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ABSTRACT Mesenchymal stromal cells (MSCs) are promising vehicles for delivering therapeutic agents to tumors, as a result of their tumor‐homing ability. This study aimed to develop MSCs expressing a trimeric soluble form of tumor necrosis factor‐related apoptosis‐inducing ligand (TRAIL), which was enhanced by incorporating an isoleucine zipper (SCZT), to improve apoptosis‐inducing efficacy. Because some cancer cells are resistant to TRAIL, we also investigated the effects of combining SCZT‐expressing MSCs with trichostatin A (TSA), a histone deacetylase inhibitor that enhances the expression of TRAIL death receptors (DR4/DR5) in tumor cells. TSA increased TRAIL sensitivity in resistant tumor cells in vitro by upregulating DR5, leading to enhanced caspase‐8 activation and tumor cell death. MSCs accumulated at tumor sites in vivo, and the combination of SCZT‐MSCs and TSA significantly suppressed tumor growth in both TRAIL‐sensitive and TRAIL‐resistant mouse models. Notably, this combination led to complete tumor regression in some TRAIL‐resistant tumors. These in vivo findings indicate that efficient tumor targeting by MSCs is crucial for achieving therapeutic efficacy, especially in TRAIL‐resistant tumors. Overall, our results demonstrate that co‐treatment with TSA enhances the antitumor effect of TRAIL‐expressing MSCs, offering a potential strategy to overcome TRAIL resistance and improve MSC‐based cancer therapies.

Multiple myeloma (MM) is an incurable hematological malignancy of plasma cells. Myeloma cells interfere with hematopoietic activities of the bone marrow, often leading to anemia, and can cause the bones to develop osteoporotic and lytic lesions. Clinical experience with chimeric antigen receptor T-cell (CAR-T) therapy targeting B-cell maturation antigen (BCMA) has been promising, with good response rates, favorable safety profiles, and low incidences of severe cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome. However, CAR-T therapy in MM is accompanied by several new challenges, including therapeutic failure and relapse, and much attention has been paid to the further development of B-cell maturation antigen-chimeric antigen receptor (BCMA-CAR). Although most of the reported benefits of BCMA-CAR have been discussed, whether cancer can be eliminated, as well as the efficacy of CAR-T therapy for anemia and bone lesions, both myeloma-defining events, have not yet been reported in any animal model. In this study, we designed and verified a novel BCMA-specific chimeric antigen receptor (CAR). Our BCMA-CAR demonstrated the fundamental properties of CAR-T cells, including target-specific cytotoxic activity, cytokine production, and in vivo antitumor effects. In addition, we evaluated the therapeutic effect of BCMA-CAR in mice by imaging bone lesions and conducting blood examinations. Tumor mouse models showed systemic progression of MM in the bone marrow, and mice treated with saline or nongene modified T cells showed continued tumor progression, progressive bone lesions, and prolonged anemia. In contrast, all mice treated with gene modified T cells achieved a complete response, improved anemia to the level observed in normal mice, and suppressed progression of bone lesions. We concluded that anemia was improved with BCMA-CAR-T cell therapy. However, novel strategies to support the recovery of bone lesions by enhancing CAR-T cell function must be developed.

It is established that neurogenesis of dentate gyrus is increased after ischemic insult, although the regulatory mechanisms have not yet been elucidated. In this study, we focused on Ezh2 which suppresses gene expression through catalyzing trimethylation of lysine 27 of histone 3. Male gerbils were injected with adeno-associated virus (AAV) carrying shRNA targeting to Ezh2 into right dentate gyrus 2 weeks prior to forebrain ischemia. One week after ischemia, animals were injected with thymidine analogue to label proliferating cells. Three weeks after ischemia, animals were killed for histological analysis. AAV-mediated knockdown of Ezh2 significantly decreased the ischemia-induced increment of proliferating cells, and the proliferated cells after ischemia showed significantly longer migration from subgranular zone (SGZ), compared to the control group. Furthermore, the number of neural stem cells in SGZ significantly decreased after ischemia with Ezh2 knockdown group. Of note, Ezh2 knockdown did not affect the number of proliferating cells or the migration from SGZ in the non-ischemic condition. Our data showed that, specifically after ischemia, Ezh2 knockdown shifted the balance between self-renewal and differentiation toward differentiation in adult dentate gyrus.

Abstract Objectives Multiple myeloma (MM) accounts for 10% of hematologic malignancies. However, most of the patients suffered from relapsed/refractory disease. We would like to expand CAR T cell therapy to treat MM using our current platform. Methods BCMA CAR T lymphocytes were generated for volunteers or MM patients. The transduction efficiency was detected by the ddPCR technique. Immunophenotyping and exhaustion markers were monitored by flow cytometry. The efficacy of BCMA CAR T cells was tested using coculturing with BCMA CAR or mock, and the positive and negative targets, K562/hBCMA‐ECTM and K562, respectively. Results BCMA CAR T cells were generated from consented volunteers or MM patients and could be detected CAR BCMA expression at a mean of 4.07 ± 1.95 or 4.65 ± 1.21 copies/cell, respectively. Those modified T cells were primarily effector memory T cells. Our BCMA CAR T cells could explicitly eradicate the K562/hBCMA‐ECTM cell line while the K562 cell line survived. Interestingly, the BCMA CAR, mock T cells, and peripheral blood mononuclear cells from MM patients expressed similar levels of the exhaustion makers, TIM‐3, LAG‐3, and PD1. Conclusions Our BCMA CAR T cells, mainly effector/effector memory, could eliminate BCMA‐expressing cells in vitro and had similar levels of exhaustion markers among different populations.