Transient Receptor Potential Mucolipin-1 Channels in Glioblastoma: Role in Patient's Survival.

Maria Beatrice Morelli,Daniele Tomassoni,Antonella Arcella,Giorgio Santoni,Consuelo Amantini,Massimo Nabissi

doi:10.3390/cancers11040525

Maria Beatrice Morelli, Daniele Tomassoni + Show 4 more

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https://doi.org/10.3390/cancers11040525

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Abstract

A link between mucolipin channels and tumors has been recently suggested. Herein, we aim to investigate the transient receptor potential mucolipin (TRPML)-1 relevance in glioblastoma. The expression of this channel was evaluated via qRT-PCR and immunohistochemistry in biopsies from 66 glioblastoma patients and two human glioblastoma cell lines and compared to normal human brain, astrocytes, and epileptic tissues. The subcellular distribution of TRPML-1 was examined via confocal microscopy in the glioma cell lines. Then, to assess the role of TRPML-1, cell viability assays have been conducted in T98 and U251 cell lines treated with the specific TRPML-1 agonist, MK6-83. We found that MK6-83 reduced cell viability and induced caspase-3-dependent apoptosis. Indeed, the TRPML-1 silencing or the blockage of TRPML-1 dependent [Ca2+]i release abrogated these effects. In addition, exposure of glioma cells to the reactive oxygen species (ROS) inducer, carbonyl cyanide m-chlorophenylhydrazone (CCCP), stimulated a TRPML-1-dependent autophagic cell death, as demonstrated by the ability of the autophagic inhibitor bafilomycin A, the TRPML-1 inhibitor sphingomyelin, and the TRPML-1 silencing to completely inhibit the CCCP-mediated effects. To test a possible correlation with patient’s survival, Kaplan–Meier, univariate, and multivariate analysis have been performed. Data showed that the loss/reduction of TRPML-1 mRNA expression strongly correlates with short survival in glioblastoma (GBM) patients, suggesting that the reduction of TRPML-1 expression represents a negative prognostic factor in GBM patients.

Highlights

Glioblastoma (GBM) is the most aggressive and prevalent type of glioma, with a median overall survival (OS) of 12–15 months [1,2]
Its expression was observed in both cell lines, at lower levels compared to normal human astrocytes (NHA, n = 2), normal human brain (NHB, n =2), and peripheral blood mononuclear cells (PBMCs) used as positive controls (Figure 1a) [9]
Immunoblots from T98 and U251 glioma cell lysates incubated with anti-transient receptor potential mucolipin (TRPML)-1 antibody (Ab) F-10 clone showed a band corresponding to human TRPML-1 (Figure 1c)

Summary

Introduction

Glioblastoma (GBM) is the most aggressive and prevalent type of glioma, with a median overall survival (OS) of 12–15 months [1,2]. Several reports demonstrated the important role played by ion channels belonging to the transient receptor potential (TRP) superfamily in GBM [3,4]. Among the TRP family, mucolipins (TRPML channels) represent a distinct subfamily of endosome/lysosome Ca2+ channel proteins [5]. TRPML-2 is expressed in astrocytes and neural stem/progenitor cells. We have recently demonstrated the overexpression of TRPML-2 in high-grade GBM cell lines of astrocytic origin and GBM tissues [7]. Knockdown of TRPML-2 inhibits cell viability and proliferation and induces caspase-3-dependent apoptosis in GBM cell lines [7]

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