Targeting inflammatory factors for chemoprevention and cancer interception to tackle malignant mesothelioma.

Mesothelioma is an incurable cancer of the mesothelial lining often caused by exposure to asbestos. Asbestos-induced inflammation is a significant contributing factor in the development of mesothelioma, and genetic factors also play a role in the susceptibility to this rapidly progressive and treatment-resistant malignancy. Consequently, novel approaches are urgently needed to treat mesothelioma and prevent or reduce the overall incidence of this fatal disease. In this research perspective, we review the current state of chemoprevention and cancer interception progress in asbestos-induced mesothelioma. We discuss the different preclinical mouse models used for these investigations and the inflammatory factors that may be potential targets for mesothelioma prevention. Preliminary studies with naturally occurring phytochemicals and synthetic agents are reviewed. Results of previous clinical chemoprevention trials in populations exposed to asbestos and considerations regarding future trials are also presented.

BAP1 forms a trimer with HMGB1 and HDAC1 that modulates gene × environment interaction with asbestos.

Carriers of heterozygous germline BAP1 mutations (BAP1+/-) are affected by the "BAP1 cancer syndrome." Although they can develop almost any cancer type, they are unusually susceptible to asbestos carcinogenesis and mesothelioma. Here we investigate why among all carcinogens, BAP1 mutations cooperate with asbestos. Asbestos carcinogenesis and mesothelioma have been linked to a chronic inflammatory process promoted by the extracellular release of the high-mobility group box 1 protein (HMGB1). We report that BAP1+/- cells secrete increased amounts of HMGB1, and that BAP1+/- carriers have detectable serum levels of acetylated HMGB1 that further increase when they develop mesothelioma. We linked these findings to our discovery that BAP1 forms a trimeric protein complex with HMGB1 and with histone deacetylase 1 (HDAC1) that modulates HMGB1 acetylation and its release. Reduced BAP1 levels caused increased ubiquitylation and degradation of HDAC1, leading to increased acetylation of HMGB1 and its active secretion that in turn promoted mesothelial cell transformation.

BAP1 gene mutations in Egyptian patients with advanced sporadic malignant pleural mesothelioma (MPM): relation with clinical outcomes and survival.

BACKGROUND: Malignant Pleural Mesothelioma (MPM) is a lethal cancer with few therapeutic options. Patients with MPM have a poor prognosis, with estimated 1 year median survival and currently no treatment is curative. The BRCA associated protein 1 (BAP1) has the highest prevalence of protein-altering mutations identified in MPM. AIMS: Assessment of the frequency and pattern of BAP1 gene mutations in Egyptian patients with advanced sporadic MPM in relation to disease progression and survival rates in order to identify a novel therapeutic target for MPM. METHODS: This prospective, cohort study included 122 patients who were diagnosed and treated as advanced MPM. BAP1 gene mutations were assessed from circulating tumor cells (CTCs) by polymerase chain reaction (PCR) and sequencing and these mutations have been confirmed using the tumor tissue. BAP1 immunohistochemistry was performed using the Dako Envision visualization system. The relationship between BAP1 gene mutations, PFS and OS rates was assessed using the log rank test. The relationship between BAP1 gene mutations, clinical response and patient's clinicopathological characteristics was assessed using chi-square test. RESULTS: Forty seven (38.5%) MPM cases showed one or more mutations in BAP1 gene. The presence of BAP1 mutations associated significantly with BAP1 protein expression (p < 0.001), the incidence of organ metastasis (p = 0.04), PFS after second line treatment (p = 0.04) and clinical response after second line treatment (p = 0.01) only. CONCLUSION: BAP1 gene mutations are relatively common in Egyptian patients with advanced sporadic MPM. BAP1 mutations are associated with disease progression especially after second line therapy and the incidence of organ metastasis.