Establishment of a human cutaneous T-cell lymphoma in C.B-17 SCID mice

"Next top" mouse models advancing CTCL research

This review systematically describes the application of in vivo mouse models in studying cutaneous T-cell lymphoma (CTCL), a complex hematological neoplasm. It highlights the diverse research approaches essential for understanding CTCL's intricate pathogenesis and evaluating potential treatments. The review categorizes various mouse models, including xenograft, syngeneic transplantation, and genetically engineered mouse models (GEMMs), emphasizing their contributions to understanding tumor-host interactions, gene functions, and studies on drug efficacy in CTCL. It acknowledges the limitations of these models, particularly in fully replicating human immune responses and early stages of CTCL. The review also highlights novel developments focusing on the potential of skin-targeted GEMMs in studying natural skin lymphoma progression and interactions with the immune system from onset. In conclusion, a balanced understanding of these models' strengths and weaknesses are essential for accelerating the deciphering of CTCL pathogenesis and developing treatment methods. The GEMMs engineered to target specifically skin-homing CD4+ T cells can be the next top mouse models that pave the way for exploring the effects of CTCL-related genes.

Combination of Resminostat with Ruxolitinib Exerts Antitumor Effects in the Chick Embryo Chorioallantoic Membrane Model for Cutaneous T Cell Lymphoma

Simple Summary

The combination of Resminostat (HDACi) and Ruxolitinib (JAKi) exerted cytotoxic effects and inhibited proliferation of CTCL cell lines (MyLa, SeAx) in vitro. The aim of the present study was to validate their antitumor effects in vivo using the chick embryo chorioallantoic membrane (CAM) model, which allows quick and efficient monitoring of tumor growth, migration, invasion, and metastatic potential. The drug combination exhibited a significant inhibition of primary tumor size, and inhibited intravasation and extravasation of tumor cells to the liver and lung. It also exerted an inhibitory effect in the migration and invasion of tumor cells and significantly reduced key signaling pathway activation. Our data demonstrate that the CAM assay could be employed as a preclinical in vivo model in CTCL for pharmacological testing, and that the combination of Resminostat and Ruxolitinib exerts significant antitumor effects in CTCL progression that need to be further evaluated in a clinical setting.

Abstract

The combination of Resminostat (HDACi) and Ruxolitinib (JAKi) exerted cytotoxic effects and inhibited proliferation of CTCL cell lines (MyLa, SeAx) in previously published work. A xenograft tumor formation was produced by implanting the MyLa or SeAx cells on top of the chick embryo chorioallantoic membrane (CAM). The CAM assay protocol was developed to monitor the metastatic properties of CTCL cells and the effects of Resminostat and/or Ruxolitinib in vivo. In the spontaneous CAM assays, Resminostat and Ruxolitinib treatment inhibited the cell proliferation (p < 0.001) of MyLa and SeAx, and induced cell apoptosis (p < 0.005, p < 0.001, respectively). Although monotherapies reduced the size of primary tumors in the metastasis CAM assay, the drug combination exhibited a significant inhibition of primary tumor size (p < 0.0001). Furthermore, the combined treatment inhibited the intravasation of MyLa (p < 0.005) and SeAx cells (p < 0.0001) in the organs, as well as their extravasation to the liver (p < 0.0001) and lung (p < 0.0001). The drug combination also exerted a stronger inhibitory effect in migration (p < 0.0001) rather in invasion (p < 0.005) of both MyLa and SeAx cells. It further reduced p-p38, p-ERK, p-AKT, and p-STAT in MyLa cells, while it decreased p-ERK and p-STAT in SeAx cells in CAM tumors. Our data demonstrated that the CAM assay could be employed as a preclinical in vivo model in CTCL for pharmacological testing. In agreement with previous in vitro data, the combination of Resminostat and Ruxolitinib was shown to exert antitumor effects in CTCL in vivo.

Understanding Cell Lines, Patient-Derived Xenograft and Genetically Engineered Mouse Models Used to Study Cutaneous T-Cell Lymphoma

Cutaneous T cell lymphoma (CTCL) is a spectrum of lymphoproliferative disorders caused by the infiltration of malignant T cells into the skin. The most common variants of CTCL include mycosis fungoides (MF), Sézary syndrome (SS) and CD30⁺ Lymphoproliferative disorders (CD30⁺ LPDs). CD30⁺ LPDs include primary cutaneous anaplastic large cell lymphoma (pcALCL), lymphomatoid papulosis (LyP) and borderline CD30⁺ LPD. The frequency of MF, SS and CD30⁺ LPDs is ~40–50%, <5% and ~10–25%, respectively. Despite recent advances, CTCL remains challenging to diagnose. The mechanism of CTCL carcinogenesis still remains to be fully elucidated. Hence, experiments in patient-derived cell lines and xenografts/genetically engineered mouse models (GEMMs) are critical to advance our understanding of disease pathogenesis. To enable this, understanding the intricacies and limitations of each individual model system is highly important. Presently, 11 immortalized patient-derived cell lines and different xenograft/GEMMs are being used to study the pathogenesis of CTCL and evaluate the therapeutic efficacy of various treatment modalities prior to clinical trials. Gene expression studies, and the karyotyping analyses of cell lines demonstrated that the molecular profile of SeAx, Sez4, SZ4, H9 and Hut78 is consistent with SS origin; MyLa and HH resemble the molecular profile of advanced MF, while Mac2A and PB2B represent CD30⁺ LPDs. Molecular analysis of the other two frequently used Human T-Cell Lymphotropic Virus-1 (HTLV-1)⁺ cell lines, MJ and Hut102, were found to have characteristics of Adult T-cell Leukemia/Lymphoma (ATLL). Studies in mouse models demonstrated that xenograft tumors could be grown using MyLa, HH, H9, Hut78, PB2B and SZ4 cells in NSG (NOD Scid gamma mouse) mice, while several additional experimental GEMMs were established to study the pathogenesis, effect of drugs and inflammatory cytokines in CTCL. The current review summarizes cell lines and xenograft/GEMMs used to study and understand the etiology and heterogeneity of CTCL.

Challenging Cutaneous T-Cell Lymphoma: What Animal Models Tell us So Far

Cutaneous T-cell lymphomas are characterized by heterogeneity of clinical variants, further complicated by genomic and microenvironmental variables. Furthermore, in vitro experiments are hampered by the low culture efficiency of these malignant cells. Animal models are essential for understanding the pathogenetic mechanisms underlying malignancy and for discovering new anticancer treatments. They are divided into two main categories: those in which tumors arise in the host owing to genetic modifications and those that use tumor cell transplantation. In this review, we summarize the attempts to decipher the complexity of the pathogenesis of cutaneous T-cell lymphoma by exploiting genetically modified and xenograft models.

Mouse Models for Human Skin Transplantation: A Systematic Review

Immunodeficient mouse models with human skin xenografts have been developed in the past decades to study different conditions of the skin. Features such as follow-up period and size of the graft are of different relevance depending on the purpose of an investigation. The aim of this study is to analyze the different mouse models grafted with human skin. A systematic review of the literature was performed in line with the PRISMA statement using MEDLINE/PubMed databases from January 1970 to June 2020. Articles describing human skin grafted onto mice were included. Animal models other than mice, skin substitutes, bioengineered skin, postmortem or fetal skin, and duplicated studies were excluded. The mouse strain, origin of human skin, graft dimensions, follow-up of the skin graft, and goals of the study were analyzed. Ninety-one models were included in the final review. Five different applications were found: physiology of the skin (25 models, mean human skin graft size 1.43 cm2 and follow-up 72.92 days), immunology and graft rejection (17 models, mean human skin graft size 1.34 cm2 and follow-up 86 days), carcinogenesis (9 models, mean human skin graft size 1.98 cm2 and follow-up 253 days), skin diseases (25 models, mean human skin graft size 1.55 cm2 and follow-up 86.48 days), and would healing/scars (15 models, mean human skin graft size 2.54 cm2 and follow-up 129 days). The follow-up period was longer in carcinogenesis models (253 ± 233.73 days), and the skin graft size was bigger in wound healing applications (2.54 ± 3.08 cm2). Depending on the research application, different models are suggested. Careful consideration regarding graft size, follow-up, immunosuppression, and costs should be analyzed and compared before choosing any of these mouse models. To our knowledge, this is the first systematic review of mouse models with human skin transplantation.

A Microbiota-Dependent, STAT3-Driven Mouse Model of Cutaneous T-Cell Lymphoma

In recent years, much has been learned about the molecular genetics of cutaneous T-cell lymphomas. Fanok et al. (2018) translate knowledge from systematic genomic and transcriptomic analyses to develop a mouse model that tests the hypothesis that activated STAT3 in CD4⁺ T cells may be a driver of cutaneous T-cell lymphomas. The transgenic mouse that they developed exhibits clinical features of mycosis fungoides, as well as Sezary syndrome, two well-known entities in the cutaneous T-cell lymphoma spectrum. Furthermore, these authors show that TCR engagement and microbiota are required for development of the complete clinical phenotype. This mouse model, which develops progressive disease, provides a new tool to understand cutaneous T-cell lymphoma biology and to potentially test new therapies.

Role of Dysregulated Cytokine Signaling and Bacterial Triggers in the Pathogenesis of Cutaneous T-Cell Lymphoma

Cutaneous T-cell lymphoma is a heterogeneous group of lymphomas characterized by the accumulation of malignant T cells in the skin. The molecular and cellular etiology of this malignancy remains enigmatic, and what role antigenic stimulation plays in the initiation and/or progression of the disease remains to be elucidated. Deep sequencing of the tumor genome showed a highly heterogeneous landscape of genetic perturbations, and transcriptome analysis of transformed T cells further highlighted the heterogeneity of this disease. Nonetheless, using data harvested from high-throughput transcriptional profiling allowed us to develop a reliable signature of this malignancy. Focusing on a key cytokine signaling pathway previously implicated in cutaneous T-cell lymphoma pathogenesis, JAK/STAT signaling, we used conditional gene targeting to develop a fully penetrant small animal model of this disease that recapitulates many key features of mycosis fungoides, a common variant of cutaneous T-cell lymphoma. Using this mouse model, we show that T-cell receptor engagement is critical for malignant transformation of the T lymphocytes and that progression of the disease is dependent on microbiota.

Human cancer growth and therapy in immunodeficient mouse models

Since the discovery of the "nude" mouse more than 40 years ago, investigators have attempted to model human tumor growth in immunodeficient mice. Here, we summarize how the field has advanced over the ensuing years owing to improvements in the murine recipients of human tumors. These improvements include the discovery of the scid mutation and development of targeted mutations in the recombination-activating genes 1 and 2 (Rag1(null), Rag2(null)) that severely cripple the adaptive immune response of the murine host. More recently, mice deficient in adaptive immunity have been crossed with mice bearing targeted mutations designed to weaken the innate immune system, ultimately leading to the development of immunodeficient mice bearing a targeted mutation in the gene encoding the interleukin 2 (IL2) receptor common γ chain (IL2rg(null), also known in humans as cytokine receptor common subunit γ). The IL2rg(null) mutation has been used to develop several immunodeficient strains of mice, including the NOD-scid IL2rg(null) (NSG) strain. Using NSG mice as human xenograft recipients, it is now possible to grow almost all types of primary human tumors in vivo, including most solid tumors and hematological malignancies that maintain characteristics of the primary tumor in the patient. Programs to optimize patient-specific therapy using patient-derived xenograft tumor growth in NSG mice have been established at several institutions, including The Jackson Laboratory. Moreover, NSG mice can be engrafted with functional human immune systems, permitting for the first time the potential to study primary human tumors in vivo in the presence of a human immune system.

Models for mature T-cell lymphomas--a critical appraisal of experimental systems and their contribution to current T-cell tumorigenic concepts

Mature T-cell lymphomas/leukemias (MTCL) have been understudied lymphoid neoplasms that currently receive growing attention. Our historically rudimentary molecular understanding and dissatisfactory interventional success in this complex and for the most part poor-prognostic group of tumors is only slightly improving. A major limiting aspect in further progress in these rare neoplasms is the lack of suitable model systems that would substantially facilitate pathogenic studies and pre-clinical drug evaluations. Such representations of MTCL have thus far not been systematically appraised. We therefore provide an overview on existing models and point out their particular advantages and limitations in the context of the specific scientific questions. After addressing issues of species-specific differences and classifications, we summarize data on MTCL cell lines of human as well as murine origin, on murine strain predispositions to MTCL, on available models of genetically engineered mice, and on transplant systems. From an in-silico meta-analysis of available primary data of gene expression profiles on human MTCL we cross-reference genes reported to transform T-cells in mice and reflect on their general vs entity-restricted relevance and on target-promoter influences. Overall, we identify the urgent need for new models of higher fidelity to human MTCL with respect to their increasingly recognized diversity and to predictions of drug response.

A novel xenograft model of cutaneous T-cell lymphoma

Cutaneous T-cell lymphomas (CTCLs) are characterized by accumulation of malignant T cells in the skin. Early disease resembles benign skin disorders but during disease progression cutaneous tumors develop, and eventually the malignant T cells can spread to lymph nodes and internal organs. However, because of the lack of suitable animal models, little is known about the mechanisms driving CTCL development and progression in vivo. Here, we describe a novel xenograft model of tumor stage CTCL, where malignant T cells (MyLa2059) are transplanted to NOD/SCID-B2m(-/-) (NOD.Cg-Prkdc(scid) B2m(tm1Unc) /J) mice. Subcutaneous transplantation of the malignant T cells led to rapid tumor formation in 43 of 48 transplantations, whereas transplantation of non-malignant T cells isolated from the same donor did not result in tumor development. Importantly, the tumor growth was significantly suppressed in mice treated with vorinostat when compared to mice treated with vehicle. Furthermore, in most mice the tumors displayed subcutaneous and/or lymphatic dissemination. Histological, immunohistochemical and flow cytometric analyses confirmed that both tumors at the inoculation site, as well as distant subcutaneous and lymphatic tumors, originated from the transplanted malignant T cells. In conclusion, we describe a novel mouse model of tumor stage CTCL for future studies of disease dissemination and preclinical evaluations of new therapeutic strategies.

A mouse model for the Sézary syndrome

BACKGROUND

The Sézary syndrome is an aggressive leukemic form of cutaneous T cell lymphoma and there is no cure of this disease. Until now there is no true animal model for Sézary syndrome, by which new drugs against the disease could be tested.

METHODS

Immune deficient CB-17 SCID beige mice were injected subcutaneously with HUT78 cells, a cell line, derived from a Sézary syndrome patient. Developing tumors were analyzed by immunohistochemistry.

RESULTS

Injected HUT78 cells formed tumors at the site of injection. In contrast to the Sézary syndrome in man, no malignant cells were observed in the blood of tumor bearing CB-17 SCID beige mice. The tumors appeared 44-62 days after injection and tumor bearing mice survived further 25 - 62 days until they had to be euthanized according to the guidelines of the Swiss animal protection law, since the tumors had reached the maximal allowed size.

CONCLUSION

Although the mouse model does not exactly match the human disease, it will be suited for tests of new substances for the treatment of the Sézary syndrome. The formation of an isolated tumor on the skin has the advantage that the effect of a potential drug can be directly monitored without the use of invasive methods.

Establishment of a mouse xenograft model for mycosis fungoides

Mycosis fungoides (MF) is the most frequent variant of cutaneous T-cell lymphomas (CTCLs). MF primarily involves the skin initially with patches and plaques. In later stages, cutaneous tumors develop and tumor cells may spread to lymph nodes and finally to visceral sites. Here, we describe an animal model for MF in immune-deficient nude mice, using the CTCL cell line MyLa. Subcutaneous transplantation of MyLa cells leads to the formation of cutaneous tumors in 80% of the mice (50/60 total). Spread of tumor cells to visceral sites was detected by immunohistochemistry and polymerase chain reaction (PCR)-based detection of specific T-cell receptor-gamma rearrangement. MyLa cells were found circulating in the blood, lymph nodes, and in blood vessels of heart, kidney, lung, and liver. In lung and liver tissue, tumor cells presented perivascular invasion, but no large secondary tumors developed. The nude mouse model described here will be a valuable test system for new therapeutic approaches for the treatment of MF and opens the unique opportunity to study the disease in vivo.

Human-SCID mouse chimeric models for the evaluation of anti-cancer therapies

The ability to engraft human tumors and human immunocompetent cells successfully in severe combined immunodeficient (SCID) mice has spawned the development and use of human-mouse chimeric models to evaluate anti-cancer therapies. The lack of standardization and many other potential pitfalls have contributed to the current controversy surrounding the reliability of these different models. Five frequently used SCID mouse models and their specific applications are summarized with the specific aim of providing an objective discussion of the strengths and limitations of each model, together with suggestions for overcoming some of the variabilities and for improving the design and use of future models.

Chemokine-induced cutaneous inflammatory cell infiltration in a model of Hu-PBMC-SCID mice grafted with human skin

Recently, certain chemokines and chemokine receptors have been preferentially associated with the selective recruitment in vitro of type 1 T cells, such as IP-10 and its receptor CXCR3, or type 2 T cells such as monocyte-derived chemokine (MDC) and eotaxin and their receptors CCR4 and CCR3. Very few models have provided confirmation of these findings in vivo. Taking advantage of the humanized SCID mouse model grafted with autologous human skin, the ability of the chemokines IP-10, MDC, eotaxin, and RANTES to stimulate cell recruitment was investigated. Intradermal IP-10 injection resulted in an influx of CD4+ T lymphocytes but also surprisingly in the recruitment of dendritic cells. MDC recruited mainly CD8+ T lymphocytes, and had little effect on eosinophils. As predicted, eotaxin was a potent inducer of eosinophil and basophil migration, also recruiting CD4+ T cells. RANTES, a ubiquitous chemokine associated with both type 1 and type 2 profiles, was able to recruit all cell types. CXCR3-positive cells were preferentially recruited by IP-10, whereas CCR3- and CCR4-positive cells were predominantly found after injection of eotaxin and MDC. Thus, in a human environment in vivo, some chemokines have the ability to recruit cells expressing chemokine receptors preferentially expressed on type 1 or type 2 cells. Further investigations revealed that MDC and eotaxin induced the recruitment of type 2, but not type 1, cytokine-producing cells. RANTES, on the other hand, induced the migration of both type 1 and type 2 cytokine-secreting cells, whereas IP-10 did not induce the recruitment of either subtype. These studies provide detailed information on the properties of MDC, eotaxin, IP-10, and RANTES as chemotactic molecules in skin in vivo. The use of the humanized SCID mouse model grafted with human skin is validated as a useful model for the evaluation of chemokine function in the inflammatory reaction, and suggests that therapeutic targeting of certain chemokines might be of interest in diseases associated preferentially with a type 1 or type 2 profile.

A murine xenograft model for human CD30+ anaplastic large cell lymphoma. Successful growth inhibition with an anti-CD30 antibody (HeFi-1)

To develop a model for the biology and treatment of CD30+ anaplastic large cell lymphoma (ALCL), we transplanted leukemic tumor cells from a 22-month-old girl with multiple relapsed ALCL. Tumor cells were inoculated intraperitoneally into a 4-week-old SCID/bg mouse and produced a disseminated tumor within 8 weeks; this tumor was serially transplanted by subcutaneous injections to other mice. Morphology, immunohistochemistry, and molecular genetics which demonstrated the NPM-ALK fusion protein, resulting from the t(2;5)(p23;q35), confirmed the identity of the xenograft with the original tumor. The tumor produced transcripts for interleukin-1alpha, tumor necrosis factor-alpha, and interferon-gamma which could explain the patient's B-symptoms. Treatment of mice with monoclonal antibody (HeFi-1) which activates CD30 antigen administered on day 1 after tumor transplantation prevented tumor growth. Treatment with HeFi-1 after tumors had reached a 0.2 cm(3) volume caused tumor growth arrest and prevention of tumor dissemination. We conclude that transplantation of CD30+ ALCL to SCID/bg mice may provide a valuable model for the study of the biology and design of treatment modalities for CD30+ ALCL.

Transformed and nontransformed human T lymphocytes migrate to skin in a chimeric human skin/SCID mouse model

To study human T cell migration to human skin in vivo, we grafted severe combined immunodeficient mice with 500-microm thick human skin. Two weeks after grafting, epidermal and dermal structures in the grafts were of human origin. When we intraperitoneally injected grafted mice with clones of the human HUT-78 T cell line derived from a patient with cutaneous T cell lymphoma and Sézary syndrome, we detected in the grafts the rare Vbeta23-Jbeta1.2 T cell receptor transcripts characteristic for the HUT-78 clones. These signals were found 2-6 d after cell injection in about 40% of the grafted and HUT-78 cell injected mice but not in grafts from mice that received no exogenous T cells. In contrast to HUT-78 cells, which only accumulate in low number, grafts topically challenged with nickel sufate in vaseline from mice that were injected with autologous nickel-reactive T cell lines led to massive accumulation of T cells within 3 d. Only scattered T cells accumulated in the skin when grafted mice received vaseline plus T cells, nickel sulfate alone, T cells alone, or nickel sulfate plus an allogeneic nickel-nonreactive T cell clone. When the T cell lines were labeled with the fluorochrome PKH-26 before cell injection, spots of fluorescent label in the size and shape of cells were found in the grafts challenged with nickel. Together, these results clearly demonstrate that human T cells can migrate to human skin in this chimeric human/mouse model.

Xenogeneic (bovine) peripheral blood leukocytes engrafted into severe combined immunodeficient mice retain primary immune function

The immune responsiveness of xenogeneic PBL engrafted into SCID mice was investigated using the bovine PBL-reconstituted SCID mouse model system (PBL-SCID-bo). Bovine PBL-reconstitution and B-cell activity were monitored by bovine serum Ig production. Bovine T-cell function was demonstrated by an antigen-specific immune response to bovine transplantation antigens provided by bovine skin allografts. Bovine allograft rejection was clearly evident in > 65% PBL-SCID-bo that received a bovine PBL inoculum either 30 days after bovine skin grafting, or 7-52 days before bovine skin grafting. Bovine allograft rejection was confirmed via histological examination and was characterized primarily by a band of infiltrating bovine lymphocytes at the periphery of the graft and tissue necrosis. A secondary immune response could be elicited if bovine cells in the PBL inoculum were presensitized to Ag from the bovine skin allograft donor. This study is the first to show that bovine cells engrafted in SCID mice after i.p. injection of bovine PBL retain some aspects of immune competency. These results confirm the value of the xenogeneic PBL-reconstituted SCID mouse model in the study of primary immunity.

Engraftment of precursor lesions of human cutaneous neoplasms onto C.B-17 SCID mice: a useful in vivo experimental model of carcinogenesis in human skin

Using a full-thickness skin grafting technique, lesional skin from various human neoplastic and preneoplastic skin diseases was transplanted onto SCID (severe combined immunodeficiency) mice. Of 27 grafted lesions, 21 were successfully accepted by the mice and maintained in good condition. All these accepted grafts were finally excised 10-101 days after transplantation for histological examination. In most grafts, the characteristic histological configurations of each disease were well preserved. Immunohistochemical study using monoclonal antibodies to human blood group antigens ABH revealed that some elements of the grafts such as sweat glands were clearly positive, confirming that the tissue was from human skin. Neoplastic (atypical) cells were detected in 9 of 17 accepted grafts containing neoplastic cells from the beginning. The detection rates for neoplastic cells were very high (90%) in grafts from precursor lesions of squamous cell carcinomas such as Bowen's disease (5/5 specimens) and thermal keratosis (2/3). In contrast, no definite neoplastic cells were found in two grafts from extramammary Paget's disease and five grafts from the radial growth component of malignant melanoma. In most of the grafts from latter two diseases, characteristic histological configurations such as elongation of the rete ridges were maintained, suggesting that the neoplastic cells were selectively eliminated from the grafts. Split-thickness grafts of normal human skin were accepted and remained in a good condition for as long as 6 months. Engraftment of human lesional and non-lesional skin onto SCID mice therefore may well provide a useful in vivo experimental model of human skin diseases.

The C.B.17 scid mouse strain as a model for human disseminated leukaemia and myeloma in vivo

Using the C.B.17 scid mouse strain, we have developed a model of disseminated leukaemia and myeloma using five human cell lines, CCRF-Cem, Molt-4, Raji, IM9 and HS-Sultan. Introduction of any of these cell lines by either an intravenous or an intraperitoneal route eventually kills the mouse due to leukaemia or myeloma cell load. Neoplastic cells can be found in the blood, liver and bone marrow. Intraperitoneal transfer produces a local solid tumour whereas intravenous transfer produces foci of neoplastic cells in the spine and brain. A single dose of melphalan is able to increase survival time from infection of a lethal dose of the T-cell leukaemia cell line, CCRF-Cem.

High level functional engraftment of severe combined immunodeficient mice with human peripheral blood lymphocytes following pretreatment with radiation and anti-asialo GM1

The severe combined immunodeficient (SCID) mouse engrafted with human peripheral blood lymphocytes (PBLs) is a potentially useful model for the study of cancer immunotherapy. For this application, rapid, consistent, and high level engraftment of SCID mice with functional human cytotoxic effector cells is necessary. To date, short term human lymphoid cell engraftment in SCID mice has generally been low and variable. Further, most of the human cells detected within the first 30 days are found in the peritoneal cavity. The purpose of the present study was to improve short term reconstitution of human PBLs in the SCID mouse. When untreated SCID mice were injected with human PBLs, the mean level of CD3+ cells in the spleens was < 5% on days 6-32 after injection, as determined by flow cytometry (FCM). Depletion of SCID mouse natural killer (NK) cells with anti-asialo GM1 only marginally improved short term reconstitution with human CD3+ cells. Preirradiation of SCID mice with 3 Gy improved reconstitution to over 16% CD3+ cells on days 12-14 following engraftment. However, the combination of pretreatment with anti-asialo GM1 plus radiation, significantly increased the mean percentage of human CD3+ cells in the spleen to 40% within 2 weeks following injection of PBLs. Human T cells positive for CD4, CD8, TcR alpha beta, and TcR gamma delta, and human NK and B cells were detected in the spleens of irradiated plus anti-asialo GM1 pretreated SCID mice. The presence of human lymphoid cells was confirmed by immunohistologic staining. The human immune cells in these mice were shown to be functional by the in vivo demonstration of an appropriate secondary immune response to the injection of tetanus toxoid and by an in vivo proliferative response to phytohemagglutinin. Human NK cells could be found in the spleens and peripheral blood of irradiated plus anti-asialo GM1 pretreated mice. These cells were also shown to be competent by their ability to lyse the human NK sensitive tumor targets K562 and MOLT-4 in 51Cr release assays. Thus, pretreatment of SCID mice with radiation plus anti-asialo GM1 significantly improves short term human PBL engraftment and provides a potentially useful model for the study of cancer immunotherapy.

Effectiveness of HB2 (anti-CD7)--saporin immunotoxin in an in vivo model of human T-cell leukaemia developed in severe combined immunodeficient mice

The transplantation of the human T-cell acute lymphoblastic leukaemia (T-ALL) cell line HSB-2 into severe combined immunodeficient (SCID) mice was found to produce a disseminated pattern of leukaemia similar to that seen in man. The intravenous injection of 10(7) HSB-2 cells was associated with a universally fatal leukaemia. Histopathological examination of animals revealed the spread of leukaemia initially from bone marrow to involve all major organs including the meninges. An immunotoxin (HB2-Sap) was constructed by conjugating the anti-CD7 MAb HB2 to the ribosome-inactivating protein saporin. An in vitro protein synthesis inhibition assay revealed specific delivery of HB2-Sap immunotoxin (IT) to CD7+ HSB-2 target cells with an IC50 of 4.5 pM. When SCID mice were injected with 10(6) HSB-2 cells and then treated 8 days later with a single intravenous dose of 10 micrograms of immunotoxin there was a significant therapeutic effect evidenced by the numbers of animals surviving in the therapy group compared with untreated controls (chi 2 = 5.348, P = 0.021). These results demonstrate the useful application of human leukaemia xenografts in SCID mice and the potential therapeutic effect of an anti-CD7 immunotoxin in human T-ALL.

Immunotoxin studies in a model of human T-cell acute lymphoblastic leukemia developed in severe combined immune-deficient mice

The transplantation of the human T-cell acute lymphoblastic leukemia (T-ALL) cell line HSB-2 into severe combined immune-deficient (SCID) mice was found to produce a disseminated pattern of leukemia similar to that seen in humans. The iv injection of 10(7) HSB-2 cells was associated with a universally fatal leukemia. Histopathological examination of animals revealed the spread of leukemia initially from bone marrow to involve all major organs including the meninges. An immunotoxin (HB2-Sap) was constructed by conjugating the anti-CD7 monoclonal antibody (MAb) HB2 to the ribosome inactivating protein (RIP) saporin. An in vitro protein synthesis inhibition assay revealed specific delivery of HB2-Sap immunotoxin (IT) to CD7+ HSB-2 target cells with an IC50 of 4.5 pM. In an in vivo study, the IT was shown to significantly prolong the survival of SCID mice injected with HSB-2 cells compared to untreated control animals. This therapeutic effect was seen both with a single injection of 10 micrograms of IT given 7 d after the injection of HSB-2 cells, and was even more effective when IT was administered as three daily injections of 10 micrograms on d 7, 8, and 9. These results demonstrate the useful application of human leukemia xenografts in SCID mice and the potential therapeutic effect of an anti-CD7 IT in human T-ALL.

In vivo targeting of integrin receptors in human skin xenografts by intravenously applied antibodies

We examined whether systemically injected monoclonal antibodies (mAbs) directed to cell-surface glycoproteins of human keratinocytes reach their target antigens in xenograft transplants of normal human skin on SCID mice. The integrins alpha 6 beta 4, expressed in the basal cell layer of human epidermis, and glycoprotein T16 (gp 40/50), expressed in terminally differentiating keratinocytes of the stratum spinosum, were selected as targets. It was found that all injected mAbs selectively localized to their antigens and bound and saturated their targets even in the uppermost layers of the stratum malpighii. This could easily be monitored by direct immunofluorescence staining since SCID mice lack endogenous production of significant amounts of immunoglobulins. After a single injection, mAbs could still be detected at the target site after 14 days. Our results proved that heterologous immunoglobulins pass systemic capillary filters in this xenograft model and specifically bind to their target molecules. Thus, xenografted SCID mice provide a versatile model for studying cell-surface glycoprotein-mediated interactions by the use of functionally interfering antibodies under in vivo conditions in human skin.

Cellular and molecular composition of human skin in long-term xenografts on SCID mice

We report on the immunophenotypical characterization of adult human skin transplanted onto severe combined immunodeficient (SCID) mice. Thirty animals were followed for up to 12 months after receiving split-thickness xenografts, of which 28 were tolerated for the whole test period. Antigen mapping revealed an almost complete preservation of human cellular and extracellular tissue components in long-term transplants including skin immune cells (Langerhans-cells, macrophages, lymphocytes) and also parts of the engrafted endothelium. Hence, xenografts on SCID mice offer a versatile experimental tool for the in vivo study of both human skin immune cell function and endothelial cell-mediated interactions in an environment completely devoid of interferences by adoptive host immune response.

Growth of Hodgkin cell lines in severely combined immunodeficient mice

No animal model exists for the in vivo growth of Hodgkin's-lymphoma-derived cells. Neither unmanipulated Hodgkin's-disease(HD)-derived cell lines nor primary biopsy tissue could be grown in nude mice. Since the severe combined immunodeficient (SCID) mouse has been reported to be a better recipient for transplanted human lymphatic tissue than the nude mouse, we tested whether SCID mice provide suitable conditions for the in vivo growth of HD cell lines. Tumorigenicity of HD cells was tested in untreated and pre-treated SCID mice and in another combined immunodeficient mouse strain, beige/nude/X-linked immunodeficient (BNX) mouse. SCID mice supported in vivo growth of the 6 HD cell lines tested (L428, L540, L591, DEV, HD-LM2, KM-H2). Only one of the 6 lines (DEV) was tumorigenic in BNX mice. No HD cell line proliferated in T-cell-deficient nude mice. Thus, in vivo growth of HD cell lines appeared to be related to the degree of host immunodeficiency. Additional growth supportive treatments such as fibrosarcoma co-transplantation, intraperitoneal mineral oil injection or immunosuppressive pre-treatment (anti-asialo-GMI-antibody injection) permitted growth of 3 additional HD cell lines in BNX mice. The immunophenotype and karyotype of explanted graft cells were identical to the original cell lines. Our experiments describe an effective and reproducible xenograft model for growth of Hodgkin's-disease-derived cell lines. This may be of value for elucidating the growth characteristics of Hodgkin's-lymphoma-derived cells as well as for testing new therapeutic regimens.

Preliminary report: growth of Hodgkin's lymphoma derived cells in immune compromised mice

Until now there has been no satisfactory animal host for the in vivo growth of Hodgkin lymphoma cells. With the exception of one mutant subline (L540Cy) none of the other Hodgkin derived cell lines nor Hodgkin's disease (HD) derived lymphatic tissue could be propagated in suitable animal systems such as the T-cell deficient nude mouse. Recently, the severe combined immunodeficient (SCID-) mouse has been demonstrated as a possible recipient for human lymphatic tissue. In the present study, we have evaluated the SCID mouse as a possible in vivo model for Hodgkin's lymphoma. I) We demonstrate that seven permanent cell lines derived from patients with Hodgkin's disease grow progressively in SCID mice after subcutaneous and intraperitoneal inoculation. II) In addition, after intravenous injection, two of these lines (L540, L540Cy) show a disseminated growth pattern resembling the distribution of HD cells in man (involvement of lymph nodes, liver and bone marrow but not of spleen). The observed reproducible disseminated tumor growth establishes the SCID mouse as a new animal model for experimental treatment strategies in Hodgkin's lymphoma. III) We present preliminary results of the transplantation of primary material from 13 patients with Hodgkin's disease. Material from two patients induced human tumors in the SCID mice recipients, whereas material from two others led to the induction of mouse lymphomas. The human tumors showed three distinct histological patterns: 1) Lymphoproliferative disease (LPD); 2) anaplastic large cell lymphomas (ALCL); 3) Hodgkin like lesions (HLL). In vitro cell lines established from human SCID mouse tumors were of B-lymphoid origin, were EBV-positive and showed numerical and some structural chromosomal aberrations of varying degree.

Growth of MCF-7 human breast carcinoma in severe combined immunodeficient mice: growth suppression by recombinant interleukin-2 treatment and role of lymphokine-activated killer cells

The severe combined immunodeficient (SCID) mouse, lacking functional T and B lymphocytes, has been considered by many groups to be a prime candidate for the reconstitution of a human immune system in a laboratory animal. In addition, this immuno-deficient animal would appear to have excellent potential as a host for transplanted human cancers, thus providing an exceptional opportunity for the study of interactions between the human immune system and human cancer in a laboratory animal. However, because this animal model is very recent, few studies have been reported documenting the capability of these mice to accept human cancers, and whether or not the residual immune cells in these mice (e.g. natural killer, NK, cells; macrophages) possess antitumor activities toward human cancers. Thus, the purpose of this study was (a) to determine whether or not a human breast carcinoma cell line (MCF-7) can be successfully transplanted to SCID mice, (b) to determine whether or not chronic treatment of SCID mice with a potent lymphokine (recombinant interleukin-2, rIL-2) could alter MCF-7 carcinoma growth, and (c) to assess whether or not rIL-2-activated NK cells (LAK cells) are important modulators of growth of MCF-7 cells in SCID mice. To fulfill these objectives, female SCID mice were implanted s.c. with MCF-7 cells (5 x 10(6) cells/mouse) at 6 weeks of age. Six weeks later, some of the mice were injected i.p. twice weekly with rIL-2 (1 x 10(4) U mouse-1 injection-1). Results clearly show that MCF-7 cells can grow progressively in SCID mice; 100% of the SCID mice implanted with MCF-7 cells developed palpable measurable tumors within 5-6 weeks after tumor cell inoculation. In addition, MCF-7 tumor growth was significantly (P less than 0.01) suppressed by rIL-2 treatment. rIL-2 treatment was non-toxic and no effect of treatment on body weight gains was observed. For non-tumor-bearing SCID mice, splenocytes treated in vitro with rIL-2 (lymphokine-activated killer, LAK, cells) or splenocytes derived from rIL-2-treated SCID mice (LAK cells) had significant (P less than 0.01) cytolytic activity toward MCF-7 carcinoma cells in vitro. In contrast, splenocytes (LAK cells) derived from tumor(MCF-7)-bearing rIL-2-treated SCID mice lacked cytolytic activities toward MCF-7 cells in vitro. No significant concentration of LAK cells in MCF-7 human breast carcinomas ws observed nor did rIL-2 treatment significantly alter growth of MCF-7 cells in vitro.(ABSTRACT TRUNCATED AT 400 WORDS)

Potential of the scid mouse as a host for human tumors

Animal models of human tumors and their metastases that effectively mimic clinical disease are in considerable demand. While it is certainly true that athymic nude mice provide us with useful models to study a large number of human tumors in vivo, it is also well known that nude mice usually do not develop spontaneous metastases and are not suitable for all types of tumors. Therefore, the scid mouse that allows disseminated growths for a number of human tumors, particularly hematologic disorders and malignant melanoma, can be used preferentially for the investigation of such malignancies. The potential to study the interaction of human immune cells and human tumor in an in vivo model is another unique feature of scid mice that will add to their usefulness in experimental cancer research.

Use of a SCID mouse/human lymphoma model to evaluate cytokine-induced killer cells with potent antitumor cell activity

C.B-17 severe combined immune deficient (SCID) mice, which lack functional B and T lymphocytes, allow xenografts and, therefore, can be used to study the biology of human malignancies. Two different human B cell lymphoma cell lines, SU-DHL-4 and OCI-Ly8, which both harbor the t(14;18) chromosomal translocation, were injected into C.B-17 SCID mice. Mice injected intravenously or intraperitoneally developed tumors and died in a dose-dependent manner. The presence of tumor cells in various murine tissues could be demonstrated by a clonogenic tumor assay, staining of frozen sections with a monoclonal antibody (mAb) against a human B cell antigen (CD19), and with the polymerase chain reaction technique. A protocol using cytotoxic effector cells was developed and used to selectively deplete the tumor cells from bone marrow. These cells were developed by growing peripheral blood mononuclear cells in the presence of interferon gamma (IFN-gamma), anti-CD3 mAb, and interleukin 2 (IL-2). The timing of IFN-gamma treatment was critical and optimal if IFN-gamma was added before IL-2 treatment. The cells that were stimulated by IFN-gamma, followed by IL-2, could be expanded by treatment with a mAb directed against CD3. These cells could be further activated by IL-1, but not by tumor necrosis factor alpha. With this protocol, a tumor cell kill of 3 logs was obtained as measured by a clonogenic assay. Interestingly, despite their high cytotoxic activity against lymphoma cells, these cells had little toxicity against a subset of normal human hematopoietic precursor cells (granulocyte/macrophage colony-forming units). These cells were further tested by treating murine bone marrow contaminated with the human lymphoma cell line SU-DHL-4, and injecting these cells into SCID mice to assay for tumor growth in vivo. The animals injected with bone marrow contaminated with SU-DHL-4 cells had enhanced survival if the bone marrow was treated with the cytokine-induced killer cells before infusion. The SCID mouse provides a useful in vivo model for evaluation of new therapeutic approaches for lymphoma treatment. The cytokine-induced killer cells generated as described here could have an important impact on bone marrow purging for autologous bone marrow transplantation as well as for adoptive immunotherapy.