Blockade of the forward Na⁺/Ca²⁺ exchanger suppresses the growth of glioblastoma cells through Ca²⁺‐mediated cell death

Abstract

Background and PurposeThe Na+/Ca2+ exchanger (NCX) working in either forward or reverse mode participates in maintaining intracellular Ca2+ ([Ca2+]i) homeostasis, which is essential for determining cell fate. Previously, numerous blockers targeting reverse or forward NCX have been developed and studied in ischaemic tissue injury but barely examined in glioblastoma for the purpose of anti‐tumour therapy. We assessed the effect of NCX blockers on glioblastoma growth and whether NCX can become a therapeutic target.Experimental ApproachPatch‐clamp recording, Ca2+ imaging, flow cytometry, and Western blot were used to study the effects of specific and non‐specific NCX blockers on cultured glioblastoma cells. In vivo bioluminescent imaging was used to measure effects on grafted glioblastoma.Key ResultsSelectively blocking the reverse NCX with SEA0400, SN‐6, and YM‐244769 did not affect tumour cell viability. Blocking the forward NCX with bepridil, CB‐DMB, or KB‐R7943 elevated [Ca2+]i and killed glioblastoma cells. Bepridil and CB‐DMB caused Ca2+‐dependent cell cycle arrest together with apoptosis, which were all attenuated by a Ca2+ chelator BAPTA‐AM. Systemic administration of bepridil inhibited growth of brain‐grafted glioblastoma. Bepridil did not appear to have a cytotoxic effect on human astrocytes, which have higher functional expression of NCX than glioblastoma cells.Conclusions and ImplicationsLow expression of the NCX makes glioblastoma cells sensitive to disturbance of [Ca2+]i. Interventions designed to block the forward NCX can cause Ca2+‐mediated injury to glioblastoma thus having therapeutic potential. Bepridil could be a lead compound for developing new anti‐tumour drugs.

Cell Calcium Imaging as a Reliable Method to Study Neuron–Glial Circuits

“…NCX controls intracellular Ca 2+ homeostasis, and silencing of NCX1 isoforms diminished the effect of SKF 96365 on glioblastoma cells ( Song et al, 2014 ). In addition, inhibition of the forward NCX (Ca 2+ exit mode), with bepridil and CB-DMB, induced Ca 2+ -mediated injury in glioblastoma cells ( Hu et al, 2019 ). NCX maintains cytoplasmic calcium homeostatic levels, in addition to plasma membrane Ca 2+ transport ATPase (PMCA) and sarco/endoplasmic reticulum (SR/ER) Ca 2+ -ATPase (SERCA).…”

“…The Na + /Ca 2+ exchanger (NCX), which maintains cytoplasmic calcium homeostatic levels, also increases Ca 2+ levels in glioblastoma cells ( Song et al, 2014 ). Inhibition of the forward NCX (Ca 2+ exit mode) induces a Ca 2+ -mediated injury in glioblastoma cells ( Hu et al, 2019 ). Finally, G protein-coupled metabotropic receptors coupled to activation of phospholipase C result in the generation of the second messenger, inositol 1,4,5 trisphosphate, which increases intracellular Ca 2+ and diacylglycerol, involved in cancer cell proliferation, with important participation of the large-conductance voltage- and Ca 2+ -activated K + channel.…”

Imaging asparaginyl endopeptidase (AEP) in the live brain as a biomarker for Alzheimer’s disease

“…Human glioblastoma cell lines A172, U251 and rat glioma C6 cells were from American Type Culture Collection (ATCC) (Rockville, Maryland, USA). The pediatric glioblastoma cell line SF188 was kindly provided by Dr. Yu-Jie Tang (Shanghai Jiao Tong University School of Medicine, China) and Dr. Stefan Pfister (DKFZ, Germany) [ 30 ]. Cells were cultured in Dulbecco’s Modification of Eagle’s Medium (DMEM) (Gibco, Carlsbad, CA, USA) containing l -glutamine and 10% fetal bovine serum (FBS) (Gibco).…”

Role of Sodium/Calcium Exchangers in Tumors

“…In glioblastoma cells, the forward-mode NCX was shown to be predominant, since blocking the reverse mode NCX with selective inhibitors did not affect the tumor growth. It was shown that blocking the forward-mode NCX can suppress growth via Ca 2+ -mediated injury [ 37 ]. Furthermore, differently mutated melanoma cell lines (BRAF V600E -mutated and NRAS Q61R -mutated) present different Ca 2+ homeostatic status and dependence on Ca 2+ levels to survive and proliferate.…”