IRE1\u03b1 and IGF signaling predict resistance to an endoplasmic reticulum stress-inducing drug in glioblastoma cells

Jeffrey J Rodvold,Hannah Carter,Su Xian,Julia Nussbacher,T Cameron Waller,Pengfei Jiang,Maurizio Zanetti,Brian Tsui,Stephen C Searles,Ivan Babic,Natsuko Nomura,Alyssa Lew,Santosh Kesari,Jonathan H Lin

doi:10.1038/s41598-020-65320-6

Abstract

To date current therapies of glioblastoma multiforme (GBM) are largely ineffective. The induction of apoptosis by an unresolvable unfolded protein response (UPR) represents a potential new therapeutic strategy. Here we tested 12ADT, a sarcoendoplasmic reticulum Ca2+ ATPase (SERCA) inhibitor, on a panel of unselected patient-derived neurosphere-forming cells and found that GBM cells can be distinguished into “responder” and “non-responder”. By RNASeq analysis we found that the non-responder phenotype is significantly linked with the expression of UPR genes, and in particular ERN1 (IRE1) and ATF4. We also identified two additional genes selectively overexpressed among non-responders, IGFBP3 and IGFBP5. CRISPR-mediated deletion of the ERN1, IGFBP3, IGFBP5 signature genes in the U251 human GBM cell line increased responsiveness to 12ADT. Remarkably, >65% of GBM cases in The Cancer Genome Atlas express the non-responder (ERN1, IGFBP3, IGFBP5) gene signature. Thus, elevated levels of IRE1α and IGFBPs predict a poor response to drugs inducing unresolvable UPR and possibly other forms of chemotherapy helping in a better stratification GBM patients.

Highlights

Glioblastoma (GBM) is a devastating, rapidly fatal disease whose survival rate has not improved much in recent years relative to other tissues
Mipsagargin (G-202) is a prodrug that is hydrolyzed by prostate specific membrane antigen (PSMA), which is highly expressed in the stroma of 75% of brain tumors[19] relative to normal brain tissue
Because neither inhibition of the IRE1α or PKR-like ER kinase (PERK) pathways accounted for a differential sensitivity in NR neurosphere lines, we looked beyond unfolded protein response (UPR) associated genes and performed a weighted gene correlation network analysis (WGCNA) to identify putative gene signaling networks and assess their roles in 12ADT responsiveness[23]

Summary

Introduction

Glioblastoma (GBM) is a devastating, rapidly fatal disease whose survival rate has not improved much in recent years relative to other tissues. With the current standard of care for newly diagnosed GBM of surgical resection followed by temozolomide and radiotherapy, the expected median survival remains under two years[1] This inadequacy leaves open the necessity for novel therapeutic approaches targeting the signaling programs GBM cells rely on to acquire chemoresistance and survive in the face of various challenges in the tumor microenvironment, e.g., hypoxia, radiation therapy, and chemotherapy (temozolomide). In mammalian cells the unfolded protein response (UPR) represents a powerful homeostatic signaling mechanism and an adaptive cellular response to the accumulation of mis- or unfolded protein within the endoplasmic reticulum (ER)[2] This homeostatic mechanism regulates the balance between cell survival and apoptosis such that if adaptation/restoration to proteostasis fails, the apoptotic program is activated[2]. These results provide novel insights into the transcriptional networks of GBM cells in relation to their sensitivity to treatment, establishing new predictive criteria for the treatment of patients with GBM

Methods

Results

Conclusion