Cold Atmospheric Plasma Increases Temozolomide Sensitivity of Three-Dimensional Glioblastoma Spheroids via Oxidative Stress-Mediated DNA Damage.

Priyanka Shaw,Evelien Smits,Annemie Bogaerts,Angela Privat-Maldonado,Naresh Kumar

doi:10.3390/cancers13081780

Priyanka Shaw, Evelien Smits + Show 3 more

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https://doi.org/10.3390/cancers13081780

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Abstract

Simple SummaryCold atmospheric plasma (CAP) is gaining increasing interest for cancer treatment, for a wide range of cancer types. The studies performed with CAP as a standalone treatment modality serve as evidence that it can also be a suitable candidate for combination therapy. Temozolomide (TMZ) is used as the gold standard drug for glioblastoma treatment, one of the most aggressive malignant brain tumors in adults that remains incurable despite treatment advances. In this study, we explore whether CAP, a cocktail of reactive oxygen and nitrogen species, can amplify the cytotoxic effect on both TMZ-sensitive and TMZ-resistant glioblastoma multiforme (GBM) in three-dimensional tumor-like tissues through inhibiting the glutathione (GSH)/ glutathione peroxidase 4 (GPX4) antioxidant machinery, which can further lead to DNA damage.Glioblastoma multiforme (GBM) is the most frequent and aggressive primary malignant brain tumor in adults. Current standard radiotherapy and adjuvant chemotherapy with the alkylating agent temozolomide (TMZ) yield poor clinical outcome. This is due to the stem-like properties of tumor cells and genetic abnormalities in GBM, which contribute to resistance to TMZ and progression. In this study, we used cold atmospheric plasma (CAP) to enhance the sensitivity to TMZ through inhibition of antioxidant signaling (linked to TMZ resistance). We demonstrate that CAP indeed enhances the cytotoxicity of TMZ by targeting the antioxidant specific glutathione (GSH)/glutathione peroxidase 4 (GPX4) signaling. We optimized the threshold concentration of TMZ on five different GBM cell lines (U251, LN18, LN229, U87-MG and T98G). We combined TMZ with CAP and tested it on both TMZ-sensitive (U251, LN18 and LN229) and TMZ-resistant (U87-MG and T98G) cell lines using two-dimensional cell cultures. Subsequently, we used a three-dimensional spheroid model for the U251 (TMZ-sensitive) and U87-MG and T98G (TMZ-resistant) cells. The sensitivity of TMZ was enhanced, i.e., higher cytotoxicity and spheroid shrinkage was obtained when TMZ and CAP were administered together. We attribute the anticancer properties to the release of intracellular reactive oxygen species, through inhibiting the GSH/GPX4 antioxidant machinery, which can lead to DNA damage. Overall, our findings suggest that the combination of CAP with TMZ is a promising combination therapy to enhance the efficacy of TMZ towards the treatment of GBM spheroids.

Highlights

Glioblastoma multiforme (GBM), called glioblastoma, is the most common cancer malignancy with neuroectodermal origin, showing a considerable variability in age of onset, severity, histological features, and ability to metastasizes [1]
Griseti et al has shown that plasma-treated phosphate buffer saline (PBS) (PT-PBS) induced a fast-occurring and more pronounced cell death, visible within deeper layers of the 3D spheroid models [25]
In our recent paper [31] we showed that cold atmospheric plasma (CAP) triggered cell death in a dose- and time-dependent manner, which was due to increased reactive oxygen species (ROS) levels and an inhibition of the GSH/glutathione peroxidase 4 (GPX4) antioxidant machinery

Summary

Introduction

Glioblastoma multiforme (GBM), called glioblastoma, is the most common cancer malignancy with neuroectodermal origin, showing a considerable variability in age of onset, severity, histological features, and ability to metastasizes [1]. Temozolomide (TMZ) is used as the gold standard chemotherapeutic for the management of GBM among other drugs, i.e., bevacizumab and carmustine [2]. TMZ has adverse side effects due to the high toxicity and development of resistance over time [2,3]. To improve the effect of TMZ, many studies have combined it with radiation, other chemotherapeutic drugs, and phytochemicals, but many patients still develop drug resistance [1,4]. The distinctive tumor microenvironment of GBM stimulates an intrastromal and intratumoral hypoxia cycle, which impairs drug delivery to tumor cells [5,6] and involves aberrant dysregulation of cellular signal transduction pathways [6,7]

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