The differential roles of Slit2-exon 15 splicing variants in angiogenesis and HUVEC permeability

Abstract

Slit2, a secreted glycoprotein, is down-regulated in many cancers. Slit2/Robo signaling pathway plays an important, but controversial, role in angiogenesis. We identified splicing variants of Slit2 at exon 15, Slit2-WT and Slit2-ΔE15, with differential effects on proliferation and invasive capability of lung cancer cells. The aim of this study was to elucidate the differential roles of these exon 15 splicing variants in angiogenesis. Our results revealed that both Slit2-WT and Slit2-ΔE15 inhibit motility of human umbilical vein endothelial cells (HUVECs). The conditioned medium (CM) collected from CL1-5/VC or CL1-5/Slit2-WT lung adenocarcinoma cells blocked HUVEC tube formation and angiogenesis on chorioallantoic membrane (CAM) assay when compared with untreated HUVECs and CAM, respectively. However, CM of CL1-5/Slit2-ΔE15 restored the quality of tubes and the size of vessels. Although both Slit2-WT and Slit2-ΔE15 inhibited permeability induced by CM of cancer cells, Slit2-ΔE15 exhibited stronger effect. These results suggested that Slit2-ΔE15 plays important roles in normalization of blood vessels by enhancing tube quality and tightening endothelial cells, while Slit2-WT only enhances tightening of endothelial cells. It appears that Robo4 is responsible for Slit2 isoform-mediated inhibition of permeability, while neither Robo1 nor Robo4 is required for Slit2-ΔE15-enhanced tube quality. The results of this study suggest that Slit2-ΔE15 splicing form is a promising molecule for normalizing blood vessels around a tumor, which, in turn, may increase efficacy of chemotherapy and radiotherapy.

Suppression of Slit3 induces tumor proliferation and chemoresistance in hepatocellular carcinoma through activation of GSK3β/β-catenin pathway

“…While the expression of Slit1 is confined to neurons, Slit2 and Slit 3 are widely expressed in mammalian tissues [ 4 ] and their deregulations have been identified in malignant tissues. Slit2 is frequently inactivated in human cancers including lung cancer [ 5 ], breast cancer [ 6 , 7 ], colorectal cancer [ 8 ], ovarian cancer [ 9 ], glioma [ 10 ] and HCC [ 11 , 12 ] and its tumor suppressive role that inhibits cancer cell invasion and migration [ 10 , 13 – 17 ], angiogenesis [ 18 , 19 ] and growth [ 8 , 20 – 22 ], has been well-studied. In conjunction, hypermethylation and subsequent down-regulation of Slit3 has been reported in several cancers, including thyroid cancer, colorectal cancer, gastric cancer, nasopharyngeal carcinoma, cervical cancer, ovarian cancer and pancreatic ductal adenocarcinoma [ 23 – 32 ].…”

Lung Tumorigenesis Alters the Expression of Slit2-exon15 Splicing Variants in Tumor Microenvironment

“…Slit2-WT suppresses lung cancer cell invasion, while Slit2-ΔE15 inhibits both the growth and invasion of lung cancer cells [21]. We also observed that Slit2-ΔE15, but not Slit2-WT, is able to normalize the vessel size [22]. These studies reveal that the Slit2-exon15 splicing forms have differential roles in tumor growth and angiogenesis.…”

Structural insights and evaluation of the potential impact of missense variants on the interactions of SLIT2 with ROBO1/4 in cancer progression

“…SLIT2 interacts, with its cognate receptor ROBO1 in the human umbilical vein endothelial cells (HUVECs) and tumour-associated endothelial cells 9 . Studies have shown that the ROBO4 receptor imparts inhibitory signal to endothelial migration, tube formation, and vascular permeability through its interaction with SLIT2, suggesting its negative regulatory role in angiogenesis in HUVEC cells 66 – 68 and an animal model for ocular angiogenesis 69 .…”