Targeting FLT3-specific chimeric antigen receptor T cells for acute lymphoblastic leukemia with KMT2A rearrangement.

CD19-specific chimeric antigen receptor T (CAR T) immunotherapy is used to treat B-cell malignancies. However, antigen-escape mediated relapse following CAR T therapy has emerged as a major concern. In some relapsed cases, especially KMT2A rearrangement-positive B-acute lymphoblastic leukemia (KMT2A-r B-ALL), most of the B-cell antigens are lost via lineage conversion to the myeloid phenotype, rendering multi-B-cell-antigen-targeted CAR T cell therapy ineffective. Fms-related tyrosine kinase-3 (FLT3) is highly expressed in KMT2A-r B-ALL; therefore, in this study, we aimed to evaluate the antitumor efficacy of CAR T cells targeting both CD19 and FLT3 in KMT2A-r B-ALL cells. We developed piggyBac transposon-mediated CAR T cells targeting CD19, FLT3, or both (dual) and generated CD19-negative KMT2A-r B-ALL models through CRISPR-induced CD19 gene-knockout (KO). FLT3 CAR T cells showed antitumor efficacy against CD19-KO KMT2A-r B-ALL cells both in vitro and in vivo; dual-targeted CAR T cells showed cytotoxicity against wild-type (WT) and CD19-KO KMT2A-r B-ALL cells, whereas CD19 CAR T cells demonstrated cytotoxicity only against WT KMT2A-r B-ALL cells in vitro. Therefore, targeting FLT3-specific CAR T cells would be a promising strategy for KMT2A-r B-ALL cells even with CD19-negative relapsed cases.

PiggyBac Transposon-Mediated CD19 Chimeric Antigen Receptor-T Cells Derived From CD45RA-Positive Peripheral Blood Mononuclear Cells Possess Potent and Sustained Antileukemic Function.

The quality of chimeric antigen receptor (CAR)-T cell products, namely, memory and exhaustion markers, affects the long-term functionality of CAR-T cells. We previously reported that piggyBac (PB) transposon-mediated CD19 CAR-T cells exhibit a memory-rich phenotype that is characterized by the high proportion of CD45RA+/C-C chemokine receptor type 7 (CCR7)+ T-cell fraction. To further investigate the favorable phenotype of PB-CD19 CAR-T cells, we generated PB-CD19 CAR-T cells from CD45RA+ and CD45RA- peripheral blood mononuclear cells (PBMCs) (RA+ CAR and RA- CAR, respectively), and compared their phenotypes and antitumor activity. RA+ CAR-T cells showed better transient gene transfer efficiency 24 h after transduction and superior expansion capacity after 14 days of culture than those shown by RA- CAR-T cells. RA+ CAR-T cells exhibited dominant CD8 expression, decreased expression of the exhaustion marker programmed cell death protein-1 (PD-1) and T-cell senescence marker CD57, and enriched naïve/stem cell memory fraction, which are associated with the longevity of CAR-T cells. Transcriptome analysis showed that canonical exhaustion markers were downregulated in RA+ CAR-T, even after antigen stimulation. Although antigen stimulation could increase CAR expression, leading to tonic CAR signaling and exhaustion, the expression of CAR molecules on cell surface after antigen stimulation in RA+ CAR-T cells was controlled at a relatively lower level than that in RA- CAR-T cells. In the in vivo stress test, RA+ CAR-T cells achieved prolonged tumor control with expansion of CAR-T cells compared with RA- CAR-T cells. CAR-T cells were not detected in the control or RA- CAR-T cells but RA+ CAR-T cells were expanded even after 50 days of treatment, as confirmed by sequential bone marrow aspiration. Our results suggest that PB-mediated RA+ CAR-T cells exhibit a memory-rich phenotype and superior antitumor function, thus CD45RA+ PBMCs might be considered an efficient starting material for PB-CAR-T cell manufacturing. This novel approach will be beneficial for effective treatment of B cell malignancies.

Infantile mediastinal neuroblastoma presenting as an oncologic emergency: usefulness of serum-based MYCN gene amplification analysis for risk stratification.

We reported two infantile cases of mediastinal neuroblastoma with life-threatening tracheal obstructions presenting as oncologic emergencies that were successfully treated per tentative risk classification using serum-based MYCN gene amplification (MNA) analysis. Tentative risk stratification based on age, tumour location and serum-based MNA status may be useful in patients with neuroblastoma presenting as oncologic emergencies who require urgent therapy stratification but for whom tumor-based molecular diagnoses cannot be established.

Early-onset parkinsonism in a pedigree with phosphoglycerate kinase deficiency and a heterozygous carrier: do PGK-1 mutations contribute to vulnerability to parkinsonism?

Phosphoglycerate kinase 1 (PGK-1) is a glycolytic enzyme encoded by PGK-1, which maps to the X chromosome. PGK-1 deficiency causes X-linked recessive hereditary chronic hemolytic anemia, myopathy, and neurological disorders due to insufficient ATP regeneration. Early-onset parkinsonism has occasionally been reported as a neurological complication of this condition. However, heterozygous carriers of PGK-1 deficiency were thought to be neurologically asymptomatic. Here, we report a boy with PGK-1 deficiency and his mother, a carrier of a heterozygous mutation in PGK-1, both of whom presented with early-onset parkinsonism. The boy developed parkinsonism at 9 years of age. His parkinsonism partially responded to levodopa treatment. 123l-metaiodobenzylguanidine (MIBG) uptake was normal. His mother, who exhibited normal PGK-1 activity in erythrocytes, developed parkinsonism at 36 years of age. Her symptoms were undistinguishable from those of Parkinson's disease (PD), despite her normal uptake of MIBG. Neither a point mutation in nor multiplication of SNCA was found. Additionally, hotspots of LRRK2 and GBA were not mutated. To our knowledge, this report provides the first description of parkinsonism in a carrier of PGK-1 deficiency. Interestingly, PGK-1 is located within the confirmed susceptibility locus for PD known as PARK12. These observations suggest that PGK-1 mutations confer susceptibility to PD.