Pancreatic adenocarcinoma is a highly aggressive cancer, currently treated with limited success and dismal outcomes. New diagnostic and treatment strategies offer the potential to reduce cancer mortality. Developing highly-specific non-invasive imaging probes for pancreatic cancer is essential to improving diagnostic accuracy and monitoring therapeutic intervention.
A bispecific heterodimer was synthesized by conjugating an anti-tissue factor (TF) Fab with an anti-CD105 Fab, via the bioorthogonal "click" reaction between tetrazine (Tz) and trans-cyclooctene (TCO). The heterodimer was labeled with <sup>64</sup>Cu for positron emission tomography (PET) imaging of nude mice bearing BXPC-3 xenograft and orthotopic pancreatic tumors.
PET imaging of BXPC-3 (TF/CD105<sup>+/+</sup>) xenograft tumors with <sup>64</sup>Cu-labeled heterodimer displayed significantly enhanced tumor uptake (28.8 {plus minus} 3.2 %ID/g; n = 4, SD) at 30 h post-injection (p.i.), as compared to each of their monospecific Fab tracers (12.5 {plus minus} 1.4 and 7.1 {plus minus} 2.6 %ID/g; n = 3, SD). In addition, the activity-concentration ratio allowed for effective tumor visualization (tumor/muscle ratio 75.2 {plus minus} 9.4 at 30 h p.i.; n = 4, SD). Furthermore, <sup>64</sup>Cu-NOTA-heterodimer enabled sensitive detection of orthotopic pancreatic tumor lesions with an uptake of 17.1 {plus minus} 4.9 %ID/g at 30 h p.i. and tumor/muscle ratio of 72.3 {plus minus} 46.7.
This study demonstrates that dual targeting of TF and CD105 provided synergistic improvements in binding affinity and tumor localization of the heterodimer. Dual-targeted imaging agents of pancreatic and other cancers may assists in diagnosing pancreatic malignancies as well as reliable monitoring of therapeutic response.
Copyright ©2016, American Association for Cancer Research (AACR) (Free AACR Whitepaper).
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