Why are certain individuals more susceptible to mesothelioma while others appear to be immune, despite receiving the same level of exposure?

In the continuing search to find a cure for the fatal disease, researchers have tried to discover exactly why only a small number of those exposed to asbestos go on to develop mesothelioma or other asbestosis diseases.

One possible answer is that a family member may inherit a ‘genetic tendency’, which can be triggered by the presence of asbestos fibres in the lung linings. New cancer research being conducted in the US suggests that those individuals who do develop mesothelioma without any obvious or known occupational exposure possess an inherited genetic mutation.

Inflammatory response

Results from laboratory studies reveal that a mutated tumour-suppressing gene associated with an increased risk of developing several types of cancers, including mesothelioma, showed a marked inflammatory response known to cause healthy cells to turn malignant.

The studies involved exposing laboratory mice with the mutated gene to very low dosages only of asbestos. The researchers found that the inflammatory response was more pronounced after exposure to the very low doses compared to mice without the gene mutation, who went on to develop mesothelioma.

The researchers conclude that those individuals carrying the mutated gene have a significantly higher risk of contracting mesothelioma caused by the pronounced inflammatory response even though their exposure to asbestos was minimal.

An entire family group

Researchers have previously looked for a genetic mutation with a direct effect on the development of mesothelioma cancer cells and found a number of factors operating within an entire family group.

The results suggest that a family link to mesothelioma cancer could exert a strong influence over the increased susceptibility to asbestos and the eventual development of the fatal disease.

Key factors included:

• Patients who had been exposed to asbestos with a parent or direct family member who had previously received a cancer diagnosis.

• The children of patients with mesothelioma who were seven times more likely to be diagnosed with cancer, which could even be more aggressive than the parent’s condition.

• Family members who had developed mesothelioma were often younger when first exposed to asbestos because cells in younger age groups possess a higher vulnerability to cancer-causing substances.

• Mesothelioma patients who were also diagnosed with a different type of cancer at the same time as being diagnosed for mesothelioma due to a greater genetic vulnerability.

• Genetic mutations that appear to also increase a patient’s susceptibility to developing a number of other cancers.

• Around 25 per cent of patients with mesothelioma but no family history of the disease who were found to have an identical genetic mutation.

“Family-based” causes

Researchers have continued to investigate the evidence for a genetic susceptibility to mesothelioma and recently discovered the potential for further ‘family-based’ causes.

Studies carried out in Italy analysed the database records of industrial disease between 1980 and 2012, which included searching for “family clusters” of mesothelioma.

Of the 1,000 cases of fatal malignant cancer recorded, between 3 – 4 per cent of all mesothelioma incidents were found to be 37 ‘family’ cases and another 13 ‘family clusters’ were also revealed.

The results appear to show a link between siblings – where one of the siblings is more likely to be diagnosed with mesothelioma if the other sibling has already contracted the disease – and especially, if both siblings were also exposed to asbestos.

The researchers also found that the highest number of mesothelioma groupings occurred between siblings affected with the disease and the parents who were not affected.

Secondary and environmental exposures

Not surprisingly, seven of the “clusters” were the primary and most well-known cause of mesothelioma, which occurs between those who work together and are both exposed to asbestos at the same workplace.

However, three of the “clusters” were either “secondary exposures”, which occurs in the same household when asbestos contaminated work clothes / overalls are brought home to be cleaned or were the result of an “environmental exposure.

The Health and Safety Executive (HSE) in the UK have previously reported an increase in the average “background mesothelioma risk” among the older workforce as a result of exposure that is not readily identifiable but could have occurred in “any setting” during peak asbestos use in the UK between the 1950s to the 1970s / 80s.