In support of the notion that MMP13 plays a causal role in RKIP-mediated suppression of breast cancer metastasis, expression of MMP13 is sufficient to rescue the invasion inhibited RKIP-expressing 4T1 cells Fig 3B, while the expression of MMP13 alone had no effect on the invasive capacity of the 4T1 cells Fig 3C. This evidence concerns the gene PEBP1 and breast cancer.