Abstract 1062: Imaging DNA damage response (DDR) during oncogenesis.

Abstract

Abstract Introduction: DNA damage repair (DDR) signalling is upregulated during tumorigenesis and acts as a p53-mediated block on proliferation. Expression of the DNA double strand break (DSB) repair protein, γH2AX, is induced by the activated kinases pATM or pATR during oncogenesis. Previously, we showed that γH2AX presents an abundant epitope for non-invasive in vivo imaging of DSBs. We used 111In-labelled anti-γH2AX antibodies, conjugated to the cell penetrating peptide, TAT, to non-invasively image DDR during oncogenesis in a genetically engineered mouse model of HER2/neu-overexpression driven breast cancer. Methods: Balb/neuT mice, genetically modified to express mutated rat neuT under MMTV promotor control, form multiple palpable carcinomas in mammary fat pads when animals are 130 days old. SPECT images were acquired weekly from balb/neuT mice (age 40-140 days; n=23) 24 h after i.v. injection of 111In-labelled anti-γH2AX-Tat or the non-selective agent, 111In-rIgG-Tat using a small animal SPECT/CT scanner. 111In uptake in fat pads was determined using volume of interest analysis. 111In uptake of >5%ID/g was deemed positive. Anatomical and histological changes were assessed at different ages using DCE-MRI imaging and immunohistochemistry. Results: Balb/neuT mice that were 80 days old developed multiple hyperplastic and dysplastic lesions in mammary fat pads. γH2AX foci were observed in these regions in balb/neuT mice that were 80-100 days old (10-15 foci/cell), but were less numerous in overt tumor tissue in 130-day-old mice (4-5 foci/cell). γH2AX foci were not observed in normal tissues in older mice (0 foci/cell), in mammary fat pads in younger mice (0 foci/cell), or in wild type mice (0 foci/cell). Serial SPECT imaging revealed a 7-fold increase in 111In-anti-γH2AX-Tat accumulation in mammary fat pads in mice 80-110 days old (up to 8.5 %ID/g), compared to non-specific control (P=0.0007), but not in younger or older mice (P>0.05). Repeated SPECT imaging itself did not influence tumor occurrence (P>0.05). The median time to detection of positive tissue was 96 days, much sooner than detection of lesions >150 μm by DCE-MRI (117 days), or palpation (130 days) (P<0.0001). Conclusion: Using a γH2AX-targeted radiopharmaceutical, we were able to image the DNA damage response during neuT-mediated oncogenesis in balb/neuT mice. DDR imaging identified neoplastic tissue significantly earlier than anatomical imaging. These results suggest that γH2AX imaging has potential as a screening tool for cancer-prone individuals. Citation Format: Bart Cornelissen, Sarah Able, Veerle Kersemans, Katherine A. Vallis. Imaging DNA damage response (DDR) during oncogenesis. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1062. doi:10.1158/1538-7445.AM2013-1062