MMP-2/9-oriented combinations enhance antitumor efficacy of EGFR/HER2-targeting fusion proteins and gemcitabine

To increase the antitumor efficacy, in the present study, we proposed several settings of matrix metalloproteinase (MMP)-2/9-oriented combinations that comprise the MMP-2/9-targeting fusion protein dFv-LDP and the MMP inhibitor doxycycline (DOX) in association with EGFR/HER2-bispecific fusion protein Ec-LDP-Hr, its enediyne-energized analogue Ec-LDP-Hr-AE, and gemcitabine (GEM). The expressions of various fusion proteins were detected by western blot analysis. Proliferation and migration inhibition of cells were determined by MTT and Transwell assay, respectively. The binding capability of dFv-LDP and Ec-LDP-Hr to cancer cells was examined by ELISA, cell immunofluorescence coimmunoprecipitation and confocal assays. Animal experiments were set to investigate the antitumor efficacy of various combinations against colorectal carcinoma HCT-15 xenograft in athymic mice. These two targeting proteins dFv-LDP and Ec-LDP-Hr had strong binding capabilities and antiproliferation effects on various cancer cell lines. Enhanced therapeutic efficacy in vivo was observed in the MMP-2/9-targeting fusion protein dFv-LDP integrated combinations including: i) dFv-LDP and Ec-LDP-Hr, ii) dFv-LDP and enediyne-energized fusion protein Ec-LDP-Hr-AE, iii) dFv-LDP and Ec-LDP-Hr-AE plus DOX, and iv) dFv-LDP and GEM plus DOX against colorectal cancer HCT-15 xenograft in athymic mice. In setting iii, DOX (20 mg/kg), dFv-LDP (20 mg/kg) and Ec-LDP-Hr-AE (0.3 mg/kg) alone suppressed tumor growth by 35, 49.7 and 67.5%, respectively. The combination of dFv-LDP and Ec-LDP-Hr-AE was 75.1%. Furthermore, this combination plus DOX showed stronger efficacy with an inhibitory rate of 82.7%. In setting iv, the combination of dFv-LDP and GEM suppressed tumor growth by 66.3%. Notably, the tumor inhibitory rate of the dFv-LDP/GEM/DOX combination reached 85.5%, producing initial shrinkage after the first administration. The MMP-2/9-oriented combination strategy that employs the MMP-2/9-targeting antibody-based fusion protein and the small molecular inhibitor DOX as the basic composed agents may enhance antitumor efficacy in association with the EGFR/HER2-targeting fusion protein and GEM. This multiple targeting approach may be useful for enhancing antitumor efficacy against colorectal cancer.