Peritoneal Mesothelioma Case Highlights Importance of Genetic Testing

The case of a peritoneal mesothelioma patient who was diagnosed at just 45-years-old is drawing attention to the role of genetics in this aggressive asbestos-linked malignancy.

Sometimes referred to as “asbestos cancer”, malignant mesothelioma is almost always connected with known exposure to the fibrous mineral—often in a work environment.

But even though most mesothelioma cases can be traced back to asbestos, not all asbestos-exposed people go on to develop malignant mesothelioma.

Because of this, scientists began to believe that, in mesothelioma as in so many other types of cancer, there were likely other factors at play.

Early Mesothelioma, Genes, and Asbestos Exposure

In most cases, mesothelioma takes decades to develop, meaning that most patients are not diagnosed with mesothelioma until they are in their 60s or 70s. Most worked in a field like construction, plumbing, or mining where asbestos was known to be present.

But in a new article in the Journal of Translational Medicine, a pair of physician researchers from Loyola University and the University of Illinois say their 45-year-old patient had a family history of peritoneal mesothelioma, but had never worked or lived around asbestos.

“These findings lead us to hypothesize that the mesothelioma occurred in the setting of a germline BAP1 mutation,” write Muaiad Kittaneh and Charles Berkelhammer.

Genetic testing confirmed that their suspicions were correct—the patient did have a hereditary mutation in the gene responsible for the production of BRCA-1 associated tumor protein 1 (BAP1), a protein that is supposed to help ward off tumors. People with this mutation are much more likely to develop mesothelioma, even if their asbestos exposure is minimal.

In this case, knowing that the patient had a BAP1 mutation helped to guide treatment planning (some mesothelioma treatments work better in people with this mutation) and allowed the researchers to screen the patient’s family members to see if any of them also carried a genetic risk for mesothelioma.

“The subsequent therapeutic choices for the patient and testing of at-risk family members highlight the importance of recognizing this genetic syndrome and screening for individuals at high risk,” conclude Kittaneh and Berkelhammer.

BAP1 Syndrome and Malignant Mesothelioma

The BAP1 protein, produced by the BAP1 gene, is one of the mechanisms by which the body attempts to suppress tumors before they can gain a foothold.

In 2011, a pivotal study of familial cases of malignant mesothelioma determined that an inherited mutation on the BAP1 gene made certain asbestos-exposed people more likely than others to develop mesothelioma. This is called a germline mutation.

Another study six years later determined that BAP1 mutation (and resulting loss of BAP1 protein expression) does not have to be present at birth, but can develop later in life.

Both situations make people more susceptible to mesothelioma and several other types of cancer and have come to be referred to as “BAP1 tumor predisposition syndrome”.

People with the BAP1 mutation can develop malignant mesothelioma in the presence of even tiny amounts of asbestos—a potentially precarious situation for these individuals, given that asbestos is present in nearly every American home and public building built before 1980.

Sources:

Guo, ZY, “Loss of BRCA associated protein 1 expression in malignant mesothelioma and its diagnostic application”, October 8, 2017, Chinese Journal of Pathology

Kittaneh, M and Gerkelhammer, C, “Detecting germline BAP1 mutations in patients with peritoneal mesothelioma: benefits to patient and family members”, July 13, 2018, Journal of Translational Medicine