Pfetin as a prognostic biomarker in gastrointestinal stromal tumor: Novel monoclonal antibody and external validation study in multiple clinical facilities

Objective: The clinical course of gastrointestinal stromal tumor (GIST) spans a wide spectrum from a curable disorder to a highly malignant disease that leads to metastasis and death. To develop prognostic modalities for GIST patients, we developed a mouse monoclonal antibody against pfetin, the prognostic value of which has been previously reported. Methods: The reactivity of the monoclonal antibody against pfetin was examined by western blotting and immunohistochemistry. Results: Western blotting demonstrated that the monoclonal antibody was specific to pfetin. The immunohistochemical study demonstrated that the 5-year disease-free survival rate was 93.2% and 94.5% for GIST patients with pfetin-positive tumors and 70.0% and 80.7% for those with pfetin-negative tumors in the 159 cases from the National Cancer Center Hospital (P < 0.0001) and in the 100 cases from Niigata University Medical and Dental Hospital (P < 0.0001), respectively. Uni- and multivariate analyses revealed that pfetin expression was a powerful prognostic factor among the clinico-pathological parameters examined. Conclusions: These results establish pfetin as a practical prognostic marker for GIST patients after surgery. Pfetin may also present a novel therapeutic target to prevent recurrence of GIST.