EGFR Phosphorylates Tumor-Derived EGFRvIII Driving STAT3/5 and Progression in Glioblastoma

Abstract

SUMMARY EGFRvIII, a frequently occurring mutation in primary glioblastoma, results in a protein product that cannot bind ligand, but signals constitutively. Deducing how EGFRvIII causes transformation has been difficult because of autocrine and paracrine loops triggered by EGFRvIII alone or in heterodimers with wild-type EGFR. Here, we document co-expression of EGFR and EGFRvIII in primary human glioblastoma that drives transformation and tumorigenesis in a cell-intrinsic manner. We demonstrate enhancement of downstream STAT signaling triggered by EGFR-catalyzed phosphorylation of EGFRvIII, implicating EGFRvIII as a substrate for EGFR. Subsequent phosphorylation of STAT3 requires nuclear entry of EGFRvIII and formation of an EGFRvIII-STAT3 nuclear complex. Our findings clarify specific oncogenic signaling relationships between EGFR and EGFRvIII in glioblastoma.

Epidermal Growth Factor Receptor Variant III (EGFRvIII) Positivity in EGFR-Amplified Glioblastomas: Prognostic Role and Comparison between Primary and Recurrent Tumors

“…However, previous studies reported that EGFR amplification may be restricted to subpopulations of tumor cells, as determined in cases of glioblastomas with amplification of EGFR and PDGFRA (52,53). With respect to EGFRvIII expression, our data demonstrate that EGFRvIII immunopositivity shows marked regional heterogeneity and is often restricted to subpopulations of tumor cells in glioblastomas, thus confirming previous findings in the GGN patient cohort (17) and in several independent studies (39,42,43,51,54).…”

“…Accumulating preclinical evidence has attributed an important function of EGFRvIII-expressing glioblastoma cells in driving tumor heterogeneity and progression by promoting glioma cell proliferation, invasion, angiogenesis, stemness, and therapy resistance in different model systems (36)(37)(38)(39)(40)(41)(42)(43). In addition, several therapeutic approaches targeting overexpressed wild type EGFR protein or specifically EGFRvIII have already entered, or are about to enter clinical evaluation, including peptide-based vaccines (44)(45)(46), chimeric antigen receptor (CAR) T cells (47,48), as well as anti-EGFR antibodybased approaches (22,49,50).…”

Assessment and prognostic significance of the epidermal growth factor receptor vIII mutation in glioblastoma patients treated with concurrent and adjuvant temozolomide radiochemotherapy

“…Additional evidence for the specificity of the antibodies used for the detection of EGFRvIII and EGFR wild type proteins has previously been provided by immunofluorescence staining of glioma cells stably transfected with either EGFR wild type, EGFRvIII or both. 18 Extraction of nucleic acids DNA and RNA were extracted from frozen tumor tissue samples by ultracentrifugation over caesium chloride as described elsewhere. 19 The RNeasy FFPE Kit (Qiagen, Hilden, Germany) was used for RNA extraction from formalin-fixed paraffin-embedded (FFPE) tumor tissue samples.…”

Cucurbitacin-I inhibits Aurora kinase A, Aurora kinase B and survivin, induces defects in cell cycle progression and promotes ABT-737-induced cell death in a caspase-independent manner in malignant human glioma cells

“…The EGFR/JAK/STAT pathway has generated significant interest as a key driver of tumor cell survival, proliferation, and invasion in GBM. 38 Recently, using subcellular fractionation, Fan, et al 69 demonstrated that receptor phosphorylation of EGFRviii led to nuclear transport of EGFRviii and enhanced the formation of a complex between EGFRviii and STAT5. This complex serves as a transcriptional co-activator for a series of tumor-promoting genes such as cyclin D1, iNOS, B-myb, Aurora kinase and Cox-2.…”