Reproduction of occult metastasis of head and neck cancer in nude mice

Development of lung metastases in mouse models of tongue squamous cell carcinoma

OBJECTIVE

Oral squamous cell carcinoma (OSCC) represents 3%-4% of all cancers. Despite the increasing incidence of OSCC distant metastasis and poor prognosis, few animal models of OSCC distant metastasis have been reported. In this study, we established mouse models of OSCC lung metastasis by orthotopic and tail vein injection of new OSCC cell lines.

METHODS

For the tail vein model, we used a novel cell line isolated from lung metastases reproduced in vivo after intravenous injection of HSC-3 GFP/luciferase cells and sorted for GFP expression (HSC-3 M1 GFP/luciferase). Lung metastases were assessed by imaging techniques and further confirmed by histology. For the orthotopic model, HSC-3 GFP/luciferase cells were injected into the tongue of athymic nude mice. The primary tumor and metastases were assessed by in vivo imaging, histology, and immunohistochemistry.

RESULTS

The orthotopic model presented spontaneous lung metastases in 50% of the animals and lymph node metastases were present in 83% of cases. In the tail vein model, a lung metastasis rate of 60% was observed.

CONCLUSIONS

Lung metastases were successfully reproduced by orthotopic and tail vein injection. Since lymph node metastases were present, the orthotopic model with HSC-3 GFP/luciferase cells may be suitable to investigate metastatic dissemination in OSCC.

Xenograft models of head and neck cancers

Head and neck cancers are among the most prevalent tumors in the world. Despite advances in the treatment of head and neck tumors, the survival of patients with these cancers has not markedly improved over the past several decades because of our inability to control and our poor understanding of the regional and distant spread of this disease. One of the factors contributing to our poor understanding may be the lack of reliable animal models of head and neck cancer metastasis. The earliest xenograft models in which human tumor cells were grown in immunosuppressed mice involved subcutaneous implantation of human head and neck cancer cell lines. Subcutaneous xenograft models have been popular because they are easy to establish, easy to manage, and lend themselves to ready quantitation of the tumor burden. More recently, orthotopic xenograft models, in which the tumor cells are implanted in the tumor site of origin, have been used with greater frequency in animal studies of head and neck cancers. Orthotopic xenograft models are advantageous for their ability to mimic local tumor growth and recapitulate the pathways of metastasis seen in human head and neck cancers. In addition, recent innovations in cell labeling techniques and small-animal imaging have enabled investigators to monitor the metastatic process and quantitate the growth and spread of orthopically implanted tumors. This review summarizes the progress in the development of murine xenograft models of head and neck cancers. We then discuss the advantages and disadvantages of each type of xenograft model. We also discuss the potential for these models to help elucidate the mechanisms of regional and distant metastasis, which could improve our ability to treat head and neck cancers.

Loss of p53 expression correlates with metastatic phenotype and transcriptional profile in a new mouse model of head and neck cancer

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most frequent cancer worldwide. Because HNSCC is largely acquired by environmental carcinogen exposure rather than through germ line mutations, there are no known familial forms of the disease in humans nor are there inbred rodent strains prone to spontaneous head and neck tumors. Transgenic animals with inactivation of tumor suppressor genes commonly mutated in human cases of HNSCC provide attractive models for studying the pathogenesis of head and neck cancer. p53 is the most frequently inactivated tumor suppressor gene in HNSCC. We used a chemical induction protocol in mice heterozygous for the p53 gene to evaluate how p53 inactivation contributed to head and neck carcinogenesis the mouse model. Metastatic squamous cell carcinomas developed in 100% of animals. Histopathologically, the tumors ranged from well to poorly differentiated and showed many molecular features of human HNSCC. Mice carrying only one p53 allele developed tumors with significantly reduced latency compared with wild-type controls (average, 18 versus 22 weeks). Metastatic cancer cells showed complete loss of p53 expression when compared with primary tumors. Transcriptional profiling showed not only distinct genetic differences between primary and metastatic tumors, but also when cancers from heterozygous null and wild-type animals were compared. Our results provide novel insights into the molecular genetics of tumor progression in head and neck cancer.

An orthotopic floor-of-mouth model for locoregional growth and spread of human squamous cell carcinoma

The molecular investigation of head and neck cancer targets requires the utilization and optimization of established animal models to characterize the effects of gene transcription and protein expression on invasion and metastasis. Floor-of-the-mouth murine models have been developed to study tumor growth, invasion, and metastasis of murine squamous cell carcinoma (SCC) cells in immunocompetent mice and invasion and metastasis of human SCC cells in nude mice. However, there are tumor cell lines that do not produce tumors in mice, using standard techniques, thus reducing the utility of the model to study specific genetic or treatment conditions. Furthermore, these techniques require large tumor volumes raising the possibility of airway compromise. In this report, we detail significant modifications to the orthotopic floor-of-mouth murine model for human SCC to facilitate predictable growth of a large panel of University of Michigan SCC cell lines. Furthermore, we describe the use of bioluminescence and micro-computed tomography to monitor tumor growth and bony invasion.

Animal models for the study of squamous cell carcinoma of the upper aerodigestive tract: a historical perspective with review of their utility and limitations. Part A. Chemically-induced de novo cancer, syngeneic animal models of HNSCC, animal models of transplanted xenogeneic human tumors

Understanding the complex histological, genetic and molecular changes that lead to malignant transformation of squamous epithelia of the head and neck will likely guide the development of methods for improved diagnosis, monitoring and treatment of head and neck squamous cell carcinoma (HNSCC). The development and use of animal models that closely mimic the histopathology and molecular pathogenesis of HNSCC in humans would greatly expand the research possibilities and provide a means of testing potential therapeutic agents. However, many available animal models of HNSCC fall short of this objective. In order for investigators to select the appropriate model to answer scientific questions, it is important to understand the benefits and limitations of available animal models for the study of HNSCC. The purpose of this work is to give an overview of the most pertinent animal models of HNSCC, and to discuss future directions of research in this field.

Effects of fibroblast growth inhibitor on proliferation and metastasis of oral squamous cell carcinoma

Development of a new therapeutic approach to improve the prognosis of high grade invasion of oral squamous cell carcinoma is needed. To elucidate the effect of a fibroblast inhibitor (tranilast), we investigated the proliferation and metastasis of oral squamous cell carcinoma in a mouse model. The effect of tranilast on tumour growth, lymph node metastases, microvessel density, and the proliferating cell nuclear antigen (PCNA) labelling index of oral squamous cell carcinoma implanted into the tongue of nude mice was evaluated. Tumour growth and the incidence of cervical lymph node metastases were significantly suppressed by the administration of tranilast. The amount of fibrous tissue, the microvessel density, and the PCNA labelling index of tumour were also significantly reduced. Administration of a fibroblast inhibitor may well be clinically effective for the treatment of oral squamous cell carcinoma.

Effects of chemotherapy on invasion and metastasis of oral cavity cancer in mice

BACKGROUND

Using an orthotopic implantation model in which oral cancer invasion and metastasis can be reproduced, we investigated the inhibitory effects of anticancer agents on invasion and metastasis.

METHODS

A highly invasive and metastatic human oral squamous cell carcinoma cell line, OSC-19, was implanted into the oral floor of nude mice, and cisplatin or peplomycin was administered to the mice 7 or 14 days after implantation. The effects of each anticancer drug and different administration timings on cancer invasion and metastasis were investigated.

RESULTS

Tumor size and the ratio of proliferating cell nuclear antigen-positive cells was significantly reduced. In the control group, the tumors showed grade 4C mode of invasion, whereas in the groups treated with anticancer drugs, grade 3 was observed in 77.3% of the mice, with an inhibitory effect on tumor invasion being observed. The rate of metastasis in the cervical lymph node was significantly decreased in the groups treated with the cisplatin or peplomycin on day 7 after implantation. The tumor stage progression in the metastatic lymph nodes was also inhibited.

CONCLUSIONS

Chemotherapy is effective not only for tumor diminution but also for inhibiting invasion and metastasis. In light of these effects, administration of anticancer drugs may be clinically useful in this regard.