Published papers

Acute myeloid leukemia (AML) is a hematologic malignancy which originates from leukemia initiating cells (LICs). Since LICs are considered to be resistant to standard chemotherapy, the identification of common mechanisms involved in LIC maintenance and progression is crucial to establishing broadly effective therapeutic agents for AML. The NF-κB pathway is one of the most promising targets, considering that its constitutive activation has been reported in different types of AML. In myeloid leukemia mouse models, we found that NF-κB activity is maintained specifically in LICs through autocrine TNF-α secretion, forming an NF-κB/TNF-α positive feedback loop. LICs had increased levels of active proteasome machinery, which promoted the degradation of IκBα and further supported NF-κB activity. Genetic ablation of TNF-α or NF-κB markedly suppressed leukemia progression in vivo. These findings demonstrate that NF-κB/TNF-α signaling in LICs contributes to leukemia progression and provide a widely applicable approach for targeting LICs.

Chimeric antigen receptor (CAR)-engineered T-cell therapy against B-cell malignancies and multiple myeloma was recently introduced for clinical use. However, the efficacy of CAR-T cell therapy is not durable in most patients, warranting the development of CAR-T cells with additional genetic modification or engineering of synthetic molecules to enhance their functions. This review will provide an overview of the molecular mechanisms underlying the functional alteration of T cells, especially transcriptional networks associated with memory formation and T cell exhaustion. In addition, methods to rationally improve CAR-T cell functions based on these mechanistic insights will be discussed.

The efficacy of adoptive immunotherapy using CD19-targeting chimeric antigen receptor (CAR)-engineered T cells against B-cell malignancies has already been established in the clinic. However, high economic costs and heterogeneous quality of CAR-T cells derived from individual patients hinder further expansion of their applicability to various cancer types, including solid tumors. Mass CAR-T cell production from healthy donors is a promising approach to overcome these problems, given that allogeneic immunity elicited against donor CAR-T cells by the recipient’s immune system is controlled. CAR-T cells genetically ablated with T-cell receptor and human leukocyte antigen molecules, referred to as universal CAR-T cells, may enable the use of allogeneic T cells for off-the-shelf adoptive cancer immunotherapy. However, several concerns, such as poor persistence of infused CAR-T cells and chromosomal abnormalities due to genome editing, remain to be addressed. Thus, recent clinical trials on universal CAR-T cells are summarized and future perspectives to overcome current challenges are discussed in this review.

T細胞に対する二重特異性抗体（BsAb）はCD3抗体を介して抗腫瘍活性をT細胞に賦与するが，長期的な治療効果は未だ不十分である。T細胞に最適な抗腫瘍効果を誘導するには複合的なシグナルが必要であり，我々はBsAb，共刺激分子，サイトカインなどの分子群を同時に表面に搭載したナノサイズの細胞膜由来膜小胞の作製技術を確立した。B細胞性造血器腫瘍に対し，CD19を標的としたBsAbに加え，共刺激分子（CD80，4-1BBL），T細胞の増殖・長期生存に関わるサイトカイン（IL-7，IL-15）を搭載した膜小胞は，T細胞に抗原特異的な抗腫瘍活性を効率よく誘導した。また抗PDL1抗体，CTLA4抗体，IL-12，IL-18など腫瘍微小環境に作用する分子を搭載し，腫瘍内マクロファージの改変や免疫抑制シグナルの解除を行えることを示した。この手法は従来の抗体医薬と比較して多面的な免疫制御シグナルを誘導できる。

Abstract Tumor-infiltrating lymphocyte (TIL) therapy is a type of adoptive immunotherapy potentially applicable to many types of solid tumors. Although gynecologic malignancies are promising targets for TIL therapy, its objective efficacy has not been established. Current TIL culture typically involves incubation of dissociated samples with high-dose IL-2 (HD-IL2) for weeks to enrich tumor-reactive T cells. While this protocol has been successfully used for melanoma TIL, it has not necessarily been optimized for other cancers. Here we investigated the method of efficiently expanding TILs derived from patients with gynecological cancers. TILs were incubated with HD-IL2 (HD-IL2-TILs) or stimulated with K562 cells expressing anti-CD3 mAb and CD80 (αCD3/CD80-TILs). We found that the αCD3/CD80-TILs showed significantly better proliferation than HD-IL2-TILs. The TIL populations that predominantly expanded upon αCD3/CD80 stimulation expressed high levels of PD-1 and CD28. CD28 co-stimulation was essential to overcome PD-1–mediated signals for growth suppression. We also identified DUSP4 as a negative regulator of TIL proliferation by downregulating ERK phosphorylation. The αCD3/CD80-TILs were reactive to tumor cells as shown by IFN-γ secretion and CD107a expression. Moreover, the αCD3/CD80-TILs were efficiently transduced with a chimeric cytokine receptor that we had previously developed to provide constitutive IL-7 signaling, resulting in superior in vivo persistence and antitumor effects without exogenous cytokine support in mouse models. Collectively, this study shows that direct stimulation of TILs with anti-CD3 mAb and CD28 co-stimulation achieves efficient expansion of tumor-reactive TILs. Genetic engineering of cytokine signaling in TILs may further enhance TIL functions and replace cytokine administration after TIL infusion.

Background While chimeric antigen receptor (CAR)-T cell therapy exhibits a robust therapeutic efficacy against B-cell malignancies and multiple myeloma, its efficacy and safety have not been established for acute myeloid leukemia (AML) and solid tumors due to the paucity of established target antigens. Some AML and solid tumor cells express tumor necrosis factor (TNF), which is initially expressed on the cell surface prior to shedding. Methods In this study, we obtained monoclonal antibodies against the N-terminal fragment of TNF (TNF-NTF) that remains on the cell surface after shedding. We then generated CAR-T cells to target TNF-NTF using the antibody sequence. To enhance the therapeutic efficacy of TNF-NTF CAR-T cells, we further engineered the previously developed chimeric cytokine receptor consisting of GP130, IL6R, and constitutively active IL7R with the M452L mutation (G6/7R). Results TNF-NTF CAR-T cells efficiently lysed TNF-expressing leukemia cells in vitro, while showing limited antitumor efficacy in vivo due to poor expansion and persistence. Activated T cells upregulate TNF, which was recognized by TNF-NTF CAR-T cells and led to fratricide. Genetic knockout (KO) of TNF significantly enhanced the viability and proliferation of TNF-NTF CAR-T cells, while slightly reducing their cytotoxic activity. In addition, ectopic expression of G6/7R improved the effector function of TNF-NTF CAR-T cells through constitutive activation of janus kinase (JAK)-signal transducers and activators of transcription (STAT) signaling. The G6/7R-expressing TNF-KO TNF-NTF CAR-T cells exhibited superior persistence and durable antileukemic efficacy in vivo compared with parental CAR-T cells. We also confirmed that TNF-NTF CAR-T cells can target primary AML cells, including a leukemia-initiating population with colony-forming capacity. Unlike CD33, targeting TNF-NTF did not show cytotoxicity against normal hematopoietic stem/progenitor cells. Finally, we demonstrated the curative efficacy of G6/7R TNF-KO TNF-NTF CAR-T cells against TNF-expressing ovarian tumor cells in vivo. Conclusions Our studies highlight TNF-NTF as a promising cell surface target for CAR-T cell therapy that can be applied to AML as well as solid tumors.

Providing cytokine signaling is a key strategy to boost the efficacy of chimeric antigen receptor (CAR) T cell therapy. However, the individual roles of key downstream mediators, STAT3 and STAT5, remain incompletely understood. In this study, we engineered CAR T cells to express constitutively active mutants of STAT3 (Y640F; caSTAT3) and STAT5 (N642H; caSTAT5) to investigate their individual functions. In vitro, caSTAT3 CAR T cells exhibited enhanced effector function and a robust memory phenotype, with broader transcriptional changes involving both effector and memory associated genes compared to caSTAT5 CAR T cells. However, caSTAT3 CAR T cells failed to expand due to activation of apoptosis-related gene programs. In contrast, caSTAT5 CAR T cells demonstrated sustained proliferation over time. Despite the limited in vitro expansion, caSTAT3 CAR T cells exhibited reduced transgene toxicity in vivo and exerted durable antitumor activity in both leukemia and solid tumor models without significant off-tumor toxicity. Titrated expression of caSTAT3 maintained enhanced effector function without inducing apoptosis. On the other hand, caSTAT5 CAR T cells efficiently accumulated in tumors but also infiltrated non-tumor tissues, causing lethal systemic toxicity. Coexpression of caSTAT3 and caSTAT5 markedly enhanced the long-term proliferative capacity of CAR T cells, even in the absence of antigen stimulation or cytokine supplementation. These findings elucidate the distinct impacts of STAT3 and STAT5 activation on CAR T cell behavior and suggest that selective activation of STAT3 at optimal levels may improve CAR T cell efficacy while minimizing off-tumor toxicities.

 Chimeric antigen receptor (CAR)-engineered T-cell therapy can induce a high remission rate for B-cell tumors and multiple myeloma. However, a significant number of patients experience a relapse after a transient response. To improve the efficacy of CAR-T cell therapy, genetic modification focused on epigenetic factors and cytokine signaling has been actively explored to confer long-lived potential and resistance to exhaustion of CAR-T cells. Studies are also underway to prevent or mitigate therapeutic toxicities, such as cytokine release syndrome, which inevitably increase in proportion to the therapeutic effect. In addition, the risk of developing T-cell malignancies after CAR T-cell therapy is better understood, and there is increasing interest in the long-term safety of the therapy. Here, I will review recent studies and future directions in CAR T-cell therapy with respect to the above perspectives.

 Chimeric antigen receptor (CAR)-engineered T cell therapy has shown significant efficacy against hematological malignancies; however, its long-term efficacy remains suboptimal. Furthermore, solid tumors are highly resistant to CAR-T cell therapy. Cytokine signaling is important for anti-tumor activity of T cells. Modulating cytokine signaling can improve the efficacy and safety of CAR-T cell therapy. We will review representative studies on manipulating CAR-T cell functions using cytokine signaling.

Hematopoietic cells differentiate through several progenitors in a hierarchical manner, and recent single-cell analyses have revealed substantial heterogeneity within each progenitor. Although common myeloid progenitors (CMPs) are defined as a multipotent cell population that can differentiate into granulocyte-monocyte progenitors (GMPs) and megakaryocyte-erythrocyte progenitors (MEPs), and GMPs generate neutrophils and monocytes, these myeloid progenitors must contain some lineage-committed progenitors. Through gene expression analysis at single-cell levels, we identified CD62L as a marker to reveal the heterogeneity. We confirmed that CD62L-negative CMPs represent "bona fide" CMPs, whereas CD62L-high CMPs are mostly restricted to GMP potentials both in mice and humans. In addition, we identified CD62L-negative GMPs as the most immature subsets in GMPs and Ly6C+CD62L-intermediate and Ly6C+CD62L-high GMPs are skewed to neutrophil and monocyte differentiation in mice, respectively. Our findings contribute to more profound understanding about the mechanism of myeloid differentiation.

T cell exhaustion is a main obstacle against effective cancer immunotherapy. Exhausted T cells include a subpopulation that maintains proliferative capacity, referred to as precursor exhausted T cells (TPEX). While functionally distinct and important for antitumor immunity, TPEX possess some overlapping phenotypic features with the other T-cell subsets within the heterogeneous tumor-infiltrating T-lymphocytes (TIL). Here we explore surface marker profiles unique to TPEX using the tumor models treated by chimeric antigen receptor (CAR)-engineered T cells. We find that CD83 is predominantly expressed in the CCR7+PD1+ intratumoral CAR-T cells compared with the CCR7-PD1+ (terminally differentiated) and CAR-negative (bystander) T cells. The CD83+CCR7+ CAR-T cells exhibit superior antigen-induced proliferation and IL-2 production compared with the CD83- T cells. Moreover, we confirm selective expression of CD83 in the CCR7+PD1+ T-cell population in primary TIL samples. Our findings identify CD83 as a marker to discriminate TPEX from terminally exhausted and bystander TIL.

Adoptive immunotherapy, in which tumor-reactive T cells are prepared in vitro for adoptive transfer to the patient, can induce an objective clinical response in specific types of cancer. In particular, chimeric antigen receptor (CAR)-redirected T-cell therapy has shown robust responses in hematologic malignancies. However, its efficacy against most of the other tumors is still insufficient, which remains an unmet medical need. Accumulating evidence suggests that modifying specific genes can enhance antitumor T-cell properties. Epigenetic factors have been particularly implicated in the remodeling of T-cell functions, including changes to dysfunctional states such as terminal differentiation and exhaustion. Genetic ablation of key epigenetic molecules prevents the dysfunctional reprogramming of T cells and preserves their functional properties.Clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)-based gene editing is a valuable tool to enable efficient and specific gene editing in cultured T cells. A number of studies have already identified promising targets to improve the therapeutic efficacy of CAR-T cells using genome-wide or focused CRISPR screening. In this review, we will present recent representative findings on molecular insights into T-cell dysfunction and how genetic modification contributes to overcoming it. We will also discuss several technical advances to achieve efficient gene modification using the CRISPR and other novel platforms.

T cell exhaustion is induced in the context of chronic virus infection and tumor microenvironment, in which cytotoxic T cells are repeatedly exposed to the target antigen and deprived of their effector functions. Multiple studies have already shown the significant impact of immune checkpoint molecules such as PD1 on functional properties of exhausted T cells. In addition to these signals, exhausted T cells possess distinct transcriptional and epigenetic profiles compared with conventional effector and memory T cells. Importantly, most of these features are not affected by immune checkpoint blockade, suggesting that genetic and epigenetic remodeling of T cells is an underlying molecular mechanism essential for T cell exhaustion. Moreover, it has now been evident that exhausted T cells are a heterogeneous cell population composed of distinct T cell subsets, and these functional differences profoundly affect therapeutic efficacy of cancer immunotherapy. In this review, I will discuss recent studies investigating molecular mechanisms of T cell exhaustion, including novel key molecules essentially associated with T cell exhaustion. These findings are potentially applicable to reinvigorate effector functions of exhausted T cells.

Abstract The efficient generation of chimeric antigen receptor (CAR) T cells is highly influenced by the quality of apheresed T cells. Healthy donor-derived T cells usually proliferate better than patients-derived T cells and are precious resources to generate off-the-shelf CAR-T cells. However, relatively little is known about the determinants that affect the efficient generation of CAR-T cells from healthy donor-derived peripheral blood mononuclear cells (PBMCs) compared with those from the patients’ own PBMCs. We here examined the efficiency of CAR-T cell generation from multiple healthy donor samples and analyzed its association with the phenotypic features of the starting peripheral blood T cells. We found that CD62L expression levels within CD8+ T cells were significantly correlated with CAR-T cell expansion. Moreover, high CD62L expression within naïve T cells was associated with the efficient expansion of T cells with a stem cell-like memory phenotype, an indicator of high-quality infusion products. Intriguingly, genetic disruption of CD62L significantly impaired CAR-T cell proliferation and cytokine production upon antigen stimulation. Conversely, ectopic expression of a shedding-resistant CD62L mutant augmented CAR-T cell effector functions compared to unmodified CAR-T cells, resulting in improved antitumor activity in vivo. Collectively, we identified the surface expression of CD62L as a concise indicator of potent T-cell proliferation. CD62L expression is also associated with the functional properties of CAR-T cells. These findings are potentially applicable to selecting optimal donors to massively generate CAR-T cell products.

BACKGROUND: A number of immunotherapeutic approaches have been developed and are entering the clinic. Bispecific antibodies (BsAbs) are one of these modalities and induce robust efficacy by endogenous T cells in several hematological malignancies. However, most of the treated patients experience only a temporary benefit. Currently available BsAbs provide only anti-CD3 antibody-mediated T-cell stimulation, but not the costimulation or cytokine signaling essential for full T-cell activation. Here, we hypothesized that the simultaneous input of more comprehensive signals would elicit more robust and durable effector T-cell functions. METHODS: We genetically engineered the leukemia cell line K562 to express BsAbs, costimulatory ligands, cytokines, and blocking antibodies against immune checkpoint molecules on the cell surface, from which we obtained plasma membrane fractions by mechanical homogenization and subsequent isolation steps. Plasma membranes were reconstituted on the poly (lactic-co-glycolic acid) surface to generate membrane-coated nanoparticles (NPs). Alternatively, nano-sized membrane vesicles (MVs) were generated by ultrasonic dispersion of the isolated membranes. The antitumor function of NPs and MVs loaded with various immunomodulatory factors was evaluated in vitro and in vivo. RESULTS: Both membrane-coated NPs and MVs induced BsAb-mediated antigen-specific cytotoxic activity in non-specific T cells, with MVs inducing a slightly better response in vivo. Importantly, T-cell activation was elicited only in the presence of target tumor cells, providing a safety advantage for clinical use. NPs and MVs expressing costimulatory molecules (CD80/4-1BBL) and cytokines (interleukin (IL)-7/IL-15) further enhanced effector T-cell function and induced therapeutic efficacy in vivo. In addition, MVs expressing immune checkpoint antibodies and inflammatory cytokines IL-12 and IL-18 induced objective antitumor responses in solid tumor models partly by converting immunosuppressive macrophages to proinflammatory phenotypes and inducing cytotoxic T-cell infiltration into the tumor. Finally, we showed that MVs were also engineered to activate natural killer (NK) cells by loading multiple ligands. MVs loaded with BsAbs, 4-1BBL, IL-15, and IL-21 induced NK-cell cytotoxic activity in an antigen-specific manner. CONCLUSIONS: We developed antitumor NPs and MVs that efficiently induced antitumor immune responses in vivo by simultaneously delivering multiple immunostimulatory signals to endogenous T cells. This platform enables the delivery of desired combinations of antitumor immune signals into T cells and NK cells.

Chimeric antigen receptor (CAR) T cell therapy often causes serious toxicities, such as cytokine release syndrome (CRS), mainly due to interleukin-6 (IL-6) secreted by monocyte lineage cells. Here, we describe a protocol to generate anti-CD19 CAR T cells and quantify human monocyte-derived IL-6 cocultured with CAR T cells and target tumor cells in vitro. We further describe a protocol to generate a humanized mouse model and evaluate CAR T cell-associated plasma IL-6 levels in vivo. For complete details on the use and execution of this protocol, please refer to Yoshikawa et al.1.

Chimeric antigen receptor(CAR)T-cell therapy has already been in the clinic due to its marked efficacy against several hematologic cancers. However, a significant number of patients relapse after a transient response, and the applicable diseases are still limited. Cytokine signaling is one of the most promising targets to enhance the therapeutic efficacy of CAR-T cells. At the same time, several cytokines are closely associated with toxicity, as exemplified by cytokine release syndrome. Here I will present representative findings on cytokines that have been shown to modulate CAR-T cell functions. I will also present our recent studies on how to simultaneously address efficacy and safety issues in CAR-T cell therapy. We will also briefly discuss CAR-NK cells, in which cytokines play an essential role.