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Humanized mouse models that have received human cells or tissue transplants are extremely useful in basic and applied human disease research. Highly immunodeficient mice, which do not reject xenografts and support cell and tissue differentiation and growth, are indispensable for generating additional appropriate models. Since the early 2000s, a series of immunodeficient mice appropriate for generating humanized mice has been successively developed by introducing the IL-2Rynull gene （e.g., NOD/SCID/7c＂uu and Rag2nu＂ycnun mice）. These strains show not only a high rate of human cell engraftment, but also generate well-differentiated multilineage human hematopoietic cells after human hematopoietic stem cell （HSC） transplantation. These humanized mice facilitate the analysis of human hematology and immunology in vivo. However, human hematopoietic cells developed from HSCs are not always phenotypically and functionally identical to those in humans. More recently, a new series of immunodeficient mice compensates for these disadvantages. These mice were generated by genetically introducing human cytokine genes into NODISCIDI？cn＂u and Rag2nulITcnUll mice. In this review, we describe the current knowledge of human hematopoietic cells developed in these mice. Various human disease mouse models using these humanized mice are summarized.

Cancer stem cells (CSCs) possess the capacity for self-renewal and the potential to differentiate into non-CSCs. The recent discoveries of dynamic equilibrium between CSCs and non-CSCs revealed the significance of acquiring CSC-like properties in non-CSCs as an important process in progression of cancer. The mechanism underlying acquisition of CSC-like properties has mainly been investigated in the context of epithelial–mesenchymal transition. Here, we demonstrate the dedifferentiation process may be an alternative mechanism in acquisition of CSC-like properties in human colorectal cancer cells. By exploring the single-cell gene expression analysis of organoids developed from CD44 + CSCs, we identified TWIST1 as a key molecule for maintaining the undifferentiated state of cancer cells. Consistent with the finding, we found that TGF-beta signaling pathway, a regulator of TWIST1, was specifically activated in the undifferentiated CD44 + CSCs in human colorectal cancer using microarray-based gene expression analysis and quantitative pathology imaging system. Furthermore, we showed that external stimulation with TGF-beta and the induction of TWIST1 converted CD44 − non-CSCs into the undifferentiated CD44 + CSCs, leading to the significant increment of CSCs in xenograft models. This study strongly suggests dedifferentiation driven by TGF-beta signaling enhances stem cell properties in human colorectal cancer.

Despite the success of immune checkpoint blockade (ICB) therapy for esophageal squamous cell cancer, the key immune cell populations that affect ICB efficacy remain unclear. Here, imaging mass cytometry of tumor tissues from ICB-treated patients identifies a distinct cell population of CD39 + PD-1 + CD8 + T cells, specifically the TCF1 + subset, precursor exhausted T (CD39 + Tpex) cells, which positively correlate with ICB benefit. CD39 + Tpex cells are predominantly in the stroma, while differentiated CD39 + exhausted T cells are abundantly and proximally within the parenchyma. Notably, CD39 + Tpex cells are concentrated within and around tertiary lymphoid structure (TLS). Accordingly, tumors harboring TLSs have more of these cells in tumor areas than tumors lacking TLSs, suggesting Tpex cell recruitment from TLSs to tumors. In addition, circulating CD39 + Tpex cells are also increased in responders following ICB therapy. Our findings show that this unique subpopulation of CD39 + PD-1 + CD8 + T cells is crucial for ICB benefit, and suggest a key role in TLS-mediated immune responses against tumors. Immune checkpoint blockade (ICB) benefits esophageal squamous cell cancer, but the immune cell mediators remain unclear. Here the author show, by imaging mass cytometry, that CD39 + CD8 + exhausted cells are present abundantly in both tertiary lymphoid tissue and tumor and correlate with responses to ICB.

Although the neutrophil to lymphocyte ratio (NLR) was reported to be a predictive biomarker for clinical outcomes in various types of cancer, including recurrent or metastatic head and neck cancer (R/M HNSCC) treated with nivolumab, the usefulness of the pretreatment C-reactive protein/albumin ratio (CAR) as a prognostic marker remains to be clarified. This study aimed to analyze the clinical usability of the CAR in comparison with that of the NLR. 46 R/M HNSCC patients treated with nivolumab were retrospectively analyzed. The optimal cutoff value for the CAR was calculated using receiver operating characteristic curve analysis. The optimal cutoff value for the CAR was set to 0.30. On multivariate analyses, a high CAR was significantly associated with poor overall survival (adjusted HR, 2.19; 95% CI, 1.42–3.47; p  < 0.01) and progression-free survival (adjusted HR, 1.98; 95% CI, 1.38–2.80; p  < 0.01). The overall response rate and disease control rate for the high CAR patients were lower than for the low CAR patients. The CAR had significantly higher area under the curve values than the NLR at 2 and 4 months. The pretreatment CAR might be an independent marker for prognosis and efficacy in R/M HNSCC patients treated with nivolumab.

Background Anti-PD-1 monoclonal antibody, nivolumab, has shown efficacy for advanced gastric cancer (AGC). However, the specific immune cell subsets predominantly activated during the period of anti-PD-1 therapy for AGC have not been clarified. Methods Peripheral blood of 30 AGC patients treated with nivolumab was prospectively obtained before the initial and second administrations and at the time of progressive disease (PD). The proportions of immune cell subsets and the serum concentrations of cytokines were systematically analysed by flow cytometry. Associations of subsets and serum cytokines with therapeutic effects were evaluated. Results After the initial administration, significant increases in activated central/effector memory, activated effector T cells, and activated T-helper 1 subsets were observed. At the time of PD, activated regulatory T cells, LAG3-positive CD4+/CD8+ T cells, and TIM3-positive CD4+/CD8+ T cells increased significantly. Significant positive correlations were shown between progression-free survival and proportions of LAG3-positive CD4+/CD8+ T cells and of OX40-positive CD4+/CD8+ T cells (log-rank p  = 0.0008, 0.0003, 0.0035 and 0.0040). Conclusions Nivolumab therapy enhances activation of central/effector memory and effector subsets of CD4+/CD8+ T cells. The expression levels of LAG-3 and OX40 on T cells correlated with the efficacy of nivolumab therapy and could be reasonable biomarkers for anti-PD-1 therapy.

We generated a novel mouse strain expressing transgenic human interleukin-15 (IL-15) using the severe immunodeficient NOD/Shi- scid -IL-2Rγ null (NOG) mouse genetic background (NOG-IL-15 Tg). Human natural killer (NK) cells, purified from the peripheral blood (hu-PB-NK) of normal healthy donors, proliferated when transferred into NOG-IL-15 Tg mice. In addition, the cell number increased, and the hu-PB-NK cells persisted for 3 months without signs of xenogeneic graft versus host diseases (xGVHD). These in vivo -expanded hu-PB-NK cells maintained the original expression patterns of various surface antigens, including NK receptors and killer cell immunoglobulin-like receptor (KIR) molecules. They also contained significant amounts of granzyme A and perforin. Inoculation of K562 leukemia cells into hu-PB-NK-transplanted NOG-IL-15 Tg mice resulted in significant suppression of tumor growth compared with non-transplanted mice. Furthermore, NOG-IL-15 Tg mice allowed for engraftment of in vitro -expanded NK cells prepared for clinical cell therapy. These cells exerted antibody-dependent cell-mediated cytotoxicity (ADCC) on Her2-positive gastric cancer cells in the presence of therapeutic anti-Her2 antibody, and subsequently suppressed tumor growth. Our results collectively suggest that the NOG-IL-15 Tg mice are a useful model for studying human NK biology and evaluating human NK cell-mediated in vivo cytotoxicity.

Cell line‐derived xenograft (CDX) models created by implanting cancer cell lines into immunodeficient mice have contributed largely to the development of cancer drug therapies. However, cell lines often lose their original biological characteristics through many passages and cancer tissues in CDX models have many cancer cells and few cancer stromal cells, therefore CDX models are currently considered not suitable for predicting the results of clinical studies. Conversely, patient‐derived xenograft (PDX) models are gaining importance, as human cancer biological characteristics and microenvironments are recreated by implanting tumor tissue into immunodeficient mice. These highly expected, evidently beneficial PDX models have been used in some basic research and are becoming more generalized. However, quality control and quality assurance criteria have not been established for them, and challenges and problems in the utilization of valuable PDX models in drug development have yet to be clarified. In this report, we conducted a questionnaire survey among researchers in Japanese academic institutions and pharmaceutical companies to understand the current status of PDX models in Japan. Based on the questionnaire results, we summarized the situations surrounding respondent's utilization and quality control in the development of anticancer drugs and proposed several measures to facilitate the utilization of PDX models in the development of anticancer drugs. We conducted a questionnaire survey among researchers in Japanese academic institutions and pharmaceutical companies to understand the current status of PDX models in Japan. Based on the results of the survey, we proposed several measures to facilitate the utilization of PDX models in the development of anticancer drugs. It is hoped that this report provides information to undertake research using PDX models for the development of anticancer drugs.

Bone marrow (BM) is the primary site of postnatal hematopoiesis, yet how it is established during embryogenesis remains poorly understood. BM formation is initiated by the invasion of vascular and mesenchymal cells into a preformed cartilage template, generating the primary ossification center (POC). Here, we identify CD55 + CD90 + mesenchymal cells as early regulators of osteoclastogenesis within the POC. These cells share a matrix-degrading transcriptional program with FABP5 + septoclasts that localize to the chondro-osseous interface of developing bone. Fate-mapping analyses reveal that CD55 + CD90 + cells transiently give rise to septoclasts during perinatal development, whereas osteoclast-supporting activity is subsequently assumed by LepR + bone marrow stromal cells (BMSCs). During fracture repair, FABP5 + septoclasts and LepR + BMSCs are redeployed within the callus, indicating reactivation of a developmental osteogenic program. Together, our findings uncover a conserved mechanism that links skeletal remodeling to the establishment of the BM microenvironment required for hematopoiesis. This study shows that fetal bone marrow cavity expansion is orchestrated by a previously unrecognized RANKL-producing niche comprising FABP5 + cells at early chondro-osseous border and BMSCs in marrow, a mechanism recapitulated during fracture repair.

The status of humoral immunity of cancer patients is not clear compared to cellular immunity because the ability of specific antibody production is difficult to analyze in vitro. We previously developed a humanized mouse model to evaluate antigen-specific antibody production by transplanting human peripheral blood mononuclear cells (PBMCs) into NOG-hIL-4-Tg mice (hu-PBL hIL-4 NOG). In this study, these mice were transplanted with PBMCs derived from breast cancer patients (BC) and immunized with a human epidermal growth factor receptor 2 (HER2) peptide, CH401MAP, to analyze humoral immunity of BCs. The hu-PBL hIL-4 NOG mice recapitulated immune environment of BCs as the ratio of CD8+/CD4+T cells was lower and that of PD-1 + T cells was higher compared to healthy donors (HDs). Diverse clusters were detected in BC-mouse (BC-M) plasma components involving immunoglobulins and complements unlike HD-M, and there was a significant diversity in CH401MAP-specific IgG titers in BC-M. The number of B cell clones producing high CH401MAP-specific IgG was not increased by immunization in BC-M unlike HD-M. These results demonstrated that the humoral immunity of BCs appeared as diverse phenotypes different from HDs in hu-PBL hIL-4 NOG mice, which may provide important information for the study of personalized medicine.

Immunodeficient mice engrafted with human peripheral blood cells are promising tools for in vivo analysis of human patient individual immune responses. However, when human peripheral blood mononuclear cells (PBMCs) are transferred into NOG (NOD/Shi-scid, IL-2rg null ) mice, severe graft versus host disease (GVHD) hinders long term detailed analysis. Administration of human PBMCs into newly developed murine MHC class I- and class II-deficient NOG (NOG-dKO; NOG- Iab, B2m-double-knockout) mice showed sufficient engraftment of human immune cells with little sign of GVHD. Immunization with influenza vaccine resulted in an increase in influenza-specific human IgG Ab, indicating induction of antigen-specific B cells in the NOG-dKO mice. Immunization with human dendritic cells pulsed with HLA-A2 restricted cytomegalovirus peptide induced specific cytotoxic T cells, indicating the induction of antigen-specific T cells in the NOG-dKO mice. Adoptive cell therapies (ACTs) using melanoma antigen recognized by T cells (MART-1)-specific TCR-transduced activated T cells showed strong tumor growth inhibition in NOG-dKO mice without any sign of GVHD accompanied by preferential expansion of the transferred MART-1-specific T cells. ACTs using cultured human melanoma infiltrating T cells also showed anti-tumor effects against autologous melanoma cells in NOG-dKO mice, in which changes in human cancer phenotypes by immune intervention, such as increased CD271 expression, could be evaluated. Therefore, NOG-dKO mice are useful tools for more detailed analysis of both the induction and effector phases of T-cell and B-cell responses for a longer period than regular NOG mice.