Mesothelioma, Malignant
A number sign (#) is used with this entry because somatic mutations in several genes have been identified in malignant mesothelioma. These genes include WT1 (607102) on chromosome 11p13, BCL10 (603517) on chromosome 1p22, CDKN2A (600160) on chromosome 9p21, NF2 (607379) on chromosome 22q12, and BAP1 (603089) on chromosome 3p21.
DescriptionMalignant mesothelioma is an aggressive neoplasm of the serosal lining of the chest etiologically linked to asbestos. It is diagnosed in approximately 2,000 to 3,000 individuals annually in the United States, most of whom die within 2 years of diagnosis (summary by Bott et al., 2011).
See also 614327 for a tumor predisposition syndrome that may contribute to the development of malignant mesothelioma upon asbestos exposure and is caused by germline mutation in the BAP1 gene (603089) on chromosome 3p21.
InheritanceIn connection with the etiology of mesothelioma, primary attention has appropriately been focused on environmental factors, particularly asbestos exposure. Li et al. (1978) reported pleural mesothelioma in the wife and daughter of a man who worked for about 25 years as a pipe insulator at a shipyard and who also developed pulmonary asbestosis and lung cancer. The wife and daughter had no asbestos exposure other than that from the man's clothing.
Risberg et al. (1980) described a family in Sweden in which the father, 3 brothers and a sister died of malignant mesothelioma. Four of the 5 probably had had asbestos exposure in the building industry. All were smokers. The area showed low incidence of malignant mesothelioma. There were 8 other sibs who were unaffected at the time of report (2 had died of other causes). The authors suggested that, in addition to smoking and asbestos, genetic factors may be involved in the pathogenesis.
Martensson et al. (1984) observed malignant mesothelioma in 2 pairs of sibs and raised a question of a hereditary predisposing factor.
Although common household or occupational exposure may be responsible for familial aggregation, Lynch et al. (1985) also raised the question of a host factor in the occurrence and/or the histologic characteristics of mesothelioma. They reported brothers who died of malignant pleural mesothelioma.
Hammar et al. (1989) reported 3 brothers who worked in the asbestos insulation business and developed mesothelioma. In a second family, a father, who was occupationally exposed to asbestos, died from a tubulopapillary peritoneal mesothelioma 11 years before his son died from a peritoneal mesothelioma of identical histologic type. Although it is possible that the son was secondarily exposed to asbestos from the father's work clothes, quantitative asbestos analysis of the son's lung tissue showed numbers of asbestos bodies well within the lower limits seen in the general urban population with no occupational exposure to asbestos. The simulation of mendelian dominant inheritance was indicated by the occurrence of familial mesothelioma contracted as an infant by a woman who died of this disorder at age 32.
A combination of asbestos exposure and host predisposition was suggested also by the report of pleural malignant mesothelioma in 3 sisters and a male cousin by Ascoli et al. (1998). The 3 women had worked in the same confectionary shop as pastry cooks and/or pastry shop assistants; the use of an asbestos-insulated oven was the putative source of exposure. The man had occupational exposure as a heating system insulation worker. Malignant cancers were reported in other relatives (larynx in a brother; pleura and lung in a mother; lung in an aunt and uncle; and lung in a cousin).
Erionite present in stones used to build the villages of Karain and Tuzkoy, Turkey, mined from nearby caves, is purported to cause mesothelioma in half of the villagers. Roushdy-Hammady et al. (2001) constructed genetic epidemiology maps to test whether some villagers were genetically predisposed to mesothelioma. Analysis of a 6-generation extended pedigree of 526 individuals showed that mesothelioma was genetically transmitted, probably in an autosomal dominant way. The incidence of malignant mesothelioma in immigrants from Karain and Tuzkoy living in Sweden and Germany was similar to or higher than that of the 2 Turkish villages, suggesting that erionite is only a cofactor in the cause of malignant mesothelioma in genetically predisposed individuals. This suggestion is supported by data showing an absence of mesothelioma cases in the towns of Karlik and other nearby villages, whose houses contain a similar amount of erionite.
Carbone and Testa (2001) claimed that genetic susceptibility to mesothelioma in the Cappadocian region of Turkey was conclusively demonstrated by the study of Roushdy-Hammady et al. (2001). Saracci and Simonato (2001) presented several reasons why the study did not prove genetic causation. One of the reasons was that before 1978, when endemic mesothelioma was recognized in this area by the study of Baris et al. (1978), mesothelioma was diagnosed as tuberculosis, lung cancer, metastatic cancers, or other disorders. Some members of the family in the reported pedigree must have died no later than 1960, long before local recognition of the disease. Dogan et al. (2001) defended the conclusion concerning a genetic factor for susceptibility to erionite carcinogenicity. Saracci and Simonato (2001) pointed out that the question has wide public health implications, given the weight that a genetic factor may carry when debating liability in asbestos-related mesotheliomas.
CytogeneticsIn 24 human malignant mesothelioma cell lines derived from untreated primary tumors, Balsara et al. (1999) performed comparative genomic hybridization analysis to identify chromosomal imbalances. Chromosomal losses accounted for the majority of genomic imbalances. The most frequent underrepresented segments were 22q (58%) and 15q11.1-q21 (54%). To map more precisely the region of 15q deletion, loss of heterozygosity analyses were performed with a panel of polymorphic microsatellite markers distributed along 15q, which defined a minimal region of chromosomal loss at 15q11.1-q15. Balsara et al. (1999) suggested that this region harbors a putative tumor suppressor gene whose loss or inactivation may contribute to the pathogenesis of many malignant mesotheliomas.
Musti et al. (2002) described a family in which 3 sisters were affected by malignant mesothelioma, 2 pleural and 1 peritoneal, and 1 brother was affected by pleural plaques. All family members had been subjected to previous asbestos exposure of environmental-residential type. For 13 years, from 1951 to 1964, their housing was provided by the father's employer, an asbestos cement factory; the factory warehouse was on the ground floor of the building in which they lived. DNA extracted from paraffin-embedded malignant mesothelioma samples was used to search for chromosomal alterations by comparative genomic hydridization (CGH). A loss at chromosome 9p, a frequent event in malignant mesothelioma, was the only change in 2 of the sisters, which suggested that this region may be the site of 1 or more oncosuppressor genes that play an important role in the development of the disease and in inducing greater genetic susceptibility to the carcinogenic effects of asbestos.
Molecular GeneticsBy immunohistochemical analysis of archival paraffin specimens and tumor cell lines, Kratzke et al. (1995) found that p16(INK4) (CDKN2; 600160) was expressed in a nonsmall cell lung cancer cell line but not in 12 of 12 primary thoracic mesotheliomas and 15 of 15 mesothelioma cell lines. All tumor specimens and the tumor cell lines showed expression of wildtype RB1 protein (614041). In addition, transfection of CDKN2 suppressed the growth of 2 independent mesothelioma cell lines. The authors concluded that inactivation of the CDKN2 gene is an essential step in the etiology of malignant mesotheliomas.
Baser et al. (2002) reported a patient with neurofibromatosis type II (NF2; 101000) who developed malignant mesothelioma after a long occupational exposure to asbestos. Genetic analysis of the tumor tissue showed loss not only of chromosome 22, where the NF2 gene (607379) is located, but also of chromosomes 14 and 15, and gain of chromosome 7. Baser et al. (2002) suggested that an individual with a constitutional mutation of an NF2 allele is more susceptible to mesothelioma. Although mesothelioma is not a common feature in NF2, the authors cited the observation of Knudson (1995) that somatic mutations of a tumor suppressor gene, such as NF2, RB1, or p53 (191170), can be common in a tumor type that is not characteristic of the hereditary disorder, perhaps due to the proliferative timing of the cells involved.
By studying copy number alterations followed by candidate gene sequencing of 53 primary malignant pleural mesothelioma (MPM) samples, Bott et al. (2011) identified the BAP1 gene (603089) on chromosome 3p21.1 as a commonly somatically inactivated gene. Twelve (23%) of 53 tumors had nonsynonymous mutations, and 16 (30%) had at least single copy genomic loss of the BAP1 locus. Tumors with mutations showed loss of nuclear staining for BAP1. BAP1 losses were confirmed in an independent collection of MPM tumors. The somatic nature of the mutations was confirmed in all tumors that had matched normal tissue available. Knockdown of BAP1 in mesothelioma cell lines expressing wildtype BAP1 resulted in proliferation defects with an accumulation of cells in S phase and also downregulated E2F (see, e.g., 189971)-responsive genes. Given the known role of BAP1 in regulatory ubiquitination of histones, the findings suggested transcriptional deregulation as a pathogenic mechanism. Sequencing also confirmed frequent inactivating mutations in the NF2 gene (11 of 53; 21%) and identified previously undescribed missense mutations in the LATS2 gene (604861) (2 of 53; 3.8%) and the LATS1 gene (603473) (2 of 53; 3.8%).