Endothelial epsin deficiency decreases tumor growth by enhancing VEGF signaling
Satish Pasula, Xiaofeng Cai, Yunzhou Dong, Mirko Messa, John McManus, Baojun Chang, Xiaolei Liu, Hua Zhu, Robert Silasi Mansat, Seon-Joo Yoon, Scott Hahn, Jacob Keeling, Debra Saunders, Genevieve Ko, John Knight, Gail Newton, Francis Luscinskas, Xiaohong Sun, Rheal Towner, Florea Lupu, Lijun Xia, Ottavio Cremona, Pietro De Camilli, Wang Min, Hong Chen
Satish Pasula, Xiaofeng Cai, Yunzhou Dong, Mirko Messa, John McManus, Baojun Chang, Xiaolei Liu, Hua Zhu, Robert Silasi Mansat, Seon-Joo Yoon, Scott Hahn, Jacob Keeling, Debra Saunders, Genevieve Ko, John Knight, Gail Newton, Francis Luscinskas, Xiaohong Sun, Rheal Towner, Florea Lupu, Lijun Xia, Ottavio Cremona, Pietro De Camilli, Wang Min, Hong Chen
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Research Article

Endothelial epsin deficiency decreases tumor growth by enhancing VEGF signaling

Abstract

Epsins are a family of ubiquitin-binding, endocytic clathrin adaptors. Mice lacking both epsins 1 and 2 (Epn1/2) die at embryonic day 10 and exhibit an abnormal vascular phenotype. To examine the angiogenic role of endothelial epsins, we generated mice with constitutive or inducible deletion of Epn1/2 in vascular endothelium. These mice exhibited no abnormal phenotypes under normal conditions, suggesting that lack of endothelial epsins 1 and 2 did not affect normal blood vessels. In tumors, however, loss of epsins 1 and 2 resulted in disorganized vasculature, significantly increased vascular permeability, and markedly retarded tumor growth. Mechanistically, we show that VEGF promoted binding of epsin to ubiquitinated VEGFR2. Loss of epsins 1 and 2 specifically impaired endocytosis and degradation of VEGFR2, which resulted in excessive VEGF signaling that compromised tumor vascular function by exacerbating nonproductive leaky angiogenesis. This suggests that tumor vasculature requires a balance in VEGF signaling to provide sufficient productive angiogenesis for tumor development and that endothelial epsins 1 and 2 negatively regulate the output of VEGF signaling. Promotion of excessive VEGF signaling within tumors via a block of epsin 1 and 2 function may represent a strategy to prevent normal angiogenesis in cancer patients who are resistant to anti-VEGF therapies.

Authors

Satish Pasula, Xiaofeng Cai, Yunzhou Dong, Mirko Messa, John McManus, Baojun Chang, Xiaolei Liu, Hua Zhu, Robert Silasi Mansat, Seon-Joo Yoon, Scott Hahn, Jacob Keeling, Debra Saunders, Genevieve Ko, John Knight, Gail Newton, Francis Luscinskas, Xiaohong Sun, Rheal Towner, Florea Lupu, Lijun Xia, Ottavio Cremona, Pietro De Camilli, Wang Min, Hong Chen

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Figure 3

VEGF but not other angiogenic signaling is heightened in ECs lacking epsins 1 and 2.

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VEGF but not other angiogenic signaling is heightened in ECs lacking eps...
(A and B) WT or DKO MECs (A) or HUVECs transfected with either control siRNA or epsins 1 and 2 siRNAs (B) were stimulated with VEGF-A (50 ng/ml) and VEGF signaling was analyzed by Western blotting. (C) Quantification of total VEGFR2 and fold change of phospho-VEGFR2 to total VEGFR2 in HUVECs treated with either control or epsin 1 and 2 siRNAs. (D) RT-PCR showing VEGF-A and VEGFR2 expression in WT and DKO MECs. (E–H) VEGF but not FGF, PDGF, EGF, or TGF-β signaling is augmented in the absence of epsins 1 and 2. HUVECs transfected with either control or epsins 1 and 2 siRNAs were stimulated with FGF (25 ng/ml) (E), PDGF (25 ng/ml) (F), EGF (30 ng/ml) (G), or TGF-β (5 ng/ml) (H) and analyzed by Western blotting. (I) VEGF-induced augmented ear vessel permeability revealed by Evans blue dye extravasation. n > 5 per group in all panels.