Germline BAP1 Mutational Landscape of Asbestos-Exposed Malignant Mesothelioma Patients with Family History of Cancer.

Heritable mutations in the BAP1 tumor suppressor gene predispose individuals to mesothelioma and other cancers. However, a large-scale assessment of germline BAP1 mutation incidence and associated clinical features in mesothelioma patients with a family history of cancer has not been reported. Therefore, we examined the germline BAP1 mutation status of 150 mesothelioma patients with a family history of cancer, 50 asbestos-exposed control individuals with a family history of cancers other than mesothelioma, and 153 asbestos-exposed individuals without familial cancer. No BAP1 alterations were found in control cohorts, but were identified in nine of 150 mesothelioma cases (6%) with a family history of cancer. Alterations among these cases were characterized by both missense and frameshift mutations, and enzymatic activity of BAP1 missense mutants was decreased compared with wild-type BAP1. Furthermore, BAP1 mutation carriers developed mesothelioma at an earlier age that was more often peritoneal than pleural (five of nine) and exhibited improved long-term survival compared to mesothelioma patients without BAP1 mutations. Moreover, many tumors harboring BAP1 germline mutations were associated with BAP1 syndrome, including mesothelioma and ocular/cutaneous melanomas, as well as renal, breast, lung, gastric, and basal cell carcinomas. Collectively, these findings suggest that mesothelioma patients presenting with a family history of cancer should be considered for BAP1 genetic testing to identify those individuals who might benefit from further screening and routine monitoring for the purpose of early detection and intervention.

Identification of a mesothelioma phenotype.

Despite the strong association of asbestos exposure to mesothelioma, only a fraction of persons exposed develop this neoplasm which is characterized by long latency and shortened survival. Familial clustering implicates both exposure and genetic predisposition as causative, but a biologically relevant mesothelioma phenotype essential to genetic analysis has not been defined. To identify a more extensive set of traits that would define a mesothelioma phenotype for the purpose of genetic analysis, we set to determine characteristics that distinguish mesothelioma patients from others exposed to asbestos and to identify factors that predict the presence of mesothelioma over other mesenchymal tumors of the peritoneum and carcinoma metastatic to the pleura. We compared demographics in four asbestos-exposed groups (controls n=347, bronchogenic cancer n=67, mesothelioma n=179 and benign asbestos-induced lung disease (BALD) n=3757). Within the mesothelioma group, we compared traits to identify characteristics associated with shortened survival. We found that compared to other asbestos-exposed groups, subjects with mesothelioma were younger at first asbestos exposure, had a greater risk of a second cancer diagnosis (odds ratio=3.29), had a longer disease latency, and had a greater risk of cancer among first-degree relatives (point estimate for risk 2.93; 95% CI 2.5-3.5). Thoracic tumor location, work exposure and male gender were consistently associated with shortened survival (1.9+/-1.3 years). We conclude that thoracic tumor location, work exposure, male gender, long latency, early age at first exposure, presence of a second cancer, and first-degree relative with cancer define a phenotype that sets mesothelioma patients with a short survival apart from other asbestos-exposed individuals. We propose that this phenotype be applied to candidate gene analysis.