OA22.03 HMGB1, a Target for Mesothelioma Therapy and a Biomarker to Detect Asbestos Exposure and to Identify Mesothelioma Patients

Abstract

Millions of people have been potentially exposed to asbestos, the primary cause of malignant mesothelioma (MM). Presently, no reliable biomarkers are available to identify among potentially exposed people, those individuals who have actually been exposed and who are at high risk of MM. High Mobility Group Box Protein-1 (HMGB1) is a key mediator of asbestos-induced inflammation and MM pathogenesis. Recently, HMGB1 hyper-acetylation has been functionally associated to its active release by inflammatory cells. Here, we compared the serum levels of total and hyper-acetylated HMGB1 in individuals professionally exposed to asbestos, MM patients and healthy unexposed controls. We compared the serum levels of total and hyper-acetylated HMGB1 in individuals professionally exposed to asbestos, MM patients and healthy unexposed controls. Previously proposed MM biomarkers fibulin-3, osteopontin, and mesothelin were also blindly measured in blood collected from participants to the study. HMGB1 serum levels reliably distinguished asbestos-exposed individuals and MM patients from unexposed controls. Moreover, the levels of total and hyper-acetylated HMGB1 were significantly higher in MM patients compared to asbestos-exposed individuals, and did not vary with tumor stage, suggesting that early lesions are also associated to increased HMGB1 levels. At a cutoff value of 2.00 ng/mL, the sensitivity and specificity of hyper-acetylated serum HMGB1 in differentiating MM patients from asbestos-exposed individuals was 100%, outperforming, in parallel experiments, other previously proposed biomarkers: osteopontin, fibulin-3, and mesothelin. When comparing MM patients to patients with other non-MM cytologically benign or malignant pleural effusion, the combination of two biomarkers, HMGB1 and fibulin-3, provided the highest sensitivity and specificity in differentiating these two groups. Moreover, we found that HMGB1 drives MM development and sustains MM progression, and we demonstrated that targeting HMGB1 inhibits MM cell growth and motility in vitro, reduced tumor growth in vivo and prolonged survival. Despite the relatively small size of our cohorts, our results are of exceptional significance and clinical relevance as they provide the first biomarker of asbestos exposure and indicate that hyper-acetylated HMGB1 is a very sensitive and specific biomarker to differentiate MM patients from individuals occupationally exposed to asbestos and unexposed controls. Moreover, our results on HMGB1 inhibitors indicate that HMGB1 targeting hampers the malignant phenotype of MM, offering a novel potential therapeutic approach to patients afflicted with this dismal disease.