direct downstream target and activator of p53, and may directly stabilize p21; in addition, PAI-2 expression is increased in senescent fibroblasts and may arrest growth of young fibroplasts. Potential roles in cancer The role of PAI-2 in cancer growth and metastasis is complex, as PAI-2 may have tumor-promoting and tumor-inhibiting effects. Notably, it is high expression of PAI-2 by tumor cells, not the host organism, which influences cancer growth. Cancer cells may facilitate export of PAI-2 via microparticles. PAI-2 provides protection for cancer cells against plasmin-induced cell death, which can exert a lethal effect on tumors. This protection is particularly salient in brain metastases, which tend to express high levels of PAI-2 and neuroserpin, and whose growth may be partially inhibited by knockout of PAI-2. Due to its high expression in tumor cells, PAI-2 has been used to track and study the spread of angiotropic melanoma cells. Although PAI-2 expression can promote metastasis to the brain, in other cases high PAI-2 expression significantly decreases metastasis to the lungs and other organs. The particular effects of PAI-2 on metastasis may depend on cancer type and location in the body. See also Plasminogen activator inhibitor-1 Serpin References Further reading External links The MEROPS online database for peptidases and their inhibitors: I04.007 Fibrinolytic system Serine protease inhibitors