Thioredoxin Confers Intrinsic Resistance to Cytostatic Drugs in Human Glioma Cells.

Bodo Haas,Maria Wos-Maganga,Sandra Weickhardt,Marco Timmer,Niels Eckstein,Lena Schütte

doi:10.3390/ijms19102874

Abstract

Thioredoxin (Trx) overexpression is known to be a cause of chemotherapy resistance in various tumor entities. However, Trx effects on resistance are complex and depend strictly on tissue type. In the present study, we analyzed the impact of the Trx system on intrinsic chemoresistance of human glioblastoma multiforme (GBM) cells to cytostatic drugs. Resistance of GBM cell lines and primary cells to drugs and signaling inhibitors was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays. Impact of Trx inhibition on apoptosis was investigated by proteome profiling of a subset of proteins and annexin V apoptosis assays. Trx-interacting protein (TXNIP) was overexpressed by transfection and protein expression was determined by immunoblotting. Pharmacological inhibition of Trx by 1-methyl-2-imidazolyl-disulfide (PX-12) reduced viability of three GBM cell lines, induced expression of active caspase-3, and reduced phosphorylation of AKT-kinase and expression of β-catenin. Sensitivity to cisplatin could be restored by both PX-12 and recombinant expression of the upstream Trx inhibitor TXNIP, respectively. In addition, PX-12 also sensitized primary human GBM cells to temozolomide. Combined inhibition of Trx and the phosphatidylinositide 3-kinase (PI3K) pathway resulted in massive cell death. We conclude that the Trx system and the PI3K pathway act as a sequential cascade and could potentially present a new drug target.

Highlights

Gliomas are the most common primary brain tumors in humans, with glioblastoma multiforme (GBM, WHO grade IV) as the most aggressive form with the highest incidence [1,2]
Resistance is frequently driven by mutated tumor suppressor genes after loss of function like P53, retinoblastoma protein (RB), and phosphatase and tensin homolog (PTEN) and alterations in upstream receptor tyrosine kinase (RTK) signaling pathways [6,7,8]
In order to confirm this, we determined Trx and Trx-interacting protein (TXNIP) expression in three established GBM cell lines—U87, U251, and U373—and primary GBM cells, which have previously been shown by us to be intrinsically resistant to TMZ and cisplatin [30]

Summary

Introduction

Gliomas are the most common primary brain tumors in humans, with glioblastoma multiforme (GBM, WHO grade IV) as the most aggressive form with the highest incidence [1,2]. TXNIP is an upstream, negative regulator of the Trx-reducing activity. This functional antagonism comprises both suppression of Trx expression and direct protein interaction. Trx overexpression in several tumor-derived cell lines is associated with resistance to cisplatin [12]. Knockdown of TXNIP in the U251 GBM cell line promoted cell invasion, migration, and proliferation [15]. In this context, it is interesting to note that Trx expression correlates with glioma grade [16] and high Trx levels in breast cancer are associated with poor patient survival [17]

Methods

Results

Conclusion