Decreased Equilibrative Nucleoside Transporter 1 (ENT1) Activity Contributes to the High Extracellular Adenosine Levels in Mesenchymal Glioblastoma Stem-Like Cells.

Sebastián Alarcón,Daniel Uribe,Claudia Quezada,Rodrigo Fernández,Carolina Villarreal,Angel Ayuso Sacido,María De Los Ángeles Toro,Rómulo Melo,Rody San Martín

doi:10.3390/cells9081914

Sebastián Alarcón, Daniel Uribe + Show 7 more

Open Access

https://doi.org/10.3390/cells9081914

Copy DOI

Abstract

Glioblastoma multiforme is one of the most malignant types of cancer. This is mainly due to a cell subpopulation with an extremely aggressive potential, called glioblastoma stem-like cells (GSCs). These cells produce high levels of extracellular adenosine which has been associated with increased chemoresistance, migration, and invasion in glioblastoma. In this study, we attempted to elucidate the mechanisms that control extracellular adenosine levels in GSC subtypes. By using primary and U87MG-derived GSCs, we associated increased extracellular adenosine with the mesenchymal phenotype. [3H]-adenosine uptake occurred mainly through the equilibrative nucleoside transporters (ENTs) in GSCs, but mesenchymal GSCs have lower expression and ENT1-mediated uptake activity than proneural GSCs. By analyzing expression and enzymatic activity, we determined that ecto-5′-nucleotidase (CD73) is predominantly expressed in proneural GSCs, driving AMPase activity. While in mesenchymal GSCs, both CD73 and Prostatic Acid Phosphatase (PAP) contribute to the AMP (adenosine monophosphate) hydrolysis. We did not observe significant differences between the expression of proteins involved in the metabolization of adenosine among the GCSs subtypes. In conclusion, the lower expression and activity of the ENT1 transporter in mesenchymal GSCs contributes to the high level of extracellular adenosine that these GSCs present.

Highlights

Glioblastoma (GBM) is one of the most malignant types of tumors of the central nervous system [1].This neoplasia is found in the intracranial tissue/glial cells, which are responsible for supplying functional nutrients and oxygen to the neurons [2]
Cells were subjected to different culture conditions to generate Glioblastoma Stem-like Cells (GSCs) and non-GSCs as described in the cells were subjected to different culture conditions to generate GSCs and non-GSCs as described in Methods section. (A) Total adenosine uptake activity mediated by concentrative nucleoside transporter the Methods section. (A) Total adenosine uptake activity mediated by concentrative nucleoside (CNT)transporter and equilibrative nucleoside transporter systems were obtained a transport (CNT) and equilibrative nucleoside(ENT)
Our research group previously demonstrated that GSCs have high levels of extracellular adenosine compared to non-GSCs [19], which is associated with pathogenic signaling through the adenosine compared to non-GSCs [19], which is associated with pathogenic signaling through the adenosine receptor which in turn mediates the greater chemoresistant and invasive potential observed adenosine receptor which in turn mediates the greater chemoresistant and invasive potential in GBM [6,19,39]

Summary

Introduction

Glioblastoma (GBM) is one of the most malignant types of tumors of the central nervous system [1]. This neoplasia is found in the intracranial tissue/glial cells, which are responsible for supplying functional nutrients and oxygen to the neurons [2]. Evidence suggests that CSCs play an important role during the onset, progression, and recurrence of a tumor and are primarily responsible for radiation and chemotherapy resistance and, poor patient survival [9,10]. Glioblastoma Stem-like Cells (GSCs) have emerged as the primary target for therapy against Glioblastoma, but success has been limited [11,12]. Previous studies have identified two GSC subtypes called proneural and mesenchymal GSCs, which exhibit different metabolic, growth, and malignancy properties and, different response to therapies [13,14,15]

Methods

Results

Discussion

Conclusion