Abstract
Frequent metastasis to the cervical lymph nodes leads to poor survival of patients with oral squamous cell carcinoma (OSCC). To understand the underlying mechanisms of lymph node metastasis, two sublines were successfully isolated from cervical lymph nodes of nude mice through in vivo selection, and identified as originating from poorly metastatic parental cells. These two sublines specifically metastasized to cervical lymph nodes in 83% of mice, whereas OEC-M1 cells did not metastasize after injection into the oral cavity. After gene expression analysis, we identified insulin-like growth factor binding protein 3 (IGFBP3) as one of the significantly up-regulated genes in the sublines in comparison with their parental cells. Consistently, meta-analysis of the public microarray datasets and IGFBP3 immunohistochemical analysis revealed increased both levels of IGFBP3 mRNA and protein in human OSCC tissues when compared to normal oral or adjacent nontumorous tissues. Interestingly, the up-regulated IGFBP3 mRNA expression was significantly associated with OSCC patients with lymph node metastasis. IGFBP3 knockdown in the sublines impaired and ectopic IGFBP3 expression in the parental cells promoted migration, transendothelial migration and lymph node metastasis of orthotopic transplantation. Additionally, ectopic expression of IGFBP3 with an IGF-binding defect sustained the IGFBP3-enhanced biological functions. Results indicated that IGFBP3 regulates metastasis-related functions of OSCC cells through an IGF-independent mechanism. Furthermore, exogenous IGFBP3 was sufficient to induce cell motility and extracellular signal-regulated kinase (ERK) activation. The silencing of integrin β1 was able to impair exogenous IGFBP3-mediated migration and ERK phosphorylation, suggesting a critical role of integrin β1 in IGFBP3-enchanced functions.
Highlights
Oral squamous cell carcinoma (OSCC) is one of the most frequent cancers worldwide, with more than half a million patients being diagnosed annually [1]
By analyzing the differentiated gene expression, we identified insulin-like growth factor binding protein 3 (IGFBP3) as one such up-regulated gene that might participate in tumorigenesis and lymph node metastasis of OSCC
Based on the previous studies showing that small GTPase is the downstream effectors of integrin– mediated cell migration, we further explore whether IGFBP3-induced migration was mediated by integrin β1, which is interacting with IGFBP3 as shown previously [35,36,37,38,39]
Summary
Oral squamous cell carcinoma (OSCC) is one of the most frequent cancers worldwide, with more than half a million patients being diagnosed annually [1]. Patients with lymph node metastasis have a markedly worse prognosis than patients without metastasis. The 5-year overall survival rates for OSCC patients are approximately 80% for patients without lymph node metastasis and 45% for patients with lymph node metastasis [2]. An accurate assessment of the cervical lymph node metastasis status in OSCC helps predict the prognosis of patients, and benefits for the appropriate treatment. Understanding the pathophysiology of lymph node metastasis of OSCC is important for early diagnosis and treatment. Precise molecular mechanisms of lymph node metastasis have not been elucidated, partly due to the lack of consistent and reproducible animal models
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