Abstract 1645: Characterization of a novel anti-insoluble-fibrin chimeric antibody (AFCA) for cancer stromal target (CAST) therapy and diagnosis.

Abstract Background: A large body of clinicopathological evidence supports the conclusion that abnormal coagulation occurs in a variety of cancers. In the non-malignant condition, fibrin clots (insoluble fibrin) form only at the onset or active state of disease and subsequently disappear because of plasmin digestion or replacement with collagen within a few weeks. However, in cancer, fibrin clot formation and subsequent replacement with collagen continue for as long as cancer cells survive in the body. In this context we considered that the fibrin clot could be a pathophysiologically specific target in cancer and accordingly developed an anti-insoluble-fibrin chimeric antibody (AFCA). Here, we characterize AFCA and demonstrate its potential as a tool for drug delivery to the cancer stroma. Method: The specificity of AFCA was evaluated by ELISA using insoluble fibrin, fibrinogen (the precursor of fibrin), soluble fibrin, and D-dimer (the degradation product of insoluble fibrin) as antigens. To compare AFCA with commercially available anti-fibrin antibodies, we performed ELISA with insoluble fibrin, fibrinogen, and D-dimer as antigens. We also conducted western blotting with native fibrinogen and denatured fibrinogen. To evaluate the accumulation of AFCA in tumors, we gave fluorescence-labeled AFCA to transgenic mice with pancreatic cancer. Results: AFCA recognized only insoluble fibrin, not any fibrin-related proteins. AFCA had higher specificity against insoluble fibrin than did commercially available anti-fibrin antibodies. Western blotting analysis revealed that AFCA reacted with denatured fibrinogen but not native fibrinogen. AFCA, but not isotype control IgG, accumulated in the pancreatic cancer tissues. Conclusion: These findings imply that the epitope of AFCA is a distinctive sequence that is uncovered only on the fibrin clot. Because lasting asymptomatic fibrin clot formation is a cancer-specific phenomenon, AFCA should be a useful tool for drug delivery to insoluble fibrin present around cancers. Citation Format: Yohei Hisada, Masahiro Yasunaga, Yasuhiro Matsumura. Characterization of a novel anti-insoluble-fibrin chimeric antibody (AFCA) for cancer stromal target (CAST) therapy and diagnosis. [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 1645. doi:10.1158/1538-7445.AM2013-1645