Recombinant human tissue transglutaminase modifies angiogenesis and delays mammary tumor growth in vivo

Tissue transglutaminase (tTG) is a calcium-dependent enzyme that stabilizes tissues by covalently crosslinking extracellular matrix (ECM) molecules. The tTG expressed by the tumor vasculature and ECM could modify angiogenesis and tumor growth. We investigated whether tTG could play a role in angiogenesis by administering purified recombinant human tTG (40ng/ml) in a rat window chamber model and directly examined the neovascularization process by videomicroscopy. The tTG treated group inhibited vessel growth by 50-70%. We then tested whether the recombinant tTG modified the growth of rat mammary tumor (R3230AC). The tTG (40ng/ml or 120ng/ml) was applied at the time the mammary tumor was implanted into the window chamber. Controls were treated with an inactive tTG mutant (active Cys 277 converted to Ala). Photomicrographs were recorded 3,7 and 10 days after implantation. The tumors either did not grow (25%) or lagged behind controls at day 7 (p<.05). Both concentrations of tTG had similar effects. There was extensive fibrosis and hemorrhage in the tissues of the tTG treated rats. The active site mutant did not modify tumor growth. We observed that after 10 days, the tumor growth in the tTG treated group was similar to controls. In vitro recombinant tTG (40ug/ml) had no effect on endothelial cells growth and tube formation. In conclusion, recombinant tTG has an antiangiogenic activity and can delav tumor growth in vivo bv modifvine the ECM surrounding a developing tumor.

Duke Scholars

Author Mark Wesley Dewhirst Radiation Oncology