Elimination of Osteosarcoma by Necroptosis with Graphene Oxide-Associated Anti-HER2 Antibodies

Abstract

The prognosis for non-resectable or recurrent osteosarcoma (OS) remains poor. The finding that the majority of OS overexpress the protooncogene HER2 raises the possibility of using HER2 as a therapeutic target. However, clinical trials on the anti-HER2 antibody trastuzumab (TRA) in treating OS find no therapeutic benefit. HER2 overexpression in OS is not generally associated with gene amplification, with low-level expression regarded as HER2 "negative", as per criteria used to classify breast cancer HER2 status. Nevertheless, active HER2-targeting approaches, such as virus-based HER2 vaccines or CAR-T cells have generated promising results. More recently, it has been found that the noncovalent association of TRA with nanomaterial graphene oxide (GO) generates stable TRA/GO complexes capable of rapidly killing OS cells. TRA/GO induces oxidative stress and strong HER2 signaling to elicit immediate degradation of both cIAP (cellular inhibitor of apoptosis protein) and caspase 8, leading to activation of necroptosis. This is an attractive mechanism of cancer cell death as chemo/apoptosis-resistant tumors may remain susceptible to necroptosis. In addition, necroptosis is potentially immunogenic to promote tumor immunity, as opposed to apoptosis that tends to silence tumor immunity. Currently, no established anticancer therapeutics are known to eliminate cancers by necroptosis. The aim of this article is to review the rationale and mechanisms of TRA/GO-mediated cytotoxicity.

Keywords: HER2; graphene oxide; necroptosis; osteosarcoma; trastuzumab.

Figure 1

The HER2 signaling pathway.

Figure 2

Mechanism of TRA/GO action. (A) TRA/GO induces ROS production. ROS disrupts mitochondrial integrity, releasing SMAC/DIBLO into cytosol. Binding of SAMC to cIAPs prevent RIP1 ubiquitylation, allowing formation of death complex ripoptosome. (B) Binding of TRA/GO to HER2 causes HER2 homodimerization, eliciting HER2 signaling; this activates NF-kB through the canonic pathway, augmenting TNFα production. TNFα singling through TNFR1 promotes degradation of cIAPs. (C) HER2 signaling also activates MAPK pathway, resulting in activation RSK2 that phosphorylate caspase 8 at Thr263 site to induce caspase ubiquitination and proteosomal degradation. Degradation of caspase 8 leads to formation of necroptosome executing necroptosis. (D) ROS also contributes to MAPK activation.