An article recently released in the Journal of Cancer Research and a Clinical Oncology discusses the potential and known causes of mesothelioma, most notably asbestos exposure, and explores the biological processes involved in the development of mesothelioma.
Malignant mesothelioma is a cancer caused almost exclusively by asbestos exposure. Annually, approximately 2,000 to 3,000 cases of mesothelioma are diagnosed in the United States and those figures are expected to rise over the next decade.
Exposure to asbestos occurs when the microscopic fibers that make up the mineral are inhaled or ingested into the body. After asbestos-containing materials are damaged or disturbed, the release of microscopic asbestos fibers into the surrounding environment can lead to inhalation or ingestion of the toxic material.
Once inside the body, the tiny fibers can become lodged in the tissue lining (known as a mesothelial lining) of the lungs, abdomen or heart. Once lodged in the tissue, the asbestos fibers cause a series of biological reactions that lead to cancerous changes in the surrounding cells. There are currently a number of theories on how these biological reactions lead to cancerous changes, which are presented in the article “Pathogenesis of Malignant Pleural Mesothelioma and Role of Environmental and Genetic Factors.”
The article explains that “Asbsetos’ contribution to the pathogenesis of MPM [malignant pleural mesothelioma] is multifaceted with effects ranging from direct to indirect, genetic to molecular.” The more direct method of injury involves asbestos fibers penetrating the mesothelial lining, causing cellular changes at the direct site. These fibers may also damage the mitotic spindles in the cells, which control cellular division and replication, resulting in genetic damage to the cell’s DNA.
A more indirect method involves asbestos leading to the formation of reactive oxygen species (ROS). The production of ROS can be caused by the iron content in asbestos fibers. Additionally, “macrophages that have phagocytosed asbestos fibers release ROS and lymphokines, which can damage DNA and possibly suppress the immune system.
There is currently some controversy on whether all lengths of asbestos fibers can lead to cancer, but it is scientifically accepted that all forms of asbestos have the potential to cause mesothelioma cancer. The key to preventing mesothelioma is to avoid asbestos exposure altogether. Those who do develop mesothelioma usually worked in an occupational setting where exposure occurred repeatedly (or they had a spouse or family member who worked with asbestos).
Throughout the 20th century, some of the more common locations for asbestos exposure have included industries such as construction, automotive, shipyards, power plants, chemical plants, railroad, manufacturing and mining. Workers in these industries show higher rates of mesothelioma and are advised to seek regular medical checkups and X-rays as a preventative measure.