Etsuko Fujii

Interferon-α enhances CD317 expression and the antitumor activity of anti-CD317 monoclonal antibody in renal cell carcinoma xenograft models

A murine (mAHM) and a humanized (AHM) monoclonal antibody against CD317 (also called tetherin, BST2, or HM1.24 antigen), expressed preferentially in neoplastic B cells such as multiple myeloma, exhibited antitumor effects as a result of antibody‐dependent cellular cytotoxicity (ADCC). The putative interferon (IFN) response elements IRF‐1/2 and ISGF3 are present in the promoter of the CD317 gene, and IFN has been used for the treatment of not only myeloproliferative diseases but also solid tumors such as renal cell carcinoma (RCC) and melanoma. Therefore, we examined the effects of IFN on the expression of CD317 and on the antitumor activity of AHM and mAHM in RCC and melanoma. Flow cytometry and in vitro ADCC assays with human or mouse effector cells demonstrated that IFN‐α markedly increased the amount of cell surface CD317 and augmented the ADCC activity of mAHM and AHM in RCC cells and to a lesser extent in melanoma cells. Administration of IFN‐α to mice bearing RCC xenografts also increased the expression of CD317 in tumor cells. When coadministered with IFN‐α, mAHM exhibited more profound antitumor activity in both IFN‐α‐sensitive and ‐insensitive RCC xenograft models. Thus, AHM in combination with IFN‐α may be an effective therapy for the treatment of RCC. (Cancer Sci 2008; 99: 2461–2466)

Distribution of IL-31 and its receptor expressing cells in skin of atopic dermatitis

BACKGROUND To understand the clinical segments of IL-31 signaling blockade therapy in pruritus of atopic dermatitis (AD), direct detection of the target proteins in the diseased tissues will provide crucial information. There is a lack of direct evidence concerning the cellular origin of IL-31 in AD skins, and data on the expression of IL-31RA in AD are inconsistent. Also, there is no available information regarding IL-31RA protein expression in human dorsal root ganglia (DRG), which mediates the sensation of itch and is the long-suspected source of the protein. OBJECTIVE We sought to obtain direct evidence concerning the distribution of IL-31- and IL-31RA-protein expressing cells and their characteristics in AD skin samples and in human DRG. METHODS IL-31 was detected immunohistochemically in AD skins, and representative sections were double stained with IL-31 and several immune-markers. IL-31RA was stained immunohistochemically in AD skins and normal human DRG, and representative AD skins were double stained with IL-31RA and PGP9.5 (a nerve marker). RESULTS IL-31-positive cells were observed as mononuclear infiltrating cells and as CD11b co-expressing cells in severe AD samples. As for IL-31RA, positive reactions were detected in keratinocytes and nerve fibers in the dermis of AD and in the neurons of normal DRG. CONCLUSION The detection of IL-31 in infiltrating cells of severe AD skin and of IL-31RA in nerve fibers of AD dermis and normal DRG indicates IL-31 signaling may be a contributing factor in the persistence and exacerbation of AD skin lesions.

Anti-IL-31 receptor antibody is shown to be a potential therapeutic option for treating itch and dermatitis in mice

IL‐31, which is described as a pruritogenic cytokine, is linked to the itching that is associated with allergic and non‐allergic eczema, but the precise pruritogenic mechanism of IL‐31 and its potential as a therapeutic target for atopic dermatitis (AD) have not been determined.

Establishment and characterization of in vivo human tumor models in the NOD/SCID/γcnull mouse

Immunodeficient mice are widely used for xenografts of human cells and tissue. The purpose of the present study was to investigate the characteristics of xenograft human tumor models using engraftment of various non‐hematopoietic tumors in the NOD/SCID/γcnull mouse. For tumor models, human solid tumor tissues were serially passaged three or more times to establish tissue lines. A total of 326 fresh tumor specimens, mainly gastrointestinal and female genital tissue, were engrafted with 54 established tissue lines. The types of tissue lines varied and included tumor tissue of both epithelial and mesenchymal origin. In some cases the original surgical specimen was replaced with large mononuclear cells. In the established tumor tissue lines, differentiation and tumor structure were similar to that of the original surgical specimen. The interstitium of the xenograft tissue in the tissue lines was relatively well preserved although slightly decreased and replaced by host tissue. These results indicate that human solid tumors can be successfully engrafted into the NOD/SCID/γcnull mouse and that tissue lines with the characteristics of the original tumors can be established. Investigators in the field of tumor research will benefit from the availability of tissue lines that allow the establishment of more relevant in vivo human tissue models.

Novel genetically-humanized mouse model established to evaluate efficacy of therapeutic agents to human interleukin-6 receptor

For clinical trials of therapeutic monoclonal antibodies (mAbs) to be successful, their efficacy needs to be adequately evaluated in preclinical experiments. However, in many cases it is difficult to evaluate the candidate mAbs using animal disease models because of lower cross-reactivity to the orthologous target molecules. In this study we have established a novel humanized Castlemans disease mouse model, in which the endogenous interleukin-6 receptor gene is successfully replaced by human IL6R, and human IL6 is overexpressed. We have also demonstrated the therapeutic effects of an antibody that neutralizes human IL6R, tocilizumab, on the symptoms in this mouse model. Plasma levels of human soluble IL6R and human IL6 were elevated after 4-week treatment of tocilizumab in this mouse model similarly to the result previously reported in patients treated with tocilizumab. Our mouse model provides us with a novel means of evaluating the in vivo efficacy of human IL6R-specific therapeutic agents.

Spontaneous thymic lymphomas in the non-obese diabetic/Shi-scid, IL-2Rγnull mouse

The NOD/Shi-scid, IL-2Rγ null (NOG) mouse is a severely immunodeficient mouse used for the engraftment of human tissues and cells. In this study, 2406 mice (8–62 weeks old, 503 males and 1903 females) were subcutaneously engrafted with human tissues. In 16 mice (12–26 weeks old, 1 male and 15 females), a mass was seen in the anteroventralis of the thorax on gross examination with an incidence of 0.7%. Histologically, the masses were composed of sheets of lymphoblastic cells. A ‘starry sky’ pattern was observed with numerous mitoses. Immunohistochemically the lymphoblastic cells were positive for Thy 1. The lymphoblastic cells were also seen in the spleen, lung, liver, kidney and heart. The gross and histopathological findings led to the diagnosis of spontaneous thymic lymphoma in NOG mice.

Characterization of EBV-related lymphoproliferative lesions arising in donor lymphocytes of transplanted human tumor tissues in the NOG mouse.

Human tumor tissue line models established in the severely immunodeficient NOD.Cg-Prkdcscid Il2rgtm1Sug/Jic (NOD/Shi-scid, IL-2Rγnull or NOG) mouse are important tools for oncology research. During the establishment process, a lymphoproliferative lesion (LPL) that replaces the original tumor cells in the site of transplantation occurs. In the present study, we studied the impact of the LPL on the establishment process and the characteristics of the lesion, investigated the systemic distribution of the lesion in the mouse, and evaluated the potential of a simple identification method. The incidence of the lesion varied among tumor types, and the lesion was found to be the leading cause of unsuccessful establishment with gastric and colorectal cancer. The lesion consisted of a varying population of proliferating lymphoid cells that expressed CD20. The cells were positive for Epstein-Barr virus (EBV)-related antigens, and EBV DNA was detected. There was systemic distribution of the lesion within the NOG mouse, and the most consistent gross finding was splenomegaly. Additionally, identification of LPL-affected cases was possible by detecting splenomegaly in the 1st and 2nd generation mice at necropsy. From our findings the lesion was judged to arise from EBV-infected B cells originating from the donor, and monitoring splenomegaly at necropsy was thought effective as a simple method for identifying the lesion at an early stage of the establishment process.

An anti–glypican 3/CD3 bispecific T cell–redirecting antibody for treatment of solid tumors

An anti–glypican 3/CD3 bispecific T cell–redirecting antibody (ERY974) is a promising therapeutic agent for solid tumors. Double trouble for solid tumors Because the endogenous immune response is not enough to clear a patient’s cancer, therapies are being designed to redirect T cells to tumor cells. This can be done by engineering the cells ex vivo, such as in CAR T cell therapy, or in vivo, such as with bispecific antibodies. Ishiguro et al. describe the development and preclinical testing of a bispecific antibody recognizing CD3 and glypican 3, a common antigen on solid tumors. This bispecific antibody was effective in a variety of mouse cancer models, even when treatment was initiated after the tumor was quite large. Treatment also appeared to be safe when administered to monkeys. These results suggest further development of this antibody for therapeutic use in multiple cancer types. Cancer care is being revolutionized by immunotherapies such as immune checkpoint inhibitors, engineered T cell transfer, and cell vaccines. The bispecific T cell–redirecting antibody (TRAB) is one such promising immunotherapy, which can redirect T cells to tumor cells by engaging CD3 on a T cell and an antigen on a tumor cell. Because T cells can be redirected to tumor cells regardless of the specificity of T cell receptors, TRAB is considered efficacious for less immunogenic tumors lacking enough neoantigens. Its clinical efficacy has been exemplified by blinatumomab, a bispecific T cell engager targeting CD19 and CD3, which has shown marked clinical responses against hematological malignancies. However, the success of TRAB in solid tumors has been hampered by the lack of a target molecule with sufficient tumor selectivity to avoid “on-target off-tumor” toxicity. Glypican 3 (GPC3) is a highly tumor-specific antigen that is expressed during fetal development but is strictly suppressed in normal adult tissues. We developed ERY974, a whole humanized immunoglobulin G–structured TRAB harboring a common light chain, which bispecifically binds to GPC3 and CD3. Using a mouse model with reconstituted human immune cells, we revealed that ERY974 is highly effective in killing various types of tumors that have GPC3 expression comparable to that in clinical tumors. ERY974 also induced a robust antitumor efficacy even against tumors with nonimmunogenic features, which are difficult to treat by inhibiting immune checkpoints such as PD-1 (programmed cell death protein–1) and CTLA-4 (cytotoxic T lymphocyte–associated protein–4). Immune monitoring revealed that ERY974 converted the poorly inflamed tumor microenvironment to a highly inflamed microenvironment. Toxicology studies in cynomolgus monkeys showed transient cytokine elevation, but this was manageable and reversible. No organ toxicity was evident. These data provide a rationale for clinical testing of ERY974 for the treatment of patients with GPC3-positive solid tumors.

Cynomolgus monkey model of interleukin-31-induced scratching depicts blockade of human interleukin-31 receptor A by a humanized monoclonal antibody

Scratching is an important factor exacerbating skin lesions through the so‐called itch‐scratch cycle in atopic dermatitis (AD). In mice, interleukin (IL)‐31 and its receptor IL‐31 receptor A (IL‐31RA) are known to play a critical role in pruritus and the pathogenesis of AD; however, study of their precise roles in primates is hindered by the low sequence homologies between primates and mice and the lack of direct evidence of itch sensation by IL‐31 in primates. We showed that administration of cynomolgus IL‐31 induces transient scratching behaviour in cynomolgus monkeys and by that were able to establish a monkey model of scratching. We then showed that a single subcutaneous injection of 1 mg/kg nemolizumab, a humanized anti‐human IL‐31RA monoclonal antibody that also neutralizes cynomolgus IL‐31 signalling and shows a good pharmacokinetic profile in cynomolgus monkeys, suppressed the IL‐31‐induced scratching for about 2 months. These results suggest that the IL‐31 axis and IL‐31RA axis play as critical a role in the induction of scratching in primates as in mice and that the blockade of IL‐31 signalling by an anti‐human IL‐31RA antibody is a promising therapeutic approach for treatment of AD. Nemolizumab is currently under investigation in clinical trials.

Segmentation of the Pathophysiological Stages of Diabetic Changes in the db/db Mouse.

The db/db mouse is one of the diabetes mellitus animal models and if the pathophysiological stages of diabetic changes in the mouse model could simulate the stages in human diabetes, the db/db mouse could be used to better evaluate drug candidates. Blood insulin, HbA1c levels and morphological features of pancreatic islets in db/db mice were evaluated to determine the pathophysiological stage. At 6 weeks of age, db/db mice showed the highest level of plasma insulin and lowest level of HbA1c, and histopathological examination revealed enlarged islets with a circular shape and hypertrophic islet cells. By 9 and 12 weeks of age, the plasma insulin levels had decreased to mid levels and HbA1c had increased to mid to high levels; histopathological examination at this time revealed two types of islets coexisting, enlarged circular islets and small irregular-shaped islets. By 15 and 22 weeks of age, plasma insulin had decreased further to low levels and HbA1c was at its highest level; the histopathological examination at this time revealed an increase in irregular-shaped and small islets. Based on blood insulin levels, HbA1c levels and histopathology findings in the db/db mice in this study, the clinical staging of diabetic changes were recognized. The pathophysiological stages of diabetes mellitus in this animal model were similar to the stages in humans.