LAUSR

Accelerated formation of fibrin clots in a tumor microenvironment can be used for targeted delivery of interferon gamma (IFNγ) to tumor cells. Here, we selected cysteine-arginine-glutamic acid-lysine-alanine (CREKA) as the fibrin clot-binding peptide and designed 2 types of fusion proteins for tumor targeting. The CREKA peptide was fused to IFNγ's C-terminus, with or without a matrix metalloproteinase-2 (MMP2)-cleavable linker (IFNγ-mmp-CREKA or IFNγ-CREKA, respectively). The former was designed to release IFNγ from IFNγ-mmp-CREKA bound to fibrin clots, to ensure IFNγ's function in the tumor milieu. IFNγ-activated sequence-dependent reporter gene expression in B16-BL6 cells revealed that the biological activities of IFNγ-CREKA and IFNγ were comparable, whereas that of IFNγ-mmp-CREKA was approximately 60% that of IFNγ. Plasma concentrations of IFNγ-CREKA and IFNγ-mmp-CREKA remained at effective levels for at least 4 weeks after gene transfer into mice. After gene transfer to tumor-bearing mice, intratumoral concentration of IFNγ in pCpG-IFNγ-mmp-CREKA group was tended to be higher than those of the other groups. Inhibition of colon-26 tumor growth was significantly more with gene transfer of IFNγ-mmp-CREKA than with IFNγ or IFNγ-CREKA. These results indicate that targeted delivery of IFNγ to fibrin clots through IFNγ-mmp-CREKA fusion can enhance the therapeutic efficacy of IFNγ in cancer gene therapy.