Abstract 1507: Oxidative stress increases the aggressiveness of colorectal cancer by activating the antioxidant transmembrane chloride intracellular channel 1 (tmCLIC1)

Abstract Colorectal cancer is the third leading cause of death in developed country, especially in the presence of metastases. Metastatic cancer cells depend on antioxidants like glutathione (GSH) to tackle oxidative stress as they adapt to distinctive environments different from those of the primary tumor. The mechanisms that cause oxidative stress in cancer cells are poorly understood, but it was recently discovered that the Chloride Intracellular Channel 1 (CLIC1) protein supports tumor cell Reactive Species of Oxigen (ROS) overproduction. CLIC1 is a ubiquitous protein from the CLICs family, which is unique in its ability to be metamorphic. In normal cells, CLIC1 protein is expressed as a cytosolic form and binds antioxidant glutathione (GSH). Under the chronic stress typical of cancer cells, CLIC1 undergoes a conformational change, translocating to the plasma membrane (tmCLIC1). This transition releases GSH into the cytoplasm while tmCLIC1 facilitates reactive oxygen species (ROS) overproduction, fostering an aggressive cancer phenotype. Studies reveal a contradiction where cancer cells simultaneously exhibit high levels of both ROS and GSH, which are usually inversely related. In this work, we demonstrate that this paradox is linked to tmCLIC1 activity, where GSH release acts as a defense mechanism, while tmCLIC1 overexpression amplifies ROS production, driving cancer cell proliferation and metastasis. Blocking tmCLIC1 activity has shown a reduction of proliferation, migration, and invasion of metastatic colorectal cancer cells (CRC). The study also demonstrated that forcing non-metastatic CRC cells (SW480) to release GSH using the antioxidant N-Acetyl Cysteine (NAC) enriched cytoplasmic GSH and increased tmCLIC1 expression. This effect, however, was absent in cells where CLIC1 was silenced, proving that GSH release depends on tmCLIC1 activity. These cells were converted from non-aggressive cell lines to metastatic ones in vitro and in vivo. These findings challenge the traditional view of antioxidants in cancer treatment, suggesting that tmCLIC1 inhibition could serve as a novel therapeutic strategy against metastatic colorectal cancer, addressing a pressing societal health concern. Citation Format: Francesca Cianci, Guido Rey, Carlotta Tacconi, Luca Palloni, Matteo Ranucci, Giulia Bertolini, Luca Roz, Alessandro Fantin, Michele Mazzanti. Oxidative stress increases the aggressiveness of colorectal cancer by activating the antioxidant transmembrane chloride intracellular channel 1 (tmCLIC1). [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1507.