Because only a small fraction of asbestos-exposed individuals develop malignant mesothelioma1, and because mesothelioma clustering is observed in some families1, we searched for genetic predisposing factors. We discovered germline mutations in BAP1 (BRCA1-associated protein 1) in two families with a high incidence of mesothelioma. Somatic alterations affecting BAP1 were observed in familial mesotheliomas, indicating biallelic inactivation. Besides mesothelioma, some BAP1 mutation carriers developed uveal melanoma. Germline BAP1 mutations were also found in two of 26 sporadic mesotheliomas: both patients with mutant BAP1 were previously diagnosed with uveal melanoma. Truncating mutations and aberrant BAP1 expression were common in sporadic mesotheliomas without germline mutations. These results reveal a BAP1-related cancer syndrome characterized by mesothelioma and uveal melanoma. We hypothesize that other cancers may also be involved, and that mesothelioma predominates upon asbestos exposure. These findings will help identify individuals at high risk of mesothelioma who could be targeted for early intervention.

BackgroundBRCA1–associated protein 1 (BAP1) is a tumor suppressor gene located on chromosome 3p21. Germline BAP1 mutations have been recently associated with an increased risk of malignant mesothelioma, atypical melanocytic tumors and other neoplasms. To answer the question if different germline BAP1 mutations may predispose to a single syndrome with a wide phenotypic range or to distinct syndromes, we investigated the presence of melanocytic tumors in two unrelated families (L and W) with germline BAP1 mutations and increased risk of malignant mesothelioma.MethodsSuspicious cutaneous lesions were clinically and pathologically characterized and compared to those present in other families carrying BAP1 mutations. We then conducted a meta-analysis of all the studies reporting BAP1-mutated families to survey cancer risk related to the germline BAP1 mutation (means were compared using t-test and proportions were compared with Pearson χ2 test or two-tailed Fisher’s exact test).ResultsMelanocytic tumors: of the five members of the L family studied, four (80%) carried a germline BAP1 mutation (p.Gln684*) and also presented one or more atypical melanocytic tumors; of the seven members of W family studied, all carried a germline BAP1 mutation (p.Pro147fs*48) and four of them (57%) presented one or more atypical melanocytic tumors, that we propose to call “melanocytic BAP1-mutated atypical intradermal tumors” (MBAITs). Meta-analysis: 118 individuals from seven unrelated families were selected and divided into a BAP1-mutated cohort and a BAP1-non-mutated cohort. Malignant mesothelioma, uveal melanoma, cutaneous melanoma, and MBAITs prevalence was significantly higher in the BAP1-mutated cohort (p ≤ 0.001).ConclusionsGermline BAP1 mutations are associated with a novel cancer syndrome characterized by malignant mesothelioma, uveal melanoma, cutaneous melanoma and MBAITs, and possibly by other cancers. MBAITs provide physicians with a marker to identify individuals who may carry germline BAP1 mutations and thus are at high risk of developing associated cancers.

Background BAP1 is a nuclear deubiquitinase that regulates gene expression, transcription, DNA repair, and more. Several findings underscore the apparent “driver” role of BAP1 in malignant mesothelioma (MM). However the reported frequency of somatic BAP1 mutations in MM varies considerably, a discrepancy that appeared related to either methodological or ethnical differences across various studies. Methods To address this discrepancy, we carried out comprehensive genomic and immunohistochemical (IHC) analyses to detect somatic BAP1 gene alterations in 22 frozen MM biopsies from US MM patients. Results By combining Sanger sequencing, Multiplex Ligation-Dependent Probe Amplification, copy number analysis and cDNA sequencing, we found alteration of BAP1 in 14/22 biopsies (63.6%). No changes in methylation were observed. IHC revealed normal nuclear BAP1 staining in the 8 MM containing wild-type BAP1, while no nuclear staining was detected in the 14 MM biopsies containing tumor cells with mutated BAP1. Thus, IHC results were in agreement with those obtained by genomic analyses. We then extended IHC analysis to an independent cohort of 70 MM biopsies, of which there was insufficient material to perform molecular studies. IHC revealed loss of BAP1 nuclear staining in 47 out of these 70 MM biopsies (67.1%). Conclusions Our findings conclusively establish BAP1 as the most commonly mutated gene in MM, regardless of ethnic background or other clinical characteristics. Our data point to IHC as the most accessible and reliable technique to detect BAP1 status in MM biopsies.

Mesothelioma, a malignancy associated with asbestos, has been recently linked to simian virus 40 (SV40). We found that infection of human mesothelial cells by SV40 is very different from the semipermissive infection thought to be characteristic of human cells. Mesothelial cells are uniformly infected but not lysed by SV40, a mechanism related to p53, and undergo cell transformation at an extremely high rate. Exposure of mesothelial cells to asbestos complemented SV40 mutants in transformation. Our data provide a mechanistic explanation for the ability of SV40 to transform mesothelial cells preferentially and indicate that asbestos and SV40 may be cocarcinogens. M alignant mesothelioma (MM) is a tumor of the serosal lining the pleural, pericardial, and peritoneal cavities that causes about 2,500 deaths per year in the United States (1). MM arises from the malignant transformation of mesothelial cells, which are undifferentiated cells representing the adult remnants of the surface coelomic mesoderm (1). Although MM has been associated with past exposure to asbestos fibers, the mechanisms through which asbestos causes mesothelial cell transformation are unclear. The capacity of asbestos to induce autophosphorylation of the epidermal growth factor receptor, which leads to activation protein-1 activity in human mesothelial cells (HM; ref.2); the production of reactive oxygen species by cells exposed to asbestos (3); and the local and systemic immunosuppressive effects of asbestos (4) may all contribute to carcinogenesis (1). Other factors act alone or synergistically with asbestos in causing MM, because only 5-10% of individuals exposed to high levels of asbestos develop MM, and 10-20% of MM occurs in individuals with no known exposure (1).Recently, simian virus 40 (SV40) has been associated with human mesothelioma and brain and bone tumors (reviewed in refs. 1 and 5-7). SV40 (5-8) is a DNA tumor virus encoding two transforming proteins (the large tumor antigen, or Tag; and the small tumor antigen, or tag), and three capsid proteins (VP1-3). Tag is the replicase of SV40. Expression of Tag in the absence of cell lysis leads to cellular transformation through several mechanisms, including Tag-mediated inhibition of cellular p53 and Rb family proteins, induction of insulin-like growth factor-I and its receptor, and the direct mutagenic effect of Tag. SV40 tag enhances Tag functions by inhibiting protein phosphatase 2A, contributing to malignancy (1, 9). SV40 infects cells from different species, and the cell type determines the outcome of SV40 infection (5-8). Permissive monkey cells support SV40 replication, which results in cell lysis. In nonpermissive rodent cells SV40 DNA cannot be replicated, and cells are not lysed and can be transformed. Human cells are termed semipermissive because only a fraction of cells express SV40 Tag after infection, these infected cells are lysed, and cell transformation is a very rare event.SV40 is highly oncogenic in rodents (5-7). We found that intracardial injection of SV40 induced MM...

Human malignant mesothelioma (MM) is an aggressive and highly lethal cancer that is believed to be caused by chronic exposure to asbestos and erionite. Prognosis for this cancer is generally poor due to late-stage diagnosis and resistance to current conventional therapies. The damage-associated molecular pattern (DAMP) protein HMGB1 has been implicated previously in transformation of mesothelial cells. Here we show that HMGB1 establishes an autocrine circuit in MM cells that influences their proliferation and survival. MM cells strongly expressed HMGB1 and secreted it at high levels in vitro. Accordingly, HMGB1 levels in MM patient sera were higher than that found in healthy individuals. The motility, survival and anchorage-independent growth of HMGB1-secreting MM cells was inhibited in vitro by treatment with monoclonal antibodies directed against HMGB1 or against the receptor for advanced glycation end products (RAGE), a putative HMGB1 receptor. HMGB1 inhibition in vivo reduced the growth of MM xenografts in SCID mice and extended host survival. Taken together, our findings indicate that MM cells rely on HMGB1 and they offer a preclinical proof of principle that antibody-mediated ablation of HMBG1 is sufficient to elicit therapeutic activity, suggesting a novel therapeutic approach for MM treatment.

Germline BAP1 mutations predispose to several cancers, in particular malignant mesothelioma. Mesothelioma is an aggressive malignancy generally associated to professional exposure to asbestos. However, to date we found that none of the mesothelioma patients carrying germline BAP1 mutations were professionally exposed to asbestos. We hypothesized that germline BAP1 mutations might influence the asbestos-induced inflammatory response that is linked to asbestos carcinogenesis, thereby increasing the risk of developing mesothelioma after minimal exposure. Using a BAP1+/− mouse model, we found that, compared to their wild type littermates, BAP1+/− mice exposed to low-dose asbestos fibers showed significant alterations of the peritoneal inflammatory response, including significantly higher levels of pro-tumorigenic alternatively polarized M2 macrophages, and lower levels of several chemokines and cytokines. Consistent with these data, BAP1+/− mice had a significantly higher incidence of mesothelioma after exposure to very low doses of asbestos, doses that rarely induced mesothelioma in wild type mice. Our findings suggest that minimal exposure to carcinogenic fibers may significantly increase the risk of malignant mesothelioma in genetically predisposed individuals carrying germline BAP1 mutations, possibly via alterations of the inflammatory response.

We recently discovered an inherited cancer syndrome caused by BRCA1-Associated Protein 1 (BAP1) germline mutations, with high incidence of mesothelioma, uveal melanoma and other cancers and very high penetrance by age 55. To identify families with the BAP1 cancer syndrome, we screened patients with family histories of multiple mesotheliomas and melanomas and/or multiple cancers. We identified four families that shared an identical BAP1 mutation: they lived across the US and did not appear to be related. By combining family histories, molecular genetics, and genealogical approaches, we uncovered a BAP1 cancer syndrome kindred of ~80,000 descendants with a core of 106 individuals, whose members descend from a couple born in Germany in the early 1700s who immigrated to North America. Their descendants spread throughout the country with mutation carriers affected by multiple malignancies. Our data show that, once a proband is identified, extended analyses of these kindreds, using genomic and genealogical studies to identify the most recent common ancestor, allow investigators to uncover additional branches of the family that may carry BAP1 mutations. Using this knowledge, we have identified new branches of this family carrying BAP1 mutations. We have also implemented early-detection strategies that help identify cancers at early-stage, when they can be cured (melanomas) or are more susceptible to therapy (MM and other malignancies).

Donor history is a reliable predictor of HLA alloimmunization. Testing only donors with a prior history of pregnancy or transfusion is a logical and cost-effective TRALI prevention strategy.