Upregulation of NHE1 protein expression enables glioblastoma cells to escape TMZ-mediated toxicity via increased H⁺ extrusion, cell migration and survival.
Sodium-hydrogen exchanger isoform 1 (NHE1) plays a role in survival and migration/invasion of several cancers and is an emerging new therapeutic target. However, the role of NHE1 in glioblastoma and the interaction of NHE1 expression and function in glioblastoma cells with cytotoxic temozolomide (TMZ) therapy remain unknown. In this study, we detected high levels of NHE1 protein only in primary human glioma cells (GC), glioma xenografts and glioblastoma, but not in human neural stem cells or astrocytes. GC exhibited an alkaline resting pHi (7.46±0.04) maintained by robust NHE1-mediated H(+) extrusion. GC treatment with TMZ for 2-24h triggered a transient decrease in pHi, which recovered by 48h and correlated with concurrent upregulation of NHE1 protein expression. NHE1 protein was colocalized with ezrin at lamellipodia and probably involved in GC migration. The TMZ-treated GC exhibited increased migration and invasion, which was attenuated by addition of NHE1 inhibitor HOE-642. Most importantly, NHE1 inhibition prevented prosurvival extracellular signal-regulated kinase activation and accelerated TMZ-induced apoptosis. Taken together, our study provides the first evidence that GC upregulate NHE1 protein to maintain alkaline pHi. Combining TMZ therapy with NHE1 inhibition suppresses GC migration and invasion, and also augments TMZ-induced apoptosis. These findings strongly suggest that NHE1 is an important cytoprotective mechanism in GC and presents a new therapeutic strategy of combining NHE1 inhibition and TMZ chemotherapy.
Department of Neurological Surgery, The Second Affiliated Hospital of the Harbin Medical University, Harbin 150086, China, Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Damin
D
Cong
Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Wen
W
Zhu
Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Yejie
Y
Shi
Department of Neurological Surgery, University of Wisconsin, Madison, WI 53705, USA.
Kelli B
KB
Pointer
Department of Neurological Surgery, University of Wisconsin, Madison, WI 53705, USA.
Paul A
PA
Clark
Department of Surgery, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Hongmei
H
Shen
Department of Neurological Surgery, University of Wisconsin, Madison, WI 53705, USA, Carbone Cancer Center, University of Wisconsin, Madison, WI 53705, USA and, Pittsburgh, PA 15213, USA and.
John S
JS
Kuo
Department of Neurological Surgery, The Second Affiliated Hospital of the Harbin Medical University, Harbin 150086, China.
Shaoshan
S
Hu
Department of Neurological Surgery, The Second Affiliated Hospital of the Harbin Medical University, Harbin 150086, China, Department of Neurology, University of Pittsburgh, Pittsburgh, PA 15213, USA, Veterans Affairs Pittsburgh Health Care System, Geriatric Research, Educational and Clinical Center, Pittsburgh, PA, 15213, USA sund@upmc.edu.
Dandan
D
Sun
D000136:Acid-Base Equilibrium; D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D017209:Apoptosis; D001253:Astrocytes / Q000378:metabolism; D001692:Biological Transport; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement; D002470:Cell Survival; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005909:Glioblastoma; D006801:Humans; D020935:MAP Kinase Signaling System; D051379:Mice; D058953:Neural Stem Cells / Q000378:metabolism; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics* / Q000378:metabolism; D000077204:Temozolomide; D015854:Up-Regulation
D018906:Antineoplastic Agents, Alkylating; D027682:Cation Transport Proteins; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers; D003606:Dacarbazine; D048049:Extracellular Signal-Regulated MAP Kinases; D000077204:Temozolomide