Chimeric NANOG repressors inhibit glioblastoma growth in vivo in a context-dependent manner

Abstract

Targeting stemness promises new therapeutic strategies against highly invasive tumors. While a number of approaches are being tested, inhibiting the core transcription regulatory network of cancer stem cells is an attractive yet challenging possibility. Here we have aimed to provide the proof of principle for a strategy, previously used in developmental studies, to directly repress the targets of a salient stemness and pluripotency factor: NANOG. In doing so we expected to inhibit the expression of so far unknown mediators of pro-tumorigenic NANOG function. We chose NANOG since previous work showed the essential requirement for NANOG activity for human glioblastoma (GBM) growth in orthotopic xenografts, and it is apparently absent from many adult human tissues thus likely minimizing unwanted effects on normal cells. NANOG repressor chimeras, which we name NANEPs, bear the DNA-binding specificity of NANOG through its homeodomain (HD), and this is linked to transposable human repressor domains. We show that in vitro and in vivo , NANEP5, our most active NANEP with a HES1 repressor domain, mimics knock-down (kd) of NANOG function in GBM cells. Competition orthotopic xenografts also reveal the effectiveness of NANEP5 in a brain tumor context, as well as the specificity of NANEP activity through the abrogation of its function via the introduction of specific mutations in the HD. The transcriptomes of cells expressing NANEP5 reveal multiple potential mediators of pro-tumorigenic NANEP/NANOG action including intercellular signaling components. The present results encourage further studies on the regulation of context-dependent NANEP abundance and function, and the development of NANEP-based anti-cancer therapies.

NANOG expression in human development and cancerogenesis

“…Other studies investigated synergistic therapeutic effect of targeting NANOG with cancer vaccination or with chemotherapeutic drugs, where an increased sensitivity for drugs and an induced cell apoptosis was observed. 72–75 Information regarding Nanog-targeting therapy in human cancer is limited, i.e. there is an ongoing clinical trial (phase 2) with NANOG inhibitor in combination with sorafenib in adult patients with hepatocellular carcinoma.…”

Anastasis in Glioblastoma, Brain Cancer Stem, and Brain Stem Cells

“…This may suggest that the mechanism of anastasis may suppress stemness properties of GBM cells. NANOG and WNT5A upregulation may lead to a more aggressive phenotype of the cells as independently from the stemness feature (11,12). Moreover, these results also indicated that the cells may become stem-like cells by gaining a self-renewal property (13).…”

Hsp70 and Calcitonin Receptor Protein in Extracellular Vesicles from Glioblastoma Multiforme: Biomarkers with Putative Roles in Carcinogenesis and Potential for Differentiating Tumor Types

“…Because our work is directed toward the identification of biomarkers for the early diagnosis of GBM, we focused on CACLR, considering its cellular functions as a tumor suppressor, which are currently little known, and its ability to interact with various chaperone molecules, including some belonging to the Hsp70 family ( Figure 4 B). Furthermore, our proteomic analysis identified proteins involved in the canonical and alternative complement pathways, in the metabolic pathway, in inflammatory pathways, and more (additional information is presented in Table S3 [ 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 , 93 , 94 , 95 , 96 , 97 , 98 , 99 ]). The differentially expressed proteins were further analyzed using the STRING database to derive an interaction network and potential signaling pathways, which may reveal the tumorigenic mechanism underlying GBM ( Figure 4 B).…”