TRIM59 promotes gliomagenesis by inhibiting TC45 dephosphorylation of STAT3

Although the oncogenic signalings driven by amplification and mutations of EGF receptor (EGFR) gene play a major role in glioblastoma pathogenesis, the responsible downstream mechanisms remain less clear. Here we demonstrate that tripartite motif-containing protein 59 (TRIM59), acting as a new downstream effector of EGFR signaling, regulates STAT3 activation in glioblastoma. EGFR signaling leads to TRIM59 upregulation through SOX9 that results in enhancing TRIM59 interaction with STAT3 in nucleus, and inhibiting STAT3 association with TC45 (the nuclear form of T cell protein tyrosine phosphatase TC-PTP), thereby maintaining STAT3 phosphorylation and activation and promoting tumorigenesis. Silencing TRIM59 suppresses cell proliferation, migration, and orthotopic xenograft brain tumorigenesis of GBM cells. Moreover, evaluation of GBM patient samples reveals an association among EGFR activation, TRIM59 expression, STAT3 phosphorylation, and poor prognoses. Our study identifies TRIM59 as a new regulator of oncogenic EGFR-STAT3 signaling and a potential therapeutic target for GBM patients with EGFR activation. Examination of effects of TRIM59 knockdown on differential gene expression in glioma cells with EGFRvIII overexpression.