A study conducted by a group of San Francisco researchers suggests that a new biomarker may help make chemotherapy drugs more effective for mesothelioma patients.
A biomarker is a substance present in tumor cells that can help doctors identify cancer. Biomarkers are especially important in mesothelioma, a virulent cancer of the mesothelium, because it can be so difficult to diagnose. Now, medical researchers at the University of California who have been studying melanoma cell adhesion molecule (MCAM) have found it to be an even more precise biomarker than mesothelin, the most common biomarker used to diagnose mesothelioma.
MCAM is already being used to help identify other types of cancer including ovarian cancer and certain skin cancers. Unlike mesothelin, which is present in lower amounts even in non-cancerous mesothelium cells, MCAM is only found in cancer cells. It is not present in normal tissue.
In a recent study of MCAM and mesothelioma, the substance was indentified in more than 80 percent of mesothelioma tissue samples. It was found in 28 of 31 epithelioid tissue samples, 8 of 10 sarcomatoid samples and all 14 of the biphasic samples. In contrast, mesothelin is only found in epithelioid mesothelioma cells, making it a poor biomarker for other types of mesothelioma. Sarcomatoid mesothelioma accounts for 10 to 20 percent of cases and biphasic makes up 20 to 35 percent.
Once MCAM was identified as a biomarker for all three types, the second phase of the study involved testing it as a target for chemotherapy drugs. The researchers found that, when exposed to mesothelial cells in a testing dish, the anti-MCAM substance called scFv (single chain antibody) bound only with the mesothelioma cells and even increased cellular death in these cells. The targeting results were confirmed in animal testing.
The results suggests that, by attaching powerful cancer-fighting agents to an antibody like scFv, it may be possible to target just the mesothelioma tumor cells (through their MCAM) and spare surrounding tissue, minimizing size effects and improving outcomes. Writing in the journal Cancer Research, the study’s authors conclude, “These experiments show that MCAM is widely expressed by all subtypes of mesothelioma and by tumor-associated blood vessels, and may thus be an attractive therapeutic target.”
Bidlingmaier, S et al, “Identification of MCAM/CD 146 as the target antigen of a human monoclonal antibody that recognizes both epithelioid and sarcomatoid types of mesothelioma”, Cancer Research, February 2009. 1570-77.