Cooperative but distinct early co-signaling events originate from ERBB2 and ERBB1 receptors upon trastuzumab treatment in breast cancer cells.

Paola Bagnato,Silvia Grasso,Paola Defilippi,Tiziana Daniele,Richard Lundmark,Patrizio Castagnola,Alessia Castagnino,Grazia Bellese,Katia Cortese,Maria Bono,Carlo Tacchetti

doi:10.18632/oncotarget.17686

Abstract

ERBB2 receptor belongs to the ERBB tyrosine kinase receptor family. At variance to the other family members, ERBB2 is a constitutively active orphan receptor. Upon ligand binding and activation, ERBB receptors form homo- or hetero-dimers with the other family members, including ERBB2, promoting an intracellular signaling cascade. ERBB2 is the preferred dimerization partner and ERBB2 heterodimers signaling is stronger and longer acting compared to heterodimers between other ERBB members. The specific contribution of ERBB2 in heterodimer signaling is still undefined.Here we report the formation of circular dorsal ruffles (CDRs) upon treatment of the ERBB2-overexpressing breast cancer cell lines SK-BR-3 and ZR751 with Trastuzumab, a therapeutic humanized monoclonal antibody directed against ERBB2. We found that in SK-BR-3 cells Trastuzumab leads to surface redistribution of ERBB2 and ERBB1 in CDRs, and that the ERBB2-dependent ERK1/2 phosphorylation and ERBB1 expression are both required for CDR formation. In particular, in these cells CDR formation requires activation of both the protein regulator of actin polymerization N-WASP, mediated by ERK1/2, and of the actin depolymerizing protein cofilin, mediated by ERBB1. Furthermore, we suggest that this latter event may be inhibited by the negative cell motility regulator p140Cap, as we found that p140Cap overexpression led to cofilin deactivation and inhibition of CDR formation.In conclusion, here we show for the first time an ERBB2-specific signaling contribution to an ERBB2/ERBB1 heterodimer, in the activation of a complex biological process such as the formation of CDRs.

Highlights

ERBB2 (Her2/Neu) is a member of the ERBB family of receptor tyrosine kinases (RTKs), which includes EGFR (ERBB1), ERBB3, and ERBB4
We found that in SK-BR-3 cells Trastuzumab leads to surface redistribution of ERBB2 and ERBB1 in circular dorsal ruffle (CDR), and that the ERBB2-dependent ERK1/2 phosphorylation and ERBB1 expression are both required for CDR formation
To characterize early events occurring at the level of the plasma membrane (PM) upon Tz binding to ERBB2, we analyzed the breast cancer cell line SK-BR-3, in a time range between 2 and 120 min of treatment with Tz

Summary

Introduction

ERBB2 (Her2/Neu) is a member of the ERBB family of receptor tyrosine kinases (RTKs), which includes EGFR (ERBB1), ERBB3, and ERBB4. ERBB2 is an orphan receptor and is the preferred dimerization partner for ERBB1, 3, and 4, upon their activation following the binding to specific ligands, e.g. EGF, TGF-α, and amphiregulin (for EGFR), or Heregulins/Neuregulins (for ERBB3/4) [1,2,3]. The oncogenic signaling by ERBB2 www.impactjournals.com/oncotarget [4, 5] is thought to involve the sustained activation of a number of signaling pathways, including the Ras-RafMAPK, which contributes to cell proliferation, and the PI3K-AKT, which induces cell survival [2, 6, 7]. The precise contribution of ERBB2 to the heterodimer signaling is not clear yet. Evidence suggests that in the absence of ERBB2 containing heterodimers, ERBB agonists elicited a weaker and curtailed signaling response [9]

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Conclusion