DJ-1 Is Upregulated in Oral Squamous Cell Carcinoma and Promotes Oral Cancer Cell Proliferation and Invasion

BACKGROUND The development of oral squamous cell carcinoma (OSCC) is a multistep process that involves in both genetic alterations and epigenetic modifications. DJ-1, a negative regulator of tumor suppressor PTEN, functions as an oncogene in many types of cancers. However, its role in OSCC is poorly known. METHODS Immunohistochemical staining and Western blotting were performed to evaluate the expression level of DJ-1 in oral leukoplakia (OLK) and OSCC tissues respectively. Then lentiviral mediated DJ-1 shRNA was constructed and used to infect the OSCC cell lines (Tca8113 and CAL-27). MTT, cell counting, and Matrigel invasion assay were utilized to examine the effects of DJ-1 down-regulation on proliferation and invasion capacity of oral cancer cells. RESULTS The immunoreactivity and expression level of DJ-1 protein was significantly increased in OLK and OSCC tissues compared with the controls. Lentiviral-delivered shRNA targeting DJ-1 could effectively knock down DJ-1 at mRNA and protein level (P<0.01). The proliferative and invasion ability of OSCC cell lines was significantly suppressed following DJ-1 inhibition (P<0.01). CONCLUSIONS Our study indicated that DJ-1 is over-expressed in both oral precancer and cancer tissues and shRNA inhibition of DJ-1 expression led to decreased proliferation and invasion capability of oral cancer cells. These findings suggest that DJ-1 might be actively involved in the development of OSCC. Future studies will investigate the potential of DJ-1 as a biomarker for early detection of OSCC.