Maximizing mouse cancer models

Preclinical Models of Hepatocellular Carcinoma: Current Utility, Limitations, and Challenges

Hepatocellular carcinoma (HCC), the predominant primary liver tumor, remains one of the most lethal cancers worldwide, despite the advances in therapy in recent years. In addition to the traditional chemically and dietary-induced HCC models, a broad spectrum of novel preclinical tools have been generated following the advent of transgenic, transposon, organoid, and in silico technologies to overcome this gloomy scenario. These models have become rapidly robust preclinical instruments to unravel the molecular pathogenesis of liver cancer and establish new therapeutic approaches against this deadly disease. The present review article aims to summarize and discuss the commonly used preclinical models for HCC, evaluating their strengths and weaknesses.

Microenvironment M1/M2 macrophages and tumoral progression vary within C57BL/6 mice from same substrain in prostate cancer model

Cancer mice models are critical for immune-oncology research; they provide conditions to explore tumor immunoenviroment aiming to advance knowledge and treatment development. Often, research groups breed their own mice colonies. To assess the effect of C57BL/6 mice breeding nuclei in prostate cancer development and intratumoral macrophage populations, an isotransplantation experiment was performed. C57BL/6J mice from two breeding nuclei (nA and nB) were employed for prostate adenocarcinoma TRAMP-C1 cell implantation; tumor growth period and intratumoral macrophage profile were measured. BL/6nB mice (54%) showed tumor implantation after 69-day growth period while BL/6nA implantation reached 100% across tumor growth period (28 days). No difference in total macrophage populations was observed between groups within several tumoral regions; significantly higher M2 macrophage profile was observed in tumor microenvironments from both mice groups. Nevertheless, BL/6nB tumors showed around twice the population of M1 profile (11-27%) than BL6nA (4-15%) and less non-polarized macrophages. The M1:M2 average ratio was 1:8 for group A and 1:4 for B. Our results demonstrate different tumor progression and intratumoral macrophage populations among mice from the same substrain. Data obtained in this study shows the relevance of animal source renewal for better control of murine cancer model variables.

How CRISPR Is Revolutionizing the Generation of New Models for Cancer Research

Cancers arise through acquisition of mutations in genes that regulate core biological processes like cell proliferation and cell death. Decades of cancer research have led to the identification of genes and mutations causally involved in disease development and evolution, yet defining their precise function across different cancer types and how they influence therapy responses has been challenging. Mouse models have helped define the in vivo function of cancer-associated alterations, and genome-editing approaches using CRISPR have dramatically accelerated the pace at which these models are developed and studied. Here, we highlight how CRISPR technologies have impacted the development and use of mouse models for cancer research and discuss the many ways in which these rapidly evolving platforms will continue to transform our understanding of this disease.

Multi-scale in vivo imaging of tumour development using a germline conditional triple-reporter system

Imaging reporter genes are indispensable for visualising biological processes in living subjects, particularly in cancer research where they have been used to observe tumour development, cancer cell dissemination, and treatment response. Engineering reporter genes into the germline frequently involves single imaging modality reporters operating over limited spatial scales. To address these limitations, we developed an inducible triple-reporter mouse model (Rosa26LSL - NRL) that integrates reporters for complementary imaging modalities, flfluorescence, bioluminescence and positron emission tomography (PET), along with inducible Cre-lox functionality for precise spatiotemporal control of reporter expression. We demonstrated robust reporter inducibility across various tissues in the Rosa26LSL - NRL mouse, facilitating effective tracking and characterisation of tumours in liver and lung cancer mouse models. We precisely pinpointed tumour location using multimodal whole-body imaging which guided in situ lung microscopy to visualise cell-cell interactions within the tumour microenvironment. The triple-reporter system establishes a robust new platform technology for multi-scale investigation of biological processes within whole animals, enabling tissue-specific and sensitive cell tracking, spanning from the whole-body to cellular scales.

Establishment of a murine model of breast cancer expressing human epidermal growth factor receptor 2 (4T1-HER2)

AIM

Although people with HER2-positive breast cancer benefit from approved HER2-targeted therapy, acquiring resistance to the therapies occurs. Animal models can play a part in gaining a deep understanding of such a process and addressing questions concerning developing and improving immunotherapy approaches.

MATERIALS AND METHODS

To develop such a model, we transfected murine 4T1 cells with the pCMV6-Neo-HER2 construct and evaluated HER2 expression and its effects on the established cell line behavior in vitro and in vivo.

RESULTS

Data illustrated that human HER2 protein was expressed on isolated 4T1-HER2 clones in vitro and in vivo. Except for proliferation over 48 hours, such expression did not change 4T1-HER2 characteristics compared to 4T1 in vitro. Notwithstanding the reduction in proliferation, the rate of tumorigenicity was 90% in challenged mice and Herceptin therapy significantly decreased tumors' growth and metastasis compared to the control group.

CONCLUSION

We describe a murine model for HER2-positive breast cancer not only helping shed light on the mechanisms by which the tumor evades antitumor immunity but also playing a key role in making breast cancer more sensitive to novel immunotherapy modalities.

Advances in Making Cancer Mouse Models More Accessible and Informative through Non-Germline Genetic Engineering

Genetically engineered mouse models (GEMMs) allow for modeling of spontaneous tumorigenesis within its native microenvironment in mice and have provided invaluable insights into mechanisms of tumorigenesis and therapeutic strategies to treat human disease. However, as their generation requires germline manipulation and extensive animal breeding that is time-, labor-, and cost-intensive, traditional GEMMs are not accessible to most researchers, and fail to model the full breadth of cancer-associated genetic alterations and therapeutic targets. Recent advances in genome-editing technologies and their implementation in somatic tissues of mice have ushered in a new class of mouse models: non-germline GEMMs (nGEMMs). nGEMM approaches can be leveraged to generate somatic tumors de novo harboring virtually any individual or group of genetic alterations found in human cancer in a mouse through simple procedures that do not require breeding, greatly increasing the accessibility and speed and scale on which GEMMs can be produced. Here we describe the technologies and delivery systems used to create nGEMMs and highlight new biological insights derived from these models that have rapidly informed functional cancer genomics, precision medicine, and immune oncology.

Gender Difference in DNA Damage Induced by the Environmental Carcinogen Dibenzo[def,p]chrysene Individually and in Combination with Mouse Papillomavirus Infection in the Mouse Oral Cavity

Tobacco smoking and human papillomavirus infection are established etiological agents in the development of head and neck squamous cell carcinoma (HNSCC). The incidence and mortality of HNSCC are higher in men than women. To provide biochemical basis for sex differences, we tested the hypothesis that carcinogen treatment using dibenzo[def,p]chrysene, which is an environmental pollutant and tobacco smoke constituent, in the absence or presence of the mouse papillomavirus infection results in significantly higher levels of DNA damage in the oral cavity in male than in female mice. However, the results of the present investigation do not support our hypothesis since we found that females were more susceptible to carcinogen-induced covalent DNA damage than males independent of the viral infection. Since DNA damage represents only a single-step in the carcinogenesis process, additional factors may contribute to sex differences in humans.

Applications of Innovation Technologies for Personalized Cancer Medicine: Stem Cells and Gene-Editing Tools

Personalized medicine is a new approach toward safer and even cheaper treatments with minimal side effects and toxicity. Planning a therapy based on individual properties causes an effective result in a patient's treatment, especially in a complex disease such as cancer. The benefits of personalized medicine include not only early diagnosis with high accuracy but also a more appropriate and effective therapeutic approach based on the unique clinical, genetic, and epigenetic features and biomarker profiles of a specific patient's disease. In order to achieve personalized cancer therapy, understanding cancer biology plays an important role. One of the crucial applications of personalized medicine that has gained consideration more recently due to its capability in developing disease therapy is related to the field of stem cells. We review various applications of pluripotent, somatic, and cancer stem cells in personalized medicine, including targeted cancer therapy, cancer modeling, diagnostics, and drug screening. CRISPR-Cas gene-editing technology is then discussed as a state-of-the-art biotechnological advance with substantial impacts on medical and therapeutic applications. As part of this section, the role of CRISPR-Cas genome editing in recent cancer studies is reviewed as a further example of personalized medicine application.

Clinical insights into small cell lung cancer: Tumor heterogeneity, diagnosis, therapy, and future directions

Small cell lung cancer (SCLC) is characterized by rapid growth and high metastatic capacity. It has strong epidemiologic and biologic links to tobacco carcinogens. Although the majority of SCLCs exhibit neuroendocrine features, an important subset of tumors lacks these properties. Genomic profiling of SCLC reveals genetic instability, almost universal inactivation of the tumor suppressor genes TP53 and RB1, and a high mutation burden. Because of early metastasis, only a small fraction of patients are amenable to curative-intent lung resection, and these individuals require adjuvant platinum-etoposide chemotherapy. Therefore, the vast majority of patients are currently being treated with chemoradiation with or without immunotherapy. In patients with disease confined to the chest, standard therapy includes thoracic radiotherapy and concurrent platinum-etoposide chemotherapy. Patients with metastatic (extensive-stage) disease are treated with a combination of platinum-etoposide chemotherapy plus immunotherapy with an anti-programmed death-ligand 1 monoclonal antibody. Although SCLC is initially very responsive to platinum-based chemotherapy, these responses are transient because of the development of drug resistance. In recent years, the authors have witnessed an accelerating pace of biologic insights into the disease, leading to the redefinition of the SCLC classification scheme. This emerging knowledge of SCLC molecular subtypes has the potential to define unique therapeutic vulnerabilities. Synthesizing these new discoveries with the current knowledge of SCLC biology and clinical management may lead to unprecedented advances in SCLC patient care. Here, the authors present an overview of multimodal clinical approaches in SCLC, with a special focus on illuminating how recent advancements in SCLC research could accelerate clinical development.

A Mouse-Specific Model to Detect Genes under Selection in Tumors

The mouse is a widely used model organism in cancer research. However, no computational methods exist to identify cancer driver genes in mice due to a lack of labeled training data. To address this knowledge gap, we adapted the GUST (Genes Under Selection in Tumors) model, originally trained on human exomes, to mouse exomes via transfer learning. The resulting tool, called GUST-mouse, can estimate long-term and short-term evolutionary selection in mouse tumors, and distinguish between oncogenes, tumor suppressor genes, and passenger genes using high-throughput sequencing data. We applied GUST-mouse to analyze 65 exomes of mouse primary breast cancer models and 17 exomes of mouse leukemia models. Comparing the predictions between cancer types and between human and mouse tumors revealed common and unique driver genes. The GUST-mouse method is available as an open-source R package on github.

Is Osteopontin a Good Marker for Bone Metastasis in Canine Mammary Gland Tumor and Prostate Cancer?

Osteopontin (OPN) is a protein synthesized by a large number of cells, and its overexpression has been associated with the development and prognosis of cancer. OPN overexpression has been claimed to be a marker for the development of bone metastasis in human cancers, but no prior research has investigated the association between OPN expression and the metastasis of canine mammary gland tumors (MGTs) and prostate cancer (PC). Therefore, we investigated OPN expression in MGTs and PC samples from 50 canine patients with or without metastasis (bone vs. other sites). Higher OPN expression was detected in primary tumor samples from animals with bone metastasis than in those without bone involvement (p = 0.0321). In MGT samples, a significantly lower survival rate was observed in patients with higher OPN expression (p = 0.0171). In animals with PC, there was a strong trend toward lower survival in animals with positive OPN expression; however, this trend was not statistically significant (p = 0.0779). From these findings, it can be concluded that OPN may be a promising target for future MGTs and PC studies because of its role in enhancing cell invasion and metastasis.

Circadian disruption does not alter tumorigenesis in a mouse model of lymphoma

Background: Disruption of natural light cycles, as experienced by shift workers, is linked to enhanced cancer incidence. Several mouse models of cancer develop more severe disease when exposed to irregular light/dark cycles, supporting the connection between circadian disruption and increased cancer risk. Cryptochrome 2 (CRY2), a repressive component of the molecular circadian clock, facilitates turnover of the oncoprotein c-MYC, one mechanism that may link the molecular clock to tumorigenesis. In Eμ-MYC mice, which express transgenic c-MYC in B cells and develop aggressive lymphomas and leukemia, global Cry2 deletion reduces survival and enhances tumor formation. Lighting conditions that mimic the disruption experienced by shift workers dampen Cry2 transcripts in peripheral tissues of C57BL/6J mice. Although it is milder than homozygous deletion of Cry2, we hypothesized that reduced Cry2 rhythmicity could alter MYC protein accumulation and contribute to enhanced cancer risk caused by circadian disruption. We tested this hypothesis in MYC-driven lymphoma. Methods: We housed Eμ-MYC mice in light-tight boxes set to either control (continuous cycles of 12-hours of light followed by 12-hours of dark, LD12:12) or chronic jetlag (eight-hour light phase advances every two to three days, CJL) lighting conditions and assessed the impact of disrupted light cycles on survival and tumor formation in Eμ-MYC mice. Results: Environmental disruption of circadian rhythms did not alter tumor location, tumor growth, or survival in Eμ-MYC mice. Conclusions: Dampened rhythms of Cry2 following disruption of circadian light exposures is milder than deletion of Cry2. The lack of phenotype caused by altered circadian gene expression in contrast to enhanced tumorigenesis caused by homozygous deletion of Cry2 suggests that CRY2 dosage impacts this model. Importantly, these findings indicate that increased cancer risk associated with circadian disruption arises from one or more mechanisms that are not recapitulated here, and may be different in distinct tumor types.

An overview of mouse models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has become a severe burden on global health due to its high morbidity and mortality rates. However, effective treatments for HCC are limited. The lack of suitable preclinical models may contribute to a major failure of drug development for HCC. Here, we overview several well-established mouse models of HCC, including genetically engineered mice, chemically-induced models, implantation models, and humanized mice. Immunotherapy studies of HCC have been a hot topic. Therefore, we will introduce the application of mouse models of HCC in immunotherapy. This is followed by a discussion of some other models of HCC-related liver diseases, including non-alcoholic fatty liver disease (NAFLD), hepatitis B and C virus infection, and liver fibrosis and cirrhosis. Together these provide researchers with a current overview of the mouse models of HCC and assist in the application of appropriate models for their research.

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.

Mechanical confinement promotes heat resistance of hepatocellular carcinoma via SP1/IL4I1/AHR axis

Mechanical stress can modulate the fate of cells in both physiological and extreme conditions. Recurrence of tumors after thermal ablation, a radical therapy for many cancers, indicates that some tumor cells can endure temperatures far beyond physiological ones. This unusual heat resistance with unknown mechanisms remains a key obstacle to fully realizing the clinical potential of thermal ablation. By developing a 3D bioprinting-based thermal ablation system, we demonstrate that hepatocellular carcinoma (HCC) cells in this 3D model exhibit enhanced heat resistance as compared with cells on plates. Mechanistically, the activation of transcription factor SP1 under mechanical confinement enhances the transcription of Interleukin-4-Induced-1, which catalyzes tryptophan metabolites to activate the aryl hydrocarbon receptor (AHR), leading to heat resistance. Encouragingly, the AHR inhibitor prevents HCC recurrence after thermal ablation. These findings reveal a previously unknown role of mechanical confinement in heat resistance and provide a rationale for AHR inhibitors as neoadjuvant therapy.

Mechanical factors driving cancer progression

A fundamental step of tumor metastasis is tumor cell migration away from the primary tumor site. One mode of migration that is essential but still understudied is collective invasion, the process by which clusters of cells move in a coordinated fashion. In recent years, there has been growing interest to understand factors regulating collective invasion, with increasing number of studies investigating the biomechanical regulation of collective invasion. In this review we discuss the dynamic relationship between tumor microenvironment cues and cell response by first covering mechanical factors in the microenvironment and second, discussing the mechanosensing pathways utilized by cells in collective clusters to dynamically respond to mechanical matrix cues. Finally, we discuss model systems that have been developed which have increased our understanding of the mechanical factors contributing to tumor progression.

PRECLINICAL MODELS OF LIVER CÂNCER

•In this review, we described different murine models of carcinogenesis: classic models, new transgenic and combined models, that reproduce the key points for HCC and CCA genesis allowing a better understanding of its genetic physiopathological, and environmental abnormalities. •Each model has its advantages, disadvantages, similarities, and differences with the corresponding human disease and should be chosen according to the specificity of the study. Ultimately, those models can also be used for testing new anticancer therapeutic approaches. •Cholangiocarcinoma has been highlighted, with an increase in prevalence. This review has an important role in understanding the pathophysiology and the development of new drugs. Background - This manuscript provides an overview of liver carcinogenesis in murine models of hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). Objective - A review through MEDLINE and EMBASE was performed to assess articles until August 2022.Methods - Search was conducted of the entire electronic databases and the keywords used was HCC, CCA, carcinogenesis, animal models and liver. Articles exclusion was based on the lack of close relation to the subject. Carcinogenesis models of HCC include HCC induced by senescence in transgenic animals, HCC diet-induced, HCC induced by chemotoxicagents, xenograft, oncogenes, and HCC in transgenic animals inoculated with B and C virus. The models of CCA include the use of dimethylnitrosamine (DMN), diethylnitrosamine (DEN), thioacetamide (TAA), and carbon tetrachloride (CCl4). CCA murine models may also be induced by: CCA cells, genetic manipulation, Smad4, PTEN and p53 knockout, xenograft, and DEN-left median bile duct ligation. Results - In this review, we described different murine models of carcinogenesis that reproduce the key points for HCC and CCA genesis allowing a better understanding of its genetic, physiopathological, and environmental abnormalities. Conclusion - Each model has its advantages, disadvantages, similarities, and differences with the corresponding human disease and should be chosen according to the specificity of the study. Ultimately, those models can also be used for testing new anticancer therapeutic approaches.

Zebrafish imaging reveals hidden oncogenic-normal cell communication during primary tumorigenesis

Oncogenic mutations drive tumorigenesis, and single cells with oncogenic mutations act as the tumor seeds that gradually evolve into fully transformed tumors. However, oncogenic cell behavior and communication with neighboring cells during primary tumorigenesis remain poorly understood. We used the zebrafish, a small vertebrate model suitable for in vivo cell biology, to address these issues. We describe the cooperative and competitive communication between oncogenic cells and neighboring cells, as revealed by our recent zebrafish imaging studies. Newly generated oncogenic cells are actively eliminated by neighboring cells in healthy epithelia, whereas oncogenic cells cooperate with their neighbors to prime tumorigenesis in unhealthy epithelia via additional mutations or inflammation. In addition, we discuss the potential of zebrafish in vivo imaging to determine the initial steps of human tumorigenesis.Key words: zebrafish, imaging, cell-cell communication, cell competition, EDAC, senescence, primary tumorigenesis.

Aging - what it is and how to measure it

The current understanding of the biology of aging is largely based on research aimed at identifying factors that influence lifespan. However, lifespan as a sole proxy measure of aging has limitations because it can be influenced by specific pathologies (not generalized physiological deterioration in old age). Hence, there is a great need to discuss and design experimental approaches that are well-suited for studies targeting the biology of aging, rather than the biology of specific pathologies that restrict the lifespan of a given species. For this purpose, we here review various perspectives on aging, discuss agreement and disagreement among researchers on the definition of aging, and show that while slightly different aspects are emphasized, a widely accepted feature, shared across many definitions, is that aging is accompanied by phenotypic changes that occur in a population over the course of an average lifespan. We then discuss experimental approaches that are in line with these considerations, including multidimensional analytical frameworks as well as designs that facilitate the proper assessment of intervention effects on aging rate. The proposed framework can guide discovery approaches to aging mechanisms in all key model organisms (e.g., mouse, fish models, D. melanogaster, C. elegans) as well as in humans.

Enhancing the Anti-tumor Potency of a Novel Siglec-15 Antibody by Engineering its Fc-mediated Effector Functions

Siglec-15, an inhibitory immune checkpoint, is an emerging target in cancer immunotherapy. Blocking the function of Siglec-15 is an excellent strategy for cancer treatment and antibody blockade has been used to target Siglec-15. However, whether Fc-mediated effector functions contribute to the therapeutic effect of antibodies remains unclear. Herein, we generated a monoclonal antibody, 1-15D1, which had a high binding affinity with Siglec-15 and strongly activated T-cell immune response in vitro. Subsequently, the Fc-mediated effector functions of 1-15D1 were explored in a Siglec-15 humanized mouse model, and further improvement in antitumor efficacy was observed in the mouse IgG2a isotype group. Thus, we demonstrate that the antitumor effects of 1-15D1 were mediated via multiple factors. In addition to the T-cell immune response, 2 novel mechanisms were explored, including the internalization of the cell surface Siglec-15 and Fc-mediated effector functions. In conclusion, our studies not only provide a potential agent for the improvement of cancer immunotherapy but also suggest that a specific role of Fc-mediated immune regulation may improve the therapeutic potency of Siglec-15 monoclonal antibody.

Advances in the Application of Preclinical Models in Photodynamic Therapy for Tumor: A Narrative Review

Photodynamic therapy (PDT) is a non-invasive laser light local treatment that has been utilized in the management of a wide variety of solid tumors. Moreover, the evaluation of efficacy, adverse reactions, the development of new photosensitizers and the latest therapeutic regimens are inseparable from the preliminary exploration in preclinical studies. Therefore, our aim was to better comprehend the characteristics and limitations of these models and to provide a reference for related research.

METHODS

We searched the databases, including PubMed, Web of Science and Scopus for the past 25 years of original research articles on the feasibility of PDT in tumor treatment based on preclinical experiments and animal models. We provided insights into inclusion and exclusion criteria and ultimately selected 40 articles for data synthesis.

RESULTS

After summarizing and comparing the methods and results of these studies, the experimental model selection map was drawn. There are 7 main preclinical models, which are used for different research objectives according to their characteristics.

CONCLUSIONS

Based on this narrative review, preclinical experimental models are crucial to the development and promotion of PDT for tumors. The traditional animal models have some limitations, and the emergence of organoids may be a promising new insight.

Targeting the "hallmarks of aging" to slow aging and treat age-related disease: fact or fiction?

Aging is a major risk factor for a number of chronic diseases, including neurodegenerative and cerebrovascular disorders. Aging processes have therefore been discussed as potential targets for the development of novel and broadly effective preventatives or therapeutics for age-related diseases, including those affecting the brain. Mechanisms thought to contribute to aging have been summarized under the term the "hallmarks of aging" and include a loss of proteostasis, mitochondrial dysfunction, altered nutrient sensing, telomere attrition, genomic instability, cellular senescence, stem cell exhaustion, epigenetic alterations and altered intercellular communication. We here examine key claims about the "hallmarks of aging". Our analysis reveals important weaknesses that preclude strong and definitive conclusions concerning a possible role of these processes in shaping organismal aging rate. Significant ambiguity arises from the overreliance on lifespan as a proxy marker for aging, the use of models with unclear relevance for organismal aging, and the use of study designs that do not allow to properly estimate intervention effects on aging rate. We also discuss future research directions that should be taken to clarify if and to what extent putative aging regulators do in fact interact with aging. These include multidimensional analytical frameworks as well as designs that facilitate the proper assessment of intervention effects on aging rate.

Modeling leukemia with zebrafish (Danio rerio): Towards precision medicine

Leukemia is a type of blood cancer characterized by high genetic heterogeneity and fatality. While chemotherapy remains the primary form of treatment for leukemia, its effectiveness was profoundly diminished by the genetic heterogeneity and cytogenetic abnormalities of leukemic cells. Therefore, there is an unmet need to develop precision medicine for leukemia with distinct genetic backgrounds. Zebrafish (Danio rerio), a freshwater fish with exceptional feasibility in genome editing, is a powerful tool for rapid human cancer modeling. In the past decades, zebrafish have been adopted in modeling human leukemia, exploring the molecular mechanisms of underlying genetic abnormalities, and discovering novel therapeutic agents. Although many recurrent mutations of leukemia have been modeled in zebrafish for pathological study and drug discovery, its great potential in leukemia modeling was not yet fully exploited, particularly in precision medicine. In this review, we evaluated the current zebrafish models of leukemia/pre-leukemia and genetic techniques and discussed the potential of zebrafish models with novel techniques, which may contribute to the development of zebrafish as a disease model for precision medicine in treating leukemia.

Development of extrahepatic bile ducts and mechanisms of tumorigenesis: Lessons from mouse models

The biliary system is a highly branched tubular network consisting of intrahepatic bile ducts (IHBDs) and extrahepatic bile ducts (EHBDs). IHBDs are derived from hepatic progenitor cells, while EHBDs originate directly from the endoderm through a separate branching morphogenetic process. Traits that are important for cancer are often found to overlap in developmental and other processes. Therefore, it has been suggested that intrahepatic cholangiocarcinomas (iCCAs) and extrahepatic cholangiocarcinomas (eCCAs) have different developmental mechanisms. While much evidence is being gathered on the mechanism of iCCAs, the evidence for eCCA is still very limited. The main reason for this is that there are very few appropriate animal models for eCCA. We can gain important insights from these animal models, particularly genetically engineered mouse models (GEMMs). GEMMs are immunocompetent and mimic human CCA subtypes with a specific mutational pattern, allowing the development of precancerous lesions, that is, biliary intraepithelial neoplasia (BilIN) and intraductal papillary neoplasm of the bile duct (IPNB). This review provides a summary of the pathogenesis and mechanisms of eCCA that can be revealed by GEMMs. Furthermore, we discuss several clinical questions, such as whether BilIN and IPNB really become malignant, whether the peribiliary gland is the origin of eCCAs, and others.

Molecular pathogenesis, targeted therapies, and future perspectives for gastric cancer

Gastric cancer is a major source of global cancer mortality with limited treatment options and poor patient survival. As our molecular understanding of gastric cancer improves, we are now beginning to recognize that these cancers are a heterogeneous group of diseases with incredibly unique pathogeneses and active oncogenic pathways. It is this molecular diversity and oftentimes lack of common oncogenic driver mutations that bestow the poor treatment responses that oncologists often face when treating gastric cancer. In this review, we will examine the treatments for gastric cancer including up-to-date molecularly targeted therapies and immunotherapies. We will then review the molecular subtypes of gastric cancer to highlight the diversity seen in this disease. We will then shift our discussion to basic science and gastric cancer mouse models as tools to study gastric cancer molecular heterogeneity. Furthermore, we will elaborate on a molecular process termed paligenosis and the cyclical hit model as key events during gastric cancer initiation that impart nondividing mature differentiated cells the ability to re-enter the cell cycle and accumulate disparate genomic mutations during years of chronic inflammation and injury. As our basic science understanding of gastric cancer advances, so too must our translational and clinical efforts. We will end with a discussion regarding single-cell molecular analyses and cancer organoid technologies as future translational avenues to advance our understanding of gastric cancer heterogeneity and to design precision-based gastric cancer treatments. Elucidation of interpatient and intratumor heterogeneity is the only way to advance future cancer prevention, diagnoses and treatment.

The cell-line-derived subcutaneous tumor model in preclinical cancer research

Tumor-bearing experimental animals are essential for preclinical cancer drug development. A broad range of tumor models is available, with the simplest and most widely used involving a tumor of mouse or human origin growing beneath the skin of a mouse: the subcutaneous tumor model. Here, we outline the different types of in vivo tumor model, including some of their advantages and disadvantages and how they fit into the drug-development process. We then describe in more detail the subcutaneous tumor model and key steps needed to establish it in the laboratory, namely: choosing the mouse strain and tumor cells; cell culture, preparation and injection of tumor cells; determining tumor volume; mouse welfare; and an appropriate experimental end point. The protocol leads to subcutaneous tumor growth usually within 1-3 weeks of cell injection and is suitable for those with experience in tissue culture and mouse experimentation.

Lineage tracing reveals the phylodynamics, plasticity, and paths of tumor evolution

Tumor evolution is driven by the progressive acquisition of genetic and epigenetic alterations that enable uncontrolled growth and expansion to neighboring and distal tissues. The study of phylogenetic relationships between cancer cells provides key insights into these processes. Here, we introduced an evolving lineage-tracing system with a single-cell RNA-seq readout into a mouse model of Kras;Trp53(KP)-driven lung adenocarcinoma and tracked tumor evolution from single-transformed cells to metastatic tumors at unprecedented resolution. We found that the loss of the initial, stable alveolar-type2-like state was accompanied by a transient increase in plasticity. This was followed by the adoption of distinct transcriptional programs that enable rapid expansion and, ultimately, clonal sweep of stable subclones capable of metastasizing. Finally, tumors develop through stereotypical evolutionary trajectories, and perturbing additional tumor suppressors accelerates progression by creating novel trajectories. Our study elucidates the hierarchical nature of tumor evolution and, more broadly, enables in-depth studies of tumor progression.

A combined antitumor strategy of separately transduced mesenchymal stem cells with soluble TRAIL and IFNβ produces a synergistic activity in the reduction of lymphoma and mice survival enlargement

As the understanding of cancer grows, new therapies have been proposed to improve the well-known limitations of current therapies, whose efficiency relies mostly on early detection, surgery and chemotherapy. Mesenchymal stem cells (MSCs) have been introduced as a promissory and effective therapy. This fact is due to several useful features of MSCs, such as their accessibility and easy culture and expansion in vitro, and their remarkable ability for ‘homing’ towards tumors, allowing MSCs to exert their anticancer effects directly into tumors. Additionally, MSCs offer the practicability of being genetically engineered to carry anticancer genes, increasing their specificity and efficacy for fighting tumors. In the present study, the antitumoral efficacy and post-implant survival of mice bearing lymphomas implanted intratumorally were determined using mouse bone marrow-derived (BM)-MSCs transduced with soluble TRAIL (sTRAIL), full length TRAIL (flTRAIL), or interferon β (IFNβ), naïve BM-MSCs, or combinations of these. The percentage of surviving mice was determined once all not-implanted mice succumbed. It was found that the percentage of surviving mice implanted with the combination of MSCs-sTRAIL and MSCs-IFN-β was 62.5%. Lymphoma model achieved 100% fatality in the non-treated group by day 41. On the other hand, the percentage of surviving mice implanted with MSCs-sTRAIL was 50% and with MSCs-INFβ 25%. All the aforementioned differences were statistically significant (P<0.05). In conclusion, all implants exhibited tumor size reduction, growth delay, or apparent tumor clearance. MSCs proved to be effective anti-lymphoma agents; additionally, the combination of soluble TRAIL and IFN-β resulted in the most effective antitumor and life enlarging treatment, showing an additive antitumoral effect compared with individual treatments.

Novel Mouse Models for Cancer Immunology

Mouse models for the study of cancer immunology provide excellent systems in which to test biological mechanisms of the immune response against cancer. Historically, these models have been designed to have different strengths based on the current major research questions at the time. As such, many mouse models of immunology used today were not originally developed to study questions currently plaguing the relatively new field of cancer immunology, but instead have been adapted for such purposes. In this review, we discuss various mouse model of cancer immunology in a historical context as a means to provide a fuller perspective of each model's strengths. From this outlook, we discuss the current state of the art and strategies for tackling future modeling challenges.

Two Beats One: Osteosarcoma Therapy with Light-Activated and Chemo-Releasing Keratin Nanoformulation in a Preclinical Mouse Model

Osteosarcoma treatment is moving towards more effective combination therapies. Nevertheless, these approaches present distinctive challenges that can complicate the clinical translation, such as increased toxicity and multi-drug resistance. Drug co-encapsulation within a nanoparticle formulation can overcome these challenges and improve the therapeutic index. We previously synthetized keratin nanoparticles functionalized with Chlorin-e6 (Ce6) and paclitaxel (PTX) to combine photo (PDT) and chemotherapy (PTX) regimens, and the inhibition of osteosarcoma cells growth in vitro was demonstrated. In the current study, we generated an orthotopic osteosarcoma murine model for the preclinical evaluation of our combination therapy. To achieve maximum reproducibility, we systematically established key parameters, such as the number of cells to generate the tumor, the nanoparticles dose, the design of the light-delivery device, the treatment schedule, and the irradiation settings. A 60% engrafting rate was obtained using 10 million OS cells inoculated intratibial, with the tumor model recapitulating the histological hallmarks of the human counterpart. By scheduling the treatment as two cycles of injections, a 32% tumor reduction was obtained with PTX mono-therapy and a 78% reduction with the combined PTX-PDT therapy. Our findings provide the in vivo proof of concept for the subsequent clinical development of a combination therapy to fight osteosarcoma.

Ayurveda-based Botanicals as Therapeutic Adjuvants in Paclitaxel-induced Myelosuppression

Chemotherapy-induced myelosuppression is one of the major challenges in cancer treatment. Ayurveda-based immunomodulatory botanicals Asparagus racemosus Willd (AR/Shatavari) and Withania somnifera (L.). Dunal (WS/Ashwagandha) have potential role to manage myelosuppression. We have developed a method to study the effects of AR and WS as therapeutic adjuvants to counter paclitaxel (PTX)-induced myelosuppression. Sixty female BALB/c mice were divided into six groups—vehicle control (VC), PTX alone, PTX with aqueous and hydroalcoholic extracts of AR (ARA, ARH) and WS (WSA, WSH). The myelosuppression was induced in mice by intraperitoneal administration of PTX at 25 mg/kg dose for three consecutive days. The extracts were orally administered with a dose of 100 mg/kg for 15 days prior to the induction with PTX administration. The mice were observed daily for morbidity parameters and were bled from retro-orbital plexus after 2 days of PTX dosing. The morbidity parameters simulate clinical adverse effects of PTX that include activity (extreme tiredness due to fatigue), behavior (numbness and weakness due to peripheral neuropathy), body posture (pain in muscles and joints), fur aspect and huddling (hair loss). The collected samples were used for blood cell count analysis and cytokine profiling using Bio-Plex assay. The PTX alone group showed a reduction in total leukocyte and neutrophil counts (4,800 ± 606; 893 ± 82) when compared with a VC group (9,183 ± 1,043; 1,612 ± 100) respectively. Pre-administration of ARA, ARH, WSA, and WSH extracts normalized leukocyte counts (10,000 ± 707; 9,166 ± 1,076; 10,333 ± 1,189; 9,066 ± 697) and neutrophil counts (1,482 ± 61; 1,251 ± 71; 1,467 ± 121; 1,219 ± 134) respectively. Additionally, higher morbidity score in PTX group (7.4 ± 0.7) was significantly restricted by ARA (4.8 ± 1.1), ARH (5.1 ± 0.6), WSA (4.5 ± 0.7), and WSH (5 ± 0.8). (Data represented in mean ± SD). The extracts also significantly modulated 20 cytokines to evade PTX-induced leukopenia, neutropenia, and morbidity. The AR and WS extracts significantly prevented PTX-induced myelosuppression (p < 0.0001) and morbidity signs (p < 0.05) by modulating associated cytokines. The results indicate AR and WS as therapeutic adjuvants in cancer management.

Isolation of TCR genes with tumor-killing activity from tumor-infiltrating and circulating lymphocytes in a tumor rejection cynomolgus macaque model

To develop effective adoptive cell transfer therapy using T cell receptor (TCR)-engineered T cells, it is critical to isolate tumor-reactive TCRs that have potent anti-tumor activity. In humans, tumor-infiltrating lymphocytes (TILs) have been reported to contain CD8⁺PD-1⁺ T cells that express tumor-reactive TCRs. Characterization of tumor reactivity of TILs from non-human primate tumors could improve anti-tumor activity of TCR-engineered T cells in preclinical research. In this study, we sought to isolate TCR genes from CD8⁺PD-1⁺ T cells among TILs in a cynomolgus macaque model of tumor transplantation in which the tumors were infiltrated with CD8⁺ T cells and were eventually rejected. We analyzed the repertoire of TCRα and β pairs obtained from single CD8⁺PD-1⁺ T cells in TILs and circulating lymphocytes and identified multiple TCR pairs with high frequency, suggesting that T cells expressing these recurrent TCRs were clonally expanded in response to tumor cells. We further showed that the recurrent TCRs exhibited cytotoxic activity to tumor cells in vitro and potent anti-tumor activity in mice transplanted with tumor cells. These results imply that this tumor transplantation macaque model recapitulates key features of human TILs and can serve as a platform toward preclinical studies of non-human primate tumor models.

Mechanisms of cancellation by pain of genetically determined inhibition of a malignant tumor growth in experiment

Aims are to study the nature of the processes of carcinogenesis of experimental B16/F10 melanoma in uPA gene knockout mice modified by chronic neurogenic pain and investigate some electrophysiological mechanisms of melanoma development. Materials and methods. We used 48 C57BL/6-PlautmI. IBug-ThisPlau6FDhu/GFDhu mice of both genders with urokinase gene knockout and 102 C57BL/6 mice of both genders with the normal genotype. Chronic neurogenic pain (CNP) was produced due to bilateral ligation of the sciatic nerve. Against the above background, all animals were transplanted with B16/F10 melanoma. To study the mechanism of CNP, studies of the intracellular electrophysiological activity of neurons of the central nervous system of the snail Helix pomatia in the body in vivo were carried out. CNP was reproduced by dosed pressing of four main nerves with Fresnel hairs that with time turned into increasing pain. Membrane potential (MP), action potential (AP) and firing rate (FR) parameters of intracellular bio-potentials of the command neuron RPaG3, continuously recorded using an ultrathin glass microelectrode for 4-5 days, were analyzed. Results. It was detected that an activation of cancerogenesis during the modification of the progression of experimental B16/ F10 melanoma in C57BL/6-PlautmI.IBug-ThisPlau6FDhu/GFDhu mice with uPA gene knockout using CNP is accompanied by a 2-fold acceleration in the time of tumor production, stimulation of the growth of the primary tumor nodes from 1.05±0.08 cm3 to 9.50±0.98 cm3 (p<0.001) and multiple metastasizing to the lungs, a reduction in the life span from 34.67±0.67 to 21.33±2.19 days (p<0.001) <0.05) in the genetically modified mice, by changing some gender-specific characteristics of the progression of the malignant process. The neuropathic nature of pain resulting from command neuron compression or ligation of the sciatic nerves is essentially identical to the implementation of genetic programs responsible for the control of life and death, reproducing events in carcinogenesis with the progression of a malignant tumor. Conclusion. The initiation and chronization of pain at the local level of the nervous system can lead to generalization of the pain syndrome and contribute to the cancellation of genetically predetermined programs of carcinogenesis.

Downregulation of CYP39A1 Serves as a Novel Biomarker in Hepatocellular Carcinoma with Worse Clinical Outcome

Background

CYP39A1 is a poorly characterized metabolic enzyme that has been investigated in a few tumors. However, the role of CYP39A1 in hepatocellular carcinoma (HCC) has not yet been clarified. In this study, the expression and clinical significance of CYP39A1 in HCC were explored.

Methods

CYP39A1 protein expression was detected in Akt/c-Met-induced HCC mice and 14 paired fresh HCC samples as well as another 159 HCC and matched noncancerous tissues. Meanwhile, the mRNA expression was analyzed by GEO and TCGA analysis and validated in 14 paired fresh HCC tissues. Furthermore, the relationships between CYP39A1 expression and clinicopathologic features as well as prognosis were analyzed. HCC cell growth changes were analyzed by cell viability assays after CYP39A1 overexpression and then validated after CYP39A1 knockout by DepMap database analysis.

Results

CYP39A1 protein expression was lower expressed in HCC mouse models, and its mRNA and protein expression were also downregulated in HCC compared with noncancerous liver tissues. Higher CYP39A1 expression was associated with well differentiation. Moreover, survival analysis indicated that lower CYP39A1 expression was associated with poorer overall survival. In addition, HepG2 and SMMC-7721 cell viability were inhibited after CYP39A1 overexpression. Genome-wide CRISPR/Cas9 proliferation screening indicated that knockout of CYP39A1 could promote HCC cell growth. Likewise, p-NF-κB and Nrf2 were suppressed after CYP39A1 overexpression. It is worth mentioning that total bile acid, total bilirubin, and direct bilirubin were significantly increased in the patients with low CYP39A1 expression.

Conclusions

Downregulation of CYP39A1 is associated with HCC carcinogenesis, tumor differentiation, and poor overall survival, suggesting that CYP39A1 may serve as a tumor suppressor gene and novel biomarker for HCC patients.

Murine Models of Chronic Viral Infections and Associated Cancers

Viruses are now recognized as bona fide etiologic factors of human cancer. Carcinogenic viruses include Epstein– Barr virus (EBV), high-risk human papillomaviruses (HPVs), hepatitis B virus (HBV), hepatitis C virus (HCV), human T-cell leukemia virus type 1 (HTLV-1), human immunodeficiency virus type 1 (HIV-1, indirectly), and several candidate human cancer viruses. It is estimated that 15% of all human tumors worldwide are caused by viruses. Tumor viruses establish long-term persistent infections in humans, and cancer is an accidental side effect of viral replication strategies. Viruses are usually not complete carcinogens, supporting the concept that cancer results from the accumulation of multiple cooperating events, in which human cancer viruses display different, often opposing roles. The laboratory mouse Mus musculus is one of the best in vivo experimental systems for modeling human pathology, including viral infections and cancer. However, mice are unsusceptible to infection with the known carcinogenic viruses. Many murine models were developed to overcome this limitation and to address various aspects of virus-associated carcinogenesis, from tumors resulting from xenografts of human tissues and cells, including cancerous and virus infected, to genetically engineered mice susceptible to viral infections and associated cancer. The review considers the main existing models, analyzes their advantages and drawbacks, describes their applications, outlines the prospects of their further development.

Targeting the IGF-Axis Potentiates Immunotherapy for Pancreatic Ductal Adenocarcinoma Liver Metastases by Altering the Immunosuppressive Microenvironment

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy, resistant to chemotherapy and associated with high incidence of liver metastases and poor prognosis. Using murine models of aggressive PDAC, we show here that in mice bearing hepatic metastases, treatment with the IGF-Trap, an inhibitor of type I insulin-like growth factor receptor (IGF-IR) signaling, profoundly altered the local, immunosuppressive tumor microenvironment in the liver, curtailing the recruitment of myeloid-derived suppressor cells, reversing innate immune cell polarization and inhibiting metastatic expansion. Significantly, we found that immunotherapy with anti-PD-1 antibodies also reduced the growth of experimental PDAC liver metastases, and this effect was enhanced when combined with IGF-Trap treatment, resulting in further potentiation of a T-cell response. Our results show that a combinatorial immunotherapy based on dual targeting of the prometastatic immune microenvironment of the liver via IGF blockade, on one hand, and reversing T-cell exhaustion on the other, can provide a significant therapeutic benefit in the management of PDAC metastases.

Pharmacokinetic and Pharmacodynamic Assessment of Hydroxychloroquine in Breast Cancer

Hydroxychloroquine (HCQ) is being tested in a number of human clinical trials to determine the role of autophagy in response to standard anticancer therapies. However, HCQ pharmacodynamic (PD) responses are difficult to assess in patients, and preclinical studies in mouse models are equivocal with regard to HCQ exposure and inhibition of autophagy. Here, pharmacokinetic (PK) assessment of HCQ in non-tumor-bearing mice after intraperitoneal dosing established 60 mg/kg as the human equivalent dose of HCQ in mice. Autophagy inhibition, cell proliferation, and cell death were assessed in two-dimensional (2D) cell culture and three-dimensional tumor organoids in breast cancer. Mice challenged with breast cancer xenografts were then treated with 60 mg/kg HCQ via intraperitoneal dosing, and subsequent PK and PD responses were assessed. Although autophagic flux was significantly inhibited in cells irrespective of autophagy-dependence status, autophagy-dependent tumors had decreased cell proliferation and increased cell death at earlier time points compared with autophagy-independent tumors. Overall, this study shows that 2D cell culture, three-dimensional tumor organoids, and in vivo studies produce similar results, and in vitro studies can be used as surrogates to recapitulate in vivo antitumor responses of HCQ. SIGNIFICANCE STATEMENT: Autophagy-dependent tumors but not autophagy-independent tumors have decreased cell proliferation and increased cell death after single-agent hydroxychloroquine treatment. However, hydroxychloroquine causes decreased autophagic flux regardless of autophagy status, suggesting its clinical efficacy in the context of autophagy inhibition.

Between the Devil and the Deep Blue Sea: Non-Coding RNAs Associated with Transmissible Cancers in Tasmanian Devil, Domestic Dog and Bivalves

Currently there are nine known examples of transmissible cancers in nature. They have been observed in domestic dog, Tasmanian devil, and six bivalve species. These tumours can overcome host immune defences and spread to other members of the same species. Non-coding RNAs (ncRNAs) are known to play roles in tumorigenesis and immune system evasion. Despite their potential importance in transmissible cancers, there have been no studies on ncRNA function in this context to date. Here, we present possible applications of the CRISPR/Cas system to study the RNA biology of transmissible cancers. Specifically, we explore how ncRNAs may play a role in the immortality and immune evasion ability of these tumours.

Patient-derived xenograft culture-transplant system for investigation of human breast cancer metastasis

Metastasis is a fatal disease where research progress has been hindered by a lack of authentic experimental models. Here, we develop a 3D tumor sphere culture-transplant system that facilitates the growth and engineering of patient-derived xenograft (PDX) tumor cells for functional metastasis assays in vivo. Orthotopic transplantation and RNA sequencing (RNA-seq) analyses show that PDX tumor spheres maintain tumorigenic potential, and the molecular marker and global transcriptome signatures of native tumor cells. Tumor spheres display robust capacity for lentiviral engineering and dissemination in spontaneous and experimental metastasis assays in vivo. Inhibition of pathways previously reported to attenuate metastasis also inhibit metastasis after sphere culture, validating our approach for authentic investigations of metastasis. Finally, we demonstrate a new role for the metabolic enzyme NME1 in promoting breast cancer metastasis, providing proof-of-principle that our culture-transplant system can be used for authentic propagation and engineering of patient tumor cells for functional studies of metastasis.

Preclinical Solid Tumor Models to Study Novel Therapeutics in Brain Metastases

Metastases are the most common malignancy of the adult central nervous system and are becoming an increasingly troubling problem in oncology largely due to the lack of successful therapeutic options. The limited selection of treatments is a result of the currently poor understanding of the biological mechanisms of metastatic development, which in turn is difficult to achieve because of limited preclinical models that can accurately represent the clinical progression of metastasis. Described in this article are in vitro and in vivo model systems that are used to enhance the understanding of metastasis and to identify new therapies for the treatment of brain metastasis. © 2021 Wiley Periodicals LLC.

Decoding leader cells in collective cancer invasion

Collective cancer invasion with leader-follower organization is increasingly recognized as a predominant mechanism in the metastatic cascade. Leader cells support cancer invasion by creating invasion tracks, sensing environmental cues and coordinating with follower cells biochemically and biomechanically. With the latest developments in experimental and computational models and analysis techniques, the range of specific traits and features of leader cells reported in the literature is rapidly expanding. Yet, despite their importance, there is no consensus on how leader cells arise or their essential characteristics. In this Perspective, we propose a framework for defining the essential aspects of leader cells and provide a unifying perspective on the varying cellular and molecular programmes that are adopted by each leader cell subtype to accomplish their functions. This Perspective can lead to more effective strategies to interdict a major contributor to metastatic capability.

Consistent tumorigenesis with self-assembled hydrogels enables high-powered murine cancer studies

Preclinical cancer research is heavily dependent on allograft and xenograft models, but current approaches to tumor inoculation yield inconsistent tumor formation and growth, ultimately wasting valuable resources (e.g., animals, time, and money) and limiting experimental progress. Here we demonstrate a method for tumor inoculation using self-assembled hydrogels to reliably generate tumors with low variance in growth. The observed reduction in model variance enables smaller animal cohorts, improved effect observation and higher powered studies.

Nanoprobe-Based Magnetic Resonance Imaging of Hypoxia Predicts Responses to Radiotherapy, Immunotherapy, and Sensitizing Treatments in Pancreatic Tumors

Accurate diagnosis of tumors and predicting the therapeutic responses are highly demanded in the clinic to improve the treatment efficacy and survival rates. Since hypoxia develops in the progression of tumors and inversely correlates with prognosis and promotes resistance to radiotherapies and immunotherapies, it is a potential marker for therapeutic prediction. Therefore, effective discrimination of tumor hypoxia for predicting therapeutic outcomes is critical. Here, a magnetic resonance imaging (MRI)-based diagnosis strategy using contrast-amplifying nanoprobes that sense tumor acidosis and real-time observation of hypoxic conditions in tumors has been developed, aiming at accurate detection of pancreatic tumors and prediction of therapeutic effects. Our approach selectively probed xenograft, allograft, and transgenic spontaneous models of intractable pancreatic cancer, which lacks standardized predictive markers to identify patients who benefit most from treatments, and effectively discriminated the intratumoral hypoxia levels. By stratification of pancreatic tumors based on quantitative MR imaging of hypoxia, it enabled prediction of the responses to radiotherapy and immune checkpoint inhibitors. Moreover, the nanoprobe-based MRI could monitor hypoxia reduction by tumor normalization treatments, which permits visualizing pancreatic tumors that will respond to immune checkpoint blockade therapy, enhancing the response rate. The results demonstrate the potential of our strategy for accurate tumor diagnosis, patient stratification, and effective therapy.

Study of Longitudinal Aging in Mice: Presentation of Experimental Techniques

Aging is associated with functional and metabolic decline and is a risk factor for all noncommunicable diseases. Even though mice are routinely used for modeling human aging and aging-related conditions, no comprehensive assessment to date has been conducted on normative mouse aging. To address this gap, the Study of Longitudinal Aging in Mice (SLAM) was designed and implemented by the National Institute on Aging (NIA/NIH) as the mouse counterpart to the Baltimore Longitudinal Study of Aging (BLSA). In this manuscript, we describe the premise, study design, methodologies, and technologies currently employed in SLAM. We also discuss current and future study directions. In this large population mouse study, inbred C57BL/6J and outbred UM-HET3 mice of both sexes are longitudinally evaluated for functional, phenotypic, and biological health, and collection of biospecimens is conducted throughout their life span. Within the longitudinal cohorts, a cross-sectional arm of the study has also been implemented for the well-controlled collection of tissues to generate a biorepository. SLAM and studies stemming from SLAM seek to identify and characterize phenotypic and biological predictors of mouse aging and age-associated conditions, examine the degrees of functional and biomolecular variability that occur within inbred and genetically heterogeneous mouse populations with age, and assess whether these changes are consistent with alterations observed in human aging in BLSA. The findings from these studies will be critical for evaluating the utility of mouse models for studying different aspects of aging, both in terms of interpreting prior findings and designing and implementing future studies.

Discovery of Small Molecule Bak Activator for Lung Cancer Therapy

Rationale: Bak is a major proapoptotic Bcl2 family member and a required molecule for apoptotic cell death. High levels of endogenous Bak were observed in both small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC) cell lines. Increased Bak expression was correlated with poor prognosis of NSCLC patients, suggesting that Bak protein is an attractive target for lung cancer therapy. The BH3 domain functions as death domain and is required for Bak to initiate apoptotic cell death. Thus, the BH3 domain is attractive target for discovery of Bak agonist.

Methods: The BH3 death domain binding pocket (aa75-88) of Bak was chosen as a docking site for screening of small molecule Bak activators using the UCSF DOCK 6.1 program suite and the NCI chemical library (300,000 small molecules) database. The top 500 compounds determined to have the highest affinity for the BH3 domain were obtained from the NCI and tested for cytotoxicity for further screening. We identified a small molecule Bak activator BKA-073 as the lead compound. The binding affinity of BKA-073 with Bak protein was analyzed by isothermal titration calorimetry (ITC) assay. BKA-073-mediated Bak activation via oligomerization was analyzed by a cross-linking with Bis (maleimido) hexane (BMH). Sensitivity of BKA-073 to lung cancer cells in vitro was evaluated by dynamic BH3 profiling (DBP) and apoptotic cell death assay. The potency of BKA-073 alone or in combination with radiotherapy or Bcl2 inhibitor was evaluated in animal models.

Results: We found that BKA-073 binds Bak at BH3 domain with high affinity and selectivity. BKA-073/Bak binding promotes Bak oligomerization and mitochondrial priming that activates its proapoptotic function. BKA-073 potently suppresses tumor growth without significant normal tissue toxicity in small cell lung cancer (SCLC) and NSCLC xenografts, patient-derived xenografts, and genetically engineered mouse models of mutant KRAS-driven cancer. Bak accumulates in radioresistant lung cancer cells and BKA-073 reverses radioresistance. Combination of BKA-073 with Bcl-2 inhibitor venetoclax exhibits strong synergy against lung cancer in vivo.

Conclusions: Development of small molecule Bak activator may provide a new class of anticancer agents to treat lung cancer.

Translating complexity and heterogeneity of pancreatic tumor: 3D in vitro to in vivo models

Pancreatic ductal adenocarcinoma (PDAC) is an extremely aggressive type of cancer with an overall survival rate of less than 7-8%, emphasizing the need for novel effective therapeutics against PDAC. However only a fraction of therapeutics which seemed promising in the laboratory environment will eventually reach the clinic. One of the main reasons behind this low success rate is the complex tumor microenvironment (TME) of PDAC, a highly fibrotic and dense stroma surrounding tumor cells, which supports tumor progression as well as increases the resistance against the treatment. In particular, the growing understanding of the PDAC TME points out a different challenge in the development of efficient therapeutics - a lack of biologically relevant in vitro and in vivo models that resemble the complexity and heterogeneity of PDAC observed in patients. The purpose and scope of this review is to provide an overview of the recent developments in different in vitro and in vivo models, which aim to recapitulate the complexity of PDAC in a laboratory environment, as well to describe how 3D in vitro models can be integrated into drug development pipelines that are already including sophisticated in vivo models. Hereby a special focus will be given on the complexity of in vivo models and the challenges in vitro models face to reach the same levels of complexity in a controllable manner. First, a brief introduction of novel developments in two dimensional (2D) models and ex vivo models is provided. Next, recent developments in three dimensional (3D) in vitro models are described ranging from spheroids, organoids, scaffold models, bioprinted models to organ-on-chip models including a discussion on advantages and limitations for each model. Furthermore, we will provide a detailed overview on the current PDAC in vivo models including chemically-induced models, syngeneic and xenogeneic models, highlighting hetero- and orthotopic, patient-derived tissues (PDX) models, and genetically engineered mouse models. Finally, we will provide a discussion on overall limitations of both, in vitro and in vivo models, and discuss necessary steps to overcome these limitations to reach an efficient drug development pipeline, as well as discuss possibilities to include novel in silico models in the process.

Systems genetics analysis of oral squamous cell carcinoma susceptibility using the mouse model: current position and new perspective

Oral squamous cell carcinoma (OSCC) is one of the most common human malignancies with complex etiology and poor prognosis. Although environmental carcinogens and carcinogenic viruses are still considered the main etiologic factors for OSCC development, genetic factors obviously play a key role in the initiation and progression of this neoplasm, given that not all individuals exposed to carcinogens develop the same severity of the disease, if any. Identifying genetic loci modulating OSCC risk may have several important clinical implications, including early detection, prevention and developing new treatment strategies. Due to limitations in controlled and standardized genetic studies in humans, genetic components underlying susceptibility of OSCC development remain largely unknown. A combination of quantitative trait loci mapping in mice, with complementary association studies in humans, has the potential to discover novel cancer risk loci. As of today, a limited number of genetic analyses were applied on rodent models to locate novel genetic loci associated with human OSCC. Here, we discuss the current status of the mouse models use for dissecting the genetic basis of OSCC and highlight how systems genetics analysis using mouse models, may increase our understanding of human OSCC susceptibility.

Development of PET Radioligands Targeting COX-2 for Colorectal Cancer Staging, a Review of in vitro and Preclinical Imaging Studies

Colorectal cancer (CRC) is the second most common cause of cancer death, making early diagnosis a major public health challenge. The role of inflammation in tumorigenesis has been extensively explored, and among the identified markers of inflammation, cyclooxygenase-2 (COX-2) expression seems to be linked to lesions with a poor prognosis. Until now, COX-2 expression could only be accessed by invasive methods, mainly by biopsy. Imaging techniques such as functional Positron Emission Tomography (PET) could give access to in vivo COX-2 expression. This could make the staging of the disease more accurate and would be of particular interest in the exploration of the first metastatic stages. In this paper, we review recent progress in the development of COX-2 specific PET tracers by comparing the radioligands' characteristics and highlighting the obstacles that remain to be overcome in order to achieve the clinical development of such a radiotracer, and its evaluation in the management of CRC.

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

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