Unfortunately for mesothelioma patients with high levels of the PD-L1 protein, they have a worse overall survival compared to patients who have lower levels. A European study looking at 200 patients wanted to see if PD-L1 and PD-1, popular targets for immunotherapy drugs, impact survival independently without immunotherapy drugs present. The researchers found that the PD-L1 protein can shorten the lives of patients, but PD-1 does not do the same.
Pleural mesothelioma is a tough to treat cancer of the pleural lining, the mesothelium that covers the lungs. Researchers continually study why mesothelioma is hard to treat, wanting to find out how to get past its natural defense system, the PD-L1 and PD-1 proteins. The full names for these proteins are programmed death ligand 1 (PD-L1) and programmed cell death 1 (PD-1). PD-L1 is typically found in immune system cells while PD-1 is part of an immune checkpoint blockade, which prevents the immune system from attacking healthy cells. For cancer cells though, it prevents the immune system from attacking them, making these cells very hard to kill. Immune checkpoint inhibitors, like the drugs Opdivo and Yervoy, lessen the protective power of these proteins. When the proteins are undermined, they are more easily attacked by the immune system.
The study had researchers from multiple European countries including Austria, Croatia, Slovenia, Hungary, Germany, and the Czech Republic. The researchers looked at tumor samples from 203 patients with pleural mesothelioma from five different European cancer centers. Immunohistochemistry was used to measure the PD-L1 and PD-1 levels of each sample. Eighteen of the patients had PD-L1 levels higher than 10 percent while a quarter of the patients had more than 10 percent of PD-1 levels in their tumor infiltrating cells. These values were not tied to the mesothelioma subtype or stage of cancer.
The researchers found that there was a relationship between PD-L1 expression and survival. The patients with higher than 10 percent of PD-L1 protein expression had a median survival of 6.3 months. The patients with lower levels of the protein had a median overall survival of 15.1 months. The researchers did not find that there was a correlation between PD-L1 and PD-1 protein levels in the body.
The researchers concluded that high PD-L1 expression (over 10 percent) in tumor cells predicts a worse overall survival in pleural mesothelioma patients. None of the patients received immunotherapy, the drugs that target PD1 and PD-L1 proteins in the body.
