Development of a 4-nitroquinoline-1-oxide model of lymph node metastasis in oral squamous cell carcinoma

Objectives: Lymph node metastasis is one of the most important prognostic factors in oral squamous cell carcinoma. However, regional lymph node metastasis from oral cancer has barely been investigated in 4-nitroquinoline-1-oxide (4NQO) models. In this study, we developed a 4NQO-treated mouse model of oral squamous cell carcinoma that displayed lymph node metastasis and examined the occurrence and timing of the lymph node metastasis. Materials and methods: BALB/c mice were treated with 200 mu g/ml 4NQO in drinking water for 20 weeks and then followed for 4 weeks. Four mice were sacrificed bi-weekly, and oral lesion and regional lymph node metastasis were assessed during the week 25-32 and week 33-40 observation periods. Results: Tumor formation and local lymph enlargement were observed from 25 weeks onwards. The presence of metastatic tumor cells in the enlarged lymph nodes was confirmed via the detection of tumor infiltration by HE staining and cytokeratin positivity by immunostaining at both 28 and 36 weeks. The incidence rates of oral squamous cell carcinoma and local lymph node metastasis were 68.8% and 12.5% in the week 25-32 observation period, and 100% and 100% in the week 33-40 observation period, respectively. Conclusions: A lymph node metastasis model involving mice being subjected to high-dose 4NQO treatment for a long period and then followed for a prolonged period was established. This model might provide a platform for studying the mechanism of lymphatic metastasis in oral carcinoma, leading to the development of new therapies for advanced oral carcinoma. (C) 2012 Elsevier Ltd. All rights reserved.