Targeting prion-like protein doppel selectively suppresses tumor angiogenesis
Taslim A. Al-Hilal, … , In-San Kim, Youngro Byun
Taslim A. Al-Hilal, … , In-San Kim, Youngro Byun
Published March 7, 2016
Citation Information: J Clin Invest. 2016;126(4):1251-1266. https://doi.org/10.1172/JCI83427.
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Research Article Oncology

Targeting prion-like protein doppel selectively suppresses tumor angiogenesis

Abstract

Controlled and site-specific regulation of growth factor signaling remains a major challenge for current antiangiogenic therapies, as these antiangiogenic agents target normal vasculature as well tumor vasculature. In this article, we identified the prion-like protein doppel as a potential therapeutic target for tumor angiogenesis. We investigated the interactions between doppel and VEGFR2 and evaluated whether blocking the doppel/VEGFR2 axis suppresses the process of angiogenesis. We discovered that tumor endothelial cells (TECs), but not normal ECs, express doppel; tumors from patients and mouse xenografts expressed doppel in their vasculatures. Induced doppel overexpression in ECs enhanced vascularization, whereas doppel constitutively colocalized and complexed with VEGFR2 in TECs. Doppel inhibition depleted VEGFR2 from the cell membrane, subsequently inducing the internalization and degradation of VEGFR2 and thereby attenuating VEGFR2 signaling. We also synthesized an orally active glycosaminoglycan (LHbisD4) that specifically binds with doppel. We determined that LHbisD4 concentrates over the tumor site and that genetic loss of doppel in TECs decreases LHbisD4 binding and targeting both in vitro and in vivo. Moreover, LHbisD4 eliminated VEGFR2 from the cell membrane, prevented VEGF binding in TECs, and suppressed tumor growth. Together, our results demonstrate that blocking doppel can control VEGF signaling in TECs and selectively inhibit tumor angiogenesis.

Authors

Taslim A. Al-Hilal, Seung Woo Chung, Jeong Uk Choi, Farzana Alam, Jooho Park, Seong Who Kim, Sang Yoon Kim, Fakhrul Ahsan, In-San Kim, Youngro Byun

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Figure 10

Therapeutic efficacy of LHbisD4.

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Therapeutic efficacy of LHbisD4. (A) Orally administered LHbisD4, at a d...
(A) Orally administered LHbisD4, at a dose of 10 mg/kg daily, inhibited SCC7 tumor growth (n = 11–12 mice). **P < 0.01 versus control, Student’s t test. (B) Images of isolated tumors after termination of the experiment. Scale bar: 1 mm. (C) Tumors were excised after the study to calculate the final tumor weight. ***P < 0.001 versus control. (D and E) Representative images of SCC7 tumor–bearing mouse tumor sections stained for PCNA (proliferating cells) and CD31 (blood vessels) and their staining score (n = 11 mice). Scale bars: 50 μm. *P < 0.05 versus control; ***P < 0.001 versus control, Student’s t test. (F) Total volume of isolated TECs after termination of the experiment (n = 11 tumor sections). *P < 0.01 versus control, Student’s t test. (G) Tumor growth inhibition study of orally administered LHbisD4 in MDAMB-231 tumor at doses of 2.5, 5, and 10 mg/kg once daily or 5 and 10 mg/kg twice daily (n = 5–7 mice). ***P < 0.001 between each of the groups and the control group. **P < 0.01 between the 10 mg/kg once daily and the 10 mg/kg twice daily groups, Mann-Whitney U test. (H) Tumors were excised at the end of the study to calculate the final tumor weight. *P < 0.05, Mann-Whitney U test. (I) Tumor sections from MDAMB-231 tumor–bearing mice were stained for CD31 (blood vessels) after LHbisD4 treatment at different doses (n = 5–7 mice). Scale bar: 50 μm. (J) Dual staining of doppel (green) and PCNA (red) in a section of control and LHbisD4-treated samples. Scale bar: 50 μm.