Amplification of DNA damage by a ¦ÃH2AX-targeted radiopharmaceutical

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• 作者：Bart Cornelissen ; Sonali Darbar ; Veerle Kersemans ; Danny Allen ; Nadia Falzone ; Jody Barbeau ; Sean Smart ; Katherine A. Vallis
• 关键词：Radioimmunoconjugate ; ¦ÃH2AX ; Auger electrons ; DNA damage ; Ionizing radiation
• 刊名：Nuclear Medicine and Biology
• 出版年：2012
• 出版时间：November, 2012
• 年：2012
• 卷：39
• 期：8
• 页码：1142-1151
• 全文大小：458 K

文摘

¹¹¹In-DTPA-anti-¦ÃH2AX-Tat, which combines an anti-¦ÃH2AX antibody with a cell-penetrating peptide, Tat, and the Auger electron-emitting radioisotope, ¹¹¹In, targets the DNA damage signalling protein, ¦ÃH2AX, and has potential as a probe for imaging DNA damage in vivo. The goal of this study was to investigate whether ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat labelled to high specific activity (6 MBq/¦Ìg) can amplify treatment-related DNA damage for therapeutic gain.

Methods

MDA-MB-468 and MDA-MB-231/H2N (231-H2N) breast cancer cells were incubated with ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat (3 MBq, 6 MBq/¦Ìg) or a control radioimmunoconjugate, ¹¹¹In-DTPA-mIgG-Tat, and exposed to IR or bleomycin. DNA damage was studied by counting ¦ÃH2AX foci and by neutral comet assay. Cytotoxicity was evaluated using clonogenic assays. ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat was administered intravenously to 231-H2N-xenograft-bearing Balb/c nu/nu mice in tumor growth inhibition studies.

Results

The number of ¦ÃH2AX foci was greater after exposure of cells to IR (10 Gy) plus ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat compared to IR alone (20.6 ¡À 2.5 versus 10.4 ¡À 2.3 foci/cell; P < .001).¹¹¹In-DTPA-anti-¦ÃH2AX-Tat resulted in a reduced surviving fraction in cells co-treated with IR (4 Gy) versus IR alone (5.2 %  ¡À 0.9 % versus 47.8 %  ¡À 2.8 % ; P < .001). Similarly, bleomycin (25-200 ¦Ìg/mL) plus ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat resulted in a lower SF compared to bleomycin alone. The combination of a single exposure to IR (10 Gy) plus ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat significantly decreased the growth rate of 231-H2N xenografts in vivo compared to either ¹¹¹In-DTPA-anti-¦ÃH2AX-Tat or IR alone (? 0.002 ¡À 0.004 versus 0.036 ¡À 0.011 and 0.031 ¡À 0.014 mm³/day, respectively, P < .001).

Conclusion

¹¹¹In-DTPA-anti-¦ÃH2AX-Tat amplifies anticancer treatment-related DNA damage in vitro and has a potent anti-tumor effect when combined with IR in vivo.