Expression of MMP protein in human normal breast and breast cancer tissue analyzed by Western blot. Protein lysates were isolated from normal breast, breast cancer tissue grade 2 (G2) and breast cancer tissue grade 3 (G3). Protein samples were separated by polyacrylamide gel electrophoresis and expression of MMP proteins was visualized using specific antibodies (listed in Table 3). β-actin was used as internal loading control. Inactive (latent) and active forms of MMP proteins are indicated with arrows.