Effect of c-Jun overexpression on potential of MCF-7 tumor formation. 2 × 107 MCF-7 or MCF-7/c-Jun cells suspended in 200 μl of PBS were injected s.c. in the right flank. After 3–4 weeks, tumor tissues were dissected and fixed in 10% buffered formalin and embedded in paraffin wax. Tissue sections (4 μm) were stained with H & E for morphology. The photographs were taken on a Nikon microscope. A, the tumors are composed of relatively large cells that differ in size and display areas with glandula-like arrangement of tumor cells. B, the blood vessels were visualized in the tumor tissues. C, the tumors were highly invasive in the surrounding muscle tissue. ← blood vessels ×400 magnification.