Stemness, Pluripotentiality, and Wnt Antagonism: sFRP4, a Wnt antagonist Mediates Pluripotency and Stemness in Glioblastoma

Abstract

Background: Chemotherapeutic resistance of glioblastoma has been attributed to a self-renewing subpopulation, the glioma stem cells (GSCs), which is known to be maintained by the Wnt β−catenin pathway. Our previous findings demonstrated that exogeneous addition of the Wnt antagonist, secreted fizzled-related protein 4 (sFRP4) hampered stem cell properties in GSCs. Methods: To understand the molecular mechanism of sFRP4, we overexpressed sFRP4 (sFRP4 OE) in three human glioblastoma cell lines U87MG, U138MG, and U373MG. We also performed chromatin immunoprecipitation (ChIP) sequencing of sFRP4 OE and RNA sequencing of sFRP4 OE and sFRP4 knocked down U87 cells. Results: We observed nuclear localization of sFRP4, suggesting an unknown nuclear role. ChIP-sequencing of sFRP4 pulldown DNA revealed a homeobox Cphx1, related to the senescence regulator ETS proto-oncogene 2 (ETS2). Furthermore, miRNA885, a p53-mediated apoptosis inducer, was upregulated in sFRP4 OE cells. RNA sequencing analysis suggested that sFRP4-mediated apoptosis is via the Fas-p53 pathway by activating the Wnt calcium and reactive oxygen species pathways. Interestingly, sFRP4 OE cells had decreased stemness, but when knocked down in multipotent mesenchymal stem cells, pluripotentiality was induced and the Wnt β-catenin pathway was upregulated. Conclusions: This study unveils a novel nuclear role for sFRP4 to promote apoptosis by a possible activation of DNA damage machinery in glioblastoma.

Therapeutic Emergence of Rhein as a Potential Anticancer Drug: A Review of Its Molecular Targets and Anticancer Properties

“…Cyclin D1, one of the major cell-cycle mediator proteins, is overexpressed in the cancer cells due to the increased β-catenin levels. Thus, there is a crucial role of β-catenin, a component of the Wnt signaling pathway, in activating the genes for growth regulation involving cellular survival, proliferation and metastasis [105][106][107][108][109]. It was shown that rhein induced cell-cycle arrest at the G0/G1 and S phases in A549 lung cancer cells and BEL-7402 hepatocellular cancer cells, respectively [54,110].…”

Role of microRNA/Epithelial-to-Mesenchymal Transition Axis in the Metastasis of Bladder Cancer

“…The Wnt/β-catenin signaling pathway has been under attention in recent years due to its role in tumorigenesis [ 115 , 116 , 117 , 118 , 119 ]. The tumor-promoting role of Wnt signaling pathway has been investigated in different cancers, including BC [ 120 , 121 ].…”

Multifaceted WNT Signaling at the Crossroads Between Epithelial-Mesenchymal Transition and Autophagy in Glioblastoma

“…Demethylation of the FRP gene promoter in human glioma cell lines led to an increase in phosphorylated b-catenin in the cytosol, attenuating tumorigenesis (48). Expression of FRPs promotes apoptosis through a possible activation of the DNA damage machinery through FAS-p53, activating the non-canonical WNT/Ca 2+ pathway and the release of reactive oxygen species (ROS) (49). FRP4 treatment, in conjunction with TMZ, inhibited the canonical WNT pathway and was associated with a decrease in the expression of mesenchymal markers such as N-cadherin, Twist and Snail, along with a greater expression of epithelial markers, such as E-cadherin, showing the role of the inhibitor in reversing EMT (49).…”

“…Expression of FRPs promotes apoptosis through a possible activation of the DNA damage machinery through FAS-p53, activating the non-canonical WNT/Ca 2+ pathway and the release of reactive oxygen species (ROS) (49). FRP4 treatment, in conjunction with TMZ, inhibited the canonical WNT pathway and was associated with a decrease in the expression of mesenchymal markers such as N-cadherin, Twist and Snail, along with a greater expression of epithelial markers, such as E-cadherin, showing the role of the inhibitor in reversing EMT (49). In addition, FRP4 chemically sensitizes GSCs, which decreases stemness properties that contribute to therapeutic resistance (49).…”