OSCC is a common oral cancer and metastasis and recurrence are two characteristics of OSCC. Despite advances in treatment and diagnostics the incidence and mortality in patients with OSCC are increasing. The tumorigenesis of OSCC is a complex multi-step process which associated with the dysregulation of oncogenes and tumor suppressor genes [15]. In addition, most OSCC patients are diagnosed at advanced stages, and the routine therapeutic methods are not effective for them [16]. Early diagnosis may improve the prognosis and treatments of OSCC. Therefore, there is an urgent requirement to identify novel bio-markers for the diagnosis, therapy and prognosis of OSCC.
Cortactin protein possess a multi-domain structure consisting of an acidic domain at the amino terminus, a proline-rich helical region and an Src homology SH3 domain located at the carboxyl terminus [17, 18]. Cortactin protein was initially considered as a substrate of Src protein kinase and a cytoskeletal protein that plays a potential role in the regulation of the actin cytoskeleton, actin assembly and adhesion [19]. Besides, cortactin protein was involved in the pathogenesis and development of some human tumors. In the study of Zhao et al., increased expression of cortactin was observed in hepatoma carcinoma (HCC) cells, and it regulated the invasion and migration of HCC cells [20]. Ni et al. mentioned that cortactin was higher in colon cancer tissues than that in adjacent non-tumor tissues, and over-expression of cortactin enhanced cell colony formation and tumor growth [21].
In the present study, the qRT-PCR results showed that the relative expression of cortactin in OSCC tissues was significantly up-regulated compared with that in adjacent normal tissues at mRNA level, which was similar to previous studies [20, 21]. It revealed that cortactin gene might play an oncogenic role and exhibit tissue-specific in OSCC. Moreover, increased expression of cortactin was more frequently occurred in patients with larger tumor size, advanced TNM stage, positive lymph node metastasis and recurrence. According to these results, we hypothesized that cortactin expression might be involved in the development of OSCC. Our findings were consistent with the previous studies, for example, Lu et al. reported that the mRNA expression level of cortactin gene was over-expressed in esophageal squamous cell carcinoma and associated with tumor stage as well as lymph node metastasis of patients [22]. In head and neck squamous cell carcinoma, patients with positive cortactin expression tended to have recurrence or metastasis [23]. Nevertheless, a study carried out by Tsai et al. showed that the immunostaining scores of cortactin was obviously linked with histological grade of pancreatic and ampulla of Vater adenocarcinoma patients, which was inconsistent with our result [24]. The functions of cortactin in different cancers might be varied, and the sample size, its source as well as expression pattern might also cause the difference.
A large number of researches had demonstrated that cortactin was correlated with the prognosis of various tumors, including OSCC [25-27]. In the study of Li et al., they reported that the negative expression of cortactin was an independent prognostic factor and had a survival advantage in epithelial ovarian cancer [28]. Cortactin was demonstrated to be an important indicator of the malignancy and metastasis of liver cancer and might have predictive value in the prognosis of HCC [27, 29]. However, little is known about the diagnostic value of cortactin in OSCC. In this study, the result of ROC curve analysis indicated that cortactin mRNA expression could be a potential bio-marker for the diagnosis of OSCC patients with high values of AUC, sensitivity and specificity.