Abstract 63: Targeting osteosarcoma with graphene oxide-associated anti-HER2 antibodies
Authors: Chen Xinjian 
Published: July 2017

Abstract
Osteosarcoma (OS) is the most common primary cancer of the bone affecting children and adolescents. While over the last two decades the neoadjuvant chemotherapy has improved survival of the patients with resectable OS, the prognosis for unresectable or recurrent tumors remains poor due to the lack of effective treatment. Given that a majority osteosarcomas overexpress HER2, a phase II clinical trial of anti-HER2 antibody trastuzumab in conjunction with chemotherapy has been carried out to treat metastatic OS. However, no significant therapeutic benefit was observed. We recently reported that association of anti-CD20 antibody rituximab with a nanomaterial graphene oxide (GO) substantially enhances the anti-lymphoma activity of the antibody. Here we have studied antitumor activity of GO-associated trastuzumab (TRA). Similar to RTX, TRA could be stably associated with functionalized GO through non-covalent interactions, and GO-associated TRA (TRA/GO) showed markedly enhanced HER2 binding activity with capacity to aggregate (cap) HER2 on the target cells. Treating HER2+ OS as well as Ewing’s sarcoma cell lines in culture with TRA/GO resulted in rapid sarcoma cell death within 12 hr, while free TRA or the cytotoxin-conjugated TRA (ado-trastuzumab emtansine) showed no significant cytotoxic effects. TRA/GO manifested no cytotoxicity to human lymphocytes, in contrast to chemotherapeutic drugs such as doxorubicin and oxaliplatin. We find that the ability to kill the sarcoma cells results from the unique capacity of TRA/GO to simultaneously induce oxidative stress as well as intense detrimental HER2 signaling, which leads to a complete disappearance of a major tyrosine-phosphorylated protein and caspase 8, and a partial loss of RIPK1 along with an increase in RIPK3 levels within 5 min, followed by necroptosis of the target cells. Intravenous administration of TRA/GO rapidly eradicated established xenograft human OS in the lung as well as at subcutaneous locations in NOD/ragko/gko immunodeficient mice in the absence of chemotherapy, resulting in indefinite survival of the animals. In contrast, free TRA treatment failed to do so. No appreciable side effects were observed of TRA/GO in vivo. These results therefore demonstrate a novel strategy to substantially enhance the therapeutic capacity of anti-cancer antibodies. Given the increasing variety of human malignancies that are found to overexpress Her2, including sarcomas, carcinomas and neurological malignancies, our findings should have broad therapeutic implications. As TRA/GO does not harm lymphocytes, TRA/GO-based therapy may constitute a unique opportunity to implement immunotherapy that is now known to play an important role in control tumor progression.
Citation Format: Xinjian Chen. Targeting osteosarcoma with graphene oxide-associated anti-HER2 antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 63. doi:10.1158/1538-7445.AM2017-63