Relapsed T Cell ALL: Current Approaches and New Directions

T-cell acute lymphoblastic leukemia progression is supported by inflammatory molecules including hepatocyte growth factor

T-cell acute lymphoblastic leukemia (T-ALL) is a malignant hematological disorder characterized by an increased proliferation of immature T lymphocytes precursors. T-ALL treatment includes chemotherapy with strong side effects, and patients that undergo relapse display poor prognosis. Although cell-intrinsic oncogenic pathways are well-studied, the tumor microenvironment, like inflammatory cellular and molecular components is less explored in T-ALL. We sought to determine the composition of the inflammatory microenvironment induced by T-ALL, and its role in T-ALL progression. We show in two mouse T-ALL cell models that T-ALLs enhance blood neutrophils and resident monocytes, accompanied with a plasmatic acute secretion of inflammatory molecules. Depleting neutrophils using anti-Ly6G treatment or resident monocytes by clodronate liposomes treatment does not modulate plasmatic inflammatory molecule secretion and mice survival. However, inhibiting the secretion of inflammatory molecules by microenvironment with NECA, an agonist of adenosine receptors, diminishes T-ALL progression enhancing mouse survival. We uncovered Hepatocyte Growth Factor (HGF), T-ALL-driven and the most decreased molecule with NECA, as a potential therapeutic target in T-ALL. Altogether, we identified a signature of inflammatory molecules that can potentially be involved in T-ALL evolution and uncovered HGF/cMET pathway as important to target for limiting T-ALL progression.

Notch3-regulated microRNAs impair CXCR4-dependent maturation of thymocytes allowing maintenance and progression of T-ALL

Malignant transformation of T-cell progenitors causes T-cell acute lymphoblastic leukemia (T-ALL), an aggressive childhood lymphoproliferative disorder. Activating mutations of Notch, Notch1 and Notch3, have been detected in T-ALL patients. In this study, we aimed to deeply characterize hyperactive Notch3-related pathways involved in T-cell dynamics within the thymus and bone marrow to propose these processes as an important step in facilitating the progression of T-ALL. We previously generated a transgenic T-ALL mouse model (N3-ICtg) demonstrating that aberrant Notch3 signaling affects early thymocyte maturation programs and leads to bone marrow infiltration by CD4+CD8+ (DP) T cells that are notably, Notch3highCXCR4high. Newly, our in vivo results suggest that an anomalous immature thymocyte subpopulation, such as CD4-CD8- (DN) over-expressing CD3ɛ, but with low CXCR4 expression, dominates N3-ICtg thymus-resident DN subset in T-ALL progression. MicroRNAs might be of significance in T-ALL pathobiology, however, whether required for leukemia maintenance is not fully understood. The selection of specific DN subsets demonstrates the inverse correlation between CXCR4 expression and a panel of Notch3-deregulated miRNAs. Interestingly, we found that within DN thymocyte subset hyperactive Notch3 inhibits CXCR4 expression through the cooperative effects of miR-139-5p and miR-150-5p, thus impinging on thymocyte differentiation with accumulation of DNCD3ɛ+CXCR4- cells. These data point out that deregulation of Notch3 in T-ALL, besides its role in sustaining dissemination of abnormal DP T cells, as we previously demonstrated, could play a role in selecting specific DN immature T cells within the thymus, thus impeding T cell development, to facilitate T-ALL progression inside the bone marrow.

Chidamide combined with a modified Bu-Cy conditioning regimen improves survival in patients with T-cell acute lymphoblastic leukemia/lymphoma undergoing allogeneic hematopoietic stem cell transplantation

This study aimed to evaluate the efficacy and safety of chidamide (Chi) combined with a modified Busulfan-Cyclophosphamide (mBuCy) conditioning regimen for T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). Twenty-two patients received chidamide combined with mBuCy conditioning regimen (Chi group). A matched-pair control (CON) group of 44 patients (matched 1:2) received mBuCy only in the same period. The leukemia-free survival (LFS), overall survival (OS), cumulative incidence of relapse (CIR), and non-relapse-related mortality (NRM) were evaluated. Patients in the Chi group were associated with lower 2-year CIR (19.0 vs. 41.4%, P = 0.030), better 2-year LFS (76.1 vs. 48.1%, P = 0.014), and had no significant difference in 2-year OS (80.5 vs. 66.4%, P = 0.088). Patients with minimal residual disease (MRD) positive before HSCT in the Chi group exhibited an advantage in 2-year LFS and a trend towards better 2-year OS (75.0 vs. 10.2%, P = 0.048; 75.0 vs. 11.4%, P = 0.060, respectively). Multivariable analysis showed that the chidamide intensified regimen was independently associated with better LFS (HR 0.23; 95%CI, 0.08-0.63; P = 0.004), and showed no significant impact with OS for all patients (HR 0.34, 95%CI, 0.11-1.07; P = 0.064). The cumulative incidence rates of grade II-IV aGVHD were similar (36.4 vs. 38.6%, P = 0.858). 20 patients in Chi group evinced an elevation in γ-glutamyltransferase, as compared to the mBuCy group (90.9 vs. 65.9%, P = 0.029). No transplantation-related mortality was documented within the first 100 days after transplantation. The results demonstrate that the chidamide intensified regimen may be an effective and acceptable safety option for T-ALL/LBL undergoing allo-HSCT, and further validation is needed.

4'-Ethynyl-2'-Deoxycytidine (EdC) Preferentially Targets Lymphoma and Leukemia Subtypes by Inducing Replicative Stress

Anticancer nucleosides are effective against solid tumors and hematologic malignancies, but typically are prone to nucleoside metabolism resistance mechanisms. Using a nucleoside-specific multiplexed high-throughput screening approach, we discovered 4'-ethynyl-2'-deoxycytidine (EdC) as a third-generation anticancer nucleoside prodrug with preferential activity against diffuse large B-cell lymphoma (DLBCL) and acute lymphoblastic leukemia (ALL). EdC requires deoxycytidine kinase (DCK) phosphorylation for its activity and induces replication fork arrest and accumulation of cells in S-phase, indicating it acts as a chain terminator. A 2.1Å cocrystal structure of DCK bound to EdC and UDP reveals how the rigid 4'-alkyne of EdC fits within the active site of DCK. Remarkably, EdC was resistant to cytidine deamination and SAMHD1 metabolism mechanisms and exhibited higher potency against ALL compared with FDA-approved nelarabine. Finally, EdC was highly effective against DLBCL tumors and B-ALL in vivo. These data characterize EdC as a preclinical nucleoside prodrug candidate for DLBCL and ALL.

CD7 CAR T bridging to allo-HSCT in R/R T-ALL: A case report

BACKGROUND

Refractory/relapsed T-cell acute lymphoblastic leukemia (R/R T-ALL) is a hematological malignancy with a poor prognosis. The current treatment strategy has not benefited most patients, and the treatment methods are still being explored.

CASE PRESENTATION

An 8-year-old boy with R/R T-ALL achieved CR after multiple chemotherapies, followed by the first allo-HSCT. Unfortunately, 1 year and 3 months later, he relapsed. After recurrence, the patient underwent multiple chemotherapies, but the NOTCH1 gene and MRD were still positive. FCM and immunohistochemistry revealed abnormally high expression of CD7, so we considered bridging the second allo-HSCT after CD7 CAR T-cells treatment. The patient has low toxic and side effects and is still in CR, findings from this case report have more important therapeutic significance for R/R T-ALL.

CONCLUSION

In conclusion, CD7 CAR T-cells bridging to allo-HSCT is a safe and effective approach for R/R T-ALL, resulting in durable CR and longer survival.

Case report: Preventive infusion of donor-derived CD7 chimeric antigen receptor T cells after allogeneic hematopoietic stem cell transplantation

Chimeric antigen receptor T cells (CAR T) targeting CD7 for T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) showed promising efficacy and safety in some clinical trials. However, most of them were bridged with allogeneic hematopoietic stem cell transplantation (allo-HSCT). We described successful treatment with preventive donor-derived anti-CD7 CAR-T therapy in a case of refractory T lymphoblastic lymphoma following allo-HSCT, who could not receive autologous anti-CD7 CAR-T products due to the low-quality of T lymphocytes. To date, the patient's complete remission has persisted for 20 months after HSCT.

Malignant A-to-I RNA editing by ADAR1 drives T cell acute lymphoblastic leukemia relapse via attenuating dsRNA sensing

Leukemia-initiating cells (LICs) are regarded as the origin of leukemia relapse and therapeutic resistance. Identifying direct stemness determinants that fuel LIC self-renewal is critical for developing targeted approaches. Here, we show that the RNA-editing enzyme ADAR1 is a crucial stemness factor that promotes LIC self-renewal by attenuating aberrant double-stranded RNA (dsRNA) sensing. Elevated adenosine-to-inosine editing is a common attribute of relapsed T cell acute lymphoblastic leukemia (T-ALL) regardless of molecular subtype. Consequently, knockdown of ADAR1 severely inhibits LIC self-renewal capacity and prolongs survival in T-ALL patient-derived xenograft models. Mechanistically, ADAR1 directs hyper-editing of immunogenic dsRNA to avoid detection by the innate immune sensor melanoma differentiation-associated protein 5 (MDA5). Moreover, we uncover that the cell-intrinsic level of MDA5 dictates the dependency on the ADAR1-MDA5 axis in T-ALL. Collectively, our results show that ADAR1 functions as a self-renewal factor that limits the sensing of endogenous dsRNA. Thus, targeting ADAR1 presents an effective therapeutic strategy for eliminating T-ALL LICs.

Inhibition of γ-secretase/Notch pathway as a potential therapy for reversing cancer drug resistance

The mechanism of tumor drug resistance is complex and may involve stem cell maintenance, epithelial-mesenchymal transition, the activation of survival signaling pathways, transporter protein expression, and tumor microenvironment remodeling, all of which are linked to γ-secretase/Notch signaling. Increasing evidence has shown that the activation of the γ-secretase/Notch pathway is a key driver of cancer progression and drug resistance development and that γ-secretase inhibitors (GSIs) may be the most promising agents for reversing chemotherapy resistance of tumors by targeting the γ-secretase/Notch pathway. Here, we systematically summarize the roles in supporting γ-secretase/Notch activation-associated transformation of cancer cells into cancer stem cells, promotion of the EMT process, PI3K/Akt, MEK/ERK and NF-κB activation, enhancement of ABC transporter protein expression, and TME alteration in mediating tumor drug resistance. Subsequently, we analyze the mechanism of GSIs targeting the γ-secretase/Notch pathway to reverse tumor drug resistance and propose the outstanding advantages of GSIs in treating breast cancer drug resistance over other tumors. Finally, we emphasize that the development of GSIs for reversing tumor drug resistance is promising.

Nelarabine: when and how to use in the treatment of T-cell acute lymphoblastic leukemia

ABSTRACT

T-cell acute lymphoblastic leukemia or lymphoblastic lymphoma (T-ALL/LBL) is a rare hematologic malignancy most commonly affecting adolescent and young adult males. Outcomes are dismal for patients who relapse, thus, improvement in treatment is needed. Nelarabine, a prodrug of the deoxyguanosine analog 9-β-arabinofuranosylguanine, is uniquely toxic to T lymphoblasts, compared with B lymphoblasts and normal lymphocytes, and has been developed for the treatment of T-ALL/LBL. Based on phase 1 and 2 trials in children and adults, single-agent nelarabine is approved for treatment of patients with relapsed or refractory T-ALL/LBL, with the major adverse effect being central and peripheral neurotoxicity. Since its approval in 2005, nelarabine has been studied in combination with other chemotherapy agents for relapsed disease and is also being studied as a component of initial treatment in pediatric and adult patients. Here, we review current data on nelarabine and present our approach to the use of nelarabine in the treatment of patients with T-ALL/LBL.

Resistance mechanism to Notch inhibition and combination therapy in human T-cell acute lymphoblastic leukemia

Gain-of-function mutations in NOTCH1 are among the most frequent genetic alterations in T-cell acute lymphoblastic leukemia (T-ALL), highlighting the Notch signaling pathway as a promising therapeutic target for personalized medicine. Yet, a major limitation for long-term success of targeted therapy is relapse due to tumor heterogeneity or acquired resistance. Thus, we performed a genome-wide CRISPR-Cas9 screen to identify prospective resistance mechanisms to pharmacological NOTCH inhibitors and novel targeted combination therapies to efficiently combat T-ALL. Mutational loss of phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) causes resistance to Notch inhibition. PIK3R1 deficiency leads to increased PI3K/AKT signaling, which regulates cell cycle and the spliceosome machinery, both at the transcriptional and posttranslational level. Moreover, several therapeutic combinations have been identified, in which simultaneous targeting of the cyclin-dependent kinases 4 and 6 (CDK4/6) and NOTCH proved to be the most efficacious in T-ALL xenotransplantation models.

Targeted delivery of AZD5363 to T-cell acute lymphocytic leukemia by mSiO2-Au nanovehicles

T-cell acute lymphocytic leukemia (T-ALL) is the most common cancer in children, with a low survival rate because of drug resistance and a high recurrence rate. Targeted delivery of chemotherapy drugs can reduce their side effects and improve their efficacy. The abnormality of phosphatidylinositol-3-kinase/protein kinase B/ mammalian target of rapamycin (PI3K/Akt/mTOR) pathway plays a key role in T-ALL occurrence. AZD5363 is a selective Akt inhibitor with promising therapeutic potential for tumors encoded by the PI3K/Akt/mTOR pathway. However, the toxicity and side effects have limited its application in treating T-ALL. This study aimed to design a delivery system for targeting AZD5363 to T-ALL by sgc8c aptamer designed as mesoporous silica (mSiO2) decorated with Au nanoparticles. The cell-specific targeting and cytotoxicity of mSiO2-Au-AZD5363-Apt were investigated. The mSiO2-Au nanovehicles were found feasible for AZD5363 delivery, with high loading efficiency and pH-responsive release in the acidic lysosome. More importantly, mSiO2-Au-AZD5363-Apt nanovehicles could specifically recognize and enter T-ALL cells in vitro and in vivo, effectively inhibiting the proliferation of CCRF-CEM cells. In conclusion, mSiO2-Au-AZD5363-Apt provided an effective therapeutic method for the targeted treatment of T-ALL.

YBX1 as an oncogenic factor in T-cell acute lymphoblastic leukemia

Y-box-binding protein 1 (YBX1), a member of the RNA-binding protein family, is a critical regulator of cell survival in various solid tumors and acute myeloid leukemia. However, the function of YBX1 in T-cell acute lymphoblastic leukemia (T-ALL) remains elusive. Here, we found that YBX1 was upregulated in patients with T-ALL, T-ALL cell lines, and NOTCH1-induced T-ALL mice. Furthermore, depletion of YBX1 dramatically reduced cell proliferation, induced cell apoptosis, and induced G0/G1 phase arrest in vitro. Moreover, YBX1 depletion significantly decreased the leukemia burden in the human T-ALL xenograft and NOTCH1-induced T-ALL mice model in vivo. Mechanistically, downregulation of YBX1 markedly inhibited the expression of total AKT serine/threonine kinase (AKT), p-AKT, total extracellular signal-regulated kinase (ERK), and p-ERK in T-ALL cells. Taken together, our results uncovered a critical role of YBX1 in the leukemogenesis of T-ALL, which may have great potential as a biomarker and therapeutic target in T-ALL.

PLK1 as a cooperating partner for BCL2-mediated antiapoptotic program in leukemia

The deregulation of BCL2 family proteins plays a crucial role in leukemia development. Therefore, pharmacological inhibition of this family of proteins is becoming a prevalent treatment method. However, due to the emergence of primary and acquired resistance, efficacy is compromised in clinical or preclinical settings. We developed a drug sensitivity prediction model utilizing a deep tabular learning algorithm for the assessment of venetoclax sensitivity in T-cell acute lymphoblastic leukemia (T-ALL) patient samples. Through analysis of predicted venetoclax-sensitive and resistant samples, PLK1 was identified as a cooperating partner for the BCL2-mediated antiapoptotic program. This finding was substantiated by additional data obtained through phosphoproteomics and high-throughput kinase screening. Concurrent treatment using venetoclax with PLK1-specific inhibitors and PLK1 knockdown demonstrated a greater therapeutic effect on T-ALL cell lines, patient-derived xenografts, and engrafted mice compared with using each treatment separately. Mechanistically, the attenuation of PLK1 enhanced BCL2 inhibitor sensitivity through upregulation of BCL2L13 and PMAIP1 expression. Collectively, these findings underscore the dependency of T-ALL on PLK1 and postulate a plausible regulatory mechanism.

Ginsenoside Rh2: A shining and potential natural product in the treatment of human nonmalignant and malignant diseases in the near future

BACKGROUND

Ginseng is well-known as one of the most valuable and commonly used Chinese medicines not only in ancient China but also worldwide including East, Russia, Southeast Asia, North America and some Western European countries. Ginsenosides, as one of the main high active components of Ginseng, have various pharmacological activities, such as anti-inflammatory, antianaphylaxis, anti-depression, and anticancer activities. Ginsenoside Rh2 (Rh2), one of the major bioactive ginsenosides in Panax ginseng, also exhibits versatile pharmacological activities, such as increasing non-specific resistance and specific immune response, improving cardiac function and fibrosis, anti-inflammatory effects and antitumor effects, which may serve as an excellent medicinal potential.

PURPOSE

As one of hundreds of ginsenosides being identified from ginseng, Rh2 exerts a markedly pharmacological effect on various diseases without severe toxicity, it has attracted many researchers 'attention. Although Rh2 plays important roles in some animal models and cell lines to simulate human diseases, its underlying molecular mechanisms have yet to be determined. During the past ten years, nearly 450 studies on Rh2 in the treatment of complex disease have been reported, however, up to now, no comprehensive reviews about the roles of Rh2 in animal models and cellular lines of human nonmalignant and malignant diseases have been conducted.

METHOD

We searched articles on ginsenoside-related diseases from December 2010 to February 2023 in peer-reviewed and nonclinical databases, which include Web of Science, Scopus, PubMed, China national knowledge internet and Medline, and using the following keywords: Ginsenoside Rh2, Human diseases, Cancer, Mechanisms, Chinese herbal medicine, Natural products and Signaling pathway.

RESULTS

Therefore, in this review, we make a comprehensive summary on the roles of Rh2 and support the potential mechanisms of Rh2 according to the disease classification, including nonmalignant disease such as ulcerative colitis, neuropathic pain, Asthma, myocardial injury, depression and malignant disease such as breast cancer, colorectal cancer, hepatocellular carcinoma and gastric cancer. Finally, the combination therapy of Rh2 and other medications in human diseases are summarized, apart from that, there are other problems such as the bioavailability of oral administration Rh2 to be overcome in following research.

CONCLUSION

These findings provide strong evidence that Ginsenoside Rh2 plays important roles in the treatment of nonmalignant and malignant diseases.

Malignant A-to-I RNA editing by ADAR1 drives T-cell acute lymphoblastic leukemia relapse via attenuating dsRNA sensing

Leukemia initiating cells (LICs) are regarded as the origin of leukemia relapse and therapeutic resistance. Identifying direct stemness determinants that fuel LIC self-renewal is critical for developing targeted approaches to eliminate LICs and prevent relapse. Here, we show that the RNA editing enzyme ADAR1 is a crucial stemness factor that promotes LIC self-renewal by attenuating aberrant double-stranded RNA (dsRNA) sensing. Elevated adenosine-to-inosine (A-to-I) editing is a common attribute of relapsed T-ALL regardless of molecular subtypes. Consequently, knockdown of ADAR1 severely inhibits LIC self-renewal capacity and prolongs survival in T-ALL PDX models. Mechanistically, ADAR1 directs hyper-editing of immunogenic dsRNA and retains unedited nuclear dsRNA to avoid detection by the innate immune sensor MDA5. Moreover, we uncovered that the cell intrinsic level of MDA5 dictates the dependency on ADAR1-MDA5 axis in T-ALL. 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.

WDR54 exerts oncogenic roles in T-cell acute lymphoblastic leukemia

WDR54 has been recently identified as a novel oncogene in colorectal and bladder cancers. However, the expression and function of WDR54 in T-cell acute lymphoblastic leukemia (T-ALL) were not reported. In this study, we investigated the expression of WDR54 in T-ALL, as well as its function in T-ALL pathogenesis using cell lines and T-ALL xenograft. Bioinformatics analysis indicated high mRNA expression of WDR54 in T-ALL. We further confirmed that the expression of WDR54 was significantly elevated in T-ALL. Depletion of WDR54 dramatically inhibited cell viability and induced apoptosis and cell cycle arrest at S phase in T-ALL cells in vitro. Moreover, knockdown of WDR54 impeded the process of leukemogenesis in a Jurkat xenograft model in vivo. Mechanistically, the expression of PDPK1, phospho-AKT (p-AKT), total AKT, phospho-ERK (p-ERK), Bcl-2 and Bcl-xL were downregulated, while cleaved caspase-3 and cleaved caspase-9 were upregulated in T-ALL cells with WDR54 knockdown. Additionally, RNA-seq analysis indicated that WDR54 might regulate the expression of some oncogenic genes involved in multiple signaling pathways. Taken together, these findings suggest that WDR54 may be involved in the pathogenesis of T-ALL and serve as a potential therapeutic target for the treatment of T-ALL.

Venetoclax-Resistant T-ALL Cells Display Distinct Cancer Stem Cell Signatures and Enrichment of Cytokine Signaling

Therapy resistance remains one of the major challenges for cancer treatment that largely limits treatment benefits and patient survival. The underlying mechanisms that lead to therapy resistance are highly complicated because of the specificity to the cancer subtype and therapy. The expression of the anti-apoptotic protein BCL2 has been shown to be deregulated in T-cell acute lymphoblastic leukemia (T-ALL), where different T-ALL cells display a differential response to the BCL2-specific inhibitor venetoclax. In this study, we observed that the expression of anti-apoptotic BCL2 family genes, such as BCL2, BCL2L1, and MCL1, is highly varied in T-ALL patients, and inhibitors targeting proteins coded by these genes display differential responses in T-ALL cell lines. Three T-ALL cell lines (ALL-SIL, MOLT-16, and LOUCY) were highly sensitive to BCL2 inhibition within a panel of cell lines tested. These cell lines displayed differential BCL2 and BCL2L1 expression. Prolonged exposure to venetoclax led to the development of resistance to it in all three sensitive cell lines. To understand how cells developed venetoclax resistance, we monitored the expression of BCL2, BCL2L1, and MCL1 over the treatment period and compared gene expression between resistant cells and parental sensitive cells. We observed a different trend of regulation in terms of BCL2 family gene expression and global gene expression profile including genes reported to be expressed in cancer stem cells. Gene set enrichment analysis (GSEA) showed enrichment of cytokine signaling in all three cell lines which was supported by the phospho-kinase array where STAT5 phosphorylation was found to be elevated in resistant cells. Collectively, our data suggest that venetoclax resistance can be mediated through the enrichment of distinct gene signatures and cytokine signaling pathways.

Donor CD7 Chimeric Antigen Receptor T Cell Bridging to Allogeneic Hematopoietic Stem Cell Transplantation for T Cell Hematologic Malignancy

It is crucial to quickly bridge to allogeneic hematopoietic stem cell transplantation (allo-HSCT) for hematopoietic reconstitution. Here we report on the efficacy and safety of donor CD7 chimeric antigen receptor (CAR) T cell therapy (CAR-T) bridging to allo-HSCT in treating 12 patients with relapsed/refractory (r/r) T-ALL or T-cell lymphoblastic lymphoma (T-LBL). The median time from CAR-T infusion to allo-HSCT was 33.5 days (range, 30 to 55 days). With reduced-intensity conditioning, all patients except 1 successfully engrafted. With a mean follow-up of 301 days (range, 238 to 351 days), the remaining 11 patients were alive and disease-free at their last follow-up. Acute graft-versus-host disease (GVHD) was observed in 3 patients, and chronic GVHD developed in 3 patients, all with a limited pattern. Under the current protocol, infection was the main complication post-transplantation, and all infections were well controlled except in 1 patient, who died of multiple organ failure caused by an infection-induced inflammatory cytokine storm at days 14 post-transplantation. One patient relapsed (CD7⁺), and 3 patients became minimal residual disease (MRD) positive (CD7⁺ in 1, CD7^- in 1, fusion gene positive only in 1). Subsequently, all 3 of these patients achieved an MRD-negative complete remission with either CD7 CAR-T reinfusion or immunosuppressive agent withdrawal. Our study shows for the first time that a novel strategy of donor CD7 CAR-T bridging to allo-HSCT can be highly effective and feasible in improving disease-free survival for patients with r/r T-ALL or T-LBL.

IgD/FcδR is involved in T-cell acute lymphoblastic leukemia and regulated by IgD-Fc-Ig fusion protein

T-cell acute lymphoblastic leukemia (T-ALL) has a poor prognosis as a result of severe immunosuppression and rapid tumor progression with resistance to conventional chemotherapy. Excessive IgD may play a role in T cell activation via IgD Fc receptor (FcδR). Here we aimed to investigate the effects of IgD in T-ALL and demonstrated the potential benefit by targeting IgD/FcδR in T-ALL patients with IgD-Fc-Ig fusion protein. In T-ALL patients' blood samples and cell lines, the level of IgD, the percentage of FcδR expressing cells and the binding affinity were determined by flow cytometry. T cell viability, proliferation and apoptosis were analyzed. A mouse xenograft model was used to evaluate the in vivo effect of IgD-Fc-Ig, an IgD-FcδR blocker. The levels of serum IgD and FcδR were abnormally increased in part of T-ALL patients and IgD could induce over-proliferation and inhibit apoptosis of T-ALL cells in vitro. FcδR was constitutively expressed on T-ALL cells. IgD-Fc-Ig showed similar binding affinity to FcδR and selectively blocked the stimulation effect of IgD on T-ALL cells in vitro. In vivo study exhibited that IgD-Fc-Ig may also have therapeutic benefit. IgD-Fc-Ig administration inhibited human T-ALL growth and extended survival in xenograft T-ALL mice. In conclusion, this work supports the idea of targeting IgD/FcδR in T-ALL patients with excessive IgD. IgD-Fc-Ig fusion protein might be a potential biological drug with high selectivity for T-ALL treatment.

Targeted Treatment and Immunotherapy in High-risk and Relapsed/ Refractory Pediatric Acute Lymphoblastic Leukemia

Acute lymphoblastic leukemia is the most frequent pediatric malignancy in children, comprising 30% of all pediatric malignancies; adult ALL comprises 5% of all ALL cases, which have a 186.6 per 1 million incidence. In pediatric ALL (pALL), on which this review focuses, approximately 1 in 285 children are diagnosed with cancer before the age of 20, and approximately 1 in 530 young adults between the ages of 20 and 39 years old is a childhood cancer survivor. The survival probability in pALL is now very high, approximately 80-90%. Thus, the most important is to improve supportive care and treatment based on relapse risk, optimally being based on the genetic feature of malignant cells. Improvements made by now are mainly the classifying of subgroups based on genetic characteristics such as aneuploidy or translocation and aligning them with treatment response. Relevant genetic changes in ALL pathogenesis are transcription regulators of lymphoid development (PAX5, IKZF1, EBF1, and LEF1) and/or coactivators (TBL1XR1 and ERG), lymphoid signaling (BTLA, and CD200 TOX), and tumor suppressor genes (CDKN2A, CDKN2B, RB1, and TP53). This review aims to summarize treatment strategies inhibiting tyrosine kinases, influencing different signaling pathways, BCL inhibitors, and anti-CD therapy (anti-cluster differentiation therapy) in pALL. CAR T-cell therapy (chimeric antigen receptors T-cell therapy) is under research and requires further development.

Naturally selected CD7 CAR-T therapy without genetic editing demonstrates significant antitumour efficacy against relapsed and refractory acute myeloid leukaemia (R/R-AML)

Background

The survival rate for patients with relapsed and refractory acute myeloid leukaemia (R/R-AML) remains poor, and treatment is challenging. Chimeric antigen receptor T cells (CAR-T cells) have been widely used for haematologic malignancies. Current CAR-T therapies for acute myeloid leukaemia mostly target myeloid-lineage antigens, such as CD123 and CD33, which may be associated with potential haematopoietic toxicity. As a lineage-specific receptor, CD7 is expressed in acute myeloid leukaemia cells and T cells but is not expressed in myeloid cells. Therefore, the use of CD7 CAR-T cells for R/R-AML needs to be further explored.

Methods

In this report, immunohistochemistry and flow cytometry were used to analyse CD7 expression in clinical samples from R/R-AML patients and healthy donors (HDs). We designed naturally selected CD7 CAR-T cells to analyse various functions and in vitro antileukaemic efficacy based on flow cytometry, and xenograft models were used to validate in vivo tumour dynamics.

Results

We calculated the percentage of cells with CD7 expression in R/R-AML patients with minimal residual disease (MRD) (5/16, 31.25%) from our institution and assessed CD7 expression in myeloid and lymphoid lineage cells of R/R-AML patients, concluding that CD7 is expressed in T cells but not in myeloid cells. Subsequently, we designed and constructed naturally selected CD7 CAR-T cells (CD7 CAR). We did not perform CD7 antigen knockdown on CD7 CAR-T cells because CD7 molecule expression is naturally eliminated at Day 12 post transduction. We then evaluated the ability to target and kill CD7+ acute myeloid leukaemia cells in vitro and in vivo. Naturally selected CD7 CAR-T cells efficiently killed CD7+ acute myeloid leukaemia cells and CD7+ primary blasts of R/R-AML patients in vitro and significantly inhibited leukaemia cell growth in a xenograft mouse model.

Conclusion

Naturally selected CD7 CAR-T cells represent an effective treatment strategy for relapsed and refractory acute myeloid leukaemia patients in preclinical studies.

Cellular and Molecular Effects of Eribulin in Preclinical Models of Hematologic Neoplasms

Despite the advances in understanding the biology of hematologic neoplasms which has resulted in the approval of new drugs, the therapeutic options are still scarce for relapsed/refractory patients. Eribulin is a unique microtubule inhibitor that is currently being used in the therapy for metastatic breast cancer and soft tissue tumors. Here, we uncover eribulin's cellular and molecular effects in a molecularly heterogeneous panel of hematologic neoplasms. Eribulin reduced cell viability and clonogenicity and promoted apoptosis and cell cycle arrest. The minimal effects of eribulin observed in the normal leukocytes suggested selectivity for malignant blood cells. In the molecular scenario, eribulin induces DNA damage and apoptosis markers. The ABCB1, ABCC1, p-AKT, p-NFκB, and NFκB levels were associated with responsiveness to eribulin in blood cancer cells, and a resistance eribulin-related target score was constructed. Combining eribulin with elacridar (a P-glycoprotein inhibitor), but not with PDTC (an NFkB inhibitor), increases eribulin-induced apoptosis in leukemia cells. In conclusion, our data indicate that eribulin leads to mitotic catastrophe and cell death in blood cancer cells. The expression and activation of MDR1, PI3K/AKT, and the NFκB-related targets may be biomarkers of the eribulin response, and the combined treatment of eribulin and elacridar may overcome drug resistance in these diseases.

Phase 1b study of carfilzomib with induction chemotherapy in pediatric relapsed/refractory acute lymphoblastic leukemia

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common cancer diagnosed in childhood. Survival for patients following relapse remains poor, and achieving complete remission (CR) after relapse is the first critical step to cure. Carfilzomib is a proteasome inhibitor with an acceptable safety profile and clinical activity in adults with multiple myeloma but has not been assessed in children. The primary objective of this phase 1b study was to assess the safety and tolerability of carfilzomib combined with vincristine, dexamethasone, asparaginase, and daunorubicin (VXLD) in children with relapsed and/or refractory ALL.

METHODS

Patients aged 1-21 years (n = 24) received 4-week induction therapy with carfilzomib at dose levels of 27 mg/m² (n = 3), 36 mg/m² (n = 7), 45 mg/m² (n = 4), and 56 mg/m² (n = 10) in combination with VXLD. Patients achieving stable disease were offered further consolidation chemotherapy. Analyses were based on the safety evaluable population.

RESULTS

Following dose escalation of carfilzomib, the recommended phase 2 carfilzomib dose was identified as 56 mg/m² . Grade ≥3 hematological adverse events were common (83%, 20/24 patients), and serious treatment-emergent adverse events occurred in 58% (14/24) of patients. At the end of induction, CR/CR with incomplete platelet recovery (CRp)/CR with incomplete blood count recovery (CRi) was identified in 50% of patients (n = 12/24). By the end of consolidation, cumulative CR/CRp/CRi was identified in 58% of patients (n = 14/24).

CONCLUSION

These data support the use of carfilzomib in pediatric patients with relapsed and/or refractory ALL.

Identification of a Novel Curcumin Derivative Influencing Notch Pathway and DNA Damage as a Potential Therapeutic Agent in T-ALL

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy considered curable by modern clinical management. Nevertheless, the prognosis for T-ALL high-risk cases or patients with relapsed and refractory disease is still dismal. Therefore, there is a keen interest in developing more efficient and less toxic therapeutic approaches. T-ALL pathogenesis is associated with Notch signaling alterations, making this pathway a highly promising target in the fight against T-ALL. Here, by exploring the anti-leukemic capacity of the natural polyphenol curcumin and its derivatives, we found that curcumin exposure impacts T-ALL cell line viability and decreases Notch signaling in a dose- and time-dependent fashion. However, our findings indicated that curcumin-mediated cell outcomes did not depend exclusively on Notch signaling inhibition, but might be mainly related to compound-induced DNA-damage-associated cell death. Furthermore, we identified a novel curcumin-based compound named CD2066, endowed with potentiated anti-proliferative activity in T-ALL compared to the parent molecule curcumin. At nanomolar concentrations, CD2066 antagonized Notch signaling, favored DNA damage, and acted synergistically with the CDK1 inhibitor Ro3306 in T-ALL cells, thus representing a promising novel candidate for developing therapeutic agents against Notch-dependent T-ALL.

Synthesis of an Anti-CD7 Recombinant Immunotoxin Based on PE24 in CHO and E. coli Cell-Free Systems

Recombinant immunotoxins (RITs) are an effective class of agents for targeted therapy in cancer treatment. In this article, we demonstrate the straight-forward production and testing of an anti-CD7 RIT based on PE24 in a prokaryotic and a eukaryotic cell-free system. The prokaryotic cell-free system was derived from Escherichia coli BL21 StarTM (DE3) cells transformed with a plasmid encoding the chaperones groEL/groES. The eukaryotic cell-free system was prepared from Chinese hamster ovary (CHO) cells that leave intact endoplasmic reticulum-derived microsomes in the cell-free reaction mix from which the RIT was extracted. The investigated RIT was built by fusing an anti-CD7 single-chain variable fragment (scFv) with the toxin domain PE24, a shortened variant of Pseudomonas Exotoxin A. The RIT was produced in both cell-free systems and tested for antigen binding against CD7 and cell killing on CD7-positive Jurkat, HSB-2, and ALL-SIL cells. CD7-positive cells were effectively killed by the anti-CD7 scFv-PE24 RIT with an IC50 value of 15 pM to 40 pM for CHO and 42 pM to 156 pM for E. coli cell-free-produced RIT. CD7-negative Raji cells were unaffected by the RIT. Toxin and antibody domain alone did not show cytotoxic effects on either CD7-positive or CD7-negative cells. To our knowledge, this report describes the production of an active RIT in E. coli and CHO cell-free systems for the first time. We provide the proof-of-concept that cell-free protein synthesis allows for on-demand testing of antibody−toxin conjugate activity in a time-efficient workflow without cell lysis or purification required.

Modern treatment approaches to adult acute T-lymphoblastic and myeloid/T-lymphoblastic leukemia: from current standards to precision medicine

PURPOSE OF REVIEW

To review the most recent advancements in the management of adult T-cell acute lymphoblastic leukemia (T-ALL), we summarize insights into molecular diagnostics, immunotherapy, targeted therapy and new techniques of drug sensitivity profiling that may support further therapeutic progress in T-ALL subsets.

RECENT FINDINGS

With current induction/consolidation chemotherapy and/or risk-oriented allogeneic stem cell transplantation programs up to 95% adult T-ALL patients achieve a remission and >50% (up to 80% in adolescents and young adults) are cured. The group of patients who fail upfront therapy, between 25% and 40%, is enriched in high-risk characteristics (unfavorable genetics, persistent minimal residual disease) and represents the ideal setting for the study of molecular mechanisms of disease resistance, and consequently explore novel ways of restoration of drug sensitivity and assess patient/subset-specific patterns of drug vulnerability to targeting agents, immunotherapy and cell therapy.

SUMMARY

The emerging evidence supports the contention that precision medicine may soon allow valuable therapeutic chances to adult patients with high-risk T-ALL. The ongoing challenge is to identify the best way to integrate all these new data into the therapeutic path of newly diagnosed patients, with a view to optimize the individual treatment plan and increase the cure rate.

Cytosine base editing enables quadruple-edited allogeneic CART cells for T-ALL

Allogeneic chimeric antigen receptor T-cell (CART) therapies require multiple gene edits to be clinically tractable. Most allogeneic CARTs have been created using gene editing techniques that induce DNA double-stranded breaks (DSBs), resulting in unintended on-target editing outcomes with potentially unforeseen consequences. Cytosine base editors (CBEs) install C•G to T•A point mutations in T cells, with between 90% and 99% efficiency to silence gene expression without creating DSBs, greatly reducing or eliminating undesired editing outcomes following multiplexed editing as compared with clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). Using CBE, we developed 7CAR8, a CD7-directed allogeneic CART created using 4 simultaneous base edits. We show that CBE, unlike CRISPR-Cas9, does not impact T-cell proliferation, lead to aberrant DNA damage response pathway activation, or result in karyotypic abnormalities following multiplexed editing. We demonstrate 7CAR8 to be highly efficacious against T-cell acute lymphoblastic leukemia (T-ALL) using multiple in vitro and in vivo models. Thus, CBE is a promising technology for applications requiring multiplexed gene editing and can be used to manufacture quadruple-edited 7CAR8 cells, with high potential for clinical translation for relapsed and refractory T-ALL.

Clinical experiences with venetoclax and other pro-apoptotic agents in lymphoid malignancies: lessons from monotherapy and chemotherapy combination

BH3-mimetics are a novel drug class of small molecule inhibitors of BCL2 family proteins which restore apoptosis in malignant cells. The only currently approved BH3-mimetic, the selective BCL2 inhibitor venetoclax, is highly efficacious in chronic lymphocytic leukemia and has rapidly advanced to an approved standard of care in frontline and relapsed disease in combination with anti-CD20 monoclonal antibodies. In this context, tumour lysis syndrome and myelosuppression are the most commonly encountered toxicities and are readily manageable with established protocols. Venetoclax is active in other lymphoid malignancies including several B cell non-Hodgkin lymphomas, acute lymphoblastic leukemia and multiple myeloma, with the highest intrinsic sensitivity observed in mantle cell lymphoma and Waldenstrom macroglobulinemia. Venetoclax combination with standard regimens in follicular lymphoma, multiple myeloma and aggressive B cell neoplasms has shown some promise, but further studies are required to optimize dose and scheduling to mitigate increased myelosuppression and infection risk, and to find validated biomarkers of venetoclax sensitivity. Future research will focus on overcoming venetoclax resistance, targeting other BCL2 family members and the rational design of synergistic combinations.

Temporal changes in incidence of relapse and outcome after relapse of childhood acute lymphoblastic leukemia over three decades; a Nordic population-based cohort study

Relapse remains the main obstacle to curing childhood acute lymphoblastic leukemia (ALL). The aims of this study were to compare incidence of relapse, prognostic factors, and survival after relapse between three consecutive Nordic Society of Pediatric Hematology and Oncology trials. Relapse occurred as a primary event in 638 of 4 458 children (1.0-14.9 years) diagnosed with Ph-negative ALL between 1992 and 2018. The 5-year cumulative incidence of relapse was 17.3% (95% CI 15.4-19.2%) and 16.5% (95% CI 14.3-18.8%) for patients in the ALL1992 and ALL2000 trials, respectively, but decreased to 8.4% (95% CI 7.0-10.1%) for patients in the ALL2008 trial. No changes in duration of first complete remission and site of relapse were observed over time; however, high hyperdiploidy, and t(12;21) decreased in the ALL2008 trial. The 4-year overall survival after relapse was 56.6% (95% CI 52.5-60.5%) and no statistically significant temporal improvements were observed. Age ≥10 years, T-cell immunophenotype, bone-marrow involvement, early and very early relapse, hypodiploidy, and Down syndrome all independently predicted worse outcome after relapse. Improvements in the primary treatment of childhood ALL has resulted in fewer relapses. However, failure to improve outcome of remaining relapses suggests a selection of harder-to-cure relapses and calls for new therapeutic strategies.

Long noncoding RNA endogenous bornavirus-like nucleoprotein acts as an oncogene by regulating microRNA-655-3p expression in T-cell acute lymphoblastic leukemia

Acute lymphocytic leukemia (ALL) is the most common malignant tumor in children with T-cell ALL (T-ALL), accounting for approximately 15% of all cases. Long noncoding RNAs (lncRNAs) are involved in the pathogenesis and progression of T-ALL. The present study aimed to explore the role and mechanism of action of lncRNA EBLN3P in T-ALL. We used quantitative reverse transcription-PCR (qRT-PCR) to determine the expression of lncRNA endogenous bornavirus-like nucleoprotein (EBLN3P), microRNA (miR)-655-3p, and the transcription level of matrix metalloproteinase-9 (MMP-9), and Western blot assay to quantify the protein expression level of cleaved-caspase3, caspase3, proliferating cell nuclear antigen (PCNA), and MMP-9. The potential binding sites between lncRNA EBLN3P and miR-655-3p were predicted using StarBase, and the interaction was further verified by dual-luciferase reporter assay and RNA pull-down assay. The proliferation ability of Jurkat cells was detected using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and their invasion and migration ability using transwell assay. Cell apoptosis was determined using flow cytometry (FCM) assay. The expression of lncRNA EBLN3P was upregulated while that of miR-655-3p was downregulated in human T-ALL cell lines and lncRNA EBLN3P negatively regulated miR-655-3p. LncRNA EBLN3P knockdown significantly inhibited proliferation, invasion, and migration of Jurkat cells and induced their apoptosis. Downregulating miR-655-3p reversed the effects of lncRNA EBLN3P knockdown on Jurkat cells. In conclusion, we confirmed for the first time that lncRNA EBLN3P is dysregulated in T-ALL cell lines, and lncRNA EBLN3P knockdown inhibited the malignant biological behaviors of T-ALL cells by up-regulating miR-655-3p.

Salvage Therapy in Early Relapse of T-Lymphoblastic Leukemia/Lymphoma Using Daratumumab/Nelarabine Combination: Two Consecutive Cases

Treatment of early relapses of T lymphoblastic leukemia/lymphoma is often unsuccessful. We tested an experimental regimen containing daratumumab and nelarabine in two young patients with early relapses of T lymphoblastic lymphoma and T-ALL, respectively. Both patients achieved a deep complete remission. Combining daratumumab with chemotherapy may have a role in relapsing T lymphoblastic leukemia/lymphoma.

Circ_0000745 regulates NOTCH1-mediated cell proliferation and apoptosis in pediatric T-cell acute lymphoblastic leukemia through adsorbing miR-193b-3p

BACKGROUND

T-cell acute lymphoblastic leukemia (T-ALL) is a highly proliferative hematologic malignancy. Circular RNA hsa_circ_0000745 (circ_0000745) has been reported as an oncogene in acute lymphoblastic leukemia (ALL). However, whether circ_0000745 can drive T-ALL progression by controlling notch receptor 1 (NOTCH1) expression is unclear.

METHODS

Relative expression of circ_0000745 and NOTCH1 in bone marrow (BM) samples and T-ALL cells was detected by real-time quantitative polymerase chain reaction (RT-qPCR). Loss- and gain-of-function experiments were executed to evaluate the effects of circ_0000745 and NOTCH1 on T-ALL cell proliferation and apoptosis. The microRNAs (miRs) that might jointly interact with circ_0000745 and NOTCH1 were predicted by bioinformatics analysis and verified by dual-luciferase reporter and RNA immunoprecipitation (RIP) assays.

RESULTS

Circ_0000745 and NOTCH1 were overexpressed in T-ALL BM and T-ALL cells. Functionally, both circ_0000745 and NOTCH1 overexpression promoted T-ALL cell proliferation and curbed T-ALL cell apoptosis. In contrast, both circ_0000745 and NOTCH1 silencing restrained T-ALL cell proliferation and induced T-ALL cell apoptosis. Furthermore, circ_0000745 could control T-ALL cell proliferation and apoptosis through regulating NOTCH1 expression. Importantly, circ_0000745 regulated NOTCH1 expression by sponging miR-193b-3p.

CONCLUSION

Our findings proposed a novel model in which circ_0000745 promoted cell proliferation and curbed cell apoptosis via upregulating NOTCH1 through serving as a miR-193b-3p sponge in T-ALL.

Outcomes and prognostic factors of adults with refractory or relapsed T-cell acute lymphoblastic leukemia included in measurable residual disease-oriented trials

Despite high complete remission (CR) rates with frontline therapy, relapses are frequent in adults with T-cell acute lymphoblastic leukemia (T-ALL) with limited salvage options. We analyzed the outcomes and prognostic factors for CR to salvage therapy and overall survival (OS) of patients with R/R T-ALL included in two prospective measurable residual disease-oriented trials. Seventy-five patients (70 relapsed, 5 refractory) were identified. Relapses occurred in bone marrow, isolated or combined in 50 patients, and in the central nervous system (CNS; isolated or combined) in 20. Second CR was attained in 30/75 patients (40%). Treatment with FLAG-Ida and isolated CNS relapse were independently associated with a higher CR rate after first salvage therapy. The median OS was 6.2 (95% confidence interval [CI], 3.9-8.6) months, with a 4-year OS probability of 18% (95% CI, 9%-27%). No differences in survival were observed according to the treatment with hematopoietic stem cell transplantation in patients in CR after first salvage therapy. Multivariable analysis showed a ≥12-month interval between first CR and relapse, CR after first salvage therapy and isolated CNS relapse as favorable prognostic factors for OS with hazard ratios (HR) (95% CI) of 1.931 (1.109-3.362), 2.958 (1.640-5.334), and 2.976 (1.157-7.655), respectively. This study confirms the poor outcomes of adults with R/R T-ALL among whom FLAG-Ida was the best of the rescue therapies evaluated. Late relapse, CR after first rescue therapy and isolated CNS relapse showed prognostic impact on survival. More effective rescue therapies are needed in adults with R/R T-ALL.

CARMA1 is required for Notch1-induced NF-κB activation in SIL-TAL1-negative T cell acute lymphoblastic leukemia

The NF-κB signaling pathway is an important downstream pathway of oncogenic Notch1 in T cell acute lymphoblastic leukemia (T-ALL) cells. However, the molecular mechanisms underlying the cascade activation of Notch1 in T-ALL cells are poorly understood. Here, we evaluated the role of CARMA1 in Notch1-induced NF-κB activation in T-ALL cells. CARMA1 was highly and specifically expressed in T-ALL cells and correlated with the prognosis of T-ALL patients. Interestingly, CARMA1 knockdown only inhibited the growth and proliferation of SIL-TAL1 fusion gene-negative T-ALL cells. In addition, CARMA1 knockdown arrested T-ALL cells at the G1 phase. Furthermore, CARMA1 knockdown significantly inhibited the proliferation of T-ALL cells in vivo and prolonged the survival of mice. Mechanistically, CARMA1 deficiency abolished Notch1-induced NF-κB transcriptional activation and significantly reduced expression levels of the NF-κB target genes c-Myc, Bcl-2, and CCR7. Taken together, these results of our study identify CARMA1 as one of the crucial mediators of Notch1-induced transformation of T-All cells, suggesting that CARMA1 is a promising therapeutic target for T-ALL due to its specific expression in lymphocytes. KEY MESSAGES: CARMA1 contributes to cell survival only in SIL-TAL1 negative T-ALL cells. CARMA1 is a crucial mediator of Notch1-induced activation of NF-κB pathway. CARMA1 is a promising therapeutic target for T-ALL.

Tumor-associated myeloid cells provide critical support for T-ALL

Despite harboring mutations in oncogenes and tumor suppressors that promote cancer growth, T-cell acute lymphoblastic leukemia (T-ALL) cells require exogenous cells or signals to survive in culture. We previously reported that myeloid cells, particularly dendritic cells, from the thymic tumor microenvironment support the survival and proliferation of primary mouse T-ALL cells in vitro. Thus, we hypothesized that tumor-associated myeloid cells would support T-ALL in vivo. Consistent with this possibility, in vivo depletion of myeloid cells results in a significant reduction in leukemia burden in multiple organs in 2 distinct mouse models of T-ALL and prolongs survival. The impact of the myeloid compartment on T-ALL growth is not dependent on suppression of antitumor T-cell responses. Instead, myeloid cells provide signals that directly support T-ALL cells. Transcriptional profiling, functional assays, and acute in vivo myeloid-depletion experiments identify activation of IGF1R as a critical component of myeloid-mediated T-ALL growth and survival. We identify several myeloid subsets that have the capacity to directly support survival of T-ALL cells. Consistent with mouse models, myeloid cells derived from human peripheral blood monocytes activate IGF1R and directly support survival of primary patient T-ALL cells in vitro. Furthermore, enriched macrophage gene signatures in published clinical samples correlate with inferior outcomes for pediatric T-ALL patients. Collectively, these data reveal that tumor-associated myeloid cells provide signals critical for T-ALL growth in multiple organs in vivo and implicate tumor-associated myeloid cells and associated signals as potential therapeutic targets.

Current Status of CAR T Cell Therapy for Leukemias

OPINION STATEMENT

Chimeric antigen receptor (CAR) T-cell therapy has become the standard of care for children and young adults with relapsed and refractory B-cell acute lymphoblastic leukemia (B-ALL), and it is a highly promising therapy under investigation for adults with relapsed disease. Despite having potentially life-threatening toxicities, such as cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, the benefits of CAR T-cell therapy far outweigh these risks, particularly as increased experience and improved supportive care measures are mitigating these toxicities. CAR T cells can result in complete remission for significant proportion of patients with relapsed and refractory B-ALL and permit them to proceed to potentially curative allogeneic hematopoietic stem cell transplantation (allo-HSCT). CAR T cells may also be curative by themselves. Herein lie the greatest challenges and questions for clinical investigators, specifically, how are CAR T cells best employed and how do we overcome mechanisms of resistance to them? The primary clinical question is the timing and even the necessity of allo-HSCT. Relative to resistance, we know that target antigen loss, specifically CD19, is a major contributor to resistance. However, current investigations of alternative targets, such CD22, and CAR T cells expressing dual targeting antigen receptors have demonstrated encouraging initial results and provide a high degree of optimism that the efficacy and the broader application of CAR T-cell therapy will gradually increase in B-ALL. That optimism is not as high and the challenges are increased for the application of CAR T cells in T-cell leukemias and acute myeloid leukemia due to the relative lack of suitable leukemia surface targets that are not also expressed on normal hematopoietic progenitors. Despite these significant challenges, considerable research is being conducted into the development of CAR T cells for these diseases utilizing unique technologies, which may be applicable to other diseases.

Safety of nelarabine in adults with relapsed or refractory T-cell acute lymphoblastic leukemia/lymphoma

INTRODUCTION

T-cell acute lymphoblastic leukemia (T-ALL) and lymphoma (T-LBL) are aggressive hematological malignancies accounting for 15-20% of adult acute lymphoproliferative diseases. Treatment of relapsed/refractory (R/R) T-ALL/T-LBL is challenging with very few therapeutic options.

AREAS COVERED

This report provides a concise review on the efficacy and safety of nelarabine monotherapy in adults with R/R T-ALL and T-LBL.

EXPERT OPINION

Nelarabine is approved for the treatment of adults with R/R T-ALL/T-LBL in the setting of third or more line of therapy. Hematological and neurological toxicities are the most frequent adverse events. Grade 3 and 4 neutropenia and thrombocytopenia are common, however with treatment-related deaths accounting only for 1-2% of patients. Neurological toxicity is typically characterized by a reversible peripheral neuropathy, usually mild or moderate and without treatment delay. Other neurological (somnolence and depressed level of consciousness) or extra-neurological adverse events are uncommon and rarely severe. In conclusion, nelarabine is a well tolerated and effective salvage therapy in patients with R/R T-ALL/T-LBL and has acquired an important role as a bridge-therapy to allogeneic stem cell transplantation.

The Complexity of the Tumor Microenvironment and Its Role in Acute Lymphoblastic Leukemia: Implications for Therapies

The microenvironment that surrounds a tumor, in addition to the tumor itself, plays an important role in the onset of resistance to molecularly targeted therapies. Cancer cells and their microenvironment interact closely between them by means of a molecular communication that mutually influences their biological characteristics and behavior. Leukemia cells regulate the recruitment, activation and program of the cells of the surrounding microenvironment, including those of the immune system. Studies on the interactions between the bone marrow (BM) microenvironment and Acute Lymphoblastic Leukemia (ALL) cells have opened a scenario of potential therapeutic targets which include cytokines and their receptors, signal transduction networks, and hypoxia-related proteins. Hypoxia also enhances the formation of new blood vessels, and several studies show how angiogenesis could have a key role in the pathogenesis of ALL. Knowledge of the molecular mechanisms underlying tumor-microenvironment communication and angiogenesis could contribute to the early diagnosis of leukemia and to personalized molecular therapies. This article is part of a Special Issue entitled: Innovative Multi-Disciplinary Approaches for Precision Studies in Leukemia edited by Sandra Marmiroli (University of Modena and Reggio Emilia, Modena, Italy) and Xu Huang (University of Glasgow, Glasgow, United Kingdom).

CAR-NK cells: the next wave of cellular therapy for cancer

T cells engineered to express chimeric antigen receptors (CARs) have revolutionised the field of cellular therapy for cancer. Despite its success, this strategy has some recognised limitations and toxicities. Hence, there is growing interest in developing novel cellular therapies based on non-αβ T-cell immune effector cells, including NK cells that offer clear advantages in cancer immunotherapy. As a result, NK cells are being explored as an alternative platform for CAR engineering and are becoming recognised as important players in the next generation of cellular therapies targeting cancer. In this review, we highlight preclinical and clinical studies of CAR-NK cells derived from different sources and discuss strategies under investigation to enhance the antitumor activity of these engineered innate immune cells.

The New Therapeutic Strategies in Pediatric T-Cell Acute Lymphoblastic Leukemia

Childhood acute lymphoblastic leukemia is a genetically heterogeneous cancer that accounts for 10–15% of T-cell acute lymphoblastic leukemia (T-ALL) cases. The T-ALL event-free survival rate (EFS) is 85%. The evaluation of structural and numerical chromosomal changes is important for a comprehensive biological characterization of T-ALL, but there are currently no genetic prognostic markers. Despite chemotherapy regimens, steroids, and allogeneic transplantation, relapse is the main problem in children with T-ALL. Due to the development of high-throughput molecular methods, the ability to define subgroups of T-ALL has significantly improved in the last few years. The profiling of the gene expression of T-ALL has led to the identification of T-ALL subgroups, and it is important in determining prognostic factors and choosing an appropriate treatment. Novel therapies targeting molecular aberrations offer promise in achieving better first remission with the hope of preventing relapse. The employment of precisely targeted therapeutic approaches is expected to improve the cure of the disease and quality of life of patients. These include therapies that inhibit Notch1 activation (bortezomib), JAK inhibitors in ETP-ALL (ruxolitinib), BCL inhibitors (venetoclax), and anti-CD38 therapy (daratumumab). Chimeric antigen receptor T-cell therapy (CAR-T) is under investigation, but it requires further development and trials. Nelarabine-based regimens remain the standard for treating the relapse of T-ALL.

Flow cytometric evaluation of CD38 expression levels in the newly diagnosed T-cell acute lymphoblastic leukemia and the effect of chemotherapy on its expression in measurable residual disease, refractory disease and relapsed disease: an implication for anti-CD38 immunotherapy

Background

Recently, anti-CD38 monoclonal antibody (Mab) therapy has become a focus of attention as an additional/alternative option for many hematological neoplasms including T-cell acute lymphoblastic leukemia (T-ALL). It has been shown that antitumor efficacy of anti-CD38-Mab depends on the level of CD38 expression on tumor cells. Reports on CD38 expression in T-ALL are scarce, and data on the effect of cytotoxic chemotherapy on CD38 expression are limited to very few samples. Moreover, it lacks entirely in refractory disease and in adult T-ALL. We report the flow cytometric evaluation of CD38 expression in T-ALL blasts at diagnosis and the effect of cytotoxic chemotherapy on its expression in measurable residual disease (MRD), refractory disease (MRD≥5%), and relapsed disease in a large cohort of T-ALL.

Methods

The study included 347 samples (188 diagnostic, 100 MRD, 24 refractory and 35 relapse samples) from 196 (children: 85; adolescents/adults: 111) patients with T-ALL. CD38-positive blasts percentages (CD38-PBPs) and expression-intensity (mean fluorescent intensity, CD38-MFI) were studied using multicolor flow cytometry (MFC). MFC-based MRD was performed at the end-of-induction (EOI-MRD, day 30–35) and end-of-consolidation (EOC-MRD, day 78–85) subsequent follow-up (SFU-MRD) points.

Results

Patients were classified into early thymic precursor subtype of T-ALL (ETPALL, 54/188, 28.7%), and non-ETPALL (134/188, 71.3%). Of 188, EOI-MRD assessment was available in 152, EOC-MRD was available in 96 and SFU-MRD was available in 14 patients. CD38 was found positive in 97.9% (184/188) of diagnostic, 88.7% (110/124) MRD (including 24-refractory) and 82.9% (29/35) relapsed samples. Median (95% CI) of CD38-PBPs/MFI in diagnostic, MRD, refractory, and relapsed T-ALL samples were, respectively, 85.9% (82.10%–89.91%)/4.2 (3.88–4.47), 74.0% (58.87%–83.88%)/4.6 (3.67–6.81), 79.6% (65.25%–96.11%)/4.6 (3.33–8.47) and 85.2% (74.48%–93.01%)/5.6 (4.14–8.99). No significant difference was noted in CD38 expression between pediatric versus adult and patients with ETPALL versus non-ETPALL. No change was observed in CD38-MFI between diagnostic versus MRD and diagnostic versus relapsed paired samples. However, we noticed a mild drop in the CD38-PBPs in MRD samples compared with the diagnostic samples (p=0.016).

Conclusion

We report an in-depth analysis of CD38 expression in a large cohort of T-ALL at diagnosis, during chemotherapy, and at relapse. Our data demonstrated that CD38 is robustly expressed in T-ALL blasts with a little effect of cytotoxic chemotherapy making it a potentially effective target for antiCD38-Mab therapy.

Network-based systems pharmacology reveals heterogeneity in LCK and BCL2 signaling and therapeutic sensitivity of T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy, and novel therapeutics are much needed. Profiling patient leukemia' drug sensitivities ex vivo, we discovered that 44.4% of childhood and 16.7% of adult T-ALL cases exquisitely respond to dasatinib. Applying network-based systems pharmacology analyses to examine signal circuitry, we identified preTCR-LCK activation as the driver of dasatinib sensitivity, and T-ALL-specific LCK dependency was confirmed in genome-wide CRISPR-Cas9 screens. Dasatinib-sensitive T-ALLs exhibited high BCL-XL and low BCL2 activity and venetoclax resistance. Discordant sensitivity of T-ALL to dasatinib and venetoclax is strongly correlated with T-cell differentiation, particularly with the dynamic shift in LCK vs. BCL2 activation. Finally, single-cell analysis identified leukemia heterogeneity in LCK and BCL2 signaling and T-cell maturation stage, consistent with dasatinib response. In conclusion, our results indicate that developmental arrest in T-ALL drives differential activation of preTCR-LCK and BCL2 signaling in this leukemia, providing unique opportunities for targeted therapy.

Impact of disease status at allogeneic stem cell transplantation on adolescent and young adult patients with early T-cell precursor acute lymphoblastic leukemia

Early T-cell precursor (ETP) acute lymphoblastic leukemia (ALL) is an aggressive subset of T-cell ALL, and the role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in adolescent and young adult (AYA) patients has not been sufficiently described. We retrospectively analysed the data of 30 AYA patients (19 in first complete remission [CR1], 3 in CR2, and 8 with active disease) with ETP-ALL who underwent myeloablative allogeneic hematopoietic stem cell transplantation (allo-HSCT) from HLA-matched related, n = 2, unrelated, n = 5, or HLA-haploidentical related, n = 23 donors with an emphasis on the impact of disease status on the outcomes of transplant. The stem cell source was unmanipulated G-CSF mobilized bone marrow or peripheral blood stem cells. All patients achieved neutrophil engraftment with full donor chimerism. The cumulative incidences of grade II to IV acute graft-versus-host disease (GVHD) and chronic GVHD at 2 years were 37% and 33%, respectively. Overall, 16 patients died. The causes of death were relapse (8 patients), infection (4 patients) and GVHD (4 patients). The estimated 2-year overall survival (OS) and leukemia-free survival (LFS) for the whole cohort were 47.8% and 46.2%, respectively. Patients transplanted in CR1/2 had significantly better 2-year OS and LFS than patients with active disease (61.7% vs. 12.5%, p = 0.02; and 58.3% vs. 12.5%, p = 0.04, respectively). There was a trend toward an inferior OS rate in those patients in CR1 with chemoresistance or in CR2 compared with patients in CR1 with chemosensitivity, although this did not reach statistical significance. Our data support allo-HSCT, especially from HLA-haploidentical donors as an effective therapeutic strategy in AYA patients with ETP-ALL and disease status was significantly associated with survival in these patients.

Nelarabine as salvage therapy and bridge to allogeneic stem cell transplant in 118 adult patients with relapsed/refractory T-cell acute lymphoblastic leukemia/lymphoma. A CAMPUS ALL study

The outcome of relapsed or refractory (R/R) T-cell acute lymphoblastic leukemia/lymphoma (T-ALL/T-LBL) in adults is poor, with less than 20% of patients surviving at 5 years. Nelarabine is the only drug specifically approved for R/R T-ALL/T-LBL, but the information to support its use is based on limited available data. The aim of this observational phase four study was to provide recent additional data on the efficacy and safety of nelarabine in adults with R/R T-ALL/T-LBL and to evaluate the feasibility and outcome of allogeneic hematopoietic stem cell transplant (SCT) after salvage with nelarabine therapy. The primary endpoints were overall response rate (ORR) and overall survival (OS). Additional endpoints were safety, SCT rate and post-SCT OS. Between May 2007 and November 2018, 118 patients received nelarabine salvage therapy at 27 Italian hematology sites. The median age was 37 years (range 18-74 years), 73% were male, 77 had a diagnosis of T-ALL and 41 of T-LBL, and 65/118 (55%) had received more than two lines of therapy. The median number of nelarabine cycles was two (range 1-4); 43/118 (36%) patients had complete remission (CR), 16 had partial remission (14%) and 59 (50%) were refractory, with an ORR of 50%. The probability of OS, from the first dose of nelarabine, was 37% at 1 year with a median survival of 8 months. The OS at 1 year was significantly better for the 47 patients (40%) who underwent SCT after nelarabine salvage therapy (58% vs 22%, log-rank P < .001). The probability of OS at 2 and 5 years from SCT was 46% and 38%, respectively. Seventy-five patients (64%) experienced one or more drug-related adverse events (AE). Grade III-IV neurologic toxicities were observed in 9/118 (8%) of cases and thrombocytopenia or/and neutropenia (grade III-IV) were reported in 41% and 43% of cases, respectively. In conclusion, this is one of the largest cohorts of adult patients with R/R T-ALL/T-LBL treated in real life with nelarabine. Taking into account the poor prognosis of this patient population, nelarabine represents an effective option with an ORR of 50% and a CR rate of 36%. In addition, 40% of cases following nelarabine salvage therapy could undergo SCT with an expected OS at 2 and 5 years of 46% and 38%, respectively. The safety profile of nelarabine was acceptable with only 8% of cases showing grade III-IV neurological AE.

LEF1 Induces DHRS2 Gene Expression in Human Acute Leukemia Jurkat T-Cells

Objective

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive disease resulting from the accumulation of genetic changes that affect the development of T-cells. The precise role of lymphoid enhancer-binding factor 1 (LEF1) in T-ALL has been controversial since both overexpression and inactivating LEF1 mutations have been reported to date. Here, we investigate the potential gene targets of LEF1 in the Jurkat human T-cell leukemia cell line.

Materials and Methods

We used small interfering RNA (siRNA) technology to knock down LEF1 in Jurkat cells and then compared the gene expression levels in the LEF1 knockdown cells with non-targeting siRNA-transfected and non-transfected cells by employing microarray analysis.

Results

We identified DHRS2, a tumor suppressor gene, as the most significantly downregulated gene in LEF1 knockdown cells, and we further confirmed its downregulation by real-time quantitative polymerase chain reaction (qRT-PCR) in mRNA and at protein level by western blotting.

Conclusion

Our results revealed that DHRS2 is positively regulated by LEF1 in Jurkat cells, which indicates the capability of LEF1 as a tumor suppressor and, together with previous reports, suggests that LEF1 exhibits a regulatory role in T-ALL via not only its oncogenic targets but also tumor suppressor genes.

MALT1 Inhibition as a Therapeutic Strategy in T-Cell Acute Lymphoblastic Leukemia by Blocking Notch1-Induced NF-κB Activation

Current treatment of T-cell acute lymphoblastic leukemia (T-ALL) is primarily based on high-intensity combination chemotherapy, which has serious side effects. Therefore, developments of novel targeted therapeutics are urgently needed for treatment of T-ALL. In this study, we found that mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a novel promising therapeutic target for treatment of T-ALL. MALT1 inhibitor MI-2 significantly suppressed the cell growth, proliferation, and colony formation of T-ALL cells. Furthermore, MI-2 induced cell apoptosis of T-ALL via a mitochondrial-dependent pathway. In a T-ALL mouse model, MI-2 significantly reduced leukemic burden and prolonged the survival of leukemia-bearing mice. Mechanistically, MALT1 inhibition effectively blocked both baseline and Notch1-induced activation of nuclear factor κB pathway, which mediates T-ALL cell survival. In conclusion, our results highlight the potential role of MALT1 as an attractive target for treatment of T-ALL and support the potential of MI-2 or other MALT1 inhibitors to clinical trials in T-ALL.

New Approaches to Treating Challenging Subtypes of ALL in AYA Patients

PURPOSE OF REVIEW

The treatment of acute lymphoblastic leukemia (ALL) in adolescent and young adult (AYA) patients has markedly improved with the adoption of pediatric-inspired protocols. However, there remain several subtypes of ALL that represent significant therapeutic challenges. Here, we review the current evidence guiding treatment of Philadelphia chromosome-positive (Ph+), Philadelphia chromosome-like (Ph-L), and early T-precursor (ETP) ALL in the AYA population.

RECENT FINDINGS

Clinical trials in Ph + ALL have demonstrated the superior efficacy of second- and third-generation tyrosine kinase inhibitors (TKIs) to induce and maintain remission. Current efforts now focus on determining the durability of these remissions and which patients will benefit from transplant. For Ph-like and ETP ALL, recent studies are investigating the addition of novel agents to standard treatment. The treatment of Ph + ALL has significantly improved with the addition of potent TKIs. However, the treatment of Ph-like and ETP ALL remains a challenge. At this time, the judicious use of allogenic transplant is the only current approach to modify this increased risk.

Comparison of Early T-Cell Precursor and Non-ETP Subtypes Among 122 Chinese Adults With Acute Lymphoblastic Leukemia

Background: Adult T-cell acute lymphoblastic leukemia (T-ALL) is a rare hematological malignancy and significantly linked to poor outcomes. Early T-cell precursor (ETP) leukemia is a unique subtype of T-ALL. The aim of this study is to compare the differences between ETP and non-ETP ALLs in China.

Methods: We retrospectively analyzed the records of 122 adult T-ALL patients diagnosed and treated at our center between January 2014 and June 2019. All the patients enrolled were categorized into ETP and non-ETP ALL by immunophenotype, and further statistical analyses about clinical data and prognostic factors were performed.

Results: Among the 122 cases, the male-to-female ratio was 2.8:1, and the median age is 29 (range, 16–82) years. Except for 10 patients with insufficient immunophenotyping results, 47.3% (53/112) are ETP and 52.7% (59/112) are non-ETP. Compared with non-ETP patients, ETP-ALL patients had lower white blood cell counts and lactate dehydrogenase levels, while they were older and had higher platelet counts and fibrinogen levels (all p < 0.05). Complete remission (CR) was achieved in 68.0% (83/122) of patients, 64.2 and 76.3% in ETP and non-ETP, respectively (p = 0.160). In total, 44.6% (37/83) of patients relapsed. Allogeneic stem cell transplantation (allo-SCT) was successfully performed in 36.1% (44/122) of patients, of which 79.5% (35/44) were in CR1. With a median follow-up of 9.1 (range, 0.5–70.3) months, the estimated 2-year overall survival (OS) and relapse-free survival (RFS) rates for the cohort were 38.0 ± 5.1 and 39.1 ± 6.3%, respectively. In the ETP group, the 2-year OS rate was 40.7 ± 8.2% and the RFS rate was 47.2 ± 10.7%, while in the non-ETP group, the 2-year OS rate was 37.9 ± 7.0% and the RFS rate was 39.2 ± 8.3% (both p > 0.05). In the landmark analysis of CR1 patients who had a survival of more than 6 months, the allo-SCT group had significantly better survival outcomes than the chemotherapy group, and the 2-year OS rates and RFS rates were 80.1 ± 7.3 vs. 28.4 ± 8.4% and 68.9 ± 8.8 vs. 12.8 ± 7.2%, respectively (both p < 0.0001). A multivariate analysis suggests that allo-SCT acts as an independent prognostic factor for both OS and RFS.

Conclusions: Our results revealed that ETP accounted for a high proportion of T-ALL in Chinese. There are no CR rates and prognosis differences between ETP and non-ETP. Allo-SCT in CR1 can significantly improve patients' survival.