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Protein Discovery Could Open Door to New Treatment for 1 in 5 Mesothelioma Patients

19103717_Immune System

That news comes from a team of Spanish researchers presenting their new findings at the European Society of Medical Oncology (ESMO) Conference in Barcelona, Spain.

The protein, called PD-L1 or programmed cell death ligand 1, is part of an immune system pathway that acts to suppress the body’s natural anti-tumor immune response, preventing the body from attacking the cancer. It appears to play a central role in how tumors invade and spread and has been linked to prognosis in several other types of cancer. The new report is the first to link PD-L1 with mesothelioma survival.

Dr. Susana Cedres and her colleagues with Vall d’Hebron Institute Oncology in Barcelona tested for PD-L1 expression in tissue samples from 119 mesothelioma patients. Patients were treated between November 2002 and February 2014. Most (71.4%) were men and the median age was 69. The presence and level of PD-L1 expression was compared to how long each patient lived.

The team found that patients with the highest levels of PD-L1 had the shortest overall survival – an average of 11 months shorter than mesothelioma patients whose cells did not express the protein. About 20% of malignant pleural mesothelioma patients tested were positive for the protein. PD-L1 expression did not appear to be dependent on gender, smoking habits, asbestos exposure or disease stage.

Although this appears to be bad news for the 1 in 5 mesothelioma patients who express PD-L1, there is a hopeful side. Identification of this key protein may open the door to new, highly targeted treatments which would only work for mesothelioma patients who express this protein.

“The results of our study could offer new treatment to this population of patients, identifying a subset of malignant pleural mesothelioma who expressed PD-L1 and could be treated with targeted therapies to PD-L1,” Cedres said. The team is recommending that PD-L1 be further evaluated as a possible target for immunotherapy.

Many top mesothelioma researchers believe that immunotherapy, which involves manipulating a patient’s immune system, represents the best hope for the treatment of mesothelioma and other intractable cancers.


Cedres, S et al, “15560 PR – Analysis of expression of programmed cell death 1 ligand 1 (PD-L1) in malignant pleural mesothelioma, European Society of Medical Oncology (ESMO) 2014 Conference, Barcelona, Spain,

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