Human plasminogen kringle 5 protein acts as a potent antiangiogenic and pro-inflammatory agent. Murine DA/3 mammary adenocarcinoma cells (left), gene-engineered green fluorescent protein (GFP)-expressing DA/3 cells (middle), and gene-engineered kringle5-GFP-expressing DA/3 cells (right) were embedded in Matrigel and implanted subcutaneously in immune competent BALB/c mice. Representative images of retrieved implants (arrows) 1 week postimplantation are demonstrated. For details, see Perri et al. in this issue.