From Mice to Men and Back: An Assessment of Preclinical Model Systems for the Study of Lung Cancers

The progressive trend of modeling and drug screening systems of breast cancer bone metastasis

Bone metastasis is considered as a considerable challenge for breast cancer patients. Various in vitro and in vivo models have been developed to examine this occurrence. In vitro models are employed to simulate the intricate tumor microenvironment, investigate the interplay between cells and their adjacent microenvironment, and evaluate the effectiveness of therapeutic interventions for tumors. The endeavor to replicate the latency period of bone metastasis in animal models has presented a challenge, primarily due to the necessity of primary tumor removal and the presence of multiple potential metastatic sites.The utilization of novel bone metastasis models, including three-dimensional (3D) models, has been proposed as a promising approach to overcome the constraints associated with conventional 2D and animal models. However, existing 3D models are limited by various factors, such as irregular cellular proliferation, autofluorescence, and changes in genetic and epigenetic expression. The imperative for the advancement of future applications of 3D models lies in their standardization and automation. The utilization of artificial intelligence exhibits the capability to predict cellular behavior through the examination of substrate materials' chemical composition, geometry, and mechanical performance. The implementation of these algorithms possesses the capability to predict the progression and proliferation of cancer. This paper reviewed the mechanisms of bone metastasis following primary breast cancer. Current models of breast cancer bone metastasis, along with their challenges, as well as the future perspectives of using these models for translational drug development, were discussed.

Lack of racial and ethnic diversity in lung cancer cell lines contributes to lung cancer health disparities

Lung cancer is the leading cause of cancer death in the United States and worldwide, and a major source of cancer health disparities. Lung cancer cell lines provide key in vitro models for molecular studies of lung cancer development and progression, and for pre-clinical drug testing. To ensure health equity, it is imperative that cell lines representing different lung cancer histological types, carrying different cancer driver genes, and representing different genders, races, and ethnicities should be available. This is particularly relevant for cell lines from Black men, who experience the highest lung cancer mortality in the United States. Here, we undertook a review of the available lung cancer cell lines and their racial and ethnic origin. We noted a marked imbalance in the availability of cell lines from different races and ethnicities. Cell lines from Black patients were strongly underrepresented, and we identified no cell lines from Hispanic/Latin(x) (H/L), American Indian/American Native (AI/AN), or Native Hawaiian or other Pacific Islander (NHOPI) patients. The majority of cell lines were derived from White and Asian patients. Also missing are cell lines representing the cells-of-origin of the major lung cancer histological types, which can be used to model lung cancer development and to study the effects of environmental exposures on lung tissues. To our knowledge, the few available immortalized alveolar epithelial cell lines are all derived from White subjects, and the race and ethnicity of a handful of cell lines derived from bronchial epithelial cells are unknown. The lack of an appropriately diverse collection of lung cancer cell lines and lung cancer cell-of-origin lines severely limits racially and ethnically inclusive lung cancer research. It impedes the ability to develop inclusive models, screen comprehensively for effective compounds, pre-clinically test new drugs, and optimize precision medicine. It thereby hinders the development of therapies that can increase the survival of minority and underserved patients. The noted lack of cell lines from underrepresented groups should constitute a call to action to establish additional cell lines and ensure adequate representation of all population groups in this critical pre-clinical research resource.

Progress in construction of mouse models to investigate the pathogenesis and immune therapy of human hematological malignancy

Hematological malignancy is a disease arisen by complicate reasons that seriously endangers human health. The research on its pathogenesis and therapies depends on the usage of animal models. Conventional animal model cannot faithfully mirror some characteristics of human features due to the evolutionary divergence, whereas the mouse models hosting human hematological malignancy are more and more applied in basic as well as translational investigations in recent years. According to the construction methods, they can be divided into different types (e.g. cell-derived xenograft (CDX) and patient-derived xenograft model (PDX) model) that have diverse characteristics and application values. In addition, a variety of strategies have been developed to improve human hematological malignant cell engraftment and differentiation in vivo. Moreover, the humanized mouse model with both functional human immune system and autologous human hematological malignancy provides a unique tool for the evaluation of the efficacy of novel immunotherapeutic drugs/approaches. Herein, we first review the evolution of the mouse model of human hematological malignancy; Then, we analyze the characteristics of different types of models and summarize the ways to improve the models; Finally, the way and value of humanized mouse model of human immune system in the immunotherapy of human hematological malignancy are discussed.

Rb Tumor Suppressor in Small Cell Lung Cancer: Combined Genomic and IHC Analysis with a Description of a Distinct Rb-Proficient Subset

PURPOSE

RB1 mutations and loss of retinoblastoma (Rb) expression represent consistent but not entirely invariable hallmarks of small cell lung cancer (SCLC). The prevalence and characteristics of SCLC retaining wild-type Rb are not well-established. Furthermore, the performance of targeted next-generation sequencing (NGS) versus immunohistochemistry for Rb assessment is not well-defined.

EXPERIMENTAL DESIGN

A total of 208 clinical SCLC samples were analyzed by comprehensive targeted NGS, covering all exons of RB1, and Rb IHC. On the basis of established coordination of Rb/p16/cyclinD1 expression, p16-high/cyclinD1-low profile was used as a marker of constitutive Rb deficiency.

RESULTS

Fourteen of 208 (6%) SCLC expressed wild-type Rb, accompanied by a unique p16-low/cyclinD1-high profile supporting Rb proficiency. Rb-proficient SCLC was associated with neuroendocrine-low phenotype, combined SCLC with non-SCLC (NSCLC) histology and aggressive behavior. These tumors exclusively harbored CCND1 amplification (29%), and were markedly enriched in CDKN2A mutations (50%) and NSCLC-type alterations (KEAP1, STK11, FGFR1). The remaining 194 of 208 SCLC were Rb-deficient (p16-high/cyclinD1-low), including 184 cases with Rb loss (of which 29% lacked detectable RB1 alterations by clinical NGS pipeline), and 10 cases with mutated but expressed Rb.

CONCLUSIONS

This is the largest study to date to concurrently analyze Rb by NGS and IHC in SCLC, identifying a 6% rate of Rb proficiency. Pathologic-genomic data implicate NSCLC-related progenitors as a putative source of Rb-proficient SCLC. Consistent upstream Rb inactivation via CDKN2A/p16↓ and CCND1/cyclinD1↑ suggests the potential utility of CDK4/6 inhibitors in this aggressive SCLC subset. The study also clarifies technical aspects of Rb status determination in clinical practice, highlighting the limitations of exon-only sequencing for RB1 interrogation. See related commentary by Mahadevan and Sholl, p. 4603.

Lung Cancer Computational Biology and Resources

Comprehensive clinical, pathological, and molecular data, when appropriately integrated with advanced computational approaches, are transforming the way we characterize and study lung cancer. Clinically, cancer registry and publicly available historical clinical trial data enable retrospective analyses to examine how socioeconomic factors, patient demographics, and cancer characteristics affect treatment and outcome. Pathologically, digital pathology and artificial intelligence are revolutionizing histopathological image analyses, not only with improved efficiency and accuracy, but also by extracting additional information for prognostication and tumor microenvironment characterization. Genetically and molecularly, individual patient tumors and preclinical models of lung cancer are profiled by various high-throughput platforms to characterize the molecular properties and functional liabilities. The resulting multi-omics data sets and their interrogation facilitate both basic research mechanistic studies and translation of the findings into the clinic. In this review, we provide a list of resources and tools potentially valuable for lung cancer basic and translational research. Importantly, we point out pitfalls and caveats when performing computational analyses of these data sets and provide a vision of future computational biology developments that will aid lung cancer translational research.

Comparative microsomal proteomics of a model lung cancer cell line NCI-H23 reveals distinct differences between molecular profiles of 3D and 2D cultured cells

Lung cancer is the leading cause of cancer-related deaths in the USA and worldwide. Yet, about 95% of new drug candidates validated in preclinical phase eventually fail in clinical trials. Such a high attrition rate is attributed mostly to the inability of conventional two-dimensionally (2D) cultured cancer cells to mimic native three-dimensional (3D) growth of malignant cells in human tumors. To ascertain phenotypical differences between these two distinct culture conditions, we carried out a comparative proteomic analysis of a membrane fraction obtained from 3D- and 2D-cultured NSCLC model cell line NCI-H23. This analysis revealed a map of 1,166 (24%) protein species regulated in culture dependent manner, including differential regulation of a subset of cell surface-based CD molecules. We confirmed exclusive expression of CD99, CD146 and CD239 in 3D culture. Furthermore, label-free quantitation, targeting KRas proteoform-specific peptides, revealed upregulation of both wild type and monoallelic KRas4BG12C mutant at the surface of 3D cultured cells. In order to reduce the high attrition rate of new drug candidates, the results of this study strongly suggests exploiting base-line molecular profiling of a large number of patient-derived NSCLC cell lines grown in 2D and 3D culture, prior to actual drug candidate testing.

Mapping lung squamous cell carcinoma pathogenesis through in vitro and in vivo models

Lung cancer is the main cause of cancer death worldwide, with lung squamous cell carcinoma (LUSC) being the second most frequent subtype. Preclinical LUSC models recapitulating human disease pathogenesis are key for the development of early intervention approaches and improved therapies. Here, we review advances and challenges in the generation of LUSC models, from 2D and 3D cultures, to murine models. We discuss how molecular profiling of premalignant lesions and invasive LUSC has contributed to the refinement of in vitro and in vivo models, and in turn, how these systems have increased our understanding of LUSC biology and therapeutic vulnerabilities.

Perspectives of nano-carrier drug delivery systems to overcome cancer drug resistance in the clinics

Advanced cancer is still considered an incurable disease because of its metastatic spread to distal organs and progressive gain of chemoresistance. Even though considerable treatment progress and more effective therapies have been achieved over the past years, recurrence in the long-term and undesired side effects are still the main drawbacks of current clinical protocols. Moreover, a majority of chemotherapeutic drugs are highly hydrophobic and need to be diluted in organic solvents, which cause high toxicity, in order to reach effective therapeutic dose. These limitations of conventional cancer therapies prompted the use of nanomedicine, the medical application of nanotechnology, to provide more effective and safer cancer treatment. Potential of nanomedicines to overcome resistance, ameliorate solubility, improve pharmacological profile, and reduce adverse effects of chemotherapeutical drugs is thus highly regarded. Their use in the clinical setting has increased over the last decade. Among the various existing nanosystems, nanoparticles have the ability to transform conventional medicine by reducing the adverse effects and providing a controlled release of therapeutic agents. Also, their small size facilitates the intracellular uptake. Here, we provide a closer review of clinical prospects and mechanisms of action of nanomedicines to overcome drug resistance. The significance of specific targeting towards cancer cells is debated as well.

Recent advances in preclinical models for lung squamous cell carcinoma

Lung squamous cell carcinoma (LUSC) represents a major subtype of non-small cell lung cancer with limited treatment options. Previous studies have elucidated the complex genetic landscape of LUSC and revealed multiple altered genes and pathways. However, in stark contrast to lung adenocarcinoma, few targetable driver mutations have been established so far and targeted therapies for LUSC remain unsuccessful. Immunotherapy has revolutionized LUSC treatment and is currently approved as the new standard of care. To gain a better understanding of the LUSC biology, improved modeling systems are urgently needed. Preclinical models, particularly those mimicking human disease with an intact tumor immune microenvironment, are an invaluable tool to study cancer development and evaluate new therapeutic targets. Here, we discuss recent advances in LUSC preclinical models, with a focus on genetically engineered mouse models (GEMMs) and organoids, in the context of evolving precision medicine and immunotherapy.

Progress towards non-small-cell lung cancer models that represent clinical evolutionary trajectories

Non-small-cell lung cancer (NSCLC) is the leading cause of cancer-related deaths worldwide. Although advances are being made towards earlier detection and the development of impactful targeted therapies and immunotherapies, the 5-year survival of patients with advanced disease is still below 20%. Effective cancer research relies on pre-clinical model systems that accurately reflect the evolutionary course of disease progression and mimic patient responses to therapy. Here, we review pre-clinical models, including genetically engineered mouse models and patient-derived materials, such as cell lines, primary cell cultures, explant cultures and xenografts, that are currently being used to interrogate NSCLC evolution from pre-invasive disease through locally invasive cancer to the metastatic colonization of distant organ sites.

Neuroendocrine Lung Cancer Mouse Models: An Overview

Simple Summary

Neuroendocrine lung tumors are a heterogeneous group of malignancies that share a common neuroendocrine nature. They range from low- and intermediate-grade typical and atypical carcinoma, to the highly malignant large cell neuroendocrine lung carcinoma and small cell carcinoma, with marked differences in incidences and prognosis. This review delineates the current knowledge of the genetic landscape of the human tumors, its influence in the development of genetically engineered mouse models (GEMMs) and the molecular imaging tools available to detect and monitor these diseases. While small cell lung carcinoma is one of the diseases best represented by GEMMs, there is a worrying lack of animal models for the other members of the group, these being understudied diseases. Regardless of the incidence and material available, they all are in urgent need of effective therapies.

Abstract

Neuroendocrine lung tumors comprise a range of malignancies that extend from benign tumorlets to the most prevalent and aggressive Small Cell Lung Carcinoma (SCLC). They also include low-grade Typical Carcinoids (TC), intermediate-grade Atypical Carcinoids (AC) and high-grade Large Cell Neuroendocrine Carcinoma (LCNEC). Optimal treatment options have not been adequately established: surgical resection when possible is the choice for AC and TC, and for SCLC chemotherapy and very recently, immune checkpoint inhibitors. Some mouse models have been generated based on the molecular alterations identified in genomic analyses of human tumors. With the exception of SCLC, there is a limited availability of (preclinical) models making their development an unmet need for the understanding of the molecular mechanisms underlying these diseases. For SCLC, these models are crucial for translational research and novel drug testing, given the paucity of human material from surgery. The lack of early detection systems for lung cancer point them out as suitable frameworks for the identification of biomarkers at the initial stages of tumor development and for testing molecular imaging methods based on somatostatin receptors. Here, we review the relevant models reported to date, their impact on the understanding of the biology of the tumor subtypes and their relationships, as well as the effect of the analyses of the genetic landscape of the human tumors and molecular imaging tools in their development.

Immortalized normal human lung epithelial cell models for studying lung cancer biology

Primary cultures of human lung epithelial cells are ideal representatives of normal lung epithelial cells, and while there are certain novel approaches for the long-term culture of lung epithelial cells, the cells eventually undergo irreversible growth arrest, limiting their experimental utility, particularly the ability to widely distribute these cultures and their clonal derivatives to the broader research community. Therefore, the establishment of immortalized normal human lung epithelial cell strains has garnered considerable attention. The number and type of oncogenic changes necessary for the tumorigenic transformation of normal cells could be determined using "normal" cell lines immortalized with the simian virus 40 (SV40) large T antigen (LT). A primary report suggested that LT, human telomerase reverse transcriptase (hTERT), and oncogenic RAS transformed normal lung epithelial cells into tumorigenic cells. Since LT inactivates the tumor suppressors p53 and RB, at least four alterations would be necessary. However, the SV40 small T antigen (ST), a different oncoprotein, was also introduced simultaneously with LT in the above-mentioned study. Furthermore, the possible uncharacterized functions of LT remained largely obscure. Therefore, no definitive conclusion could be arrived in these studies. Subsequent studies used methods that did not involve the use of oncoproteins and revealed that at least five genetic changes were necessary for full tumorigenic transformation. hTERT-immortalized normal human lung epithelial cell lines established without using viral oncoproteins were also used for investigating several aspects of lung cancer, such as epithelial to mesenchymal transition and the cancer stem cell theory. The use of immortalized normal lung epithelial cell models has improved our understanding of lung cancer pathogenesis and these models can serve as valuable research tools.

Effects of anti-PD-1 immunotherapy on tumor regression: insights from a patient-derived xenograft model

Immunotherapies, such as checkpoint blockade of programmed cell death protein-1 (PD-1), have resulted in unprecedented improvements in survival for patients with lung cancer. Nonetheless, not all patients benefit equally and many issues remain unresolved, including the mechanisms of action and the possible effector function of immune cells from non-lymphoid lineages. The purpose of this study was to investigate whether anti-PD-1 immunotherapy acts on malignant tumor cells through mechanisms beyond those related to T lymphocyte involvement. We used a murine patient-derived xenograft (PDX) model of early-stage non–small cell lung carcinoma (NSCLC) devoid of host lymphoid cells, and studied the tumor and immune non-lymphoid responses to immunotherapy with anti-PD-1 alone or in combination with standard chemotherapy (cisplatin). An antitumor effect was observed in animals that received anti-PD-1 treatment, alone or in combination with cisplatin, likely due to a mechanism independent of T lymphocytes. Indeed, anti-PD-1 treatment induced myeloid cell mobilization to the tumor concomitant with the production of exudates compatible with an acute inflammatory reaction mediated by murine polymorphonuclear leukocytes, specifically neutrophils. Thus, while keeping in mind that more research is needed to corroborate our findings, we report preliminary evidence for a previously undescribed immunotherapy mechanism in this model, suggesting a potential cytotoxic action of neutrophils as PD-1 inhibitor effector cells responsible for tumor regression by necrotic extension.

A biobank of small cell lung cancer CDX models elucidates inter- and intratumoral phenotypic heterogeneity

Although small cell lung cancer (SCLC) is treated as a homogeneous disease, biopsies and preclinical models reveal heterogeneity in transcriptomes and morphology. SCLC subtypes were recently defined by neuroendocrine transcription factor (NETF) expression. Circulating-tumor-cell-derived explant models (CDX) recapitulate donor patients' tumor morphology, diagnostic NE marker expression and chemotherapy responses. We describe a biobank of 38 CDX models, including six CDX pairs generated pretreatment and at disease progression revealing complex intra- and intertumoral heterogeneity. Transcriptomic analysis confirmed three of four previously described subtypes based on ASCL1, NEUROD1 and POU2F3 expression and identified a previously unreported subtype based on another NETF, ATOH1. We document evolution during disease progression exemplified by altered MYC and NOTCH gene expression, increased 'variant' cell morphology, and metastasis without strong evidence of epithelial to mesenchymal transition. This CDX biobank provides a research resource to facilitate SCLC personalized medicine.

Intensive care for human hearts in pluripotent stem cell models

Successful drug discovery is ultimately contingent on the availability of workable, relevant, predictive model systems. Conversely, for cardiac muscle, the lack of human preclinical models to inform target validation and compound development has likely contributed to the perennial problem of clinical trial failures, despite encouraging non-human results. By contrast, human cardiomyocytes produced from pluripotent stem cell models have recently been applied to safety pharmacology, phenotypic screening, target validation and high-throughput assays, facilitating cardiac drug discovery. Here, we review the impact of human pluripotent stem cell models in cardiac drug discovery, discussing the range of applications, readouts, and disease models employed, along with the challenges and prospects to advance this fruitful mode of research further.

Concomitant deletion of HRAS and NRAS leads to pulmonary immaturity, respiratory failure and neonatal death in mice

We reported previously that adult (HRAS^−/−; NRAS^−/−) double knockout (DKO) mice showed no obvious external phenotype although lower-than-expected numbers of weaned DKO animals were consistently tallied after crossing NRAS-KO and HRAS-KO mice kept on mixed genetic backgrounds. Using mouse strains kept on pure C57Bl/6 background, here we performed an extensive analysis of the offspring from crosses between HRAS-KO and NRAS-KO mice and uncovered the occurrence of very high rates of perinatal mortality of the resulting DKO littermates due to respiratory failure during the first postnatal 24–48 h. The lungs of newborn DKO mice showed normal organ structure and branching but displayed marked defects of maturation including much-reduced alveolar space with thick separating septa and significant alterations of differentiation of alveolar (AT1, AT2 pneumocytes) and bronchiolar (ciliated, Clara cells) cell lineages. We also observed the retention of significantly increased numbers of undifferentiated progenitor precursor cells in distal lung epithelia and the presence of substantial accumulations of periodic acid-Schiff-positive (PAS+) material and ceramide in the lung airways of newborn DKO mice. Interestingly, antenatal dexamethasone treatment partially mitigated the defective lung maturation phenotypes and extended the lifespan of the DKO animals up to 6 days, but was not sufficient to abrogate lethality in these mice. RNA microarray hybridization analyses of the lungs of dexamethasone-treated and untreated mice uncovered transcriptional changes pointing to functional and metabolic alterations that may be mechanistically relevant for the defective lung phenotypes observed in DKO mice. Our data suggest that delayed alveolar differentiation, altered sphingolipid metabolism and ceramide accumulation are primary contributors to the respiratory stress and neonatal lethality shown by DKO mice and uncover specific, critical roles of HRAS and NRAS for correct lung differentiation that are essential for neonatal survival and cannot be substituted by the remaining KRAS function in this organ.

A step towards valid detection and quantification of lung cancer volume in experimental mice with contrast agent-based X-ray microtomography

Tumor volume is a parameter used to evaluate the performance of new therapies in lung cancer research. Conventional methods that are used to estimate tumor size in mouse models fail to provide fast and reliable volumetric data for tumors grown non-subcutaneously. Here, we evaluated the use of iodine-staining combined with micro-computed tomography (micro-CT) to estimate the tumor volume of ex vivo tumor-burdened lungs. We obtained fast high spatial resolution three-dimensional information of the lungs, and we demonstrated that iodine-staining highlights tumors and unhealthy tissue. We processed iodine-stained lungs for histopathological analysis with routine hematoxylin and eosin (H&E) staining. We compared the traditional tumor burden estimation performed manually with H&E histological slices with a semi-automated method using micro-CT datasets. In mouse models that develop lung tumors with well precise boundaries, the method that we describe here enables to perform a quick estimation of tumorous tissue volume in micro-CT images. Our method overestimates the tumor burden in tumors surrounded by abnormal tissue, while traditional histopathological analysis underestimates tumor volume. We propose to embed micro-CT imaging to the traditional workflow of tumorous lung analyses in preclinical cancer research as a strategy to obtain a more accurate estimation of the total lung tumor burden.

Discovery and optimization of a series of 3-substituted indazole derivatives as multi-target kinase inhibitors for the treatment of lung squamous cell carcinoma

Although lung adenocarcinoma patients have benefited from the development of targeted therapy, patients with lung squamous cell carcinoma (SqCC) have no effective treatment due to the complexity and heterogeneity of the disease. Therefore, basing on the genetic analysis of mutations in lung squamous cell carcinoma to design multi-target inhibitors represents a potential strategy for the medical treatment. In this study, through screening an in-house focused library, we identified an interesting indazole scaffold. And following with binding analysis, we elaborated the structure-activity relationship of this hit compound by optimizing four parts guided by the DDR2 enzymatic assay, which resulted in a potent lead compound 10a. We conducted further optimization of dual enzymatic inhibitions towards FGFR1 and DDR2, two important kinases in lung squamous cell carcinoma. Finally, from the cellular antiproliferative activity tests and in vivo pharmacokinetic test, 3-substituted indazole derivative 11k was found to be a promising candidate and subjected to in vivo pharmacology study with the mouse xenograft models, demonstrating profound anti-tumor efficacy. Additional in vitro druglike assessment reinforced that compound 11k could be valuable for SqCC drug development.

Autochthonous murine models for the study of smoker and never-smoker associated lung cancers

Lung cancer accounts for the greatest number of cancer deaths in the world. Tobacco smoke-associated cancers constitute the majority of lung cancer cases but never-smoker cancers comprise a significant and increasing fraction of cases. Recent genomic and transcriptomic sequencing efforts of lung cancers have revealed distinct sets of genetic aberrations of smoker and never-smoker lung cancers that implicate disparate biology and therapeutic strategies. Autochthonous mouse models have contributed greatly to our understanding of lung cancer biology and identified novel therapeutic targets and strategies in the era of targeted therapy. With the emergence of immuno-oncology, mouse models may continue to serve as valuable platforms for novel biological insights and therapeutic strategies. Here, we will review the variety of available autochthonous mouse models of lung cancer, their relation to human smoker and never-smoker lung cancers, and their application to immuno-oncology and immune checkpoint blockade that is revolutionizing lung cancer therapy.

ETS1 regulates Twist1 transcription in a KrasG12D/Lkb1-/- metastatic lung tumor model of non-small cell lung cancer

Distinct members of the Ets family of transcription factors act as positive or negative regulators of genes involved in cellular proliferation, development, and tumorigenesis. In human lung cancer, increased ETS1 expression is associated with poor prognosis and metastasis. We tested whether ETS1 contributes to lung tumorigenesis by binding to Twist1, a gene involved in tumor cell motility and dissemination. We used a mouse lung cancer model with metastasis driven by conditionally activated Kras and concurrent tumor suppressor Lkb1 loss (Kras^G12D/ Lkb1^-/- model) and a similar model of lung cancer that does not metastasize, driven by conditionally activated Kras alone (Kras^G12D model). We show that Ets1 and Twist1 gene expression differs between Kras^G12D tumors (low Ets1 and Twist1 expression) and Kras^G12D/Lkb1^-/- tumors (high Ets1 and Twist1 expression). In human lung tumors, ETS1 and TWIST1 expression positively correlates and low combined ETS1 and TWIST1 levels are associated with improved survival compared to high levels. Using mouse cell lines derived from Kras^G12D and Kras^G12D/Lkb1^-/- mouse models and the human lung cancer (A549) cell line, we show that ETS1 regulates Twist1 expression. Chromatin immunoprecipitation assays confirm binding of ETS1 to the Twist1 promoter. Overexpression studies show that ETS1 transactivates Twist1 promoter activity in mouse and human cells. Silencing endogenous Ets1 by siRNA in mouse cell lines decreases Twist1 mRNA levels, decreases invasion, and increases cell growth. Ets1 and Twist1 are at the crossroad of several signaling pathways in cancer. Understanding their regulation may inform the development of therapies to impair lung tumor metastasis.

Mouse models in squamous cell lung cancer: impact for drug discovery

INTRODUCTION

Squamous cell lung cancer (SQCLC) is the second most common subtype of non-small cell lung cancer (NSCLC) and has limited therapeutic options. Its development is likely a result of a multistep process in response to chronic tobacco exposure, involving sequential metaplasia, dysplasia and invasive carcinoma. Its complex genomic landscape has recently been revealed but no driver mutations have been validated that could lead to molecularly targeted therapy as have emerged in lung adenocarcinoma. Few preclinical murine models exist for testing and developing novel therapeutics in SQCLC. Areas covered: This review discusses the pathophysiology and molecular underpinnings of SQCLC that have limited the development of animal models. It then explores the advantages and limitations of a variety of existing mouse models and illustrates their potential application in drug discovery and chemoprevention. Expert opinion: There are several challenges in the development of mouse models for SQCLC, such as lack of validated driver genetic alterations, unclear cell of origin, and difficulty in reproducing the sophisticated tumor microenvironment of human disease. Nevertheless, several successful SQCLC murine models have emerged, especially Patient Derived Xenografts (PDXs) and Genetically Engineered Mouse Models (GEMMs). Continued efforts are needed to generate more SQCLC animal models to better understand its carcinogenesis and metastasis and to further test novel therapeutic strategies.

Small cell lung cancer tumors and preclinical models display heterogeneity of neuroendocrine phenotypes

Background

Small cell lung cancer (SCLC) is a deadly, high grade neuroendocrine (NE) tumor without recognized morphologic heterogeneity. However, over 30 years ago we described a SCLC subtype with "variant" morphology which did not express some NE markers and exhibited more aggressive growth.

Methods

To quantitate NE properties of SCLCs, we developed a 50-gene expression-based NE score that could be applied to human SCLC tumors and cell lines, and genetically engineered mouse (GEM) models. We identified high and low NE subtypes of SCLC in all of our sample types, and characterized their properties.

Results

We found that 16% of human SCLC tumors and 10% of SCLC cell lines were of the low NE subtype, as well as cell lines from the GEM model. High NE SCLC lines grew as non-adherent floating aggregates or spheroids while Low NE lines had morphologic features of the variant subtype and grew as loosely attached cells. While the high NE subtype expressed one of the NE lineage master transcription factors ASCL1 or NEUROD1, together with NKX2-1, the entire range of NE markers, and lacked expression of the neuronal and NE repressor REST, the low NE subtype had lost expression of most NE markers, ASCL1, NEUROD1 and NKX2-1 and expressed REST. The low NE subtype had undergone epithelial mesenchymal transition (EMT) and had activated the Notch, Hippo and TGFβ pathways and MYC oncogene . Importantly, the high and low NE group of SCLC lines had similar gene expression profiles as their SCLC tumor counterparts.

Conclusions

SCLC tumors and cell lines can exhibit distinct inter-tumor heterogeneity with respect to expression of NE features. Loss of NE expression results in major alterations in morphology, growth characteristics, and molecular properties. These findings have major clinical implications as the two subtypes are predicted to have very different responses to targeted therapies.

Conditionally reprogrammed cells (CRC) methodology does not allow the in vitro expansion of patient-derived primary and metastatic lung cancer cells

Availability of tumor and non-tumor patient-derived models would promote the development of more effective therapeutics for non-small cell lung cancer (NSCLC). Recently, conditionally reprogrammed cells (CRC) methodology demonstrated exceptional potential for the expansion of epithelial cells from patient tissues. However, the possibility to expand patient-derived lung cancer cells using CRC protocols is controversial. Here, we used CRC approach to expand cells from non-tumoral and tumor biopsies of patients with primary or metastatic NSCLC as well as pulmonary metastases of colorectal or breast cancers. CRC cultures were obtained from both tumor and non-malignant tissues with extraordinary high efficiency. Tumor cells were tracked in vitro through tumorigenicity assay, monitoring of tumor-specific genetic alterations and marker expression. Cultures were composed of EpCAM+ lung epithelial cells lacking tumorigenic potential. NSCLC biopsies-derived cultures rapidly lost patient-specific genetic mutations or tumor antigens. Similarly, pulmonary metastases of colon or breast cancer generated CRC cultures of lung epithelial cells. All CRC cultures examined displayed epithelial lung stem cell phenotype and function. In contrast, brain metastatic lung cancer biopsies failed to generate CRC cultures. In conclusion, patient-derived primary and metastatic lung cancer cells were negatively selected under CRC conditions, limiting the expansion to non-malignant lung epithelial stem cells from either tumor or non-tumor tissue sources. Thus, CRC approach cannot be applied for direct therapeutic testing of patient lung tumor cells, as the tumor-derived CRC cultures are composed of (non-tumoral) airway basal cells.

Small-cell lung cancer: what we know, what we need to know and the path forward

Small-cell lung cancer (SCLC) is a deadly tumour accounting for approximately 15% of lung cancers and is pathologically, molecularly, biologically and clinically very different from other lung cancers. While the majority of tumours express a neuroendocrine programme (integrating neural and endocrine properties), an important subset of tumours have low or absent expression of this programme. The probable initiating molecular events are inactivation of TP53 and RB1, as well as frequent disruption of several signalling networks, including Notch signalling. SCLC, when diagnosed, is usually widely metastatic and initially responds to cytotoxic therapy but nearly always rapidly relapses with resistance to further therapies. There were no important therapeutic clinical advances for 30 years, leading SCLC to be designated a 'recalcitrant cancer'. Scientific studies are hampered by a lack of tissue availability. However, over the past 5 years, there has been a worldwide resurgence of studies on SCLC, including comprehensive molecular analyses, the development of relevant genetically engineered mouse models and the establishment of patient-derived xenografts. These studies have led to the discovery of new potential therapeutic vulnerabilities for SCLC and therefore to new clinical trials. Thus, while the past has been bleak, the future offers greater promise.

Immuno-Oncology: The Third Paradigm in Early Drug Development

Clinical researchers in oncology face the difficulty of developing new drugs for treating cancer patients. This challenge nowadays extends towards new horizons since a high number of drugs are developed in each of the three paradigms: classical cytotoxics, new targeted agents, and emergent immunotherapeutic approaches. Over the last decade, there has been an unstoppable progress in this third paradigm, to the extent that in 2013 immunotherapy was granted the scientific breakthrough of the year. However, the novel mechanisms of action of these immunotherapeutic agents entail a whole new series of concepts, resulting in a number of unresolved questions to which clarification is crucial for their success: establishment of accurate preclinical models able to predict human toxicities, better selection of candidate populations, finding and validation of predictive biomarkers, definition of suitable endpoints, improvements in first-in-human study designs, proposal of more accurate radiological response criteria, management of novel immune-related toxicities and development of combinations based on a biological rationale. In this article, we review the major challenges to overcome in forthcoming years. The final role of immunotherapy in cancer will be determined by our capacity to shed some light on some of these key points.

Molecular alterations in a new cell line (KU-Lu-MPPt3) established from a human lung adenocarcinoma with a micropapillary pattern

PURPOSE

Lung adenocarcinomas with a micropapillary pattern (MPP) are characterized by more frequent and pronounced vascular invasion, higher incidence and more advanced lymph node involvement and poorer prognosis than papillary adenocarcinomas without an MPP. Here we established a new lung cancer cell line featuring micropapillary structure.

METHODS

A 73-year-old never-smoker Japanese female, presenting with an abnormal chest shadow, was diagnosed with a clinical T2aN0M0 Stage IB lung adenocarcinoma and underwent left upper lobectomy with mediastinal lymph node dissection. Pathological study demonstrated a T2aN2M0 Stage IIIA micropapillary adenocarcinoma. Tumor cells were obtained from freshly resected lung material and used to establish the KU-Lu-MPPt3 cell line.

RESULTS

The KU-Lu-MPPt3 cells featured adherent monolayers, adherent tufts, and suspended tufts without adhesion under the same culture conditions. The cells were positive for cytokeratin, epithelial cell-adhesion molecules, E-cadherin, mucin-1, thyroid transcription factor-1, vimentin, and anti-programmed death ligand 1. Xenograft tumors clearly demonstrated micropapillary structures. Sequencing and fragment analysis of the epidermal growth factor receptor in the primary tumor tissue and KU-Lu-MPPt3 cells revealed an in-frame deletion E746-A750 in exon 19.

CONCLUSIONS

This cell line represents a new model system for molecular studies of lung adenocarcinoma which may be suitable for investigation of cancer spread and also for development of molecular-targeting and immunotherapies, both in vitro and in vivo.

TRP53 Mutants Drive Neuroendocrine Lung Cancer Through Loss-of-Function Mechanisms with Gain-of-Function Effects on Chemotherapy Response

Lung cancer is the leading cause of cancer-related deaths with small-cell lung cancer (SCLC) as the most aggressive subtype. Preferential occurrence of TP53 missense mutations rather than loss implicates a selective advantage for TP53-mutant expression in SCLC pathogenesis. We show that lung epithelial expression of R270H and R172H (R273H and R175H in humans), common TRP53 mutants in lung cancer, combined with RB1 loss selectively results in two subtypes of neuroendocrine carcinoma, SCLC and large cell neuroendocrine carcinoma (LCNEC). Tumor initiation and progression occur in a remarkably consistent time frame with short latency and uniform progression to lethal metastatic disease by 7 months. R270H or R172H expression and TRP53 loss result in similar phenotypes demonstrating that TRP53 mutants promote lung carcinogenesis through loss-of-function and not gain-of-function mechanisms. Tumor responses to targeted and cytotoxic therapeutics were discordant in mice and corresponding tumor cell cultures demonstrating need to assess therapeutic response at the organismal level. Rapamycin did not have therapeutic efficacy in the mouse model despite inhibiting mTOR signaling and markedly suppressing tumor cell growth in culture. In contrast, cisplatin/etoposide treatment using a patient regimen prolonged survival with development of chemoresistance recapitulating human responses. R270H, but not R172H, expression conferred gain-of-function activity in attenuating chemotherapeutic efficacy. These data demonstrate a causative role for TRP53 mutants in development of chemoresistant lung cancer, and provide tractable preclinical models to test novel therapeutics for refractory disease. Mol Cancer Ther; 16(12); 2913-26. ©2017 AACR.

Non-malignant respiratory epithelial cells preferentially proliferate from resected non-small cell lung cancer specimens cultured under conditionally reprogrammed conditions

The “conditionally reprogrammed cells” (CRC) method, using a Rho kinase inhibitor and irradiated mouse fibroblast cells has been described for the efficient growth of cells from malignant and non-malignant samples from primary tumor and non-malignant sites. Using the CRC method, four institutions independently cultured tumor tissues from 48 non-small cell lung cancers (NSCLC, mostly from primary resected tumors) and 22 non-malignant lungs. We found that epithelial cells could be cultured from tumor and non-malignant lung. However, epithelial cells cultured from tumors had features of non-malignant respiratory epithelial cells which include: 1) among 22 mutations found in the original tumors only two mutations were found in the CRC cultures with reduced frequency (31% to 13% and 92% to 15% from original tumor and CRC culture respectively); 2) copy number variation was analyzed in 9 tumor and their CRC cultures and only diploid patterns were found in CRC cultures; 3) mRNA expression profiles were similar to those of normal respiratory epithelial cells; and 4) co-culture of tumor and non-malignant lung epithelial cells resulted in mostly non-malignant cells. We conclude that CRC method is a highly selective and useful method for the growth of non-malignant respiratory epithelial cells from tumor specimens and only occasionally do such CRC cultures contain a small subpopulation of cancer cells marked by oncogenic mutations. While our findings are restricted to resected primary NSCLC, they indicated the necessity to fully characterize all CRC cultures and the need to develop culture technology that facilitates the growth of primary lung cancers.

A high-content image analysis approach for quantitative measurements of chemosensitivity in patient-derived tumor microtissues

Organotypic, three-dimensional (3D) cancer models have enabled investigations of complex microtissues in increasingly realistic conditions. However, a drawback of these advanced models remains the poor biological relevance of cancer cell lines, while higher clinical significance would be obtainable with patient-derived cell cultures. Here, we describe the generation and data analysis of 3D microtissue models from patient-derived xenografts (PDX) of non-small cell lung carcinoma (NSCLC). Standard of care anti-cancer drugs were applied and the altered multicellular morphologies were captured by confocal microscopy, followed by automated image analyses to quantitatively measure phenotypic features for high-content chemosensitivity tests. The obtained image data were thresholded using a local entropy filter after which the image foreground was split into local regions, for a supervised classification into tumor or fibroblast cell types. Robust statistical methods were applied to evaluate treatment effects on growth and morphology. Both novel and existing computational approaches were compared at each step, while prioritizing high experimental throughput. Docetaxel was found to be the most effective drug that blocked both tumor growth and invasion. These effects were also validated in PDX tumors in vivo. Our research opens new avenues for high-content drug screening based on patient-derived cell cultures, and for personalized chemosensitivity testing.

The instructive extracellular matrix of the lung: basic composition and alterations in chronic lung disease

The pulmonary extracellular matrix (ECM) determines the tissue architecture of the lung, and provides mechanical stability and elastic recoil, which are essential for physiological lung function. Biochemical and biomechanical signals initiated by the ECM direct cellular function and differentiation, and thus play a decisive role in lung development, tissue remodelling processes and maintenance of adult homeostasis. Recent proteomic studies have demonstrated that at least 150 different ECM proteins, glycosaminoglycans and modifying enzymes are expressed in the lung, and these assemble into intricate composite biomaterials. These highly insoluble assemblies of interacting ECM proteins and their glycan modifications can act as a solid phase-binding interface for hundreds of secreted proteins, which creates an information-rich signalling template for cell function and differentiation. Dynamic changes within the ECM that occur upon injury or with ageing are associated with several chronic lung diseases. In this review, we summarise the available data about the structure and function of the pulmonary ECM, and highlight changes that occur in idiopathic pulmonary fibrosis (IPF), pulmonary arterial hypertension (PAH), chronic obstructive pulmonary disease (COPD), asthma and lung cancer. We discuss potential mechanisms of ECM remodelling and modification, which we believe are relevant for future diagnosis and treatment of chronic lung disease.

The role of canonical and non-canonical Hedgehog signaling in tumor progression in a mouse model of small cell lung cancer

Hedgehog (Hh) signaling regulates cell fate and self-renewal in development and cancer. Canonical Hh signaling is mediated by Hh ligand binding to the receptor Patched (Ptch), which in turn activates Gli-mediated transcription through Smoothened (Smo), the molecular target of the Hh pathway inhibitors used as cancer therapeutics. Small cell lung cancer (SCLC) is a common, aggressive malignancy with universally poor prognosis. Although preclinical studies have shown that Hh inhibitors block the self-renewal capacity of SCLC cells, the lack of activating pathway mutations have cast doubt over the significance of these observations. In particular, the existence of autocrine, ligand-dependent Hh signaling in SCLC has been disputed. In a conditional Tp53;Rb1 mutant mouse model of SCLC, we now demonstrate a requirement for the Hh ligand Sonic Hedgehog (Shh) for the progression of SCLC. Conversely, we show that conditional Shh overexpression activates canonical Hh signaling in SCLC cells, and markedly accelerates tumor progression. When compared to mouse SCLC tumors expressing an activating, ligand-independent Smo mutant, tumors overexpressing Shh exhibited marked chromosomal instability and Smoothened-independent upregulation of Cyclin B1, a putative non-canonical arm of the Hh pathway. In turn, we show that overexpression of Cyclin B1 induces chromosomal instability in mouse embryonic fibroblasts lacking both Tp53 and Rb1. These results provide strong support for an autocrine, ligand-dependent model of Hh signaling in SCLC pathogenesis, and reveal a novel role for non-canonical Hh signaling through the induction of chromosomal instability.

Determining EGFR-TKI sensitivity of G719X and other uncommon EGFR mutations in non-small cell lung cancer: Perplexity and solution (Review)

Mutations in epidermal growth factor receptor (EGFR) play critical roles in the pathogenesis of non-small cell lung cancer (NSCLC), and they are highly associated with sensitivity to tyrosine kinase inhibitors (TKIs). While the pathogenic and pharmacological characteristics of common mutations in EGFR have been thoroughly investigated, those of uncommon mutations remain to be elucidated. Traditional approaches to study common mutations by randomized controlled trials are not feasible for uncommon mutations owing to their rarity. Therefore, by systematically reviewing laboratory and clinical studies of the G719X mutation, one of the uncommon mutations, we concluded that the G719X mutation was intermediately sensitive to TKIs, with an average response rate of 35.1% (47/134). Moreover, accordingly, we proposed a comprehensive model to investigate uncommon mutations in EGFR. The model involves both basic and clinical components, composed of structural analyses, functional alterations, cell viabilities and animal models with various types of clinical studies. In this review, we systematically reviewed studies of the G719X mutation and put forward a research model that could be generalized to explore uncommon mutations in diseases associated with gene mutations.

Tumour and normal tissue radiobiology in mouse models: how close are mice to mini-humans?

Animal modelling is essential to the study of radiobiology and the advancement of clinical radiation oncology by providing preclinical data. Mouse models in particular have been highly utilized in the study of both tumour and normal tissue radiobiology because of their cost effectiveness and versatility. Technology has significantly advanced in preclinical radiation techniques to allow highly conformal image-guided irradiation of small animals in an effort to mimic human treatment capabilities. However, the biological and physical limitations of animal modelling should be recognized and considered when interpreting preclinical radiotherapy (RT) studies. Murine tumour and normal tissue radioresponse has been shown to vary from human cellular and molecular pathways. Small animal irradiation techniques utilize different anatomical boundaries and may have different physical properties than human RT. This review addresses the difference between the human condition and mouse models and discusses possible strategies for future refinement of murine models of cancer and radiation for the benefit of both basic radiobiology and clinical translation.

The impact of immunohistochemistry on the classification of lung tumors

INTRODUCTION

To highlight the role of immunohistochemistry to lung cancer classification on the basis of existing guidelines and future perspectives.

AREAS COVERED

Four orienting key-issues were structured according to an extensive review on the English literature: a) cancer subtyping; b) best biomarkers and rules to follow; c) negative and positive profiling; d) suggestions towards an evidence-based proposal for lung cancer subtyping. A sparing material approach based on a limited number of specific markers is highly desirable. It includes p40 for squamous cell carcinoma ('no p40, no squamous'), TTF1 for adenocarcinoma, synaptophysin for neuroendocrine tumors and vimentin for sarcomatoid carcinoma. A close relationship between genotype and phenotype also supports a diagnostic role for negative profiles. Expert commentary: Highly specific and sensitive IHC markers according to positive and negative diagnostic algorithms seem appropriate for individual patients' lung cancer subtyping.

So you always wanted to write about that patient who

Small-cell lung cancer (SCLC) remains the deadliest of all the lung cancer types. Its high mortality is largely attributed to the invariable development of resistance to standard chemo/radiotherapies, which have remained unchanged for the past 30 years, underscoring the need for new therapeutic approaches. The discovery of molecular targets for chemoprevention and treatment has been hampered by the poor understanding of SCLC progression. In recent years, comprehensive omics-based analyses have led to the discovery of recurrent alterations in patient tumors, and functional studies using genetically engineered mouse models and patient-derived tumor models have provided information about the alterations critical for SCLC pathogenesis. Defining the somatic alterations scattered throughout the SCLC genome will help to understand the underlying mechanism of this devastating disease and pave the way for the discovery of therapeutic vulnerabilities associated with the genomic alterations.

Alterations in the small cell lung cancer (SCLC) genome are critical for disease progression and relapse. A complete map of the genome in cancerous cells would greatly improve the chances of successfully treating this deadly disease. SCLC is often detected too late, and only five per cent of patients survive beyond five years after diagnosis. While the disease initially responds to standard chemotherapy, the cancer cells quickly build resistance and relapse follows. Kwon-Sik Park at the University of Virginia, Charlottesville, US, and co-workers reviewed current understanding of SCLC genome alterations. The latest research highlights substantial variations in the SCLC genome between patients, with implications for existing treatment regimens. Researchers have made considerable progress in profiling the genome, with significant alterations, mutations and potential therapeutic targets now being explored in genetically engineered mouse models and patient-derived tumor models.