Downregulation of Pygopus 2 inhibits vascular mimicry in glioma U251 cells by suppressing the canonical Wnt signaling pathway

Abstract

Abstract. Gliomas are the most common type of malignant primary brain tumor, and the Wnt signaling pathway is associated with glioma malignancy. Pygopus protein plays an important role in developmental brain patterning, and has been identified to be a component of the Wnt signaling pathway. In the present study, the Pygopus 2 (Pygo2) protein was examined in 80 glioma tissue samples. Short hairpin (sh) RNA-Pygo2 was transfected into glioma U251 cells, and the cell proliferation, colony formation and bromodeoxyuridine (BrdU) incorporation were analyzed. Western blot analysis and reverse transcription-polymerase chain reaction were used to detect the expression of Pygo2. A vascular mimicry assay was performed to examine the vascular mimicry of U251 cells. A luciferase reporter assay was used to detect the β-catenin/Wnt system. The cyclin D1 protein was also detected using western blot analysis. The results demonstrated that inhibition of the expression of Pygo2 significantly triggered the decrease of cell proliferation, colony formation and BrdU incorporation compared with the cells treated with scramble control shRNA (shRNA-Scr). shRNA-Pygo2 transfection was found to inhibit vascular-mimicry and block the Wnt signaling pathway compared to the cells transfected with shRNA-Scr. The transfection of shRNA-Pygo2 also decreased the expression of the Wnt target gene cyclin D1. In conclusion, shRNA-Pygo2 suppressed glioma cell proliferation effectively and inhibited vascular mimicry by inhibiting the expression of cyclin D1 in the canonical Wnt/β-catenin pathway in brain glioma cells.

Wnt/β-catenin signaling pathway inhibits the proliferation and apoptosis of U87 glioma cells via different mechanisms

“…Similar to our finding, Nowicki et al [26] reported that inhibiting GSK-3 through lithium could reduce the motility of gliomas. Another study reported that inhibiting the expression of Pygo2 could decrease the proliferation, colony formation, and BrdU incorporation of gliomas by reducing cyclin D1, a downstream gene of the Wnt/β-catenin signaling pathway [27]. The conclusion was analogous to the findings by Zhang.…”

Mechanisms of Vasculogenic Mimicry in Ovarian Cancer

“…Several mechanisms are involved in VM, including those related to the capacity of aggressive tumor cells to resemble features of the ECs such as cell adhesion (52), migration (53), extracellular matrix remodeling (54), perfusion (50), and maturation of blood vessels (55). Moreover, CSCs promote VM by deregulating pathways involved in embryonic development, such as the transforming growth factor β (TGF-β) (56–58), Wnt (59), Notch (60, 61), Nodal (62–64), and the Hippo pathways (65–67), among others. EMT also plays an important role in VM, and encompasses the pathways previously mentioned as well as transcription factors such as Twist1/2 (68), Snail/Slug (69), and ZEB1/2 (34).…”

“…The Wnt family members regulate EC differentiation and vascular development (112) and has been associated with VM. In glioma and colon cancer, the canonical Wnt/β-catenin pathway induced VM by increasing the expression of VEGFR-2 and VE-cadherin (59, 113). Interestingly, in ovarian cancer, the non-canonical Wnt signaling is implicated in VM formation.…”

Immunohistochemistry analysis of Pygo2 expression in central nervous system tumors

“…Previous research has demonstrated that the deletion of Pygo2 delayed tumor onset in Wnt‐1 transgenic mice that spontaneously developed extensive mammary adenocarcinomas (Watanabe et al 2014). Suppression of Pygo2 expression inhibited ovarian, lung cancer cell and glioma cells proliferation (Liu et al 2013b; Wang et al 2016). The Pygo2 oncogenic potential was also evaluated by xenograft assays in immunodeficient mice both for wild and knockdown Pygo2 epithelial ovarian cancer cells.…”