Store-Operated Calcium Channels Control Proliferation and Self-Renewal of Cancer Stem Cells from Glioblastoma.

Elodie Terrié,Nadine Déliot,Valérie Coronas,Patricia Arnault,Thomas Harnois,Patrick Bois,Bruno Constantin,Yassine Benzidane,François Vallette,Laëtitia Cousin,Lisa Oliver

doi:10.3390/cancers13143428

Abstract

Simple SummaryGlioblastoma is a high-grade primary brain tumor that contains a subpopulation of cells called glioblastoma stem cells, which are responsible for tumor initiation, growth and recurrence after treatment. Recent transcriptomic studies have highlighted that calcium pathways predominate in glioblastoma stem cells. Calcium channels have the ability to transduce signals from the microenvironment and are therefore ideally placed to control cellular behavior. Using multiple approaches, we demonstrate in five different primary cultures, previously derived from surgical specimens, that glioblastoma stem cells express store-operated channels (SOC) that support calcium entry into these cells. Pharmacological inhibition of SOC dramatically reduces cell proliferation and stem cell self-renewal in these cultures. By identifying SOC as a critical mechanism involved in the maintenance of the stem cell population in glioblastoma, our study will contribute to the framework for the identification of new therapies against this deadly tumor.Glioblastoma is the most frequent and deadly form of primary brain tumors. Despite multimodal treatment, more than 90% of patients experience tumor recurrence. Glioblastoma contains a small population of cells, called glioblastoma stem cells (GSC) that are highly resistant to treatment and endowed with the ability to regenerate the tumor, which accounts for tumor recurrence. Transcriptomic studies disclosed an enrichment of calcium (Ca2+) signaling transcripts in GSC. In non-excitable cells, store-operated channels (SOC) represent a major route of Ca2+ influx. As SOC regulate the self-renewal of adult neural stem cells that are possible cells of origin of GSC, we analyzed the roles of SOC in cultures of GSC previously derived from five different glioblastoma surgical specimens. Immunoblotting and immunocytochemistry experiments showed that GSC express Orai1 and TRPC1, two core SOC proteins, along with their activator STIM1. Ca2+ imaging demonstrated that SOC support Ca2+ entries in GSC. Pharmacological inhibition of SOC-dependent Ca2+ entries decreased proliferation, impaired self-renewal, and reduced expression of the stem cell marker SOX2 in GSC. Our data showing the ability of SOC inhibitors to impede GSC self-renewal paves the way for a strategy to target the cells considered responsible for conveying resistance to treatment and tumor relapse.

Highlights

Glioblastoma (GBM) is a high-grade primary brain tumor and ranks among the most lethal of all human cancers
To investigate whether glioblastoma stem cells (GSC) expressed the main protein components supporting storeoperated Ca2+ entries, we examined in these cells grown as spheres, the presence of both TRPC1 and Orai1 channels as well as their endoplasmic reticulum (ER) activator STIM1
Western blot analysis showed that all cultures expressed detectable levels of Orai1, TRPC1 and STIM1, at different levels (Figure 1A)

Summary

Introduction

Glioblastoma (GBM) is a high-grade primary brain tumor and ranks among the most lethal of all human cancers. Treatment for patients includes maximal tumor resection followed by radiotherapy with concomitant chemotherapy with temozolomide. Despite this multimodal treatment, glioblastoma remains a refractory malignancy with 90% of patients experiencing tumor relapse and with a median survival of barely 15 months from the time of diagnosis [1]. In addition to being highly infiltrative, GBM exhibit complex cellular and molecular heterogeneity, both between patients and within individual tumors, which represents a major hurdle for an effective treatment and leads to nearly systematic recurrence. The poor response of GBM to treatment and tumor relapse have been ascribed to the persistence of a rare population of cells that, like physiological stem cells, are endowed with regenerative potential and have been termed glioblastoma stem cells (GSC) [5]. A complete cure of GBM would require the eradication of these tumor initiating and propagating cells [5]

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