Australian Doctors Use Bacteria to Shrink Mesothelioma Tumors

Could bacteria responsible for problems ranging from sinusitis to food poisoning be used as a weapon in the fight against malignant mesothelioma? The results of a new study conducted by mesothelioma researchers at the University of Western Australia suggest that it might.

The researchers focused their study on a compound made up of proteins produced by the bacteria Staphylococcus aureus, also called ‘Staph’ bacteria. The compound has been used clinically to induce pleurodesis, a closing up of the pleural space around the lungs that can become fluid-filled in people with mesothelioma. Based on its success in pleurodesis, the Australian team wondered if the S. aureus protein compound could also shrink tumors.

Scientists in the University’s Centre for Asthma, Allergy and Respiratory Research found that treating mesothelioma cells with the S. aureus bio-product mixture effectively kills them. At the same time, the mixture induces the release of certain immune system proteins and growth-inducing compounds in healthy mesothelial cells, but not in mesothelioma cells.

When they injected the compound directly into mesothelioma tumors in mice, it prompted necrosis or the death of tumor cells while simultaneously activating tumor-fighting T-cells.  “Tumour growth was significantly inhibited in the treatment group during and after the treatment period,” reports lead study author Dr. Sally M. Lansley.  When the treatment was discontinued, mesothelioma tumors started growing again.

When the team tried the S. aureus bio-product compound in mice with peritoneal mesothelioma (in the lining of the abdomen), the compound “significantly reduced the mesothelioma load” and stimulated T-cells. Evidence of the increased T-cell production was found in the tumor-draining lymph nodes. Just as importantly, the treatment did not appear to have any negative side effects.

One of the most encouraging aspects of this study is that, unlike other experimental mesothelioma treatments, the S. aureus bio-product compound is readily available. “This proof-of-principle study demonstrates promising antitumoural activity of a commercially available compound of S. aureus bio-products against mesothelioma,” writes Dr. Lansley.

Mesothelioma is caused almost exclusively by exposure to asbestos. Although incidence of the disease has leveled off in recent years in the U.S., its incidence continues to climb worldwide. There is no cure.

Lansley, SM et al, “A commercially available preparation of Staphylococcus aureus bio-products potently inhibits tumour growth in a murine model of mesothelioma”, August 14, 2014, Respirology, Epub ahead of print