears in contrast that only Li- and Na-montmorillonites undergo a mesopore swelling, distinct from the interlayer swelling. More generally, our results confirm the possibility to use thermoporometry or differential scanning calorimetry to study the structure and the evolution of swelling materials in wetting conditions such as natural clays or biological cells. In this paper, we describe the different key steps of the hydration of swelling clays such as montmorillonites saturated with alkaline cations. Using thermoporometry results combined with X-ray diffraction data, we distinguish the evolution of the porosity at the two different scales and propose a sequence of hydration dependent on the interlayer cation. From this study, it is shown that the interlayer spaces are not completely filled when the mesopores start to fill up. This implies that the swelling observed in the mesopores for Li and Na samples is due to an osmotic swelling. For the other samples, it is difficult to conclude definitively. Furthermore, we determine the different proportion of water (interlayer water and mesopore water) present in our samples by the original combination of (1) X-ray diffraction data, (2) the pore size distribution obtained by thermoporometry, and (3) recent adsorption isotherm results. It is found that the interlayer space is never completely filled by water at the studied relative humidity values for all samples except for the Cs sample.

Application of microanalytical techniques to the study of aqueous ion sorption phenomena on mineral surfaces

Nuclear microprobe analysis has been used to study the aqueous sorption of cadmium and selenium at different solution pH values onto hydroxyapatite. By coupling Particle Induced X-ray Emission (PIXE) and Rutherford Backscattering (RBS) microanalyses, we have quantified the concentration and modeled the depth distribution of Cd and Se in particles of calcium hydroxyapatites (HAP). No cadmium precipitation was observed for those experiments in which the initial concentration was greater than the solubility of Cd(OH)2 and CdCO3 at solution pH=9 and 12. The observation of the solid by transmission and scanning electron microscopies, SEM and TEM, showed the polycrystalline nature of the particles; these particles were constituted by aggregated nanocrystals. This additional information allowed us to interpret the incorporation of Cd and Se into the apatitic substrate as a penetration in the intra-particle porosity generated by this aggregation of crystals and probably not as diffusion in the solid structure.

Epidemiological changes in hepatitis C virus genotypes in France: evidence in intravenous drug users

Hepatitis C virus (HCV) genotypes are distributed differently depending on geography and route of infection. We characterized the distribution of genotypes in a large cohort of patients with chronic hepatitis C in the South-east of France and evaluated the relative prevalence according to time of acquisition. One thousand, one hundred-and-eighty-three patients who were anti-HCV-positive were studied. HCV genotype distribution has changed significantly from the 1960s to 2000. The prevalence of genotype 1b decreased from 47% before 1978 to 18.8% in the 1990s while the prevalence of genotype 1a and 3a increased during the same period from 18% and 15.3% to 28.8% and 26.3%, respectively. The logistic regression model showed that genotype 1a was significantly more common in patients infected through intravenous drug injection odds ratio ((OR): 2.08, P < 0.01) and after 1990 (OR: 1.98, P < 0.05). Genotype 1b was significantly less frequent in patients infected through intravenous drug injection (OR: 0.17, P < 0.001) and has decreased since 1978 (OR: 0.27, P < 0.001). Genotype 3a was independently associated with intravenous drug injection (OR: 6.1, P < 0.001) and tattooing (OR: 8.01, P < 0.001) and was more frequent in the 1979-90 period (OR: 2.05 and 1.74, P < 0.001 and P < 0.05). Our results show a modification of HCV genotypes distribution over the last four decades due to an increase of intravenous drug use (IVDU) contamination and an evolution of HCV genotypes distribution only in IVDU population characterized by a decrease of genotype 1b, an increase of genotype 3a from 1970 to 1990 and a higher increase of genotype 1a which is currently the predominant genotype in our population.

Study of hydrophobic interactions between acylated proteins and phospholipid bilayers using BIACORE

Intracellular proteins of eukaryotic cells are frequently covalently modified by the addition of long chain fatty acids. These modifications are thought to allow otherwise soluble proteins to associate with membranes by lipid-lipid based hydrophobic interactions. The purpose of this work was to quantify the effect of acyl chain length on hydrophobic interactions between acylated proteins and phospholipid monolayers. The binding of an artificially acylated model protein to electrically neutral phospholipids was studied by surface plasmon resonance, using BIACORE. Kinetic rates for the binding of bovine pancreatic ribonuclease A (RNase A), monoacylated on its N-terminal lysine with fatty acids of 10, 12, 14, 16 or 18 carbon atoms, to phospholipids on hydrophobic sensor chips, were measured. Unlike unmodified ribonuclease, acylated RNase A bound to the phospholipids, and the association level increased with the acyl chain length to reach a maximum for C16. Reproducible kinetics were obtained which did not fit a 1:1 Langmuir model but rather a two-step binding profile.

Analysis of habituated embryogenic lines in Asparagus officinalis L.: growth characteristics, hormone content and ploidy level of calli and regenerated plants

Habituated asparagus embryogenic lines derived from eleven genotypes were maintained on hormone-free medium and grew actively through secondary embryogenesis. Secondary embryos were of single cell origin and emerged from the transversal division of some epidermal or subepidermal cotyledonary cells of primary embryos. The intensity of secondary embryogenesis was found to be variable between embryogenic lines. Plants regenerated from three of these lines have been previously demonstrated to carry a mutation whose phenotype was the direct appearance of somatic embryos on apices or nodes cultured on hormone-free medium. Habituated lines of embryogenic calli and various tissues of embryogenic mutant and wild type plants were analysed for their hormonal content in ABA, IAA, iP, Z and their metabolites ABA-GE, iPA, iMP, ZR. No significant difference was found between different embryogenic lines, except the level of iPA, or between cladophyll or apex cultures of mutant and wild type plants. Flow cytometry analyses indicated only 34% of the embryogenic lines were diploid, most of the others being tetraploid, but 62% of regenerated plants from these lines were diploid. This indicated the process of maturation and conversion selected diploid embryos in the embryogenic lines.

Direct transactivation of c-Ha-Ras gene by p53: evidence for its involvement in p53 transactivation activity and p53-mediated apoptosis

p53 protein is a sequence-specific transcriptional activator which induces the expression of a number of cellular genes involved in different metabolic pathways. We report that the computer-selected sequence in human and mouse C-Ha-Ras gene confers to a reporter gene the ability to be directly transactivated by wild-type p53 either overexpressed or activated in response to a cellular stress. By analysing human transformed cell lines, we showed, at both mRNA and protein level, that the endogenous c-Ha-Ras gene expression is positively regulated by wt p53 protein. The stimulation of c-Ha-Ras gene expression in Saos-2Ts cells by a temperature shift down to the permissive temperature for the p53-wt conformation is associated with a significant increase in the activated form of p21c-Ha-Ras protein. Furthermore, in human transformed cell lines, the transient expression of a dominant interfering mutant of c-Ha-Ras greatly reduced the ability of p53 to induce apoptosis and inhibited the p53-dependent transactivation. This is due, at least in part, to a decrease in the protein (but not mRNA) level of the transiently expressed p53, indicating that inactivation of p21c-Ha-Ras signalling pathways led to a specific degradation of p53 protein. We therefore suggest that, by inducing c-Ha-Ras, p53 activates a positive feedback loop that counteracts the negative feedback loop mediated by Mdm2.

Covert transmission of hepatitis C virus during bloody fisticuffs

Hepatitis C virus (HCV) is transmitted primarily through direct percutaneous exposure to infected blood. Sporadic HCV cases exist and may represent more than 10% of HCV transmission. We report the first case of documented transmission of HCV during a fight from a person who unknowingly had chronic HCV infection to a person who subsequently contracted acute hepatitis C. Patient-to-patient transmission was ascertained by sequence analysis of part of the NS5B genome and phylogenetic analysis. This case report suggests that sporadic HCV infection may be a result of blood exposure. This example of transmission could have a major impact in sports such as boxing or rugby. We suggest that in any fight, single use or nondisposable material should be used to dry blood to avoid such contamination.

Characterization and molecular basis of the oligomeric structure of HIV-1 nef protein

The Nef protein of human immunodeficiency virus type I (HIV-1) is an important determinant for the onset of AIDS disease. The self-association properties of HIV-1 Nef are analyzed by chemical cross-linking, dynamic light scattering, equilibrium analytical ultracentrifugation, and NMR spectroscopy. The experimental data show that the HIV-1 Nef core domain forms stable homo-dimers and trimers in solution, but not higher oligomers. These Nef homomers are not covalently linked by disulfide bridges, and the equilibrium between these forms is dependent on the Nef concentration. We further provide the molecular basis for the Nef core dimers and trimers obtained by analysis of crystallographic models. Oligomerization of biological polypeptides is a common tool used to trigger events in cellular signaling and endocytosis, both of which are targeted by Nef. The quaternary structure of Nef may be of physiological importance and may help to connect its cellular targets or to increase affinity of the viral molecule for its ligands. The herein described models for Nef dimers and trimers will allow further mutational studies to elucidate their role in vivo. These results provide novel insight into the structural and functional relationships of this important viral protein. Moreover, the oligomer interface may represent a novel target for the design of antiviral agents.

MOMP (major outer membrane protein) of Campylobacter jejuni; a versatile pore-forming protein

The great majority of trimeric porins of Gram-negative bacteria cannot be dissociated into monomers without disrupting their folded conformation. The porin of Campylobacter jejuni, however, displays two folded structures, a classical oligomer and a monomer resistant to detergent denaturation. We probed the transition of trimer to monomer using light scattering experiments and examined the secondary structures of these two molecular states by infra-red spectroscopy. The channel-forming properties of both trimer and monomer were studied after incorporation into artificial lipid bilayers. In these conditions, the trimer induced ion channels with a conductance value of 1200 pS in 1 M NaCl. The pores showed marked cationic selectivity and sensitivity to low voltage. Analysis of the isolated monomer showed nearly the same single-channel conductance and the same selectivity and sensitivity to voltage. These results indicate that the folded monomer form of C. jejuni MOMP displays essentially the same pore-forming properties as the native trimer.

Control of seed dormancy in Nicotiana plumbaginifolia: post-imbibition abscisic acid synthesis imposes dormancy maintenance

The physiological characteristics of seed dormancy in Nicotiana plumbaginifolia Viv. are described. The level of seed dormancy is defined by the delay in seed germination (i.e the time required prior to germination) under favourable environmental conditions. A wild-type line shows a clear primary dormancy, which is suppressed by afterripening, whereas an abscisic acid (ABA)-deficient mutant shows a non-dormant phenotype. We have investigated the role of ABA and gibberellic acid (GA(3)) in the control of dormancy maintenance or breakage during imbibition in suitable conditions. It was found that fluridone, a carotenoid biosynthesis inhibitor, is almost as efficient as GA(3) in breaking dormancy. Dry dormant seeds contained more ABA than dry afterripened seeds and, during early imbibition, there was an accumulation of ABA in dormant seeds, but not in afterripened seeds. In addition, fluridone and exogenous GA(3) inhibited the accumulation of ABA in imbibed dormant seeds. This reveals an important role for ABA synthesis in dormancy maintenance in imbibed seeds.

[Lyell syndrome and Stevens-Johnson syndrome caused by lamotrigine]

BACKGROUND

Lamotrigine is a new anticonvulsant belonging to the triazine family. Several cases of Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) have been described in patients taking this drug. We report 2 cases in children attending the same hospital.

CASE REPORTS

Two children, aged 9 and 13 years, developed SJS and TEN respectively, 3 and 28 days after lamotrigine was added to their usual anticonvulsant regimen. In both cases, outcome was favorable despite major decline in psychomotor capacity in one. In the first case, chronological attributability was plausible for lamotrigine and doubtful for sodium valproate, clonazepam and hydrocortisone. In the second case, chronological attributability was probable for amoxicillin, plausible for lamotrigine and doubtful for sodium valproate, but the numerous previous absorptions of amoxicillin made lamotrigine more suspect.

DISCUSSION

The risk of Steven-Johnson syndrome and toxic epidermal necrolysis is high with lamotrigine with an estimated frequency of 1/1000. This risk is probably higher than with other anticonvulsants. Associating lamotrigine with sodium valproate increases the frequency of adverse skin reactions.

Assessment of spontaneous fluctuations of viral load in untreated patients with chronic hepatitis C by two standardized quantitation methods: branched DNA and Amplicor Monitor

Quantitation of hepatitis C virus (HCV) RNA in serum has been used to predict and monitor the efficacy of interferon therapy in chronic HCV infection. We prospectively studied the fluctuation of viremia by a longitudinal follow-up of HCV RNA levels for 2 months in six untreated patients. Spontaneous fluctuations of HCV RNA ranged from 2.8- to 5.7-fold with branched DNA assay and from 2.9- to 5.6-fold with Monitor. These large spontaneous fluctuations (up to 0.75 log), observed daily, weekly, and monthly, raise doubt about the clinical value of a single assessment of pretherapeutic viremia.

HIV-1 Nef protein: purification, crystallizations, and preliminary X-ray diffraction studies

Human immunodeficiency virus Nef protein accelerates virulent progression of AIDS by its interaction with specific cellular proteins involved in cellular activation and signal transduction. Here we report the purification and crystallization of the conserved core of HIV-1LAI Nef protein in the unliganded form and in complex with the wild-type SH3 domain of the P59fyn protein-tyrosine kinase. One-dimensional NMR experiments show that full-length protein and truncated fragment corresponding to the product of HIV-1 protease cleavage have a well-folded compact tertiary structure. The ligand-free HIV-1 Nefcore protein forms cubic crystals belonging to space group P23 with unit cell dimensions of a = b = c = 86.4 A. The Nef-Fyn SH3 cocrystals belong to the space group P6(1)22 or its enantiomorph, P6(5)22, with unit cell dimensions of a = b = 108.2 A and c = 223.7 A. Both crystal forms diffract to a resolution limit of 3.0 A resolution using synchrotron radiation, and are thus suitable for X-ray structure determination.

ZEA3: A Negative Modulator of Cytokinin Responses in Plant Seedlings

In Nicotiana plumbaginifolia cytokinins affect seedling development by inhibiting root growth and hypocotyl elongation and by stimulating cotyledon expansion. The zea3.1 mutant was selected for its inability to grow in conditions of low nitrogen and for its ability to grow independently on inhibitory concentrations of zeatin (J.D. Faure, M. Jullien, M. Caboche [1994] Plant J 5: 481-491). The zea3.1 growth response to cytokinins is reflected by an increase in cotyledon expansion due to cell division and by a swelling of the hypocotyl due to cell enlargement. An analysis of the seedling's root length and fresh weight over a wide range of benzyladenine concentrations showed that zea3.1 plants exhibit a higher sensitivity and an amplified response to cytokinins. A similar response of zea3.1 to benzyladenine was also seen in the expression of msr1, a cytokinin-regulated gene. Regulation of msr1 expression by protein phosphorylation was unaffected by the zea3.1 mutation. No significant differences in cytokinin and auxin levels were found between zea3.1 and wild-type seedlings, suggesting that the mutant phenotype is not caused by an alteration of these hormone levels. The data presented suggest that ZEA3 negatively modulates cytokinin responses and may function as a broad regulator of seedling development.