Overexpression of β2-microglobulin is associated with poor survival in patients with oral cavity squamous cell carcinoma and contributes to oral cancer cell migration and invasion

beta 2-Microglobulin (beta 2M), a component of MHC class I molecules, is believed to be associated with tumour status in various cancers. In this study, we examined the expression of beta 2M at different malignant stages of oral cavity squamous cell carcinoma (OCSCC). To determine the possible correlation between beta 2M expression and various clinical characteristics, 256 samples from patients with OCSCC were evaluated by immunohistochemical staining. Strong beta 2M expression was significantly correlated with a relatively advanced tumour stage (P < 0.001), positive nodal status (P < 0.001), and TNM stage (P < 0.001). The cumulative 5-year survival rate was significantly correlated with a relatively advanced tumour stage (P < 0.001), positive nodal status (P < 0.001), TNM stage (P < 0.001), and strong expression of beta 2M (P < 0.001). Thus, elevated beta 2M expression is an indicator of poor survival (P < 0.001). In addition, we extended our analysis of beta 2M expression to the FaDu and SCC25 oral cancer cell lines. beta 2-Microglobulin expression was positively correlated with cell migration and invasion in beta 2M-overexpressing transfectants in Transwell chambers. The suppression of beta 2M expression using small interfering RNA (siRNA) was sufficient to decrease cell migration and invasion in vitro. Taken together, our results suggest that beta 2M expression in the tissues is associated with survival and may be involved in tumour progression and metastasis in OCSCC.