Insights on neoplastic stem cells from gel-based proteomics of childhood germ cell tumors

Background: Childhood germ cell tumors (cGCTs), believed to arise from transformed primordial germ cells by an unknown mechanism, provide a unique model system for investigating cell signaling, pluripotency, and the microenvironment of neoplastic stem cells (NSCs) in vivo. This is the first report of proteomics of cGCTs. Procedure : Four dysgerminomas (DYSs) and four childhood endodermal sinus tumors (cESTs), resembling self-renewing and differentiating NSCs, respectively, were selected. Proteomic studies were performed by 2-DE, SDS-PAGE, and cLC/MS/MS with protein database searching. Results : 2-DE: 9 of 941 spots were differentially regulated with greater than a twofold change in spot volume for at least three of four gels in each group. Two of nine spots had P values for the t-test analysis of comparisons less than 0.001, while the remaining spots had P values from 0.013 to 0.191. Top-ranked proteins were identified in nine of nine spots with 4.0-38% sequence coverage. APOA1, CRK, and PDIA3 were up-regulated in cESTs. TFG, TYMP, VCP, RBBP, FKBP4, and BiP were up-regulated in DYSs. SDS-PAGE: Up-regulation of NF45 and FKBP4 was observed in four of four cESTs and DYSs, respectively. The fold-changes observed correspond with characteristic genetic changes. Conclusion : Differential regulation of FKBP4 and NF45, combined with previous research on immunosuppressant binding, suggests that glucocorticoid receptor signaling merits further investigation in cGCTs and NSCs.