A Conformationally Constrained Peptidomimetic Binds to the Extracellular Region of HER2 Protein

Abstract

Human epidermal growth factor receptor 2 (HER2) is a member of the human epidermal growth factor receptor kinases (other members include EGFR or HER1, HER3, and HER4) that are involved in signaling cascades for cell growth and differentiation. It is well established that HER2-mediated heterodimerization has important implications in cancer. Deregulation of signaling pathways and overexpression of HER2 is known to occur in cancer cells, indicating a role of HER2 in tumorigenesis. Therefore, blocking HER2-mediated signaling has potential therapeutic value. We have designed several peptidomimetics to inhibit HER2-mediated signaling for cell growth. One of the compounds (HERP5, Arg-βNaph-Phe) exhibited antiproliferative activity with IC50 values in the micromolar-to-nanomolar range in breast cancer cell lines. Binding of fluorescently labeled HERP5 to HER2 protein was evaluated by fluorescence assay, microscopy, and circular dichroism spectroscopy. Results indicated that HERP5 binds to the extracellular region of the HER2 protein. Structure of the peptidomimetic HERP5 was studied by NMR and molecular dynamics simulations. Based on these results a model was proposed for HER2-EGFR dimerization and possible blocking by HERP5 peptidomimetic using a protein-protein docking method.

Structure–activity relationship of conformationally constrained peptidomimetics for antiproliferative activity in HER2-overexpressing breast cancer cell lines

“…The lead compound 5 was shown to be highly selective for HER2-overexpressing cell lines, with an IC 50 value of 0.396 μM in SKBR-3 and 0.896 μM in BT-474 pcell lines and 16.9 μM in MCF-7 cell lines. 28,29 To evaluate the effect of R1 and R3 flanking residues of the central β-amino acid, peptidomimetics with different functional groups at R1 and R3 were evaluated (Table 1). Replacement of the C-terminal amino acid Phe with Tyr (a hydrophibic group with a hydroxyl group) (compound 6 ) or a negatively charged acidic side chain (compound 7 ) resulted in a loss of activity.…”

“…28 We have also shown that a peptidomimetic (compound 5 ) exhibits antiproliferative activity in the lower micromolar range and specifically binds to HER2-overexpressing breast cancer cells. 29 To further investigate the structure-activity relationship of compound 5 and its analogs, we investigated the inclusion of different functional groups (amino acids or β-amino acids) in the peptidomimetic and studied their antiproliferative activity in breast cancer cell lines. Conformational constraints were introduced by incorporating a Pro residue in the peptidomimetic sequence.…”

Design, synthesis and characterization of peptidomimetic conjugate of BODIPY targeting HER2 protein extracellular domain

“…The crystal structures of homodimers of EGFR suggest that hydrophobic residues such as Leu582, Trp584, and Tyr602 participate in PPI of domain IV to stabilize the interaction of homodimers of EGFR near the transmembrane [26]. The results from our current and previous studies [28, 30] clearly suggest that a peptidomimetic that we designed targets domain IV and inhibits PPI in vitro as seen in the PLA assay. This inhibition in turn has the pharmacological action of inhibition of phosphorylation of the kinase domain and, hence, modulation of the signal for cell growth.…”

Current and future targeted therapies for non-small-cell lung cancers with aberrant EGF receptors

“…The region of PPI and its inhibition is marked by an oval shape. The model of EGFR:HER2 heterodimer was generated [108,109] using the crystal structures of EGFR (PDB ID 3NJP) [110] and HER2 (PDB ID) [111] with a homodimer of EGFR as a template (PDB ID 3NJP). EGFR: EGF receptor; PPI: Protein–protein interaction.…”