A Critical Role for HSP90 in Cancer Cell Invasion Involves Interaction with the Extracellular Domain of HER-2

Abstract

HSP90 is a ubiquitously expressed molecular chaperone that controls the folding, assembly, intracellular disposition, and proteolytic turnover of many proteins, most of which are involved in signal transduction processes. Recently, a surface form of HSP90 has been identified and associated with cell migration events. In this paper, we explore the interaction of surface HSP90 with HER-2, a receptor-like glycoprotein and member of the ErbB family of receptor tyrosine kinases that play central roles in cellular proliferation, differentiation, and migration as well as in cancer progress. The involvement of HSP90 in the regulation of HER-2 has been attributed so far to receptor stabilization via interaction with its cytoplasmic kinase domain. Here we present evidence, using glutathione S-transferase pull-down and transfection assays, for a novel interaction between surface HSP90 and the extracellular domain of HER-2. Specific disruption of this interaction using mAb 4C5, a function-blocking monoclonal antibody against HSP90, inhibits cell invasion accompanied by altered actin dynamics in human breast cancer cells under ligand stimulation conditions with heregulin. Additionally, disruption of surface HSP90/HER-2 interaction leads to inhibition of heregulin-induced HER-2-HER-3 heterodimer formation, reduced HER-2 phosphorylation, and impaired downstream kinase signaling. Interestingly, this disruption does not affect HER-2 internalization. Our data suggest that surface HSP90 is involved in heregulin-induced HER-2 activation and signaling, leading to cytoskeletal rearrangement, essential for cell invasion.

Targeting highly expressed extracellular HSP90 in breast cancer stem cells inhibits tumor growthin vitroandin vivo

“…Taking into account the documented metastatic potential of BCSC 37 this result is in line with previously reported data relating eHSP90 with invasion and metastasis. 24,26,27 These observations suggest that eHSP90 could be considered as a potential CSC marker in the case of breast cancer.…”

“…36 Moreover in the same work we have reported that mAb4C5 disrupts the formation and/or stabilization of the eHSP90/eCdc37/EGFR complex thus leading to inhibition of the invasive capacity of the MDA-MB-231 cells. Taking into account all the above, it is tempting to speculate that eHSP90, by acting as an extracellular chaperone, is crucial not only for the invasive potential of breast cancer cells 24,27 but also for the maintenance of stem cell properties such as self-renewal capacity and tumorigenic ability that are necessary for primary tumor growth. Finally our results further support and reinforce the anti-cancer potential of mAb 4C5.…”

“…In the latter case we demonstrated that mAb4C5 disrupts the association of eHSP90 with the extracellular domain of HER2, which in turn results in inhibition of HER2-HER-3 heterodimer formation, reduced HER-2 phosphorylation and impaired downstream signaling necessary for cytoskeletal re-arrangement, which in turn is essential for cancer cell invasion. 27 Finally we have reported that mAb 4C5 significantly reduces the metastatic depositions of MDA-MB-453 breast cancer cells into the lungs of NOD/ SCID mice by binding to eHSP90. 24 Taking into account all the above, here we investigated the presence of eHSP90 on BCSC derived from the highly metastatic MDA-MB-231, MDA-MB-453 and MCF-7 breast cancer cell lines, and compare it to that on the parental cells.…”

RNAi knockdown of Hop (Hsp70/Hsp90 organising protein) decreases invasion via MMP-2 down regulation

“…Webb et al [34] showed that geldanamycin (GA) down regulates MET expression at nanamolar concentrations, thus inhibiting HGF/SF-mediated cell motility and invasion. Another Hsp90 client protein, HER2 has been proposed to interact extracellularly with Hsp90 -activating HER2 by heterodimerisation with HER3, leading to actin remodelling and cell motility via activation of signal transduction pathways MAPK and PI3 K-Akt [35,36].…”

Secreted Heat Shock Protein 90α Induces Colorectal Cancer Cell Invasion through CD91/LRP-1 and NF-κB-mediated Integrin αV Expression

“…Through an interaction with the extracellular domain of Neu/Her-2, surface HSP90 is involved in heregulin-induced Neu/Her-2 activation and signaling, leading to cytoskeletal rearrangements and migration and invasion of breast cancer cells (7). Recent studies have shown that HSP90 could be secreted by keratinocytes, nonsmall cell lung cancer CL1-5 cells, and breast cancer MCF-7 cells (8 -12).…”