Mouse models of lung cancer

miR-92a-3p regulates cisplatin-induced cancer cell death

Non-small cell lung cancer is characterized by a dismal prognosis largely owing to inefficient diagnosis and tenacious drug resistance. Therefore, the identification of new molecular determinants underlying sensitivity of cancer cells to existing therapy is of particular importance to develop new effective combinatorial treatment strategy. MicroRNAs (miRNAs), a class of small non-coding RNAs, have been established as master regulators of a variety of cellular processes that play a key role in tumor initiation, progression and metastasis. This, along with their widespread deregulation in many distinct cancers, has triggered enthusiasm for miRNAs as novel therapeutic targets for cancer management, in particular in patients with refractory cancers such as those harboring KRAS mutations. In this study, we performed a loss-of-function screening approach to identify miRNAs whose silencing promotes sensitivity of lung adenocarcinoma (LUAD) cells to cisplatin. Our results showed in particular that antisense oligonucleotides directed against miR-92a-3p, a member of the oncogenic miR-17 ~ 92 cluster, caused the greatest increase in the sensitivity of KRAS-mutated LUAD cells to cisplatin. In addition, we demonstrated that this miRNA finely regulates the apoptotic threshold and the proliferative capacity of various tumor cell lines with distinct genetic alterations. Collectively, these data suggest that targeting miR-92a-3p may serve as an effective strategy to overcome treatment resistance of solid tumors.

Relationship between Lung Carcinogenesis and Chronic Inflammation in Rodents

Simple Summary

Lung cancer is the most common cause of cancer-related deaths worldwide. There are various risk factors for lung cancer, including tobacco smoking, inhalation of dust particles, chronic inflammation, and genetic factors. Chronic inflammation has been considered a key factor that promotes tumor progression via production of cytokines, chemokines, cytotoxic mediators, and reactive oxygen species by inflammatory cells. Here, we review rodent models of lung tumor induced by tobacco, tobacco-related products, and pro-inflammatory materials as well as genetic modifications, and discuss the relationship between chronic inflammation and lung tumor. Through this review, we hope to clarify the effects of chronic inflammation on lung carcinogenesis and help develop new treatments for lung cancer.

Abstract

Lung cancer remains the leading cause of cancer-related deaths, with an estimated 1.76 million deaths reported in 2018. Numerous studies have focused on the prevention and treatment of lung cancer using rodent models. Various chemicals, including tobacco-derived agents induce lung cancer and pre-cancerous lesions in rodents. In recent years, transgenic engineered rodents, in particular, those generated with a focus on the well-known gene mutations in human lung cancer (KRAS, EGFR, and p53 mutations) have been widely studied. Animal studies have revealed that chronic inflammation significantly enhances lung carcinogenesis, and inhibition of inflammation suppresses cancer progression. Moreover, the reduction in tumor size by suppression of inflammation in animal experiments suggests that chronic inflammation influences the promotion of tumorigenesis. Here, we review rodent lung tumor models induced by various chemical carcinogens, including tobacco-related carcinogens, and transgenics, and discuss the roles of chronic inflammation in lung carcinogenesis.

The oncogenic potential of a mutant TP53 gene explored in two spontaneous lung cancer mice models

Background

Lung cancer is the number one cancer killer worldwide. A major drawback in the lung cancer treatment field is the lack of realistic mouse models that replicate the complexity of human malignancy and immune contexture within the tumor microenvironment. Such models are urgently needed. Mutations of the tumor protein p53 are among the most common alterations in human lung cancers.

Methods

Previously, we developed a line of lung cancer mouse model where mutant human TP53-273H is expressed in a lung specific manner in FVB/N background. To investigate whether the human TP53 mutant has a similar oncogenic potential when it is expressed in another strain of mouse, we crossed the FVB/N-SPC-TP53-273H mice to A/J strain and created A/J-SPC-TP53-273H transgenic mice. We then compared lung tumor formation between A/J-SPC-TP53-273H and FVB/N-SPC-TP53-273H.

Results

We found the TP53-273H mutant gene has a similar oncogenic potential in lung tumor formation in both mice strains, although A/J strain mice have been found to be a highly susceptible strain in terms of carcinogen-induced lung cancer. Both transgenic lines survived more than 18 months and developed age related lung adenocarcinomas. With micro CT imaging, we found the FVB-SPC-TP53-273H mice survived more than 8 weeks after initial detection of lung cancer, providing a sufficient window for evaluating new anti-cancer agents.

Conclusions

Oncogenic potential of the most common genetic mutation, TP53-273H, in human lung cancer is unique when it is expressed in different strains of mice. Our mouse models are useful tools for testing novel immune checkpoint inhibitors or other therapeutic strategies in the treatment of lung cancer.

Patients Lung Derived Tumoroids (PLDTs) to model therapeutic response

Preclinical lung cancer models are essential for a basic understanding of lung cancer biology and its translation into efficient treatment options for affected patients. Lung cancer cell lines and xenografts derived directly from human lung tumors have proven highly valuable in fundamental oncology research and anticancer drug discovery. Both models inherently comprise advantages and caveats that have to be accounted for. Recently, we have enabled reliable in vitro culture techniques from lung cancer biopsies as Patients Lung Derived Tumoroids (PLDTs). This breakthrough provides the possibility of high-throughput drug screening covering the spectrum of lung cancer phenotypes seen clinically. We have adapted and optimized our in vitro three-dimensional model as a preclinical lung cancer model to recapitulate the tumor microenvironment (TME) using matrix reconstitution. Hence, we developed directly PLDTs to screen for chemotherapeutics and radiation treatment. This original model will enable precision medicine to become a reality, allowing a given patient sample to be screened for effective ex vivo therapeutics, aiming at tailoring of treatments specific to that individual. Hence, this tool can enhance clinical outcomes and avoid morbidity due to ineffective therapies.

In vivo Tumor Growth and Spontaneous Metastasis Assays Using A549 Lung Cancer Cells

Metastasis accounts for the majority of cancer related deaths. The genetically engineered mouse (GEM) models and cell line-based subcutaneous and orthotopic mouse xenografts have been developed to study the metastatic process. By using lung cancer cell line A549 as an example, we present a modified protocol to establish the cell line-based xenograft. Our protocol ensures sufficient establishment of the mouse xenografts and allows us to monitor tumor growth and spontaneous metastasis. This protocol could be adapted to other types of established cancer cell lines or primary cancer cells to study the mechanism of metastatic process as well as to test the effect of the potential anti-cancer agents on tumor growth and metastatic capacity.

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.

Patterns of Vasculature in Mouse Models of Lung Cancer Are Dependent on Location

PURPOSE

Preclinical studies of hypoxia are generally done using ectopic xenograft tumors, which behave differently from human tumors. Our previous findings have shown that subcutaneously implanted lung tumors exhibit more hypoxia than their orthotopic implanted or spontaneous K-ras-induced counterparts. We hypothesize that differences in hypoxia are due to site-specific differences in vascularity and perfusion.

PROCEDURES

To compare the presence and functionality of vessels in these tumor models, we studied vascular perfusion in vivo in real time.

RESULTS

Orthotopically implanted and spontaneous K-ras-induced lung tumors showed elevated perfusion, demonstrating vasculature functionality. Little contrast agent uptake was observed within the subcutaneously implanted tumors, indicating vascular dysfunction. These findings were corroborated at the microscopic level with Hoechst 33342 and Meca-32 staining.

CONCLUSIONS

From these observations, we concluded that differences in hypoxia in experimental models is related to vessel perfusion. Thus, appropriate selection of preclinical lung tumor models is essential for the study of hypoxia, angiogenesis and therapies targeting these phenomena.

Marine Mollusk-Derived Agents with Antiproliferative Activity as Promising Anticancer Agents to Overcome Chemotherapy Resistance

The chemical investigation of marine mollusks has led to the isolation of a wide variety of bioactive metabolites, which evolved in marine organisms as favorable adaptations to survive in different environments. Most of them are derived from food sources, but they can be also biosynthesized de novo by the mollusks themselves, or produced by symbionts. Consequently, the isolated compounds cannot be strictly considered as "chemotaxonomic markers" for the different molluscan species. However, the chemical investigation of this phylum has provided many compounds of interest as potential anticancer drugs that assume particular importance in the light of the growing literature on cancer biology and chemotherapy. The current review highlights the diversity of chemical structures, mechanisms of action, and, most importantly, the potential of mollusk-derived metabolites as anticancer agents, including those biosynthesized by mollusks and those of dietary origin. After the discussion of dolastatins and kahalalides, compounds previously studied in clinical trials, the review covers potentially promising anticancer agents, which are grouped based on their structural type and include terpenes, steroids, peptides, polyketides and nitrogen-containing compounds. The "promise" of a mollusk-derived natural product as an anticancer agent is evaluated on the basis of its ability to target biological characteristics of cancer cells responsible for poor treatment outcomes. These characteristics include high antiproliferative potency against cancer cells in vitro, preferential inhibition of the proliferation of cancer cells over normal ones, mechanism of action via nonapoptotic signaling pathways, circumvention of multidrug resistance phenotype, and high activity in vivo, among others. The review also includes sections on the targeted delivery of mollusk-derived anticancer agents and solutions to their procurement in quantity.

Temporal dynamics of the developing lung transcriptome in three common inbred strains of laboratory mice reveals multiple stages of postnatal alveolar development

To characterize temporal patterns of transcriptional activity during normal lung development, we generated genome wide gene expression data for 26 pre- and post-natal time points in three common inbred strains of laboratory mice (C57BL/6J, A/J, and C3H/HeJ). Using Principal Component Analysis and least squares regression modeling, we identified both strain-independent and strain-dependent patterns of gene expression. The 4,683 genes contributing to the strain-independent expression patterns were used to define a murine Developing Lung Characteristic Subtranscriptome (mDLCS). Regression modeling of the Principal Components supported the four canonical stages of mammalian embryonic lung development (embryonic, pseudoglandular, canalicular, saccular) defined previously by morphology and histology. For postnatal alveolar development, the regression model was consistent with four stages of alveolarization characterized by episodic transcriptional activity of genes related to pulmonary vascularization. Genes expressed in a strain-dependent manner were enriched for annotations related to neurogenesis, extracellular matrix organization, and Wnt signaling. Finally, a comparison of mouse and human transcriptomics from pre-natal stages of lung development revealed conservation of pathways associated with cell cycle, axon guidance, immune function, and metabolism as well as organism-specific expression of genes associated with extracellular matrix organization and protein modification. The mouse lung development transcriptome data generated for this study serves as a unique reference set to identify genes and pathways essential for normal mammalian lung development and for investigations into the developmental origins of respiratory disease and cancer. The gene expression data are available from the Gene Expression Omnibus (GEO) archive (GSE74243). Temporal expression patterns of mouse genes can be investigated using a study specific web resource (http://lungdevelopment.jax.org).

An orthotopic mouse model of small cell lung cancer reflects the clinical course in patients

Small cell lung cancer (SCLC) is a highly aggressive subtype of lung cancer with very poor prognosis due to early metastatic spread and development of chemoresistance. In the last 30 years the study of SCLC has been constrained by a lack of primary human tumor specimen thus highlighting the need of a suitable mouse model. In this article we present the establishment of an orthotopic xenograft mouse model which accurately reproduced the clinical course of SCLC. Orthotopic implantation enabled engraftment of primary lung tumors in all injected mice. Furthermore, immunodeficiency of mice allowed formation of spontaneous metastases in characteristic organs. Bioluminescence Imaging, Magnetic Resonance Imaging and Positron emission tomography were applied to monitor engraftment, metabolism and the exact growth of tumors over time. In order to mimic the extensive disease stage, mice were injected with aggressive human chemoresistant cells leading to development of chemoresistant tumors and early metastatic spread. As a proof of concept treatment of tumor-bearing mice with conventional chemotherapeutics reduced tumor volumes, but a complete regression of tumors was not achieved. By mimicking the extensive disease stage our mouse model can facilitate the study of mechanisms contributing to chemoresistance and metastasis formation, as well as drug screening and evaluation of new treatment strategies for SCLC patients.

Ovine pulmonary adenocarcinoma: a large animal model for human lung cancer

Lung cancer is the leading cause of cancer deaths worldwide. Recent progress in understanding the molecular pathogenesis of this disease has resulted in novel therapeutic strategies targeting specific groups of patients. Further studies are required to provide additional advances in diagnosis and treatment. Animal models are valuable tools for studying oncogenesis in lung cancer, particularly during the early stages of disease where tissues are rarely available from human cases. Mice have traditionally been used for studying lung cancer in vivo, and a variety of spontaneous and transgenic models are available. However, it is recognized that other species may also be informative for studies of cancer. Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring lung cancer of sheep caused by retrovirus infection and has several features in common with adenocarcinoma of humans, including a similar histological appearance and activation of common cell signaling pathways. Additionally, the size and organization of human lungs are much closer to those of sheep lungs than to those of mice, which facilitates experimental approaches in sheep that are not available in mice. Thus OPA presents opportunities for studying lung tumor development that can complement conventional murine models. Here we describe the potential applications of OPA as a model for human lung adenocarcinoma with an emphasis on the various in vivo and in vitro experimental systems available.

Systems toxicology approaches enable mechanistic comparison of spontaneous and cigarette smoke-related lung tumor development in the A/J mouse model

The A/J mouse is highly susceptible to lung tumor induction and has been widely used as a screening model in carcinogenicity testing and chemoprevention studies. However, the A/J mouse model has several disadvantages. Most notably, it develops lung tumors spontaneously. Moreover, there is a considerable gap in our understanding of the underlying mechanisms of pulmonary chemical carcinogenesis in the A/J mouse. Therefore, we examined the differences between spontaneous and cigarette smoke-related lung tumors in the A/J mouse model using mRNA and microRNA (miRNA) profiling. Male A/J mice were exposed whole-body to mainstream cigarette smoke (MS) for 18 months. Gene expression interaction term analysis of lung tumors and surrounding non-tumorous parenchyma samples from animals that were exposed to either 300 mg/m³ MS or sham-exposed to fresh air indicated significant differential expression of 296 genes. Ingenuity Pathway Analysis^® (IPA^®) indicated an overall suppression of the humoral immune response, which was accompanied by a disruption of sphingolipid and glycosaminoglycan metabolism and a deregulation of potentially oncogenic miRNA in tumors of MS-exposed A/J mice. Thus, we propose that MS exposure leads to severe perturbations in pathways essential for tumor recognition by the immune system, thereby potentiating the ability of tumor cells to escape from immune surveillance. Further, exposure to MS appeared to affect expression of miRNA, which have previously been implicated in carcinogenesis and are thought to contribute to tumor progression. Finally, we identified a 50-gene expression signature and show its utility in distinguishing between cigarette smoke-related and spontaneous lung tumors.

Lung cancer stem cells: Molecular features and therapeutic targets

Lung cancers are highly heterogeneous and resistant to available therapeutic agents, with a five year survival rate of less than 15%. Despite significant advances in our knowledge of the genetic alterations and aberrations in signaling pathways, it has been difficult to determine the basis of lung cancer heterogeneity and drug resistance. Cancer stem cell model has attracted a significant amount of attention in recent years as a viable explanation for the heterogeneity, drug resistance, dormancy and recurrence and metastasis of various tumors. At the same time, cancer stem cells have been relatively less characterized in lung cancers. This review summarizes the current understanding of lung cancer stem cells, including their molecular features and signaling pathways that drive their stemness. This review also discusses the potential startegies to inhibit the signaling pathways driving stemness, in an effort to eradicate these cells to combat lung cancer.

The diverse roles of nonsteroidal anti-inflammatory drug activated gene (NAG-1/GDF15) in cancer

Nonsteroidal anti-inflammatory drug (NSAID) activated gene-1, NAG-1, is a divergent member of the transforming growth factor-beta (TGF-β) superfamily that plays a complex but poorly understood role in several human diseases including cancer. NAG-1 expression is substantially increased during cancer development and progression especially in gastrointestinal, prostate, pancreatic, colorectal, breast, melanoma, and glioblastoma brain tumors. Aberrant increases in the serum levels of secreted NAG-1 correlate with poor prognosis and patient survival rates in some cancers. In contrast, the expression of NAG-1 is up-regulated by several tumor suppressor pathways including p53, GSK-3β, and EGR-1. NAG-1 expression is also induced by many drugs and dietary compounds which are documented to prevent the development and progression of cancer in mouse models. Studies with transgenic mice expressing human NAG-1 demonstrated that the expression of NAG-1 inhibits the development of intestinal tumors and prostate tumors in animal models. Laboratory and clinical evidence suggest that NAG-1, like other TGF-β family members, may have different or pleiotropic functions in the early and late stages of carcinogenesis. Upon understanding the molecular mechanism and function of NAG-1 during carcinogenesis, NAG-1 may serve as a potential biomarker for the diagnosis and prognosis of cancer and a therapeutic target for the inhibition and treatment of cancer development and progression.

A gated-7T MRI technique for tracking lung tumor development and progression in mice after exposure to low doses of ionizing radiation

A gated-7T magnetic resonance imaging (MRI) application is described that can accurately and efficiently measure the size of in vivo mouse lung tumors from ∼0.1 mm(3) to >4 mm(3). This MRI approach fills a void in radiation research because the technique can be used to noninvasively measure the growth rate of lung tumors in large numbers of mice that have been irradiated with low doses (<50 mGy) without the additional radiation exposure associated with planar X ray, CT or PET imaging. High quality, high resolution, reproducible images of the mouse thorax were obtained in ∼20 min using: (1) a Bruker 7T micro-MRI scanner equipped with a 60 mm inner diameter gradient insert capable of generating a maximum gradient of 1000 mT/m; (2) a 35 mm inner diameter quadrature radiofrequency volume coil; and (3) an electrocardiogram and respiratory gated Fast Low Angle Shot (FLASH) pulse sequence. The images had an in-plane image resolution of 98 μm and a 0.5 mm slice thickness. Tumor diameter measured by MRI was highly correlated (R(2) = 0.97) with the tumor diameter measured by electronic calipers. Data generated with an initiation/promotion mouse model of lung carcinogenesis and this MRI technique demonstrated that mice exposed to 4 weekly fractions of 10, 30 or 50 mGy of CT radiation had the same lung tumor growth rate as that measured in sham-irradiated mice. In summary, this high-field, double-gated MRI approach is an efficient way of quantitatively tracking lung tumor development and progression after exposure to low doses of ionizing radiation.

Optimized murine lung preparation for detailed structural evaluation via micro-computed tomography

Utilizing micro-X-ray CT (μCT) imaging, we sought to generate an atlas of in vivo and intact/ex vivo lungs from normal murine strains. In vivo imaging allows visualization of parenchymal density and small airways (15-28 μm/voxel). Ex vivo imaging of the intact lung via μCT allows for improved understanding of the three-dimensional lung architecture at the alveolar level with voxel dimensions of 1-2 μm. μCT requires that air spaces remain air-filled to detect alveolar architecture while in vivo structural geometry of the lungs is maintained. To achieve these requirements, a fixation and imaging methodology that permits nondestructive whole lung ex vivo μCT imaging has been implemented and tested. After in vivo imaging, lungs from supine anesthetized C57Bl/6 mice, at 15, 20, and 25 cmH(2)O airway pressure, were fixed in situ via vascular perfusion using a two-stage flushing system while held at 20 cmH(2)O airway pressure. Extracted fixed lungs were air-dried. Whole lung volume was acquired at 1, 7, 21, and >70 days after the lungs were dried and served as validation for fixation stability. No significant shrinkage was observed: +8.95% change from in vivo to fixed lung (P = 0.12), -1.47% change from day 1 to day 7 (P = 0.07), -2.51% change from day 1 to day 21 (P = 0.05), and -4.90% change from day 1 to day 70 and thereafter (P = 0.04). μCT evaluation showed well-fixed alveoli and capillary beds correlating with histological analysis. A fixation and imaging method has been established for μCT imaging of the murine lung that allows for ex vivo morphometric analysis, representative of the in vivo lung.

TAZ is a novel oncogene in non-small cell lung cancer

Transcriptional coactivator with PDZ-binding motif (TAZ) is a transcriptional coactivator involved in the differentiation of stem cell as well as the development of multiple organs. Recently, TAZ has also been identified as a major component of the novel Hippo-LATS tumor suppressor pathway and to function as an oncogene in breast cancer. We show for the first time that TAZ is an oncogene in non-small cell lung cancer (NSCLC). Our results show that TAZ is overexpressed in NSCLC cells and that lentivirus-mediated overexpression of TAZ in HBE135 immortalized human bronchial epithelial cells causes increased cell proliferation and transformation, which can be restored back to its original levels by knockdown of TAZ. In addition, short-hairpin RNA (shRNA)-mediated knockdown of TAZ expression in NSCLC cells suppresses their proliferation and anchorage-independent growth in vitro, and tumor growth in mice in vivo, which can be reversed by re-introduction of shRNA-resistant TAZ into TAZ-knockdown NSCLC cells. These results indicate that TAZ is an oncogene and has an important role in tumorigenicity of NSCLC cells. Therefore, TAZ may present a novel target for the future diagnosis, prognosis and therapy of lung cancer.

Assessment of acridine orange and SYTO 16 for in vivo imaging of the peritoneal tissues in mice

The effect of peritoneal injection of acridine orange and SYTO 16 in mice was investigated. Images of peritoneal tissues stained with these dyes and obtained through a confocal micro-endoscope are presented. Seventy-five Balb/c mice were split into five groups and given peritoneal injections of dye or saline. The proportions of negative outcomes in each group were compared using confidence intervals and the Fisher's exact statistical test. A statistically significant increase in adverse events due to dye injection was not observed. These data provide an initial investigation into the safety of acridine orange and SYTO 16 for in vivo imaging.

Regression of drug-resistant lung cancer by the combination of rosiglitazone and carboplatin

PURPOSE

Current therapy for lung cancer involves multimodality therapies. However, many patients are either refractory to therapy or develop drug resistance. KRAS and epidermal growth factor receptor (EGFR) mutations represent some of the most common mutations in lung cancer, and many studies have shown the importance of these mutations in both carcinogenesis and chemoresistance. Genetically engineered murine models of mutant EGFR and KRAS have been developed that more accurately recapitulate human lung cancer. Recently, using cell-based experiments, we showed that platinum-based drugs and the antidiabetic drug rosiglitazone (PPARgamma ligand) interact synergistically to reduce cancer cell and tumor growth. Here, we directly determined the efficacy of the PPARgamma/carboplatin combination in these more relevant models of drug resistant non-small cell lung cancer.

EXPERIMENTAL DESIGN

Tumorigenesis was induced by activation of either mutant KRAS or EGFR. Mice then received either rosiglitazone or carboplatin monotherapy, or a combination of both drugs. Change in tumor burden, pathology, and evidence of apoptosis and cell growth were assessed.

RESULTS

Tumor burden remained unchanged or increased in the mice after monotherapy with either rosiglitazone or carboplatin. In striking contrast, we observed significant tumor shrinkage in mice treated with these drugs in combination. Immunohistochemical analyses showed that this synergy was mediated via both increased apoptosis and decreased proliferation. Importantly, this synergy between carboplatin and rosiglitazone did not increase systemic toxicity.

CONCLUSIONS

These data show that the PPARgamma ligand/carboplatin combination is a new therapy worthy of clinical investigation in lung cancers, including those cancers that show primary resistance to platinum therapy or acquired resistance to targeted therapy.

Rapid repair of UVA-induced oxidized purines and persistence of UVB-induced dipyrimidine lesions determine the mutagenicity of sunlight in mouse cells

Despite the predominance of ultraviolet A (UVA) relative to UVB in terrestrial sunlight, solar mutagenesis in humans and rodents is characterized by mutations specific for UVB. We have investigated the kinetics of repair of UVA- and UVB-induced DNA lesions in relation to mutagenicity in transgenic mouse fibroblasts irradiated with equilethal doses of UVA and UVB in comparison to simulated-sunlight UV (SSL). We have also analyzed mutagenesis-derived carcinogenesis in sunlight-associated human skin cancers by compiling the published data on mutation types found in crucial genes in nonmelanoma and melanoma skin cancers. Here, we demonstrate a resistance to repair of UVB-induced cis-syn cyclobutane pyrimidine-dimers (CPDs) together with rapid removal of UVA-induced oxidized purines in the genome overall and in the cII transgene of SSL-irradiated cells. The spectra of mutation induced by both UVB and SSL irradiation in this experimental system are characterized by significant increases in relative frequency of C-->T transitions at dipyrimidines, which are the established signature mutation of CPDs. This type of mutation is also the predominant mutation found in human nonmelanoma and melanoma tumor samples in the TP53, CDKN2, PTCH, and protein kinase genes. The prevailing role of UVB over UVA in solar mutagenesis in our test system can be ascribed to different kinetics of repair for lesions induced by the respective UV irradiation.

A large animal model to evaluate the effects of Hsp90 inhibitors for the treatment of lung adenocarcinoma

Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring lung cancer of sheep caused by Jaagsiekte sheep retrovirus (JSRV). The JSRV envelope glycoprotein (Env) functions as a dominant oncoprotein in vitro and in vivo. In order to develop the basis for the use of OPA as a lung cancer model, we screened a variety of signal transduction inhibitors for their ability to block transformation by the JSRV Env. Most inhibitors were not effective in blocking JSRV Env-induced transformation. On the contrary, various Hsp90 inhibitors efficiently blocked JSRV transformation. This phenomenon was at least partly due to Akt degradation, which is activated in JSRV-transformed cells. Hsp90 was found expressed in tumor cells of sheep with naturally occurring OPA. In addition, Hsp90 inhibitors specifically inhibited proliferation of immortalized and moreover primary cells derived from OPA tumors. Thus, OPA could be used as a large animal model for comprehensive studies investigating the effects of Hsp90 inhibitors in lung adenocarcinoma.

Transgenic cyclin E triggers dysplasia and multiple pulmonary adenocarcinomas

Cyclin E is a critical G(1)-S cell cycle regulator aberrantly expressed in bronchial premalignancy and lung cancer. Cyclin E expression negatively affects lung cancer prognosis. Its role in lung carcinogenesis was explored. Retroviral cyclin E transduction promoted pulmonary epithelial cell growth, and small interfering RNA targeting of cyclin E repressed this growth. Murine transgenic lines were engineered to mimic aberrant cyclin E expression in the lung. Wild-type and proteasome degradation-resistant human cyclin E transgenic lines were independently driven by the human surfactant C (SP-C) promoter. Chromosome instability (CIN), pulmonary dysplasia, sonic hedgehog (Shh) pathway activation, adenocarcinomas, and metastases occurred. Notably, high expression of degradation-resistant cyclin E frequently caused dysplasia and multiple lung adenocarcinomas. Thus, recapitulation of aberrant cyclin E expression as seen in human premalignant and malignant lung lesions reproduces in the mouse frequent features of lung carcinogenesis, including CIN, Shh pathway activation, dysplasia, single or multiple lung cancers, or presence of metastases. This article reports unique mouse lung cancer models that replicate many carcinogenic changes found in patients. These models provide insights into the carcinogenesis process and implicate cyclin E as a therapeutic target in the lung.