Abstract LB-009: Intracellular delivery with SOCS3 suppresses angiogenesis in tumors

Abstract

Abstract Introduction: Suppressor of cytokine signaling 3 (SOCS3) is a negative feedback regulator in the Janus kinase/signal transducer and activator of transduction (JAK/STAT) signaling pathway, in which it suppresses inflammation and cancer. The JAK/STAT pathway is activated in some tumors thus enhancing the expression of genes involved in proliferation and angiogenesis, notably, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), angiopoietin-1 and phospoinositide 3-kinase (PI3K)-protein kinase B (AKT). Objective: The aim of this study is to develop an improved cell-permeable (iCP)-SOCS3 and determine its applicability as an anti-angiogenic agent to treat cancer. Methods: The iCP-SOCS3 was expressed in E. coli as a 37 kDa recombinant protein fused to an advanced macromolecule transduction domain (aMTD) and humanized solubilization domain (SD). Uptake of a fluorescently tagged iCP-SOCS3 by cells and tissues was monitored by flow cytometry and confocal microscopy. Biological and biochemical activities of iCP-SOCS3 were determined by in vitro angiogenesis assays and changes in biomarker expression and anti-tumor activities were analyzed in mice bearing human tumor xenografts. Results: The iCP-SOCS3 improved on an earlier generation of CP-SOCS3 fused to FGF4-derived membrane translocating motif (MTM) with regard to solubility, yield, delivery into cells and tissues and biological activity. The iCP-SOCS3 suppressed proliferation of human umbilical vein endothelial cells (HUVECs) by 60% and migration by 54% via inhibition of AKT/mTOR signaling pathway. Moreover, iCP-SOCS3 inhibited invasion of EC cells in PANC-1 and U87MG conditioned medium by 38% and 95%, respectively. In tube formation assay, iCP-SOCS3 reduced the number of branch points by 79% and tube length by 60% compared to the vehicle. In chick chorioallantoic membrane (CAM) assay, iCP-SOCS3 significantly inhibited angiogenesis by 83% in dose dependent manner compared to the reference drug, retinoic acid. The anti-angiogenic activity of iCP-SOCS3 was also shown in matrigel plug assay. The new vessel formation induced by U87-MG glioblastoma cells was significantly reduced by the treatment of iCP-SOCS3. In PANC-1, U87-MG and HepG2 cell-derived xenograft models, iCP-SOCS3 suppressed expression of pro-angiogenic factors including VEGF, ERK and angiopoietin 1. Conclusion: These results validate iCP-SOCS3 targets in promoting angiogenesis and suggest ways to reduce angiogenesis in various types of tumors. Citation Format: Yukdong Jung, Kuysook Lee, Youngsil Choi, Daewoong Jo. Intracellular delivery with SOCS3 suppresses angiogenesis in tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-009.