Animal models for studying lung cancer and evaluating novel intervention strategies

The Novel Fusion Protein Melittin-MIL-2 Exhibits Strong Antitumor Immune Effect in Lung Adenocarcinoma Cell A549

In previous studies, we developed a novel fusion protein named "melittin-MIL-2" which exhibited more anti-tumor activity. However, it remains unclear whether melittin-MIL-2 possesses antitumor immune effect on lung adenocarcinoma. In this study, the immune effect and mechanism of melittin-MIL-2 inhibiting the growth and invasion of lung adenocarcinoma will be investigated, in order to provide novel perspectives for the immunotherapy of lung cancer. The results indicated that melittin-MIL-2 promoted T cell proliferation, enhanced NK cell cytotoxicity, and boosted IFN-γ secretion in PBMCs. After melittin-MIL-2 stimulation, perforin expression and LAK/NK-like killing activities of human PBMCs and NK cells were significantly enhanced. Melittin-MIL-2 is capable of hampering the development and proliferation of lung adenocarcinoma cell A549. ICAM-1 and Fas expression in A549 cells exposed to melittin-MIL-2 rose significantly. The expression levels of TLR8 and VEGF in A549 cells decreased significantly after melittin-MIL-2 stimulation. In vivo, melittin-MIL-2 substantially impeded the growth of lung adenocarcinoma and formed an immune-stimulating microenvironment locally in tumor tissues. In conclusion, the novel fusion protein melittin-MIL-2 exhibits strong anti-tumor immune effect in lung adenocarcinoma cell A549 via activating the LFA-1/ICAM-1 and Fas/FasL pathways to enhance cytolytic activity, upregulating the secretion of IFN-γ and perforin, and boosting LAK/NK-like killing activities. Immuno-effector cells and their secreted cytokines can form immune stimulation microenvironment locally in lung adenocarcinoma Lewis mice tissue.

Ovine Pulmonary Adenocarcinoma: A Unique Model to Improve Lung Cancer Research

Lung cancer represents a major worldwide health concern; although advances in patient management have improved outcomes for some patients, overall 5-year survival rates are only around 15%. In vitro studies and mouse models are commonly used to study lung cancer and their use has increased the molecular understanding of the disease. Unfortunately, mouse models are poor predictors of clinical outcome and seldom mimic advanced stages of the human disease. Animal models that more accurately reflect human disease are required for progress to be made in improving treatment outcomes and prognosis. Similarities in pulmonary anatomy and physiology potentially make sheep better models for studying human lung function and disease. Ovine pulmonary adenocarcinoma (OPA) is a naturally occurring lung cancer that is caused by the jaagsiekte sheep retrovirus. The disease is endemic in many countries throughout the world and has several features in common with human lung adenocarcinomas, including histological classification and activation of common cellular signaling pathways. Here we discuss the in vivo and in vitro OPA models that are currently available and describe the advantages of using pre-clinical naturally occurring OPA cases as a translational animal model for human lung adenocarcinoma. The challenges and options for obtaining these OPA cases for research purposes, along with their use in developing novel techniques for the evaluation of chemotherapeutic agents or for monitoring the tumor microenvironment in response to treatment, are also discussed.

Yangfei Kongliu Formula, a compound Chinese herbal medicine, combined with cisplatin, inhibits growth of lung cancer cells through transforming growth factor-β1 signaling pathway

OBJECTIVE

To investigate the tumor inhibition effect of Yangfei Kongliu Formula (YKF), a compound Chinese herbal medicine, combined with cisplatin (DDP) and its action mechanisms.

METHODS

C57BL/6 mice with Lewis lung carcinoma were divided into six groups: control group (C), DDP group (2 mg/kg, DDP), low-dose YKF group (2.43 g/kg, L), high-dose YKF group (24.3 g/kg, H), low-dose YKF combined with DDP group (L + DDP) and high-dose YKF combined with DDP group (H + DDP). Transforming growth factor-β1 (TGF-β1), mothers against decapentaplegic homolog 3 (Smad3) and Smad7 levels were measured with quantitative real-time polymerase chain reaction (qPCR), Western blotting and immunohistochemistry. An enzyme-linked immunosorbent assay was used to analyze the expressions of interleukin-2 (IL-2) and tumor necrosis factor-α (TNF-α).

RESULTS

YKF combined with DDP significantly inhibited the growth and metastasis of tumors relative to the control group, and YKF groups (P < 0.05). There was no significant difference between high-dose YKF group and low-dose YKF group (P > 0.05). We also found that the expression levels of TGF-β1 and Smad3 were both significantly decreased by YKF relative to the control group (P < 0.05). Furthermore, after treatment with YKF combined with DDP, the expression levels of TGF-β1 and Smad3 were decreased but the expression level of Smad7 was increased relative to the DDP group (P < 0.05). Compared to the DDP group, the combination of YKF and DDP enhanced the effect of tumor inhibition (P < 0.05), showing obvious synergy between YKF and DDP. Treatment with DDP or YKF decreased serum levels of IL-2 and TNF-α relative to the control group (P < 0.05). Furthermore, the expression levels of IL-2 and TNF-α were significantly decreased when treated with YKF in combination with DDP. Co-treatment with YKF and DDP significantly inhibited tumor growth, decreased the expressions of TGF-β1, Smad3, IL-2 and TNF-α and increased the expression of Smad7; these differences were significant relative to both YKF groups and the control group (P < 0.05).

CONCLUSION

YKF can inhibit tumor growth synergistically with DDP, mainly through the TGF-β1 signaling pathway.

Detection of lung tumors in mice using a 1-tesla compact magnetic resonance imaging system

Due to their small size, lung tumors in rodents are typically investigated using high-field magnetic resonance (MR) systems (4.7 T or higher) to achieve higher signal-to-noise ratios, although low-field MR systems are less sensitive to susceptibility artifacts caused by air in the lung. We investigated the feasibility of detecting lung tumors in living, freely breathing mice with a 1-T compact permanent magnet MR system. In total, 4 mice were used, and MR images of mouse lungs were acquired using a T1-weighted three-dimensional fast low-angle shot sequence without cardiac or respiratory gating. The delineation and size of lung tumors were assessed and compared with histopathological findings. Submillimeter lesions were demonstrated as hyperintense, relative to the surrounding lung parenchyma, and were delineated clearly. Among the 13 lesions validated in histopathological sections, 11 were detected in MR images; the MR detection rate was thus 84.6%. A strong correlation was obtained in size measurements between MR images and histological sections. Thus, a dedicated low-field MR system can be used to detect lung tumors in living mice noninvasively without gating.

Long-term study of ovine pulmonary adenocarcinogenesis in sheep with marginal vs. sufficient nutritional selenium supply: results from computed tomography, pathology, immunohistochemistry, JSRV-PCR and lung biochemistry

The impact of selenium (Se) in carcinogenesis is still debatable due to inconsistent results of observational studies, recent suspicion of diabetic side effects and e.g. dual roles of glutathione peroxidases (GPx). Previously, our group introduced long-term studies on lung carcinogenesis using the jaagtsiekte sheep retrovirus (JSRV) induced ovine pulmonary adenocarcinoma (OPA) as an innovative animal model. The present report describes the results of sufficient (0.2 mg Se/kg dry weight (dw)) vs. marginal (<0.05 mg Se/kg dw) nutritional Se supply on cancer progression over a two-year period in 16 animals. Computed tomography (CT) evaluation of lung cancer progression, final pathological examination, evidence of pro-viral JSRV-DNA in lung, lymph nodes and broncho-alveolar lavage cells as well as biochemical analysis of Se, GPx1 and thioredoxin reductase (TrxR) activity in lung tissue were recorded. Additionally, immunohistochemical determination of GPx1 expression in unaffected and neoplastic lung cells was implemented. The feeding regime caused significant differences in Se concentration and GPx1 activity in lung tissue between groups, whereas TrxR activity remained unaffected. JSRV was evident in broncho-alveolar lavage cells, lung tissue and lung lymph nodes. Quarterly executed CT could not demonstrate differences in lung cancer proliferation intensity. Necropsy and histopathology substantiated CT findings. Immunohistochemical analysis of GPx1 in lung tissue suggested a coherency of GPx1 immunolabelling intensity in dependence of tumour size. It was concluded that the model proved to be suitable for long-term studies of lung cancer proliferation including the impact of modifiable nutritional factors. Proliferation of OPA was unaffected by marginal vs. sufficient nutritional Se supply.

Evaluation of novel orthotopic nude mouse models for human small-cell lung cancer

INTRODUCTION

Although subcutaneous xenograft models have been widely used to evaluate the antitumor activity of new compounds, these models present a major disadvantage because the tumors do not accurately represent the cancer biology, especially with regard to metastasis and drug sensitivity. Effective murine models of small-cell lung cancer (SCLC) are needed.

METHODS

To provide strategies for studying new therapies and tumor biology, we developed three orthotopic models of human SCLC (H69A, a variant of the National Cancer Institute [NCI]-H69 cell line selected for invasiveness in vitro, NCI-H187, and NCI-N417) in nude mice. Tumor cells were injected into their lungs and new cell lines were established from these tumors (H69ALu, H187Lu, and N417Lu) to select for a reproducible tumor growth pattern and minimize variations in tumor size.

RESULTS

In all three models tumors started as a solitary mass in the left lung and spread to mediastinal and axillary lymph nodes and to the right lung in a pattern similar to that observed in human SCLC. To test the accuracy of this model in representing SCLC as seen in the clinic, we compared the efficacy of chemotherapeutic agents in each model. Irinotecan significantly inhibited the growth and progression of all three human SCLC tumors, and cisplatin, paclitaxel, and etoposide significantly inhibited the growth and progression of H69ALu tumors over the control agent.

CONCLUSIONS

We have established three orthotopic murine models of human SCLC closely resembling the course of human SCLC seen in the clinic including metastasis to lymph nodes and distant organs. They provide a means for better understanding the biology of this disease and will enable evaluation of novel therapeutic strategies.

Ovine pulmonary adenocarcinoma as an animal model of progressive lung cancer and the impact of nutritional selenium supply

Jaagsiekte sheep retrovirus (JSRV) is known to induce ovine pulmonary adenocarcinoma (OPA). Several studies have suggested an influence of selenium (Se) status on cancer progression. Thus, combining OPA with a defined Se supply might serve as a suitable animal model to study the impact of Se on lung cancer progression. 16 naturally JSRV-infected sheep were divided into 2 treatment groups receiving (a) <0.05 and (b) 0.2 mg Se/kg dry matter in diet, respectively. Computed tomography (CT) was performed repeatedly and evaluated using a CT-OPA-score system. Liver biopsies were taken three-monthly, blood samples were collected biweekly to study treatment effects on Se concentrations and glutathione peroxidase (GPx) activity. Cell pellets from bronchoalveolar lavage fluid (BALF) were tested for JSRV by PCR to approve the infection. To date, four animals of the ongoing study have been euthanised. Autopsy and histopathology were performed and correlated to CT analysis. JSRV was detected in BALF cell pellets. Progression of lung tumours was monitored successfully by repeated CT examinations, enabling the detection of even small nodules or increased lung density. Histopathology revealed bronchioloalveolar adenocarcinoma in lung areas suspicious to be OPA from CT evaluation. Score-based analysis of CT images for quantifying tumour progression proved as a valuable tool. Se concentration and GPx activity increased in liver and serum of group b and verified the efficiency of different feeding regime. In conclusion, OPA along with CT, autopsy/histopathology, trace element and enzyme activity analysis provide a suitable large animal model to examine the impact of Se supply on lung tumourigenesis.

Tumorigenic study on hepatocytes coexpressing SV40 with Ras

A model of neoplastic transformation by the combination of SV40 large T antigen (LT), SV40 small T antigen (ST), oncogenic Ras, and human telomerase reverse trasncriptase subunit (hTERT) has become established and replicated in primary human fibroblasts, however, there is no report on human hepatocytes. Here we use cell transplantation model, and show that transplantation of human hepatocytes of HL-7702 and HL-7703 expressing Ha-RasV12 and SV40 LT into subrenal capsule of immunodeficient mice results in fully malignant tumors, in contrast to conventional subcutaneous injections where tumors fail to develop. In GM-847 cell study, we have found that hTERT is not required for tumorigenic growth in subrenal capsule transplantation, however, it is required in subcutaneous injection assay. These results demonstrate that Human hepatocytes can be transformed under kidney capsule by coexpressing SV40 LT and Ha-RasV12, neither hTERT nor protein phosphatase 2A (PP2A) inhibition are required for malignant transformation, a gene which increases cell survival in the subcutaneous injection model is not required for tumorigenic growth in subrenal capsule.

Trials, tribulations, and trends in tumor modeling in mice

Selection of mouse models of cancer is often based simply on availability of a mouse strain and a known compatible tumor. Frequently this results in use of tumor models long on history but short on homology and quality control. Other factors including genetics, sex, immunological status, method and site of tumor implantation, technical competence, biological activity of the tumor, protocol sequence and timing, and selection of endpoints interact to produce outcomes in tumor models. Common reliance on survival and tumor burden data in a single mouse model often skews expectations towards high remission and cure rates; a finding seldom duplicated in clinical trials. Inherent limitations of tumor models coupled with the advent of new therapeutic targets reinforce need for careful attention to design, conduct, and stringent selection of in vivo and ex vivo endpoints. Preclinical efficacy testing for anti-tumor therapies should progress through a series of models of increasing sophistication that includes incorporation of genetically engineered animals, and orthotopic and combination therapy models. Pharmacology and safety testing in tumor-bearing animals may also help to improve predictive value of these models for clinical efficacy. Trends in bioinformatics, genetic refinements, and specialized imaging techniques are helping to maintain mice as the most scientifically and economically powerful model of malignant neoplasms.

The difference of angiogenesis in human lung adenocarcinoma cell lines with different metastatic potency

We investigated the ability of angiogenesis in PC9/F9 cells (from a highly metastatic human lung adenocarcinoma cell line) as compared with PC9 cells (from a low metastatic human lung adenocarcinoma cell line). In vivo tumor growth assay using BALB/c nude mice (7 mice/group), showed that the tumor volume of PC9/F9 cells on day 35 (230.7+/-31.3 mm(3)) was significantly larger than that of PC9 cells (90.9+/-24.7 mm(3)) (p<0.001). However, there was no significant difference between PC9/F9 cells and PC9 cells in an in vitro growth assay. In a dorsal air sac assay (DAS assay) using ICR mice (3 mice/group), PC9/F9 cells (4.7+/-1.2 vessels) showed stronger neovascurizationin in compared with PC9 cells (0.3+/-0.4 vessels) (p<0.05). In an enzyme linked immunosorbent assay (ELISA) and Western blotting analysis there were no significant differences between PC9/F9 cells and PC9 cells in the protein expression of vascular endothelial growth factor (VEGF). There was no significant difference between the gene expression levels of PC9/F9 cells and PC9 cells on cDNA array analysis. Matrix metalloproteinase-2 (MMP-2) activity in PC9/F9 cells was remarkably stronger than that of PC9 cells in Gelatin Zymography. From these results, we considered that of the increased metastasis of PC9/F9 cells might be induced by augmented angiogenesis. Furthermore, we speculated that the augmented angiogenesis of the highly metastatic PC9/F9 cell line might be induced by increased MMP-2 activity.

Modeling of lung cancer by an orthotopically growing H460SM variant cell line reveals novel candidate genes for systemic metastasis

Endobronchial implantation of NCI-H460 cells into the nude rat generates a primary lung tumor with mediastinal lymph node spread, but rarely systemic metastases. We isolated tumor cells from mediastinal nodes, orthotopically reimplanted the cells into nude rats and repeated this four times to derive a cell line, designated H460SM, that spontaneously metastasizes to bone, kidney, brain, soft tissue and contralateral lung. H460SM cells demonstrated higher invasive activity in vitro than parental NCI-H460 cells. Spectral karyotyping revealed a new inversion within 17q and loss of an extra normal copy of chromosome 14 present in parental NCI-H460 cells. Expression profiling of orthotopic primary tumors revealed differential expression of 360 genes. Of these, 173 were represented in the probe set of a 19.2K OCI cDNA microarray previously used to profile the gene expression of surgically resected lung cancer specimens. We have computationally validated clinical importance of these genes by using in silico analysis of 18 cases of pulmonary adenocarcinoma, which were split into two patient groups with markedly different clinical outcome. The model identifies additional novel candidate genes for the progression of lung cancer to systemic metastases and poor prognosis.