Pigment Epithelium-derived Factor and Its Phosphomimetic Mutant Induce JNK-dependent Apoptosis and p38-mediated Migration Arrest

Alexander Konson,Sunila Pradeep,Cosimo Walter D'Acunto,Rony Seger

doi:10.1074/jbc.m110.151548

Abstract

Pigment epithelium-derived factor (PEDF) is a potent endogenous inhibitor of angiogenesis and a promising anticancer agent. We have previously shown that PEDF can be phosphorylated and that distinct phosphorylations differentially regulate its physiological functions. We also demonstrated that triple phosphomimetic mutant (EEE-PEDF), has significantly increased antiangiogenic activity and is much more efficient than WT-PEDF in inhibiting neovascularization and tumor growth. The enhanced antiangiogenic effect was associated with a direct ability to facilitate apoptosis of tumor-residing endothelial cells (ECs), and subsequently, disruption of intratumoral vascularization. In the present report, we elucidated the molecular mechanism by which EEE-PEDF exerts more profound effects at the cellular level. We found that EEE-PEDF suppresses EC proliferation due to caspase-3-dependent apoptosis and also inhibits migration of the EC much better than WT-PEDF. Although WT-PEDF and EEE-PEDF did not affect proliferation and did not induce apoptosis of cancer cells, these agents efficiently inhibited cancer cell motility, with EEE-PEDF showing a stronger effect. The stronger activity of EEE-PEDF was correlated with a better binding to laminin receptors. Furthermore, the proapoptotic and antimigratory activities of WT-PEDF and EEE-PEDF were found regulated by differential activation of two distinct MAPK pathways, namely JNK and p38, respectively. We show that JNK and p38 phosphorylation is much higher in cells treated with EEE-PEDF. JNK leads to apoptosis of ECs, whereas p38 leads to anti-migratory effect in both EC and cancer cells. These results reveal the molecular signaling mechanism by which the phosphorylated PEDF exerts its stronger antiangiogenic, antitumor activities.

Highlights

EEE-Pigment epithelium-derived factor (PEDF) was correlated with a better bindifnigntdoinlagmsiniinn sreu-bsequPerenvtiowusostrukd.ies by our group revealed that plasma PEDF is ceptors
As compared with WT-PEDF, EEEPEDF induces much stronger signaling via p38 and JNK, and we propose that this stronger signaling effect is the reason for the enhanced antiangiogenic activity of this PEDF mutant
Effect of WT-PEDF and EEE-PEDF on Endothelial and Cancer Cell Proliferation—We have previously shown that when administered to mice bearing MDA-MB-231, HCT116, or U87-MG xenografts, WT-PEDF and its phosphomimetic mutant EEE-PEDF predominantly affect ECs of the tumor vasculature, rather than cancer cells themselves [19]

Summary

Introduction

EEE-PEDF was correlated with a better bindifnigntdoinlagmsiniinn sreu-bsequPerenvtiowusostrukd.ies by our group revealed that plasma PEDF is ceptors. JNK leads to these phosphorylations by demonstrating that variable phosapoptosis of ECs, whereas p38 leads to anti-migratory effect in phorylation states of PEDF differentially regulate its biological both EC and cancer cells. These results reveal the molecular sig- mode of activity [18]. The proapoptotic and antimigratory activities of WT-PEDF and EEE-PEDF are further shown to be differentially and independently regulated by JNK and p38 MAPKs. As compared with WT-PEDF, EEEPEDF induces much stronger signaling via p38 and JNK, and we propose that this stronger signaling effect is the reason for the enhanced antiangiogenic activity of this PEDF mutant

Objectives

Results

Conclusion