Molecular subtypes of lung adenocarcinoma present distinct immune tumor microenvironments.

Overcoming resistance to immune checkpoint inhibitors is an important issue in patients with non-small-cell lung cancer (NSCLC). Transcriptome analysis shows that adenocarcinoma can be divided into three molecular subtypes: terminal respiratory unit (TRU), proximal proliferative (PP), and proximal inflammatory (PI), and squamous cell carcinoma (LUSQ) into four. However, the immunological characteristics of these subtypes are not fully understood. In this study, we investigated the immune landscape of NSCLC tissues in molecular subtypes using a multi-omics dataset, including tumor-infiltrating leukocytes (TILs) analyzed using flow cytometry, RNA sequences, whole exome sequences, metabolomic analysis, and clinicopathologic findings. In the PI subtype, the number of TILs increased and the immune response in the tumor microenvironment (TME) was activated, as indicated by high levels of tertiary lymphoid structures, and high cytotoxic marker levels. Patient prognosis was worse in the PP subtype than in other adenocarcinoma subtypes. Glucose transporter 1 (GLUT1) expression levels were upregulated and lactate accumulated in the TME of the PP subtype. This could lead to the formation of an immunosuppressive TME, including the inactivation of antigen-presenting cells. The TRU subtype had low biological malignancy and "cold" tumor-immune phenotypes. Squamous cell carcinoma (LUSQ) did not show distinct immunological characteristics in its respective subtypes. Elucidation of the immune characteristics of molecular subtypes could lead to the development of personalized immune therapy for lung cancer. Immune checkpoint inhibitors could be an effective treatment for the PI subtype. Glycolysis is a potential target for converting an immunosuppressive TME into an antitumorigenic TME in the PP subtype.

Fibroblast inhibition by tocilizumab enabled gemcitabine/nab-paclitaxel rechallenge for pancreatic cancer.

Interleukin-6 (IL-6)/signal transducer and activator of transcription 3 (STAT3) pathway inhibition may overcome chemoresistance of metastatic pancreatic cancer (MPC). We sought to determine the safety and recommended dose of tocilizumab (TCZ), an IL-6 receptor monoclonal antibody, and biological correlates of tumor shrinkage in patients with gemcitabine (GEM)/nanoparticle albumin-bound paclitaxel (nab-PTX)-refractory MPC. This phase 1 study enrolled 10 patients with MPC who had progressed after GEM/nab-PTX. Patients initially received TCZ 8 mg/kg on Day 1 and nab-PTX 100 mg/m2 + GEM 750 mg/m2 on Days 2, 9, and 16. Before and at the end of Cycle 1, biopsy of liver metastases was performed 3-5 h after levofloxacin (LVFX) administration to measure LVFX infiltration into tumor tissue. No dose-limited toxicities occurred, and the recommended dosage of TCZ was determined to be 8 mg/kg. Treatment-emergent adverse events occurred in 80% of patients, of which decreased neutrophil count was the most common. Tumor reduction during Cycle 1 was observed in four patients, who were defined as responders. In paired-biopsy samples, responder-related biological activities were an increase of cleaved PARP expression of tumor nuclei (p = 0.01), a decrease of proliferative cancer-associated fibroblasts (CAFs) (p = 0.08), and an increase of LVFX infiltration in the tumor (p = 0.04). A decrease of phosphorylated STAT3 expression (p = 0.02) favored an increase in LVFX infiltration. In conclusion, TCZ + GEM/nab-PTX-rechallenge had a manageable safety profile and showed preliminary activity via inhibition of CAF and improved intratumoral drug infiltration in MPC.

Development of rat duodenal monolayer model with effective barrier function from rat organoids for ADME assay.

The in-depth analysis of the ADME profiles of drug candidates using in vitro models is essential for drug development since a drug's exposure in humans depends on its ADME properties. In contrast to efforts in developing human in vitro absorption models, only a limited number of studies have explored models using rats, the most frequently used species in in vivo DMPK studies. In this study, we developed a monolayer model with an effective barrier function for ADME assays using rat duodenal organoids as a cell source. At first, we developed rat duodenal organoids according to a previous report, but they were not able to generate a confluent monolayer. Therefore, we modified organoid culture protocols and developed cyst-enriched organoids; these strongly promoted the formation of a confluent monolayer. Furthermore, adding valproic acid to the culture accelerated the differentiation of the monolayer, which possessed an effective barrier function and apicobasal cell polarity. Drug transporter P-gp function as well as CYP3A activity and nuclear receptor function were confirmed in the model. We expect our novel monolayer model to be a useful tool for elucidating drug absorption processes in detail, enabling the development of highly absorbable drugs.

Tumor-infiltrating Leukocyte Profiling Defines Three Immune Subtypes of NSCLC with Distinct Signaling Pathways and Genetic Alterations.

Resistance to immune checkpoint blockade remains challenging in patients with non-small cell lung cancer (NSCLC). Tumor-infiltrating leukocyte (TIL) quantity, composition, and activation status profoundly influence responsiveness to cancer immunotherapy. This study examined the immune landscape in the NSCLC tumor microenvironment by analyzing TIL profiles of 281 fresh resected NSCLC tissues. Unsupervised clustering based on numbers and percentages of 30 TIL types classified adenocarcinoma (LUAD) and squamous cell carcinoma (LUSQ) into the cold, myeloid cell-dominant, and CD8+ T cell-dominant subtypes. These were significantly correlated with patient prognosis; the myeloid cell subtype had worse outcomes than the others. Integrated genomic and transcriptomic analyses, including RNA sequencing, whole-exome sequencing, T-cell receptor repertoire, and metabolomics of tumor tissue, revealed that immune reaction-related signaling pathways were inactivated, while the glycolysis and K-ras signaling pathways activated in LUAD and LUSQ myeloid cell subtypes. Cases with ALK and ROS1 fusion genes were enriched in the LUAD myeloid subtype, and the frequency of TERT copy-number variations was higher in LUSQ myeloid subtype than in the others. These classifications of NSCLC based on TIL status may be useful for developing personalized immune therapies for NSCLC. Significance: The precise TIL profiling classified NSCLC into novel three immune subtypes that correlates with patient outcome, identifying subtype-specific molecular pathways and genomic alterations that should play important roles in constructing subtype-specific immune tumor microenvironments. These classifications of NSCLC based on TIL status are useful for developing personalized immune therapies for NSCLC.

Combination of T cell-redirecting bispecific antibody ERY974 and chemotherapy reciprocally enhances efficacy against non-inflamed tumours.

Identifying a strategy with strong efficacy against non-inflamed tumours is vital in cancer immune therapy. ERY974 is a humanized IgG4 bispecific T cell-redirecting antibody that recognizes glypican-3 and CD3. Here we examine the combination effect of ERY974 and chemotherapy (paclitaxel, cisplatin, and capecitabine) in the treatment of non-inflamed tumours in a xenograft model. ERY974 monotherapy shows a minor antitumour effect on non-inflamed NCI-H446 xenografted tumours, as infiltration of ERY974-redirected T cells is limited to the tumour-stromal boundary. However, combination therapy improves efficacy by promoting T cell infiltration into the tumour centre, and increasing ERY974 distribution in the tumour. ERY974 increases capecitabine-induced cytotoxicity by promoting capecitabine conversion to its active form by inducing thymidine phosphorylase expression in non-inflamed MKN45 tumour through ERY974-induced IFNγ and TNFα in T cells. We show that ERY974 with chemotherapy synergistically and reciprocally increases antitumour efficacy, eradicating non-inflamed tumours.

Generation of a lung squamous cell carcinoma three-dimensional culture model with keratinizing structures.

Tumor nests in lung squamous cell carcinoma (LUSC) have a hierarchical structure resembling squamous epithelium. The nests consist of basal-like cells on the periphery and layers of keratinocyte-like cells that differentiate towards the center of the nest, forming keratin pearls. Reproducing this spatial heterogeneity in in vitro models would be useful for understanding the biology of LUSC. Here, we established a three-dimensional (3D) culture model with a squamous epithelial structure using LUSC cell lines PLR327F-LD41 and MCC001F, established in-house. When PLR327F-LD41 cells were cultured in a mixture of Matrigel and collagen I, they generated 3D colonies (designated cancer organoids, or COs) with involucrin (IVL)-positive keratinizing cells in the center (IVLinner COs). COs with uniform size were generated by seeding PLR327F-LD41 cells in a form of small cell aggregates. Since Notch signaling induces the differentiation of squamous epithelium, we confirmed the effect of γ-secretase inhibitor in inhibiting Notch signaling in IVLinner COs. Surprisingly, γ-secretase inhibitor did not block induction of IVL-positive cells; however, cells residing between the CK5-positive basal-like layer and IVL-positive layer decreased significantly. Thus, our 3D culture model with uniform size and structure promises to be a useful tool for elucidating the biology of LUSC and for screening drug-candidates.

Continuous formation of small clusters with LGR5-positive cells contributes to tumor growth in a colorectal cancer xenograft model.

New cancer characteristics can be discovered by focusing on the process of tumor formation. Cancer stem cells (CSCs) are a key subpopulation, as they are theorized to be at the apex of the tumor hierarchy. We can better understand their function in the tumor hierarchy by using sectioned samples to observe the growth of tumors from their origins as CSCs. In this study, we evaluated the growth of moderate differentiated colorectal cancer from LGR5-positive cells, which is a CSC marker of colorectal cancer, using xenograft and three-dimensional culture models spatiotemporally. These cells express LGR5 at high levels and show CSC phenotypes. To detect them, we used a previously generated antibody that specifically targets LGR5, and were therefore able to observe LGR5-positive cells aggregating into small clusters (sCLs) over the course of tumor growth. Because these LGR5-expressing sCLs formed continuously during growth mainly in the invasive front, we concluded that the structure must contribute significantly to the expansion of CSCs and to tumor growth overall. We confirmed the formation of sCLs from gland structures using a three-dimensional culture model. In addition, sCLs exhibited upregulated genes related to stress response and partial/hybrid epithelial-mesenchymal transition (EMT), as well as genes reported to be prognosis factors. Finally, sCLs with high LGR5 expression were identified in clinical samples. Based on these results, we elucidate how sCLs are an important contributors to tumor growth and the expansion of CSCs.

Exploitation of Elevated Extracellular ATP to Specifically Direct Antibody to Tumor Microenvironment.

The extracellular adenosine triphosphate (ATP) concentration is highly elevated in the tumor microenvironment (TME) and remains tightly regulated in normal tissues. Using phage display technology, we establish a method to identify an antibody that can bind to an antigen only in the presence of ATP. Crystallography analysis reveals that ATP bound in between the antibody-antigen interface serves as a switch for antigen binding. In a transgenic mouse model overexpressing the antigen systemically, the ATP switch antibody binds to the antigen in tumors with minimal binding in normal tissues and plasma and inhibits tumor growth. Thus, we demonstrate that elevated extracellular ATP concentration can be exploited to specifically target the TME, giving therapeutic antibodies the ability to overcome on-target off-tumor toxicity.

Patient-derived xenograft (PDX) models: characteristics and points to consider for the process of establishment.

Tumor research has largely relied on xenograft models created by the engraftment of cultured cell lines derived from tumor tissues into immunodeficient mice for in vivo studies. Like in vitro models, such models retain the ability of tumor cells to continuously proliferate, so they have been used to predict the clinical relevance of studies on proliferating cells. However, these models are composed of a limited population of tumor cells, which include only those tumor cells that are able to adapt to culture conditions, and thus they do not reflect the diversity and heterogeneity of tumors. This, at least in part, explains the poor predictivity of non-clinical data in the research and development of molecularly targeted drugs. Recently, research focus has been directed towards patient-derived xenograft (PDX) models created by directly engrafting tumor tissues, which have not been cultured in vitro, into immunodeficient mice. PDX models reflect the diversity and heterogeneity of tumors, and the evidence they provide can be verified in the patient tissues from which they were derived originally. PDX models are anticipated to efficiently bridge non-clinical and clinical data in translational research. Based on the evidence obtained from our research experience, this review describes the characteristics of PDX models for acting as tumor models, and elucidates the points to consider when attempting to establish these models.

Tissue-specific effects of an anti-desmoglein-3 ADCC antibody due to expression of the target antigen and physiological characteristics of the mouse vagina.

Desmoglein-3 (DSG3) is a potential target of cytotoxic antibody therapy for squamous cell carcinomas but is also expressed in various normal squamous epithelia. We obtained information about DSG3 distribution in mouse tissues by immunohistochemistry and conducted an intravenous multiple-dose study in mouse to estimate the toxic potential of anti-DSG3 therapy. DSG3 was expressed in the squamous epithelium of several organs including the skin, esophagus, tongue, forestomach, eye, and vagina. It was expressed at all estrous cycles of the vagina with changes in distribution patterns along with the structural changes in each cycle, and expression was reduced in ovariectomized (OVX) mice. On the administration of the antibody, there was disarrangement of the vaginal mucosal epithelium with formation of miroabscess, increased granulocyte infiltration, and single cell necrosis. Despite similar expression levels of DSG3 in other tissues, histopathological changes were limited to the vagina. The severity of the changes was reduced by ovariectomy. From these findings, the lesions were thought to be related to the drastic change in the histological structure of the vaginal mucosa accompanying the estrous cycle. Thus, we have shown that the changing expression of target antigen distribution and its relationship with physiological changes in tissue structure are important features for estimating the toxic potential of cytotoxic antibody therapy.

Three-dimensional culture models mimic colon cancer heterogeneity induced by different microenvironments.

Colorectal cancer demonstrates intra-tumour heterogeneity formed by a hierarchical structure comprised of cancer stem cells (CSCs) and their differentiated progenies. The mechanism by which CSCs are maintained and differentiated needs to be further elucidated, and there is evidence that the tumour microenvironment governs cancer stemness. Using PLR123, a colon cancer cell line with CSC properties, we determined the culture conditions necessary to establish a pair of three-dimensional (3D) culture models grown in Matrigel, designated stemCO and diffCO. The conditions were determined by comparing the phenotypes in the models with PLR123 mouse xenografts colonising lung and liver. StemCO resembled LGR5-positive undifferentiated tumours in the lung, and diffCO had lumen structures composed of polarised cells that were similar to the ductal structures found in differentiated tumours in the liver. In a case using the models for biomedical research, treatment with JAG-1 peptide or a γ-secretase inhibitor modified the Notch signaling and induced changes indicating that the signal participates in lumen formation in the models. Our results demonstrate that culture conditions affect the stemness of 3D culture models generated from CSCs and show that comparing models with different phenotypes is useful for studying how the tumour environment regulates cancer.

Histopathological evaluation of crypt fission during intestinal development in neonatal mice.

Pathological evaluation of juvenile toxicity studies requires the understanding of normal tissue development at different ages. Here, we report the morphological features of the neonatal mouse intestine, focusing on crypt fission. Postnatal day (PND) 7 and 14 mice showed fewer crypts and less mature epithelial morphology compared to PND 21 and 28. Crypt fission occurred in three stages: 1) flattening of the crypt base into a skirt shape, 2) penetration of myofibroblasts into the crypt base center, and 3) complete separation of a single crypt into two daughter crypts. The ratio of crypt fission to total number of crypts was the highest at PND 14 and 7 in the jejunum and colon, respectively. Crypt fission, a key phenomenon for balance or imbalance in epithelial cell hierarchy, including stem and differentiated cells, is related to tissue injury repair and tumorigenesis. Therefore, examining crypt fission can provide valuable insights into current conditions of intestine.

In vivo effects of mutant RHOA on tumor formation in an orthotopic inoculation model.

Ras homolog family member A (RHOA) mutations are driver genes in diffuse­type gastric cancers (DGCs), and we previously revealed that RHOA mutations contribute to cancer cell survival and cell migration through their dominant negative effect on Rho­associated kinase (ROCK) signaling in vitro. However, how RHOA mutations contribute to DGC development in vivo is poorly understood. In the present study, the contribution of RHOA mutations to tumor morphology was investigated using an orthotopic xenograft model using the gastric cancer cell line MKN74, in which wild­type (WT) or mutated (Y42C and Y42S) RHOA had been introduced. When we conducted RNA sequencing to distinguish between the genes expressed in human tumor tissues from those in mouse stroma, the expression profiles of the tumors were clearly divided into a Y42C/Y42S group and a mock/WT group. Through gene set enrichment analysis, it was revealed that inflammation­ and hypoxia­related pathways were enriched in the mock/WT tumors; however, cell metabolism­ and cell cycle­related pathways such as Myc, E2F, oxidative phosphorylation and G2M checkpoint were enriched in the Y42C/Y42S tumors. In addition, the gene set related to ROCK signaling inhibition was enriched in the RHOA­mutated group, which indicated that a series of events are related to ROCK inhibition induced by RHOA mutations. Histopathological analysis revealed that small tumor nests were more frequent in RHOA mutants than in the mock or WT group. In addition, increased blood vessel formation and infiltration of macrophages within the tumor mass were observed in the RHOA mutants. Furthermore, unlike mock/WT, the RHOA­mutated tumor cells had little antitumor host reaction in the invasive front, which is similar to the pattern of mucosal invasion in clinical RHOA­mutated DGC. These transcriptome and pathological analyses revealed that mutated RHOA functionally contributes to the acquisition of DGC features, which will accelerate our understanding of the contribution of RHOA mutations in DGC biology and the development of further therapeutic strategies.

Difference in morphology and interactome profiles between orthotopic and subcutaneous gastric cancer xenograft models.

In xenograft models, orthotopic (ORT) engraftment is thought to provide a different tumor microenvironment compared with subcutaneous (SC) engraftment. We attempted to characterize the biological difference between OE19 (adenocarcinoma of the gastroesophageal junction) SC and ORT models by pathological analysis and CASTIN (CAncer-STromal INteractome) analysis, which is a novel method developed to analyze the tumor-stroma interactome framework. In SC models, SCID mice were inoculated subcutaneously with OE19 cells, and tumor tissues were sampled at 3 weeks. In ORT models, SCID mice were inoculated under the serosal membrane of the stomach wall, and tumor tissues were sampled at 3 and 6 weeks after engraftment. Results from the two models were then compared. Histopathologically, the SC tumors were well circumscribed from the adjacent tissue, with scant stroma and the formation of large ductal structures. In contrast, the ORT tumors were less circumscribed, with small ductal structures invading into abundant stroma. Then we compared the transcriptome profiles of human tumor cells with the mouse stromal cells of each model by species-specific RNA sequencing. With CASTIN analysis, we successfully identified several interactions that are known to affect the tumor microenvironment as being selectively enhanced in the ORT model. In conclusion, pathological analysis and CASTIN analysis revealed that ORT models of OE19 cells have a more invasive character and enhanced interaction with stromal cells compared with SC models.

Generation of an anti-desmoglein 3 antibody without pathogenic activity of pemphigus vulgaris for therapeutic application to squamous cell carcinoma.

It is ideal for the target antigen of a cytotoxic therapeutic antibody against cancer to be cancer-specific, but such antigens are rare. Thus an alternative strategy for target selection is necessary. Desmoglein 3 (DSG3) is highly expressed in lung squamous cell carcinoma, while it is well-known that anti-DSG3 antibodies cause pemphigus vulgaris, an autoimmune disease. We evaluated DSG3 as a novel target by selecting an epitope that exerts efficacy against cancer with no pathogenic effects in normal tissues. Pathogenic anti-DSG3 antibodies induce skin blisters by inhibiting the cell-cell interaction in a Ca2+-dependent manner. We screened anti-DSG3 antibodies that bind DGS3 independent of Ca2+ and have high antibody-dependent cell cytotoxicity (ADCC) activity against DSG3-expressing cells. These selected antibodies did not inhibit cell-cell interaction and showed ADCC activity against squamous cell carcinoma cell lines. Furthermore, one of the DSG3 antibodies showed anti-tumour activity in tumour mouse models but did not induce adverse effects such as blister formation in the skin. Thus it was possible to generate an antibody against DSG3 by using an appropriate epitope that retained efficacy with no pathogenicity. This approach of epitope selection may expand the variety of druggable target molecules.

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

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.

Entire CD3ε, δ, and γ humanized mouse to evaluate human CD3-mediated therapeutics.

T cell-mediated immunotherapy is an attractive strategy for treatment in various disease areas. In this therapeutic approach, the CD3 complex is one of the key molecules to modulate T cell functions; however, in many cases, we cannot evaluate the drug candidates in animal experiments because the therapeutics, usually monoclonal antibodies specific to human CD3, cannot react to mouse endogenous Cd3. Although immunodeficient mice transfused with human hematopoietic stem or precursor cells, known as humanized mice, are available for these studies, mice humanized in this manner are not completely immune competent. In this study we have succeeded in establishing a novel mouse strain in which all the three components of the Cd3 complex - Cd3ε, Cd3δ, and Cd3γ - are replaced by their human counterparts, CD3E, CD3D, and CD3G. Basic immunological assessments have confirmed that this strain of human CD3 EDG-replaced mice are entirely immune competent, and we have also demonstrated that a bispecific antibody that simultaneously binds to human CD3 and a tumor-associated antigen (e.g. ERBB2 or GPC3) can be evaluated in human CD3 EDG-replaced mice engrafted with tumors. Our mouse model provides a novel means to evaluate the in vivo efficacy of human CD3-mediated therapy.

The status of donor cancer tissues affects the fate of patient-derived colorectal cancer xenografts in NOG mice.

Patient-derived xenografts (PDXs) of tumors are increasingly becoming important tools for translational research in oncology. The NOD.Cg-Prkdc(scid) Il2rg(tm1Sug)/Jic (NOG) mouse is an efficient host for PDXs. Thus as a basis for future development of methods to obtain PDXs from various disease types, we have studied the factors that affect the outcome of transplantation of human colorectal cancer in NOG mice. Of the original donor cases examined, 73% had successful engraftment. The outcome of donor-matched tissues was consistent in most cases, and was thought to show that the condition of the host did not affect engraftment. Next we analyzed the tumor aggressiveness in terms of histology grade of the original tumor and found that they were related to engraftment. Detailed histopathological examination of the transplanted tissues strongly indicated that lymphocytes engrafted with the tumor cells affect engraftment. As a factor related to transplantation of lymphocytes, we studied the human IgG concentration in the serum of tumor-bearing mice, but there was no tendency for higher concentrations to result in unsuccessful engraftment. Finally, we studied the type, density and location of T cells in the original donor tissue to determine the immune contexture and found that the unsuccessful engraftment cases tended to have an adequate or coordinated immune contexture compared to successful engraftment cases. From these results, we concluded that the aggressiveness and the T cell infiltration of the original tumor affect the outcome of transplantation in the NOG mouse.

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-Prkdc(scid) Il2rg(tm1Sug)/Jic (NOD/Shi-scid, IL-2Rγ(null) 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.

Histopathological characteristics of human non-tumor thyroid tissues in a long-term model of adenomatous goiter xenografts in the NOD/Shi-scid, IL-2Rγ(null) mouse.

There is a growing need for modeling the human thyroid to link data obtained from animals to humans because of its sensitivity to radiation exposure and endocrine disruption chemicals. In a scid mouse model produced by transplanting human thyroid tissues, leakiness and thymic lymphoma that occurs spontaneously in the scid mouse can complicate the interpretation of experimental results. Considering that the NOD.Cg-Prkdc(scid)Il2rg(tm1Sug)/Jic mouse (NOD/Shi-scid, IL-2Rγ(null) or NOG mouse) may be a better host because this strain has low incidence of leakiness and thymic lymphoma, we have evaluated the potential of a model that allows long-term observation of non-tumor human thyroid tissues in this mouse. We transplanted tissues of human adenomatous goiter into NOG mice and examined the tissues histopathologically. The morphology of human adenomatous goiter tissues was maintained from 24 to 44 weeks after transplantation in NOG mice with no noted differences between donor-matched tissues or the weeks after transplantation. The tissues expressed thyroglobulin protein and mRNA as well as thyroperoxidase. Endothelial cells originating from human were found in the transplanted tissues and were thought to be a characteristic of this model. The intactness of the tissues before transplantation was found to affect the rate of tissue engraftment. From the present results we have concluded that transplanted thyroid tissues in NOG mice maintain the histopathological characteristics of their origin for long terms. Therefore this model was thought feasible for toxicity evaluation.