Cellular and molecular properties of 90Y-labeled cetuximab in combination with radiotherapy on human tumor cells in vitro


Cellular and molecular properties of 90Y-labeled cetuximab in combination with radiotherapy on human tumor cells in vitro

Saki, M.; Toulany, M.; Sihver, W.; Zenker, M.; Heldt, J.-M.; Mosch, B.; Pietzsch, H.-J.; Baumann, M.; Steinbach, J.; Rodemann, H. P.

Purpose. Anti-EGFR antibody cetuximab (C225) is used in combination with radiotherapy of head and neck squamous cell carcinoma (HNSCC) patients. We investigated whether conjugation of cetuximab with trans-cyclohexyl-diethylene-triamine-pentaacetic acid (CHX-A″-DTPA) and radiolabeling with 90Yttrium affect the molecular and cellular function of cetuximab and improve its combined effect with external-beam irradiation (EBI).Methods. The following cell lines were used: HNSCC UT5, SAS, FaDu, as well as A43, Chinese hamster ovary cells (CHO), and human skin fibroblast HSF7. Binding affinity and kinetics, specificity, retention, and the combination of 90Y-cetuximab with EBI were evaluated.Results. Control cetuximab and CHX-A″-DTPA-cetuximab blocked the proliferation activity of UT5 cells. In combination with EBI, CHX-A″-DTPA-cetuximab increased the radiosensitivity of UT5 to a similar degree as control cetuximab did. In contrast, in SAS and HSF7 cells neither proliferation nor radiosensitivity was affected by either of the antibodies. Binding [90Y]Y-CHX-A″-DTPA-cetuximab (90Y-cetuximab) to EGFR in HNSCC cells occurred time dependently with a maximum binding at 24 h. Retention of 90Y-cetuximab was similar in both HNSCC cell lines; 24 h after treatment, approximately 90% of bound activity remained in the cell layer. Competition assays, using cell membranes in the absence of an internalized fraction of cetuximab, showed that the cetuximab affinity is not lost as a result of conjugation with CHX-A″-DTPA. Cetuximab and CHX-A″-DTPA-cetuximab blocked EGF-induced Y1068 phosphorylation of EGFR. The lack of an effect of cetuximab on EGF-induced Akt and ERK1/2 phosphorylation and the inhibition of irradiation (IR)-induced Akt and ERK1/2 phosphorylation by cetuximab were not affected by DTPA conjugation. 90Y-cetuximab in combination with EBI resulted in a pronounced inhibition of colony formation of HNSCC cells.Conclusions. Conjugation of CHX-A″-DTPA to cetuximab does not alter the cellular and biological function of cetuximab. 90Y-labeling of cetuximab in combination with EBI may improve radiotherapy outcome.

Keywords: Head and neck squamous cell carcinoma; EGFR; Cetuximab; 90Yittrium; 90Y-cetuximab

Permalink: https://www.hzdr.de/publications/Publ-17756
Publ.-Id: 17756