Evaluation of DNA damage in a Her2+ cell line induced by an Auger- emitting immunoconjugate

Introduction: Auger electron based radioimmunotherapy (RIT) using 111In-DOTA-trastuzumab (111In-DOTA-antiHer2) feasibility was studied in vitro on a HER2/neu positive cell line, SkBr3. Methods: 111In-DOTA-antiHer2 was prepared according to the optimized conditions followed by quality control tests including radiochemical purity; immunoreactivity). SkBr3 as a HER2/neu positive cell line was used to determine the degree of internalization and cell viability of 111In-DOTA-antiHer2. For comet assay freshly cultivated SkBr3 cells incubated with 111InDOTA-antiHer2 in 3.7 and 7.4 MBq doses at 37oC for 24h. Results: 111In-DOTA-antiHer2 (>95% radiochemical purity; >79% immunoreactivity) demonstrated significant internalization in SKBr3 cells in 24 h. no significant cell viability difference observed for 111In-DOTA-antiHer2 and 111In cation treatments. Comet assay at 3.7 MBq demonstrated no significant DNA damage, while at 7.4 MBq dose DNA damage observed at least 16% more than control In-111 chloride after 24 h. Conclusion: Although the internalization of 111In-DOTA-antiHer2 was approved in this study, however, lack of cell death and slight DNA breakage for 111In-DOTA-antiHer2 treatment suggests absence of nucleus entry which is essential for demonstration of DNA damage according to Auger electron range at cellular level.