Quiescence status of glioblastoma stem-like cells involves remodelling of Ca2+ signalling and mitochondrial shape

Francisco J Aulestia,Marie-Claude Kilhoffer,Isabelle Néant,Marc Moreau,Jihu Dong,Jacques Haiech,Catherine Leclerc

doi:10.1038/s41598-018-28157-8

Abstract

Quiescence is a reversible cell-cycle arrest which allows cancer stem-like cells to evade killing following therapies. Here, we show that proliferating glioblastoma stem-like cells (GSLCs) can be induced and maintained in a quiescent state by lowering the extracellular pH. Through RNAseq analysis we identified Ca2+ signalling genes differentially expressed between proliferating and quiescent GSLCs. Using the bioluminescent Ca2+ reporter EGFP-aequorin we observed that the changes in Ca2+ homeostasis occurring during the switch from proliferation to quiescence are controlled through store-operated channels (SOC) since inhibition of SOC drives proliferating GSLCs to quiescence. We showed that this switch is characterized by an increased capacity of GSLCs’ mitochondria to capture Ca2+ and by a dramatic and reversible change of mitochondrial morphology from a tubular to a donut shape. Our data suggest that the remodelling of the Ca2+ homeostasis and the reshaping of mitochondria might favours quiescent GSLCs’ survival and their aggressiveness in glioblastoma.

Highlights

Multiform glioblastoma (GBM) is the most aggressive brain tumours with very poor prognosis
In order to further characterize this quiescent state, glioblastoma stem-like cells (GSLCs) were seeded in NS34 medium at pH 7.4 and 6.5 and cell proliferation and viability analysed during 5 days by cell counting and trypan blue exclusion respectively
Glioblastoma tumour recurrence has been attributed to the GSLCs which reside within the tumour mass in hypoxic and acidic microenvironments in a slow-cycling or quiescent state

Summary

Introduction

Multiform glioblastoma (GBM) is the most aggressive brain tumours with very poor prognosis. Transcriptional profiling data reveals that quiescent stem cells are characterized by a common gene signature with the down-regulation of genes associated with cell-cycle progression (i.e. CCNA2, CCNB1 and CCNE2) and the upregulation of genes classified as tumour suppressors, including the cyclin-dependent kinase inhibitor p21 (CDKN1A) and the G0/G1 switch gene 2 (G0S2)[6,7]. These data show that quiescence is a G0 phase and not a prolonged G1 phase[8]. Our data suggest that the remodelling of the Ca2+ homeostasis and the reshaping of mitochondria during the transition from proliferation to quiescence constitute a protective mechanism that favours survival and aggressiveness of GSLCs

Methods

Results

Conclusion