Calreticulin is a novel independent prognostic factor for oral squamous cell carcinoma

We focused on the expression of Calreticulin (CALR) in oral squamous cell carcinoma (OSCC) on the basis of proteomic differential display analysis data. We used QR-32 cells in this study which is a regressive murine fibrosarcoma cell clone; and QRsP-11, a progressive malignant tumor cell clone originated from QR-32. CALR is an endoplasmic reticulum luminal Ca²⁺-binding chaperone protein, which is thought to affect the tumor behavior of various malignancies. This study was aimed to determine the usefulness of CALR as a prognostic factor in patients with OSCC. We investigated the expression of CALR in tissue samples taken from 111 OSCC patients by immunohistochemistry, and we also analyzed the relationship between CALR expression and patients' clinicopathological characteristics as well as patient survival. Positive immunohistchemical staining of CALR was observed in the cancer cell cytoplasm. Among 111 patients, high expression of CALR was observed in 44 patients (39.6%), whereas low expression was observed in 67 patients (60.4%). Significant association was found between CALR expression and T classification (P=0.0027), N classification (P=0.0219), stage (P=0.0013), and patient outcome (P=0.0014). Log-rank test showed that, there is a significant difference (P<0.0001) in 5-year survival rates between patients showing CALR high-expression (59.1%) and CALR low-expression (86.6%). According to our Multivariate analysis, reduced term survival of patients was correlated to high levels of CALR expression (P<0.0001). Our findings suggest that elevated expression of CALR might play an important role in tumor progression in OSCC, and could be considered as a useful prognostic factor in OSCC patients.