Background: Due to the lack of effective treatment options, the prognosis of patients with relapsed/refractory acute myeloid leukemia (R/R AML) remains poor. Although chimeric antigen receptor (CAR)-T-cell therapy has shown promising effects in acute lymphoblastic leukemia (ALL) and lymphoma, its application in R/R AML is limited by “off-target” effects, which lead to severe bone marrow suppression and limit its clinical application. CAR-natural killer (NK) cells not only exhibit antitumor effects but also demonstrate increased safety and universality. We have developed a new CAR construct that targets CD33 and modified NK cells, specifically eliminating AML cells while reducing severe side effects on stem cells. Methods: The CD33-targeting domain was selected by CAR-T cells, and this optimized CAR construct was subsequently transduced into umbilical cord-derived NK cells via a retroviral vector. Preclinical efficacy and safety studies were conducted both in vitro and in vivo. Ten eligible patients with R/R AML aged 18–65 years who received one or more infusions of anti-CD33 CAR-NK cells following the preconditioning regimen were enrolled. We assessed the response rates and treatment-related side effects post-infusion, while also documenting the long-term efficacy of the therapy. Results: The CD33 sequence was selected on the basis of its antitumor efficacy and safety in CAR-T-cell studies conducted both in vitro and in vivo. CD33 CAR-NK cells demonstrated efficacy comparable to that of CD33 CAR-T cells but showed limited toxicity to hematopoietic stem cells (HSCs). Ten patients, with a median of five prior lines of treatment, completed the efficacy evaluation (range, 3–8). No grade 3–4 adverse events were observed, except bone marrow suppression, which was relieved within one month. No cases of immune effector cell–associated neurotoxicity syndrome (ICANS) or graft-versus-host disease (GVHD) were reported following CAR-NK cell infusion. Only one patient experienced grade 2 cytokine release syndrome (CRS) and presented with persistent fever. By day 28, six of ten patients had achieved minimal residual disease (MRD)-negative complete remission. Conclusions: Our preclinical and clinical data demonstrated the primary efficacy and safety of CD33 CAR-NK cells for patients with R/R AML. Expanded samples and longer follow-up periods are needed to provide further efficacy data. Trial registration: NCT05008575 ( https://clinicaltrials.gov/study/NCT05008575 ).

Gap junctional intercellular communication (GJIC) is typically decreased in malignant tumors. Gap junction is not presented between hematopoietic cells but occurred in bone marrow stromal cells (BMSCs). Connexin 43 (Cx43) is the major gap junction (GJ) protein; our previous study revealed that Cx43 expression and GJIC were decreased in acute leukemic BMSCs. All-trans retinoic acid (ATRA) increases GJIC in a variety of cancer cells and has been used to treat acute promyelocytic leukemia, but the effects of ATRA on leukemic BMSCs is unknown. In this study, we evaluated the potential effects of ATRA on cell cycle, proliferation, and apoptosis of leukemic BMSCs. Effects of ATRA on Cx43 expression and GJIC were also examined. Human BMSCs obtained from 25 patients with primary acute leukemia, and 10 normal healthy donors were cultured. Effects of ATRA on cell cycle, cell proliferation, and apoptosis were examined with or without co-treatment with amphotericin-B. Cx43 expression was examined at both the mRNA and protein expression levels. GJIC was examined by using a dye transfer assay and measuring the rate of fluorescence recovery after photobleaching (FRAP). ATRA arrested the cell cycle progression, inhibited cell growth, and increased apoptosis in leukemic BMSCs. Both Cx43 expression and GJIC function were increased by ATRA treatment. Most of the observed effects mediated by ATRA were abolished by amphotericin-B pretreatment. ATRA arrests cell cycle progression in leukemic BMSCs, likely due to upregulating Cx43 expression and enhancing GJIC function.

As one of the most promising adoptive cell therapies, CAR-T cell therapy has achieved notable clinical effects in patients with hematological tumors. However, several treatment-related obstacles remain in CAR-T therapy, such as cytokine release syndrome, neurotoxicity, and high-frequency recurrence, which severely limit the long-term effects and can potentially be fatal. Therefore, strategies to increase the controllability and safety of CAR-T therapy are urgently needed. In this study, we engineered a genetic code expansion-based therapeutic system to achieve rapid CAR protein expression and regulation in response to cognate unnatural amino acids at the translational level. When the unnatural amino acid N-ε-((tert-butoxy) carbonyl)-l-lysine (BOCK) is absent, the CAR protein cannot be completely translated, and CAR-T is “closed”. When BOCK is present, complete translation of the CAR protein is induced, and CAR-T is “open”. Therefore, we investigated whether the BOCK-induced device can control CAR protein expression and regulate CAR-T cell function using a series of in vitro and in vivo experiments. First, we verified that the BOCK-induced genetic code expansion system enables the regulation of protein expression as a controllable switch. We subsequently demonstrated that when the system was combined with CAR-T cells, BOCK could effectively and precisely control CAR protein expression and induce CAR signaling activation. When incubated with tumor cells, BOCK regulated CAR-T cells cytotoxicity in a dose-dependent manner. Our results revealed that the presence of BOCK enables the activation of CAR-T cells with strong anti-tumor cytotoxicity in a NOG mouse model. Furthermore, we verified that the BOCK-induced CAR device provided NK cells with controllable anti-tumor activity, which confirmed the universality of this device. Our study systematically demonstrated that the BOCK-induced genetic code expansion system effectively and precisely regulates CAR protein expression and controls CAR-T cell anti-tumor effects in vitro and in vivo. We conclude that this controllable and reversible switch has the potential for more effective, secure, and clinically available CAR-based cellular immunotherapies.

The aim of this study was to investigate the clinical features and outcomes of elderly patients with acute myeloid leukemia (AML) from a real word research. The clinical data of 223 consecutive elderly patients (aged ≥ 60 years) who were newly diagnosed with AML at our medical center between July 2017 and June 2022, including their clinical characteristics, genetic mutations, and survival outcomes, were retrospectively analyzed. Among the 223 patients (median age 67 years), 180 (80.7%) were diagnosed with de novo AML. Genetic mutations were identified in 138 of 149 patients tested (92.6%). The most commonly mutated genes included TET2, DNMT3A, NPM1, FLT3-ITD, ASXL1, IDH2, RUNX1, TP53, and CEBPA. Among these genes, TET2, DNMT3A, FLT3-ITD, and TP53 were associated with a poor outcome. Multivariate Cox’s regression analysis revealed that age over 70 years, platelet count less than 100 × 10⁹/L, albumin level less than 35 g/L, presence of infection or bleeding at diagnosis, untreated or best supportive care (BSC) treatment status, and adverse or intermediate ELN 2022 risk classification were independent prognostic factors for overall survival in elderly AML patients. Patients who received at least one induction cycle had longer overall survival times (20 months vs. 6.6 months, P < 0.001) than those who received best supportive care. Patients with ≥ 6 cycles of chemotherapy had longer overall survival times (89.2% vs. 78.5%, P = 0.007) than those with ≤ 5 cycles of therapy. The results of this study indicated that elderly AML patients had multiple genetic abnormalities and poor outcomes. Regular effective treatment can improve patient outcomes and survival. In addition to genetic abnormalities, several other clinical features can influence survival in elderly AML patients.