The mighty mouse: genetically engineered mouse models in cancer drug development

Bridging the Knowledge of Different Worlds to Understand the Big Picture of Cancer Nanomedicines

Explosive growth of nanomedicines continues to significantly impact the therapeutic strategies for effective cancer treatment. Despite the significant progress in the development of advanced nanomedicines, successful clinical translation remains challenging. As cancer nanomedicine is a multidisciplinary field, the fundamental problem is that the knowledge gaps stem from different vantage points in the understanding of cancer nanomedicines. The complexities and heterogenecity of both nanomedicines and cancer are further demanding the integration of highly diverse expertise to develop clinically translatable cancer nanomedicines. This progress report aims to discuss the current understanding of cancer nanomedicines between different research areas in terms of nanoparticle engineering, formulation, tumor patho-physiology and clinical medicine, as well as to identify the knowledge gaps lying at the interface between the different fields of research in nanomedicine. Here we also highlight for the necessity to harmonize the multidisciplinary effort in the research of nanomedicines in order to bridge the knowledge and to advance the full understanding in cancer nanomedicines. A paradigm shift is needed in the strategic development of disease specific nanomedicines in order to foster the successful translation into clinic of future cancer nanomedicines.

Functional analyses of major cancer-related signaling pathways in Alzheimer's disease etiology

Alzheimer's disease (AD) is an aging-related neurodegenerative disease and accounts for majority of human dementia. The hyper-phosphorylated tau-mediated intracellular neurofibrillary tangle and amyloid β-mediated extracellular senile plaque are characterized as major pathological lesions of AD. Different from the dysregulated growth control and ample genetic mutations associated with human cancers, AD displays damage and death of brain neurons in the absence of genomic alterations. Although various biological processes predominately governing tumorigenesis such as inflammation, metabolic alteration, oxidative stress and insulin resistance have been associated with AD genesis, the mechanistic connection of these biological processes and signaling pathways including mTOR, MAPK, SIRT, HIF, and the FOXO pathway controlling aging and the pathological lesions of AD are not well recapitulated. Hence, we performed a thorough review by summarizing the physiological roles of these key cancer-related signaling pathways in AD pathogenesis, comprising of the crosstalk of these pathways with neurofibrillary tangle and senile plaque formation to impact AD phenotypes. Importantly, the pharmaceutical investigations of anti-aging and AD relevant medications have also been highlighted. In summary, in this review, we discuss the potential role that cancer-related signaling pathways may play in governing the pathogenesis of AD, as well as their potential as future targeted strategies to delay or prevent aging-related diseases and combating AD.

Osteopontin is involved in TLR4 pathway contributing to ovarian cancer cell proliferation and metastasis

Tumor cell proliferation and metastasis are critical for tumor progression and lead to death of cancer patients. TLR4 is a member of the toll-like receptor (TLR) family, which promotes tumor growth, metastasis and immune escape. Osteopontin (OPN), a phosphorylated glycoprotein extensively expressed in multiple cell-types, plays important roles in tumorigenesis, metastasis and infiltration, and participates in signal transduction of innate immunity. However, it is unclear whether TLR4 has any relationship with OPN. The current study investigated the role of TLR4 and OPN in tumor proliferation and metastasis, and the potential effect of TLR4 signaling on OPN using the human ovarian cancer cell line HO-8910PM. High expression levels of TLR4 and OPN were detected in HO-8910PM cells, which promoted the proliferation, migration and invasion of tumor cells. Lipopolysaccharide (LPS) induced activation of TLR4 up-regulated OPN, increasing the malignant phenotype of cells. RNAi-mediated knockdown of OPN reduced significantly the metastatic phenotype activated by TLR4. Taken together, our study demonstrates that OPN contributes to the ovarian cancer cell proliferation and metastasis, which is activated by TLR4 signaling pathway. It provides new insights for the mechanisms of tumor development and metastasis, and suggests targeting TLR4 and OPN as an intervention in the ovarian cancer treatment.

Comparison and combination of rotational imaging optical coherence tomography and selective plane illumination microscopy for embryonic study

Several optical imaging techniques have been applied for high-resolution embryonic imaging using different contrast mechanisms, each with their own benefits and limitations. In this study, we imaged the same E9.5 mouse embryo with rotational imaging optical coherence tomography (RI-OCT) and selective plane illumination microscopy (SPIM). RI-OCT overcomes optical penetration limits of traditional OCT imaging that prohibit full-body imaging of mouse embryos at later stages by imaging the samples from multiple angles. SPIM enables high-resolution, 3D imaging with less phototoxicity and photobleaching than laser scanning confocal microscopy (LSCM) by illuminating the sample with a focused sheet of light. Side by side comparisons are supplemented with co-registered images. The results demonstrate that SPIM and RI-OCT are highly complementary and could provide more comprehensive tissue characterization for mouse embryonic research.

Cytosolic Hsp90α and its mitochondrial isoform Trap1 are differentially required in a breast cancer model

The Hsp90 family of molecular chaperones includes the cytosolic isoforms Hsp90a and Hsp90β and the mitochondrial isoform Trap1. Hsp90a/βsupport a large number of client proteins in the cytoplasm and the nucleus whereas Trap1 regulates oxidative phosphorylation in mitochondria. Many of the associated proteins and cellular processes are relevant to cancer, and there is ample pharmacological and genetic evidence to support the idea that Hsp90a/βand Trap1 are required for tumorigenesis. However, a direct and comparative genetic test in a mouse cancer model has not been done. Here we report the effects of deleting the Hsp90a or Trap1 genes in a mouse model of breast cancer. Neither Hsp90a nor Trap1 are absolutely required for mammary tumor initiation, growth and metastasis induced by the polyoma middle T-antigen as oncogene. However, they do modulate growth and lung metastasis in vivo and cell proliferation, migration and invasion of isolated primary carcinoma cells in vitro. Without Hsp90a, tumor burden and metastasis are reduced, correlating with impaired proliferation, migration and invasion of cells in culture. Without Trap1, the appearance of tumors is initially delayed, and isolated cells are affected similarly to those without Hsp90a. Analysis of expression data of human breast cancers supports the conclusion that this is a valid mouse model highlighting the importance of these molecular chaperones.

Patient-derived xenografts as preclinical neuroblastoma models

The prognosis for children with high-risk neuroblastoma is often poor and survivors can suffer from severe side effects. Predictive preclinical models and novel therapeutic strategies for high-risk disease are therefore a clinical imperative. However, conventional cancer cell line-derived xenografts can deviate substantially from patient tumors in terms of their molecular and phenotypic features. Patient-derived xenografts (PDXs) recapitulate many biologically and clinically relevant features of human cancers. Importantly, PDXs can closely parallel clinical features and outcome and serve as excellent models for biomarker and preclinical drug development. Here, we review progress in and applications of neuroblastoma PDX models. Neuroblastoma orthotopic PDXs share the molecular characteristics, neuroblastoma markers, invasive properties and tumor stroma of aggressive patient tumors and retain spontaneous metastatic capacity to distant organs including bone marrow. The recent identification of genomic changes in relapsed neuroblastomas opens up opportunities to target treatment-resistant tumors in well-characterized neuroblastoma PDXs. We highlight and discuss the features and various sources of neuroblastoma PDXs, methodological considerations when establishing neuroblastoma PDXs, in vitro 3D models, current limitations of PDX models and their application to preclinical drug testing.

Establishment of two ovarian cancer orthotopic xenograft mouse models for in vivo imaging: A comparative study

Orthotopic tumor animal models are optimal for preclinical research of novel therapeutic interventions. The aim of the present study was to compare two types of ovarian cancer orthotopic xenograft (OCOX) mouse models, i.e. cellular orthotopic injection (COI) and surgical orthotopic implantation (SOI), regarding xenograft formation rate, in vivo imaging, tumor growth and metastasis, and tumor microenvironment. The tumor formation and progression were monitored by bioluminescent in vivo imaging. Cell proliferation and migration abilities were detected by EdU and scratch assays, respectively. Expression of α-SMA, CD34, MMP2, MMP9, vimentin, E-cadherin and Ki67 in tumor samples were detected by immunohistochemistry. As a result, we successfully established COI- and SOI-OCOX mouse models using ovarian cancer cell lines ES2 and SKOV3. The tumor formation rate in the COI and SOI models were 87.5 and 100%, respectively. Suspected tumor cell leakage occurred in 37.5% of the COI models. The SOI xenografts grew faster, held larger primary tumors, and were more metastatic than the COI xenografts. The migration and proliferation properties of the cells that generated SOI xenografts were significantly starker than those deriving COI xenografts in vitro. The tumor cells in SOI xenografts exhibited a mesenchymal phenotype and proliferated more actively than those in the COI xenografts. Additionally, compared with the COI tumors, the SOI tumors contained more cancer associated fibroblasts, matrix metallopeptidase 2 and 9. In conclusion, SOI is a feasible and reliable technique to establish OCOX mouse models mimicking the clinical process of ovarian cancer growth and metastasis, although SOI is more technically difficult and time-consuming than COI.

Integrated Genomic Medicine: A Paradigm for Rare Diseases and Beyond

Individualized medicine, or the tailoring of therapeutic interventions to a patient's unique genetic, biochemical, physiological, exposure and behavioral profile, has been enhanced, if not enabled, by modern biomedical technologies such as high-throughput DNA sequencing platforms, induced pluripotent stem cell assays, biomarker discovery protocols, imaging modalities, and wireless monitoring devices. Despite successes in the isolated use of these technologies, however, it is arguable that their combined and integrated use in focused studies of individual patients is the best way to not only tailor interventions for those patients, but also shed light on treatment strategies for patients with similar conditions. This is particularly true for individuals with rare diseases since, by definition, they will require study without recourse to other individuals, or at least without recourse to many other individuals. Such integration and focus will require new biomedical scientific paradigms and infrastructure, including the creation of databases harboring study results, the formation of dedicated multidisciplinary research teams and new training programs. We consider the motivation and potential for such integration, point out areas in need of improvement, and argue for greater emphasis on improving patient health via technological innovations, not merely improving the technologies themselves. We also argue that the paradigm described can, in theory, be extended to the study of individuals with more common diseases.

Isolation of Circulating Tumor Cells in an Orthotopic Mouse Model of Colorectal Cancer

Despite the advantages of easy applicability and cost-effectiveness, subcutaneous mouse models have severe limitations and do not accurately simulate tumor biology and tumor cell dissemination. Orthotopic mouse models have been introduced to overcome these limitations; however, such models are technically demanding, especially in hollow organs such as the large bowel. In order to produce uniform tumors which reliably grow and metastasize, standardized techniques of tumor cell preparation and injection are critical. We have developed an orthotopic mouse model of colorectal cancer (CRC) which develops highly uniform tumors and can be used for tumor biology studies as well as therapeutic trials. Tumor cells from either primary tumors, 2-dimensional (2D) cell lines or 3-dimensional (3D) organoids are injected into the cecum and, depending on the metastatic potential of the injected tumor cells, form highly metastatic tumors. In addition, CTCs can be found regularly. We here describe the technique of tumor cell preparation from both 2D cell lines and 3D organoids as well as primary tumor tissue, the surgical and injection techniques as well as the isolation of CTCs from the tumor-bearing mice, and present tips for troubleshooting.

A Genetically Engineered Mouse Model of Sporadic Colorectal Cancer

Despite the advantages of easy applicability and cost-effectiveness, colorectal cancer mouse models based on tumor cell injection have severe limitations and do not accurately simulate tumor biology and tumor cell dissemination. Genetically engineered mouse models have been introduced to overcome these limitations; however, such models are technically demanding, especially in large organs such as the colon in which only a single tumor is desired. As a result, an immunocompetent, genetically engineered mouse model of colorectal cancer was developed which develops highly uniform tumors and can be used for tumor biology studies as well as therapeutic trials. Tumor development is initiated by surgical, segmental infection of the distal colon with adeno-cre virus in compound conditionally mutant mice. The tumors can be easily detected and monitored via colonoscopy. We here describe the surgical technique of segmental adeno-cre infection of the colon, the surveillance of the tumor via high-resolution colonoscopy and present the resulting colorectal tumors.

Genetically engineered mouse models for studying radiation biology

Genetically engineered mouse models (GEMMs) are valuable research tools that have transformed our understanding of cancer. The first GEMMs generated in the 1980s and 1990s were knock-in and knock-out models of single oncogenes or tumor suppressors. The advances that made these models possible catalyzed both technological and conceptual shifts in the way cancer research was conducted. As a result, dozens of mouse models of cancer exist today, covering nearly every tissue type. The advantages inherent to GEMMs compared to in vitro and in vivo transplant models are compounded in preclinical radiobiology research for several reasons. First, they accurately and robustly recapitulate primary cancers anatomically, histopathologically, and genetically. Reliable models are a prerequisite for predictive preclinical studies. Second, they preserve the tumor microenvironment, including the immune, vascular, and stromal compartments, which enables the study of radiobiology at a systems biology level. Third, they provide exquisite control over the genetics and kinetics of tumor initiation, which enables the study of specific gene mutations on radiation response and functional genomics in vivo. Taken together, these facets allow researchers to utilize GEMMs for rigorous and reproducible preclinical research. In the three decades since the generation of the first GEMMs of cancer, advancements in modeling approaches have rapidly progressed and expanded the mouse modeling toolbox with techniques such as in vivo short hairpin RNA (shRNA) knockdown, inducible gene expression, site-specific recombinases, and dual recombinase systems. Our lab and many others have utilized these tools to study cancer and radiobiology. Recent advances in genome engineering with CRISPR/Cas9 technology have made GEMMs even more accessible to researchers. Here, we review current and future approaches to mouse modeling with a focus on applications in preclinical radiobiology research.

In vivo genome editing and organoid transplantation models of colorectal cancer and metastasis

In vivo interrogation of the function of genes implicated in tumorigenesis is limited by the need to generate and cross germline mutant mice. Here we describe approaches to model colorectal cancer (CRC) and metastasis, which rely on in situ gene editing and orthotopic organoid transplantation in mice without cancer-predisposing mutations. Autochthonous tumor formation is induced by CRISPR-Cas9-based editing of the Apc and Trp53 tumor suppressor genes in colon epithelial cells and by orthotopic transplantation of Apc-edited colon organoids. ApcΔ/Δ;KrasG12D/+;Trp53Δ/Δ (AKP) mouse colon organoids and human CRC organoids engraft in the distal colon and metastasize to the liver. Finally, we apply the orthotopic transplantation model to characterize the clonal dynamics of Lgr5+ stem cells and demonstrate sequential activation of an oncogene in established colon adenomas. These experimental systems enable rapid in vivo characterization of cancer-associated genes and reproduce the entire spectrum of tumor progression and metastasis.

Modeling of Patient-Derived Xenografts in Colorectal Cancer

Developing realistic preclinical models using clinical samples that mirror complex tumor biology and behavior are vital to advancing cancer research. While cell line cultures have been helpful in generating preclinical data, the genetic divergence between these and corresponding primary tumors has limited clinical translation. Conversely, patient-derived xenografts (PDX) in colorectal cancer are highly representative of the genetic and phenotypic heterogeneity in the original tumor. Coupled with high-throughput analyses and bioinformatics, these PDXs represent robust preclinical tools for biomarkers, therapeutic target, and drug discovery. Successful PDX engraftment is hypothesized to be related to a series of anecdotal variables namely, tissue source, cancer stage, tumor grade, acquisition strategy, time to implantation, exposure to prior systemic therapy, and genomic heterogeneity of tumors. Although these factors at large can influence practices and patterns related to xenotransplantation, their relative significance in determining the success of establishing PDXs is uncertain. Accordingly, we systematically examined the predictive ability of these factors in establishing PDXs using 90 colorectal cancer patient specimens that were subcutaneously implanted into immunodeficient mice. Fifty (56%) PDXs were successfully established. Multivariate analyses showed tissue acquisition strategy [surgery 72.0% (95% confidence interval (CI): 58.2-82.6) vs. biopsy 35% (95% CI: 22.1%-50.6%)] to be the key determinant for successful PDX engraftment. These findings contrast with current empiricism in generating PDXs and can serve to simplify or liberalize PDX modeling protocols. Better understanding the relative impact of these factors on efficiency of PDX formation will allow for pervasive integration of these models in care of colorectal cancer patients. Mol Cancer Ther; 16(7); 1435-42. ©2017 AACR.

A minimum core outcome dataset for the reporting of preclinical chemotherapeutic drug studies: Lessons learned from multiple discordant methodologies in the setting of colorectal cancer

In vivo studies in animal models are critical tools necessary to study the fundamental complexity of carcinogenesis. A constant strive to improve animal models in cancer exists, especially those investigating the use of chemotherapeutic effectiveness. In the present systematic review, colorectal cancer (CRC) is used as an example to highlight and critically evaluate the range of reporting strategies used when investigating chemotherapeutic agents in the preclinical setting. A systematic review examining the methodology and reporting of preclinical chemotherapeutic drug studies using CRC murine models was conducted. A total of 45 studies were included in this systematic review. The literature was found to be highly heterogeneous with various cell lines, animal strains, animal ages and chemotherapeutic compounds/regimens tested, proving difficult to compare outcomes between similar studies or indeed gain any significant insight into which chemotherapeutic regimen caused adverse events. From this analysis we propose a minimum core outcome dataset that could be regarded as a standardised way of reporting results from in vivo experimentation.

Exploiting the cancer niche: Tumor-associated macrophages and hypoxia as promising synergistic targets for nano-based therapy

The tumor microenvironment has been widely exploited as an active participant in tumor progression. Extensive reports have defined the dual role of tumor-associated macrophages (TAMs) in tumor development. The protumoral effect exerted by the M2 phenotype has been correlated with a negative outcome in most solid tumors. The high infiltration of immune cells in the hypoxic cores of advanced solid tumors leads to a chain reaction of stimuli that enhances the expression of protumoral genes, thrives tumor malignancy, and leads to the emergence of drug resistance. Many studies have shown therapeutic targeting systems, solely to TAMs or tumor hypoxia, however, novel therapeutics that target both features are still warranted. In the present review, we discuss the role of hypoxia in tumor development and the clinical outcome of hypoxia-targeted therapeutics, such as hypoxia-inducible factor (HIF-1) inhibitors and hypoxia-activated prodrugs. Furthermore, we review the state-of-the-art of macrophage-based cancer therapy. We thoroughly discuss the development of novel therapeutics that simultaneously target TAMs and tumor hypoxia. Nano-based systems have been highlighted as interesting strategies for dual modality treatments, with somewhat improved tissue extravasation. Such approach could be seen as a promising strategy to overcome drug resistance and enhance the efficacy of chemotherapy in advanced solid and metastatic tumors, especially when exploiting cell-based nanotherapies. Finally, we provide an in-depth opinion on the importance of exploiting the tumor microenvironment in cancer therapy, and how this could be translated to clinical practice.

Choosing wisely - Preclinical test models in the era of precision medicine

Through the introduction of a steadily growing variety of preclinical test models drug development and biomarker research has advanced. Next to classical used 2D cell line cultures, tissue-slice cultures, 3D organoid cell cultures, genetically engineered mouse models, cell line derived mouse models and patient derived xenografts may be selected for a specific question. All models harbor advantages and disadvantages. This review focuses on the available preclinical test models, novel developments such as humanized mice and discusses for which question a particular model should be employed.

Imaging biomarker roadmap for cancer studies

Imaging biomarkers (IBs) are integral to the routine management of patients with cancer. IBs used daily in oncology include clinical TNM stage, objective response and left ventricular ejection fraction. Other CT, MRI, PET and ultrasonography biomarkers are used extensively in cancer research and drug development. New IBs need to be established either as useful tools for testing research hypotheses in clinical trials and research studies, or as clinical decision-making tools for use in healthcare, by crossing 'translational gaps' through validation and qualification. Important differences exist between IBs and biospecimen-derived biomarkers and, therefore, the development of IBs requires a tailored 'roadmap'. Recognizing this need, Cancer Research UK (CRUK) and the European Organisation for Research and Treatment of Cancer (EORTC) assembled experts to review, debate and summarize the challenges of IB validation and qualification. This consensus group has produced 14 key recommendations for accelerating the clinical translation of IBs, which highlight the role of parallel (rather than sequential) tracks of technical (assay) validation, biological/clinical validation and assessment of cost-effectiveness; the need for IB standardization and accreditation systems; the need to continually revisit IB precision; an alternative framework for biological/clinical validation of IBs; and the essential requirements for multicentre studies to qualify IBs for clinical use.

Overview of the Use of Murine Models in Leukemia and Lymphoma Research

Murine models have been adopted as a significant and powerful tool in the study of cancer. The applications of murine models of cancer are numerous: mechanism discovery, oncogenesis, molecular genetics, microenvironment, metastasis, and therapeutic efficacy. Leukemias and lymphomas are a group of highly heterogeneous hematologic malignancies that affect people of all ages and ethnicities. Leukemia and lymphoma arise from hematopoietic and immune cells and usually spread widely throughout the body. The liquid nature of many of these malignancies, as well as the complex microenvironment from which they arise and their multifaceted genetic basis, has added to the difficulty in generating appropriate and translational models to study them. Murine models of leukemia and lymphoma have made substantial contributions to our understanding of the pathobiology of these disorders in humans. However, while there are many advantages to these models, limitations remain. In this review, we discuss the mouse as a model to study leukemia and lymphoma, and the importance of choosing the correct methodology. Specific examples of murine models of leukemias and lymphomas are provided, with particular attention to those that are highly translational to their human counterpart. Finally, future applications of murine models and potential for better models are discussed.

Modeling nasopharyngeal carcinoma in three dimensions

Nasopharyngeal carcinoma (NPC) is a type of cancer endemic in Asia, including Malaysia, Southern China, Hong Kong and Taiwan. Treatment resistance, particularly in recurring cases, remains a challenge. Thus, studies to develop novel therapeutic agents are important. Potential therapeutic compounds may be effectively examined using two-dimensional (2D) cell culture models, three-dimensional (3D) spheroid models or in vivo animal models. The majority of drug assessments for cancers, including for NPC, are currently performed with 2D cell culture models. This model offers economical and high-throughput screening advantages. However, 2D cell culture models cannot recapitulate the architecture and the microenvironment of a tumor. In vivo models may recapitulate certain architectural and microenvironmental conditions of a tumor, however, these are not feasible for the screening of large numbers of compounds. By contrast, 3D spheroid models may be able to recapitulate a physiological microenvironment not observed in 2D cell culture models, in addition to avoiding the impediments of in vivo animal models. Thus, the 3D spheroid model offers a more representative model for the study of NPC growth, invasion and drug response, which may be cost-effective without forgoing quality.

Murine Tumor Models for Oncolytic Rhabdo-Virotherapy

The preclinical optimization and validation of novel treatments for cancer therapy requires the use of laboratory animals. Although in vitro experiments using tumor cell lines and ex vivo treatment of patient tumor samples provide a remarkable first-line tool for the initial study of tumoricidal potential, tumor-bearing animals remain the primary option to study delivery, efficacy, and safety of therapies in the context of a complete tumor microenvironment and functional immune system. In this review, we will describe the use of murine tumor models for oncolytic virotherapy using vesicular stomatitis virus. We will discuss studies using immunocompetent and immunodeficient models with respect to toxicity and therapeutic treatments, as well as the various techniques and tools available to study cancer therapy with Rhabdoviruses.

Docetaxel-Loaded PLGA Nanoparticles Improve Efficacy in Taxane-Resistant Triple-Negative Breast Cancer

Novel treatment strategies, including nanomedicine, are needed for improving management of triple-negative breast cancer. Patients with triple-negative breast cancer, when considered as a group, have a worse outcome after chemotherapy than patients with breast cancers of other subtypes, a finding that reflects the intrinsically adverse prognosis associated with the disease. The aim of this study was to improve the efficacy of docetaxel by incorporation into a novel nanoparticle platform for the treatment of taxane-resistant triple-negative breast cancer. Rod-shaped nanoparticles encapsulating docetaxel were fabricated using an imprint lithography based technique referred to as Particle Replication in Nonwetting Templates (PRINT). These rod-shaped PLGA-docetaxel nanoparticles were tested in the C3(1)-T-antigen (C3Tag) genetically engineered mouse model (GEMM) of breast cancer that represents the basal-like subtype of triple-negative breast cancer and is resistant to therapeutics from the taxane family. This GEMM recapitulates the genetics of the human disease and is reflective of patient outcome and, therefore, better represents the clinical impact of new therapeutics. Pharmacokinetic analysis showed that delivery of these PLGA-docetaxel nanoparticles increased docetaxel circulation time and provided similar docetaxel exposure to tumor compared to the clinical formulation of docetaxel, Taxotere. These PLGA-docetaxel nanoparticles improved tumor growth inhibition and significantly increased median survival time. This study demonstrates the potential of nanotechnology to improve the therapeutic index of chemotherapies and rescue therapeutic efficacy to treat nonresponsive cancers.

Cancer nanomedicine: progress, challenges and opportunities

The intrinsic limits of conventional cancer therapies prompted the development and application of various nanotechnologies for more effective and safer cancer treatment, herein referred to as cancer nanomedicine. Considerable technological success has been achieved in this field, but the main obstacles to nanomedicine becoming a new paradigm in cancer therapy stem from the complexities and heterogeneity of tumour biology, an incomplete understanding of nano-bio interactions and the challenges regarding chemistry, manufacturing and controls required for clinical translation and commercialization. This Review highlights the progress, challenges and opportunities in cancer nanomedicine and discusses novel engineering approaches that capitalize on our growing understanding of tumour biology and nano-bio interactions to develop more effective nanotherapeutics for cancer patients.

De-Risking Immunotherapy: Report of a Consensus Workshop of the Cancer Immunotherapy Consortium of the Cancer Research Institute

With the recent FDA approvals of pembrolizumab and nivolumab, and a host of additional immunomodulatory agents entering clinical development each year, the field of cancer immunotherapy is changing rapidly. Strategies that can assist researchers in choosing the most promising drugs and drug combinations to move forward through clinical development are badly needed in order to reduce the likelihood of late-stage clinical trial failures. On October 5, 2014, the Cancer Immunotherapy Consortium of the Cancer Research Institute, a collaborative think tank composed of stakeholders from academia, industry, regulatory agencies, and patient interest groups, met to discuss strategies for de-risking immunotherapy development, with a focus on integrating preclinical and clinical studies, and conducting smarter early-phase trials, particularly for combination therapies. Several recommendations were made, including making better use of clinical data to inform preclinical research, obtaining adequate tissues for biomarker studies, and choosing appropriate clinical trial endpoints to identify promising drug candidates and combinations in nonrandomized early-phase trials.

Mouse models in oncoimmunology

Fundamental cancer research and the development of efficacious antineoplastic treatments both rely on experimental systems in which the relationship between malignant cells and immune cells can be studied. Mouse models of transplantable, carcinogen-induced or genetically engineered malignancies - each with their specific advantages and difficulties - have laid the foundations of oncoimmunology. These models have guided the immunosurveillance theory that postulates that evasion from immune control is an essential feature of cancer, the concept that the long-term effects of conventional cancer treatments mostly rely on the reinstatement of anticancer immune responses and the preclinical development of immunotherapies, including currently approved immune checkpoint blockers. Specific aspects of pharmacological development, as well as attempts to personalize cancer treatments using patient-derived xenografts, require the development of mouse models in which murine genes and cells are replaced with their human equivalents. Such 'humanized' mouse models are being progressively refined to characterize the leukocyte subpopulations that belong to the innate and acquired arms of the immune system as they infiltrate human cancers that are subjected to experimental therapies. We surmise that the ever-advancing refinement of murine preclinical models will accelerate the pace of therapeutic optimization in patients.

Translational modeling and simulation approaches for molecularly targeted small molecule anticancer agents from bench to bedside

INTRODUCTION

Recent advances in molecular biology have enabled personalized cancer therapies with molecularly targeted agents (MTAs), which offer a promising future for cancer therapy. Dynamic modeling and simulation (M&S) is a powerful mathematical approach linking drug exposures to pharmacological responses, providing a quantitative assessment of in vivo drug potency. Accordingly, a growing emphasis is being placed upon M&S to quantitatively understand therapeutic exposure-response relationships of MTAs in nonclinical models.

AREAS COVERED

An overview of M&S approaches for MTAs in nonclinical models is presented with discussion about mechanistic extrapolation of antitumor efficacy from bench to bedside. Emphasis is placed upon recent advances in M&S approaches linking drug exposures, biomarker responses (e.g. target modulation) and pharmacological outcomes (e.g. antitumor efficacy).

EXPERT OPINION

For successful personalized cancer therapies with MTAs, it is critical to mechanistically and quantitatively understand their exposure-response relationships in nonclinical models, and to logically and properly apply such knowledge to the clinic. Particularly, M&S approaches to predict pharmacologically active concentrations of MTAs in patients based upon nonclinical data would be highly valuable in guiding the design and execution of clinical trials. Proactive approaches to understand their exposure-response relationships could substantially increase probability of achieving a positive proof-of-concept in the clinic.

Preclinical and Clinical Assessment of Cannabinoids as Anti-Cancer Agents

Cancer is the second leading cause of death in the United States with 1.7 million new cases estimated to be diagnosed in 2016. This disease remains a formidable clinical challenge and represents a substantial financial burden to the US health care system. Therefore, research and development of novel therapeutics for the treatment of cancer is of high priority. Cannabinoids and their derivatives have been utilized for their medicinal and therapeutic properties throughout history. Cannabinoid activity is regulated by the endocannabinoid system (ECS), which is comprised of cannabinoid receptors, transporters, and enzymes involved in cannabinoid synthesis and breakdown. More recently, cannabinoids have gained special attention for their role in cancer cell proliferation and death. However, many studies investigated these effects using in vitro models which may not adequately mimic tumor growth and metastasis. As such, this article aims to review study results which evaluated effects of cannabinoids from plant, synthetic and endogenous origins on cancer development in preclinical animal models and to examine the current standing of cannabinoids that are being tested in human cancer patients.

Clinical development of new drug-radiotherapy combinations

In countries with the best cancer outcomes, approximately 60% of patients receive radiotherapy as part of their treatment, which is one of the most cost-effective cancer treatments. Notably, around 40% of cancer cures include the use of radiotherapy, either as a single modality or combined with other treatments. Radiotherapy can provide enormous benefit to patients with cancer. In the past decade, significant technical advances, such as image-guided radiotherapy, intensity-modulated radiotherapy, stereotactic radiotherapy, and proton therapy enable higher doses of radiotherapy to be delivered to the tumour with significantly lower doses to normal surrounding tissues. However, apart from the combination of traditional cytotoxic chemotherapy with radiotherapy, little progress has been made in identifying and defining optimal targeted therapy and radiotherapy combinations to improve the efficacy of cancer treatment. The National Cancer Research Institute Clinical and Translational Radiotherapy Research Working Group (CTRad) formed a Joint Working Group with representatives from academia, industry, patient groups and regulatory bodies to address this lack of progress and to publish recommendations for future clinical research. Herein, we highlight the Working Group's consensus recommendations to increase the number of novel drugs being successfully registered in combination with radiotherapy to improve clinical outcomes for patients with cancer.

Transplantation in zebrafish

Tissue or cell transplantation is an invaluable technique with a multitude of applications including studying the developmental potential of certain cell populations, dissecting cell-environment interactions, and identifying stem cells. One key technical requirement for performing transplantation assays is the capability of distinguishing the transplanted donor cells from the endogenous host cells and tracing the donor cells over time. The zebrafish has emerged as an excellent model organism for performing transplantation assays, thanks in part to the transparency of embryos and even adults when pigment mutants are employed. Using transgenic techniques and fast-evolving imaging technology, fluorescence-labeled donor cells can be readily identified and studied during development in vivo. In this chapter, we will discuss the rationale of different types of zebrafish transplantation in both embryos and adults and then focus on four detailed methods of transplantation: blastula/gastrula transplantation for mosaic analysis, hematopoietic stem cell transplantation, chemical screening using a transplantation model, and tumor transplantation.

NSG Mice Provide a Better Spontaneous Model of Breast Cancer Metastasis than Athymic (Nude) Mice

Metastasis is the most common cause of mortality in breast cancer patients worldwide. To identify improved mouse models for breast cancer growth and spontaneous metastasis, we examined growth and metastasis of both estrogen receptor positive (T47D) and negative (MDA-MB-231, SUM1315, and CN34BrM) human breast cancer cells in nude and NSG mice. Both primary tumor growth and spontaneous metastases were increased in NSG mice compared to nude mice. In addition, a pattern of metastasis similar to that observed in human breast cancer patients (metastases to the lungs, liver, bones, brain, and lymph nodes) was found in NSG mice. Furthermore, there was an increase in the metastatic burden in NSG compared to nude mice that were injected with MDA-MB-231 breast cancer cells in an intracardiac experimental metastasis model. This data demonstrates that NSG mice provide a better model for studying human breast cancer metastasis compared to the current nude mouse model.

Normoxic or hypoxic adaptation in response to antiangiogenic therapy: Clinical implications

In a recent article in Cell Reports, we described a novel mechanism for acquired resistance against new small-molecule antiangiogenic tyrosine-kinase inhibitors (TKIs). Vascular normalization-inducing TKIs block glycolysis and trigger a nutritional stress response in the tumor compartment that induces a (targetable) switch to mitochondrial metabolism. We discuss the implications for clinical/translational studies and suggest areas for future research.

The Zebrafish Xenograft Platform: Evolution of a Novel Cancer Model and Preclinical Screening Tool

Animal xenografts of human cancers represent a key preclinical tool in the field of cancer research. While mouse xenografts have long been the gold standard, investigators have begun to use zebrafish (Danio rerio) xenotransplantation as a relatively rapid, robust and cost-effective in vivo model of human cancers. There are several important methodological considerations in the design of an informative and efficient zebrafish xenotransplantation experiment. Various transgenic fish strains have been created that facilitate microscopic observation, ranging from the completely transparent casper fish to the Tg(fli1:eGFP) fish that expresses fluorescent GFP protein in its vascular tissue. While human cancer cell lines have been used extensively in zebrafish xenotransplantation studies, several reports have also used primary patient samples as the donor material. The zebrafish is ideally suited for transplanting primary patient material by virtue of the relatively low number of cells required for each embryo (between 50 and 300 cells), the absence of an adaptive immune system in the early zebrafish embryo, and the short experimental timeframe (5-7 days). Following xenotransplantation into the fish, cells can be tracked using in vivo or ex vivo measures of cell proliferation and migration, facilitated by fluorescence or human-specific protein expression. Importantly, assays have been developed that allow for the reliable detection of in vivo human cancer cell growth or inhibition following administration of drugs of interest. The zebrafish xenotransplantation model is a unique and effective tool for the study of cancer cell biology.

Human Organotypic Lung Tumor Models: Suitable For Preclinical 18F-FDG PET-Imaging

Development of predictable in vitro tumor models is a challenging task due to the enormous complexity of tumors in vivo. The closer the resemblance of these models to human tumor characteristics, the more suitable they are for drug-development and –testing. In the present study, we generated a complex 3D lung tumor test system based on acellular rat lungs. A decellularization protocol was established preserving the architecture, important ECM components and the basement membrane of the lung. Human lung tumor cells cultured on the scaffold formed cluster and exhibited an up-regulation of the carcinoma-associated marker mucin1 as well as a reduced proliferation rate compared to respective 2D culture. Additionally, employing functional imaging with 2-deoxy-2-[¹⁸F]fluoro-D-glucose positron emission tomography (FDG-PET) these tumor cell cluster could be detected and tracked over time. This approach allowed monitoring of a targeted tyrosine kinase inhibitor treatment in the in vitro lung tumor model non-destructively. Surprisingly, FDG-PET assessment of single tumor cell cluster on the same scaffold exhibited differences in their response to therapy, indicating heterogeneity in the lung tumor model. In conclusion, our complex lung tumor test system features important characteristics of tumors and its microenvironment and allows monitoring of tumor growth and -metabolism in combination with functional imaging. In longitudinal studies, new therapeutic approaches and their long-term effects can be evaluated to adapt treatment regimes in future.

INFRAFRONTIER: a European resource for studying the functional basis of human disease

Ageing research and more generally the study of the functional basis of human diseases profit enormously from the large-scale approaches and resources in mouse functional genomics: systematic targeted mutation of the mouse genome, systemic phenotyping in mouse clinics, and the archiving and distribution of the mouse resources in public repositories. INFRAFRONTIER, the European research infrastructure for the development, systemic phenotyping, archiving and distribution of mammalian models, offers access to sustainable mouse resources for biomedical research. INFRAFRONTIER promotes the global sharing of high-quality resources and data and thus contributes to data reproducibility and animal welfare. INFRAFRONTIER puts great effort into international standardisation and quality control and into technology development to improve and expand experimental protocols, reduce the use of animals in research and increase the reproducibility of results. In concert with the research community and the International Mouse Phenotyping Consortium (IMPC), INFRAFRONTIER is currently developing new pilot platforms and services for the research on ageing and age-related diseases.

Investigating long noncoding RNAs using animal models

The number of long noncoding RNAs (lncRNAs) has grown rapidly; however, our understanding of their function remains limited. Although cultured cells have facilitated investigations of lncRNA function at the molecular level, the use of animal models provides a rich context in which to investigate the phenotypic impact of these molecules. Promising initial studies using animal models demonstrated that lncRNAs influence a diverse number of phenotypes, ranging from subtle dysmorphia to viability. Here, we highlight the diversity of animal models and their unique advantages, discuss the use of animal models to profile lncRNA expression, evaluate experimental strategies to manipulate lncRNA function in vivo, and review the phenotypes attributable to lncRNAs. Despite a limited number of studies leveraging animal models, lncRNAs are already recognized as a notable class of molecules with important implications for health and disease.

Efficacy and Mechanisms of Aerobic Exercise on Cancer Initiation, Progression, and Metastasis: A Critical Systematic Review of In Vivo Preclinical Data

A major objective of the emerging field of exercise-oncology research is to determine the efficacy of, and biological mechanisms by which, aerobic exercise affects cancer incidence, progression, and/or metastasis. There is a strong inverse association between self-reported exercise and the primary incidence of several forms of cancer; similarly, emerging data suggest that exercise exposure after a cancer diagnosis may improve outcomes for early-stage breast, colorectal, or prostate cancer. Arguably, critical next steps in the development of exercise as a candidate treatment in cancer control require preclinical studies to validate the biological efficacy of exercise, identify the optimal "dose", and pinpoint mechanisms of action. To evaluate the current evidence base, we conducted a critical systematic review of in vivo studies investigating the effects of exercise in cancer prevention and progression. Studies were evaluated on the basis of tumor outcomes (e.g., incidence, growth, latency, metastasis), dose-response, and mechanisms of action, when available. A total of 53 studies were identified and evaluated on tumor incidence (n = 24), tumor growth (n = 33), or metastasis (n = 10). We report that the current evidence base is plagued by considerable methodologic heterogeneity in all aspects of study design, endpoints, and efficacy. Such heterogeneity precludes meaningful comparisons and conclusions at present. To this end, we provide a framework of methodologic and data reporting standards to strengthen the field to guide the conduct of high-quality studies required to inform translational, mechanism-driven clinical trials. Cancer Res; 76(14); 4032-50. ©2016 AACR.

Manipulation of DNA Repair Proficiency in Mouse Models of Colorectal Cancer

Technical and biological innovations have enabled the development of more sophisticated and focused murine models that increasingly recapitulate the complex pathologies of human diseases, in particular cancer. Mouse models provide excellent in vivo systems for deciphering the intricacies of cancer biology within the context of precise experimental settings. They present biologically relevant, adaptable platforms that are amenable to continual improvement and refinement. We discuss how recent advances in our understanding of tumorigenesis and the underlying deficiencies of DNA repair mechanisms that drive it have been informed by using genetically engineered mice to create defined, well-characterized models of human colorectal cancer. In particular, we focus on how mechanisms of DNA repair can be manipulated precisely to create in vivo models whereby the underlying processes of tumorigenesis are accelerated or attenuated, dependent on the composite alleles carried by the mouse model. Such models have evolved to the stage where they now reflect the initiation and progression of sporadic cancers. The review is focused on mouse models of colorectal cancer and how insights from these models have been instrumental in shaping our understanding of the processes and potential therapies for this disease.

Targeting Tumor Mitochondrial Metabolism Overcomes Resistance to Antiangiogenics

Epithelial malignancies are effectively treated by antiangiogenics; however, acquired resistance is a major problem in cancer therapeutics. Epithelial tumors commonly have mutations in the MAPK/Pi3K-AKT pathways, which leads to high-rate aerobic glycolysis. Here, we show how multikinase inhibitor antiangiogenics (TKIs) induce hypoxia correction in spontaneous breast and lung tumor models. When this happens, the tumors downregulate glycolysis and switch to long-term reliance on mitochondrial respiration. A transcriptomic, metabolomic, and phosphoproteomic study revealed that this metabolic switch is mediated by downregulation of HIF1α and AKT and upregulation of AMPK, allowing uptake and degradation of fatty acids and ketone bodies. The switch renders mitochondrial respiration necessary for tumor survival. Agents like phenformin or ME344 induce synergistic tumor control when combined with TKIs, leading to metabolic synthetic lethality. Our study uncovers mechanistic insights in the process of tumor resistance to TKIs and may have clinical applicability.

Predictive In Vivo Models for Oncology

Experimental oncology research and preclinical drug development both substantially require specific, clinically relevant in vitro and in vivo tumor models. The increasing knowledge about the heterogeneity of cancer requested a substantial restructuring of the test systems for the different stages of development. To be able to cope with the complexity of the disease, larger panels of patient-derived tumor models have to be implemented and extensively characterized. Together with individual genetically engineered tumor models and supported by core functions for expression profiling and data analysis, an integrated discovery process has been generated for predictive and personalized drug development.Improved “humanized” mouse models should help to overcome current limitations given by xenogeneic barrier between humans and mice. Establishment of a functional human immune system and a corresponding human microenvironment in laboratory animals will strongly support further research.Drug discovery, systems biology, and translational research are moving closer together to address all the new hallmarks of cancer, increase the success rate of drug development, and increase the predictive value of preclinical models.

Design and Reporting of Targeted Anticancer Preclinical Studies: A Meta-Analysis of Animal Studies Investigating Sorafenib Antitumor Efficacy

The validity of preclinical studies of candidate therapeutic agents has been questioned given their limited ability to predict their fate in clinical development, including due to design flaws and reporting bias. In this study, we examined this issue in depth by conducting a meta-analysis of animal studies investigating the efficacy of the clinically approved kinase inhibitor, sorafenib. MEDLINE, Embase, and BIOSIS databases were searched for all animal experiments testing tumor volume response to sorafenib monotherapy in any cancer published until April 20, 2012. We estimated effect sizes from experiments assessing changes in tumor volume and conducted subgroup analyses based on prespecified experimental design elements associated with internal, construct, and external validity. The meta-analysis included 97 experiments involving 1,761 animals. We excluded 94 experiments due to inadequate reporting of data. Design elements aimed at reducing internal validity threats were implemented only sporadically, with 66% reporting animal attrition and none reporting blinded outcome assessment or concealed allocation. Anticancer activity against various malignancies was typically tested in only a small number of model systems. Effect sizes were significantly smaller when sorafenib was tested against either a different active agent or combination arm. Trim and fill suggested a 37% overestimation of effect sizes across all malignancies due to publication bias. We detected a moderate dose-response in one clinically approved indication, hepatocellular carcinoma, but not in another approved malignancy, renal cell carcinoma, or when data were pooled across all malignancies tested. In support of other reports, we found that few preclinical cancer studies addressed important internal, construct, and external validity threats, limiting their clinical generalizability. Our findings reinforce the need to improve guidelines for the design and reporting of preclinical cancer studies. Cancer Res; 76(16); 4627-36. ©2016 AACR.

Mouse Models of Breast Cancer: Platforms for Discovering Precision Imaging Diagnostics and Future Cancer Medicine

Representing an enormous health care and socioeconomic challenge, breast cancer is the second most common cancer in the world and the second most common cause of cancer-related death. Although many of the challenges associated with preventing, treating, and ultimately curing breast cancer are addressable in the laboratory, successful translation of groundbreaking research to clinical populations remains an important barrier. Particularly when compared with research on other types of solid tumors, breast cancer research is hampered by a lack of tractable in vivo model systems that accurately recapitulate the relevant clinical features of the disease. A primary objective of this article was to provide a generalizable overview of the types of in vivo model systems, with an emphasis primarily on murine models, that are widely deployed in preclinical breast cancer research. Major opportunities to advance precision cancer medicine facilitated by molecular imaging of preclinical breast cancer models are discussed.

Mounting Pressure in the Microenvironment: Fluids, Solids, and Cells in Pancreatic Ductal Adenocarcinoma

The microenvironment influences the pathogenesis of solid tumors and plays an outsized role in some. Our understanding of the stromal response to cancers, particularly pancreatic ductal adenocarcinoma, has evolved from that of host defense to tumor offense. We know that most, although not all, of the factors and processes in the microenvironment support tumor epithelial cells. This reappraisal of the roles of stromal elements has also revealed potential vulnerabilities and therapeutic opportunities to exploit. The high concentration in the stroma of the glycosaminoglycan hyaluronan, together with the large gel-fluid phase and pressures it generates, were recently identified as primary sources of treatment resistance in pancreas cancer. Whereas the relatively minor role of free interstitial fluid in the fluid mechanics and perfusion of tumors has been long appreciated, the less mobile, gel-fluid phase has been largely ignored for historical and technical reasons. The inability of classic methods of fluid pressure measurement to capture the gel-fluid phase, together with a dependence on xenograft and allograft systems that inaccurately model tumor vascular biology, has led to an undue emphasis on the role of free fluid in impeding perfusion and drug delivery and an almost complete oversight of the predominant role of the gel-fluid phase. We propose that a hyaluronan-rich, relatively immobile gel-fluid phase induces vascular collapse and hypoperfusion as a primary mechanism of treatment resistance in pancreas cancers. Similar properties may be operant in other solid tumors as well, so revisiting and characterizing fluid mechanics with modern techniques in other autochthonous cancers may be warranted.

A Decade of Experience in Developing Preclinical Models of Advanced- or Early-Stage Spontaneous Metastasis to Study Antiangiogenic Drugs, Metronomic Chemotherapy, and the Tumor Microenvironment

The clinical circumstance of treating spontaneous metastatic disease, after resection of primary tumors, whether advanced/overt or microscopic in nature, is seldom modeled in mice and may be a major factor in explaining the frequent discordance between preclinical and clinical therapeutic outcomes where the trend is "overprediction" of positive results in preclinical mouse model studies. To evaluate this hypothesis, a research program was initiated a decade ago to develop multiple models of metastasis in mice, using variants of human tumor cell lines selected in vivo for enhanced spontaneous metastatic aggressiveness after surgical resection of established orthotopic primary tumors. These models have included breast, renal, and colorectal carcinomas; ovarian cancer (but without prior surgery); and malignant melanoma. They have been used primarily for experimental therapeutic investigations involving various antiangiogenic drugs alone or with chemotherapy, especially "metronomic" low-dose chemotherapy. The various translational studies undertaken have revealed a number of clinically relevant findings. These include the following: (i) the potential of metronomic chemotherapy, especially when combined with a vascular endothelial growth factor pathway targeting drug to successfully treat advanced metastatic disease; (ii) the development of relapsed spontaneous brain metastases in mice with melanoma or breast cancer whose systemic metastatic disease is successfully controlled for a period with a given therapy; (iii) foreshadowing the failure of adjuvant antiangiogenic drug-based phase III trials; (iv) recapitulating the failure of oral antiangiogenic tyrosine kinase inhibitors plus standard chemotherapy in contrast to the modest successes of antiangiogenic antibodies plus chemotherapy in metastatic breast cancer; and (v) revealing "vessel co-option" and absence of angiogenesis as a determinant of intrinsic resistance or minimal responsiveness to antiangiogenic therapy in lung metastases. Developing similar models of metastatic disease but involving mouse tumors grown in syngeneic immunocompetent mice may also prove useful for future translational studies of immune therapy-based treatments.

Computational Identification of Key Regulators in Two Different Colorectal Cancer Cell Lines

Transcription factors (TFs) are gene regulatory proteins that are essential for an effective regulation of the transcriptional machinery. Today, it is known that their expression plays an important role in several types of cancer. Computational identification of key players in specific cancer cell lines is still an open challenge in cancer research. In this study, we present a systematic approach which combines colorectal cancer (CRC) cell lines, namely 1638N-T1 and CMT-93, and well-established computational methods in order to compare these cell lines on the level of transcriptional regulation as well as on a pathway level, i.e., the cancer cell-intrinsic pathway repertoire. For this purpose, we firstly applied the Trinity platform to detect signature genes, and then applied analyses of the geneXplain platform to these for detection of upstream transcriptional regulators and their regulatory networks. We created a CRC-specific position weight matrix (PWM) library based on the TRANSFAC database (release 2014.1) to minimize the rate of false predictions in the promoter analyses. Using our proposed workflow, we specifically focused on revealing the similarities and differences in transcriptional regulation between the two CRC cell lines, and report a number of well-known, cancer-associated TFs with significantly enriched binding sites in the promoter regions of the signature genes. We show that, although the signature genes of both cell lines show no overlap, they may still be regulated by common TFs in CRC. Based on our findings, we suggest that canonical Wnt signaling is activated in 1638N-T1, but inhibited in CMT-93 through cross-talks of Wnt signaling with the VDR signaling pathway and/or LXR-related pathways. Furthermore, our findings provide indication of several master regulators being present such as MLK3 and Mapk1 (ERK2) which might be important in cell proliferation, migration, and invasion of 1638N-T1 and CMT-93, respectively. Taken together, we provide new insights into the invasive potential of these cell lines, which can be used for development of effective cancer therapy.

Efficacy of targeted AKT inhibition in genetically engineered mouse models of PTEN-deficient prostate cancer

The PI3K/AKT pathway is frequently altered in advanced human prostate cancer mainly through the loss of functional PTEN, and presents as potential target for personalized therapy. Our aim was to determine the therapeutic potential of the pan-AKT inhibitor, AZD5363, in PTEN-deficient prostate cancer. Here we used a genetically engineered mouse (GEM) model of PTEN-deficient prostate cancer to evaluate the in vivo pharmacodynamic and antitumor activity of AZD5363 in castration-naïve and castration-resistant prostate cancer. An additional GEM model, based on the concomitant inactivation of PTEN and Trp53 (P53), was established as an aggressive model of advanced prostate cancer and was used to further evaluate clinically relevant endpoints after treatment with AZD5363. In vivo pharmacodynamic studies demonstrated that AZD5363 effectively inhibited downstream targets of AKT. AZD5363 monotherapy significantly reduced growth of tumors in castration-naïve and castration-resistant models of PTEN-deficient prostate cancer. More importantly, AZD5363 significantly delayed tumor growth and improved overall survival and progression-free survival in PTEN/P53 double knockout mice. Our findings demonstrate that AZD5363 is effective against GEM models of PTEN-deficient prostate cancer and provide lines of evidence to support further investigation into the development of treatment strategies targeting AKT for the treatment of PTEN-deficient prostate cancer.

Emerging Roles of Epigenetic Regulator Sin3 in Cancer

Revolutionizing treatment strategies is an urgent clinical need in the fight against cancer. Recently the scientific community has recognized chromatin-associated proteins as promising therapeutic candidates. However, there is a need to develop more targeted epigenetic inhibitors with less toxicity. Sin3 family is one such target which consists of evolutionary conserved proteins with two paralogues Sin3A and Sin3B. Sin3A/B are global transcription regulators that provide a versatile platform for diverse chromatin-modifying activities. Sin3 proteins regulate key cellular functions that include cell cycle, proliferation, and differentiation, and have recently been implicated in cancer pathogenesis. In this chapter, we summarize the key concepts of Sin3 biology and elaborate the recent advancements in the role of Sin3 proteins in cancer with specific examples in multiple endocrine neoplasia type 2, pancreatic ductal adenocarcinoma, and triple negative breast cancer. Finally, a program to create an integrative approach for screening antitumor agents that target chromatin-associated factors like Sin3 is presented.

Optimizing mouse models for precision cancer prevention

As cancer has become increasingly prevalent, cancer prevention research has evolved towards placing a greater emphasis on reducing cancer deaths and minimizing the adverse consequences of having cancer. 'Precision cancer prevention' takes into account the collaboration of intrinsic and extrinsic factors in influencing cancer incidence and aggressiveness in the context of the individual, as well as recognizing that such knowledge can improve early detection and enable more accurate discrimination of cancerous lesions. However, mouse models, and particularly genetically engineered mouse (GEM) models, have yet to be fully integrated into prevention research. In this Opinion article, we discuss opportunities and challenges for precision mouse modelling, including the essential criteria of mouse models for prevention research, representative success stories and opportunities for more refined analyses in future studies.

Defining the optimal murine models to investigate immune checkpoint blockers and their combination with other immunotherapies

The recent success of checkpoint blockers to treat cancer has demonstrated that the immune system is a critical player in the war against cancer. Historically, anticancer therapeutics have been tested in syngeneic mouse models (with a fully murine immune system) or in immunodeficient mice that allow the engraftment of human xenografts. Animal models with functioning human immune systems are critically needed to more accurately recapitulate the complexity of the human tumor microenvironment. Such models are integral to better predict tumor responses to both immunomodulatory agents and directly antineoplastic therapies. In this regard, the development of humanized models is a promising, novel strategy that offers the possibility of testing checkpoint blockers' capacity and their combination with other antitumor drugs. In this review, we discuss the strengths and weaknesses of the available animal models regarding their capacity to evaluate checkpoint blockers and checkpoint blocker-based combination immunotherapy.