Abstract 1863: Correlations of genetic variation R521K of EGF receptor and the in vitro, in vivo and clinical phenotypes of head and neck cancers after cetuximab treatment

Squamous cell carcinomas of the Head and Neck region (HNSCCs) have about 600.000 new cases every year. Advanced disease is treated by radio-chemotherapy, which has ambiguous success. Cetuximab, a monoclonal antibody against EGF receptor, is proven to be useful in combination therapy, thus it is in clinical use in HNSCC. However, a large number of patients show therapy resistance and do not benefit from combined therapy. EGF receptor is a widely used target in the therapy against cancer cells. Antibodies (as cetuximab) and inhibitors (TKI) are in use. However, genetic variations of the receptor are described to influence therapy efficacy. The extracellular missense polymorphism R521K of the receptor is reported to be abundant in HNSCC. However, its role in therapy outcome is yet to be cleared. In the present work, we mapped the possible effects of cetuximab therapy in wild type and mutant genotype HNSCCs. We selected two wild type (Pe/Ca-PJ41, Cal27) and two R521K (Pe/Ca-PJ15, FaDu) cell lines, performed in vitro proliferation tests and antibody binding assays, measured in vitro Antigen-Dependent Cellular Cytotoxicity (ADCC), and quantified receptor phosphorylation inhibition by cetuximb. In our in vivo xenograft experiments, we analyzed subcutaneous tumor growth by cetuximab, in combination with inhibition of NK cell and macrophage activity. Importantly, we analyzed clinical samples in the National Institute of Oncology, originated from 95 relapsed HNSCC patients treated with cetuximab to reveal any connections between EGFR R521K single nucleotide polymorphism and clinical outcome. In cell lines, cetuximab did not show significant cytotoxic effects, but was effective in the ADCC assay. Significantly, it enhanced the killing of cancer cells more effectively in wild type cell line models than on R521K harboring cells. Although antibody binding assay and EGF receptor phosphorylation was not different among the cell lines used, in vivo xenograft models showed strong antitumor effect of cetuximab in wild type models, and only moderate or no response in EGFR R521K models. Our clinical study, showed significantly lower progression-free survival among patients with R521K tumors. Overall survival of the two genotype groups showed only a trend of similar pattern, without statistically significant difference. Immune cell quantification showed no difference between the NK cell and macrophage infiltration in the two groups. Our data suggests the possible effect of EGFR 521 genotype on cetuximab therapy efficacy, but per se is insufficient to explain the dramatic difference between patient responses. Further data collection and analysis might be needed to reassure if R521K should play role in therapy selection for HNSCC, while clinical samples collected after cetuximab treatment would be exceptionally useful in order to track immune cell changes in patients with wild type and EGFR R521K tumors. This work was funded by the National Research, Development and Innovation Office grant K/116295 (2015). Financial support from the 2019 Thematic Excellence Program (TUDFO/51757/2019-ITM) is greatly acknowledged.

Citation Format: Mihaly T. Cserepes, Zita Hegedus, Ivan Ranđelović, Istvan Kenessey, Mónika Meilinger-Dobra, Kristóf G. Csikó, Andrea Ladanyi, Éva Remenár, Jozsef Tovari. Correlations of genetic variation R521K of EGF receptor and the in vitro, in vivo and clinical phenotypes of head and neck cancers after cetuximab treatment [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1863.