Abstract C129: MicroRNA-155 targets AGTR1/NF-κB /CXCR4 axis and attenuates oncogenesis in glioblastoma
Authors: Singh Anukriti , Srivastava Nidhi , Ateeq Bushra 
Published: March 2020

Abstract
Glioblastoma (GBM) is the most aggressive malignancy of all primary brain tumors. Despite the recent advances in GBM treatment, the average survival time for a patient is less than 15 months. Therefore, we sought to investigate the molecular mechanisms underlying GBM initiation, progression and identify novel drug targets for this deadly disease. Higher levels of Angiotensin II Receptor Type 1 (AGTR1) and Angiotensin II Receptor Type 2 (AGTR2) have been associated with poor patient prognosis in astrocytomas. Additionally, contribution of these receptors in proliferative and infiltrative properties of glioma cells has already been established. Moreover, overexpression of AGTR1 has been known to play a critical role in multiple human malignancies including brain. However, the underlying mechanism involved in AGTR1 upregulation in GBM is not clearly understood and remains a matter of conjecture. Here, we analysed online available RNA-seq data from two independent GBM patients’ cohorts for AGTR1 expression and observed significant overexpression of AGTR1 in glioma patients compared to normal adjacent tissue. Importantly, the overall survival probability of GBM patients with high AGTR1 expression was low as compared to patients with low AGTR1 levels. To understand the post-transcriptional regulation of AGTR1 in GBM, we employed miRNA prediction algorithms namely, TargetScan, miRanda (microRNA.org), MicroT4 (DIANA tools), RNA22 along with experimentally supported database (TarBase), and examined miRNAs that bind to 3’UTR of AGTR1. Interestingly, conserved binding of miRNA-155 was predicted by all algorithms. Further, AGTR1-3’UTR-luciferase reporter assay in HEK-293T cells also confirmed the miRNA-155 mediated post-transcriptional regulation of AGTR1. Moreover, ectopic expression of miRNA-155 in GBM cells abrogate AGTR1-mediated proliferation, invasion, foci formation and anchorage independent growth. Intriguingly, immunodeficient mice implanted with stable miRNA-155 overexpressing SNB19 cells showed a significant reduction (~95%) in tumor burden as compared to the control group. Mechanistically, we showed that miRNA-155 attenuates AGTR1-mediated epithelial-to-mesenchymal transition, angiogenesis, ERK/MAPK signaling and promotes apoptosis. Importantly, stimulation with Angiotensin II (Ang II), a bonafide ligand of AGTR1, results in activation of NF-κB signaling downstream of AGTR1, followed by an increase in expression of C-X-C chemokine receptor type 4 (CXCR4) and AGTR1. Conversely, miRNA-155 overexpression in GBM cells attenuate NF-κB signalling, leading to a notable decrease in the expression of CXCR4 and its downstream signalling accompanied with reduction in AGTR1 levels. Alternately, we treated GBM cells with IKK-16, an inhibitor of IKK complex, to abrogate the NF-κB signalling downstream of AGTR1. Interestingly, we observed a significant reduction in the AGTR1 expression along with a marked decrease in CXCR4 expression. Taken together, we demonstrate that miRNA-155 is involved in post-transcriptional regulation of AGTR1 and disrupts AGTR1/NF-κB /CXCR4 signaling axis via anticancer pleiotropic effects. The present study opens new avenues to use IKK inhibitors and possible use of miRNA-155 replacement therapy for AGTR1-positive malignancies.
Citation Format: Anukriti Singh, Nidhi Srivastava, Bushra Ateeq. MicroRNA-155 targets AGTR1/NF-κB /CXCR4 axis and attenuates oncogenesis in glioblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr C129. doi:10.1158/1535-7163.TARG-19-C129