Mesothelioma is a particularly virulent type of cancer with one known cause – exposure to asbestos fibers. Approximately 80 percent of diagnosed mesothelioma cases can be definitively linked to asbestos exposure, generally over a long period of time, and usually in an occupational setting. However, not everyone who was exposed to asbestos develops the deadly cancer but genetics may affect mesothelioma. Researchers estimate that between 2 and 10 percent of those with heavy, long-term exposure to asbestos eventually develop pleural mesothelioma, which is the most common type of the cancer.
Genetics May Affect Mesothelioma
Because of this, cancer researchers have long believed that there must be other risk factors that make certain people more susceptible to the harm caused by inhaled asbestos fibers. Over the past 20 years, a number of studies have focused on finding a genetic factor that might increase the risk of developing mesothelioma. In the past few years, researchers have zeroed in on several specific gene clusters that appear to be implicated as a risk factor for the deadly disease.
Early Genetic Research in Mesothelioma
Scientists first became interested in finding a genetic risk factor for mesothelioma in the 1960s, when they noted that the cancer appeared to be more prevalent in families. Over the years, genetic research has identified several gene clusters that appear to influence whether or not a person exposed to asbestos eventually develops the cancer. Researchers have found that abnormalities in genes that suppress tumors can increase the risk of mesothelioma in people who are heavily exposed to asbestos. In the same way, abnormalities in the genes that help combat carcinogens, including glutathione-S-transferase M1 (GSTM1) and N-acetyltransferase (NAT2) , can greatly increase the risk of developing mesothelioma after exposure to asbestos fibers.
The BAP1 Gene and Mesothelioma
In 2011, researchers at University of Hawaii Cancer Center and Fox Chase Cancer Center in Philadelphia, Pennsylvania found a clear connection between family members with malignant mesothelioma and a specific gene, known as BAP1. The study focused on two families with a high incidence of mesothelioma. Researchers found that every one of the family members who were diagnosed with the illness also had a specific mutation of the BAP1 gene. They also studied 26 people who were diagnosed with the disease, but who had no family history of mesothelioma. They found that 25 percent of that group also carried the BAP1 mutation. Since that study, other researchers have confirmed the results. The implications for mesothelioma treatment are enormous.
Genetic Testing for Mesothelioma
One of the reasons that mesothelioma is so deadly is that it often goes undiagnosed until the cancer is too advanced to respond to most conventional treatments. As with other cancers, the earlier it is diagnosed, the more positive the prognosis will be. Because the symptoms of mesothelioma are so similar to many more common diseases, it often goes undetected until it is too late to treat it effectively. A simple screening test can identify the the mutated gene, which is also associated with the development of several other types of cancer. If the test identifies the mutation, doctors could advise patients on ways to avoid other risk factors – cautioning them against asbestos exposure, for example – and arrange for a schedule of screenings to watch for symptoms and changes to the mesothelial tissues that signal the development of mesothelioma.
BAP1 and Mesothelioma Prognosis
While the existence of the mutated BAP1 gene adds to the risk of developing meshothelioma, there is a silver lining. Researchers have also discovered that the presence of the mutation also seems to improve the prognosis of those diagnosed with malignant mesothelioma. In 2014, a mesothelioma study published in Carcinogenesis found that mesothelioma patients with the BAP1 mutation had significantly better survival rates than those without the mutation. Specifically, researchers at the University of Hawaii Cancer Center found that 47 percent of patients who carried the gene mutation reached the five year survival rate in comparison to 6.7% of the control group, who had been diagnosed with the cancer but did not carry the mutated gene. Even more dramatically, the researchers found that the median survival rate for the BAP1 patients diagnosed with peritoneal mesothelioma was 10 years, while the median survival rate for the same cancer in non-BAP1 patients is 6-12 months after diagnosis.
The University of Hawaii Cancer Center research has led to new medical protocols for cancer patients, including more frequent screenings for those who carry the BAP1 gene mutation, which is also associated with a number of other cancers. The more frequent screenings may lead to earlier diagnosis of the killer cancers, and improve the possibility of more successful treatment.