Elevated Expression of Calpain-4 Predicts Poor Prognosis in Patients with Gastric Cancer after Gastrectomy

Calpain-4 belongs to the calpain family of calcium-dependent cysteine proteases, and functions as a small regulatory subunit of the calpains. Recent evidence indicates that calpain-4 plays critical roles in tumor migration and invasion. However, the roles of calpain-4 in gastric tumorigenesis remain poorly understood. Herein, we examined calpain-4 expression by immunohistochemical staining on tissue microarrays containing tumor samples of 174 gastric cancer patients between 2004 and 2008 at a single center. The Kaplan-Meier method was used to compare survival curves, and expression levels were correlated to clinicopathological factors and overall survival. Our data demonstrated that calpain-4 was generally increased in gastric cancer cell lines and primary tumor tissues. High expression of calpain-4 was positively associated with vessel invasion, lymph node metastasis, and advanced TNM (Tumor Node Metastasis) stage. Multivariate analysis identified calpain-4 as an independent prognostic factor for poor prognosis. A predictive nomogram integrating calpain-4 expression with other independent prognosticators was constructed, which generated a better prognostic value for overall survival of gastric cancer patients than a TNM staging system. In conclusion, calpain-4 could be regarded as a potential prognosis indicator for clinical outcomes in gastric cancer.