1582 Background: Glioblastoma is the most malignant astrocytic tumor and accounts for about 50–60% of all astrocytic neoplasms. Despite intensive radiation and chemotherapy, less than 2% of patients survive more than 3 years. The Erb family of signaling molecules are transmembrane receptors with intrinsic kinase activity (except ErbB3) capable of modifying tyrosine residues on the receptor itself as well as on downstream signaling molecules. Under physiological conditions a variety of ligands interact and act as driving forces in the formation of homo and heterodimeric complexes between the four receptors leading to signal amplification and downstream activities. More than one third of glioblastoma cases show gene amplification of epidermal growth factor receptor (EGFR) which can be in truncated or rearranged form. The eTag assay system (Monogram) is an antibody based fluorescent assay that has the potential to assess the activation state of the EGFR signaling pathway. Methods: Twenty three cases of glioblastoma were selected for eTag analysis. There were twelve males and eleven females with ages ranging from 20–84 years. After reviewing the histology, 10 micron sections were cut from formalin fixed paraffin embedded (FFPE) tumor tissue blocks. Specific monoclonal antibodies of the Erb family bound to a fluorescent reporter (eTag) were applied to tissue sections. After binding of specific analyte, a second monoclonal antibody is added which acts as molecular scissors resulting in cleavage of “eTags”. The released eTag molecules are separated by capillary electrophoresis and measured as relative fluorescent units. Various FFPE tumor cell lines were used as controls. Results: Nineteen out of twenty three tumors (82%) showed the presence of dimers of the Erb family signaling pathway. High levels of intra and /or extracellular EGFR homodimers (HER-1-HER-1) were detected in eight samples (35%). EGFR-HER-3 dimers and EGFR-HER-2 dimers were seen at high levels in four and six samples (17% and 26% respectively). High levels of HER-2-HER3 dimers were detected in six samples (26%). Conclusion: The EGFR signaling pathway plays a substantial role in tumorigenesis of glioblastoma. Identification of receptor homo and heterodimers may be of value during treatment planning of individual patients. No significant financial relationships to disclose.
EGFR signaling pathway occupies an important position in cancer‐related downstream signaling pathways of Pyk2