Ivan Verduci

Colorectal cancer is the third leading cause of death in developed countries. Although the huge progresses reached in therapeutically approach, metastases remain the main issue treating colorectal cancer. Ion channels have a prominent role in the acquirement of aggressive phenotype, but most of them are involved in normal physiological processes. Among all the new potential biomarkers, Chloride Intracellular Channel 1(CLIC1) is a promising candidate. As a matter of fact, in physiological homeostasis, CLIC1 is expressed by all cell types as a cytosolic monomer. CLIC1 is a metamorphic protein that coexist in both cytosolic and transmembrane form (tmCLIC1), the latter involved in several pathological states, including cancer. CLIC1 mRNA overexpression was identified in colorectal cancer cells and is related to a poor prognosis. In this scenario, the main aim of the present work is to understand the role of tmCLIC1 in tumorigenesis, invasion, and migration potential of colorectal cancer. We first investigated the level of expression of CLIC1 protein and the activity of its transmembrane form as an ion channel in several colorectal cancer cells at different stage of development. Our results have demonstrated that tmCLIC1 protein expression and activity is proportional to the level of aggressiveness of cells, and here its action is fundamental on cellular proliferation, migration, and invasion. The role of tmCLIC1 activity in colorectal cancer was confirmed also in in vivo models. Experiments performed in zebrafish and mice models have demonstrated that the silencing of CLIC1 results in the impairment of primary tumor development and a strong reduction of distal metastases formation. Moreover, many different metastatic genes are downregulated when CLIC1 protein is absent; in particular, genes related to oxidative stress conditions, typical of cancer cells. As a matter of fact, the peculiar activity of CLIC1 and its binding with glutathione makes this protein essential for redox balance of colorectal cancer cells. Altogether, all the results obtained might be considered a starting point to unveil a mechanism of action that could represent a new milestone in anticancer research. Citation Format: Francesca Cianci, Ivan Verduci, Carlotta Tacconi, Guido Rey, Luca Roz, Alessandro Fantin, Michele Mazzanti. Transmembrane chloride intracellular channel 1 (tmCLIC1) protein as akey regulator of colorectal cancers' aggressiveness [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr LB_B11.

Quantitative real-time PCR for CLIC5 protein.

Current density/voltage relationships of CLIC1 current in CSCs

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. In vitro, CLIC1 inhibition leads to a significant arrest of GB CSCs in G1 phase of the cell cycle. Furthermore, CLIC1 knockdown impairs tumor growth in vivo. 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 G1–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. Mol Cancer Ther; 17(11); 2451–61. ©2018 AACR.

Effect of IAA on apoptosis in GB CSCs.

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. In vitro, CLIC1 inhibition leads to a significant arrest of GB CSCs in G1 phase of the cell cycle. Furthermore, CLIC1 knockdown impairs tumor growth in vivo. 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 G1–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. Mol Cancer Ther; 17(11); 2451–61. ©2018 AACR.