Modeling metastasis in mice: a closer look

ATAD2 Drives Prostate Cancer Progression to Metastasis

Metastasis accounts for the overwhelming majority of cancer deaths. In prostate cancer and many other solid tumors, progression to metastasis is associated with drastically reduced survival outcomes, yet the mechanisms behind this progression remain largely unknown. ATPase family AAA domain containing 2 (ATAD2) is an epigenetic reader of acetylated histones that is overexpressed in multiple cancer types and usually associated with poor patient outcomes. However, the functional role of ATAD2 in cancer progression and metastasis has been relatively understudied. Here, we employ genetically engineered mouse models of prostate cancer bone metastasis, as well as multiple independent human cohorts, to show that ATAD2 is highly enriched in bone metastasis compared with primary tumors and significantly associated with the development of metastasis. We show that ATAD2 expression is associated with MYC pathway activation in patient datasets and that, at least in a subset of tumors, MYC and ATAD2 can regulate each other's expression. Using functional studies on mouse bone metastatic cell lines and innovative organ-on-a-chip bone invasion assays, we establish a functional role for ATAD2 inhibition in reducing prostate cancer metastasis and growth in bone. Implications: Our study highlights ATAD2 as a driver of prostate cancer progression and metastasis and suggests it may constitute a promising novel therapeutic target.

Demonstration of Enhancement of Tumor Intravasation by Dicarbonyl Stress Using a Microfluidic Organ-on-chip

Cancer metastasis involves cell migration from their primary organ foci into vascular channels, followed by dissemination to prospective colonization sites. Vascular entry of tumor cells or intravasation involves their breaching stromal and endothelial extracellular matrix (ECM) and the endothelial barriers. How the kinetics of this breach are confounded by chronic inflammatory stresses seen in diabetes and aging remains ill-investigated. To study the problem, a histopathology-motivated, imaging-tractable, microfluidic multi-organ-on-chip platform is constructed, that seamlessly integrates a breast tumor-like compartment: invasive MDA-MB-231 in a 3D Collagen I scaffold, and a flow-implemented vascular channel: immortalized human aortic endothelia (TeloHAEC) on laminin-rich basement membrane (lrBM). The chip showcases the complexity of intravasation, wherein tumor cells and endothelia cooperate to form anastomotic structures, which facilitate cancer cell migration into the vascular channel. Upon entry, cancer cells adhere to and flow within the vascular channel. Exposure to methylglyoxal (MG), a dicarbonyl stressor associated with diabetic circulatory milieu increases cancer cell intravasation and adhesion through the vascular channel. This can be driven by MG-induced endothelial senescence and shedding, but also by the ability of MG to degrade lrBM and pathologically cross-link Collagen I, diminishing cell-ECM adhesion. Thus, dicarbonyl stress attenuates homeostatic barriers to cancer intravasation, exacerbating metastasis.

Bridging the gap: From petri dish to patient - Advancements in translational drug discovery

Translational research serves as the bridge between basic research and practical applications in clinical settings. The journey from "bench to bedside" is fraught with challenges and complexities such as the often-observed disparity between how compounds behave in a laboratory setting versus in the complex systems of living organisms. The challenge is further compounded by the limited ability of in vitro models to mimic the specific biochemical environment of human tissues. This article explores and details the recent advancements and innovative approaches that are increasingly successful in bridging the gap between laboratory research and patient care. These advancements include, but are not limited to, sophisticated in vitro models such as organ-on-a-chip and computational models that utilize artificial intelligence to predict drug efficacy and safety. The article aims to showcase how these technologies improve the predictability of drug performance in human bodies and significantly speed up the drug development process. Furthermore, it discusses the role of biomarker discovery in preparation of more targeted and personalized therapy approaches and covers the impact of regulatory changes designed to facilitate drug approvals. Additionally, by providing detailed case studies of successful applications, we illustrate the practical impacts of these innovations on drug discovery and patient care.

Injecting hope: the potential of intratumoral immunotherapy for locally advanced and metastatic cancer

Despite enormous progress, advanced cancers are still one of the most serious medical problems in current society. Although various agents and therapeutic strategies with anticancer activity are known and used, they often fail to achieve satisfactory long-term patient outcomes and survival. Recently, immunotherapy has shown success in patients by harnessing important interactions between the immune system and cancer. However, many of these therapies lead to frequent side effects when administered systemically, prompting treatment modifications or discontinuation or, in severe cases, fatalities. New therapeutic approaches like intratumoral immunotherapy, characterized by reduced side effects, cost, and systemic toxicity, offer promising prospects for future applications in clinical oncology. In the context of locally advanced or metastatic cancer, combining diverse immunotherapeutic and other treatment strategies targeting multiple cancer hallmarks appears crucial. Such combination therapies hold promise for improving patient outcomes and survival and for promoting a sustained systemic response. This review aims to provide a current overview of immunotherapeutic approaches, specifically focusing on the intratumoral administration of drugs in patients with locally advanced and metastatic cancers. It also explores the integration of intratumoral administration with other modalities to maximize therapeutic response. Additionally, the review summarizes recent advances in intratumoral immunotherapy and discusses novel therapeutic approaches, outlining future directions in the field.

CAR T cells in solid tumors and metastasis: paving the way forward

CAR T cell therapy, hailed as a breakthrough in cancer treatment due to its remarkable outcomes in hematological malignancies, encounters significant hurdles when applied to solid tumors. While notable responses to CAR T cells remain sporadic in these patients, challenges persist due to issues such as on-target off-tumor toxicity, difficulties in their trafficking and infiltration into the tumor, and the presence of a hostile and immunosuppressive microenvironment. This review aims to explore recent endeavors aimed at overcoming these obstacles in CAR T cell therapy for solid tumors. Specifically, we will delve into promising strategies for enhancing tumor specificity through antigen targeting, addressing tumor heterogeneity, overcoming physical barriers, and counteracting the immune-suppressive microenvironment.

Brd4::Nutm1 fusion gene initiates NUT carcinoma in vivo

NUT carcinoma (NC) is an aggressive cancer with no effective treatment. About 70% of NUT carcinoma is associated with chromosome translocation events that lead to the formation of a BRD4::NUTM1 fusion gene. Because the BRD4::NUTM1 gene is unequivocally cytotoxic when ectopically expressed in cell lines, questions remain on whether the fusion gene can initiate NC. Here, we report the first genetically engineered mouse model for NUT carcinoma that recapitulates the human t(15;19) chromosome translocation in mice. We demonstrated that the mouse t(2;17) syntenic chromosome translocation, forming the Brd4::Nutm1 fusion gene, could induce aggressive carcinomas in mice. The tumors present histopathological and molecular features similar to human NC, with enrichment of undifferentiated cells. Similar to the reports of human NC incidence, Brd4::Nutm1 can induce NC from a broad range of tissues with a strong phenotypical variability. The consistent induction of poorly differentiated carcinoma demonstrated a strong reprogramming activity of BRD4::NUTM1. The new mouse model provided a critical preclinical model for NC that will lead to better understanding and therapy development for NC.

Development of Traceable Mouse Models of Advanced and Metastatic Bladder Cancer

Bladder cancer (BC) is the fourth most common cancer in men, with a poor patient prognosis for advanced disease. The poor survival of patients with muscle-invasive bladder cancer (MIBC) and metastatic status emphasizes the urgent need to develop new therapies. Lacking in the field of BC is the availability of relevant advanced BC mouse models, especially metastatic ones, that accurately recapitulate the complexities of human pathology to test and study new therapeutic strategies. Addressing this need, we developed a traceable mouse model of BC that expresses tumor-associated antigens within the context of advanced muscle-invasive BC. This novel system was achieved through the deletion of the tp53 and pten genes, alongside the incorporation of the fusion construct of Firefly luciferase (Luc) and the SIYRYYGL (SIY) T-cell antigen. We validate that the presence of the transgene did not impact on the development of the tumors while allowing us to measure tumor progression by bioluminescence. We show that the transgene did not influence the composition of the immune tumor microenvironment. More importantly, we report that this model was unresponsive to anti-PD-1 treatment, as in the majority of patients with BC. We also develop a new model based on the orthotopic injection of BC clonal cell lines derived from our first model. We demonstrate that this new model invades the muscle layer and has a metastasis development rate of 83%. The advantage of this model is that we can visualize tumor growth and metastasis development in vivo. These mouse models' characteristics, displaying many similarities with the human pathology, provide a valuable tool for tracking tumor progression, metastasis spread in vivo, and treatment resistance, as well as exploring fundamental and translational aspects of BC biology. This work contributes to the improvement in the landscape of mouse models of advanced BC for testing new therapeutic strategies.

Recent advances in micro-physiological systems for investigating tumor metastasis and organotropism

Tumor metastasis involves complex processes that traditional 2D cultures and animal models struggle to fully replicate. Metastatic tumors undergo a multitude of transformations, including genetic diversification, adaptation to diverse microenvironments, and modified drug responses, contributing significantly to cancer-related mortality. Micro-physiological systems (MPS) technology emerges as a promising approach to emulate the metastatic process by integrating critical biochemical, biomechanical, and geometrical cues at a microscale. These systems are particularly advantageous simulating metastasis organotropism, the phenomenon where tumors exhibit a preference for metastasizing to particular organs. Organotropism is influenced by various factors, such as tumor cell characteristics, unique organ microenvironments, and organ-specific vascular conditions, all of which can be effectively examined using MPS. This review surveys the recent developments in MPS research from the past five years, with a specific focus on their applications in replicating tumor metastasis and organotropism. Furthermore, we discuss the current limitations in MPS-based studies of organotropism and propose strategies for more accurately replicating and analyzing the intricate aspects of organ-specific metastasis, which is pivotal in the development of targeted therapeutic approaches against metastatic cancers.

"Blind men and an elephant": The need for animals in research, drug safety studies, and understanding civilizational diseases

Animal-based research and drug safety studies are essential to understanding the mysteries of nature and the long-term survival of humans. Due to the rapid increase in the global human population, conflict- and economically driven human migration, tourism-related activities, densely populated metropolitan areas, and local policies, humans will be affected by a multitude of novel disease-causing microorganisms and civilizational diseases. Despite disparities among countries, recent and planned changes in regulations concerning animal research and drug safety studies could have detrimental effects on both the animal research community and nations lacking sufficient social support systems. Based on existing scientific literature, I argue that we need animal research encompassing aspects such as animal development, behavior, drug safety studies, and for the understanding of future civilizational diseases. Depending on the nature of the research questions and local challenges, a suitable animal model organism should be made mandatory.

Breast Cancer Brain Metastases: Implementation and Characterization of a Mouse Model Relying on Malignant Cells Inoculation in the Carotid Artery

Breast cancer (BC) brain metastases (BCBM) is a severe condition frequently occurring in the triple-negative subtype. The study of BCBM pathogenesis and treatment has been hampered by the difficulty in establishing a reliable animal model that faithfully recapitulates the preferential formation of brain metastases. The injection of BC cells in the carotid artery of mice has been proposed but the procedure is challenging, with the metastatic pattern being scarcely characterized. In this work, we thoroughly describe an improved procedure, highlighting the tricks and challenges of the process, and providing a characterization of the brain and peripheral metastatic pattern at the cellular and molecular level. Triple-negative BC (4T1) cells were inoculated in the common carotid artery of BALB/c mice. Brains and peripheral organs were harvested at 7-14 days for the histological characterization of the metastases' pattern and the immunofluorescence analysis of specific markers. With our surgical procedure, both mouse death and procedure-associated weight loss were negligible. Brain metastases mostly occurred in the hippocampus, while sparse peripheral lesions were only detected in the lungs. Brain-colonizing BC cells presented proliferative (Ki-67) and epithelial (pan-cytokeratin and tomato lectin) features, which account for metastases' establishment. The presented surgical approach constitutes an important and reliable tool for BCBM studies.

Recent Advancement in Breast Cancer Research: Insights from Model Organisms-Mouse Models to Zebrafish

Animal models have been utilized for decades to investigate the causes of human diseases and provide platforms for testing novel therapies. Indeed, breakthrough advances in genetically engineered mouse (GEM) models and xenograft transplantation technologies have dramatically benefited in elucidating the mechanisms underlying the pathogenesis of multiple diseases, including cancer. The currently available GEM models have been employed to assess specific genetic changes that underlay many features of carcinogenesis, including variations in tumor cell proliferation, apoptosis, invasion, metastasis, angiogenesis, and drug resistance. In addition, mice models render it easier to locate tumor biomarkers for the recognition, prognosis, and surveillance of cancer progression and recurrence. Furthermore, the patient-derived xenograft (PDX) model, which involves the direct surgical transfer of fresh human tumor samples to immunodeficient mice, has contributed significantly to advancing the field of drug discovery and therapeutics. Here, we provide a synopsis of mouse and zebrafish models used in cancer research as well as an interdisciplinary 'Team Medicine' approach that has not only accelerated our understanding of varied aspects of carcinogenesis but has also been instrumental in developing novel therapeutic strategies.

Dissecting metastasis using preclinical models and methods

Metastasis has long been understood to lead to the overwhelming majority of cancer-related deaths. However, our understanding of the metastatic process, and thus our ability to prevent or eliminate metastases, remains frustratingly limited. This is largely due to the complexity of metastasis, which is a multistep process that likely differs across cancer types and is greatly influenced by many aspects of the in vivo microenvironment. In this Review, we discuss the key variables to consider when designing assays to study metastasis: which source of metastatic cancer cells to use and where to introduce them into mice to address different questions of metastasis biology. We also examine methods that are being used to interrogate specific steps of the metastatic cascade in mouse models, as well as emerging techniques that may shed new light on previously inscrutable aspects of metastasis. Finally, we explore approaches for developing and using anti-metastatic therapies, and how mouse models can be used to test them.

Modelling Cancer Metastasis in Drosophila melanogaster

Cancer metastasis, the process by which tumour cells spread throughout the body and form secondary tumours at distant sites, is the leading cause of cancer-related deaths. The metastatic cascade is a highly complex process encompassing initial dissemination from the primary tumour, travel through the blood stream or lymphatic system, and the colonisation of distant organs. However, the factors enabling cells to survive this stressful process and adapt to new microenvironments are not fully characterised. Drosophila have proven a powerful system in which to study this process, despite important caveats such as their open circulatory system and lack of adaptive immune system. Historically, larvae have been used to model cancer due to the presence of pools of proliferating cells in which tumours can be induced, and transplanting these larval tumours into adult hosts has enabled tumour growth to be monitored over longer periods. More recently, thanks largely to the discovery that there are stem cells in the adult midgut, adult models have been developed. We focus this review on the development of different Drosophila models of metastasis and how they have contributed to our understanding of important factors determining metastatic potential, including signalling pathways, the immune system and the microenvironment.

Current methods for studying metastatic potential of tumor cells

Cell migration and invasiveness significantly contribute to desirable physiological processes, such as wound healing or embryogenesis, as well as to serious pathological processes such as the spread of cancer cells to form tumor metastasis. The availability of appropriate methods for studying these processes is essential for understanding the molecular basis of cancer metastasis and for identifying suitable therapeutic targets for anti-metastatic treatment. This review summarizes the current status of these methods: In vitro methods for studying cell migration involve two-dimensional (2D) assays (wound-healing/scratch assay), and methods based on chemotaxis (the Dunn chamber). The analysis of both cell migration and invasiveness in vitro require more complex systems based on the Boyden chamber principle (Transwell migration/invasive test, xCELLigence system), or microfluidic devices with three-dimensional (3D) microscopy visualization. 3D culture techniques are rapidly becoming routine and involve multicellular spheroid invasion assays or array chip-based, spherical approaches, multi-layer/multi-zone culture, or organoid non-spherical models, including multi-organ microfluidic chips. The in vivo methods are mostly based on mice, allowing genetically engineered mice models and transplant models (syngeneic mice, cell line-derived xenografts and patient-derived xenografts including humanized mice models). These methods currently represent a solid basis for the state-of-the art research that is focused on understanding metastatic fundamentals as well as the development of targeted anti-metastatic therapies, and stratified treatment in oncology.

In Vivo Models for Prostate Cancer Research

In 2022, prostate cancer (PCa) is estimated to be the most commonly diagnosed cancer in men in the United States-almost 270,000 American men are estimated to be diagnosed with PCa in 2022. This review compares and contrasts in vivo models of PCa with regards to the altered genes, signaling pathways, and stages of tumor progression associated with each model. The main type of model included in this review are genetically engineered mouse models, which include conditional and constitutive knockout model. 2D cell lines, 3D organoids and spheroids, xenografts and allografts, and patient derived models are also included. The major applications, advantages and disadvantages, and ease of use and cost are unique to each type of model, but they all make it easier to translate the tumor progression that is seen in the mouse prostate to the human prostate. Although both human and mouse prostates are androgen-dependent, the fact that the native, genetically unaltered prostate in mice cannot give rise to carcinoma is an especially critical component of PCa models. Thanks to the similarities between the mouse and human genome, our knowledge of PCa has been expanded, and will continue to do so, through models of PCa.

Loss of endothelial EMCN drives tumor lung metastasis through the premetastatic niche

Background

Metastasis is the primary cause of cancer-related mortality. Metastasis involves a complex multistep process during which individual tumor cells spread primarily through destruction of the endothelial barrier, entering the circulatory system to colonize distant organs. However, the role of the endothelial barrier as the rate-limiting process in tumor metastasis and how these processes affect the regulation of the host microenvironment at the molecular level are poorly understood.

Methods

Here, we analyzed differentially expressed genes in breast cancer and lung adenocarcinoma, including metastatic and recurrent specimens, using TCGA dataset. The effects of EMCN on endothelial cells in vitro and in vivo were analyzed by assessing angiogenesis and vascular permeability, respectively. We established a syngeneic mouse model of endothelial cell-specific knockout of EMCN (EMCN^ecko) to study the role of EMCN in tumor growth and metastasis. Transcriptome sequencing, Western blotting, qPCR and immunofluorescence confirmed important factors in the premetastatic niche. A mouse model of allograft tumor resection with lung metastasis was established to confirm the therapeutic effect of a notch inhibitor combined with an anti-TGF-β antibody.

Results

We found a strong correlation of EMCN deficiency with tumor recurrence and metastasis. Comparative experiments in WT and EMCN^ecko mice revealed that endothelial EMCN deficiency did not affect primary tumor growth significantly but strongly promoted spontaneous metastasis. EMCN deficiency was associated with gene profiles that regulate cell junctions in vitro and enhance vascular permeability in vivo. Mechanistically, EMCN deficiency mainly affected the host microenvironment and led to the formation of a lung premetastatic niche by recruiting Ly6G⁺ neutrophils and upregulating MMP9, S100A8/A9 and TGF-β expression. Anti-TGF-β antibody effectively eliminated TGF-β-induced neutrophil polarization, thereby reducing lung metastasis. Notably, the combination of a Notch inhibitor and an anti-TGF-β antibody effectively inhibited tumor growth and lung metastasis and prolonged the survival time of mice.

Conclusions

We present a new translational strategy of EMCN as a new key player in tumor lung metastasis by affecting the host microenvironment. These findings could provide a sound theoretical basis for clinical treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03649-4.