Recent technological advances in using mouse models to study ovarian cancer

Preclinical tumor mouse models for studying esophageal cancer

Preclinical models are extensively employed in cancer research because they can be manipulated in terms of their environment, genome, molecular biology, organ systems, and physical activity to mimic human behavior and conditions. The progress made in in vivo cancer research has resulted in significant advancements, enabling the creation of spontaneous, metastatic, and humanized mouse models. Most recently, the remarkable and extensive developments in genetic engineering, particularly the utilization of CRISPR/Cas9, transposable elements, epigenome modifications, and liquid biopsies, have further facilitated the design and development of numerous mouse models for studying cancer. In this review, we have elucidated the production and usage of current mouse models, such as xenografts, chemical-induced models, and genetically engineered mouse models (GEMMs), for studying esophageal cancer. Additionally, we have briefly discussed various gene-editing tools that could potentially be employed in the future to create mouse models specifically for esophageal cancer research.

Aberrant MAPK Signaling Offers Therapeutic Potential for Treatment of Ovarian Carcinoma

Ovarian cancer remains the most lethal gynecological malignancy worldwide due to lack of effective screening, vague early symptoms, poor description of biomarkers, and absence of effective treatment regimes. Epithelial ovarian carcinoma (EOC) is categorized into five distinct disease subtypes which collectively account for ~90% of ovarian carcinomas. Most women present at advanced stages contributing to a poor overall 5-year survival rate. Standard treatment for EOC is cytoreductive surgery and platinum-based chemotherapy; however, most patients suffer from recurrence and platinum-resistant disease, which highlights an urgent need for targeted therapy. The high frequency of molecular alterations affecting gain-of-function signaling through the RAS mitogen-activated protein kinase (MAPK) pathway in EOC has prompted pre-clinical and clinical efforts toward research into the effectiveness of MAPK pathway inhibition as a second-line treatment. The RAS/MAPK pathway is a highly conserved signal transduction cascade, often disrupted in cancer, that regulates tumorigenic phenotypes including cellular proliferation, survival, migration, apoptosis, and differentiation. Herein, the role of the MAPK pathway in EOC with emphasis on targetability of the pathway is described. Pre-clinical and clinical efforts to target MAPK signaling in EOC have identified several MAPK pathway inhibitors that offer efficacious potential for monotherapy and in combination with other compounds. Thus, inhibition of the RAS/MAPK pathway is emerging as a tractable strategy for treatment of ovarian cancer that may permit development of personalized therapy and improved prognosis for women challenged by this disease.

The Proteolytic Landscape of Ovarian Cancer: Applications in Nanomedicine

Ovarian cancer (OvCa) is one of the leading causes of mortality globally with an overall 5-year survival of 47%. The predominant subtype of OvCa is epithelial carcinoma, which can be highly aggressive. This review launches with a summary of the clinical features of OvCa, including staging and current techniques for diagnosis and therapy. Further, the important role of proteases in OvCa progression and dissemination is described. Proteases contribute to tumor angiogenesis, remodeling of extracellular matrix, migration and invasion, major processes in OvCa pathology. Multiple proteases, such as metalloproteinases, trypsin, cathepsin and others, are overexpressed in the tumor tissue. Presence of these catabolic enzymes in OvCa tissue can be exploited for improving early diagnosis and therapeutic options in advanced cases. Nanomedicine, being on the interface of molecular and cellular scales, can be designed to be activated by proteases in the OvCa microenvironment. Various types of protease-enabled nanomedicines are described and the studies that focus on their diagnostic, therapeutic and theranostic potential are reviewed.

Establishment of In Vivo Ovarian Cancer Mouse Models Using Intraperitoneal Tumor Cell Injection

Mouse models-xenograft models, syngeneic models (directly implanted or chemically or virally induced), and genetically engineered mice (including transgenic and knockout methods) are invaluable for preclinical studies of ovarian cancer as they recapitulate the structures and microenvironments of tumors, which in vitro studies are unable to accomplish.This chapter describes the methodology and approaches for generating various murine models currently employed in ovarian cancer research. It covers the implantation of cells from ovarian cancer cell lines into mice by intraperitoneal injection.

Bioengineering of virus-like particles as dynamic nanocarriers for in vivo delivery and targeting to solid tumours

Virus-like particles (VLPs) are known as self-assembled, non-replicative and non-infectious protein particles, which imitate the formation and structure of original wild type viruses, however, lack the viral genome and/or their fragments. The capacity of VLPs to encompass small molecules like nucleic acids and others has made them as novel vessels of nanocarriers for drug delivery applications. In addition, VLPs surface have the capacity to achieve variation of the surface display via several modification strategies including genetic modification, chemical modification, and non-covalent modification. Among the VLPs nanocarriers, Hepatitis B virus core (HBc) particles have been the most encouraging candidate. HBc particles are hollow nanoparticles in the range of 30-34 nm in diameter and 7 nm thick envelopes, consisting of 180 or 240 copies of identical polypeptide monomer. They also employ a distinctive position among the VLPs carriers due to the high-level synthesis, which serves as a strong protective capsid shell and efficient self-assembly properties. This review highlights on the bioengineering of HBc particles as dynamic nanocarriers for in vivo delivery and specific targeting to solid tumours.

Modeling the Tumor Microenvironment of Ovarian Cancer: The Application of Self-Assembling Biomaterials

Ovarian cancer (OvCa) is one of the leading causes of gynecologic malignancies. Despite treatment with surgery and chemotherapy, OvCa disseminates and recurs frequently, reducing the survival rate for patients. There is an urgent need to develop more effective treatment options for women diagnosed with OvCa. The tumor microenvironment (TME) is a key driver of disease progression, metastasis and resistance to treatment. For this reason, 3D models have been designed to represent this specific niche and allow more realistic cell behaviors compared to conventional 2D approaches. In particular, self-assembling peptides represent a promising biomaterial platform to study tumor biology. They form nanofiber networks that resemble the architecture of the extracellular matrix and can be designed to display mechanical properties and biochemical motifs representative of the TME. In this review, we highlight the properties and benefits of emerging 3D platforms used to model the ovarian TME. We also outline the challenges associated with using these 3D systems and provide suggestions for future studies and developments. We conclude that our understanding of OvCa and advances in materials science will progress the engineering of novel 3D approaches, which will enable the development of more effective therapies.

Contemporary Mouse Models in Glioma Research

Despite advances in understanding of the molecular pathogenesis of glioma, outcomes remain dismal. Developing successful treatments for glioma requires faithful in vivo disease modeling and rigorous preclinical testing. Murine models, including xenograft, syngeneic, and genetically engineered models, are used to study glioma-genesis, identify methods of tumor progression, and test novel treatment strategies. Since the discovery of highly recurrent isocitrate dehydrogenase (IDH) mutations in lower-grade gliomas, there is increasing emphasis on effective modeling of IDH mutant brain tumors. Improvements in preclinical models that capture the phenotypic and molecular heterogeneity of gliomas are critical for the development of effective new therapies. Herein, we explore the current status, advancements, and challenges with contemporary murine glioma models.

Mouse models of epithelial ovarian cancer for preclinical studies

Epithelial ovarian cancer (EOC) is the leading cause of gynecological cancer-related mortality in the developed world. EOC is a heterogeneous disease represented by several histological and molecular subtypes. Therefore, exploration of relevant preclinical animal models that consider the heterogenic nature of EOC is of great importance for the development of novel therapeutic strategies that can be translated clinically to combat this devastating disease. In this review, we discuss recent progress in the development of preclinical mouse models for EOC study as well as their advantages and limitations.

The hallmarks of ovarian cancer: proliferation and cell growth

Epithelial ovarian cancer (EOC) is a heterogeneous group of diseases with distinct biological and clinical behaviour. Despite the differences between them, the capability of tumour cells to continuously proliferate and avoid death is maintained among histotypes. This ability is the result of alterations at different levels, causing the deregulation of cell cycle and proliferative-related pathways. Even if the leading role is played by RB and TP53, changes in other molecular pathways are involved in the development of EOC. This ability can be exploited to generate in vitro and in vivo models resembling the conditions of tumour development in a patient. In vivo models, such as patient-derived xenografts (PDX) or genetically engineered mouse models (GEMM), represent a fundamental tool in the study of the molecular mechanisms implicated in each EOC biotype for testing new therapeutic approaches. Herein we describe the major proliferation-related pathways and its disruption found in EOC and how these features can be used to establish in vivo models for translational research.

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Epithelial ovarian cancer (EOC) molecular biotypes are defined by distinct biology and clinical behaviour.

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Sustained proliferation and resistance to cell death mechanisms characterised tumour cells.

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RB and TP53 tumour-suppressor genes are highly implicated in EOC pathogenesis.

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In vitro and in vivo models have a key role in the study of molecular mechanisms involved in EOC pathogenesis.

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Development of animal models that mimic disease features constitute essential tools for new drugs testing.

Spontaneous and Induced Animal Models for Cancer Research

Considering the complexity of the current framework in oncology, the relevance of animal models in biomedical research is critical in light of the capacity to produce valuable data with clinical translation. The laboratory mouse is the most common animal model used in cancer research due to its high adaptation to different environments, genetic variability, and physiological similarities with humans. Beginning with spontaneous mutations arising in mice colonies that allow for pursuing studies of specific pathological conditions, this area of in vivo research has significantly evolved, now capable of generating humanized mice models encompassing the human immune system in biological correlation with human tumor xenografts. Moreover, the era of genetic engineering, especially of the hijacking CRISPR/Cas9 technique, offers powerful tools in designing and developing various mouse strains. Within this article, we will cover the principal mouse models used in oncology research, beginning with behavioral science of animals vs. humans, and continuing on with genetically engineered mice, microsurgical-induced cancer models, and avatar mouse models for personalized cancer therapy. Moreover, the area of spontaneous large animal models for cancer research will be briefly presented.

A dog oviduct-on-a-chip model of serous tubal intraepithelial carcinoma

Ovarian cancer is the fifth cause of cancer-related mortality in women, with an expected 5-year survival rate of only 47%. High-grade serous carcinoma (HGSC), an epithelial cancer phenotype, is the most common malignant ovarian cancer. It is known that the precursors of HGSC originate from secretory epithelial cells within the Fallopian tube, which first develops as serous tubal intraepithelial carcinoma (STIC). Here, we used gene editing by CRISPR-Cas9 to knock out the oncogene p53 in dog oviductal epithelia cultured in a dynamic microfluidic chip to create an in vitro model that recapitulated human STIC. Similar to human STIC, the gene-edited oviduct-on-a-chip, exhibited loss of cell polarization and had reduced ciliation, increased cell atypia and proliferation, with multilayered epithelium, increased Ki67, PAX8 and Myc and decreased PTEN and RB1 mRNA expression. This study provides a biomimetic in vitro model to study STIC progression and to identify potential biomarkers for early detection of HGSC.

Development of a MEL Cell-Derived Allograft Mouse Model for Cancer Research

Murine erythroleukemia (MEL) cells are often employed as a model to dissect mechanisms of erythropoiesis and erythroleukemia in vitro. Here, an allograft model using MEL cells resulting in splenomegaly was established to develop a diagnostic model for isolation/quantification of metastatic cells, anti-cancer drug screening, and evaluation of the tumorigenic or metastatic potentials of molecules in vivo. In this animal model, circulating MEL cells from the blood stream were successfully isolated and quantified with an additional in vitro cultivation step. In terms of the molecular-pathological analysis, we were able to successfully evaluate the functional discrimination between methyl-CpG-binding domain 2 (Mbd2) and p66α in erythroid differentiation, and tumorigenic potential in spleen and blood stream of allograft model mice. In addition, we found that the number of circulating MEL cells in anti-cancer drug-treated mice was dose-dependently decreased. Our data demonstrate that the newly established allograft model is useful to dissect erythroleukemia pathologies and non-invasively provides valuable means for isolation of metastatic cells, screening of anti-cancer drugs, and evaluation of the tumorigenic potentials.

Characteristics of in Vivo Model Systems for Ovarian Cancer Studies

An understanding of the molecular pathogenesis and heterogeneity of ovarian cancer holds promise for the development of early detection strategies and novel, efficient therapies. In this review, we discuss the advantages and limitations of animal models available for basic and preclinical studies. The fruit fly model is suitable mainly for basic research on cellular migration, invasiveness, adhesion, and the epithelial-to-mesenchymal transition. Higher-animal models allow to recapitulate the architecture and microenvironment of the tumor. We discuss a syngeneic mice model and the patient derived xenograft model (PDX), both useful for preclinical studies. Conditional knock-in and knock-out methodology allows to manipulate selected genes at a given time and in a certain tissue. Such models have built our knowledge about tumor-initiating genetic events and cell-of-origin of ovarian cancers; it has been shown that high-grade serous ovarian cancer may be initiated in both the ovarian surface and tubal epithelium. It is postulated that clawed frog models could be developed, enabling studies on tumor immunity and anticancer immune response. In laying hen, ovarian cancer develops spontaneously, which provides the opportunity to study the genetic, biochemical, and environmental risk factors, as well as tumor initiation, progression, and histological origin; this model can also be used for drug testing. The chick embryo chorioallantoic membrane is another attractive model and allows the study of drug response.

Optoacoustic imaging identifies ovarian cancer using a microenvironment targeted theranostic wormhole mesoporous silica nanoparticle

At the intersection of the newly emerging fields of optoacoustic imaging and theranostic nanomedicine, promising clinical progress can be made in dismal prognosis of ovarian cancer. An acidic pH targeted wormhole mesoporous silica nanoparticle (V7-RUBY) was developed to serve as a novel tumor specific theranostic nanoparticle detectable using multispectral optoacoustic tomographic (MSOT) imaging. We report the synthesis of a small, < 40 nm, biocompatible asymmetric wormhole pore mesoporous silica core particle that has both large loading capacity and favorable release kinetics combined with tumor-specific targeting and gatekeeping. V7-RUBY exploits the acidic tumor microenvironment for tumor-specific targeting and tumor-specific release. In vitro, treatment with V7-RUBY containing either paclitaxel or carboplatin resulted in increased cell death at pH 6.6 in comparison to drug alone (p < 0.0001). In orthotopic ovarian xenograft mouse models, V7-RUBY containing IR780 was specifically detected within the tumor 7X and 4X higher than the liver and >10X higher than in the kidney using both multispectral optoacoustic tomography (MSOT) imaging with secondary confirmation using near infrared fluorescence imaging (p < 0.0004). The V7-RUBY system carrying a cargo of either contrast agent or an anti-neoplastic drug has the potential to become a theranostic nanoparticle which can improve both diagnosis and treatment of ovarian cancer.

Transgenic Mouse Models in Cancer Research

The use of existing mouse models in cancer research is of utmost importance as they aim to explore the casual link between candidate cancer genes and carcinogenesis as well as to provide models to develop and test new therapies. However, faster progress in translating mouse cancer model research into the clinic has been hampered due to the limitations of these models to better reflect the complexities of human tumors. Traditionally, immunocompetent and immunodeficient mice with syngeneic and xenografted tumors transplanted subcutaneously or orthotopically have been used. These models are still being widely employed for many different types of studies, in part due to their widespread availability and low cost. Other types of mouse models used in cancer research comprise transgenic mice in which oncogenes can be constitutively or conditionally expressed and tumor-suppressor genes silenced using conventional methods, such as retroviral infection, microinjection of DNA constructs, and the so-called "gene-targeted transgene" approach. These traditional transgenic models have been very important in studies of carcinogenesis and tumor pathogenesis, as well as in studies evaluating the development of resistance to therapy. Recently, the clustered regularly interspaced short palindromic repeats (CRISPR)-based genome editing approach has revolutionized the field of mouse cancer models and has had a profound and rapid impact on the development of more effective systems to study human cancers. The CRISPR/Cas9-based transgenic models have the capacity to engineer a wide spectrum of mutations found in human cancers and provide solutions to problems that were previously unsolvable. Recently, humanized mouse xenograft models that accept patient-derived xenografts and CD34+ cells were developed to better mimic tumor heterogeneity, the tumor microenvironment, and cross-talk between the tumor and stromal/immune cells. These features make them extremely valuable models for the evaluation of investigational cancer therapies, specifically new immunotherapies. Taken together, improvements in both the CRISPR/Cas9 system producing more valid mouse models and in the humanized mouse xenograft models resembling complex interactions between the tumor and its environment might represent one of the successful pathways to precise individualized cancer therapy, leading to improved cancer patient survival and quality of life.

In silico cancer research towards 3R

BACKGROUND

Improving our understanding of cancer and other complex diseases requires integrating diverse data sets and algorithms. Intertwining in vivo and in vitro data and in silico models are paramount to overcome intrinsic difficulties given by data complexity. Importantly, this approach also helps to uncover underlying molecular mechanisms. Over the years, research has introduced multiple biochemical and computational methods to study the disease, many of which require animal experiments. However, modeling systems and the comparison of cellular processes in both eukaryotes and prokaryotes help to understand specific aspects of uncontrolled cell growth, eventually leading to improved planning of future experiments. According to the principles for humane techniques milestones in alternative animal testing involve in vitro methods such as cell-based models and microfluidic chips, as well as clinical tests of microdosing and imaging. Up-to-date, the range of alternative methods has expanded towards computational approaches, based on the use of information from past in vitro and in vivo experiments. In fact, in silico techniques are often underrated but can be vital to understanding fundamental processes in cancer. They can rival accuracy of biological assays, and they can provide essential focus and direction to reduce experimental cost.

MAIN BODY

We give an overview on in vivo, in vitro and in silico methods used in cancer research. Common models as cell-lines, xenografts, or genetically modified rodents reflect relevant pathological processes to a different degree, but can not replicate the full spectrum of human disease. There is an increasing importance of computational biology, advancing from the task of assisting biological analysis with network biology approaches as the basis for understanding a cell's functional organization up to model building for predictive systems.

CONCLUSION

Underlining and extending the in silico approach with respect to the 3Rs for replacement, reduction and refinement will lead cancer research towards efficient and effective precision medicine. Therefore, we suggest refined translational models and testing methods based on integrative analyses and the incorporation of computational biology within cancer research.

Optical and Magnetic Resonance Imaging Using Fluorous Colloidal Nanoparticles

Improved imaging of cancerous tissue has the potential to aid prognosis and improve patient outcome through longitudinal imaging of treatment response and disease progression. While nuclear imaging has made headway in cancer imaging, fluorinated tracers that enable magnetic resonance imaging (¹⁹F MRI) hold promise, particularly for repeated imaging sessions because nonionizing radiation is used. Fluorine MRI detects molecular signatures by imaging a fluorinated tracer and takes advantage of the spatial and anatomical resolution afforded by MRI. This manuscript describes a fluorous polymeric nanoparticle that is capable of ¹⁹F MR imaging and fluorescent tracking for in vitro and in vivo monitoring of immune cells and cancerous tissue. The fluorous particle is derived from low-molecular-weight amphiphilic copolymers that self-assemble into micelles with a hydrodynamic diameter of 260 nm. The polymer is MR-active at concentrations as low as 2.1 mM in phantom imaging studies. The fluorinated particle demonstrated rapid uptake into immune cells for potential cell-tracking or delineation of the tumor microenvironment and showed negligible toxicity. Systemic administration indicates significant uptake into two tumor types, triple-negative breast cancer and ovarian cancer, with little accumulation in off-target tissue. These results indicate a robust platform imaging agent capable of immune cell tracking and systemic disease monitoring with exceptional uptake of the nanoparticle in multiple cancer models.

Engineering hepatitis B virus core particles for targeting HER2 receptors in vitro and in vivo

Hepatitis B Virus core (HBc) particles have been studied for their potential as drug delivery vehicles for cancer therapy. HBc particles are hollow nano-particles of 30–34 nm diameter and 7 nm thick envelopes, consisting of 180–240 units of 21 kDa core monomers. They have the capacity to assemble/dis-assemble in a controlled manner allowing encapsulation of various drugs and other biomolecules. Moreover, other functional motifs, i.e. receptors, receptor binding sequences, peptides and proteins can be expressed. This study focuses on the development of genetically modified HBc particles to specifically recognise and target human epidermal growth factor receptor-2 (HER2)-expressing cancer cells, in vitro and in vivo, for future cancer therapy. The non-specific binding capacity of wild type HBc particles was reduced by genetic deletion of the sequence encoding arginine-rich domains. A specific HER2-targeting was achieved by expressing the Z_HER2 affibodies on the HBc particles surface. In vitro studies showed specific uptake of Z_HER2-ΔHBc particles in HER2 expressing cancer cells. In vivo studies confirmed positive uptake of Z_HER2-ΔHBc particles in HER2-expressing tumours, compared to non-targeted ΔHBc particles in intraperitoneal tumour-bearing mice models. The present results highlight the potential of these nanocarriers in targeting HER2-positive metastatic abdominal cancer following intra-peritoneal administration.

An Advanced Orthotopic Ovarian Cancer Model in Mice for Therapeutic Trials

A nude mouse received subcutaneous injection of human ovarian cancer cells HO-8910PM to form a tumor, and then the tumor fragment was surgically transplanted to the ovary of a recipient mouse to establish an orthotopic cancer model. Tumors occurred in 100% of animals. A mouse displayed an ovarian mass, ascites, intraperitoneal spread, and lung metastasis at natural death. The mean survival time was 34.1 ± 17.2 days, with median survival time of 28.5 days. The findings indicated that the present mouse model can reflect the biological behavior of advanced human ovarian cancers. This in vivo model can be used to explore therapeutic means against chemoresistance and metastasis, and an effective treatment would prolong the survival time.

Orthotopic Model of Ovarian Cancer

Epithelial ovarian cancer (EOC) is the fifth commonest cancer-related cause of female death in the developed world. In spite of current surgical and chemotherapeutic options the vast majority of patients have widely metastatic disease and the survival rate has not much changed over the last years. The anti-angiogenic drugs are driving the field of agents targeting the tumor microenvironment in ovarian cancer. Preclinical models that accurately reproduce the molecular and biological features of ovarian cancer patients are a valuable means of producing reliable data on personalized medicine and predicting the therapeutic response in clinical trials.In this methodological chapter we describe the orthotopic model of ovarian cancer implanted under the ovarian bursa of mice. In spite of anatomical differences between the rodent and human bursa-fallopian tube, the appropriate primary tumor microenvironment at the site of the implant allows investigation of tumor-stroma interactions (e.g., angiogenesis), and is well suited for studying the tumor dissemination and metastasis typical of this disease.This model-although fairly labor intensive-may be useful for assessing novel, more selective therapeutic interventions and for biomarker discovery, reflecting the behavior of this disease.

Studying platinum sensitivity and resistance in high-grade serous ovarian cancer: Different models for different questions

High-grade serous ovarian cancer (HGSOC) has the highest mortality rate among all gynecological cancers. Patients are generally diagnosed in an advanced stage with the majority of cases displaying platinum resistant relapses. Recent genomic interrogation of large numbers of HGSOC patient samples indicated high complexity in terms of genetic aberrations, intra- and intertumor heterogeneity and underscored their lack of targetable oncogenic mutations. Sub-classifications of HGSOC based on expression profiles, termed 'differentiated', 'immunoreactive', 'mesenchymal' and 'proliferative', were shown to have prognostic value. In addition, in almost half of all HGSOC patients, a deficiency in homologous recombination (HR) was found that potentially can be targeted using PARP inhibitors. Developing precision medicine requires advanced experimental models. In the current review, we discuss experimental HGSOC models in which resistance to platinum therapy and the use of novel therapeutics can be carefully studied. Panels of better-defined primary cell lines need to be established to capture the full spectrum of HGSOC subtypes. Further refinement of cell lines is obtained with a 3-dimensional culture model mimicking the tumor microenvironment. Alternatively, ex vivo ovarian tumor tissue slices are used. For in vivo studies, larger panels of ovarian cancer patient-derived xenografts (PDXs) are being established, encompassing all expression subtypes. Ovarian cancer PDXs grossly retain tumor heterogeneity and clinical response to platinum therapy is preserved. PDXs are currently used in drug screens and as avatars for patient response. The role of the immune system in tumor responses can be assessed using humanized PDXs and immunocompetent genetically engineered mouse models. Dynamic tracking of genetic alterations in PDXs as well as patients during treatment and after relapse is feasible by sequencing circulating cell-free tumor DNA and analyzing circulating tumor cells. We discuss how various models and methods can be combined to delineate the molecular mechanisms underlying platinum resistance and to select HGSOC patients other than BRCA1/2-mutation carriers that could potentially benefit from the synthetic lethality of PARP inhibitors. This integrated approach is a first step to improve therapy outcomes in specific subgroups of HGSOC patients.

Advantages of the avian model for human ovarian cancer

Ovarian cancer (OC) is the most lethal gynecological cancer. Early detection of OC is crucial for providing efficient treatment, whereas high mortality rates correlate with late detection of OC, when the tumor has already metastasized to other organs. The most prevalent type of OC is epithelial OC (EOC). Models that have been used to study EOC include the fruit fly, mouse and laying hen, in addition to human EOC cells in 3D culture in vitro. These models have helped in the elucidation of the genetic component of this disease and the development of drug therapies. However, the histological origin of EOC and early markers of the disease remain largely unknown. In this study, we aimed to review the relative value of each of the different models in EOC and their contributions to understanding this disease. It was concluded that the spontaneous occurrence of EOC in the adult hen, the prolific ovulation, the similarity of metastatic progression with that in humans and the advantages of using the chicken embryo for modelling the development of the reproductive system, renders the hen particularly suitable for studying the early development of EOC. Further investigation of this avian model may contribute to a better understanding of EOC, improve clinical insight and ultimately contribute to decreasing its mortality rates among humans.

The promise and challenge of ovarian cancer models

The complexity and heterogeneity of ovarian cancer cases are difficult to reproduce in in vitro studies, which cannot adequately elucidate the molecular events involved in tumor initiation and disease metastasis. It has now become clear that, although the multiple histological subtypes of ovarian cancer are being treated with similar surgical and therapeutic approaches, they are in fact characterized by distinct phenotypes, cell of origin, and underlying key genetic and genomic alterations. Consequently, the development of more personalized treatment methodologies, which are aimed at improving patient care and prognosis, will greatly benefit from a better understanding of the key differences between various subtypes. To accomplish this, animal models of all histotypes need to be generated in order to provide accurate in vivo platforms for research and the testing of targeted treatments and immune therapies. Both genetically engineered mouse models (GEMMs) and xenograft models have the ability to further our understanding of key mechanisms facilitating tumorigenesis, and at the same time offer insight into enhanced imaging and treatment modalities. While genetic models may be better suited to examine oncogenic functions and interactions during tumorigenesis, patient-derived xenografts (PDXs) are likely a superior model to assess drug efficacy, especially in concurrent clinical trials, due to their similarity to the tumors from which they are derived. Genetic and avatar models possess great clinical utility and have both benefits and limitations. Additionally, the laying hen model, which spontaneously develops ovarian tumors, has inherent advantages for the study of epithelial ovarian cancer (EOC) and recent work champions this model especially when assessing chemoprevention strategies. While high-grade ovarian serous tumors are the most prevalent form of EOC, rarer ovarian cancer variants, such as small cell ovarian carcinoma of the hypercalcemic type and transitional cell carcinoma, or non-epithelial tumors, including germ cell tumors, will also benefit from the generation of improved models to advance our understanding of tumorigenic mechanisms and the development of selective therapeutic options.

Folate receptor-targeted multimodality imaging of ovarian cancer in a novel syngeneic mouse model

A new transplantable ovarian tumor model is presented using a novel folate receptor (FR) positive, murine ovarian cancer cell line that emulates the human disease and induces widespread intraperitoneal (i.p.) tumors in immunocompetent mice within 4–8 weeks of implantation. Tumor development was monitored using a new positron emission tomography (PET) FR-targeting reporter with PET/computerized tomography (PET/CT) and fluorescence molecular tomography (FMT) using a commercial FR-targeting reporter. Conventional structural magnetic resonance imaging (MRI) was also performed. Adult female C57BL/6 mice were injected i.p. with 6 × 10⁶ MKP-L FR+ cells. Imaging was performed weekly beginning 2 weeks after tumor induction. The albumin-binding, FR-targeting ligand cm09 was radiolabeled with the positron emitter ⁶⁸Ga and used to image the tumors with a small animal PET/CT. The FR-reporter FolateRSense 680 (PerkinElmer) was used for FMT and flow cytometry. Preclinical MRI (7 T) without FR-targeting was compared with the PET and FMT molecular imaging. Tumors were visible by all three imaging modalities. PET/CT had the highest imaging sensitivity at 3–3.5 h postadministration (mean %IA/g mean > 6) and visualized tumors earlier than the other two modalities with lower kidney uptake (mean %IA/g mean < 17) than previously reported FR-targeting agents in late stage disease. FMT showed relatively low FR-targeted agent in the bladder and kidneys, but yielded the lowest anatomical image resolution. MRI produced the highest resolution images, but it was difficult to distinguish tumors from abdominal organs during early progression since a FR-targeting MRI reporter was not used. Nevertheless, there was good correlation of imaging biomarkers between the three modalities. Tumors in the mouse ovarian cancer model could be detected using FR-targeted imaging as early as 2 weeks post i.p. injection of tumor cells. An imaging protocol should combine one or more of the modalities, e.g., PET/CT or PET/MRI for optimal tumor detection and delineation from surrounding tissues.

Murine model for non-invasive imaging to detect and monitor ovarian cancer recurrence

Epithelial ovarian cancer is the most lethal gynecologic malignancy in the United States. Although patients initially respond to the current standard of care consisting of surgical debulking and combination chemotherapy consisting of platinum and taxane compounds, almost 90% of patients recur within a few years. In these patients the development of chemoresistant disease limits the efficacy of currently available chemotherapy agents and therefore contributes to the high mortality. To discover novel therapy options that can target recurrent disease, appropriate animal models that closely mimic the clinical profile of patients with recurrent ovarian cancer are required. The challenge in monitoring intra-peritoneal (i.p.) disease limits the use of i.p. models and thus most xenografts are established subcutaneously. We have developed a sensitive optical imaging platform that allows the detection and anatomical location of i.p. tumor mass. The platform includes the use of optical reporters that extend from the visible light range to near infrared, which in combination with 2-dimensional X-ray co-registration can provide anatomical location of molecular signals. Detection is significantly improved by the use of a rotation system that drives the animal to multiple angular positions for 360 degree imaging, allowing the identification of tumors that are not visible in single orientation. This platform provides a unique model to non-invasively monitor tumor growth and evaluate the efficacy of new therapies for the prevention or treatment of recurrent ovarian cancer.