Zebrafish models for cancer

Emerging In Vitro and In Vivo Models: Hope for the Better Understanding of Cancer Progression and Treatment

Various cancer models have been developed to aid the understanding of the underlying mechanisms of tumor development and evaluate the effectiveness of various anticancer drugs in preclinical studies. These models accurately reproduce the critical stages of tumor initiation and development to mimic the tumor microenvironment better. Using these models for target validation, tumor response evaluation, resistance modeling, and toxicity comprehension can significantly enhance the drug development process. Herein, various in vivo or animal models are presented, typically consisting of several mice and in vitro models ranging in complexity from transwell models to spheroids and CRISPR-Cas9 technologies. While in vitro models have been used for decades and dominate the early stages of drug development, they are still limited primary to simplistic tests based on testing on a single cell type cultivated in Petri dishes. Recent advancements in developing new cancer therapies necessitate the generation of complicated animal models that accurately mimic the tumor's complexity and microenvironment. Mice make effective tumor models as they are affordable, have a short reproductive cycle, exhibit rapid tumor growth, and are simple to manipulate genetically. Human cancer mouse models are crucial to understanding the neoplastic process and basic and clinical research improvements. The following review summarizes different in vitro and in vivo metastasis models, their advantages and disadvantages, and their ability to serve as a model for cancer research.

Zebrafish live imaging: a strong weapon in anticancer drug discovery and development

Developing anticancer drugs is a complex and time-consuming process. The inability of current laboratory models to reflect important aspects of the tumor in vivo limits anticancer medication research. Zebrafish is a rapid, semi-automated in vivo screening platform that enables the use of non-invasive imaging methods to monitor morphology, survival, developmental status, response to drugs, locomotion, or other behaviors. Zebrafish models are widely used in drug discovery and development for anticancer drugs, especially in conjunction with live imaging techniques. Herein, we concentrated on the use of zebrafish live imaging in anticancer therapeutic research, including drug screening, efficacy assessment, toxicity assessment, and mechanism studies. Zebrafish live imaging techniques have been used in numerous studies, but this is the first time that these techniques have been comprehensively summarized and compared side by side. Finally, we discuss the hypothesis of Zebrafish Composite Model, which may provide future directions for zebrafish imaging in the field of cancer research.

Mechanobiology of cancer cell responsiveness to chemotherapy and immunotherapy: Mechanistic insights and biomaterial platforms

Mechanical forces are central to how cancer treatments such as chemotherapeutics and immunotherapies interact with cells and tissues. At the simplest level, electrostatic forces underlie the binding events that are critical to therapeutic function. However, a growing body of literature points to mechanical factors that also affect whether a drug or an immune cell can reach a target, and to interactions between a cell and its environment affecting therapeutic efficacy. These factors affect cell processes ranging from cytoskeletal and extracellular matrix remodeling to transduction of signals by the nucleus to metastasis of cells. This review presents and critiques the state of the art of our understanding of how mechanobiology impacts drug and immunotherapy resistance and responsiveness, and of the in vitro systems that have been of value in the discovery of these effects.

Bioelectricity in Developmental Patterning and Size Control: Evidence and Genetically Encoded Tools in the Zebrafish Model

Developmental patterning is essential for regulating cellular events such as axial patterning, segmentation, tissue formation, and organ size determination during embryogenesis. Understanding the patterning mechanisms remains a central challenge and fundamental interest in developmental biology. Ion-channel-regulated bioelectric signals have emerged as a player of the patterning mechanism, which may interact with morphogens. Evidence from multiple model organisms reveals the roles of bioelectricity in embryonic development, regeneration, and cancers. The Zebrafish model is the second most used vertebrate model, next to the mouse model. The zebrafish model has great potential for elucidating the functions of bioelectricity due to many advantages such as external development, transparent early embryogenesis, and tractable genetics. Here, we review genetic evidence from zebrafish mutants with fin-size and pigment changes related to ion channels and bioelectricity. In addition, we review the cell membrane voltage reporting and chemogenetic tools that have already been used or have great potential to be implemented in zebrafish models. Finally, new perspectives and opportunities for bioelectricity research with zebrafish are discussed.

The Function and the Affecting Factors of the Zebrafish Gut Microbiota

Gut microbiota has become a topical issue in unraveling the research mechanisms underlying disease onset and progression. As an important and potential “organ,” gut microbiota plays an important role in regulating intestinal epithelial cell differentiation, proliferation, metabolic function and immune response, angiogenesis and host growth. More recently, zebrafish models have been used to study the interactions between gut microbiota and hosts. It has several advantages, such as short reproductive cycle, low rearing cost, transparent larvae, high genomic similarity to humans, and easy construction of germ-free (GF) and transgenic zebrafish. In our review, we reviewed a large amount of data focusing on the close relationship between gut microbiota and host health. Moreover, we outlined the functions of gut microbiota in regulating intestinal epithelial cell differentiation, intestinal epithelial cell proliferation, metabolic function, and immune response. More, we summarized major factors that can influence the composition, abundance, and diversity of gut microbiota, which will help us to understand the significance of gut microbiota in regulating host biological functions and provide options for maintaining the balance of host health.

Identifying drivers of breast cancer metastasis in progressively invasive subpopulations of zebrafish-xenografted MDA-MB-231

Cancer metastasis is the primary cause of the high mortality rate among human cancers. Efforts to identify therapeutic agents targeting cancer metastasis frequently fail to demonstrate efficacy in clinical trials despite strong preclinical evidence. Until recently, most preclinical studies used mouse models to evaluate anti-metastatic agents. Mouse models are time-consuming and expensive. In addition, an important drawback is that mouse models inadequately model the early stages of metastasis which plausibly leads to the poor correlation with clinical outcomes.

Here, we report an in vivo model based on xenografted zebrafish embryos where we select for progressively invasive subpopulations of MDA-MB-231 breast cancer cells. A subpopulation analogous to circulating tumor cells found in human cancers was selected by injection of MDA-MB-231 cells into the yolk sacs of 2 days post-fertilized zebrafish embryos and selecting cells that migrated to the tail. The selected subpopulation derived from MDA-MB-231 cells were increasingly invasive in zebrafish. Isolation of these subpopulations and propagation in vitro revealed morphological changes consistent with activation of an epithelial-mesenchymal transition program. Differential gene analysis and knockdown of genes identified gene-candidates (DDIT4, MT1X, CTSD, and SERPINE1) as potential targets for anti-metastasis therapeutics. Furthermore, RNA-splicing analysis reinforced the importance of BIRC5 splice variants in breast cancer metastasis. This is the first report using zebrafish to isolate and expand progressively invasive populations of human cancer cells. The model has potential applications in understanding the metastatic process, identification and/or development of therapeutics that specifically target metastatic cells and formulating personalized treatment strategies for individual cancer patients.

Recent research advances of the biomimetic tumor microenvironment and regulatory factors on microfluidic devices: A systematic review

Tumor microenvironment is a multicomponent system consisting of tumor cells, noncancer cells, extracellular matrix, and signaling molecules, which hosts tumor cells with integrated biophysical and biochemical elements. Because of its critical involvement in tumor genesis, invasion, metastasis, and resistance, the tumor microenvironment is emerging as a hot topic of tumor biology and a prospective therapeutic target. Unfortunately, the complex of microenvironment modeling in vitro is technically challenging and does not effectively generalize the local tumor tissue milieu. Recently, significant advances in microfluidic technologies have provided us with an approach to imitate physiological systems that can be utilized to mimic the characterization of tumor responses with pathophysiological relevance in vitro. In this review, we highlight the recent progress and innovations in microfluidic technology that facilitates the tumor microenvironment study. We also discuss the progress and future perspective of microfluidic bionic approaches with high efficiency for the study of tumor microenvironment and the challenges encountered in cancer research, drug discovery, and personalized therapy.

Zebrafish as an experimental model for the simulation of neurological and craniofacial disorders

Zebrafish have gained momentum as a leading experimental model in recent years. At present, the zebrafish vertebrate model is increasingly used due to its multifactorial similarities to humans that include genetic, organ, and cellular factors. With the emergence of novel research techniques that are very expensive, it is necessary to develop affordable and valid experimental models. This review aimed to highlight some of the most important similarities between zebrafish and humans by emphasizing the relevance of the first in simulating neurological disorders and craniofacial deformity.

Use of Zebrafish Models to Boost Research in Rare Genetic Diseases

Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by a single genetic disease (from 1/2000 to 1/more than 1,000,000), the total number of patients concerned account for approximatively 400 million peoples worldwide. Finding treatments remains challenging due to the complexity of these diseases, the small number of patients and the challenge in conducting clinical trials. Therefore, innovative preclinical research strategies are required. The zebrafish has emerged as a powerful animal model for investigating rare diseases. Zebrafish combines conserved vertebrate characteristics with high rate of breeding, limited housing requirements and low costs. More than 84% of human genes responsible for diseases present an orthologue, suggesting that the majority of genetic diseases could be modelized in zebrafish. In this review, we emphasize the unique advantages of zebrafish models over other in vivo models, particularly underlining the high throughput phenotypic capacity for therapeutic screening. We briefly introduce how the generation of zebrafish transgenic lines by gene-modulating technologies can be used to model rare genetic diseases. Then, we describe how zebrafish could be phenotyped using state-of-the-art technologies. Two prototypic examples of rare diseases illustrate how zebrafish models could play a critical role in deciphering the underlying mechanisms of rare genetic diseases and their use to identify innovative therapeutic solutions.

Mitochondrial connections with immune system in Zebrafish

Mitochondria are organelles commonly associated with adenosine triphosphate (ATP) formation through the oxidative phosphorylation (OXPHOS) process. However, mitochondria are also responsible for functions such as calcium homeostasis, apoptosis, autophagy, and production of reactive oxygen species (ROS) that, in conjunction, can lead to different cell fate decisions. Mitochondrial morphology changes rely on nutrients' availability and the bioenergetics demands of the cells, in a process known as mitochondrial dynamics, which includes both fusion and fission. This organelle senses the microenvironment and can modify the cells to either a pro or anti-inflammatory profile. The zebrafish has been increasingly used to research mitochondrial dynamics and its connection with the immune system since the pathways and molecules involved in these processes are conserved on this fish. Several genetic tools and technologies are currently available to analyze the behavior of mitochondria in zebrafish. However, even though zebrafish presents several similar processes known in mammals, the effect of the mitochondria in the immune system has not been so broadly studied in this model. In this review, we summarize the current knowledge in zebrafish studies regarding mitochondrial function and immuno metabolism.

Inducible Liver Cancer Models in Transgenic Zebrafish to Investigate Cancer Biology

Primary liver cancer is one of the most prevalent and deadly cancers, which incidence continues to increase while treatment response remains poor; thus, in-depth understanding of tumour events is necessary to develop more effective therapies. Animal models for liver cancer are powerful tools to reach this goal. Over the past decade, our laboratory has established multiple oncogene transgenic zebrafish lines that can be robustly induced to develop liver cancer. Histological, transcriptomic and molecular analyses validate the use of these transgenic zebrafish as experimental models for liver cancer. In this review, we provide a comprehensive summary of our findings with these inducible zebrafish liver cancer models in tumour initiation, oncogene addiction, tumour microenvironment, gender disparity, cancer cachexia, drug screening and others. Induced oncogene expression causes a rapid change of the tumour microenvironment such as inflammatory responses, increased vascularisation and rapid hepatic growth. In several models, histologically-proven carcinoma can be induced within one week of chemical inducer administration. Interestingly, the induced liver tumours show the ability to regress when the transgenic oncogene is suppressed by the withdrawal of the chemical inducer. Like human liver cancer, there is a strong bias of liver cancer severity in male zebrafish. After long-term tumour progression, liver cancer-bearing zebrafish also show symptoms of cancer cachexia such as muscle-wasting. In addition, the zebrafish models have been used to screen for anti-metastasis drugs as well as to evaluate environmental toxicants in carcinogenesis. These findings demonstrated that these inducible zebrafish liver cancer models provide rapid and convenient experimental tools for further investigation of fundamental cancer biology, with the potential for the discovery of new therapeutic approaches.

Understanding the effects of Moringa oleifera in chronic unpredictable stressed zebrafish using metabolomics analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Moringa leaves have been used for thousands of years to maintain skin health and mental fitness. People also use it to relieves pain and stress.

AIM OF THE STUDY

To determine the effects of Moringa oleifera leaves ethanol-aqueous (ratio 7:3) extract (MOLE) on the chronically stressed zebrafish.

METHOD

The changes in the stress-related behaviour and the metabolic pathways in response to MOLE treatment in zebrafish were studied. A chronic unpredictable stress model was adopted in which zebrafish were induced with different stressors for 14 days. Stress-related behaviour was assessed using a depth-preference test and a light and dark test. Three doses of MOLE (500, 1000, and 2000 mg/L) were administered to the zebrafish. Upon sacrifice, the brains were harvested and processed for LC-MS QTOF based, global metabolomics analysis.

RESULTS

We observed significant changes in the behavioural parameters, where the swimming time at the light phase and upper phase of the tank were increased in the chronically stressed zebrafish treated with MOLE compared to those zebrafish which were not treated. Further, distinctive metabolite profiles were observed in zebrafish with different treatments. Several pathways that shed light on effects of MOLE were identified. MOLE is believed to relieve stress by regulating pathways that are involved in the metabolism of purine, glutathione, arginine and proline, D-glutamine, and D-glutamate.

CONCLUSION

MOLE is potentially an effective stress reliever. However, its effects in human needs to be confirmed with a systematic randomised control trial.

Cytotoxicity of 4-hydroxy-N-(naphthalen-1-yl)-2-oxo-2H-chromene-3-carboxamide in multidrug-resistant cancer cells through activation of PERK/eIF2α/ATF4 pathway

After decades of research, multidrug resistance (MDR) remains a huge challenge in cancer treatment. In this study, the cytotoxic of 4-hydroxy-N-(naphthalen-1-yl)-2-oxo-2H-chromene-3-carboxamide (MCC1734) has been investigated towards multidrug-resistant cancer cell lines. MCC1734 exerted cytotoxicity on cell lines expressing different mechanisms of drug resistance (P-glycoprotein, BCRP, ABCB5, EGFR, p53 knockout) to a different extent. Interestingly, sensitive CCRF-CEM cells and multidrug-resistant P-gp-overexpressing CEM/ADR5000 cells represented similar sensitivity towards MCC1734, indicating MCC1734 can bypass P-gp-mediated resistance. Microarray-based mRNA expression revealed that MCC1734 affected cells by multiple pathways, including cell cycle regulation, mitochondrial dysfunction, apoptosis signaling, and EIF2 signaling. MCC1734 stimulated the generation of excessive reactive oxygen species and the collapse of mitochondria membrane potential in CCRF-CEM cells, companied by the arrest of the cell cycle in the G₂M phase and apoptosis induction as determined by flow cytometry. In addition, our immunoblotting analysis highlighted that MCC1734 triggered endoplasmic reticulum (ER) stress, evidenced by the activation of p-PERK, p-eIF2α, ATF4 and CHOP. The anti-cancer effects of MCC1734 were further observed in vivo using human xenograft tumors transplanted to zebrafish, providing further support for MCC1734 as a promising new candidate for cancer drug development.

Benefits of Zebrafish Xenograft Models in Cancer Research

As a promising in vivo tool for cancer research, zebrafish have been widely applied in various tumor studies. The zebrafish xenograft model is a low-cost, high-throughput tool for cancer research that can be established quickly and requires only a small sample size, which makes it favorite among researchers. Zebrafish patient-derived xenograft (zPDX) models provide promising evidence for short-term clinical treatment. In this review, we discuss the characteristics and advantages of zebrafish, such as their transparent and translucent features, the use of vascular fluorescence imaging, the establishment of metastatic and intracranial orthotopic models, individual pharmacokinetics measurements, and tumor microenvironment. Furthermore, we introduce how these characteristics and advantages are applied other in tumor studies. Finally, we discuss the future direction of the use of zebrafish in tumor studies and provide new ideas for the application of it.

Review of diseases and health management in zebrafish Danio rerio (Hamilton 1822) in research facilities

The use of zebrafish (Danio rerio) in biomedical research has expanded at a tremendous rate over the last two decades. Along with increases in laboratories using this model, we are discovering new and important diseases. We review here the important pathogens and diseases based on some 20 years of research and findings from our diagnostic service at the NIH-funded Zebrafish International Resource Center. Descriptions of the present status of biosecurity programmes and diagnostic and treatment approaches are included. The most common and important diseases and pathogens are two parasites, Pseudoloma neurophilia and Pseudocapillaria tomentosa, and mycobacteriosis caused by Mycobacterium chelonae, M. marinum and M. haemophilum. Less common but deadly diseases are caused by Edwardsiella ictaluri and infectious spleen and kidney necrosis virus (ISKNV). Hepatic megalocytosis and egg-associated inflammation and fibroplasia are common, apparently non-infectious, in zebrafish laboratories. Water quality diseases include supersaturation and nephrocalcinosis. Common neoplasms are spindle cell sarcomas, ultimobranchial tumours, spermatocytic seminomas and a small-cell carcinoma that is caused by a transmissible agent. Despite the clear biosecurity risk, researchers continue to use fish from pet stores, and here, we document two novel coccidia associated with significant lesions in zebrafish from one of these stores.

Review of diseases and health management in zebrafish Danio rerio (Hamilton 1822) in research facilities

The use of zebrafish (Danio rerio) in biomedical research has expanded at a tremendous rate over the last two decades. Along with increases in laboratories using this model, we are discovering new and important diseases. We review here the important pathogens and diseases based on some 20 years of research and findings from our diagnostic service at the NIH-funded Zebrafish International Resource Center. Descriptions of the present status of biosecurity programmes and diagnostic and treatment approaches are included. The most common and important diseases and pathogens are two parasites, Pseudoloma neurophilia and Pseudocapillaria tomentosa, and mycobacteriosis caused by Mycobacterium chelonae, M. marinum and M. haemophilum. Less common but deadly diseases are caused by Edwardsiella ictaluri and infectious spleen and kidney necrosis virus (ISKNV). Hepatic megalocytosis and egg-associated inflammation and fibroplasia are common, apparently non-infectious, in zebrafish laboratories. Water quality diseases include supersaturation and nephrocalcinosis. Common neoplasms are spindle cell sarcomas, ultimobranchial tumours, spermatocytic seminomas and a small-cell carcinoma that is caused by a transmissible agent. Despite the clear biosecurity risk, researchers continue to use fish from pet stores, and here, we document two novel coccidia associated with significant lesions in zebrafish from one of these stores.

In Vivo Targeting of Xenografted Human Cancer Cells with Functionalized Fluorescent Silica Nanoparticles in Zebrafish

Developing nanoparticles capable of detecting, targeting, and destroying cancer cells is of great interest in the field of nanomedicine. In vivo animal models are required for bridging the nanotechnology to its biomedical application. The mouse represents the traditional animal model for preclinical testing; however, mice are relatively expensive to keep and have long experimental cycles due to the limited progeny from each mother. The zebrafish has emerged as a powerful model system for developmental and biomedical research, including cancer research. In particular, due to its optical transparency and rapid development, zebrafish embryos are well suited for real-time in vivo monitoring of the behavior of cancer cells and their interactions with their microenvironment. This method was developed to sequentially introduce human cancer cells and functionalized nanoparticles in transparent Casper zebrafish embryos and monitor in vivo recognition and targeting of the cancer cells by nanoparticles in real time. This optimized protocol shows that fluorescently labeled nanoparticles, which are functionalized with folate groups, can specifically recognize and target metastatic human cervical epithelial cancer cells labeled with a different fluorochrome. The recognition and targeting process can occur as early as 30 min postinjection of the nanoparticles tested. The whole experiment only requires the breeding of a few pairs of adult fish and takes less than 4 days to complete. Moreover, zebrafish embryos lack a functional adaptive immune system, allowing the engraftment of a wide range of human cancer cells. Hence, the utility of the protocol described here enables the testing of nanoparticles on various types of human cancer cells, facilitating the selection of optimal nanoparticles in each specific cancer context for future testing in mammals and the clinic.

Zebrafish as an alternative animal model in human and animal vaccination research

Much of medical research relies on animal models to deepen knowledge of the causes of animal and human diseases, as well as to enable the development of innovative therapies. Despite rodents being the most widely used research model worldwide, in recent decades, the use of the zebrafish (Danio rerio) model has exponentially been adopted among the scientific community. This is because such a small tropical freshwater teleost fish has crucial genetic, anatomical and physiological homology with mammals. Therefore, zebrafish constitutes an excellent experimental model for behavioral, genetic and toxicological studies which unravels the mechanism of various human diseases. Furthermore, it serves well to test new therapeutic agents, such as the safety of new vaccines. The aim of this review was to provide a systematic literature review on the most recent studies carried out on the topic. It presents numerous advantages of this type of animal model in tests of efficacy and safety of both animal and human vaccines, thus highlighting gains in time and cost reduction of research and analyzes.

TLD1433 Photosensitizer Inhibits Conjunctival Melanoma Cells in Zebrafish Ectopic and Orthotopic Tumour Models

The ruthenium-based photosensitizer (PS) TLD1433 has completed a phase I clinical trial for photodynamic therapy (PDT) treatment of bladder cancer. Here, we investigated a possible repurposing of this drug for treatment of conjunctival melanoma (CM). CM is a rare but often deadly ocular cancer. The efficacy of TLD1433 was tested on several cell lines from CM (CRMM1, CRMM2 and CM2005), uveal melanoma (OMM1, OMM2.5, MEL270), epidermoid carcinoma (A431) and cutaneous melanoma (A375). Using 15 min green light irradiation (21 mW/cm², 19 J.cm^-2, 520 nm), the highest phototherapeutic index (PI) was reached in CM cells, with cell death occurring via apoptosis and necrosis. The therapeutic potential of TLD1433 was hence further validated in zebrafish ectopic and newly-developed orthotopic CM models. Fluorescent CRMM1 and CRMM2 cells were injected into the circulation of zebrafish (ectopic model) or behind the eye (orthotopic model) and 24 h later, the engrafted embryos were treated with the maximally-tolerated dose of TLD1433. The drug was administrated in three ways, either by (i) incubating the fish in drug-containing water (WA), or (ii) injecting the drug intravenously into the fish (IV), or (iii) injecting the drug retro-orbitally (RO) into the fish. Optimally, four consecutive PDT treatments were performed on engrafted embryos using 60 min drug-to-light intervals and 90 min green light irradiation (21 mW/cm², 114 J.cm^-2, 520 nm). This PDT protocol was not toxic to the fish. In the ectopic tumour model, both systemic administration by IV injection and RO injection of TLD1433 significantly inhibited growth of engrafted CRMM1 and CRMM2 cells. However, in the orthotopic model, tumour growth was only attenuated by localized RO injection of TLD1433. These data unequivocally prove that the zebrafish provides a fast vertebrate cancer model that can be used to test the administration regimen, host toxicity and anti-cancer efficacy of PDT drugs against CM. Based on our results, we suggest repurposing of TLD1433 for treatment of incurable CM and further testing in alternative pre-clinical models.

Animal Models to Study Cancer and Its Microenvironment

Cancers are complex tissues composed by genetically altered cancer cells and stromal elements such as inflammatory/immune cells, fibroblasts, endothelial cells and pericytes, neuronal cells, and a non-cellular component, the extracellular matrix. The complex network of interactions and crosstalk established between cancer cells and the supportig cellular and non-cellular components of the microenvironment are of extreme importance for tumor initiation and progression, strongly impacting the course and the outcome of the disease. Therefore, a better understanding of the tumorigenic processes implies the combined study of the cancer cell and the biologic, chemical and mechanic constituents of the tumor microenvironment, as their concerted action plays a major role in the carcinogenic pathway and is a key determinant of the efficacy of anti-cancer treatments. The use of animal models (e.g. Mouse, Zebrafish and Drosophila) to study cancer has greatly impacted our understanding of the processes governing initiation, progression and metastasis and allowed the discovery and pre-clinical validation of novel cancer treatments as it allows to recreate tumor development in a more pathophysiologic environment.

Anticancer Plants: A Review of the Active Phytochemicals, Applications in Animal Models, and Regulatory Aspects

The rising burden of cancer worldwide calls for an alternative treatment solution. Herbal medicine provides a very feasible alternative to western medicine against cancer. This article reviews the selected plant species with active phytochemicals, the animal models used for these studies, and their regulatory aspects. This study is based on a meticulous literature review conducted through the search of relevant keywords in databases, Web of Science, Scopus, PubMed, and Google Scholar. Twenty plants were selected based on defined selection criteria for their potent anticancer compounds. The detailed analysis of the research studies revealed that plants play an indispensable role in fighting different cancers such as breast, stomach, oral, colon, lung, hepatic, cervical, and blood cancer cell lines. The in vitro studies showed cancer cell inhibition through DNA damage and activation of apoptosis-inducing enzymes by the secondary metabolites in the plant extracts. Studies that reported in vivo activities of these plants showed remarkable results in the inhibition of cancer in animal models. Further studies should be performed on exploring more plants, their active compounds, and the mechanism of anticancer actions for use as standard herbal medicine.

Comparison of responsiveness to cancer development and anti-cancer drug in three different C57BL/6N stocks

In our efforts to understand the systemic features of tumors, the importance of animal models is increasing due to the recent growth in the development of immunotherapy and targeted therapies. This has resulted in increased attention towards tumor animal models using C57BL/6N, which are mainly used in immunological studies. In this study, the C57BL/6NKorl stock and two other commercial stocks (C57BL/6NA and C57BL/N6B) are evaluated by comparing the occurrence of tumors using the syngeneic model; furthermore, we compare the response to anti-cancer drugs in the syngeneic model by evaluating survival, growth of tumors, proliferation and molecular biology analysis. In the syngeneic model using LLC (Lewis lung carcinoma) cells, the survival of mice and growth of the tumor showed a better response in the C57BL/6NKorl stock, and was dependent on the cell concentration of the dosing tumor, as compared to the other C57BL/6N stocks. However, the Ki-67 staining showed only little difference in cell proliferation within the tumor tissue each mouse stocks. Comparing the sensitivity to anti-cancer drug by examining changes in growth, volume and weight revealed that cisplatin treatment for tumor-bearing C57BL/6NKorl was more dependent on concentration. The Ki-67 staining, however, showed no difference among the C57BL/6N stocks after cisplatin treatment. The expressions of p27 and p53 tumor suppressor proteins, caspase-3 and Bax showed dose-dependent increase after exposure to cisplatin, whereas the expression of Bcl-2 was reduced in a dose-dependent manner. Furthermore, the expressions of MMP-2 and VEGF involved in metastasis, as well as inflammatory genes IL-1β, IL-6 and IL-10, showed dose-dependent decrease in tumor tissue after cisplatin exposure. Differences observed among the C57BL/6N stocks were not significant. Taken together, our studies reveal that C57BL/6NKorl has the potential of being a useful biological resource established in Korea, as it does not differ from the two commercially available C57BL/6N stocks when considering response to tumor generation and sensitivity to anti-cancer drugs using the syngeneic tumor model.

Tumor microenvironment and stroma in intestinal adenocarcinomas and associated metastases in Atlantic salmon broodfish (Salmo salar)

Animal models are invaluable tools in cancer research. In this context, salmon is a promising candidate. Intestinal adenocarcinoma with metastases may be induced as a consequence of a plant-based diet triggering the inflammation - dysplasia- carcinogenesis pathway. Here, we investigate the stroma and the presence and nature of immune cells in such tumors by staining for mast cells, immunohistochemistry for T cells and antigen-presenting cells and in situ hybridization for B cells. In intestinal tumors, substantial amounts of T cells were detected in the stroma, whilst MHC class II⁺ cells were mainly among the cancerous cells. Ig⁺ cells were observed primarily in the tumor periphery. Mast cells showed a strong association with stroma. In metastases, scarce amounts of T cells were detected, whilst MHC I and II-reactivity varied, some tumors being completely negative. Ig⁺ cells were scattered around the metastatic tissue in no particular pattern, but were occasionally observed within clusters of tumor cells. Small numbers of mast cells were detected in the stroma. To the best of our knowledge, this is the first report addressing immune cells in fish tumors. The teleost tumor microenvironment seems comparable to that of mammals, making fish interesting model animals in oncoimmunology research.

Cancer-Cell-Activated Photodynamic Therapy Assisted by Cu(II)-Based Metal-Organic Framework

Activation of photosensitizers (PSs) in targeted lesion and minimization of reactive oxygen species (ROS) depletion by endogenous antioxidants constitute promising approaches to perform highly effective image-guided photodynamic therapy (PDT) with minimal non-specific phototoxicity. Traditional strategies to fabricate controllable PS platforms rely on molecular design, which requires specific modification of each PS before PDT. Therefore, construction of a general tumor-responsive PDT platform with minimum ROS loss from endogenous antioxidant, typically glutathione (GSH), is highly desirable. Herein, MOF-199, a Cu(II) carboxylate-based metal-organic framework (MOF), is selected to serve as an inert carrier to load PSs with prohibited photosensitization during delivery. After cellular uptake, Cu (II) in the MOFs effectively scavenges endogenous GSH, concomitantly induces decomposition of MOF-199 to release the encapsulated PSs, and recovers their ROS generation. In vitro and in vivo experiments demonstrate highly effective cancer cell ablation and anticancer PDT with diminished normal cell phototoxicity. This strategy is generally applicable to PSs with both aggregation-induced emission and aggregation-caused quenching to implement activatable and enhanced image-guided PDT.

Inducible Intestine-Specific Expression of krasV12 Triggers Intestinal Tumorigenesis In Transgenic Zebrafish

KRAS mutations are a major risk factor in colorectal cancers. In particular, a point mutation of KRAS of amino acid 12, such as KRAS^V12, renders it stable activity in oncogenesis. We found that kras^V12 promotes intestinal carcinogenesis by generating a transgenic zebrafish line with inducible kras^V12 expression in the intestine, Tg(ifabp:EGFP-kras^V12). The transgenic fish generated exhibited significant increases in the rates of intestinal epithelial outgrowth, proliferation, and cross talk in the active Ras signaling pathway involving in epithelial-mesenchymal transition (EMT). These results provide in vivo evidence of Ras pathway activation via kras^V12 overexpression. Long-term transgenic expression of kras^V12 resulted in enteritis, epithelial hyperplasia, and tubular adenoma in adult fish. This was accompanied by increased levels of the signaling proteins p-Erk and p-Akt and by downregulation of the EMT marker E-cadherin. Furthermore, we also observed a synergistic effect of kras^V12 expression and dextran sodium sulfate treatment to enhance intestinal tumor in zebrafish. Our results demonstrate that kras^V12 overexpression induces intestinal tumorigenesis in zebrafish, which mimics intestinal tumor formation in humans. Thus, our transgenic zebrafish may provide a valuable in vivo platform that can be used to investigate tumor initiation and anticancer drugs for gastrointestinal cancers.

Glucocorticoid deficiency causes transcriptional and post-transcriptional reprogramming of glutamine metabolism

Background

Deficient glucocorticoid biosynthesis leading to adrenal insufficiency is life-threatening and is associated with significant co-morbidities. The affected pathways underlying the pathophysiology of co-morbidities due to glucocorticoid deficiency remain poorly understood and require further investigation.

Methods

To explore the pathophysiological processes related to glucocorticoid deficiency, we have performed global transcriptional, post-transcriptional and metabolic profiling of a cortisol-deficient zebrafish mutant with a disrupted ferredoxin (fdx1b) system.

Findings

fdx1b^−/− mutants show pervasive reprogramming of metabolism, in particular of glutamine-dependent pathways such as glutathione metabolism, and exhibit changes of oxidative stress markers. The glucocorticoid-dependent post-transcriptional regulation of key enzymes involved in de novo purine synthesis was also affected in this mutant. Moreover, fdx1b^−/− mutants exhibit crucial features of primary adrenal insufficiency, and mirror metabolic changes detected in primary adrenal insufficiency patients.

Interpretation

Our study provides a detailed map of metabolic changes induced by glucocorticoid deficiency as a consequence of a disrupted ferredoxin system in an animal model of adrenal insufficiency. This improved pathophysiological understanding of global glucocorticoid deficiency informs on more targeted translational studies in humans suffering from conditions associated with glucocorticoid deficiency.

Fund

Marie Curie Intra-European Fellowships for Career Development, HGF-programme BIFTM, Deutsche Forschungsgemeinschaft, BBSRC.

The transcriptional response of skin to fluorescent light exposure in viviparous (Xiphophorus) and oviparous (Danio, Oryzias) fishes

Differences in light sources are common in animal facilities and potentially can impact experimental results. Here, the potential impact of lighting differences on skin transcriptomes has been tested in three aquatic animal models commonly utilized in biomedical research, (Xiphophorus maculatus (platyfish), Oryzias latipes (medaka) and Danio rerio (zebrafish). Analysis of replicate comparative RNA-Seq data showed the transcriptional response to commonly utilized 4100K or "cool white" fluorescent light (FL) is much greater in platyfish and medaka than in zebrafish. FL induces genes associated with inflammatory and immune responses in both medaka and zebrafish; however, the platyfish exhibit suppression of genes involved with immune/inflammation, as well as genes associated with cell cycle progression. Furthermore, comparative analyses of gene expression data from platyfish UVB exposures, with medaka and zebrafish after exposure to 4100K FL, show comparable effects on the same stress pathways. We suggest the response to light is conserved, but that long-term adaptation to species specific environmental niches has resulted in a shifting of the wavelengths required to incite similar "genetic" responses in skin. We forward the hypothesis that the "genetic perception" of light may have evolved differently than ocular perception and suggest that light type (i.e., wavelengths emitted) is an important parameter to consider in experimental design.

Identification of RECK as an evolutionarily conserved tumor suppressor gene for zebrafish malignant peripheral nerve sheath tumors

Malignant peripheral nerve sheath tumors (MPNSTs) are a type of sarcoma with poor prognosis due to their complex genetic changes, invasive growth, and insensitivity to chemo- and radiotherapies. One of the most frequently lost chromosome arms in human MPNSTs is chromosome 9p. However, the cancer driver genes located on it remain largely unknown, except the tumor suppressor gene, p16 (INK4)/CDKN2A. Previously, we identified RECK as a tumor suppressor gene candidate on chromosome 9p using zebrafish-human comparative oncogenomics. In this study, we investigated the tumorigenesis of the reck gene using zebrafish genetic models in both tp53 and ribosomal protein gene mutation background. We also examined the biological effects of RECK gene restoration in human MPNST cell lines. These results provide the first genetic evidence that reck is a bona fide tumor suppressor gene for MPNSTs in zebrafish. In addition, restoration of the RECK gene in human MPNST cells leads to growth inhibition suggesting that the reactivation of RECK could serve as a potential therapeutic strategy for MPNSTs.

Vertebrate Genome Evolution in the Light of Fish Cytogenomics and rDNAomics

To understand the cytogenomic evolution of vertebrates, we must first unravel the complex genomes of fishes, which were the first vertebrates to evolve and were ancestors to all other vertebrates. We must not forget the immense time span during which the fish genomes had to evolve. Fish cytogenomics is endowed with unique features which offer irreplaceable insights into the evolution of the vertebrate genome. Due to the general DNA base compositional homogeneity of fish genomes, fish cytogenomics is largely based on mapping DNA repeats that still represent serious obstacles in genome sequencing and assembling, even in model species. Localization of repeats on chromosomes of hundreds of fish species and populations originating from diversified environments have revealed the biological importance of this genomic fraction. Ribosomal genes (rDNA) belong to the most informative repeats and in fish, they are subject to a more relaxed regulation than in higher vertebrates. This can result in formation of a literal 'rDNAome' consisting of more than 20,000 copies with their high proportion employed in extra-coding functions. Because rDNA has high rates of transcription and recombination, it contributes to genome diversification and can form reproductive barrier. Our overall knowledge of fish cytogenomics grows rapidly by a continuously increasing number of fish genomes sequenced and by use of novel sequencing methods improving genome assembly. The recently revealed exceptional compositional heterogeneity in an ancient fish lineage (gars) sheds new light on the compositional genome evolution in vertebrates generally. We highlight the power of synergy of cytogenetics and genomics in fish cytogenomics, its potential to understand the complexity of genome evolution in vertebrates, which is also linked to clinical applications and the chromosomal backgrounds of speciation. We also summarize the current knowledge on fish cytogenomics and outline its main future avenues.

Development of a novel zebrafish xenograft model in ache mutants using liver cancer cell lines

Acetylcholinesterase (AChE), an enzyme responsible for degradation of acetylcholine, has been identified as a prognostic marker in liver cancer. Although in vivo Ache tumorigenicity assays in mouse are present, no established liver cancer xenograft model in zebrafish using an ache mutant background exists. Herein, we developed an embryonic zebrafish xenograft model using epithelial (Hep3B) and mesenchymal (SKHep1) liver cancer cell lines in wild-type and ache sb55 sibling mutant larvae after characterization of cholinesterase expression and activity in cell lines and zebrafish larvae. The comparison of fluorescent signal reflecting tumor size at 3-days post-injection (dpi) revealed an enhanced tumorigenic potential and a reduced migration capacity in cancer cells injected into homozygous ache sb55 mutants when compared with the wild-type. Increased tumor load was confirmed using an ALU based tumor DNA quantification method modified for use in genotyped xenotransplanted zebrafish embryos. Confocal microscopy using the Huh7 cells stably expressing GFP helped identify the distribution of tumor cells in larvae. Our results imply that acetylcholine accumulation in the microenvironment directly or indirectly supports tumor growth in liver cancer. Use of this model system for drug screening studies holds potential in discovering new cholinergic targets for treatment of liver cancers.

Improving zebrafish embryo xenotransplantation conditions by increasing incubation temperature and establishing a proliferation index with ZFtool

BACKGROUND

Zebrafish (Danio rerio) is a model organism that has emerged as a tool for cancer research, cancer being the second most common cause of death after cardiovascular disease for humans in the developed world. Zebrafish is a useful model for xenotransplantation of human cancer cells and toxicity studies of different chemotherapeutic compounds in vivo. Compared to the murine model, the zebrafish model is faster, can be screened using high-throughput methods and has a lower maintenance cost, making it possible and affordable to create personalized therapies. While several methods for cell proliferation determination based on image acquisition and quantification have been developed, some drawbacks still remain. In the xenotransplantation technique, quantification of cellular proliferation in vivo is critical to standardize the process for future preclinical applications of the model.

METHODS

This study improved the conditions of the xenotransplantation technique - quantification of cellular proliferation in vivo was performed through image processing with our ZFtool software and optimization of temperature in order to standardize the process for a future preclinical applications. ZFtool was developed to establish a base threshold that eliminates embryo auto-fluorescence and measures the area of marked cells (GFP) and the intensity of those cells to define a 'proliferation index'.

RESULTS

The analysis of tumor cell proliferation at different temperatures (34 °C and 36 °C) in comparison to in vitro cell proliferation provides of a better proliferation rate, achieved as expected at 36°, a maintenance temperature not demonstrated up to now. The mortality of the embryos remained between 5% and 15%. 5- Fluorouracil was tested for 2 days, dissolved in the incubation medium, in order to quantify the reduction of the tumor mass injected. In almost all of the embryos incubated at 36 °C and incubated with 5-Fluorouracil, there was a significant tumor cell reduction compared with the control group. This was not the case at 34 °C.

CONCLUSIONS

Our results demonstrate that the proliferation of the injected cells is better at 36 °C and that this temperature is the most suitable for testing chemotherapeutic drugs like the 5-Fluorouracil.

Developmental social isolation affects adult behavior, social interaction, and dopamine metabolite levels in zebrafish

The zebrafish is a social vertebrate and an excellent translational model for a variety of human disorders. Abnormal social behavior is a hallmark of several human brain disorders. Social behavioral problems can arise as a result of adverse early social environment. Little is known about the effects of early social isolation in adult zebrafish. We compared zebrafish that were isolated for either short (7 days) or long duration (180 days) to socially housed zebrafish, testing their behavior across ontogenesis (ages 10, 30, 60, 90, 120, 180 days), and shoal cohesion and whole-brain monoamines and their metabolites in adulthood. Long social isolation increased locomotion and decreased shoal cohesion and anxiety in the open-field in adult. Additionally, both short and long social isolation reduced dopamine metabolite levels in response to social stimuli. Thus, early social isolation has lasting effects in zebrafish, and may be employed to generate zebrafish models of human neuropsychiatric conditions.

Characterization of prostate cancer cell progression in zebrafish xenograft model

Early diagnosis of prostate cancer (PCa) is critical for the application of efficient treatment to PCa patients. However, the majority of PCas remains indolent from several months to several years before malignancy. Current diagnosis methods have limitations in their reliability and are inefficient in time cost. Thus, an efficient in vivo PCa cell xenograft model is highly desired for diagnostic studies in PCas. In the present study we present a standardized procedure to create a PCa cell xenograft model using zebrafish (Danio rerio) as the host. PC3-CTR cells, a cell line from adenocarcinoma with stable expression of calcitonin receptor (CRT), were subcutaneously injected into zebrafish larvae at 48 h post fertilization. The nursing conditions for the larvae were optimized with stable survival rates of post hatch and post PC3-CTR cell injection. In this system, the progression of PC3-CTR cells in vivo was evaluated by migration and proliferation of the cells. Massive migrations of PC3 cells in vivo were observed at post injection day (PID)3. The injected PC3-CTR cells eventually invaded the whole larval zebrafish at PID5. Quantification of PC3-CTR cell proliferation was done using quantitative PCR (qPCR) analysis targeting the expression profiles of two PCa housekeeping genes, TATA-binding protein (TBP) and hypoxanthine phosphoribosyltransferase 1 (HPRT1) encoding genes. The excessive proliferation of PC3 cells in vivo was detected with both qPCR assays. Expression levels of one non-coding gene, prostate cancer associated 3 gene (pca3), and two other genes encoding transient receptor potential ion channel Melastatin 8 (trpm8) and prostate-specific membrane antigen (psma), showed a significantly enhanced aggressiveness of PC3-CTR cells in vivo. The model established in the present study provides an improved in vivo model for the diagnosis of PCas efficiently. This PCa cell xenograft model can also serve as a tool for high throughput anti-PCa drug screening in therapeutic treatments.

Animal Models to Study MicroRNA Function

The discovery of the microRNAs, lin-4 and let-7 as critical mediators of normal development in Caenorhabditis elegans and their conservation throughout evolution has spearheaded research toward identifying novel roles of microRNAs in other cellular processes. To accurately elucidate these fundamental functions, especially in the context of an intact organism, various microRNA transgenic models have been generated and evaluated. Transgenic C. elegans (worms), Drosophila melanogaster (flies), Danio rerio (zebrafish), and Mus musculus (mouse) have contributed immensely toward uncovering the roles of multiple microRNAs in cellular processes such as proliferation, differentiation, and apoptosis, pathways that are severely altered in human diseases such as cancer. The simple model organisms, C. elegans, D. melanogaster, and D. rerio, do not develop cancers but have proved to be convenient systesm in microRNA research, especially in characterizing the microRNA biogenesis machinery which is often dysregulated during human tumorigenesis. The microRNA-dependent events delineated via these simple in vivo systems have been further verified in vitro, and in more complex models of cancers, such as M. musculus. The focus of this review is to provide an overview of the important contributions made in the microRNA field using model organisms. The simple model systems provided the basis for the importance of microRNAs in normal cellular physiology, while the more complex animal systems provided evidence for the role of microRNAs dysregulation in cancers. Highlights include an overview of the various strategies used to generate transgenic organisms and a review of the use of transgenic mice for evaluating preclinical efficacy of microRNA-based cancer therapeutics.

Zebrafish models for functional and toxicological screening of nanoscale drug delivery systems: promoting preclinical applications

Preclinical screening with animal models is an important initial step in clinical translation of new drug delivery systems. However, establishing efficacy, biodistribution, and biotoxicity of complex, multicomponent systems in small animal models can be expensive and time-consuming. Zebrafish models represent an alternative for preclinical studies for nanoscale drug delivery systems. These models allow easy optical imaging, large sample size, and organ-specific studies, and hence an increasing number of preclinical studies are employing zebrafish models. In this review, we introduce various models and discuss recent studies of nanoscale drug delivery systems in zebrafish models. Also in the end, we proposed a guideline for the preclinical trials to accelerate the progress in this field.

A Porphyrin-Based Conjugated Polymer for Highly Efficient In Vitro and In Vivo Photothermal Therapy

Conjugated polymers have been increasingly studied for photothermal therapy (PTT) because of their merits including large absorption coefficient, facile tuning of exciton energy dissipation through nonradiative decay, and good therapeutic efficacy. The high photothermal conversion efficiency (PCE) is the key to realize efficient PTT. Herein, a donor-acceptor (D-A) structured porphyrin-containing conjugated polymer (PorCP) is reported for efficient PTT in vitro and in vivo. The D-A structure introduces intramolecular charge transfer along the backbone, resulting in redshifted Q band, broadened absorption, and increased extinction coefficient as compared to the state-of-art porphyrin-based photothermal reagent. Through nanoencapsulation, the dense packing of a large number of PorCP molecules in a single nanoparticle (NP) leads to favorable nonradiative decay, good photostability, and high extinction coefficient of 4.23 × 10⁴ m^-1 cm^-1 at 800 nm based on porphyrin molar concentration and the highest PCE of 63.8% among conjugated polymer NPs. With the aid of coloaded fluorescent conjugated polymer, the cellular uptake and distribution of the PorCP in vitro can be clearly visualized, which also shows effective photothermal tumor ablation in vitro and in vivo. This research indicates a new design route of conjugated polymer-based photothermal therapeutic materials for potential personalized theranostic nanomedicine.

Live imaging the earliest host innate immune response to preneoplastic cells using a zebrafish inducible KalTA4-ERT2/UAS system

As cancers develop, transformed cells hijack various host mechanisms and manipulate them to create a dynamic tumor microenvironment, which supports tumor growth. This protumorigenic microenvironment is made up of many different cell types, including transformed cells, fibroblasts, inflammatory cells, and endothelial cells, the interactions of which have been shown to play a role in sustaining tumor growth. Multiple reports implicate the inflammatory cells of the tumor microenvironment as having both pro- and antitumorigenic roles, the balance of which is vital for the progression of the tumor, and while our understanding of established cancers has vastly increased since the turn of the 21st Century, our knowledge of these cellular interactions at the earliest stages of cancer initiation and development remains relatively limited. This is largely due to difficulties in monitoring these processes in vivo and in real time. Since the late nineties, the zebrafish (Danio rerio) has emerged as a vital model organism, allowing studies of previously unattainable stages of tumor initiation in a vertebrate model system. Using genetic and live-imaging approaches, this model system can be used both independently to monitor stages of tumor progression from the earliest initiation stages and incorporated into previously established systems to investigate the interactions between cancer cells and the various cell types of the tumor microenvironment, including inflammatory cells. Here, we describe the use of an inducible KalTA4-ER^T2/UAS expression system in zebrafish, which allows spatial and temporal control of preneoplastic cell (PNC) growth and monitoring of innate immune cells in response to the developing PNC microenvironment.

Zebrafish Models of Human Leukemia: Technological Advances and Mechanistic Insights

Insights concerning leukemic pathophysiology have been acquired in various animal models and further efforts to understand the mechanisms underlying leukemic treatment resistance and disease relapse promise to improve therapeutic strategies. The zebrafish (Danio rerio) is a vertebrate organism with a conserved hematopoietic program and unique experimental strengths suiting it for the investigation of human leukemia. Recent technological advances in zebrafish research including efficient transgenesis, precise genome editing, and straightforward transplantation techniques have led to the generation of a number of leukemia models. The transparency of the zebrafish when coupled with improved lineage-tracing and imaging techniques has revealed exquisite details of leukemic initiation, progression, and regression. With these advantages, the zebrafish represents a unique experimental system for leukemic research and additionally, advances in zebrafish-based high-throughput drug screening promise to hasten the discovery of novel leukemia therapeutics. To date, investigators have accumulated knowledge of the genetic underpinnings critical to leukemic transformation and treatment resistance and without doubt, zebrafish are rapidly expanding our understanding of disease mechanisms and helping to shape therapeutic strategies for improved outcomes in leukemic patients.

Nanodiamond for biolabelling and toxicity evaluation in the zebrafish embryo in vivo

Nanodiamond (ND) has been proposed for various biomedical applications, including bioimaging, biosensing and drug delivery, owing to its physical-chemical properties and biocompatibility. Particularly, ND has been demonstrated as fluorescence- and Raman-detectable labels in many cellular models. Different surface functionalization methods have been developed, varying the ND's surface properties and rendering the possibility to attach biomolecules to provide interaction with biological targets. For this, toxicity is of major concern in animal models. Aside from cellular models, a cost-effective animal test will greatly facilitate the development of applications. In this study, we use the rapid, sensitive and reproducible zebrafish embryo model for in vivo nanotoxicity test. We optimize the conditions for using this animal model and analyze the zebrafish embryonic development in the presence of ND. ND is observed in the embryo in vivo using laser confocal fluorescence microscopy and fluorescence lifetime imaging. Using the zebrafish model for a safety evaluation of ND-based nanolabel is discussed.

Predominant Activation of JAK/STAT3 Pathway by Interleukin-6 Is Implicated in Hepatocarcinogenesis

Chronic inflammation is an important process leading to tumorigenesis. Therefore, targeting and controlling inflammation can be a promising cancer therapy. Inflammation is often caused by a variety of inflammatory cytokine such as the interleukin (IL)-6, a pleiotrophic cytokine known to be involved in the tumorigenesis. In this study, an in vivo hepatic tumorigenesis model of zebrafish was generated to demonstrate a direct consequence of the human IL6 expression causing hepatocarcinogenesis. To do this, an elevated expression of the hIL6 gene was established to specifically target the zebrafish hepatocytes by transgenesis. Interestingly, the elevated hIL6 expression caused the chronic inflammation which results in a massive infiltration of inflammatory cells. This eventually resulted in the generation of various dysplastic lesions such as clear cell, small cell, and large cell changes, and also eosinophilic and basophilic foci of hepatocellular alteration. Hepatocellular carcinoma was then developed in the transgenic zebrafish. Molecular characterization revealed upregulation of the downstream components involved in the IL6-mediated signaling pathways, especially PI3K/Akt and JAK/STAT3 pathways. Further investigation indicated that PI3K was the most reactive to the infiltrated inflammatory cells and dysplasia with large cell change, whereas STAT3 was heavily activated in the region with dysplastic foci, suggesting that the JAK/STAT3 pathway was mainly implicated in the hepatic tumorigenesis in the current model. Our present study provides an in vivo evidence of the relationship between chronic inflammation and tumorigenesis and reinforces the pivotal role of IL6 in the inflammation-associated hepatocarcinogenesis.

Ultrastructural Mapping of the Zebrafish Gastrointestinal System as a Basis for Experimental Drug Studies

Research in the field of gastroenterology is increasingly focused on the use of alternative nonrodent model organisms to provide new experimental tools to study chronic diseases. The zebrafish is a particularly valuable experimental platform to explore organ and cell structure-function relationships under relevant biological and pathobiological settings. This is due to its optical transparency and its close-to-human genetic makeup. To-date, the structure-function properties of the GIS of the zebrafish are relatively unexplored and limited to histology and fluorescent microscopy. Occasionally those studies include EM of a given subcellular process but lack the required full histological picture. In this work, we employed a novel combined biomolecular imaging approach in order to cross-correlate 3D ultrastructure over different length scales (optical-, X-ray micro-CT, and high-resolution EM). Our correlated imaging studies and subsequent data modelling provide to our knowledge the first detailed 3D picture of the zebrafish larvae GIS. Our results provide unequivocally a limit of confidence for studying various digestive disorders and drug delivery pathways in the zebrafish.

Development of a vestibular schwannoma xenograft zebrafish model for in vivo antitumor drug screening

OBJECTIVES/HYPOTHESIS

The development of a simple, reliable, and cost-effective animal model greatly facilitates disease treatment. We aimed to establish a rapid, simple, and reproducible live zebrafish vestibular schwannoma xenograft model for antitumor drug screening.

METHODS

We optimized each of the following conditions for tumor cell xenografts in zebrafish larvae: larval stage, incubation temperature, and injected cell number. We used NF2-/-mouse Schwann (SC4) cells and generated mCherry fluorescent protein-expressing cells prior to injection into zebrafish larvae. SC4 cells were counted using a fluorescence microscope, suspended in 10% fetal bovine serum, and injected into the center of the yolk sac using a microinjection system. The injected embryos were transferred to E3 medium (for zebrafish embryos), and subsequent tumor formation was observed by fluorescence microscopy over a 5-day period. To validate our model, xenografted embryos were transferred into 6-well plates (5 embryos per well) and treated with everolimus, a known antitumor drug.

RESULTS

mCherry fluorescent protein-expressing SC4 cells were successfully grafted into the yolk sacs of zebrafish embryos without any immunosuppressant treatment. At 2 days postinjection, the xenografted cells had grown into tumor masses. The optimal speed of tumor formation depended on the larval stage (30 hpf), incubation temperature (31°C), and injected cell number (200 cells). In preliminary tests, everolimus treatment yielded a > 20% reduction in the number of SC4 cells in the yolk.

CONCLUSION

Our in vivo model has the potential to greatly facilitate vestibular schwannoma treatment because of its speed, simplicity, reproducibility, and amenability to live imaging.

LEVEL OF EVIDENCE

NA Laryngoscope, 126:E409-E415, 2016.

CREB engages C/EBPδ to initiate leukemogenesis

cAMP response element binding protein (CREB) is frequently overexpressed in acute myeloid leukemia (AML) and acts as a proto-oncogene; however, it is still debated whether such overactivation alone is able to induce leukemia as its pathogenetic downstream signaling is still unclear. We generated a zebrafish model overexpressing CREB in the myeloid lineage, which showed an aberrant regulation of primitive hematopoiesis, and in 79% of adult CREB-zebrafish a block of myeloid differentiation, triggering to a monocytic leukemia akin the human counterpart. Gene expression analysis of CREB-zebrafish revealed a signature of 20 differentially expressed human homologous CREB targets in common with pediatric AML. Among them, we demonstrated that CREB overexpression increased CCAAT-enhancer-binding protein-δ (C/EBPδ) levels to cause myeloid differentiation arrest, and the silencing of CREB-C/EBPδ axis restored myeloid terminal differentiation. Then, C/EBPδ overexpression was found to identify a subset of pediatric AML affected by a block of myeloid differentiation at monocytic stage who presented a significant higher relapse risk and the enrichment of aggressive signatures. Finally, this study unveils the aberrant activation of CREB-C/EBPδ axis concurring to AML onset by disrupting the myeloid cell differentiation process. We provide a novel in vivo model to perform high-throughput drug screening for AML cure improvement.

Optical micromanipulation of nanoparticles and cells inside living zebrafish

Regulation of biological processes is often based on physical interactions between cells and their microenvironment. To unravel how and where interactions occur, micromanipulation methods can be used that offer high-precision control over the duration, position and magnitude of interactions. However, lacking an in vivo system, micromanipulation has generally been done with cells in vitro, which may not reflect the complex in vivo situation inside multicellular organisms. Here using optical tweezers we demonstrate micromanipulation throughout the transparent zebrafish embryo. We show that different cells, as well as injected nanoparticles and bacteria can be trapped and that adhesion properties and membrane deformation of endothelium and macrophages can be analysed. This non-invasive micromanipulation inside a whole-organism gives direct insights into cell interactions that are not accessible using existing approaches. Potential applications include screening of nanoparticle-cell interactions for cancer therapy or tissue invasion studies in cancer and infection biology.