Scientists studying a vaccine for mesotheliomahave published some of their most important preliminary data in the respected medical journal Lung Cancer.
Mesothelioma, a cancer of the organ linings caused by asbestos exposure, is highly resistant to conventional treatments. Not only does it grow quickly, but its shape makes detection and removal difficult. Unlike some other types of solid tumors which may grow in a mass, mesothelioma tumors tend to spread out in a sheet-like formation across membranes.
The UK scientists have been experimenting with a new method for targeting and destroying mesothelioma tumors, regardless of their shape. 5T4 is an antigen overexpressed by several kinds of cancer cells. The researchers tested for 5T4 in mesothelioma cells taken from 11 lab-grown cell samples, 21 tumor biopsies, and 11 samples of the pleural fluid of mesothelioma patients. For comparison, they also tested the 5T4 antibody levels in the plasma of healthy donors.
The research team confirmed that 5T4 was overexpressed in all of the mesothelioma cells tested. Next, they exposed samples of mesothelioma cells to 5T4-specific killer T-cells – the same kind of cells produced by the immune system to destroy invaders. In the lab, the 5T4-targeting killer T-cells were able to kill four out of six of the mesothelioma cell lines tested.
“We conclude that 5T4 is a potential new antigen for targeted therapies such as immunotherapy in MPM, as it is overexpressed on mesothelioma cells and recognized by 5T4-specific Cytotoxic T-cells,” wrote the researchers in a recent published report. Their findings have since been translated into a Phase II clinical trial using 5T4-targeted therapies in mesothelioma patients. The patients are being treated with a vaccine called TroVax which activates their killer T-cells to find and destroy mesothelioma cells overexpressing the 5T4 antigen.
The TroVax mesothelioma study is an example of the treatment approach known as immunotherapy. Unlike other types of mesothelioma treatments, such as chemotherapy and radiotherapy, immunotherapy is relatively non-toxic and theoretically capable of killing the targeted cells anywhere in the body. Because it is designed to ‘teach’ the body’s immune system which cells to target, the immune system ‘memory’ may help keep mesothelioma from returning.
New therapeutic agents are particularly important for mesothelioma, because it is so aggressive and because there are so few effective treatment options available. Two to three thousand Americans and 2,000 UK residents are diagnosed with mesothelioma every year.
TroVax information, Oxford BioMedica website, Accessed 4/15/12.