Abstract 1379: Studying the autophagic flux in response to hypoxia in BAP1-mutated pleural mesothelioma cells linked to asbestos exposure
Authors: Michaud Chloe , Turcotte Sandra 
Published: June 2023

Introduction. Malignant mesothelioma is a rare cancer linked to asbestos exposure. It comes from the oncogenic transformation of mesothelioma cells, a protective membrane that covers several internal cavities including the pleura, peritoneum and pericardium. Malignant pleural mesothelioma (MPM) accounts for more than 90% of cases. The average survival of these patients is approximately 8 to 12 months, due to the resistance of tumors towards treatments. A well-known hallmark in cancer is tumor suppression gene inactivation. BAP1 is the most mutated gene in pleural mesothelioma (25-60%). BAP1 has a deubiquitinase activity involved in chromatin modifications, homologous recombination, DNA damage and programmed cell death. Moreover, hypoxia is an important microenvironment component within tumors, and it is demonstrated in patients with MPM. The bio-persistent localization of asbestos in mesothelioma cells has been shown to induce chronic inflammation that activates autophagic flux to survive. Autophagy is induced by several types of cellular stresses, including hypoxia. This suggests that MPM cells are dependent on autophagic flux when subjected to stress to ensure their continuity and proliferation.

Hypothesis/Objectives. The hypothesis of this project is that MPM has vulnerabilities in the autophagy/lysosome process, which can thus be targeted by chemical inhibitors to improve treatment response and efficacy. The specific objectives are to i) examine autophagy flux in MPM cells with BAP1 mutations, ii) demonstrate autophagy modulation in MPM cells towards the hypoxic response, and iii) assess the potential for autophagy and lysosome inhibitors in MP cells with mutations on BAP1 or towards the hypoxic response.

Methods/Results. To achieve this, molecular biology approaches are used to reintroduce (Gateway system), or repress (CRISRP/Cas9) the expression of BAP1 in Mero-25 and Mero-41 cells, respectively. Models were confirmed by western blot. The hypoxic chamber is used to manipulate cells in 1% O2, in which we confirmed the activation of autophagy in response to hypoxia in a kinetic timeframe of 24, 48 and 72hr. Subsequently, the autophagic flux was studied in presence of Bafilomycin A1 indicating an activation of this cellular process. The potential and cytotoxicity of autophagy or lysosome inhibitors will be evaluated by XTT and clonogenic assays.

Conclusion. Malignant pleural mesothelioma has an unmet need in novel therapeutic strategies. Our studies could contribute to improve anticancer treatments using combinatory approaches that modulate autophagy.

Citation Format: Chloe Michaud, Sandra Turcotte. Studying the autophagic flux in response to hypoxia in BAP1-mutated pleural mesothelioma cells linked to asbestos exposure [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1379.