EGF expression decreases MMP-9 promoter activity ex vivo. (A) The C57BL/6/proMMP9-Luc Tg mice were injected intrathymically with 5 × 10³ per lobe of lymphoma cell transfectants (267Egf) or controls (267Srα). At 7 days after injection, thymuses were collected and imaged using the Xenogen IVIS imaging system. Shown are representative images of thymus injected with lymphoma cells. (B) Thymuses were crushed and luciferase activity in tissue extracts was determined and normalized to the protein content. Controls included thymus without tumor cells. Bars represent SD; *P ≤ .05.