For project 1: Metastases of mice with human breast cancer cell 4t1 were imaged using IVIS optical imaging three weeks post cell injection. Luciferase was used as reporter to visualize the tumors. Luciferase is a gene expressed in tumor cells that interacts with a luciferin substrate that is injected into the mice prior to imaging. This interaction produces the light that is picked up by IVIS. Region of Interest (ROI) values designates the borders of the tumors.