Relapsed T-cell Acute Lymphoblastic Leukemia Research Articles

Autologous CD7 CAR-T cells generated without T cell pre-selection in pediatric patients with relapsed/refractory T-ALL: A phase I trial

Chimeric antigen receptor (CAR) T-cell therapy showed preliminary activity in patients with refractory or relapsed T-cell acute lymphoblastic leukemia (r/r T-ALL). However, many obstacles remain, including manufacturing difficulties and risk of infections. This phase I study (NCT04840875) evaluated autologous CD7 CAR T cells manufactured without pre-selection of healthy T cells in r/r T-ALL. Thirty patients (29 children and one adult) with a median of two lines of prior therapy but without detectable peripheral leukemia were enrolled. Excluding three cases of manufacturing failures, a total of 27 (90%) patients received infusions after products were confirmed free of leukemia contamination, including 16 (59%) meeting planned target doses. Common adverse events within 30 days included grade 3-4 cytopenias (100%), grade 1-2 (70%) and 3-4 (7%; including one dose-limiting toxicity) cytokine release syndrome, grade 1 neurotoxicity (7%), grade 2 infection (4%), and grade 2 graft-versus-host disease (4%). Two patients developed grade 2 infections after day 30. At day 30, 96% responded and 85% achieved CR or CRi. 74% underwent transplantation. Twelve-month progression-free survival with and without censoring transplantation was 22% (95%CI 4-100) and 57% (41-81), respectively. These results support that autologous CD7 CAR T-cell therapy without T-cell pre-selection is feasible in patients with r/r T-ALL.

A safety and efficacy study of allogeneic haematopoietic stem cell transplantation for refractory and relapsed T-cell acute lymphoblastic leukaemia/lymphoblastic lymphoma patients who achieved complete remission after autologous CD7 chimeric antigen receptor T-cell therapy.

CD7-targeted chimeric antigen receptor T-cell (CAR-T) therapy has shown promising initial complete remission (CR) rates in patients with refractory or relapsed (r/r) T-cell acute lymphoblastic leukaemia and lymphoblastic lymphoma (T-ALL/LBL). To enhance the remission duration, consolidation with allogeneic haematopoietic stem cell transplantation (allo-HSCT) is considered. Our study delved into the outcomes of 34 patients with r/r T-ALL/LBL who underwent allo-HSCT after achieving CR with autologous CD7 CAR-T therapy. These were compared with 124 consecutive T-ALL/LBL patients who received allo-HSCT in CR following chemotherapy. The study revealed that both the CAR-T and chemotherapy cohorts exhibited comparable 2-year overall survival (OS) (61.9% [95% CI, 44.1-78.1] vs. 67.6% [95% CI, 57.5-76.9], p = 0.210), leukaemia-free survival (LFS) (62.3% [95% CI, 44.6-78.4] vs. 62.0% [95% CI, 51.8-71.7], p = 0.548), non-relapse mortality (NRM) rates (32.0% [95% CI, 19.0-54.0] vs. 25.3% [95% CI, 17.9-35.8], p = 0.288) and relapse incidence rates (8.8% [95% CI, 3.0-26.0] vs. 15.8% [95% CI, 9.8-25.2], p = 0.557). Patients aged ≤14 in the CD7 CAR-T group achieved high 2-year OS and LFS rates of 87.5%. Our study indicates that CD7 CAR-T therapy followed by allo-HSCT is not only effective and safe for r/r T-ALL/LBL patients but also on par with the outcomes of those achieving CR through chemotherapy, without increasing NRM.

The CNS Microenvironment Promotes Leukemia Cell Survival By Disrupting Tumour Suppression and Cell Cycle Regulation in Pediatric T-Cell Acute Lymphoblastic Leukemia

Although modern treatment has improved the overall survival of pediatric T-cell acute lymphoblastic leukemia (T-ALL) greatly, more than 20% of all children diagnosed with T-ALL relapse (Fattizzo et al., 2020). Approximately 30% of all relapse cases occur in the central nervous system (CNS) and CNS involvement is considered a major risk factor for treatment failure and increased mortality (Frishman-Levy & Izraeli, 2017). To date, CNS directed therapy is considered essential for complete cure to prevent relapse in the CNS, leading to severe neurotoxic effects and long-term adverse complications (Thastrup et al., 2022). Due to lack of knowledge regarding the mechanisms promoting leukemia survival in the CNS and absence of reliable biomarkers to predict CNS involvement, the development of new therapeutic drugs able to eradicate leukemia cells in the CNS is not progressing, therefor limiting the overall survival of pediatric T-ALL patients (Thastrup et al., 2022). To identify genetic alterations in CNS involved T-ALL we performed an RNA-sequencing analysis coupled with a gene set enrichment analysis (GSEA) studying pediatric T-ALL patient samples obtained from the TARGET initiative. We included 30 samples from patients at initial diagnosis subdivided by degree of CNS involvement, ranging from CNS1 (no CNS disease) to CNS3 (advanced CNS disease), as well as 13 samples from patients who had relapsed in the CNS. Our analysis identified distinct genetic alterations in CNS involved T-ALL and CNS relapse compared to diagnosis samples without CNS implications, with dysregulation of genes involved in tumour suppression, apoptosis and self-renewal. CNS relapsed patients were distinguished from diagnosis patients by a distinct gene expression pattern, with an upregulation of many genes, including cell cycle inhibitor CDKN2A and transcription factor HOXA3 (Figure 1A). We also found disruption of many signaling pathways, including enrichment of the p53 pathway in patients who relapsed in the CNS compared to non-CNS involved diagnosis patients. To further study the effects of CNS implications in pediatric T-ALL, we established a co-culture of pediatric T-ALL cell lines (n=4) and a glioblastoma cell line (U87-MG). Following co-culture, changes to mRNA expression was evaluated by RT-qPCR, revealing dysregulation of many genes, including an upregulation of cancer stem cell marker and cell adhesion molecule CD44 (Chen et al., 2018). Moreover, T-ALL cells grown in CNS co-culture displayed a downregulation of tumour suppressor TP53 and an upregulation of its negative regulator, proto-oncogene MDM2 when compared to cells grown in suspension (Figure 1B) (Hernandez Borrero & El-Deiry, 2021). Co-culture also induced pro-survival isoform switching of BCL2L1 (BCLX), part of the BCL family of apoptotic regulators (Daniel et al., 2013). Together, these results suggest an increased survival and loss of tumour suppression of T-ALL cells when grown in direct contact with CNS derived cells. To determine effects of the CNS microenvironment on therapy resistance, T-ALL cell lines grown in co-culture were exposed to 2µM methotrexate, a chemotherapeutic agent used during CNS directed therapy (Thastrup et al., 2022). Leukemia cells in co-culture displayed an increased survival compared to cells grown in suspension following 48 hours of methotrexate exposure, as well as dysregulation of several genes involved in cell survival, self-renewal and cell cycle regulation. Cyclins and CDKs involved in controlling cell cycle progression were differentially expressed in co-culture versus suspension, with a downregulation of CDK2 and cyclin A, crucial for S/G2 transition, as well as CDK1 and cyclin B, responsible for G2/M transition (Leal-Esteban & Fajas, 2020). These results indicate a shift towards cell cycle arrest and senescence of T-ALL cells during methotrexate exposure in CNS co-culture, potentially promoting leukemia survival and chemoresistance. Taken together, our findings indicate a differential gene expression pattern in CNS involved T-ALL, which could potentially be utilized as predicative biomarkers to properly identify patients at risk of CNS relapse. CNS co-culture revealed cell cycle alterations and loss of proliferation markers, promoting senescence and therapy resistance, which could serve as potential therapeutic targets.

A Parallel Comparison of the Safety and Efficacy of Allogeneic Hematopoietic Stem Cell Transplantation for Refractory and Relapsed T-ALL/Lbl Patients Who Achieved Complete Remission with CD7 CAR-T Versus Patients Who Achieved First Complete Remission with Chemotherapy before Transplantation

Introduction We have developed a fratricide-resistant CD7 CAR-T cells from bulk T cells transduced with CD7 CAR without gene editing or additional gene transfer, named naturally selected CD7 CAR-T (NS7CAR-T). NS7 CAR-T therapy has shown a robust complete remission (CR) rate in patients with refractory or relapsed (R/R) T-cell acute lymphoblastic leukemia and T-cell lymphoblastic lymphoma (T-ALL/LBL). Nonetheless, the risk of relapse remains a challenge post-CD7 CAR-T therapy alone, suggesting the potential benefits of consolidation allogeneic hematopoietic stem cell transplantation (allo-HSCT). The question remains whether CD7 CAR-T therapy could increase the incidence of post-transplant complications. Here we conduct a parallel study to compare the safety and efficacy of allo-HSCT in R/R T-ALL/LBL patients who achieved CR with NS7 CAR-T therapy vs those who reached first CR (CR1) using chemotherapy prior to transplantation. Methods Between November 2020 and January 2023, a total of 223 consecutive patients with T-ALL/LBL who underwent allo-HSCT at our center were retrospectively analyzed. Patients who met the following criteria were included in this parallel study: 1) underwent the first allo-HSCT in our hospital, 2) achieved CR before transplantation either from NS7CAR-T therapy or CR1 from chemotherapy (Fig. 1). A total of 139 patients met the criteria for analysis and underwent allo-HSCT after achieving CR either from NS7CAR-T therapy (n=43) or chemotherapy (CR1=96). The median patient age at the time of transplantation was 15 years (range: 1-51 years). The median follow-up time was 370 days (2-941 days). CD7 CAR-T patients were from two clinical trials registered at www.clinicaltrials.gov NCT04572308, NCT04916860. Transplant donor types included sibling identical (n=12), haploidentical (n=110), and unrelated donors (n=17). We used total body irradiation (TBI)-based conditioning regimens (n=128) or Busulfan/Melphalan-based regimens (n=11). To prevent graft-versus-host disease (GVHD), we used ATG along with a short-term regimen combining methotrexate, cyclosporine/tacrolimus, and mycophenolate mofetil. Results The characteristics of patients from both groups are detailed in Table 1. The median interval between CD7 CAR-T treatment and transplantation was 59 (39-131) days. Within the CAR-T group, 16 patients had primary refractory disease, 18 had relapsed disease and 9 in minimal residual disease (MRD)-positive status in bone marrow before CD7 CAR-T therapy. Prior to CAR-T therapy, 55.8% (24 patients) had extramedullary lesions. In comparing the CAR-T and chemotherapy CR1 groups, we observed no significant differences in long-term efficacy post-allo-HSCT. The 2-year leukemia-free survival (LFS) rates were 64.9 (95% CI, 49.1-79.2)% and 69.8 (95% CI, 59.0-79.6)% (p=0.340); the 2-year overall survival (OS) rates were 64.1 (95%CI, 48.0-78.6)% and 71.8 (95%CI, 60.5-81.9)% (p=0.107); the 2-year relapse incidence (RI) rates were 9.3 (95%CI, 3.7-23.7)% and 11.5 (95%CI, 6.4-20.7)% (p=0.873); and the 2-year non-relapsed mortality (NRM) rates were 28.3 (95% CI, 16.9-47.4)% and 21.6 (95% CI, 13.9-33.4)% (p=0.244), for the CD7 CAR-T and non-CAR-T groups, respectively. The incidence of all grades of acute GVHD (aGVHD) 37.2 (95%CI, 25.2-54.9)% vs. 42.1 (95%CI, 33.3-53.3)% did not significantly differ between the CAR-T and non-CAR-T groups. A trend toward an increased rate but no P significance was observed in Grade 3-4 aGVHD incidence of 20.93 (95%CI, 11.7-37.4)% vs. 9.5 (95%CI, 5.1-17.6)% (p=0.139). One-year incidences of moderate to severe chronic GVHD (cGVHD) were 12.2 (95%CI, 5.4-28.0)% and 18.0 (95%CI, 11.5-28.0)% (p=0.357) in the CD7CAR-T and non-CAR-T groups, respectively (Table 2). No statistically significant differences were detected in the occurrences of transplant-associated thrombotic microangiopathy (TA-TMA), CMV, EBV, and HHV-6 infections between the two groups. Upon analyzing, we found that r/r patients who received allo-HSCT after achieving remission with NS7 CAR-T had a similar OS to CR1 patients (Fig. 2). Conclusions Our parallel study showed that T-ALL/LBL patients, who achieved CR via CD7 CAR-T therapy followed by a consolidation allo-HSCT, had similar favorable OS and LFS compared to patients who underwent allo-HSCT in the CR1 state induced by chemotherapy. This was achieved without increasing the incidence of GVHD, infections, or TA-TMA.

STAG2/LMO2 Gamma-Delta (γδ) T-ALL: Identification and Characterization of an Extremely High Risk Group of T-ALL in the Very Young

Background The prognosis of pediatric T-cell acute lymphoblastic leukemia (T-ALL) has improved with minimal residual disease (MRD)-stratified therapy, however, gamma delta T cell receptor positive (γδ) T-ALL remains a high-risk (HR) group. Limited studies have explored the clinical and genomic characteristics of γδ T-ALL, prompting us to conduct a comprehensive analysis of this entity and to identify determinants of outcome. Methods Through a consortium of 13 groups, we assembled a cohort of 200 patients up to 25 years of age with γδ T-ALL enrolled in clinical trials between 2000 and 2018. Clinical data of patients with non-γδ T-ALL enrolled on the same clinical trials were collected (n = 1,067). Complete remission (CR) was defined when bone marrow (BM) showed M1 cytomorphology and/or MRD <1% without evidence of extramedullary disease at end of induction/consolidation (EOI/EOC) and failure to achieve CR was considered treatment failure. A total of 76 γδ T-ALL samples were analyzed by whole genome (WGS) and/or transcriptome (RNAseq) sequencing. Results The frequency of γδ T-ALL was 8.0% of T-ALL cases. Patients with γδ T-ALL exhibited a higher rate of poor prednisone response ( P<0.01), MRD >1% at day 15 ( P<0.01), at EOI ( P<0.01) and EOC ( P<0.01), compared to non-γδ T-ALL cases. Furthermore, patients with γδ T-ALL showed significantly worse 5-year event free survival (EFS, 65% v. 78%, P<0.01) and overall survival (OS, 77% vs 83%, P=0.048). Almost all relapses of γδ T-ALL were isolated BM, while the central nervous system was the main site of relapse in non-γδ T-ALL, suggesting slow treatment response and chemo-resistance to the current treatment in γδ T-ALL. However, γδ T-ALL showed a higher rate of toxic death during treatment (7.6% vs 4.0%, P<0.01), suggesting the need for different therapeutic strategies and risk-classification, rather than treatment intensification. Strikingly, patients less than 3 years of age with γδ T-ALL exhibited significantly poor EFS (33% v. 70% [3-10 years] and 73% [>10], P<0.01) and OS (49% v. 78% [3-10] and 82% [>10], P< 0.01) ( Fig. A), a difference not observed in non-γδ T-ALL. MRD >1% at EOI showed poor EFS (51% v. 96% [MRD<0.01%] and 91% [1%>MRD>0.01%], P<0.01) and OS (66%). Integrated analysis of WGS and RNAseq identified enrichment of several genomic subtypes in γδ T-ALL, including STAG2/LMO2, hyperdiploidy with recurrent gains of chromosomes 8, 10, 11, 13q and 19, a recently identified “LMO2 γδ-like” subtype with distinct gene expression and LMO2/MYC/MYCN alterations, TLX3-rearranged (-R), and PICALM::MLLT10. No TAL1 nor TLX1-R were detected. STAG2/LMO2 was associated with age at diagnosis before 3 years, and extremely poor outcome, with 4 out of 5 cases dying within three years of diagnosis ( Fig. B). Of 24 STAG2/LMO2 T-ALL (additional 5 non-γδ, 13 TCR unknown cases), 22 of which were diagnosed by age three. All STAG2/LMO2 cases had alterations resulting in LMO2 activation and STAG2 inactivation, most commonly a single rearrangement between these two genes, and upregulation of HBE1, the LIN28-let7 pathway and stem cell proliferation pathways, suggesting a fetal hematopoietic origin. STAG2 has a critical role in the maintenance of enhancer-promoter looping mediated by the cohesin complex. To examine the consequences of STAG2 alterations, we performed integrated genomic/epigenomic analysis of the STAG2/LMO2 (MOLT-14 and PER-117) and STAG2 knockout (KO)/addback T-ALL lines. Chromatin loop sizes defined by H3K27ac HiChIP was highest in STAG2/LMO2 lines compared to other T-ALL. Following restoration of STAG2 expression in MOLT-14, CD34 and ID1/2 were down-regulated and H3K27ac was enriched in pathways related to T-cell differentiation. STAG2 KO in the non- STAG2/LMO2, LMO2-activated line PF382 identified genes also upregulated in STAG2/LMO2 primary samples, including CDK4 and STAG1. STAG2 KO lines exhibited partial compensation of STAG2 binding sites by STAG1 and upregulation of γδ-related genes, RORC and ID1/3. High throughput screening of 2,050 small molecules identified efficacy of HDAC, CDK and PARP inhibitors in STAG2/LMO2 lines. Conclusion Very young onset γδ T-ALL, but not non-γδ T-ALL, is enriched for the STAG2/LMO2 subtype and is a very high risk form of T-ALL. STAG2 loss perturbs chromatin organization and hematopoietic differentiation. Moreover, we demonstrate efficacy of novel therapeutic approaches that are needed to cure this form of leukemia.

Clonal Evolution Dissection Reveals High MSI2 Level Promotes Chemo-Resistance in T-Cell Acute Lymphoblastic Leukemia

Occurrences of T-cell acute lymphoblastic leukemia (T-ALL) arise in approximately 10-15% of pediatric ALL cases and the outcomes for high-risk T-ALL are inferior. Currently, the precise dissection of clonal evolution with intra-tumoral heterogeneity and to delineate targetable molecular events driving relapse in T-ALL subtypes have become area of interest. We carried out high-throughput droplet-based 5′-single-cell RNA-sequencing (scRNA-seq) and paired T-cell receptor sequencing (scTCR-seq) of isolated CD7 + BMMCs from five patients' Dx_Rel paired samples. To investigate the gene signature variation underlying leukemic progression, we observed two distinct patterns of evolutionary trajectories in the four Dx_Rel nonETP-ALL pairs. From T956 and T723, a significant outgrowth in TCR initially negligible diagnostic subclusters at relapse, to which surrogate TCR repertoires were correspondingly linked and enumerated, suggestive robust dominant “clonal shifts” under continuous chemotherapeutic pressure. Whereas in Dx_Rel pairs T593 and T856, which contained subclusters with distinct gene signatures at diagnosis or relapse respectively, shared an identical TCR genotype (TCR Dx-Rel major clone). The clonal architecture clues gained from simultaneous scRNA-seq and scTCR-seq are strongly indicative of the leukemic “clonal drift” that commonly occurs under chemotherapeutic stress, during which somehow, hypothetically, molecular signatures within the same TCR subclones intrinsically progressed over time ( Fig. A-H). Next, we designed a targeted scDNA-seq library within a custom panel covering 127 amplicons and 102 genes via Tapastri platform to validate these two patterns of clonal evolution during leukemia progression unambiguously. Likewise, we captured that in persisted subclones in T593 and T856 leukemic cells attained reproductive fitness from maintaining a mutational static status with remarkable transcriptomic variation from diagnosis to relapse. To further interpret the transcriptomic signature drift in the persisted TCR-defined major clones from T593 and T856 pairs, differential expression analysis was employed with RNA-binding protein Musashi-2 (MSI2) showing the most prominent differential expression pattern across drifted subclones catching our attention as a potential indicator of intrinsic clonal progression related to chemo-resistance. Comprehensive analysis of RNA-seq data from the CCCG-ALL-2015 cohort (n=72) and TARGET T-ALL cohort (n = 264) revealed that higher levels of MSI2 mRNA expression in pediatric T-ALL were correlated with higher measurable residual disease (MRD) after induction, and significant correlation between elevated MIS2 mRNA and resistance to prednisone, daunorubicin, and cytarabine were observed from ex vivo drug response assay. RNA immunoprecipitation and high-throughput mRNA sequencing from T-ALL cell lines detected a consistent significant enrichment of MYC transcript peaks in three T-ALL cell lines, indicating the molecular mechanism of MSI2 upregulation on MYC in the progression of T-ALL. Finally, In vitro and in vivo pharmacotyping analysis further validated the MSI2 inhibition significantly sensitized T-ALL to the chemotherapeutic drugs. Collectively, our study leveraging single-cell multi-omics profiling has provided a snapshot of the clonal architecture evolution that occurs from diagnosis to relapse in T-ALL, proving the coexistence of “clonal shift” and “clonal drift” in leukemic progression. Systemic analysis of drifted T-ALL clones has provided compelling evidence of the posttranscriptional regulatory effect of MSI2 on MYC and its potential correlation with leukemic reoccurrence, pinpointing MSI2 as a promising drug target of T-ALL in the future practice.

A Dual Role of SOX11 Expression in the Formation of T-Cell Acute Lymphoblastic Leukemia in Mouse Models

Introduction: T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that accounts for 10%-15% of pediatric and 25% of adult ALL cases. Intensified chemotherapy and bone marrow transplants have improved the survival of T-ALL patients. However, around 20% of patients still suffer from primary resistant or relapsed T-ALL. Therefore, improving our knowledge of T-ALL biology and developing precision oncology therapeutics is essential for further progress in T-ALL treatment. SRY-related HMG-box 11 (SOX11) is a transcription factor that regulates the development and survival of multiple embryonic tissues and is crucial for the nervous system. SOX11 is expressed in a multitude of tumor types, where it has been associated with either increased or decreased cell proliferation, metastatic potential, and with either good or bad prognosis, depending on cancer type. Despite being absent in the T-cell lineage, SOX11 is expressed in a subset of T-ALLs, where it plays an unknown role. Based on having a malignantly restricted expression, we hypothesize that SOX11 might be oncogenic in T-ALL. Aim: Identify the role of aberrant SOX11 expression in (pre)leukemic T-cells. Methods: Using a conditional Rosa26-SOX11 overexpression mouse model, we generated mice with T-cell specific (using Lck-cre) SOX11 expression (SOX11 Lck). To assess the self-renewal potential of SOX11 Lck thymocytes, we performed thymic transplantations on sublethally irradiated mice expressing a different allele of CD45. To study SOX11 in a leukemic context, we crossed the SOX11 Lck mice with two established T-ALL mouse models that are either driven by the overexpression of Lmo2 (SOX11 Lck-Lmo2 CD2) or by the loss of the tumor suppressor Pten (SOX11/Pten Lck). An aging cohort of these T-ALL models was followed, and tumor samples were collected. Thymi of 8-weeks old mice were used to study the impact of SOX11 in a pre-leukemic context, and T-cell tumors arising in these models were also used for RNA-sequencing. Using a retroviral strategy, we overexpressed SOX11 in human cord blood stem cells, which we differentiated towards the T-cell lineage ex vivo by co-culturing them on OP9 stromal cells expressing Delta-like Notch ligand 4. Furthermore, we transduced Jurkat cells with a SOX11 expression vector, or with an empty vector, and injected the cells into immunocompromised mice to assess the effect of SOX11 on tumor growth in vivo. Results: In SOX11 Lck mice, we found a significant increase in the immature double-negative 3 (DN3) thymic fraction, with a concomitant decrease in the amount of more mature double-positive CD4 +CD8 + (DP) thymocytes (Fig. A). A possible explanation for this phenotype would be the establishment of a stem-like self-renewal program similar to the one driven by Lmo2. However, by performing thymic transplantations into sublethally irradiated mice, we concluded that SOX11 does not confer self-renewal properties to thymocytes. Additionally, we aged a cohort of SOX11 Lck mice and did not observe formation of T-cell malignancies up to 500 days of age. Given that the expression of SOX11 does not suffice to produce T-cell tumors, we generated the SOX11 Lck-Lmo2 CD2 and SOX11/Pten Lck T-ALL mouse models. In SOX11 Lck-Lmo2 CD2 mice, we found a synergistic effect of the co-expression of both genes on the expansion of DN3 thymocytes (Fig. A), which led to accelerated leukemia formation (Fig. B). By sequencing the RNA of pre-leukemic and leukemic DN3 cells, we observed that SOX11 is mostly regulating cell adhesion, morphology, and cell-cell interactions to promote this oncogenic phenotype in Lmo2-driven T-ALL. On the other hand, SOX11/Pten Lck mice suffered from delayed leukemogenesis (Fig. B), and this tumor suppressor role might be associated with the decrease in DP cells observed in the pre-leukemic stage. Lastly, we set out to validate these findings in a human context. The ex vivo differentiation of human hematopoietic stem cells toward the T-cell lineage showed that SOX11 strongly accelerates early commitment to double-negative T-cell precursors. Also, we observed that Jurkat T-ALL cells engraft faster in immunocompromised mice when expressing SOX11. Conclusions: By generating multiple models of SOX11 expression in the T-cell lineage, we showed that SOX11 impacts T-cell differentiation, both in mice and humans, and that it can promote or hinder T-ALL formation depending on the oncogenic driver.

Malignant a-to-I RNA Editing By ADAR1 Drives T-Cell Acute Lymphoblastic Leukemia Relapse Via Attenuating dsRNA Sensing

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that frequently occurs in children, adolescents, and young adults. Approximately 10-20% of T-ALL patients will experience relapse months or years following remission and will often become refractory to further treatments. The survival of relapsed/refractory patients is very poor, with an overall survival rate of less than a 25% overall survival rate. Relapsed patients often have enriched pools of leukemia initiating cells (LICs) with enhanced pro-survival and self-renewal capacity, suggesting a potential vulnerable population for effective targeted therapies with less toxicity. An emerging research topic in LIC biology is the identification of RNA modifying enzymes that are important for LIC self-renewal and survival. ADAR1 enzymes catalyze the transition of adenosine (A) to inosine (I) in precursor double-stranded RNA (dsRNA). Epitranscriptomic A-to-I RNA editing events are widespread in the cancer transcriptome and are critical for the transition from pre-leukemic cells to fully functional LICs. Compared to myeloid leukemia, the role of ADAR1 in lymphoid progenitor maintenance and malignant transformation is not well understood . A-to-I RNA editing has a wide range of effects on RNA biology including gene expression, splicing, RNA degradation and translation, and miRNA biogenesis and/or 3' UTR targeting. The best documented functional roles of ADAR1 are suppression of the interferon (IFN) response and RNA editing of self-dsRNA to prevent abnormal activation of cytosolic self-dsRNA sensing. Concurrent deletion of the cytosolic dsRNA sensors melanoma differentiation-associated protein 5 (MDA5) and protein kinase R (PKR) is able to completely rescue embryo death and reverse the IFN signatures. Whether editing of immunogenic dsRNA and suppression of aberrant dsRNA sensing pathway could enhance LIC self-renewal capacities is an important question that has not been extensively addressed. In this study, we applied bioinformatic analysis on a large cohort of T-ALL samples to examine the function of ADAR1 in the context of T-ALL LIC maintenance. We found that ADAR1 is highly expressed in ~70% of all T-ALL patients and particularly within the LIC compartment. A thorough comparison of the A-to-I RNA editing landscape between non-relapsed and relapsed T-ALL patient cohorts revealed hyper-editing is associated with both increased risk of relapse and leukemia-associated mortality. A total of 338 under-edited and 1,472 over-edited sites were found in relapsed patients compared to non-relapsed samples. However, there was very little difference in ADAR1 expression and the overall A-to-I RNA editing levels, among various molecular subtypes of T-ALL, suggesting malignant A-to-I RNA editing is a common attribute of relapsed T-ALL regardless of the genetic mutation status. We also performed functional study in a three-dimensional human thymic organoid system and a T-ALL patient-derived xenograft (PDX) model. Depletion of ADAR1 showed striking effects in LIC survival and self-renewal with 50-90% reduction in leukemia growth. Mechanistically, we revealed complex dsRNA regulatory mechanisms of ADAR1 by directing hyper-editing of immunogenic dsRNA and retains unedited nuclear dsRNA to avoid detection by the innate immune sensor MDA5. Interesting, the dependency on ADAR1-MDA5 axis various among patients depending on the cell intrinsic level of MDA5. Collectively, our results show that ADAR1 functions as a self-renewal factor that limits the sensing of endogenous dsRNA. Thus, targeting ADAR1 presents a safe and effective therapeutic strategy for eliminating T-ALL LICs.

Idasanutlin and Navitoclax Induce a Synergistic p53-Dependent Apoptotic Cell Death in T-Cell Acute Lymphoblastic Leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy with a five-year event-free survival rate that declines with age. Existing therapies for T-ALL, particularly in adults, are intensive and poorly tolerated, with high rates of of treatment-related morbidity and mortality and a high frequency of relapse. In T-ALL, activating Notch pathway mutations are common and thought to induce transformation in part through activation of c-Myc. Typically, increased expression of c-Myc induces apoptosis through the p19(ARF)-Mdm2-p53 tumor suppressor pathway. Unsurprisingly, over 70% of T-ALL cases have inactivating mutations in CDKN2A (p19Arf). However, greater than 95% of primary and 75% of relapsed T-ALL cases maintain wild type p53. We hypothesized that MDM2 inhibition would lead to T-ALL cell apoptosis by bypassing the loss of ARF. We reported in a previous ASH abstract initial studies evaluating the MDM2 inhibitor idasanutlin in the context of T-ALL. We observed that T-ALL patient-derived xenograft (PDX) lines treated in vitro showed modest induction of apoptosis. Additionally, we observed upregulation of pro-apoptotic p53 target genes including Bax and Puma1, leading us to hypothesize that inhibition of pro-survival BH3 domain proteins Bcl-2, Bcl-xL, and Bcl-W by navitoclax (ABT-263) would synergize to enhance apoptosis. In vitro treatment of a panel of PDX lines with combined therapy led to robust cell death with strong induction of pro-apoptotic p53 targets in all lines. In vivo, we assessed the response of four T-ALL xenografts to dual treatment. All showed a significant reduction of tumor burden compared to the most efficacious single therapy and evidence of synergy in all tested lines, as evaluated by a modified Bliss Independence test analyzing average daily change in tumor burden. Overall survival was significantly increased in the combination treatment group. We report here further mechanistic characterization of idasanutlin and navitoclax dual therapy in the context of T-ALL, as well as several therapeutically-oriented comparisons. While our initial studies used navitoclax due to prior work showing that T-ALL frequently expresses and is dependent on Bcl-xL ( Chonghaile et al., 2014), navitoclax can cause a dose-limiting thrombocytopenia due to on-target Bcl-xL inhibition in circulating platelets. Therefore, we treated our PDX panel with a dose matrix of idasanutlin with navitoclax or venetoclax, which lacks Bcl-xL activity. We observed that the navitoclax combination showed strong evidence of synergic activity, as measured by zero interaction potency (ZIP) score ( Yadav et al., 2015). Idasanutlin and navitoclax combination therapy had global ZIP scores suggesting an additive effect in 1 line and strongly synergic activity in the remaining 4 lines. Venetoclax showed an additive benefit in 3 lines, but was only synergistic in 1 of 5 lines tested. These results underscore the importance of Bcl-xL targeting in T-ALL and support further investigation of whether combination treatment with idasanutlin permits a more tolerable navitoclax dosing regimen. We also evaluated ruxolitinib in combination with idasanutlin, as recent work has shown overlapping responses to inhibitors of Jak/Stat or Bcl-2 ( Yuan et al. 2022). While we observed moderate activity of ruxolitinib monotherapy, combination with idasanutlin was additive against one and synergistic in none of the tested lines. To confirm the p53-dependence of idasanutlin dual therapy, we engineered p53 knockout T-ALL cell lines and observed strong induction of apoptosis and p53 target genes in wildtype cells, which was entirely abrogated in p53 LOF lines. Additionally, we performed RNA-seq on PDX cells treated with single or dual therapy to mechanistically characterize transcriptional responses to the drug combination. We observed minimal changes in navitoclax-only treated cells at the RNA level, consistent with its on-target post-transcriptional regulation of apoptotic induction. Idasanutlin and combination therapy samples clustered closely in PCA analysis, with p53 response a strongly-induced pathway, as expected. Our data suggest that the rational combination of idasanutlin and navitoclax is highly active against T-ALL, with greater synergic opportunity compared to other available idasanutlin combination treatments, through induction of a p53-dependent apoptotic cell death.

The role of daratumumab in relapsed/refractory CD38 positive acute leukemias—case report on three cases with a literature review

Primary refractory or relapsed T-cell acute lymphoblastic leukemia (T-ALL) and mixed phenotype myeloid/T-cell acute leukemia have dismal prognoses. New treatment approaches, preferably targeting specific leukemic aberrations to overcome resistance, are urgently needed. The bright expression of the CD38 antigen found in several cases of T-ALL led to an investigation into the role of anti-CD38 antibodies in the treatment of T-ALL. Here, we present three cases of resistant and relapsed T-ALL and myeloid/T-cell treated with daratumumab-based therapy, including venetoclax and bortezomib (Dara-Ven-Bor). All patients achieved complete remission, with minimal residual disease negativity within four weeks of treatment, allowing them to proceed to allogeneic hematopoietic cell transplantation. The toxicity of the triple schema was acceptable. Our patients and other cases reviewed here suggest that daratumumab combined with venetoclax and bortezomib may be a very effective and relatively safe salvage treatment, even in primary resistant T-ALL.

Base-Edited CAR7 T Cells for Relapsed T-Cell Acute Lymphoblastic Leukemia

BackgroundCytidine deamination that is guided by clustered regularly interspaced short palindromic repeats (CRISPR) can mediate a highly precise conversion of one nucleotide into another — specifically, cytosine to thymine — without generating breaks in DNA. Thus, genes can be base-edited and rendered inactive without inducing translocations and other chromosomal aberrations. The use of this technique in patients with relapsed childhood T-cell leukemia is being investigated.MethodsWe used base editing to generate universal, off-the-shelf chimeric antigen receptor (CAR) T cells. Healthy volunteer donor T cells were transduced with the use of a lentivirus to express a CAR with specificity for CD7 (CAR7), a protein that is expressed in T-cell acute lymphoblastic leukemia (ALL). We then used base editing to inactivate three genes encoding CD52 and CD7 receptors and the β chain of the αβ T-cell receptor to evade lymphodepleting serotherapy, CAR7 T-cell fratricide, and graft-versus-host disease, respectively. We investigated the safety of these edited cells in three children with relapsed leukemia.ResultsThe first patient, a 13-year-old girl who had relapsed T-cell ALL after allogeneic stem-cell transplantation, had molecular remission within 28 days after infusion of a single dose of base-edited CAR7 (BE-CAR7). She then received a reduced-intensity (nonmyeloablative) allogeneic stem-cell transplant from her original donor, with successful immunologic reconstitution and ongoing leukemic remission. BE-CAR7 cells from the same bank showed potent activity in two other patients, and although fatal fungal complications developed in one patient, the other patient underwent allogeneic stem-cell transplantation while in remission. Serious adverse events included cytokine release syndrome, multilineage cytopenia, and opportunistic infections.ConclusionsThe interim results of this phase 1 study support further investigation of base-edited T cells for patients with relapsed leukemia and indicate the anticipated risks of immunotherapy-related complications. (Funded by the Medical Research Council and others; ISRCTN number, ISRCTN15323014.)

Long-term follow-up of donor-derived CD7 CAR T-cell therapy in patients with T-cell acute lymphoblastic leukemia

BackgroundDonor-derived CD7-directed chimeric antigen receptor (CAR) T cells showed feasibility and early efficacy in patients with refractory or relapsed T-cell acute lymphoblastic leukemia (r/r T-ALL), in a previous phase I trial report, at a median follow-up of 6.3 months. Here we report long-term safety and activity of the therapy after a 2-year follow-up.MethodsParticipants received CD7-directed CAR T cells derived from prior stem cell transplantation (SCT) donors or from HLA-matched new donors after lymphodepletion. The target dose was 1 × 106 (± 30%) CAR T cells per kg of patient weight. The primary endpoint was safety with efficacy secondary. This report focuses on the long-term follow-up and discusses them in the context of previously reported early outcomes.ResultsTwenty participants were enrolled and received infusion with CD7 CAR T cells. After a median follow-up time of 27.0 (range, 24.0–29.3) months, the overall response rate and complete response rate were 95% (19/20 patients) and 85% (17/20 patients), respectively, and 35% (7/20) of patients proceeded to SCT. Six patients experienced disease relapse with a median time-to-relapse of 6 (range, 4.0–10.9) months, and 4 of these 6 patients were found to have lost CD7 expression on tumor cells. Progression-free survival (PFS) and overall survival (OS) rates 24 months after treatment were respectively 36.8% (95% CI, 13.8–59.8%) and 42.3% (95% CI, 18.8–65.8%), with median PFS and OS of respectively 11.0 (95% CI, 6.7–12.5) months and 18.3 (95% CI, 12.5–20.8) months. Previously reported short-term adverse events (< 30 days after treatment) included grade 3–4 cytokine release syndrome (CRS; 10%) and grade 1–2 graft-versus-host disease (GVHD; 60%). Serious adverse events reported > 30 days after treatment included five infections and one grade 4 intestinal GVHD. Despite good CD7 CAR T-cell persistence, non-CAR T and natural killer cells were predominantly CD7-negative and eventually returned to normal levels in about half of the participants.ConclusionsIn this 2-year follow-up analysis, donor-derived CD7 CAR T-cell treatment demonstrated durable efficacy in a subset of patients with r/r T-ALL. Disease relapse was the main cause of treatment failure, and severe infection was a noteworthy late-onset adverse event.Trial registrationChiCTR2000034762.

STAT5 activation promotes progression and chemotherapy resistance in early T-cell precursor acute lymphoblastic leukemia

AbstractInterleukin-7 (IL-7) supports the growth and chemoresistance of T-cell acute lymphoblastic leukemia (T-ALL), particularly the early T-cell precursor subtype (ETP-ALL), which frequently has activating mutations of IL-7 signaling. Signal transducer and activator of transcription (STAT5) is an attractive therapeutic target because it is almost universally activated in ETP-ALL, even in the absence of mutations of upstream activators such as the IL-7 receptor (IL-7R), Janus kinase, and Fms-like tyrosine kinase 3 (FLT3). To examine the role of activated STAT5 in ETP-ALL, we have used a Lmo2-transgenic (Lmo2Tg) mouse model in which we can monitor chemoresistant preleukemia stem cells (pre-LSCs) and leukemia stem cells (LSCs) that drive T-ALL development and relapse following chemotherapy. Using IL-7R-deficient Lmo2Tg mice, we show that IL-7 signaling was not required for the formation of pre-LSCs but essential for their expansion and clonal evolution into LSCs to generate T-ALL. Activated STAT5B was sufficient for the development of T-ALL in IL-7R-deficient Lmo2Tg mice, indicating that inhibition of STAT5 is required to block the supportive signals provided by IL-7. To further understand the role of activated STAT5 in LSCs of ETP-ALL, we developed a new transgenic mouse that enables T-cell specific and doxycycline-inducible expression of the constitutively activated STAT5B1∗6 mutant. Expression of STAT5B1∗6 in T cells had no effect alone but promoted expansion and chemoresistance of LSCs in Lmo2Tg mice. Pharmacologic inhibition of STAT5 with pimozide-induced differentiation and loss of LSCs, while enhancing response to chemotherapy. Furthermore, pimozide significantly reduced leukemia burden in vivo and overcame chemoresistance of patient-derived ETP-ALL xenografts. Overall, our results demonstrate that STAT5 is an attractive therapeutic target for eradicating LSCs in ETP-ALL.

T cell functions and organ infiltration by leukemic T cells require cortactin.

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that is still fatal in many cases. T cell blasts are characterized by hyperactivation and strong proliferative and migratory capacities. The chemokine receptor CXCR4 is involved in mediating malignant T cell properties, and cortactin has been shown to control CXCR4 surface localization in T-ALL cells. We have previously shown that cortactin overexpression is correlated with organ infiltration and relapse in B-ALL. However, the role of cortactin in T cell biology and T-ALL remains elusive. Here, we analyzed the functional relevance of cortactin for T cell activation and migration and the implications for T-ALL development. We found that cortactin is upregulated in response to T cell receptor engagement and recruited to the immune synapse in normal T cells. Loss of cortactin caused reduced IL-2 production and proliferation. Cortactin-depleted T cells showed defects in immune synapse formation and migrated less due to impaired actin polymerization in response to T cell receptor and CXCR4 stimulation. Leukemic T cells expressed much higher levels of cortactin compared to normal T cells that correlated with greater migratory capacity. Xenotransplantation assays in NSG mice revealed that cortactin-depleted human leukemic T cells colonized the bone marrow significantly less and failed to infiltrate the central nervous system, suggesting that cortactin overexpression drives organ infiltration, which is a major complication of T-ALL relapse. Thus, cortactin could serve as a potential therapeutic target for T-ALL and other pathologies involving aberrant T cell responses.

Comprehensive Genome Characterization of Childhood T-ALL Links Oncogene Activation Mechanism and Subtypes to Prognosis

Background: Children with relapsed T-cell acute lymphoblastic leukemia (T-ALL) have poor prognosis, and identification of patients at risk for recurrence is required to prevent relapse. Prior genomic studies of T-ALL have failed to identify genetic alterations that are prognostic independent of minimal residual disease (MRD), in part due to limited cohort size, exclusion of patients with refractory disease, and lack of comprehensive, integrated genome and transcriptome sequencing, which is important as many T-ALL drivers occur in non-coding regions of the genome. Aim: To identify all coding and non-coding alterations and identify genomic predictors of relapse or refractory disease. Methods: We performed whole genome, exome, and transcriptome sequencing of 1,313 cases enrolled on the Children's Oncology Group AALL0434 trial of childhood T-ALL. ATAC-seq and HiChIP were used to investigate the consequences of non-coding mutations and structural variants (SV). We used transcriptome profiling by Uniform Manifold Approximation and Projection (UMAP), Leiden algorithm clustering, hierarchical clustering of oncogene expression, and analysis of sequence and structural DNA variants to identify subtypes of T-ALL cases, their driver and associated genomic alterations. Results: Using integrative genomic analysis, we identified the clonal subtype-defining putative drivers in 94% of samples, 60% of which were non-coding regions and required WGS for identification in 28% of cases. We identified 16 T-ALL subtypes, several of which were previously unrecognized and involved partitioning of known subgroups into groups with distinct gene expression and driver alterations. We identified 4 subtypes with deregulation of the TAL1/LMO1/LMO2 core transcriptional circuitry: TAL1-RA, TAL1-RB, TAL1-RB/RPL10, LMO2-refractory (15.5%, 20.4%, 2.8%, 0.9% of all cases). These subtypes were separated by the lower expression of T cell maturation genes CD4/CD8 and RAG in TAL1-RA and more mature double positive TAL1-RB. TAL1-RA was characterized by multiple activation mechanisms for TAL1, LMO1 and/or LMO2; and TAL1-RB with alterations of TAL1, LMO1, LMO2,LYL1 and, TAL2 including rearrangements of these genes to TCR enhancers, chimeric fusion oncoproteins and a diverse range of enhancer hijacking, amplification and SNV events. Activation mechanisms differed between the groups; TAL1-RA commonly had STIL::TAL1 fusion with frequently co-occurring LMO2/LMO1 SNV/Indels or LMO2 enhancer gains, whereas TAL1-RB had frequent TAL1/LMO2/TAL2/LYL1 TCR rearrangements, TAL1 enhancer gains or various other TAL1 rearrangements. Two additional subgroups included 39 cases with TAL1/LMO2 activation and RPL10 mutations (TAL1-RB/RPL10) and the other characterized by refractory disease (LMO2-refractory, day 29 MRD >5%, 8 cases) with deregulation of LMO2 by hijacking of the BCL11B enhancer. We observed striking association between early T-cell precursor phenotype and driver lesions, with several groups highly enriched for ETP-ALL cases. One group (11.5% of all cases, 41.9% of ETP ALL cases, Fig. 1A) had distinct gene expression and deregulation of HOXA13 by SVs, ZFP36L2 or ETV6 by chimeric fusions and MED12 by SNVs. A second group (7.3% cases, 30.4% ETP) had HOXA9 deregulation by HOXA9 SVs or NUP98/NUP214/KMT2/MLLT10 chimeric fusions. Selective HOXA13 deregulation could be explained by genomic breakpoints occurring in different chromatin compartments than rearrangements deregulating other HOXA genes such as HOXA9. Novel HOXA13 SVs include rearrangements to MIR181A1HG and MED13 loci. Event-free survival (EFS) varied by subtype (Fig1B. log rank P<0.0001). Adverse risk subtypes were SPI1-R (P<0.0001, subtype vs. rest of samples), HOXA9 (P<0.0001), LMO2-refractory (P<0.0001) and favorable risk TAL1-RB/RPL10 (P=0.046), NKX2-1 (P=0.0099), TLX1 (P=0.013), TLX3 (P=0.028) and KMT2A-R (P=0.003) subtypes (Fig. 1B). Outcome was associated with key oncogenic pathways: for example, absence of Notch pathway alterations was associated with poor outcome if D29 MRD≥0.01% (5-year EFS <75%), whereas, patients with Notch alterations had good outcome regardless of Day 29 MRD. Conclusion: Comprehensive definition of the genomic landscape of T-ALL requires integrated WGS and RNAseq, and identifies multiple subgroups and driver lesions associated with immunophenotype and outcome. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Highlights from Recent Cancer Literature

Highlights from Recent Cancer Literature

Nelarabine, etoposide, and cyclophosphamide in relapsed pediatric T-acute lymphoblastic leukemia and T-lymphoblastic lymphoma (study T2008-002 NECTAR).

Children with relapse of T-cell acute lymphoblastic leukemia (T-ALL) or lymphoblastic lymphoma (T-LBL) have a dismal prognosis, largely due to difficulty attaining second remission. We hypothesized that adding etoposide and cyclophosphamide to the nucleoside analog nelarabine could improve response rates over single-agent nelarabine for relapsed T-ALL and T-LBL. This phase I dose-escalation trial's primary objective was to evaluate the dose and safety of nelarabine given in combination with etoposide at 100mg/m2 /day and cyclophosphamide at 330-400mg/m2 /day, each for 5 consecutive days in children with either T-ALL (13 patients) or T-LBL (10 patients). Twenty-three patients were treated at three dose levels; 21 were evaluable for dose-limiting toxicities (DLT) and response. The recommended phase II doses (RP2D) for this regimen, when given daily ×5 every 3weeks, were nelarabine 650mg/m2 /day, etoposide 100mg/m2 /day, and cyclophosphamide 400mg/m2 /day. DLTs included peripheral motor and sensory neuropathies. An expansion cohort to evaluate responses at the RP2D was terminated early due to slow accrual. The overall best response rate was 38% (8/21), with 33% (4/12) responses in the T-ALL cohort and 44% (4/9) responses in the T-LBL cohort. These response rates are comparable to those seen with single-agent nelarabine in this setting. These data suggest that the addition of cyclophosphamide and etoposide to nelarabine does not increase the incidence of neurologic toxicities or the response rate beyond that obtained with single-agent nelarabine in children with first relapse of T-ALL and T-LBL.

Nelarabine-induced rhabdomyolysis in a patient with T-cell acute lymphoblastic leukemia: a case report

BackgroundNelarabine is an antineoplastic purine analog used for the treatment of refractory or relapsed T-cell acute lymphoblastic leukemia (T-ALL). The most prominent side effect of nelarabine are neurotoxicity and hematologic disorder, which are considered dose-limiting factors. Although clinical studies have reported myopathy due to nelarabine, actual detailed outcomes were not well-known initial approval. The incidence of nelarabine induced rhabdomyolysis has been reported at 2% in study in children. Cases of rhabdomyolysis have been reported in adults from medical facilities in the United Sates with renal dysfunction or severe muscle symptoms after administration of multiple courses of nelarabine. In this report, we discuss a case of rhabdomyolysis diagnosed after a single course of nelarabine. In this case, creatine kinase (CK) level was elevated in grade 4, without renal dysfunction and severe muscle symptoms.Case presentationA 46-year-old man from Japan was diagnosed with T-ALL and received a hematopoietic stem cell transplantation in first remission. However, the disease relapsed 6 months after transplantation. Nelarabine was selected as the next-line chemotherapeutic agent. The patient received 1500 mg/m2 of nelarabine on day 1 followed by a dose on days 3 and 5. CK levels, which were baseline before treatment, increased to grade 4 (18,620 IU/L) on the 8th day of treatment. He was diagnosed as rhabdomyolysis due to nelarabine with little possibility of other factors. He complained only of mild pain in his upper extremities and no other symptoms were noticed. The patient was managed with hydration. The pain lasted approximately 7 days, but there were no sequelae secondary to the rhabdomyolysis. Because of the elevation of CK in grade 4, we avoided re-administration.ConclusionIn the patient administrated nelarabine, CK level was elevated in grade 4, without other symptoms of rhabdomyolysis. The results suggest that CK may be elevated at the onset of rhabdomyolysis caused by nelarabine, even in the absence of other symptoms. Therefore, it was suggested that monitoring CK during nelarabine administration is important for detecting rhabdomyolysis before it becomes severe. We consider that CK should be monitored even in absence of symptoms.

Impact of KIR-ligand mismatch on pediatric T-cell acute lymphoblastic leukemia in unrelated cord blood transplantation

Currently, allogeneic hematopoietic stem cell transplantation (allo-HSCT) is considered to be indicated for children and adolescents with high-risk or relapsed T-cell acute lymphoblastic leukemia (T-ALL); however, the outcomes are unsatisfactory. Killer cell immunoglobulin-like receptors (KIRs) are the main receptors on natural killer (NK) cells that play an important role in the graft-versus-leukemia effect after allo-HSCT. In allo-HSCT, when the recipient lacks a donor KIR-ligand (KIR-ligand mismatch in the graft-versus-host [GVH] direction), donor NK cells will be activated against recipient cells. KIR-ligand mismatch in the GVH direction improves outcomes after unrelated cord blood transplantation (UCBT) with acute myeloid leukemia, but the effect in T-ALL is unclear. We evaluated the impact of KIR-ligand mismatch in the GVH direction on the transplantation outcomes of children and adolescents with T-ALL who received UCBT. We conducted a retrospective study using a nationwide registry of the Japanese Society for Transplantation and Cellular Therapy. Patients diagnosed with T-ALL, aged 0 to 19 years, and who underwent first UCBT between 1999 and 2017 were included. A total of 91 patients were included in this study. In all, 23 (25.3%) percent of patients had KIR-ligand mismatch in the GVH direction. The 5-year leukemia-free survival (LFS) and overall survival (OS) rates after UCBT were 65.8% and 69.6%, respectively. In a multivariate analysis, KIR-ligand mismatch in the GVH direction was associated with a significant reduction in the relapse rate (hazard ratio [HR], 0.19; P = .002), resulting in better LFS (HR, 0.18; P =.010) and OS (HR, 0.26; P = .048) without increasing non-relapse mortality (NRM; HR, 1.90; P = .264). The cumulative incidence of GVH disease (GVHD) did not differ between patients with and without KIR-ligand mismatch (grade II-IV acute GVHD, 39.1% versus 36.8%, P = .648, grade III-IV acute GVHD, 13.0% versus 11.8%, P =.857, and chronic GVHD, 26.1% versus 22.9%, P =.736, respectively). Furthermore, acute and chronic GVHD were not associated with good patient outcomes. Notably, no relapse was observed in patients who received KIR-ligand mismatched UCBT in complete remission. KIR-ligand mismatch in the GVH direction improved LFS and decreased relapse rates without increasing NRM in children and adolescents with T-ALL who received UCBT, which was not mediated by GVHD.

Central nervous system neurotoxicity associated with nelarabine in T-cell acute lymphoblastic leukemia.

Nelarabine, a prodrug of arabinosylguanine has lineage-specific toxicity for T lymphoblasts and is used to treat refractory or relapsed T-cell acute lymphoblastic leukemia and T-cell lymphoblastic lymphoma patients. The most commonly observed adverse effects associated with nelarabine are mainly hematological, i.e. neutropenia, anemia, and thrombocytopenia. Additionally, neurological, and gastrointestinal toxicities have been reported. Central nervous system neurotoxicity associated with nelarabine is very rare. A 37-year-old man patient diagnosed with T-cell acute lymphoblastic leukemia had experienced generalized tonic-clonic seizure which lasted for a few seconds and upper extremity weakness after three weeks of the nelarabine infusion. Computed tomography and magnetic resonance imaging have shown periventricular and nucleus caudatus abnormalities. Radiological findings suggested toxic leukoencephalopathy and acute infarct of right nucleus caudatus. After high-dose steroids, intravenous immunoglobulin, and support treatment, his neurologic symptoms disappeared except for mild peroral numbness. However, radiological sequelae persisted despite clinical improvement. Physicians involved in the care of these patients who use nelarabine should be aware of the fact that cerebral toxicity of the nelarabine may occur especially in the presence of predisposing factors. It is crucial to monitor closely those patients receiving nelarabine and also those who have additional predisposing factors for neurotoxicity.