Patient-derived human tumour tissue xenografts in immunodeficient mice: a systematic review

Mouse cancer models have consistently been used to qualify new anticancer drugs in the development of human clinical trials. Rodent tumour models currently being used and which include transgenic tumour models, and those generated by planting human tumour cell lines subcutaneously in immunodeficient mice, do not sufficiently represent clinical cancer characteristics, especially with regard to metastasis and drug sensitivity. The increasingly used patient-derived human tumour tissue (PDTT) xenografts models implanted subcutaneously or in subrenal capsule in immunodeficient mice, such as athymic nude mice or severe combined immune deficient (SCID) mice, may provide a more accurate reflection of human tumour biological characteristics than tumour cell lines. The ability to passage patients’ fresh tumour tissues into large numbers of immunodeficient mice provides possibilities for better preclinical testing of new therapies for the treatment and better outcome for cancer. In this review, we outline the methods of establishing xenograft models, discuss the biological stability of PDTT xenograft models and demonstrate their roles in developing new anticancer drugs and testing therapeutic regimens in cancer patients.     

Genetically engineered mouse models of prostate cancer

Despite major improvement in treatment of early stage localised prostate cancer, the distinction between indolent tumors and those that will become aggressive, as well as the lack of efficient therapies of advanced prostate cancer, remain major health problems. Genetically engineered mice (GEM) have been extensively used to investigate the molecular and cellular mechanisms underlying prostate tumor initiation and progression, and to evaluate new therapies. Moreover, the recent development of conditional somatic mutagenesis in the mouse prostate offers the possibility to generate new models that more faithfully reproduce the human disease, and thus should contribute to improve diagnosis and treatments. The strengths and weaknesses of various models will be discussed, as well as future opportunities.     

From genetic abnormality to metastases: murine models of breast cancer and their use in the development of anticancer therapies

Summary Numerous mouse models of mammary cancer have been developed that mimic selective aspects of human disease. The use of these models has enabled preclinical chemotherapeutic, chemoprevention, and genetic therapy studies in vivo, the testing of gene delivery systems, and the identification of tumour and metastasis suppressor and inducer genes. This review has discussed the most abundantly used murine models of mammary cancer including: spontaneous tumours, chemically induced tumours, orthotopic and syngeneic tumour transplantation, injected tumours, and genetically engineered mice with a predisposition to neoplasia. Each model has been discussed with regards to its merits and limitations for investigating the genetic and phenotypic alterations involved in the human disease as well as its potential usefulness for the development of new treatment strategies. To date no single mouse model is available with the ability to replicate the entire disease process, however, existing models continue to provide invaluable insights into breast cancer induction and progression that would be impossible to obtain using in vitro models alone.     

How to Establish Acute Myeloid Leukemia Xenograft Models Using Immunodeficient Mice

The discovery of the immunodeficient mice has provided a tool for establishing animal models as hosts for invivo analysis of AML. Various model systems have been established in the last few decades, and it is essential thatmurine AML models are developed to exploit more specific, targeted therapeutics. In this review, we concentrate onthe models of AML and discuss the development of immunodeficiency models for understanding of leukemogenesis,describe those now available and their values and document the methods used for establishing and identifyingAML mice models, as well as factors influencing engraftment of human AML in immunodeficient mice. Thus,the function of this article is to provide clinicians and experimentalists with a chronological, comprehensiveappraisal of all AML model systems.     

Development of humanized mouse with patient-derived xenografts for cancer immunotherapy studies: A comprehensive review

Immunotherapy has revolutionized cancer treatment, however, not all tumor types and patients are completely responsive to this approach. Establishing predictive pre-clinical models would allow for more accurate and practical immunotherapeutic drug development. Mouse models are extensively used as in vivo system for biomedical research. However, due to the significant differences between rodents and human, it is impossible to translate most of the findings from mouse models to human. Pharmacological development and advancing personalized medicine using patient-derived xenografts relies on producing mouse models in which murine cells and genes are substituted with their human equivalent. Humanized mice (HM) provide a suitable platform to evaluate xenograft growth in the context of a human immune system. In this review, we discussed recent advances in the generation and application of HM models. We also reviewed new insights into the basic mechanisms, pre-clinical evaluation of onco-immunotherapies, current limitations in the application of these models as well as available improvement strategies. Finally, we pointed out some issues for future studies.     

Patient-like nude-mouse and scid-mouse models of human lung and pleural cancer (review)

Lung cancer is one of the leading causes of cancer-related adult deaths in the world, and its incidence is rising. Patients with malignant pleural effusions are considered to be in the advanced-stage of malignant disease or in the terminal stage. For both, the lack of efficacy of non-surgical treatment modalities is related to the lack of suitable animal models for new drug discovery. Models based on athymic nude mice have been used for human cancer research. However, s.c. or i.m. xenografts usually do not metastasize, or do so at low frequencies. Conversely, human tumor cells orthotopically implanted in the corresponding organs of nude mice result in much higher metastatic rates. By avoiding disruption of tumor integrity, we have found that orthotopic implantation of histologically-intact patient specimens leads to models better reflecting the original behavior of human cancer than models constructed by orthotopic injection of cell suspensions. With the development of a novel thoracotomy procedure, we have constructed 'patient-like' models of lung cancer (SCLC and NSCLC) with regional spread and distant metastases mimicking the clinical features of these diseases. Moreover, by implantation of histologically-intact human tumor tissue in the parietal or visceral pleura of nude mice, we were able to construct models of early- and advanced-pleural cancer, respectively. Indeed, symptoms and survival of pleural-implanted mice closely resemble the clinical situation showing a statistically-significant difference in survival between parietal- and visceral-pleural implanted mice, the latter representing an advanced-stage cancer. Thus such models, reflecting clinical features, should be of great value in the development of new drugs and treatment strategies.     

Prompt tumor formation and maintenance of constitutive NF-kappaB activity of multiple myeloma cells in NOD/SCID/gammacnull mice

Clinically and biologically relevant animal models are indispensable to evaluate both the pathophysiology and strategies for diagnosis and treatment of multiple myeloma (MM). We examined the tumorigenicity of MM cell lines KMM-1 and U-266 in an in vivo cell proliferation model using NOD/SCID/gammacnull (NOG) mice. Two cell lines were inoculated either subcutaneously (s.c.) in the post-auricular region or intravenously (i.v.) in the tail of NOG mice. The KMM-1 cell line produced a progressively growing large tumor with infiltration of the cells expressing human lambda-chain in various organs of all NOG mice, while the U-266 cell line failed to do so. Tumor cells grown in NOG mice maintained the original histomorphology, as well as expression patterns of tumor markers human lambda Ig light chain and VEGF. Tumor progression in mice also correlated with elevation of serum human soluble IL-6R and gp130. Tumor cells sustained a strong NF-kappaB activity in vivo and induced NF-kappaB components were indistinguishable from those in cells cultured in vitro. The rapid and efficient engraftment of the MM cell line in NOG mice suggests that this is a very useful animal model which could provide a novel system in which to clarify the mechanism of growth of cancer cells, as well as to develop new therapeutic regimens against MM.     

Transgenic mouse models of human breast cancer

The pathogenesis of human breast cancer is thought to involve multiple genetic events, the majority of which fall into two categories, gain of function mutations in proto-oncogenes such as c-myc, cyclin D1, ErbB-2 and various growth factors which are involved in supporting cell growth, division and survival, and loss of function mutations in so called 'tumor suppressor' genes, such as p53, which are involved in preventing unrestrained cellular growth. A number of mouse systems exist to address the significance of these mutations in the pathogenesis of breast cancer including transgenic mice expressing high levels of a specific gene in target tissues and knockout mice in which specific genes have been ablated via homologous recombination. More recently, the combination of these techniques to create bigenics as well as the use of 'knockin' and conditional tissue specific gene targeting strategies have allowed the models more reflective of the human disease to be devised. Studies with these models have not only implicated particular genetic events in the progression of the disease but have emphasized the complex, multi-step nature of breast cancer progression. These models also provide the opportunity to study various aspects of the pathogenesis of this disease, from hormonal effects to responses to chemotherapeutic drugs. It is hoped that through the combined use of these models, and the further development of more relevant models, that a deeper understanding of this disease and the generation of new therapeutic agents will result.     

Contributions of human tumor xenografts to anticancer drug development

Mouse models of cancer have consistently been used to qualify new anticancer drugs for study in human clinical trials. The most used models include transplantable murine tumors grown in syngeneic hosts and xenografts of human tumors grown in immunodeficient mice. For the latter systems, retrospective preclinical-clinical correlation studies are available, which suggest that improvements must be made to increase their value. Transgenic, knock-out, and knock-in mouse models and their intercrosses are more recent developments that mirror defined steps of human carcinogenesis. However, their value in predicting clinical results remains to date poorly defined. We take the position that properly used and interpreted human tumor xenografts grown in immunodeficient mice can be useful, although not absolutely predictive of behavior in the clinic, and continue to make contributions to critical clinical development choices.     

Pathogenesis of myelofibrosis with myeloid metaplasia: lessons from mouse models of the disease

The primary genetic lesion(s), as well as the biological processes responsible for the typical structural changes of the bone marrow microenvironment in idiopathic myelofibrosis, are still poorly understood, although a central role in disease pathogenesis has been attributed to the clonal proliferation and defective maturation of megakaryocytes. Two animal models of the disease have been described, that in the last few years significantly contributed to the elucidation of some of the pathogenetic steps of the human disease; these are represented by mice genetically modified to overexpress thrombopoietin and by knock-down mice with defective GATA-1 expression in megakaryocytes (GATA-1(low) mice). This review will outline these murine models, both characterized by extensive accumulation of megakaryocytes in hematopoietic tissues, and illustrate how they provided insights into the identification of some of the molecules and mechanisms responsible for the development of fibrosis and osteosclerosis that present major similarities with those observed in patients with idiopathic myelofibrosis.     

A transgenic mouse line that develops early-onset invasive gastric carcinoma provides a model for carcinoembryonic antigen-targeted tumor therapy

In an attempt to obtain suitable in vivo models for optimizing new tumor therapy strategies for intestinal adenocarcinomas, carcinoembryonic antigen (CEA) promoter/SV40 T antigen gene constructs have been used to generate transgenic mice. One transgenic line (L5496), which contains a 424-bp CEA promoter/SV40 T antigen transgene, exclusively developed multi-focal carcinomas in the pyloric region of the stomach in 100% of the offspring. Tumors were already observable in 37-day-old animals as dysplastic cell foci within the mucosal layer. In 50-day-old mice, the tumor mass was mainly restricted to the mucosa with invasive growth into the submucosal tissue. The animals became moribund at 100-130 days of age due to blockage of the pylorus. At this time, the tumor had penetrated into the duodenum and had invaded all tissue layers within the stomach. In contrast to most other stomach tumor models, this one perfectly matches the development of the most common stomach cancers found in humans. Furthermore, after crossing these mice with mice that are transgenic for the human CEA gene, the double transgenic offspring revealed expression of CEA in the resulting tumors. Thus, as well as being a model for studying gastric carcinoma development and prevention, this system should provide a useful preclinical model for CEA-targeted gastric tumor therapy.     

Animal models of leptomeningeal metastasis

Animal models of leptomeningeal metastasis (LM) should give insight into pathophysiological mechanisms and allow to evaluate new treatments including their neurotoxicity. Syngeneic models use tumor cells of mouse, rat, rabbit or guinea pig origin. Allogeneic models usually rely on human tumor cells injected into nude mice or rats. A review of the literature revealed 2 (4) different glioma, 3 medulloblastoma, 3 (3) carcinoma, 3 (1) melanoma, 1 rhabdomyosarcoma, 2 (8) leukemia and 2 (2) non-Hodgkin's lymphoma allogeneic (syngeneic) models of LM. These models have been used to study the evolution of LM and to evaluate systemic or intrathecal chemotherapy, intrathecal immunotherapy (interleukin-2, interferon-beta, uncoupled, toxin- or radionuclide-conjugated antibodies), and recently gene therapeutic approaches. On the whole, pathophysiological, therapeutic and neurotoxic findings have been well transferable to the clinical situation. Therefore, it seems rational to preclinically test new treatments in an appropriate animal model of LM before using them in patients.     

Metastatic potential of human melanoma cells in nude mice--characterisation of phenotype, cytokine secretion and tumour-associated antigens.

Incidence and mortality of human malignant melanoma has risen rapidly over recent decades. Although the notorious resistance to treatment is characteristic for metastatic malignant melanoma, only a few experimental models have been established to study the metastatic cascade or to test new alternative treatment modalities. Thus, new human models are wanted. Here, we describe the metastatic behaviour of seven human melanoma cell lines derived from two primary cutaneous melanomas (WM 98-1, WM 1341) and five metastases established from liver (UKRV-Mel-4), skin (M7, M13), pleural effusion (UKRV-Mel-2) and lymph node (MV3). All cell lines were analysed for their capacity to grow in nude mice after s.c. and i.v. administration. M13 cells developed liver metastases spontaneously after s.c. injection, and subsequent passages of M13 and M7 melanoma cells caused liver metastases after i.v. injection, whereas MV3 and WM98-1 gave rise to lung metastases, using the same inoculation route. In contrast, WM 1341, UKRV-Mel-2 and UKRV-Mel-4 grew only very slowly in nude mice after s.c. injection and did not cause any metastases after i.v. or s.c. administration. The pattern of metastases or growth kinetics did not correlate with the interleukin 8 or tumour necrosis factor secretion of cell lines. Adhesion molecules and growth factor receptor expression on the cell lines differed widely, as determined by flow cytometry, with the low metastatic cell lines (UKRV-Mel-2, UKRV-Mel-4 and WM 1341) demonstrating a marked reduction in VLA-1 and VLA-5 expression compared with the metastatic lines (M7, M13, MV3 and WM 98-1). Expression of pigment-related proteins such as tyrosinase, TRP-1, TRP-2, Melan-A/MART-1, gp100, MAGE1 or MAGE-3 was not associated with growth and metastatic characteristics of the melanoma cell lines analysed. In conclusion, the established human melanoma cell lines exhibited diverse growth behaviour in nude mice in congruence with some early established prognostic markers such as VLA-1 and VLA-5. The xenografts provide good models for further study of metastatic processes as well as for evaluation of alternative treatment modalities including new pharmaceutical drugs and gene therapeutic targeting using tissue-specific gene regulatory elements for gene targeting.     

Nude mouse models as predictors of chemotherapy in man: thymidine and pyrimidines.

The National Cancer Institute cancer treatment screening program has been reorganized incorporating, as an important feature, a panel of human tumors growing as xenografts in congenitally athymic mice. The new screening program is a prospective experiment in the search for new and more effective agents for the treatment of clinical neoplasia. The new program is described and questions that are being asked prospectively are presented. Data are summarized on the activity against human tumor xenografts for a number of clinically established antitumor drugs and examples are presented in which there is interest in compounds for the clinic on the basis of activity in the new screen. Studies are outlined in which high dose thymidine inhibited the growth of human melanoma and teratocarcinoma transplanted in athymic mice. Studies are discussed employing murine tumors in which marked augmentation of the in vivo antitumor activity of 5-fluorouracil was obtained by combination therapy with the pyrimidine nucleosides thymidine, uridine and cytidine. The desirability of investigating combination chemotherapy with pyrimidine nucleosides and 5-fluorouracil and other pyrimidine antagonists in the treatment of human tumor xenografts is stressed. There is a broad range of investigations that can be conducted in nude mouse models and it is important to conduct such programs in relation to the clinic.     

两种荷人卵巢癌腹腔移植瘤的免疫重建SCID小鼠模型的建立及比较

背景与目的:卵巢癌的死亡率在妇科恶性肿瘤居首位。目前,常规的手术、化疗和放疗难以再提高患者的生存率,因此,生物治疗成为卵巢癌的第四大治疗模式,而生物治疗的评价需要合适的动物模型。本实验目的是建立两种荷人卵巢癌腹腔移植瘤的免疫重建的严重联合免疫缺陷(severecombinedimmunodeficiency,SCID)小鼠模型,通过比较选出较适宜的模型。方法:分别用人卵巢癌细胞株SKOV3细胞和SKOV3.ip1细胞腹腔注射6只和10只C.B17/SCID小鼠建立腹腔瘤模型,比较其生物学、组织学和免疫学特性;并将SKOV3.ip1组小鼠的腹水转种6只小鼠的腹腔,观察成瘤情况。以上22只SCID小鼠均用人外周血淋巴细胞腹腔注射进行人免疫功能重建。结果:用SKOV3细胞和SKOV3.ip1细胞分别建立的两种模型小鼠成瘤率均为100%;成瘤潜伏期分别为20～41天和22～30天(P>0.05);生存期分别为50～78天和32～43天(P<0.0001)。SKOV3.ip1组小鼠的腹水进行转种后有83.3%(5/6)能形成腹腔肿瘤和腹水。两种模型小鼠尸检发现肿瘤分布相似,均形成广泛的盆腔播散;但SKOV3.ip1组伴有0.35～5.60ml血性腹水,而SKOV3组仅有1只有0.20ml腹水。组织学显示两种模型都保持了人卵巢浆液性乳头状腺癌的特点,免疫组化结果表明两种模型都表达卵巢癌相关抗原OC166-9。72.7%(16/22)     

Gene therapy of prostate cancer with the soluble vascular endothelial growth factor receptor Flk1

A variety of novel therapeutic approaches have emerged recently for the treatment of human cancers. We have coupled two of these therapeutic approaches, gene therapy and antiangiogenic therapy and tested them in two murine prostate cancer models Recombinant adenovirus encoding the ligand-binding ectodomain of the VEGF receptor 2 (Flk1) fused to an Fc domain was administered to SCID mice carrying orthotopic human LNCaP tumors as well as to transgenic (TRAMP) mice with spontaneous prostate tumors. Ad Flk1-Fc injection reduced tumor growth by 66% for orthotopic LNCaP tumors and by 42% for spontaneous tumors in TRAMP mice. Microvessel density in the primary tumors was reduced by 68% and 40% in the two models respectively. A decrease in microvessel density was also observed in lymphatic metastases in Ad Flk1-Fc-treated TRAMP mice and was correlated with a decrease in the frequency of regional metastases in the treated animals. Survival time was also extended in the Ad Flk1-Fc-treated TRAMP mice relative to the control-treated animals. Our results suggest that adenoviral delivery of soluble Flk1 receptor can reduce vascular density and prostate tumor growth and prolong survival time in orthotopically implanted tumors as well as in spontaneous prostate tumors in transgenic animals.     

Mouse models for studying angiogenesis and lymphangiogenesis in cancer

The formation of new blood vessels (angiogenesis) is required for the growth of most tumors. The tumor microenvironment also induces lymphangiogenic factors that promote metastatic spread. Anti-angiogenic therapy targets the mechanisms behind the growth of the tumor vasculature. During the past two decades, several strategies targeting blood and lymphatic vessels in tumors have been developed. The blocking of vascular endothelial growth factor (VEGF)/VEGF receptor-2 (VEGFR-2) signaling has proven effective for inhibition of tumor angiogenesis and growth, and inhibitors of VEGF-C/VEGFR-3 involved in lymphangiogenesis have recently entered clinical trials. However, thus far anti-angiogenic treatments have been less effective in humans than predicted on the basis of pre-clinical tests in mice. Intrinsic and induced resistance against anti-angiogenesis occurs in patients, and thus far the clinical benefit of the treatments has been limited to modest improvements in overall survival in selected tumor types. Our current knowledge of tumor angiogenesis is based mainly on experiments performed in tumor-transplanted mice, and it has become evident that these models are not representative of human cancer. For an improved understanding, angiogenesis research needs models that better recapitulate the multistep tumorigenesis of human cancers, from the initial genetic insults in single cells to malignant progression in a proper tissue environment. To improve anti-angiogenic therapies in cancer patients, it is necessary to identify additional molecular targets important for tumor angiogenesis, and to get mechanistic insight into their interactions for eventual combinatorial targeting. The recent development of techniques for manipulating the mammalian genome in a precise and predictable manner has opened up new possibilities for the generation of more reliable models of human cancer that are essential for the testing of new therapeutic strategies. In addition, new imaging modalities that permit visualization of the entire mouse tumor vasculature down to the resolution of single capillaries have been developed in pre-clinical models and will likely benefit clinical imaging.     

Experimental pancreatic cancer: role of species, sex and diet

Pancreatic cancer has been experimentally induced in rodents by chemical carcinogens that have been used to establish "animal models" for pancreatic carcinogenesis. Recent work with transgenic mice provided a new model in which a dominantly expressed oncogene is transmitted in the germ cell line of homozygous strains. Carcinogens are not equally effective in all species and the histologic type of carcinoma that develops is strongly influenced by the species. Carcinomas that develop in rats and mice are predominantly acinar cell type. In contrast, hamsters characteristically develop duct-like carcinomas. The histologic type of carcinoma in hamsters resembles more closely the majority of carcinomas in the human pancreas than is the case in the rat or mouse. Studies in rats and guinea pigs have demonstrated that duct-like and undifferentiated carcinomas, as well as acinar cell carcinomas, can arise from acinar cells. Thus, the relative importance of ductal cells, centroacinar cells, acinar cells and putative stem cells in the origin of pancreatic carcinomas remains to be determined. In most rat models, males have developed a higher incidence rate of pancreatic cancers than females. Experimental evidence shows that testosterone promotes and estrogen inhibits the growth of preneoplastic lesions and cancers in the rat pancreas. Dietary composition and additives influence carcinogenesis in the pancreas. High fat diets promote carcinogenesis in rats and hamsters, and dietary trypsin inhibitors promote in rats. Other dietary additives such as retinoids and antioxidants have inhibited carcinogenesis in the animal models.     

四株人体和大鼠食管癌裸鼠移植瘤株的建立及其生物学特性研究

我们将12例人食管癌手术切除组织接种于NC和BALB/C裸鼠皮下,其中2例获移植成功,裸鼠间传代达32代,历时2年余,建立了二株人食管癌裸鼠移植瘤,分别为人食管鳞状细胞癌裸鼠移植瘤(HEC_2)和人食管腺鳞癌裸鼠移植瘤(HEC_6)。两移植瘤具有潜伏期短、移植成功率高(100％)、荷瘤存活时间长及生物学特性稳定等特点。并在建立大鼠食管癌细胞系(RE25—3.)的基础上,建立了二株大鼠食管癌裸鼠移植瘤(RE25/N和RE66/N)。此四株人体和大鼠食管癌裸鼠移植瘤株为食管癌病因、发病机理及治疗的研究,提供了极好的模型。     

Magnetic resonance imaging of the pancreas and pancreatic tumors in a mouse orthotopic model of human cancer

Pancreatic adenocarcinoma has a rising incidence and a very poor survival rate. To develop new treatment strategies, extensive research is performed on animal models of pancreatic cancer. Orthotopic pancreatic tumors models, where the tumor is implanted into the pancreas, resemble the human disease more closely than subcutaneous tumor models, yet are difficult to monitor. In our study we report a magnetic resonance imaging (MRI) approach to visualize the pancreas in mice and to monitor orthotopically implanted pancreatic tumors. An MRI scanner was used to image normal murine pancreas and the pancreas of mice implanted with a human pancreatic adenocarcinoma cell line. Gadolinium (Gd)-DTPA-enhanced T1- and T2-weighted standard sequences were used with the objective to identify the pancreas and to monitor the growth of orthotopic tumors during 30 days. The pancreas as well as the implanted tumors could be easily identified using MRI. On T2-weighted images, the implanted tumors were easily visualized at the implantation side with high signal intensity. After application of a contrast agent, the tumors showed an enhancement. Heterogeneities within the tumor could be delineated, corresponding to histology, and the size of the tumor could be measured precisely. MR serves as a noninvasive high-resolution image modality to monitor murine pancreas as well as size, growth and even areas of heterogeneity in orthotopic pancreatic tumors.