Development and characterization of a preclinical ovarian carcinoma model to investigate the mechanism of acquired resistance to trastuzumab.

Trastuzumab (Herceptin®) is a humanized monoclonal antibody designed to bind and inhibit the function of the human epidermal growth factor receptor 2 (HER2)/erbB2 receptor. Trastuzumab has demonstrated clinical activity in several types of HER2-overexpressing epithelial tumors, such as breast and metastatic gastric or gastroesophageal junction cancer. Relapse and therapeutic resistance, however, still occur in a subset of patients treated with regimens including trastuzumab, despite significant improvements in response rates, survival and quality of life.

Autoinhibition of the platelet-derived growth factor beta-receptor tyrosine kinase by its C-terminal tail.

In this report, we investigated the role of the C-terminal tail of the platelet-derived growth factor (PDGF) beta-receptor in the control of the receptor kinase activity. Using a panel of PDGF beta-receptor mutants with progressive C-terminal truncations, we observed that deletion of the last 46 residues, which contain a proline- and glutamic acid-rich motif, increased the autoactivation velocity in vitro and the V(max) of the phosphotransfer reaction, in the absence of ligand, as compared with wild-type receptors. By contrast, the kinase activity of mutant and wild-type receptors that were pre-activated by treatment with PDGF was comparable.

Glycosylation-induced conformational modification positively regulates receptor-receptor association: a study with an aberrant epidermal growth factor receptor (EGFRvIII/DeltaEGFR) expressed in cancer cells.

The epidermal growth factor receptor (EGFR) is a multisited and multifunctional transmembrane glycoprotein with intrinsic tyrosine kinase activity. Upon ligand binding, the monomeric receptor undergoes dimerization resulting in kinase activation. The consequences of kinase stimulation are the phosphorylation of its own tyrosine residues (autophosphorylation) followed by association with and activation of signal transducers.

Role of conformational alteration in the epidermal growth factor receptor (EGFR) function.

This mini-review addresses the effect of glycosylation and phosphorylation on the conformational alterations of the epidermal growth factor receptor (EGFR). Based on studies with full-length and truncated EGFRs, we propose a model to suggest that receptor-receptor self-association, which occurs in the truncated receptor and depends on core glycosylation, is prevented in intact receptor by a certain extracellular domain and that the function of the ligand is to remove the negative constraint. We also propose, based on works with a conformation-specific antibody directed to an unphosphorylated peptide, that the interactions among negatively charged phosphotyrosine residues in the receptor molecule result in bringing two epitopes separated by a long stretch of amino acids close to each other to form an antibody-binding site.

Conformational analysis of the phosphorylated epidermal growth factor receptor.

Phosphorylation-induced conformational changes have been well documented with different receptor tyrosine kinases. However. the susceptible epitopes and the tyrosine residue(s) involved in particular structural alteration mostly remain to be determined.