Pfetin as a prognostic biomarker of gastrointestinal stromal tumors revealed by proteomics.

ABSTRACT

PURPOSE: We aimed to develop prognostic biomarkers for gastrointestinal stromal tumors (GIST) using a proteomic approach. EXPERIMENTAL DESIGN: We examined the proteomic profile of GISTs using two-dimensional difference gel electrophoresis. The prognostic performance of biomarker candidates was examined using a large-scale sample set and specific antibodies. RESULTS: We identified 43 protein spots whose intensity was statistically different between GISTs with good and poor prognosis. Mass spectrometric protein identification showed that the 43 spots corresponded to 25 distinct gene products. Eight of the 43 spots derived from pfetin, a potassium channel protein, and four of the eight pfetin spots had a high discriminative power between the two groups. Western blotting and real-time PCR showed that pfetin expression and tumor metastasis were inversely related. The prognostic performance of pfetin was also examined by immunohistochemistry on 210 GIST cases. The 5-year metastasis-free survival rate was 93.9% and 36.2% for patients with pfetin-positive and pfetin-negative tumors, respectively (P < 0.0001). Univariate and multivariate analyses revealed that pfetin expression was a powerful prognostic factor among the clinicopathologic variables examined, including risk classification and c-kit- or platelet-derived growth factor receptor A mutation status. CONCLUSIONS: These results establish pfetin as a powerful prognostic marker for GISTs and may provide novel therapeutic strategies to prevent metastasis of GIST.