Involvement of the central nervous system in acute lymphoblastic leukemia: opinions on molecular mechanisms and clinical implications based on recent data

A brain organoid/ALL coculture model reveals the AP-1 pathway as critically associated with CNS involvement of BCP-ALL

ABSTRACT

Central nervous system (CNS) involvement remains a clinical hurdle in treating childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL). The disease mechanisms of CNS leukemia are primarily investigated using 2-dimensional cell culture and mouse models. Given the variations in cellular identity and architecture between the human and murine CNS, it becomes imperative to seek complementary models to study CNS leukemia. Here, we present a first-of-its-kind 3-dimensional coculture model combining human brain organoids and BCP-ALL cells. We noticed significantly higher engraftment of BCP-ALL cell lines and patient-derived xenograft (PDX) cells in cerebral organoids than non-ALL cells. To validate translatability between organoid coculture and in vivo murine models, we confirmed that targeting CNS leukemia-relevant pathways such as CD79a/Igα or C-X-C motif chemokine receptor 4-stromal cell-derived factor 1 reduced the invasion of BCP-ALL cells into organoids. RNA sequencing and functional validations of organoid-invading leukemia cells compared with the noninvaded fraction revealed significant upregulation of activator protein 1 (AP-1) transcription factor-complex members in organoid-invading cells. Moreover, we detected a significant enrichment of AP-1 pathway genes in PDX ALL cells recovered from the CNS compared with spleen blasts of mice that had received transplantation with TCF3::PBX1+ PDX cells, substantiating the role of AP-1 signaling in CNS disease. Accordingly, we found significantly higher levels of the AP-1 gene, jun proto-oncogene, in patients initially diagnosed as CNS-positive BCP-ALL compared with CNS-negative cases as well as CNS-relapse vs non-CNS-relapse cases in a cohort of 100 patients with BCP-ALL. Our results suggest CNS organoids as a novel model to investigate CNS involvement and identify the AP-1 pathway as a critical driver of CNS disease in BCP-ALL.

Selective inhibition of HDAC class IIA as therapeutic intervention for KMT2A-rearranged acute lymphoblastic leukemia

KMT2A-rearranged acute lymphoblastic leukemia (ALL) is characterized by deregulation of the epigenome and shows susceptibility towards histone deacetylase (HDAC) inhibition. Most broad-spectrum HDAC inhibitors simultaneously target multiple human HDAC isoforms. Consequently, they often induce toxicity and especially in combination with other therapeutic agents. Therefore, more specifically targeting HDAC isoforms may represent a safer therapeutic strategy. Here we show that shRNA-mediated knock-down of the class IIA HDAC isoforms HDAC4, HDAC5, and HDAC7 results in apoptosis induction and cell cycle arrest in KMT2A-rearranged ALL cells. In concordance, the HDAC4/5 selective small molecule inhibitor LMK-235 effectively eradicates KMT2A-rearranged ALL cell lines as well as primary patient samples in vitro. However, using a xenograft mouse model of KMT2A-rearranged ALL we found that the maximum achievable dose of LMK-235 was insufficient to induce anti-leukemic effects in vivo. Similar results were obtained for the specific class IIA HDAC inhibitors MC1568 and TMP195. Finally, LMK-235 appeared to exert minimal anti-leukemic effects in vivo in combination with the BCL-2 inhibitor venetoclax, but not enough to prolong survival in treated mice. In conclusion, class IIA HDAC isoforms represent attractive therapeutic target in KMT2A-rearranged ALL, although clinical applications require the development of more stable and efficient specific HDAC inhibitors.

The characterization and the impact of CSF pleocytosis during blinatumomab therapy for adult acute lymphoblastic leukemia

Reactive pleocytosis in the CSF has been observed with blinatumomab but has not been well-described. We performed a retrospective study of 88 patients who received intrathecal chemotherapy (IT) while on blinatumomab with CSF analyzed to determine if pleocytosis had an impact efficacy and safety. Blinatumomab was used for relapsed/refractory 62.5%, MRD-positive 31.8%, and consolidation in MRD-negative 5.7%. The incidence of pleocytosis in CSF was 51% and was more frequent after day 15 (55.8% vs. 18.2%, p = 0.025). Pleocytosis did not impact CR, clearance of MRD positivity, PFS and OS rates. Lower incidence of non-CNS extramedullary relapse was seen (3.7% vs. 30.8%, p = 0.011) with pleocytosis in CSF. Analysis of CSF by flow cytometry showed median CD4:CD8 ratio of 1.34. In conclusion, CSF pleocytosis is prevalent with blinatumomab but only demonstrated lower rates of non-CNS extramedullary relapse but no impact on CNS relapse or neurotoxicity.

Clinical Characteristics and Cytogenetics of Childhood Acute Lymphoblastic Leukemia in a Single Center in Pakistan

Objectives. This study aimed to find the association between clinical characteristics, cytogenetics, and post-induction outcomes of childhood acute lymphoblastic leukemia. Methods. The study was conducted at the Indus Hospital in Karachi. Initial total leukocyte count (TLC), cytogenetics, CNS status, and post-induction remission status were recorded. Results. Out of 108 children diagnosed with ALL, 66 (61.1%) were male and 42 (38.9%) were female. The majority 90 (83.3%) had B-ALL. CNS1 status was observed in 76 (84.4%) B-ALL and 18 (88.9%) T-ALL. All T-ALL and 89 (98.8%) B-ALL achieved remission post-induction. In B-ALL, 50 (55.5%) had a normal diploid karyotype, and 22 (24.4%) had numerical abnormalities. No typical gene rearrangement was observed in 66 (73.3%), 11 (12.2%) had BCR::ABL1, 10 (11.1%) had ETV6::RUNX1 and 3 (3.3%) KMT2A on FISH. No significant difference was observed between cytogenetics and clinical characteristics (P > .05). Conclusion. The study provides valuable data on childhood acute lymphoblastic leukemia in the Pakistani population.

Neurological manifestations in dogs with acute leukemia

Canine acute leukemia is a rare hematopoietic neoplasm. Neurological abnormalities have been frequently reported in dogs with acute leukemia (AL). However, the description of the presentation and findings are limited. This study aimed to describe the clinical findings in dogs with acute leukemia presenting with neurological signs as their primary complaint. The database of a private referral hospital was searched for cases that presented to the neurological department with neurological deficits and were subsequently diagnosed with acute leukemia. Six cases were included; all had neurological clinical signs and an abnormal neurological examination. All cases had a focal neuroanatomical localisation on neurological examination (brain n = 4; spinal = 2). Out of the four dogs with a complete magnetic resonance imaging (MRI) study, there was an ill-defined infiltrative pattern with abnormal signal intensity in the central nervous system (CNS) in three dogs and the loss of grey and white matter differentiation in the brain (n = 2) and/or spinal cord (n = 2). Other MRI findings included abnormal meningeal enhancement (n = 3), changes affecting spinal nerves and epaxial muscles (n = 2), and lymphadenopathy in the field of view (n = 2). The bone marrow assessment on MRI showed evidence of signal change (n = 3), characterized by a loss of normal fat opacity and an abnormal degree of contrast enhancement. The cerebrospinal fluid (CSF) analysis of the four dogs showed an increased protein level with non-specific pleocytosis and without evidence of malignant cells. Treatment with cytotoxic medication was implemented in two dogs. The dogs diagnosed with acute leukemia had focal neuroanatomical localisation, an infiltrative CNS pattern, and bone marrow remodulation on MRI with an increase in CSF protein and negative cytology analysis.

CD19-Specific CAR-T Cell Treatment of 115 Children and Young Adults with Acute B Lymphoblastic Leukemia: Long-term Follow-up

PURPOSE

Chemotherapy has been the primary treatment for patients with B-cell acute lymphoblastic leukemia (B-ALL). However, there are still patients who are not sensitive to chemotherapy, including those with refractory/relapse (R/R) disease and those experiencing minimal residual disease (MRD) re-emergence. Chimeric antigen receptor-T lymphocytes (CAR-T) therapy may provide a new treatment option for these patients.

MATERIALS AND METHODS

Our institution conducted a single-arm prospective clinical trial (ChiCTR-OPN-17013507) using CAR-T-19 to treat R/R B-ALL and MRD re-emergent patients. One hundred and fifteen patients, aged 1-25 years (median age, 8 years), were enrolled, including 67 R/R and 48 MRD re-emergent CD19-positive B-ALL patients.

RESULTS

All patients achieved morphologic complete remission (CR), and within 1 month after infusion, 111 out of 115 (96.5%) patients achieved MRD-negative CR. With a median follow-up time of 48.4 months, the estimated 4-year leukemia-free survival (LFS) rate and overall survival (OS) rate were 68.7%±4.5% and 70.7%±4.3%, respectively. There were no significant differences in long-term efficacy observed among patients with different disease statuses before infusion (4-year OS: MRD re-emergence vs. R/R B-ALL, 70.6%±6.6% vs. 66.5%±6.1%, p=0.755; 4-year LFS: MRD re-emergence vs. R/R B-ALL, 67.3%±7.0% vs. 63.8%±6.2%, p=0.704). R/R B-ALL patients bridging to transplantation after CAR-T treatment had a superior OS and LFS compared to those who did not. However, for MRD re-emergent patients, there was no significant difference in OS and LFS, regardless of whether they underwent hematopoietic stem cell transplantation or not.

CONCLUSION

CD19 CAR-T therapy effectively and safely cures both R/R B-ALL and MRD re-emergent patients.

Development of combination therapies with BTK inhibitors and dasatinib to treat CNS-infiltrating E2A-PBX1+/preBCR+ ALL

ABSTRACT

The t(1;19) translocation, encoding the oncogenic fusion protein E2A (TCF3)-PBX1, is involved in acute lymphoblastic leukemia (ALL) and associated with a pre-B-cell receptor (preBCR+) phenotype. Relapse in patients with E2A-PBX1+ ALL frequently occurs in the central nervous system (CNS). Therefore, there is a medical need for the identification of CNS active regimens for the treatment of E2A-PBX1+/preBCR+ ALL. Using unbiased short hairpin RNA (shRNA) library screening approaches, we identified Bruton tyrosine kinase (BTK) as a key gene involved in both proliferation and dasatinib sensitivity of E2A-PBX1+/preBCR+ ALL. Depletion of BTK by shRNAs resulted in decreased proliferation of dasatinib-treated E2A-PBX1+/preBCR+ cells compared with control-transduced cells. Moreover, the combination of dasatinib with BTK inhibitors (BTKi; ibrutinib, acalabrutinib, or zanubrutinib) significantly decreased E2A-PBX1+/preBCR+ human and murine cell proliferation, reduced phospholipase C gamma 2 (PLCG2) and BTK phosphorylation and total protein levels and increased disease-free survival of mice in secondary transplantation assays, particularly reducing CNS-leukemic infiltration. Hence, dasatinib with ibrutinib reduced pPLCG2 and pBTK in primary ALL patient samples, including E2A-PBX1+ ALLs. In summary, genetic depletion and pharmacological inhibition of BTK increase dasatinib effects in human and mouse with E2A-PBX1+/preBCR+ ALL across most of performed assays, with the combination of dasatinib and BTKi proving effective in reducing CNS infiltration of E2A-PBX1+/preBCR+ ALL cells in vivo.

The CNS microenvironment promotes leukemia cell survival by disrupting tumor suppression and cell cycle regulation in pediatric T-cell acute lymphoblastic leukemia

A major obstacle in improving survival in pediatric T-cell acute lymphoblastic leukemia is understanding how to predict and treat leukemia relapse in the CNS. Leukemia cells are capable of infiltrating and residing within the CNS, primarily the leptomeninges, where they interact with the microenvironment and remain sheltered from systemic treatment. These cells can survive in the CNS, by hijacking the microenvironment and disrupting normal functions, thus promoting malignant transformation. While the protective effects of the bone marrow niche have been widely studied, the mechanisms behind leukemia infiltration into the CNS and the role of the CNS niche in leukemia cell survival remain unknown. We identified a dysregulated gene expression profile in CNS infiltrated T-ALL and CNS relapse, promoting cell survival, chemoresistance, and disease progression. Furthermore, we discovered that interactions between leukemia cells and human meningeal cells induced epigenetic alterations, such as changes in histone modifications, including H3K36me3 levels. These findings are a step towards understanding the molecular mechanisms promoting leukemia cell survival in the CNS microenvironment. Our results highlight genetic and epigenetic alterations induced by interactions between leukemia cells and the CNS niche, which could potentially be utilized as biomarkers to predict CNS infiltration and CNS relapse.

Simulating neuronal development: exploring potential mechanisms for central nervous system metastasis in acute lymphoblastic leukemia

Background

Acute lymphoblastic leukemia (ALL) is prone to metastasize to the central nervous system (CNS), which is an important cause of poor treatment outcomes and unfavorable prognosis. However, the pathogenesis of CNS metastasis of ALL cells has not been fully illuminated. Recent reports have shed some light on the correlation between neural mechanisms and ALL CNS metastasis. These progressions prompt us to study the relationship between ALL central nervous system metastasis and neuronal development, exploring potential biomarkers and therapeutic targets of CNS metastasis.

Materials and methods

ALL central nervous system metastasis- and neuronal development-related differentially expressed genes (DEGs) were identified by analyzing gene expression datasets GSE60926 and GSE13715. Target prediction and network analysis methods were applied to assess protein-protein interaction networks. Gene Ontology (GO) terms and pathway enrichment for DEGs were assessed. Co-expressed differentially expressed genes (co-DEGs) coupled with corresponding predicted microRNAs (miRNAs) were studied as well. Reverse transcription-polymerase chain reaction (RT-PCR) and flow cytometry were employed for the validation of key co-DEGs in primary ALL cells. Furthermore, ALL cells were treated with a vascular endothelial growth factor (VEGF) inhibitor to block neuronal development and assess changes in the co-DEGs.

Results

We identified 216, 208, and 204 DEGs in ALL CNS metastasis specimens and neuronal development samples (GSE60926 and GSE13715). CD2, CD3G, CD3D, and LCK may be implicated in ALL CNS metastasis. LAMB1, MATN3, IGFBP3, LGALS1, and NEUROD1 may be associated with neuronal development. Specifically, four co-DEGs (LGALS1, TMEM71, SHISA2, and S100A11) may link ALL central nervous system metastasis and neuronal development process. The miRNAs for each co-DEG could be potential biomarkers or therapeutic targets for ALL central nervous system metastasis, especially hsa-miR-22-3p, hsa-miR-548t-5p, and hsa-miR-6134. Additionally, four co-DEGs (LGALS1, TMEM71, SHISA2, and S100A11) were validated in CNS-infiltrated ALL cells. The VEGF inhibitor demonstrated a suppressive effect on mRNA and protein expression of key co-DEGs.

Conclusion

The bioinformatic survey and key gene validation suggest a possible correlation between ALL CNS metastasis and the neuronal development process. Simulating the neuronal development process might be a possible strategy for CNS metastasis in ALL. LGALS1, TMEM71, SHISA2, and S100A11 genes are promising and novel biomarkers and targets in ALL CNS metastasis.

Diagnostic and therapeutic advances in adults with acute lymphoblastic leukemia in the era of gene analysis and targeted immunotherapy

Acute lymphoblastic leukemia (ALL) is one of the most rapidly changing hematological malignancies with advanced understanding of the genetic landscape, detection methods of minimal residual disease (MRD), and the development of immunotherapeutic agents with good clinical outcomes. The annual incidence of adult ALL in Korea is 300-350 patients per year. The WHO classification of ALL was revised in 2022 to reflect the molecular cytogenetic features and suggest new adverse- risk subgroups, such as Ph-like ALL and ETP-ALL. We continue to use traditional adverse-risk features and cytogenetics, with MRD-directed post-remission therapy including allogeneic hematopoietic cell transplantation. However, with the introduction of novel agents, such as ponatinib, blinatumomab, and inotuzumab ozogamicin incorporated into frontline therapy, good MRD responses have been achieved, and overall survival outcomes are improving. Accordingly, some clinical trials have suggested a possible era of chemotherapy-free or transplantation-free approaches in the near future. Nevertheless, relapse of refractory ALL still occurs, and some poor ALL subtypes, such as Ph-like ALL and ETP-ALL, are unsolved problems for which novel agents and treatment strategies are needed. In this review, we summarize the currently applied diagnostic and therapeutic practices in the era of advanced genetic analysis and targeted immunotherapies in United States and Europe and introduce real-world Korean data.

Clinical examination and imaging resources in children and adolescent back pain

Back pain is a relatively common complaint in children and adolescents. The pediatric patient presenting with back pain can often be challenging, and there are many well-known organic diagnoses that should not be missed. In younger children, an organic cause of back pain can often be found. However, back pain in older children and adolescents is often "non-specific." The differential diagnosis of back pain in children includes neoplasms, developmental, and inflammatory conditions. Basic steps should include an in-depth anamnesis, a systematic physical examination, and standard spine radiographs (anteroposterior and lateral). Nevertheless, advanced diagnostic imaging and laboratory studies should be included when indicated to avoid missing or delaying a serious diagnosis. If other types of imaging tests are necessary (magnetic resonance imaging, computed tomography, bone scan, or single photon emission computed tomography), they should be guided by diagnostic suspicion.

PPARG, GNG12, and CD19 are potential independent predictors of central nerve recurrence in childhood acute lymphoblastic leukemia

OBJECTIVE

To identify biomarkers that can predict the recurrence of the central nervous system (CNS) in children with acute lymphoblastic leukemia (ALL).

MATERIALS AND METHODS

The transcriptome and clinical data of ALL in children were downloaded from the TARGET database. Transcriptome data were analyzed by bioinformatics method to identify core (hub) genes and establish a risk assessment model. Univariate Cox analysis was performed on each clinical data, and multivariate Cox regression analysis was performed on the obtained results and risk score. The children ALL phase I samples from TARGET database were used for validation.

RESULTS

Univariate multivariate Cox analysis of 10 hub genes identified showed that PPARG (HR = 0.78, 95%CI = 0.67-0.91, p = 0.007), CD19 (HR = 1.15, 95%CI = 1.05-1.26, p = 0.003) and GNG12 (HR = 1.25, 95%CI = 1.04-1.51, p = 0.017) had statistical differences. The risk score was statistically significant in univariate (HR = 3.06, 95%CI = 1.30-7.19, p = 0.011) and multivariate (HR = 1.81, 95%CI = 1.16-2.32, p = 0.046) Cox regression analysis. The survival analysis results of the high and low-risk groups were different when the validation dataset was substituted into the model (p = 0.018). Then, we constructed a Nomogram which had a concordance index of survival prediction of 0.791(95%CI= 0.779-0.803). In addition, the CNS involvement grading status at first diagnosis CNS3 vs. CNS1 (HR = 5.74, 95%CI = 2.01-16.4, p = 0.001), T cell vs B cell (HR = 1.63, 95% CI = 1.06-2.49, p = 0.026) were also statistically significant.

CONCLUSIONS

PPARG, GNG12, and CD19 may be predictors of CNS relapse in childhood ALL.

Regulation and Functions of α6-Integrin (CD49f) in Cancer Biology

Over the past decades, our knowledge of integrins has evolved from being understood as simple cell surface adhesion molecules to receptors that have a complex range of intracellular and extracellular functions, such as delivering chemical and mechanical signals to cells. Consequently, they actively control cellular proliferation, differentiation, and apoptosis. Dysregulation of integrin signaling is a major factor in the development and progression of many tumors. Many reviews have covered the broader integrin family in molecular and cellular studies and its roles in diseases. Nevertheless, further understanding of the mechanisms specific to an individual subunit of different heterodimers is more useful. Thus, we describe the current understanding of and exploratory investigations on the α6-integrin subunit (CD49f, VLA6; encoded by the gene itga6) in normal and cancer cells. The roles of ITGA6 in cell adhesion, stemness, metastasis, angiogenesis, and drug resistance, and as a diagnosis biomarker, are discussed. The role of ITGA6 differs based on several features, such as cell background, cancer type, and post-transcriptional alterations. In addition, exosomal ITGA6 also implies metastatic organotropism. The importance of ITGA6 in the progression of a number of cancers, including hematological malignancies, suggests its potential usage as a novel prognostic or diagnostic marker and useful therapeutic target for better clinical outcomes.

Evaluation and Treatment of the Child with Acute Back Pain

Back pain is common, in up to 30% of children, increasing with age. Eighty percent is benign, mechanical type, improving within 2 weeks of conservative care. Required for those not improving is in-depth evaluation, including MRI, laboratory, and peer consultations. Spondylolysis and spondylolisthesis comprise almost 10% of pediatric back pain, often caused by lumbar hyperextension activities and treated conservatively in most cases. Osteoid osteomas and osteoblastomas constitute the most common benign spinal tumors in childhood. Aggressive and malignant tumors of the spine are rare but when present require tertiary care referral and a comprehensive oncology team for optimal life-sustaining outcomes.

CXCR4 antagonists disrupt leukaemia-meningeal cell adhesion and attenuate chemoresistance

The effective prophylaxis and treatment of central nervous system (CNS) involvement in acute lymphoblastic leukaemia (ALL) remains a significant clinical challenge. Developing novel and more effective CNS-directed therapies has been hampered, in part, by our limited understanding of the leukaemia niche in the CNS relative to the bone marrow. Accordingly, defining the molecular and cellular components critical for the establishment and maintenance of the CNS leukaemia niche may lead to new therapeutic opportunities. In prior work we showed that direct intercellular interactions between leukaemia and meningeal cells enhance leukaemia chemoresistance in the CNS. Herein, we show that the CXCR4/CXCL12 chemokine axis contributes to leukaemia-meningeal cell adhesion. Importantly, clinically tested CXCR4 antagonists, which are likely to cross the blood-brain and blood-cerebral spinal fluid barriers and penetrate the CNS, effectively disrupted leukaemia-meningeal cell adhesion. Moreover, by disrupting these intercellular interactions, CXCR4 antagonists attenuated leukaemia chemoresistance in leukaemia-meningeal cell co-culture experiments and enhanced the efficacy of cytarabine in targeting leukaemia cells in the meninges in vivo. This work identifies the CXCR4/CXCL12 axis as an important regulator of intercellular interactions within the CNS leukaemia niche and supports further testing of the therapeutic efficacy of CXCR4 antagonists in overcoming CNS niche-mediated chemoresistance.

Venetoclax Penetrates the Blood Brain Barrier: A Pharmacokinetic Analysis in Pediatric Leukemia Patients

Infiltration of malignant cells into the central nervous system in hematological malignancies correlates with poor clinical outcomes. Investigations into the penetration of venetoclax into the central nervous system have been limited. We report venetoclax pharmacokinetics in plasma and cerebrospinal fluid samples from a Phase 1 study in pediatric patients with relapsed or refractory malignancies that demonstrate venetoclax ability to cross into the central nervous system. Venetoclax was detected in cerebrospinal fluid (CSF) samples, with concentrations ranging from < 0.1 to 26 ng/mL (mean, 3.6 ng/mL) and a plasma:CSF ratio ranging from 44 to 1559 (mean, 385). Plasma:CSF ratios were comparable among patients with AML and ALL and no clear trend was observed in the ratios over the course of treatment. Moreover, improvement in central nervous system (CNS) involvement status was observed in patients who had measurable concentrations of venetoclax in the CSF. CNS resolution was observed for up to six months while on treatment. These findings highlight the potential role of venetoclax and provide the opportunity to further investigate its utility in improving clinical outcomes for patients with CNS complications.

How I prevent and treat central nervous system disease in adults with acute lymphoblastic leukemia

The central nervous system (CNS) is the most important site of extramedullary disease in adults with acute lymphoblastic leukemia (ALL). Although CNS disease is identified only in a minority of patients at the time of diagnosis, subsequent CNS relapses (either isolated or concurrent with other sites) occur in some patients even after the delivery of prophylactic therapy targeted to the CNS. Historically, prophylaxis against CNS disease has included intrathecal (IT) chemotherapy and radiotherapy (RT), although the latter is being used with decreasing frequency. Treatment of a CNS relapse usually involves intensive systemic therapy and cranial or craniospinal RT along with IT therapy and consideration of allogeneic hematopoietic cell transplant. However, short- and long-term toxicities can make these interventions prohibitively risky, particularly for older adults. As new antibody-based immunotherapy agents have been approved for relapsed/refractory B-cell ALL, their use specifically for patients with CNS disease is an area of keen interest not only because of the potential for efficacy but also concerns of unique toxicity to the CNS. In this review, we discuss data-driven approaches for these common and challenging clinical scenarios as well as highlight how recent findings potentially support the use of novel immunotherapeutic strategies for CNS disease.

Glymphatic system dysfunction in pediatric acute lymphoblastic leukemia without clinically diagnosed central nervous system infiltration: a novel DTI-ALPS method

BACKGROUND AND OBJECTIVE

Central nervous system (CNS) infiltration commonly occurs in children with acute lymphoblastic leukemia (ALL). Nevertheless, CNS infiltration is rarely detected at the initial diagnosis. The glymphatic system, which regulates cerebrospinal fluid (CSF) and interstitial fluid transport, is considered one of the possible routes of CNS infiltration by leukemia cells. In this study, we used diffusion tensor image analysis along the perivascular space (DTI-ALPS) method to investigate glymphatic system function and obtained CSF volume using synthetic magnetic resonance imaging (SyMRI) in pediatric ALL without clinically diagnosed CNS infiltration.

MATERIALS AND METHODS

Twenty-nine ALL and 29 typically developing (TD) children were prospectively recruited (age 4-16 years) in the present study. Group differences in brain volumetric parameters, brain water diffusivities, and the ALPS index were evaluated after controlling for age, gender, and handedness. Furthermore, significant group-different parameters were correlated with clinical information using partial correlations analysis.

RESULTS

Lower Dxassoc and ALPS index, and increased CSF volume were found in pediatric ALL (all p_{FDR-corrected} < 0.05). Moreover, the ALPS index was negatively associated with the risk classification (r =  - 0.59, p_{FDR-corrected} = 0.04) in pediatric ALL.

CONCLUSIONS

Dysfunction of the glymphatic system and accumulation of CSF were presented in pediatric ALL without clinically diagnosed CNS infiltration. These novel findings suggested that the glymphatic system might be essential in the early-stage process of ALL CNS infiltration, which provides a new direction for exploring underlying mechanisms and early detection of pediatric ALL CNS infiltration.

KEY POINTS

• Lower Dxassoc and ALPS index, and increased CSF volume were found in pediatric ALL (all p_{FDR-corrected} < 0.05). • The ALPS index was negatively associated with the risk classification (r =  -0.59, p_{FDR-corrected} = 0.04) in pediatric ALL. • Dysfunction of the glymphatic system and accumulation of CSF were presented in pediatric ALL without clinically diagnosed CNS infiltration, which suggested that the ALPS index and CSF volume might be promising imaging markers for early detection of pediatric ALL CNS infiltration.

Quantitative IVIM parameters evaluating perfusion changes in brain parenchyma in patients newly diagnosed with acute leukemia: Compared with healthy participants

Purpose

To study the value of quantitative IVIM parameters in evaluating cerebral blood perfusion changes in patients newly diagnosed with acute leukemia (AL) by comparing them with healthy participants.

Materials and methods

This prospective study consecutively recruited 49 participants with newly diagnosed AL and 40 normal controls between July 2020 and September 2022. All participants underwent an MRI of the brain using an axial T₁-weighted and an IVIM sequence. The IVIM parameters (water diffusion coefficient, sADC, pseudoperfusion fraction, f; diffusion coefficient, D, pseudodiffusion coefficient, D ^*, and perfusion-diffusion ratio, PDR) and peripheral white blood cell (WBC) counts were obtained. An unpaired t-test or the Mann-Whitney U-test was performed to compare the differences in gray matter (GM) and white matter (WM) of healthy participants and AL patients and the differences in IVIM parameters between healthy participants and patients with AL. In addition, multivariate (logistic regression) analyses were used to identify independent predictors and then, the receiver operating characteristic curve (ROC) analyses were performed.

Results

40 healthy participants and 49 patients with newly diagnosed AL were evaluated. In healthy participants, sADC, PDR, D and f values of GM were significantly higher than those of WM (t = 5.844, t = 3.838, t = 7.711, z = -2.184, respectively, all P < 0.05). In AL patients, the D, f and sADC values of GM were significantly higher than those of WM (t = 3.450, t = 6.262, t = 4.053, respectively, all P < 0.05). The sADC and f value from AL patients were significantly lower than those from healthy participants in GM (z = -2.537, P = 0.011; and z = -2.583, P = 0.010, respectively) and WM (z = -2.969, P = 0.003; z = -2.923, P = 0.003, respectively). The WBC counts of AL patients were significantly higher than those of healthy participants (t = 3.147, P = 0.002). Multivariate analyses showed that the f values of GM and WM were independent predictors of AL (P = 0.030, and 0.010, respectively), with the optimal cut-off value at 7.08% (AUC ROC curve: 0.661, specificity: 11.4%, sensitivity: 98%) and 13.77% (AUC ROC curve: 0.682, specificity: 79.5%, sensitivity: 59.2%).

Conclusion

The IVIM parameters of brain parenchyma in patients newly diagnosed with AL differed from those of the healthy participants. The changes of cerebral blood flow perfusion are expected to provide new ideas for studying central nervous system infiltration in AL.

Therapeutic Monitoring of Orally Administered, Small-Molecule Anticancer Medications with Tumor-Specific Cellular Protein Targets in Peripheral Fluid Spaces-A Review

Orally administered, small-molecule anticancer drugs with tumor-specific cellular protein targets (OACD) have revolutionized oncological pharmacotherapy. Nevertheless, the differences in exposure to these drugs in the systemic circulation and extravascular fluid compartments have led to several cases of therapeutic failure, in addition to posing unknown risks of toxicity. The therapeutic drug monitoring (TDM) of OACDs in therapeutically relevant peripheral fluid compartments is therefore essential. In this work, the available knowledge regarding exposure to OACD concentrations in these fluid spaces is summarized. A review of the literature was conducted by searching Embase, PubMed, and Web of Science for clinical research articles and case reports published between 10 May 2001 and 31 August 2022. Results show that, to date, penetration into cerebrospinal fluid has been studied especially intensively, in addition to breast milk, leukocytes, peripheral blood mononuclear cells, peritoneal fluid, pleural fluid, saliva and semen. The typical clinical indications of peripheral fluid TDM of OACDs were (1) primary malignancy, (2) secondary malignancy, (3) mental disorder, and (4) the assessment of toxicity. Liquid chromatography-tandem mass spectrometry was most commonly applied for analysis. The TDM of OACDs in therapeutically relevant peripheral fluid spaces is often indispensable for efficient and safe treatments.

Case Report: Blinatumomab therapy for the treatment of B-cell acute lymphoblastic leukemia patients with central nervous system infiltration

The treatment of B-cell acute lymphoblastic leukemia (B-ALL) with central nervous system (CNS) involvement poses a significant clinical challenge because most chemotherapeutic agents exhibit weak permeability to the blood-brain barrier (BBB). In addition, current anti-CNS leukemia treatments often bring short or long-term complications. Immunotherapy including chimeric antigen T-cell therapy and bispecific antibody have shown profound treatment responses in relapsed/refractory B-ALL. However, there is a lack of data on the efficacy of bispecific antibody in treating B-ALL with CNS involvement. Here, we report two ALL patients with CNS leukemia who received blinatumomab. Case 1 was diagnosed with chronic myeloid leukemia in lymphoid blast phase. The patient developed CNS leukemia and bone marrow relapse during the treatment with dasatinib. Case 2 was diagnosed with B-ALL and suffered early hematologic relapse and cerebral parenchyma involvement. After treatment with one cycle of blinatumomab, both patients achieved complete remission in the bone marrow and CNS. Furthermore, this is the first report on the efficacy of blinatumomab in treating CNS leukemia with both of the cerebral spinal fluid and the cerebral parenchymal involvement. Our results suggest that blinatumomab might be a potential option for the treatment of CNS leukemia.

Nanopore sequencing of clonal IGH rearrangements in cell-free DNA as a biomarker for acute lymphoblastic leukemia

Background

Acute Lymphoblastic Leukemia (ALL) is the most common pediatric cancer, and patients with relapsed ALL have a poor prognosis. Detection of ALL blasts remaining at the end of treatment, or minimal residual disease (MRD), and spread of ALL into the central nervous system (CNS) have prognostic importance in ALL. Current methods to detect MRD and CNS disease in ALL rely on the presence of ALL blasts in patient samples. Cell-free DNA, or small fragments of DNA released by cancer cells into patient biofluids, has emerged as a robust and sensitive biomarker to assess cancer burden, although cfDNA analysis has not previously been applied to ALL.

Methods

We present a simple and rapid workflow based on NanoporeMinION sequencing of PCR amplified B cell-specific rearrangement of the (IGH) locus in cfDNA from B-ALL patient samples. A cohort of 5 pediatric B-ALL patient samples was chosen for the study based on the MRD and CNS disease status.

Results

Quantitation of IGH-variable sequences in cfDNA allowed us to detect clonal heterogeneity and track the response of individual B-ALL clones throughout treatment. cfDNA was detected in patient biofluids with clinical diagnoses of MRD and CNS disease, and leukemic clones could be detected even when diagnostic cell-count thresholds for MRD were not met. These data suggest that cfDNA assays may be useful in detecting the presence of ALL in the patient, even when blasts are not physically present in the biofluid sample.

Conclusions

The Nanopore IGH detection workflow to monitor cell-free DNA is a simple, rapid, and inexpensive assay that may ultimately serve as a valuable complement to traditional clinical diagnostic approaches for ALL.

Central nervous system involvement in childhood acute lymphoblastic leukemia: challenges and solutions

Delivery of effective anti-leukemic agents to the central nervous system (CNS) is considered essential for cure of childhood acute lymphoblastic leukemia. Current CNS-directed therapy comprises systemic therapy with good CNS-penetration accompanied by repeated intrathecal treatments up to 26 times over 2-3 years. This approach prevents most CNS relapses, but is associated with significant short and long term neurotoxicity. Despite this burdensome therapy, there have been no new drugs licensed for CNS-leukemia since the 1960s, when very limited anti-leukemic agents were available and there was no mechanistic understanding of leukemia survival in the CNS. Another major barrier to improved treatment is that we cannot accurately identify children at risk of CNS relapse, or monitor response to treatment, due to a lack of sensitive biomarkers. A paradigm shift in treating the CNS is needed. The challenges are clear - we cannot measure CNS leukemic load, trials have been unable to establish the most effective CNS treatment regimens, and non-toxic approaches for relapsed, refractory, or intolerant patients are lacking. In this review we discuss these challenges and highlight research advances aiming to provide solutions. Unlocking the potential of risk-adapted non-toxic CNS-directed therapy requires; (1) discovery of robust diagnostic, prognostic and response biomarkers for CNS-leukemia, (2) identification of novel therapeutic targets combined with associated investment in drug development and early-phase trials and (3) engineering of immunotherapies to overcome the unique challenges of the CNS microenvironment. Fortunately, research into CNS-ALL is now making progress in addressing these unmet needs: biomarkers, such as CSF-flow cytometry, are now being tested in prospective trials, novel drugs are being tested in Phase I/II trials, and immunotherapies are increasingly available to patients with CNS relapses. The future is hopeful for improved management of the CNS over the next decade.

Immunotherapy approaches for hematological cancers

Hematological cancers such as leukemia, lymphoma, and multiple myeloma have traditionally been treated with chemo and radiotherapy approaches. Introduction of immunotherapies for treatment of these diseases has led to patient remissions that would not have been possible with traditional approaches. In this critical review we identify main disease characteristics, symptoms, and current treatment options. Five common immunotherapies, namely checkpoint inhibitors, vaccines, cell-based therapies, antibodies, and oncolytic viruses, are described, and their applications in hematological cancers are critically discussed.

Selective Inhibition of Bruton's Tyrosine Kinase by a Designed Covalent Ligand Leads to Potent Therapeutic Efficacy in Blood Cancers Relative to Clinically Used Inhibitors

Bruton's tyrosine kinase (BTK) is a member of the TEC-family kinases and crucial for the proliferation and differentiation of B-cells. We evaluated the therapeutic potential of a covalent inhibitor (JS25) with nanomolar potency against BTK and with a more desirable selectivity and inhibitory profile compared to the FDA-approved BTK inhibitors ibrutinib and acalabrutinib. Structural prediction of the BTK/JS25 complex revealed sequestration of Tyr551 that leads to BTK's inactivation. JS25 also inhibited the proliferation of myeloid and lymphoid B-cell cancer cell lines. Its therapeutic potential was further tested against ibrutinib in preclinical models of B-cell cancers. JS25 treatment induced a more pronounced cell death in a murine xenograft model of Burkitt's lymphoma, causing a 30-40% reduction of the subcutaneous tumor and an overall reduction in the percentage of metastasis and secondary tumor formation. In a patient model of diffuse large B-cell lymphoma, the drug response of JS25 was higher than that of ibrutinib, leading to a 64% "on-target" efficacy. Finally, in zebrafish patient-derived xenografts of chronic lymphocytic leukemia, JS25 was faster and more effective in decreasing tumor burden, producing superior therapeutic effects compared to ibrutinib. We expect JS25 to become therapeutically relevant as a BTK inhibitor and to find applications in the treatment of hematological cancers and other pathologies with unmet clinical treatment.

Multifaceted role of chemokines in solid tumors: From biology to therapy

Chemokines are small secretory chemotactic cytokines that control the directed migration of immune cells. Chemokines are involved in both anti-and pro-tumorigenic immune responses. Accumulating evidence suggests that the balance between these responses is influenced by several factors such as the stage of tumorigenesis, immune cell activation, recruitment of immune activating or immunosuppressive cells in the tumor microenvironment (TME), and chemokine receptor expression on effector and regulatory target cells. Cancer cells engage in a complex network with their TME components via several factors including growth factors, cytokines and chemokines that are critical for the growth of primary tumor and metastasis. However, chemokines show a multifaceted role in tumor progression including maintenance of stem-like properties, tumor cell proliferation/survival/senescence, angiogenesis, and metastasis. The heterogeneity of solid tumors in primary and metastatic cancers presents a challenge to the development of successful cancer therapy. Despite extensive research on how solid tumors escape immune cell-mediated anti-tumor response, finding an effective therapy for metastatic cancer still remains a challenge. This review discusses the multifarious roles of chemokines in solid tumors including various chemokine signaling pathways such as CXCL8-CXCR1/2, CXCL9, 10, 11-CXCR3, CXCR4-CXCL12, CCL(X)-CCR(X) in primary and metastatic cancers. We further discuss the novel therapeutic approaches that have been developed by major breakthroughs in chemokine research to treat cancer patients by the strategic blockade/activation of these signaling axes alone or in combination with immunotherapies.

Interactome based identification and validation of prefoldin 5-α for prognosing CNS leukemia in B-ALL patients

We report here the identification and validation of prefoldin 5-alpha (PFDN5-α) for the first time as prognostic biomarker for prediction of central nervous system (CNS) leukemia of B cell acute lymphoblastic leukemia (B-ALL) origin. Since cerebrospinal fluid (CSF) cytology being the gold standard of diagnosis for CNS leukemia with poor sensitivity, mandatory prophylactic intrathecal chemotherapy is administered irrespective of patients develop CNS leukemia. Thus, using interactome studies, we identified PFDN5-α as a prognostic biomarker for predicting CNS leukemia by interacting lymphoblastic proteins and CSF from B-ALL patients using far-western clinical proteomics approach. Validation by both western and ELISA methods confirmed our results. For further clinical translation, we performed Receiver Operating Characteristic (ROC) curve analysis generated from CNS +ve (n = 25) and −ve (n = 40) CSF samples from B-ALL patients and identified PFDN5-α-CSF reactivity cut-off value as 0.456. Values below 0.456 indicate the patient is at risk of developing CNS leukemia and suggestive of having intrathecal chemotherapy. Further flow cytometry validation for CNS leukemia positivity revealed that with increasing blast cells, a decrease in PFDN5-α-CSF reactivity confirming ELISA based PFDN5α-CSF reactivity assay. Predicting CNS leukemia development risk by ELISA based PFDN5-α-CSF reactivity assay could have potential in the clinical management of CNS leukemia.

Towards updated understanding of brain metastasis

Brain metastasis (BM) is a common complication in cancer patients with advanced disease and attributes to treatment failure and final mortality. Currently there are several therapeutic options available; however these are only suitable for limited subpopulation: surgical resection or radiosurgery for cases with a limited number of lesions, targeted therapies for approximately 18% of patients, and immune checkpoint inhibitors with a response rate of 20-30%. Thus, there is a pressing need for development of novel diagnostic and therapeutic options. This overview article aims to provide research advances in disease model, targeted therapy, blood brain barrier (BBB) opening strategies, imaging and its incorporation with artificial intelligence, external radiotherapy, and internal targeted radionuclide theragnostics. Finally, a distinct type of BM, leptomeningeal metastasis is also covered.

Neurological Involvement in Pediatric Patients with Acute Leukemia: A Retrospective Cohort

Acute leukemia (AL) is an important cause of morbidity and mortality in children, and neurological manifestations (NM) are frequent. The objective of this study was to analyze neurological manifestations in children with acute leukemia from cases attended in the last five years at the Centro Médico Nacional “20 de Noviembre”. Methods: Conducting a retrospective and analytical study from 1 January 2015 to 31 December 2020 in children with AL classified according to sex, age range and AL type. Participants were grouped according the presence of NM. Results: We analyzed 607 patients: 54.85% boys and 44.14% girls, with a mean age of 7.27 ± 4.54 years. When comparing groups, the NM group was significantly older (p = 0.01), and the highest prevalence was between 6 and 12 years old. ALL was predominant over the other lineages (p ≤ 0.01). The most frequent NM was CNS infiltration, seizures, headache and neuropathy. Death outcomes occurred in 18.7% of children with AML, 11.8% with ALL and 50% with MPAL (p ≤ 0.002). The NM group was associated with higher mortality during a follow-up time of 77.9 ± 49 months (44.4% vs. 8.9% deaths, NM vs. non-NM, respectively; OR = 3.3; 95% CI 2.4 to 4.6; p ≤ 0.0001). Conclusions: ALL was the most prevalent leukemia type. CNS infiltration, seizures, headache, neuropathy and PRES were the most frequent symptoms in the NM group. NM was associated with a higher mortality rate.

Does minimal central nervous system involvement in childhood acute lymphoblastic leukemia increase the risk for central nervous system toxicity?

Central nervous system (CNS) involvement in childhood acute lymphoblastic leukemia (ALL) implicates enhanced intrathecal chemotherapy, which is related to CNS toxicity. Whether CNS involvement alone contributes to CNS toxicity remains unclear. We studied the occurrence of all CNS toxicities, seizures, and posterior reversible encephalopathy syndrome (PRES) in children with ALL without enhanced intrathecal chemotherapy with CNS involvement (n = 64) or without CNS involvement (n = 256) by flow cytometry. CNS involvement increased the risk for all CNS toxicities, seizures, and PRES in univariate analysis and, after adjusting for induction therapy, for seizures (hazard ratio [HR] = 3.33; 95% confidence interval [CI]: 1.26-8.82; p = 0.016) and PRES (HR = 4.85; 95% CI: 1.71-13.75; p = 0.003).

Flow Cytometric Detection of Malignant Blasts in Cerebrospinal Fluid: A Biomarker of Central Nervous System Involvement in Childhood Acute Lymphoblastic Leukemia

Despite the excellent prognosis for children and adolescents with acute lymphoblastic lymphoma (ALL), the involvement of the central nervous system (CNS) represents a major therapeutic challenge. Patients who develop CNS relapse have a very poor prognosis, and since current methods cannot reliably identify patients with CNS involvement or patients at high risk of CNS relapse, all children with ALL receive CNS-directed treatment. The current golden standard for detecting CNS involvement is the assessment of cytomorphology on cytospin slides of cerebrospinal fluid (CSF). This technique is inadequate due to low sensitivity and reproducibility. Flow cytometric analysis of CSF represent a novel, highly specific and sensitive technique for the detection of leukemic cells in the CNS. In prospective studies, CSF flow cytometry demonstrated two to three times higher rates of CNS involvement at diagnosis of childhood ALL than conventional cytospin, and especially demonstrated superior sensitivity in detecting low-level CNS disease. CNS involvement determined via flow cytometry has been linked to a higher risk of CNS relapse and poor outcomes in several studies. In this review, we discuss the central analytical concepts of CSF flow cytometry and summarize the current evidence supporting the use of flow cytometric detection of malignant blasts as a biomarker of CNS involvement in childhood ALL.

Malignant invasion of the cerebrospinal fluid in adult and paediatric patients with haematological and solid malignancies: a monocentric retrospective study

OBJECTIVES

In this study, we describe the clinical presentation, the cerebrospinal fluid (CSF) characteristics and outcome of children and adults with leptomeningeal invasion due to haematological and solid malignancies.

METHODS

Routine CSF samples analyzed from 2008 to 2018 at our institution were retrospectively reviewed for the presence of malignant cells based on cytomorphological analysis.

RESULTS

Leptomeningeal invasion was identified in 212 patients: 45 children versus 167 adults, and 92 haematological versus 120 solid malignancies. Leukaemic invasion in childhood was mainly due to ALL, and lymphoma invasion was often due to a high-grade B-cell lymphoma in adults. Metastatic invasion by solid tumours was almost exclusively seen in adults. Patients suffered most frequently from cranial neuropathy and headache (both 32%), while asymptomatic presentations were seen mainly in children (33%) and haematological malignancies (17%). Laboratory CSF parameters often showed an elevated WBC count (87%), total protein (74%) and lactate (76%) and a decreased glucose (77%). These deviations were especially found in solid malignancies (>84%) and adults (>82%). Brain and/or spinal cord imaging was more often suggestive for the leptomeningeal invasion in solid than in haematological malignancies (86% vs. 46%). The 5-year overall survival (OS) rates for patients with haematological and solid malignancies were 21.5% and 5.9%, respectively. The 5-year OS rate for children (55.6%) was significantly better than for adults (3.5%).

CONCLUSION

Leptomeningeal invasion is more often asymptomatic, and CSF parameters and imaging are more often normal in children and haematological malignancies than in adults and solid malignancies, possibly leading to underdiagnosis.

Linear and Circular Long Non-Coding RNAs in Acute Lymphoblastic Leukemia: From Pathogenesis to Classification and Treatment

The coding regions account for only a small part of the human genome, and the remaining vast majority of the regions generate large amounts of non-coding RNAs. Although non-coding RNAs do not code for any protein, they are suggested to work as either tumor suppressers or oncogenes through modulating the expression of genes and functions of proteins at transcriptional, posttranscriptional and post-translational levels. Acute Lymphoblastic Leukemia (ALL) originates from malignant transformed B/T-precursor-stage lymphoid progenitors in the bone marrow (BM). The pathogenesis of ALL is closely associated with aberrant genetic alterations that block lymphoid differentiation and drive abnormal cell proliferation as well as survival. While treatment of pediatric ALL represents a major success story in chemotherapy-based elimination of a malignancy, adult ALL remains a devastating disease with relatively poor prognosis. Thus, novel aspects in the pathogenesis and progression of ALL, especially in the adult population, need to be further explored. Accumulating evidence indicated that genetic changes alone are rarely sufficient for development of ALL. Recent advances in cytogenic and sequencing technologies revealed epigenetic alterations including that of non-coding RNAs as cooperating events in ALL etiology and progression. While the role of micro RNAs in ALL has been extensively reviewed, less attention, relatively, has been paid to other non-coding RNAs. Herein, we review the involvement of linear and circular long non-coding RNAs in the etiology, maintenance, and progression of ALL, highlighting the contribution of these non-coding RNAs in ALL classification and diagnosis, risk stratification as well as treatment.

Development of CAR T Cell Therapy in Children-A Comprehensive Overview

CAR T cell therapy has revolutionized immunotherapy in the last decade with the successful establishment of chimeric antigen receptor (CAR)-expressing cellular therapies as an alternative treatment in relapsed and refractory CD19-positive leukemias and lymphomas. There are fundamental reasons why CAR T cell therapy has been approved by the Food and Drug administration and the European Medicines Agency for pediatric and young adult patients first. Commonly, novel therapies are developed for adult patients and then adapted for pediatric use, due to regulatory and commercial reasons. Both strategic and biological factors have supported the success of CAR T cell therapy in children. Since there is an urgent need for more potent and specific therapies in childhood malignancies, efforts should also include the development of CAR therapeutics and expand applicability by introducing new technologies. Basic aspects, the evolution and the drawbacks of childhood CAR T cell therapy are discussed as along with the latest clinically relevant information.

Isolated CNS Relapse in 2 High-Risk B-cell Acute Lymphoblastic Leukemia Patients Following SARS-CoV-2 Infection

B-cell acute lymphoblastic leukemia (B-ALL) is the most common pediatric malignancy with a highly favorable overall prognosis. Central nervous system (CNS) relapse of B-ALL is relatively rare and is associated with inferior survival outcomes. We present two patients with B-ALL who developed isolated CNS relapse following confirmed infection with severe acute respiratory syndrome coronavirus 2. In addition to individual and disease factors, we posit that delays in therapy together with immune system modulation because of severe acute respiratory syndrome coronavirus 2 may account for these 2 cases of CNS relapsed B-ALL. We report on this clinical observation to raise awareness of this potential association.

Integrin α6-Targeted Molecular Imaging of Central Nervous System Leukemia in Mice

Central nervous system leukemia (CNS-L) is caused by leukemic cells infiltrating into the meninges or brain parenchyma and remains the main reason for disease relapse. Currently, it is hard to detect CNS-L accurately by clinically available imaging models due to the relatively low amount of tumor cells, confined blood supply, and the inferior glucose metabolism intensity. Recently, integrin α6-laminin interactions have been identified to mediate CNS-L, which suggests that integrin α6 may be a promising molecular imaging target for the detection of CNS-L. The acute lymphoblastic leukemia (ALL) cell line NALM6 stabled and transfected with luciferase was used to establish the CNS-L mouse model. CNS-L-bearing mice were monitored and confirmed by bioluminescence imaging. Three of our previously developed integrin α6-targeted peptide-based molecular imaging agents, Cy5-S5 for near-infrared fluorescence (NIRF), Gd-S5 for magnetic resonance (MR), and ¹⁸F-S5 for positron emission tomography (PET) imaging, were employed for the molecular imaging of these CNS-L-bearing mice. Bioluminescence imaging showed a local intensive signal in the heads among CNS-L-bearing mice; meanwhile, Cy5-S5/NIRF imaging produced intensive fluorescence intensity in the same head regions. Moreover, Gd-S5/MR imaging generated superior MR signal enhancement at the site of meninges, which were located between the skull bone and brain parenchyma. Comparatively, MR imaging with the clinically available MR enhancer Gd-DTPA did not produce the distinguishable MR signal in the same head regions. Additionally, ¹⁸F-S5/PET imaging also generated focal radio-concentration at the same head regions, which generated nearly 5-times tumor-to-background ratio compared to the clinically available PET radiotracer ¹⁸F-FDG. Finally, pathological examination identified layer-displayed leukemic cells in the superficial part of the brain parenchyma tissue, and immunohistochemical staining confirmed the overexpression of the integrin α6 within the lesion. These findings suggest the potential application of these integrin α6-targeted molecular imaging agents for the accurate detection of CNS-L.

Management of CNS Disease in Pediatric Acute Lymphoblastic Leukemia

PURPOSE OF REVIEW

The treatment of acute lymphoblastic leukemia (ALL) is one of the success stories of pediatric oncology, but challenges and questions remain, including the optimal approach to the treatment of central nervous system (CNS) leukemia. It is unclear why some children with ALL develop CNS leukemia and others do not, and there remains debate regarding optimal regimens for prophylaxis, upfront treatment, and the treatment of CNS relapses. These topics are especially important since both cranial radiation therapy (CRT) and intensive intrathecal therapy carry risks of both short- and long-term adverse effects. In this review, we aim to identify areas of ongoing debate on this topic, review the biology of CNS leukemia, and summarize clinical trial data that address some of these questions.

RECENT FINDINGS

Both retrospective and meta-analyses have demonstrated that few patients with ALL benefit from CRT as a component of CNS-directed treatment for de novo disease, allowing cooperative groups to greatly limit the number of patients undergoing CRT as part of their initial ALL regimens. More recent efforts are focusing on how best to assay for low levels of CNS disease at the time of diagnosis, as well as the biological drivers that may result in CNS leukemia in certain patients. Progress remains to be made in the identification and treatment of CNS leukemia in pediatric ALL. Advancements have occurred to limit the number of children undergoing CRT, but much has yet to be learned to better understand the biology of and risk factors for CNS leukemia, and novel approaches are required to approach CNS relapse of ALL.

Central Nervous System Prophylaxis and Treatment in Acute Leukemias

OPINION STATEMENT

Improvements in systemic therapy in the treatment of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) have improved patient outcomes and reduced the incidence of CNS relapse. However, management of patients with CNS disease remains challenging, and relapses in the CNS can be difficult to salvage. In addition to treatment with CNS-penetrant systemic therapy (high-dose methotrexate and cytarabine), intrathecal prophylaxis is indicated in all patients with ALL, however is not uniformly administered in patients with AML without high-risk features. There is a limited role for radiation treatment in CNS prophylaxis; however, radiation should be considered for consolidative treatment in patients with CNS disease, or as an option for palliation of symptoms. Re-examining the role of established treatment paradigms and investigating the role of radiation as bridging therapy in the era of cellular therapy, particularly in chemotherapy refractory patients, is warranted.

Prognostic significance of CNSL at diagnosis of childhood B-cell acute lymphoblastic leukemia: A report from the South China Children's Leukemia Group

OBJECTIVES

The prognostic significance of acute lymphoblastic leukemia (ALL) patients with central nervous system leukemia (CNSL) at diagnosis is controversial. We aimed to determine the impact of CNSL at diagnosis on the clinical outcomes of childhood B-cell ALL in the South China Children's Leukemia Group (SCCLG).

METHODS

A total of 1,872 childhood patients were recruited for the study between October 2016 and July 2021. The diagnosis of CNSL depends on primary cytological examination of cerebrospinal fluid, clinical manifestations, and imaging manifestations. Patients with CNSL at diagnosis received two additional courses of intrathecal triple injections during induction.

RESULTS

The frequency of CNLS at the diagnosis of B-cell ALL was 3.6%. Patients with CNSL at diagnosis had a significantly higher mean presenting leukocyte count (P = 0.002) and poorer treatment response (P <0.05) compared with non-CNSL patients. Moreover, CNSL status was associated with worse 3-year event-free survival (P = 0.030) and a higher risk of 3-year cumulative incidence of relapse (P = 0.008), while no impact was observed on 3-year overall survival (P = 0.837). Multivariate analysis revealed that CNSL status at diagnosis was an independent predictor with a higher cumulative incidence of relapse (hazard ratio = 2.809, P = 0.016).

CONCLUSION

CNSL status remains an adverse prognostic factor in childhood B-cell ALL, indicating that additional augmentation of CNS-directed therapy is warranted for patients with CNSL at diagnosis.

Role and Relevance of Cerebrospinal Fluid Cells in Diagnostics and Research: State-of-the-Art and Underutilized Opportunities

Cerebrospinal fluid (CSF) has recently experienced a revival in diagnostics and research. However, little progress has been made regarding CSF cell analysis. For almost a century, CSF cell count and cytomorphological examination have been central diagnostic parameters, with CSF pleocytosis as a hallmark finding of neuroinflammation and cytology offering valuable clues regarding infectious, autoimmune, and malignant aetiologies. A great deal of information, however, remains unattended as modern immune phenotyping technologies have not yet been broadly incorporated into routine CSF analysis. This is a serious deficit considering the central role of CSF cells as effectors in central nervous system (CNS) immune defence and autoimmune CNS processes, and the diagnostic challenges posed by clinically overlapping infectious and immune-mediated CNS diseases. Here, we summarize historical, specimen-intrinsic, methodological, and technical issues determining the state-of-the-art diagnostics of CSF cells and outline future perspectives for this underutilized window into meningeal and CNS immunity.

Metabolic Reprogramming and Cell Adhesion in Acute Leukemia Adaptation to the CNS Niche

Involvement of the Central Nervous System (CNS) in acute leukemia confers poor prognosis and lower overall survival. Existing CNS-directed therapies are associated with a significant risk of short- or long-term toxicities. Leukemic cells can metabolically adapt and survive in the microenvironment of the CNS. The supporting role of the CNS microenvironment in leukemia progression and dissemination has not received sufficient attention. Understanding the mechanism by which leukemic cells survive in the nutrient-poor and oxygen-deprived CNS microenvironment will lead to the development of more specific and less toxic therapies. Here, we review the current literature regarding the roles of metabolic reprogramming in leukemic cell adhesion and survival in the CNS.

Upregulation of leukemia-induced non-coding activator RNA (LUNAR1) predicts poor outcome in pediatric T-acute lymphoblastic leukemia

T-cell Acute Lymphoblastic Leukemia (T-ALL) accounts for around 10-15% of all lymphoblastic leukemia in children. Previous studies have proven that dysregulation of Leukemia-induced non-coding activator RNA-1 (LUNAR1) expression promotes T-ALL cell growth by enhancing the NOTCH1/IGF-1R signaling pathway. We aimed to investigate the prognostic value of LUNAR1 in pediatric T-ALL, in addition, to find out its association with NOTCH1 and IGF-1R. The LUNAR1, NOTCH1, and IGF-IR gene expression were measured in peripheral blood (PB) samples of l85 children with T-ALL and forty non-leukemic samples as a control group. Cox regression analysis revealed that overexpression of LUNAR1, NOTCH1, and IGF-IR was significantly correlated with poor prognosis, short overall survival, and progression-free survival. We concluded that LUNAR1 could serve as an independent prognostic biomarker for T-ALL in children.

Central nervous system (CNS) involvement has an adverse impact on survival in newly diagnosed adult acute lymphoblastic leukemia (ALL) assessed by flow cytometry

The role of CNS involvement detected by flow cytometry (FCM) in patients with acute lymphoblastic leukemia has been discussed previously; however, its impact on survival has not been described enough. We analyzed a retrospective cohort of newly diagnosed ALL adult patients who had a cerebrospinal fluid (CSF) analysis by FCM and conventional cytology. We evaluated 81 patients; 19 (23.4%) were only positive by FCM, five (6.3%) were double-positive (DP) and 57 (70.4%) were double-negative (DN). The detection of CNS involvement was increased from 6% to 24%, employing FCM; In our final analysis, patients with FCM + had a lower survival of 7.01 months [95% CI (5.90-8.24)], compared with 11.71 months [IC95% (9.49-13.94)] in the DN group (p = 0.03).

Factors associated with treatment response to CD19 CAR-T therapy among a large cohort of B cell acute lymphoblastic leukemia

CD19-targeted chimeric antigen receptor (CAR) T cell therapy has demonstrated striking responses among B cell acute lymphoblastic leukemia (B-ALL), but analyses of potential factors associated with poor response and relapse are lacking. Here, we summarize the long-term follow-up of 254 B-ALL treated with CD19 CAR-T cells from 5 clinical trials (NCT03173417, NCT02546739, and NCT03671460 retrospectively registered on May 23, 2017, March 1, 2018, and September 7, 2018, respectively, at www.clinicaltrials.gov ; ChiCTR-ONC-17012829, and ChiCTR1800016541 retrospectively registered on September 28, 2017, and June 7, 2018, at www.chictr.org.cn ). Our data showed that TP53 mutation, bone marrow blasts > 20%, prior CAR-T/blinatumomab treatment, and severe cytokine release syndrome (CRS) were associated with a lower complete remission (CR) rate while age, extramedullary disease, complex cytogenetics, history of prior transplant, prior courses of chemotherapy, CAR-T cell dose, and manufacturing source of the cellular product did not affect patients' CR rate. Risk factors related to leukemia-free survival (LFS) and overall survival (OS) were history of prior transplant, complex cytogenetics, TP53 mutation, severe CRS, neurotoxicity, and CAR-T therapy without consolidative allogeneic hematopoietic stem cell transplantation (allo-HSCT). Age and CAR-T cell dose did not influence LFS and OS. Patients with consolidative allo-HSCT after CAR-T therapy had a superior OS and LFS compared to those who did not. This benefit was also observed in both pediatric and adult patients as well as in patients either in high- or low-risk groups. This large study to identify risk factors of CR, LFS, and OS may help to maximize clinical outcomes of CAR-T therapy. Précis TP53 mutation and BM blasts > 20% are two independent factors associated with the CR rate. Patients with high tumor burden as well as those with bone marrow blasts < 5% can benefit from consolidative allo-HSCT post-CAR-T therapy.

Plasma levels of YKL-40 as a prognostic factor in childhood acute lymphoblastic leukemia

YKL-40, also known as chitinase-3-like protein 1 (CHI3L1), is an inflammatory glycoprotein secreted by different types of cells, such as inflammatory cells. The levels of this protein are elevated in the serum or plasma of patients with different types of cancer, and high concentrations are associated with poor prognosis and short survival in patients with liver, breast, lung, bladder and endometrial cancers. In Mexico, acute lymphoblastic leukemia (ALL) is the most common type of cancer affecting the pediatric population. The prognosis of patients with ALL is difficult to establish. Hence, the objective of the present study was to analyze the plasma levels of YKL-40 in Mexican children with ALL and investigate its role as a prognostic factor. A case-control study was performed in a population of 90 children aged 1-18 years, among whom 45 had ALL and 45 were hematologically healthy. The levels of YKL-40 in plasma samples were measured using ELISA and were found to be significantly higher in children with ALL compared with those in controls (P<0.0001). Children with ALL who had high plasma levels of YKL-40 (≥36.34 ng/ml) had shorter survival compared with those with low levels (<36.34 ng/ml; P<0.05). The findings of the present study revealed that the YKL-40 plasma level, age/initial leukocyte count and central nervous system invasion were associated with the prognosis of children with ALL [odds ratio (OR)=6.06, 95% confidence interval (CI): 1.1-31.6, P=0.03; OR=8.53, 95% CI: 1.2-58.2, P=0.03; and OR=6.45, 95% CI: 1.01-41.2, P=0.04, respectively]. Therefore, YKL-40 plasma levels may serve as a prognostic biomarker in pediatric patients with ALL.

Cerebrospinal Fluid Biomarkers in Childhood Leukemias

Involvement of the central nervous system (CNS) in childhood leukemias remains a major cause of treatment failures. Analysis of the cerebrospinal fluid constitutes the most important diagnostic pillar in the detection of CNS leukemia and relies primarily on cytological and flow-cytometry studies. With increasing survival rates, it has become clear that treatments for pediatric leukemias pose a toll on the developing brain, as they may cause acute toxicities and persistent neurocognitive deficits. Preclinical research has demonstrated that established and newer therapies can injure and even destroy neuronal and glial cells in the brain. Both passive and active cell death forms can result from DNA damage, oxidative stress, cytokine release, and acceleration of cell aging. In addition, chemotherapy agents may impair neurogenesis as well as the function, formation, and plasticity of synapses. Clinical studies show that neurocognitive toxicity of chemotherapy is greatest in younger children. This raises concerns that, in addition to injury, chemotherapy may also disrupt crucial developmental events resulting in impairment of the formation and efficiency of neuronal networks. This review presents an overview of studies demonstrating that cerebrospinal fluid biomarkers can be utilized in tracing both CNS disease and neurotoxicity of administered treatments in childhood leukemias.

CD79a promotes CNS-infiltration and leukemia engraftment in pediatric B-cell precursor acute lymphoblastic leukemia

Central nervous system (CNS) involvement remains a challenge in the diagnosis and treatment of acute lymphoblastic leukemia (ALL). In this study, we identify CD79a (also known as Igα), a signaling component of the preB cell receptor (preBCR), to be associated with CNS-infiltration and –relapse in B-cell precursor (BCP)-ALL patients. Furthermore, we show that downregulation of CD79a hampers the engraftment of leukemia cells in different murine xenograft models, particularly in the CNS.

Lenk et al find that the preB cell receptor (preBCR) is associated with infiltration and relapse of acute lymphoblastic leukemia in the central nervous system (CNS). They also show that downregulation of preBCR component CD79a reduces the engraftment of leukemia cells in different murine xenograft models, particularly in the CNS.