Early development of human lymphomas in a prostate cancer xenograft program using triple knock-out immunocompromised mice

PDX Models in Theranostic Applications: Generation and Screening for B Cell Lymphoma of Human Origin

This MIB guide briefly summarizes the generation of patient-derived xenografts (PDXs) and highlights the importance of validating PDX models for the presence of B cell lymphoma of human origin before their use in radiotheranostic applications. The use of this protocol will allow researchers to learn different methods for screening PDX models for Epstein-Barr virus (EBV)-infected B cell lymphoma.

PET and Optical Imaging of Caveolin-1 in Gastric Tumors

Previous studies have suggested tumoral caveolin-1 (CAV1) as a predictive biomarker for the response to anti-HER2 antibody drug therapies in gastric tumors. In this study, radiolabeled and fluorescently labeled anti-CAV1 antibodies were developed and tested as an immunoPET or optical imaging agent to detect CAV1 in HER2-positive/CAV1-high NCIN87 gastric tumors. The expression of CAV1 receptors in NCIN87 gastric tumors and nontumor murine organs was determined by Western blot. Binding assays were performed to validate the anti-CAV1 antibody specificity for CAV1-expressing NCIN87 cancer cells. Subcutaneous and orthotopic NCIN87 xenografts were used for PET imaging and ex vivo biodistribution of the radioimmunoconjugate. Additional HER2-PET and CAV1-optical imaging was also performed to determine CAV1 in the HER2-positive tumors. 89Zr-labeled anti-CAV1 antibody was able to bind to CAV1-expressing NCIN87 cells with a Bmax value of 2.7 × 103 CAV1 receptors/cell in vitro. ImmunoPET images demonstrated the localization of the antibody in subcutaneous NCIN87 xenografts. In the orthotopic model, CAV1 expression was also observed by optical imaging in the HER2-positive tumors previously imaged with HER2-PET. Ex vivo biodistribution analysis further confirmed these imaging results. The preclinical data from this study demonstrate the potential of using CAV1-PET and optical imaging for detecting gastric tumors.

Generation, evolution, interfering factors, applications, and challenges of patient-derived xenograft models in immunodeficient mice

Establishing appropriate preclinical models is essential for cancer research. Evidence suggests that cancer is a highly heterogeneous disease. This follows the growing use of cancer models in cancer research to avoid these differences between xenograft tumor models and patient tumors. In recent years, a patient-derived xenograft (PDX) tumor model has been actively generated and applied, which preserves both cell-cell interactions and the microenvironment of tumors by directly transplanting cancer tissue from tumors into immunodeficient mice. In addition to this, the advent of alternative hosts, such as zebrafish hosts, or in vitro models (organoids and microfluidics), has also facilitated the advancement of cancer research. However, they still have a long way to go before they become reliable models. The development of immunodeficient mice has enabled PDX to become more mature and radiate new vitality. As one of the most reliable and standard preclinical models, the PDX model in immunodeficient mice (PDX-IM) exerts important effects in drug screening, biomarker development, personalized medicine, co-clinical trials, and immunotherapy. Here, we focus on the development procedures and application of PDX-IM in detail, summarize the implications that the evolution of immunodeficient mice has brought to PDX-IM, and cover the key issues in developing PDX-IM in preclinical studies.

Phenotyping of lymphoproliferative tumours generated in xenografts of non-small cell lung cancer

Background

Patient-derived xenograft (PDX) models involve the engraftment of tumour tissue in immunocompromised mice and represent an important pre-clinical oncology research method. A limitation of non-small cell lung cancer (NSCLC) PDX model derivation in NOD-scid IL2Rgammanull (NSG) mice is that a subset of initial engraftments are of lymphocytic, rather than tumour origin.

Methods

The immunophenotype of lymphoproliferations arising in the lung TRACERx PDX pipeline were characterised. To present the histology data herein, we developed a Python-based tool for generating patient-level pathology overview figures from whole-slide image files; PATHOverview is available on GitHub (https://github.com/EpiCENTR-Lab/PATHOverview).

Results

Lymphoproliferations occurred in 17.8% of lung adenocarcinoma and 10% of lung squamous cell carcinoma transplantations, despite none of these patients having a prior or subsequent clinical history of lymphoproliferative disease. Lymphoproliferations were predominantly human CD20+ B cells and had the immunophenotype expected for post-transplantation diffuse large B cell lymphoma with plasma cell features. All lymphoproliferations expressed Epstein-Barr-encoded RNAs (EBER). Analysis of immunoglobulin light chain gene rearrangements in three tumours where multiple tumour regions had resulted in lymphoproliferations suggested that each had independent clonal origins.

Discussion

Overall, these data suggest that B cell clones with lymphoproliferative potential are present within primary NSCLC tumours, and that these are under continuous immune surveillance. Since these cells can be expanded following transplantation into NSG mice, our data highlight the value of quality control measures to identify lymphoproliferations within xenograft pipelines and support the incorporation of strategies to minimise lymphoproliferations during the early stages of xenograft establishment pipelines.

The future of patient-derived xenografts in prostate cancer research

Patient-derived xenografts (PDXs) are generated by engrafting human tumours into mice. Serially transplantable PDXs are used to study tumour biology and test therapeutics, linking the laboratory to the clinic. Although few prostate cancer PDXs are available in large repositories, over 330 prostate cancer PDXs have been established, spanning broad clinical stages, genotypes and phenotypes. Nevertheless, more PDXs are needed to reflect patient diversity, and to study new treatments and emerging mechanisms of resistance. We can maximize the use of PDXs by exchanging models and datasets, and by depositing PDXs into biorepositories, but we must address the impediments to accessing PDXs, such as institutional, ethical and legal agreements. Through collaboration, researchers will gain greater access to PDXs representing diverse features of prostate cancer.

Modeling the Tumor Microenvironment and Cancer Immunotherapy in Next-Generation Humanized Mice

Cancer immunotherapy has brought significant clinical benefits to numerous patients with malignant disease. However, only a fraction of patients experiences complete and durable responses to currently available immunotherapies. This highlights the need for more effective immunotherapies, combination treatments and predictive biomarkers. The molecular properties of a tumor, intratumor heterogeneity and the tumor immune microenvironment decisively shape tumor evolution, metastasis and therapy resistance and are therefore key targets for precision cancer medicine. Humanized mice that support the engraftment of patient-derived tumors and recapitulate the human tumor immune microenvironment of patients represent a promising preclinical model to address fundamental questions in precision immuno-oncology and cancer immunotherapy. In this review, we provide an overview of next-generation humanized mouse models suitable for the establishment and study of patient-derived tumors. Furthermore, we discuss the opportunities and challenges of modeling the tumor immune microenvironment and testing a variety of immunotherapeutic approaches using human immune system mouse models.

Patient-derived xenograft (PDX) models, applications and challenges in cancer research

The establishing of the first cancer models created a new perspective on the identification and evaluation of new anti-cancer therapies in preclinical studies. Patient-derived xenograft models are created by tumor tissue engraftment. These models accurately represent the biology and heterogeneity of different cancers and recapitulate tumor microenvironment. These features have made it a reliable model along with the development of humanized models. Therefore, they are used in many studies, such as the development of anti-cancer drugs, co-clinical trials, personalized medicine, immunotherapy, and PDX biobanks. This review summarizes patient-derived xenograft models development procedures, drug development applications in various cancers, challenges and limitations.

Caveolin-1 temporal modulation enhances antibody drug efficacy in heterogeneous gastric cancer

Resistance mechanisms and heterogeneity in HER2-positive gastric cancers (GC) limit Trastuzumab benefit in 32% of patients, and other targeted therapies have failed in clinical trials. Using patient samples, patient-derived xenografts (PDXs), partially humanized biological models, and HER2-targeted imaging technologies we demonstrate the role of caveolin-1 (CAV1) as a complementary biomarker in GC selection for Trastuzumab therapy. In retrospective analyses of samples from patients enrolled on Trastuzumab trials, the CAV1-high profile associates with low membrane HER2 density and low patient survival. We show a negative correlation between CAV1 tumoral protein levels – a major protein of cholesterol-rich membrane domains – and Trastuzumab-drug conjugate TDM1 tumor uptake. Finally, CAV1 depletion using knockdown or pharmacologic approaches (statins) increases antibody drug efficacy in tumors with incomplete HER2 membranous reactivity. In support of these findings, background statin use in patients associates with enhanced antibody efficacy. Together, this work provides preclinical justification and clinical evidence that require prospective investigation of antibody drugs combined with statins to delay drug resistance in tumors.

Clinical evidences have demonstrated limited efficacy of HER2-targeted therapies in patients with gastric cancer (GC). Here the authors show that survival benefit to anti-HER2 antibody Trastuzumab is reduced in GC patients with high levels of the caveolin-1 and that, in preclinical cancer models, antibody drug efficacy can be improved by modulating caveolin-1 levels with cholesterol-depleting drugs, statins.

Establishment of an Ex Vivo Tissue Culture Model for Evaluation of Antitumor Efficacy in Clear Cell Renal Cell Carcinoma

There are many potential immunotherapeutic targets for cancer immunotherapy, which should be assessed for efficacy before they enter clinical trials. Here we established an ex vivo cultured patient-derived tumor tissue model to evaluate antitumor effectiveness of one VISTA inhibitor, given that our previous study showed that VISTA was selectively highly expressed in human clear cell renal cell carcinoma (ccRCC) tumors. We observed that all the tested patients responded to the anti-VISTA monoclonal antibody as manifested by TNF-α production, but only a small fraction were responders to the anti-PD-1 antibody. Co-blockade of VISTA and PD-1 resulted in a synergistic effect in 20% of RCC patients. Taken together, these findings indicate that this ex vivo tumor slice culture model represents a viable tool to evaluate antitumor efficacies for the inhibitors of immune checkpoints and further supports that VISTA could serve as a promising target for immunotherapy in ccRCC.

Patient-derived tumor models are attractive tools to repurpose drugs for ovarian cancer treatment: Pre-clinical updates

Despite advances in understanding of ovarian cancer biology, the progress in translation of research findings into new therapies is still slow. It is associated in part with limitations of commonly used cancer models such as cell lines and genetically engineered mouse models that lack proper representation of diversity and complexity of actual human tumors. In addition, the development of de novo anticancer drugs is a lengthy and expensive process. A promising alternative to new drug development is repurposing existing FDA-approved drugs without primary oncological purpose. These approved agents have known pharmacokinetics, pharmacodynamics, and toxicology and could be approved as anticancer drugs quicker and at lower cost. To successfully translate repurposed drugs to clinical application, an intermediate step of pre-clinical animal studies is required. To address challenges associated with reliability of tumor models for pre-clinical studies, there has been an increase in development of patient-derived xenografts (PDXs), which retain key characteristics of the original patient’s tumor, including histologic, biologic, and genetic features. The expansion and utilization of clinically and molecularly annotated PDX models derived from different ovarian cancer subtypes could substantially aid development of new therapies or rapid approval of repurposed drugs to improve treatment options for ovarian cancer patients.

The MURAL collection of prostate cancer patient-derived xenografts enables discovery through preclinical models of uro-oncology

Preclinical testing is a crucial step in evaluating cancer therapeutics. We aimed to establish a significant resource of patient-derived xenografts (PDXs) of prostate cancer for rapid and systematic evaluation of candidate therapies. The PDX collection comprises 59 tumors collected from 30 patients between 2012-2020, coinciding with availability of abiraterone and enzalutamide. The PDXs represent the clinico-pathological and genomic spectrum of prostate cancer, from treatment-naïve primary tumors to castration-resistant metastases. Inter- and intra-tumor heterogeneity in adenocarcinoma and neuroendocrine phenotypes is evident from bulk and single-cell RNA sequencing data. Organoids can be cultured from PDXs, providing further capabilities for preclinical studies. Using a 1 x 1 x 1 design, we rapidly identify tumors with exceptional responses to combination treatments. To govern the distribution of PDXs, we formed the Melbourne Urological Research Alliance (MURAL). This PDX collection is a substantial resource, expanding the capacity to test and prioritize effective treatments for prospective clinical trials in prostate cancer.

Characterization of the large-scale Japanese patient-derived xenograft (J-PDX) library

The use of patient‐derived xenografts (PDXs) has recently attracted attention as a drug discovery platform with a high predictive clinical efficacy and a preserved tumor heterogeneity. Given the racial differences in genetic variations, it would be desirable to establish a PDX library from Japanese cancer patients on a large scale. We thus tried to construct the Japanese PDX (J‐PDX) library with a detailed clinical information for further clinical utilization. Between August 2018 and May 2020, a total of 1126 cancer specimens from 1079 patients were obtained at the National Cancer Center Hospital and National Cancer Center Hospital East, Japan, and were immediately transplanted to immunodeficient mice at the National Cancer Center Research Institute. A total of 298 cross‐cancer PDXs were successfully established. The time to engraftment varied greatly by cancer subtypes, especially in the first passage. The engraftment rate was strongly affected by the clinical stage and survival time of the original patients. Approximately 1 year was needed from tumor collection to the time when coclinical trials were conducted to test the clinical utility. The 1‐year survival rates of the patients who were involved in establishing the PDX differed significantly, from 95.6% for colorectal cancer to 56.3% for lung cancer. The J‐PDX library consisting of a wide range of cancer subtypes has been successfully established as a platform for drug discovery and development in Japan. When conducting coclinical trials, it is necessary to consider the target cancer type, stage, and engraftment rate in light of this report.

Patient-derived xenografts and organoids model therapy response in prostate cancer

Therapy resistance and metastatic processes in prostate cancer (PCa) remain undefined, due to lack of experimental models that mimic different disease stages. We describe an androgen-dependent PCa patient-derived xenograft (PDX) model from treatment-naïve, soft tissue metastasis (PNPCa). RNA and whole-exome sequencing of the PDX tissue and organoids confirmed transcriptomic and genomic similarity to primary tumor. PNPCa harbors BRCA2 and CHD1 somatic mutations, shows an SPOP/FOXA1-like transcriptomic signature and microsatellite instability, which occurs in 3% of advanced PCa and has never been modeled in vivo. Comparison of the treatment-naïve PNPCa with additional metastatic PDXs (BM18, LAPC9), in a medium-throughput organoid screen of FDA-approved compounds, revealed differential drug sensitivities. Multikinase inhibitors (ponatinib, sunitinib, sorafenib) were broadly effective on all PDX- and patient-derived organoids from advanced cases with acquired resistance to standard-of-care compounds. This proof-of-principle study may provide a preclinical tool to screen drug responses to standard-of-care and newly identified, repurposed compounds.

The Essential Factors of Establishing Patient-derived Tumor Model

Establishing an applicable preclinical model is vital for translational cancer research. Patient-derived xenograft has been important preclinical model systems and widely used for cancer research. Patient-derived xenograft models that represent the tumors of the patients are necessary to better translate research discoveries and to test potential therapeutic approaches. However, research in this field is hampered by the limited engraftment rate. In this review, we go over a large number of researches on patient-derived xenograft transplantation and firstly systematically summarize the main factors in methodology to successfully establish models. These results will be applied to the development of patient-derived xenograft leading to better preclinical research.

Patient-derived tumour models for personalized therapeutics in urological cancers

Preclinical knowledge of dysregulated pathways and potential biomarkers for urological cancers has undergone limited translation into the clinic. Moreover, the low approval rate of new anticancer drugs and the heterogeneous drug responses in patients indicate that current preclinical models do not always reflect the complexity of malignant disease. Patient-derived tumour models used in preclinical uro-oncology research include 3D culture systems, organotypic tissue slices and patient-derived xenograft models. Technological innovations have enabled major improvements in the capacity of these tumour models to reproduce the clinical complexity of urological cancers. Each type of patient-derived model has inherent advantages and limitations that can be exploited, either alone or in combination, to gather specific knowledge on clinical challenges and address unmet clinical needs. Nevertheless, few opportunities exist for patients with urological cancers to benefit from personalized therapeutic approaches. Clinical validation of experimental data is needed to facilitate the translation and implementation of preclinical knowledge into treatment decision making.

Mouse models of high-risk neuroblastoma

Informative and realistic mouse models of high-risk neuroblastoma are central to understanding mechanisms of tumour initiation, progression, and metastasis. They also play vital roles in validating tumour drivers and drug targets, as platforms for assessment of new therapies and in the generation of drug sensitivity data that can inform treatment decisions for individual patients. This review will describe genetically engineered mouse models of specific subsets of high-risk neuroblastoma, the development of patient-derived xenograft models that more broadly represent the diversity and heterogeneity of the disease, and models of primary and metastatic disease. We discuss the research applications, advantages, and limitations of each model type, the importance of model repositories and data standards for supporting reproducible, high-quality research, and potential future directions for neuroblastoma mouse models.

PDX: Moving Beyond Drug Screening to Versatile Models for Research Discovery

Patient-derived xenografts (PDXs) are tools of the trade for many researchers from all disciplines and medical specialties. Most endocrinologists, and especially those working in oncology, commonly use PDXs for preclinical drug testing and development, and over the last decade large collections of PDXs have emerged across all tumor streams. In this review, we examine how the field has evolved to include PDXs as versatile resources for research discoveries, providing evidence for guidelines and changes in clinical practice.

Critical evaluation of the subcutaneous engraftments of hormone naïve primary prostate cancer

Background

Patient-derived xenografts (PDXs) are considered to better recapitulate the histopathological and molecular heterogeneity of human cancer than other preclinical models. Despite technological advances, PDX models from hormone naïve primary prostate cancer are scarce. We performed a detailed analysis of PDX methodology using a robust subcutaneous model and fresh tissues from patients with primary hormone naïve prostate cancer.

Methods

Clinical prostate tumor specimens (n=26, Gleason score 6-10) were collected from robotic-assisted laparoscopic radical prostatectomies at Turku University Hospital (Turku, Finland), cut into pieces, and implanted subcutaneously into 84 immunodeficient mice. Engraftments and the adjacent material from prostatic surgical specimens were compared using histology, immunohistochemistry and DNA sequencing.

Results

The probability of a successful engraftment correlated with the presence of carcinoma in the implanted tissue. Tumor take rate was 41%. Surprisingly, mouse hormone supplementation inhibited tumor take rate, whereas the degree of mouse immunodeficiency did not have an effect. Histologically, the engrafted tumors closely mimicked their parental tumors, and the Gleason grades and copy number variants of the engraftments were similar to those of their primary tumors. Expression levels of androgen receptor, prostate-specific antigen, and keratins were retained in engraftments, and a detailed genomic analysis revealed high fidelity of the engraftments with their corresponding primary tumors. However, in the second or third passage of tumors, the carcinoma areas were almost completely replaced by benign tissue with frequent degenerative or metaplastic changes.

Conclusions

Subcutaneous primary prostate engraftments preserve the phenotypic and genotypic landscape. Thus, they serve a potential model for personalized medicine and preclinical research but their use may be limited to the first passage.

Mouse models of colorectal cancer: Past, present and future perspectives

Colorectal cancer (CRC) is the third most common diagnosed malignancy among both sexes in the United States as well as in the European Union. While the incidence and mortality rates in western, high developed countries are declining, reflecting the success of screening programs and improved treatment regimen, a rise of the overall global CRC burden can be observed due to lifestyle changes paralleling an increasing human development index. Despite a growing insight into the biology of CRC and many therapeutic improvements in the recent decades, preclinical in vivo models are still indispensable for the development of new treatment approaches. Since the development of carcinogen-induced rodent models for CRC more than 80 years ago, a plethora of animal models has been established to study colon cancer biology. Despite tenuous invasiveness and metastatic behavior, these models are useful for chemoprevention studies and to evaluate colitis-related carcinogenesis. Genetically engineered mouse models (GEMM) mirror the pathogenesis of sporadic as well as inherited CRC depending on the specific molecular pathways activated or inhibited. Although the vast majority of CRC GEMM lack invasiveness, metastasis and tumor heterogeneity, they still have proven useful for examination of the tumor microenvironment as well as systemic immune responses; thus, supporting development of new therapeutic avenues. Induction of metastatic disease by orthotopic injection of CRC cell lines is possible, but the so generated models lack genetic diversity and the number of suited cell lines is very limited. Patient-derived xenografts, in contrast, maintain the pathological and molecular characteristics of the individual patient’s CRC after subcutaneous implantation into immunodeficient mice and are therefore most reliable for preclinical drug development – even in comparison to GEMM or cell line-based analyses. However, subcutaneous patient-derived xenograft models are less suitable for studying most aspects of the tumor microenvironment and anti-tumoral immune responses. The authors review the distinct mouse models of CRC with an emphasis on their clinical relevance and shed light on the latest developments in the field of preclinical CRC models.

Accelerating development of high-risk neuroblastoma patient-derived xenograft models for preclinical testing and personalised therapy

Background

Predictive preclinical models play an important role in the assessment of new treatment strategies and as avatar models for personalised medicine; however, reliable and timely model generation is challenging. We investigated the feasibility of establishing patient-derived xenograft (PDX) models of high-risk neuroblastoma from a range of tumour-bearing patient materials and assessed approaches to improve engraftment efficiency.

Methods

PDX model development was attempted in NSG mice by using tumour materials from 12 patients, including primary and metastatic solid tumour samples, bone marrow, pleural fluid and residual cells from cytogenetic analysis. Subcutaneous, intramuscular and orthotopic engraftment were directly compared for three patients.

Results

PDX models were established for 44% (4/9) of patients at diagnosis and 100% (5/5) at relapse. In one case, attempted engraftment from pleural fluid resulted in an EBV-associated atypical lymphoid proliferation. Xenogeneic graft versus host disease was observed with attempted engraftment from lymph node and bone marrow tumour samples but could be prevented by T-cell depletion. Orthotopic engraftment was more efficient than subcutaneous or intramuscular engraftment.

Conclusions

High-risk neuroblastoma PDX models can be reliably established from diverse sample types. Orthotopic implantation allows more rapid model development, increasing the likelihood of developing an avatar model within a clinically useful timeframe.

Corruption of neuroblastoma patient derived xenografts with human T cell lymphoma

BACKGROUND

Patient derived xenografts (PDXs) provide a unique opportunity for investigators to study tumor cell activity, response to therapeutics, and resistance patterns without exposing the human patient to experimental compounds, and thereby play a crucial role in pre-clinical evaluation of new therapies. It has been reported that PDXs may undergo a transformation to lymphoma, most commonly associated with Epstein Barr virus (EBV). If the character of a xenograft becomes compromised and remains undetected, it could have a detrimental impact on the research community as a whole. Our lab has established a number of pediatric solid tumor PDXs which accurately recapitulate the human tumors following several passages. One particular neuroblastoma PDX was noted to grow quickly and with an unusual phenotype, leading us to hypothesize that this PDX had undergone a transformation.

METHODS

The PDX in question was investigated with histology, immunohistochemistry (IHC), EBER in situ hybridization, and PCR to determine its identity.

RESULTS

Histology on the tumor revealed a small, round blue cell tumor similar to the original neuroblastoma from which it was derived. IHC staining showed that the tumor was composed of lymphocytes that were CD3 positive, <5% CD4 positive, and CD20 negative. The cells were Epstein Barr virus negative. PCR demonstrated that the tumor was human and not murine in origin.

CONCLUSION

These findings indicate that a human T Cell lymphoma developed in place of this neuroblastoma PDX. Changes in PDX identity such as this one will significantly impact studies utilizing pediatric PDXs and the mechanism by which this occurred warrants further investigation.

Application of Highly Immunocompromised Mice for the Establishment of Patient-Derived Xenograft (PDX) Models

Patient-derived xenograft (PDX) models are created by engraftment of patient tumor tissues into immunocompetent mice. Since a PDX model retains the characteristics of the primary patient tumor including gene expression profiles and drug responses, it has become the most reliable in vivo human cancer model. The engraftment rate increases with the introduction of Non-obese diabetic Severe combined immunodeficiency (NOD/SCID)-based immunocompromised mice, especially the NK-deficient NOD strains NOD/SCID/interleukin-2 receptor gamma chain(IL2Rγ)null (NOG/NSG) and NOD/SCID/Jak3(Janus kinase 3)null (NOJ). Success rates differ with tumor origin: gastrointestinal tumors acquire a higher engraftment rate, while the rate is lower for breast cancers. Subcutaneous transplantation is the most popular method to establish PDX, but some tumors require specific environments, e.g., orthotropic or renal capsule transplantation. Human hormone treatment is necessary to establish hormone-dependent cancers such as prostate and breast cancers. PDX mice with human hematopoietic and immune systems (humanized PDX) are powerful tools for the analysis of tumor-immune system interaction and evaluation of immunotherapy response. A PDX biobank equipped with patients' clinical data, gene-expression patterns, mutational statuses, tumor tissue architects, and drug responsiveness will be an authoritative resource for developing specific tumor biomarkers for chemotherapeutic predictions, creating individualized therapy, and establishing precise cancer medicine.

Testicular germ cell tumor: a comprehensive review

Testicular tumors are the most common tumors in adolescent and young men and germ cell tumors (TGCTs) account for most of all testicular cancers. Increasing incidence of TGCTs among males provides strong motivation to understand its biological and genetic basis. Gains of chromosome arm 12p and aneuploidy are nearly universal in TGCTs, but TGCTs have low point mutation rate. It is thought that TGCTs develop from premalignant intratubular germ cell neoplasia that is believed to arise from the failure of normal maturation of gonocytes during fetal or postnatal development. Progression toward invasive TGCTs (seminoma and nonseminoma) then occurs after puberty. Both inherited genetic factors and environmental risk factors emerge as important contributors to TGCT susceptibility. Genome-wide association studies have so far identified more than 30 risk loci for TGCTs, suggesting that a polygenic model fits better with the genetic landscape of the disease. Despite high cure rates because of its particular sensitivity to platinum-based chemotherapy, exploration of mechanisms underlying the occurrence, progression, metastasis, recurrence, chemotherapeutic resistance, early diagnosis and optional clinical therapeutics without long-term side effects are urgently needed to reduce the cancer burden in this underserved age group. Herein, we present an up-to-date review on clinical challenges, origin and progression, risk factors, TGCT mouse models, serum diagnostic markers, resistance mechanisms, miRNA regulation, and database resources of TGCTs. We appeal that more attention should be paid to the basic research and clinical diagnosis and treatment of TGCTs.

Movember GAP1 PDX project: An international collection of serially transplantable prostate cancer patient-derived xenograft (PDX) models

BACKGROUND

While it has been challenging to establish prostate cancer patient-derived xenografts (PDXs), with a take rate of 10-40% and long latency time, multiple groups throughout the world have developed methods for the successful establishment of serially transplantable human prostate cancer PDXs using a variety of immune deficient mice. In 2014, the Movember Foundation launched a Global Action Plan 1 (GAP1) project to support an international collaborative prostate cancer PDX program involving eleven groups. Between these Movember consortium members, a total of 98 authenticated human prostate cancer PDXs were available for characterization. Eighty three of these were derived directly from patient material, and 15 were derived as variants of patient-derived material via serial passage in androgen deprived hosts. A major goal of the Movember GAP1 PDX project was to provide the prostate cancer research community with a summary of both the basic characteristics of the 98 available authenticated serially transplantable human prostate cancer PDX models and the appropriate contact information for collaborations. Herein, we report a summary of these PDX models.

METHODS

PDX models were established in immunocompromised mice via subcutaneous or subrenal-capsule implantation. Dual-label species (ie, human vs mouse) specific centromere and telomere Fluorescence In Situ Hybridization (FISH) and immuno-histochemical (IHC) staining of tissue microarrays (TMAs) containing replicates of the PDX models were used for characterization of expression of a number of phenotypic markers important for prostate cancer including AR (assessed by IHC and FISH), Ki67, vimentin, RB1, P-Akt, chromogranin A (CgA), p53, ERG, PTEN, PSMA, and epithelial cytokeratins.

RESULTS

Within this series of PDX models, the full spectrum of clinical disease stages is represented, including androgen-sensitive and castration-resistant primary and metastatic prostate adenocarcinomas as well as prostate carcinomas with neuroendocrine differentiation. The annotated clinical characteristics of these PDXs were correlated with their marker expression profile.

CONCLUSION

Our results demonstrate the clinical relevance of this series of PDXs as a platform for both basic science studies and therapeutic discovery/drug development. The present report provides the prostate cancer community with a summary of the basic characteristics and a contact information for collaborations using these models.

A systematic review of the validity of patient derived xenograft (PDX) models: the implications for translational research and personalised medicine

Patient-derived xenograft (PDX) models are increasingly being used in oncology drug development because they offer greater predictive value than traditional cell line models. Using novel tools to critique model validity and reliability we performed a systematic review to identify all original publications describing the derivation of PDX models of colon, prostate, breast and lung cancer. Validity was defined as the ability to recapitulate the disease of interest. The study protocol was registered with the Collaborative Approach to Meta-Analysis and Review of Animal Data from Experimental Studies (CAMARADES). Searches were performed in Embase, MEDLINE and Pubmed up to July 2017. A narrative data synthesis was performed. We identified 105 studies of model validations; 29 for breast, 29 for colon, 25 for lung, 23 for prostate and 4 for multiple tissues. 133 studies were excluded because they did not perform any validation experiments despite deriving a PDX. Only one study reported following the ARRIVE guidelines; developed to improve the standard of reporting for animal experimentation. Remarkably, half of all breast (52%) and prostate (50%) studies were judged to have high concern, in contrast to 16% of colon and 28% of lung studies. The validation criteria that most commonly failed (evidence to the contrary) were: tissue of origin not proven and histology of the xenograft not comparable to the parental tumour. Overall, most studies were categorized as unclear because one or more validation conditions were not reported, or researchers failed to provide data for a proportion of their models. For example, failure to demonstrate tissue of origin, response to standard of care agents and to exclude development of lymphoma. Validation tools have the potential to improve reproducibility, reduce waste in research and increase the success of translational studies.

Patient-derived xenograft mouse models: A high fidelity tool for individualized medicine

Patient-derived xenograft (PDX) mouse models involve the direct transfer of fresh human tumor samples into immunodeficient mice following surgical resection or other medical operations. Gene expression in tumors may be maintained by serial passages of tumors from mouse to mouse. These models aid research into tumor biology and pharmacology without manual manipulation of cell cultures in vitro. and are widely used in individualized cancer therapy/translational medicine, drug development and coclinical trials. PDX models exhibit higher predictive values for clinical outcomes than cell line-derived xenograft models and genetically engineered mouse models. However, PDX models are associated with certain challenges in clinical application. The present study reviewed current collections of PDX models and assessed the challenges and future directions of this field.

An ex vivo Tissue Culture Model for the Assessment of Individualized Drug Responses in Prostate and Bladder Cancer

Urological malignancies, including prostate and bladder carcinoma, represent a major clinical problem due to the frequent occurrence of therapy resistance and the formation of incurable distant metastases. As a result, there is an urgent need for versatile and predictive disease models for the assessment of the individualized drug response in urological malignancies. Compound testing on ex vivo cultured patient-derived tumor tissues could represent a promising approach. In this study, we have optimized an ex vivo culture system of explanted human prostate and bladder tumors derived from clinical specimens and human cancer cell lines xenografted in mice. The explanted and cultured tumor slices remained viable and tissue architecture could be maintained for up to 10 days of culture. Treatment of ex vivo cultured human prostate and bladder cancer tissues with docetaxel and gemcitabine, respectively, resulted in a dose-dependent anti-tumor response. The dose-dependent decrease in tumor cells upon administration of the chemotherapeutic agents was preceded by an induction of apoptosis. The implementation and optimization of the tissue slice technology may facilitate the assessment of anti-tumor efficacies of existing and candidate pharmacological agents in the complex multicellular neoplastic tissues from prostate and bladder cancer patients. Our model represents a versatile “near-patient” tool to determine tumor-targeted and/or stroma-mediated anti-neoplastic responses, thus contributing to the field of personalized therapeutics.

Methodology, Criteria, and Characterization of Patient-Matched Thyroid Cell Lines and Patient-Derived Tumor Xenografts

OBJECTIVE

To investigate the molecular underpinnings of thyroid cancer, preclinical cell line models are crucial; however, ∼40% of these have been proven to be either duplicates of existing thyroid lines or even nonthyroid-derived lines or are not derived from humans at all. Therefore, we set out to establish procedures and guidelines that should proactively avoid these problems, which facilitated the creation of criteria to make valid preclinical models for thyroid cancer research.

DESIGN

Based on our recommendations, we systematically characterized all new cell lines that we generated by a standardized approach that included (1) determination of human origin, (2) exclusion of lymphoma, (3) DNA fingerprinting and histological comparisons to establish linkage to presumed tissue of origin, (4) examining thyroid differentiation by screening two to three thyroid markers, (5) examination of biological behavior (growth rate, tumorigenicity), and (6) presence of common thyroid cancer genetic changes (TP53, BRAF, PTEN, PIK3CA, RAS, TERT promoter, RET/PTC, PAX8/PPARγ, NF1, and EIF1AX).

RESULTS

We established seven new thyroid cell lines (LAM136, EAM306, SDAR1, SDAR2, JEM493, THJ529, and THJ560) out of 294 primary culture attempts, and 10 patient-derived tumor xenografts (PDTXs; MC-Th-95, MC-Th-374, MC-Th-467, MC-Th-491, MC-Th-493, MC-Th-504, MC-Th-524, MC-Th-529, MC-Th-560, and MC-Th-562) out of 67 attempts. All were successfully validated by our protocols.

CONCLUSIONS

This standardized approach for cell line and PDTX characterization should prevent (or detect) future cross-contamination and ensure that only valid preclinical models are used for thyroid cancer research.

The what, when, and why of human prostate cancer xenografts

BACKGROUND

Presently, ∼85 serially transplantable human prostate cancer xenografts spanning the phenotypic, epigenetic, and genetic heterogeneity seen clinically are available in a variety of laboratories throughout the world. If distributed to the prostate cancer research community, these can provide an experimental platform for resolving the specificity versus generalizability of basic cancer biology principles (eg, credentialing of therapeutic molecular targets) and for validating translational approaches for prevention, diagnosis, and therapy. Thus, there is an urgent need to distribute the already established serially transplantable human prostate cancer xenografts and to develop robust methods for establishing new ones.

METHODS

To accelerate the development of such additional xenografts, particularly from patients treated with the newer standard of care agents (ie, abiraterone, enzalutamide, cabazitaxel, alpharadin, etc), a historic review of the field will be presented.

RESULTS

Over the last 50 years, multiple groups throughout the world have developed methods for the successful establishment of serially transplantable human prostate cancer xenografts using a variety of immune deficient mice. These are summarized chronologically.

CONCLUSIONS AND FUTURE

With the ever growing appreciation of the value of personalized medicine (aka precision medicine), methods need to be developed that allow efficient and timely growth of primary patient derived prostate cancer xenografts (PDXs), which can be used as "avatars" for defining optimal therapy for that specific patient. Such development should be based upon the leads obtained from the successful establishment of serially transplantable prostate cancer xenografts described in this review.

Rituximab Treatment Prevents Lymphoma Onset in Gastric Cancer Patient-Derived Xenografts

Patient-Derived Xenografts (PDXs), entailing implantation of cancer specimens in immunocompromised mice, are emerging as a valuable translational model that could help validate biologically relevant targets and assist the clinical development of novel therapeutic strategies for gastric cancer.

More than 30% of PDXs generated from gastric carcinoma samples developed human B-cell lymphomas instead of gastric cancer. These lymphomas were monoclonal, Epstein Barr Virus (EBV) positive, originated tumorigenic cell cultures and displayed a mutational burden and an expression profile distinct from gastric adenocarcinomas. The ability of grafted samples to develop lymphomas did not correlate with patient outcome, nor with the histotype, the lymphocyte infiltration level, or the EBV status of the original gastric tumor, impeding from foreseeing lymphoma onset. Interestingly, lymphoma development was significantly more frequent when primary rather than metastatic samples were grafted.

Notably, the development of such lympho-proliferative disease could be prevented by a short rituximab treatment upon mice implant, without negatively affecting gastric carcinoma engraftment.

Due to the high frequency of human lymphoma onset, our data show that a careful histologic analysis is mandatory when generating gastric cancer PDXs. Such care would avoid misleading results that could occur if testing of putative gastric cancer therapies is performed in lymphoma PDXs. We propose rituximab treatment of mice to prevent lymphoma development in PDX models, averting the loss of human-derived samples.

Using PDX for Preclinical Cancer Drug Discovery: The Evolving Field

The ability to create patient derived xenografts (PDXs) has evolved considerably from the breakthrough of the development of immune compromised mice. How researchers in drug discovery have utilized PDX of certain cancer types has also changed from traditionally selecting a few models to profile a drug, to opting to assess inter-tumor response heterogeneity by screening across a broad range of tumor models, and subsequently to enable clinical stratification strategies. As with all models and methodologies, imperfections with this approach are apparent, and our understanding of the fidelity of these models continues to expand. To date though, they are still viewed as one of the most faithful modeling systems in oncology. Currently, there are many efforts ongoing to increase the utility and translatability of PDXs, including introducing a human immune component to enable immunotherapy studies.

Alterations in the Rho pathway contribute to Epstein-Barr virus-induced lymphomagenesis in immunosuppressed environments

Epstein-Barr virus (EBV)-positive diffuse large B-cell lymphomas (EBV⁺-DLBLs) tend to occur in immunocompromised patients, such as the elderly or those undergoing solid organ transplantation. The pathogenesis and genomic characteristics of EBV⁺-DLBLs are largely unknown because of the limited availability of human samples and lack of experimental animal models. We observed the development of 25 human EBV⁺-DLBLs during the engraftment of gastric adenocarcinomas into immunodeficient mice. An integrated genomic analysis of the human-derived EBV⁺-DLBLs revealed enrichment of mutations in Rho pathway genes, including RHPN2, and Rho pathway transcriptomic activation. Targeting the Rho pathway using a Rho-associated protein kinase (ROCK) inhibitor, fasudil, markedly decreased tumor growth in EBV⁺-DLBL patient-derived xenograft (PDX) models. Thus, alterations in the Rho pathway appear to contribute to EBV-induced lymphomagenesis in immunosuppressed environments.

Evaluation of the risk of lymphomagenesis in xenografts by the PCR-based detection of EBV BamHI W region in patient cancer specimens

Establishment of patient-derived tumor xenografts (PDXs) is hampered by lymphomagenesis mostly caused by the latently-infected Epstein-Barr virus (EBV) contained in patient cancer tissues. However, the character of patient tissues that result in lymphomagenesis after xenotransplantation is not elucidated. In this study, we analyzed the patient colorectal cancer (CRC) tissues and the PDXs established by their xenotransplantation. We found that 2 of 9 (22%) PDX tumors were EBV-associated human diffuse large B cell lymphoma which was formed by clonal proliferation of human B-cell lymphocytes, were strongly positive for EBER-ISH, and were classified as type III latency. Expression of EBV genes and RNAs, such as EBNAs, LMP1, EBER and EBV-associated microRNAs in patient CRC tissues were unlikely to be associated with lymphomagenesis in PDXs. In contrast, the positive PCR-based amplification of BamHI W region, a major internal repeat in EBV genome, in the patient CRC tissues was correlated with lymphomagenesis in PDXs. These results suggest that the detection of the EBV BamHI W region in the patient surgical specimens will be an effective way to predict the risk of lymphomagenesis in PDXs before xenotransplantation.

Spontaneous development of Epstein-Barr Virus associated human lymphomas in a prostate cancer xenograft program

Prostate cancer research is hampered by the lack of in vivo preclinical models that accurately reflect patient tumour biology and the clinical heterogeneity of human prostate cancer. To overcome these limitations we propagated and characterised a new collection of patient-derived prostate cancer xenografts. Tumour fragments from 147 unsupervised, surgical prostate samples were implanted subcutaneously into immunodeficient Rag2^-/-γC^-/- mice within 24 hours of surgery. Histologic and molecular characterisation of xenografts was compared with patient characteristics, including androgen-deprivation therapy, and exome sequencing. Xenografts were established from 47 of 147 (32%) implanted primary prostate cancers. Only 14% passaged successfully resulting in 20 stable lines; derived from 20 independent patient samples. Surprisingly, only three of the 20 lines (15%) were confirmed as prostate cancer; one line comprised of mouse stroma, and 16 were verified as human donor-derived lymphoid neoplasms. PCR for Epstein-Barr Virus (EBV) nuclear antigen, together with exome sequencing revealed that the lymphomas were exclusively EBV-associated. Genomic analysis determined that 14 of the 16 EBV⁺ lines had unique monoclonal or oligoclonal immunoglobulin heavy chain gene rearrangements, confirming their B-cell origin. We conclude that the generation of xenografts from tumour fragments can commonly result in B-cell lymphoma from patients carrying latent EBV. We recommend routine screening, of primary outgrowths, for latent EBV to avoid this phenomenon.

Prevention of Human Lymphoproliferative Tumor Formation in Ovarian Cancer Patient-Derived Xenografts

Interest in preclinical drug development for ovarian cancer has stimulated development of patient-derived xenograft (PDX) or tumorgraft models. However, the unintended formation of human lymphoma in severe combined immunodeficiency (SCID) mice from Epstein-Barr virus (EBV)–infected human lymphocytes can be problematic. In this study, we have characterized ovarian cancer PDXs which developed human lymphomas and explore methods to suppress lymphoproliferative growth. Fresh human ovarian tumors from 568 patients were transplanted intraperitoneally in SCID mice. A subset of PDX models demonstrated atypical patterns of dissemination with mediastinal masses, hepatosplenomegaly, and CD45-positive lymphoblastic atypia without ovarian tumor engraftment. Expression of human CD20 but not CD3 supported a B-cell lineage, and EBV genomes were detected in all lymphoproliferative tumors. Immunophenotyping confirmed monoclonal gene rearrangements consistent with B-cell lymphoma, and global gene expression patterns correlated well with other human lymphomas. The ability of rituximab, an anti-CD20 antibody, to suppress human lymphoproliferation from a patient's ovarian tumor in SCID mice and prevent growth of an established lymphoma led to a practice change with a goal to reduce the incidence of lymphomas. A single dose of rituximab during the primary tumor heterotransplantation process reduced the incidence of CD45-positive cells in subsequent PDX lines from 86.3% (n = 117 without rituximab) to 5.6% (n = 160 with rituximab), and the lymphoma rate declined from 11.1% to 1.88%. Taken together, investigators utilizing PDX models for research should routinely monitor for lymphoproliferative tumors and consider implementing methods to suppress their growth.

Patient-derived xenografts of gastrointestinal cancers are susceptible to rapid and delayed B-lymphoproliferation

Patient-derived cancer xenografts (PDX) are widely used to identify and evaluate novel therapeutic targets, and to test therapeutic approaches in preclinical mouse avatar trials. Despite their widespread use, potential caveats of PDX models remain considerably underappreciated. Here, we demonstrate that EBV-associated B-lymphoproliferations frequently develop following xenotransplantation of human colorectal and pancreatic carcinomas in highly immunodeficient NOD.Cg-Prkdc^scid Il2rg^tm1Wjl /SzJ (NSG) mice (18/47 and 4/37 mice, respectively), and in derived cell cultures in vitro. Strikingly, even PDX with carcinoma histology can host scarce EBV-infected B-lymphocytes that can fully overgrow carcinoma cells during serial passaging in vitro and in vivo. As serial xenografting is crucial to expand primary tumor tissue for biobanks and cohorts for preclinical mouse avatar trials, the emerging dominance of B-lymphoproliferations in serial PDX represents a serious confounding factor in these models. Consequently, repeated phenotypic assessments of serial PDX are mandatory at each expansion step to verify "bona fide" carcinoma xenografts.

Patient-derived xenografts as in vivo models for research in urological malignancies

Lack of appropriate models that recapitulate the complexity and heterogeneity of urological tumours precludes most of the preclinical reagents that target urological tumours from receiving regulatory approval. Patient-derived xenograft (PDX) models are characterized by direct engraftment of patient-derived tumour fragments into immunocompromised mice. PDXs can maintain the original histology, as well as the molecular and genetic characteristics of the source tumour. Thus, PDX models have various advantages over conventional cell-line-derived xenograft (CDX) and other models, which has resulted in an increase in the use of urological tumour PDXs in the analysis of tumour biology and, importantly, for drug development and treatment decisions in personalized medicine. PDX models of urological malignancies have great potential to be used for both basic and clinical research, but limitations exist and need to be overcome. In particular, several agents targeting the immune system have shown promising results in kidney and bladder cancer; however, establishing PDX models in mice with an intact immune system so that an immune response against the tumour is triggered is important to investigate these new therapeutics. Moreover, international collaboration to share PDX models is essential for research concerning fatal urological tumours.

Patient-derived xenograft (PDX) models in basic and translational breast cancer research

Patient-derived xenograft (PDX) models of a growing spectrum of cancers are rapidly supplanting long-established traditional cell lines as preferred models for conducting basic and translational preclinical research. In breast cancer, to complement the now curated collection of approximately 45 long-established human breast cancer cell lines, a newly formed consortium of academic laboratories, currently from Europe, Australia, and North America, herein summarizes data on over 500 stably transplantable PDX models representing all three clinical subtypes of breast cancer (ER+, HER2+, and "Triple-negative" (TNBC)). Many of these models are well-characterized with respect to genomic, transcriptomic, and proteomic features, metastatic behavior, and treatment response to a variety of standard-of-care and experimental therapeutics. These stably transplantable PDX lines are generally available for dissemination to laboratories conducting translational research, and contact information for each collection is provided. This review summarizes current experiences related to PDX generation across participating groups, efforts to develop data standards for annotation and dissemination of patient clinical information that does not compromise patient privacy, efforts to develop complementary data standards for annotation of PDX characteristics and biology, and progress toward "credentialing" of PDX models as surrogates to represent individual patients for use in preclinical and co-clinical translational research. In addition, this review highlights important unresolved questions, as well as current limitations, that have hampered more efficient generation of PDX lines and more rapid adoption of PDX use in translational breast cancer research.

Culture and Drug Profiling of Patient Derived Malignant Pleural Effusions for Personalized Cancer Medicine

INTRODUCTION

The use of patients' own cancer cells for in vitro selection of the most promising treatment is an attractive concept in personalized medicine. Human carcinoma cells from malignant pleural effusions (MPEs) are suited for this purpose since they have already adapted to the liquid environment in the patient and do not depend on a stromal cell compartment. Aim of this study was to develop a systematic approach for the in-vitro culture of MPEs to analyze the effect of chemotherapeutic as well as targeted drugs.

METHODS

MPEs from patients with solid tumors were selected for this study. After morphological and molecular characterization, they were cultured in medium supplemented with patient-derived sterile-filtered effusion supernatant. Growth characteristics were monitored in real-time using the xCELLigence system. MPEs were treated with a targeted therapeutic (erlotinib) according to the mutational status or chemotherapeutics based on the recommendation of the oncologists.

RESULTS

We have established a robust system for the ex-vivo culture of MPEs and the application of drug tests in-vitro. The use of an antibody based magnetic cell separation system for epithelial cells before culture allowed treatment of effusions with only moderate tumor cell proportion. Experiments using drugs and drug-combinations revealed dose-dependent and specific growth inhibitory effects of targeted drugs.

CONCLUSIONS

We developed a new approach for the ex-vivo culture of MPEs and the application of drug tests in-vitro using real-time measuring of cell growth, which precisely reproduced the effect of clinically established treatments by standard chemotherapy and targeted drugs. This sets the stage for future studies testing agents against specific targets from genomic profiling of metastatic tumor cells and multiple drug-combinations in a personalized manner.

Establishment and characterisation of patient-derived xenografts as paraclinical models for gastric cancer

The patient-derived xenograft (PDX) model is emerging as a promising translational platform to duplicate the characteristics of tumours. However, few studies have reported detailed histological and genomic analyses for model fidelity and for factors affecting successful model establishment of gastric cancer. Here, we generated PDX tumours surgically-derived from 62 gastric cancer patients. Fifteen PDX models were successfully established (24.2%, 15/62) and passaged to maintain tumours in immune-compromised mice. Diffuse type and low tumour cell percentage were negatively correlated with success rates (p = 0.005 and p = 0.025, respectively), while reducing ex vivo and overall procedure times were positively correlated with success rates (p = 0.003 and p = 0.01, respectively). The histology and genetic characteristics of PDX tumour models were stable over subsequent passages. Lymphoma transformation occurred in five cases (33.3%, 5/15), and all were in the NOG mouse, with none in the nude mouse. Together, the present study identified Lauren classification, tumour cell percentages, and ex vivo times along with overall procedure times, as key determinants for successful PDX engraftment. Furthermore, genetic and histological characteristics were highly consistent between primary and PDX tumours, which provide realistic paraclinical models, enabling personalised development of treatment options for gastric cancer.

An Integrative Approach to Precision Cancer Medicine Using Patient-Derived Xenografts

Cancer is a heterogeneous disease caused by diverse genomic alterations in oncogenes and tumor suppressor genes. Despite recent advances in high-throughput sequencing technologies and development of targeted therapies, novel cancer drug development is limited due to the high attrition rate from clinical studies. Patient-derived xenografts (PDX), which are established by the transfer of patient tumors into immunodeficient mice, serve as a platform for co-clinical trials by enabling the integration of clinical data, genomic profiles, and drug responsiveness data to determine precisely targeted therapies. PDX models retain many of the key characteristics of patients' tumors including histology, genomic signature, cellular heterogeneity, and drug responsiveness. These models can also be applied to the development of biomarkers for drug responsiveness and personalized drug selection. This review summarizes our current knowledge of this field, including methodologic aspects, applications in drug development, challenges and limitations, and utilization for precision cancer medicine.

Establishment of primary patient-derived xenografts of palliative TURP specimens to study castrate-resistant prostate cancer

BACKGROUND

Fresh patient specimens of castrate-resistant prostate cancer (CRPC) are invaluable for studying tumor heterogeneity and responses to current treatments. They can be used for primary patient-derived xenografts (PDXs) or serially transplantable PDXs, but only a small proportion of samples grow successfully. To improve the efficiency and quality of PDXs, we investigated the factors that determine the initial engraftment of patient tissues derived from TURP specimens.

METHODS

Fresh tissue was collected from castrate patients who required a TURP for urinary symptoms. Tissue was grafted under the renal capsule of immune-compromised mice for up to 14 weeks. The abundance of cancer in ungrafted and grafted specimens was compared using histopathology. Mice were castrated or implanted with testosterone pellets to determine the androgen-responsiveness of CRPC PDXs from TURP tissue.

RESULTS

Primary PDXs were successfully established from 7 of 10 patients that underwent grafting. Of the 112 grafts generated from these 10 patients, 21% contained cancer at harvest. Grafts were most successful when the original patient specimens contained high amounts of viable cancer, defined as samples with (i) at least 50% cancer cells, (ii) no physical damage, and (iii) detectable Ki67 expression. PDX grafts survived in castrated hosts and proliferated in response to testosterone, confirming that they were castrate resistant but androgen-responsive.

CONCLUSIONS

Primary PDXs of CRPC can be established from TURP specimens with modest success. The take rate can be increased if the original tissues contain sufficient numbers of actively proliferating cancer cells. Selecting specimens with abundant viable cancer will maximize the rate of engraftment and increase the efficiency of establishing PDXs that can be serially transplanted.

Drug discovery in prostate cancer mouse models

INTRODUCTION

The mouse is an important, though imperfect, organism with which to model human disease and to discover and test novel drugs in a preclinical setting. Many experimental strategies have been used to discover new biological and molecular targets in the mouse, with the hopes of translating these discoveries into novel drugs to treat prostate cancer in humans. Modeling prostate cancer in the mouse, however, has been challenging, and often drugs that work in mice have failed in human trials.

AREAS COVERED

The authors discuss the similarities and differences between mice and men; the types of mouse models that exist to model prostate cancer; practical questions one must ask when using a mouse as a model; and potential reasons that drugs do not often translate to humans. They also discuss the current value in using mouse models for drug discovery to treat prostate cancer and what needs are still unmet in field.

EXPERT OPINION

With proper planning and following practical guidelines by the researcher, the mouse is a powerful experimental tool. The field lacks genetically engineered metastatic models, and xenograft models do not allow for the study of the immune system during the metastatic process. There remain several important limitations to discovering and testing novel drugs in mice for eventual human use, but these can often be overcome. Overall, mouse modeling is an essential part of prostate cancer research and drug discovery. Emerging technologies and better and ever-increasing forms of communication are moving the field in a hopeful direction.

Spontaneous Post-Transplant Disorders in NOD.Cg- Prkdcscid Il2rgtm1Sug/JicTac (NOG) Mice Engrafted with Patient-Derived Metastatic Melanomas

Patient-derived tumor xenograft (PDTX) approach is nowadays considered a reliable preclinical model to study in vivo cancer biology and therapeutic response. NOD scid and Il2rg-deficient mice represent the "gold standard" host for the generation of PDTXs. Compared to other immunocompromised murine lines, these mice offers several advantages including higher engraftment rate, longer lifespan and improved morphological and molecular preservation of patient-derived neoplasms. Here we describe a spectrum of previously uncharacterized post-transplant disorders affecting 14/116 (12%) NOD.Cg- Prkdcscid Il2rgtm1Sug/JicTac (NOG) mice subcutaneously engrafted with patient-derived metastatic melanomas. Affected mice exhibited extensive scaling/crusting dermatitis (13/14) associated with emaciation (13/14) and poor/unsuccessful tumor engraftment (14/14). In this context, the following pathological conditions have been recognized and characterized in details: (i) immunoinflammatory disorders with features of graft versus host disease (14/14); (ii) reactive lymphoid infiltrates effacing xenografted tumors (8/14); (iii) post-transplant B cell lymphomas associated with Epstein-Barr virus reactivation (2/14). We demonstrate that all these entities are driven by co-transplanted human immune cells populating patient-derived tumor samples. Since the exploding interest in the utilization of NOD scid and Il2rg-deficient mice for the establishment of PDTX platforms, it is of uppermost importance to raise the awareness of the limitations associated with this model. The disorders here described adversely impact tumor engraftment rate and animal lifespan, potentially representing a major confounding factor in the context of efficacy and personalized therapy studies. The occurrence of these conditions in the NOG model reflects the ability of this mouse line to promote efficient engraftment of human immune cells. Co-transplanted human lymphoid cells have indeed the potential to colonize the recipient mouse initiating the post-transplant conditions here reported. On the other hand, the evidence of an immune response of human origin against the xenotransplanted melanoma opens intriguing perspectives for the establishment of suitable preclinical models of anti-melanoma immunotherapy.