Mutual Influence of ROS, pH, and CLIC1 Membrane Protein in the Regulation of G1–S Phase Progression in Human Glioblastoma Stem Cells

Abstract

Glioblastoma (GB) is the most lethal, aggressive, and diffuse brain tumor. The main challenge for successful treatment is targeting the cancer stem cell (CSC) subpopulation responsible for tumor origin, progression, and recurrence. Chloride Intracellular Channel 1 (CLIC1), highly expressed in CSCs, is constitutively present in the plasma membrane where it is associated with chloride ion permeability. , CLIC1 inhibition leads to a significant arrest of GB CSCs in G phase of the cell cycle. Furthermore, CLIC1 knockdown impairs tumor growth Here, we demonstrate that CLIC1 membrane localization and function is specific for GB CSCs. Mesenchymal stem cells (MSC) do not show CLIC1-associated chloride permeability, and inhibition of CLIC1 protein function has no influence on MSC cell-cycle progression. Investigation of the basic functions of GB CSCs reveals a constitutive state of oxidative stress and cytoplasmic alkalinization compared with MSCs. Both intracellular oxidation and cytoplasmic pH changes have been reported to affect CLIC1 membrane functional expression. We now report that in CSCs these three elements are temporally linked during CSC G-S transition. Impeding CLIC1-mediated chloride current prevents both intracellular ROS accumulation and pH changes. CLIC1 membrane functional impairment results in GB CSCs resetting from an allostatic tumorigenic condition to a homeostatic steady state. In contrast, inhibiting NADPH oxidase and NHE1 proton pump results in cell death of both GB CSCs and MSCs. Our results show that CLIC1 membrane protein is crucial and specific for GB CSC proliferation, and is a promising pharmacologic target for successful brain tumor therapies. .

Intracellular Chloride Ion Channel Protein-1 Expression in Clear Cell Renal Cell Carcinoma

“…A special attention should be paid to those subgroups containing the M pattern. According with Peretti et al, the fact that CLIC1 membrane expression is crucial for cancer stem cells proliferation it may represent a potential therapeutic target (14). In accordacne with this, cc RCC subgroups with M pattern may be considered of high risk.…”

“…CLIC1 is characterized by a high versatility regarding its ability to translocate from cytosol to the nucleus and/or the plasma membrane during malignant transformation (12), based on its ability to spontaneously convert from soluble to an integral membrane-bound form. This changeable state is most probably regulated by the membrane lipid composition, especially by cholesterol, together with external factors, such as oxidation and pH (13,14), however, a precise mechanism is currently unknown. Once CLIC1 is incorporated in the plasma membrane, tumor cells become highly active, with a rapid proliferation rate (15), increased invasiveness (16) and metastatic potential (17).…”

Intracellular Chloride Channels: Novel Biomarkers in Diseases

“…The currents correlate with the tumor aggressiveness indicating a positive correlation between membrane form of CLIC1 to glioblastoma, and these results indicate that CLIC1 could be translocated to the membranes in tumor environments. Similar to gastric cancer cells, CLIC1 is shown to regulate ROS accumulation and pH changes in human glioblastoma stem cells influencing their proliferation as well as their motility, and therefore could be a crucial therapeutic target (Gritti et al, 2014;Peretti et al, 2018). CLIC1 was one among the nine genes identified in a screen for ion channels strongly modified in solid tumors and vascular malformations, especially in glioblastoma and bladder cancers (Biasiotta et al, 2016).…”

CLIC1 Protein Accumulates in Circulating Monocyte Membrane during Neurodegeneration

“…CLIC1 plays an active part in this development. According to recent investigations, membrane CLIC1 protein is involved in cellular proliferation, migration and infiltration by increasing cytosol oxidation and pH alkalization [12,14,19]. All these activities are promoted by chloride permeability, which has been associated with the presence of CLIC1 protein in the membrane in several studies.…”

“…Recent investigation demonstrated that tmCLIC1 and NADPH oxidase are involved in a feed-forward mechanism that increases the production of reactive oxygen species (ROS) [12], particularly in macrophages [13]. This is instrumental in speeding up the transition G1/S phase during the cell cycle [14]. Furthermore, it has been demonstrated that CLIC1 is involved in axonal outgrowth [15], suggesting a functional role of the protein in relation to the cytoskeleton [16,17].…”