CTLA4 and malignant pleural mesothelioma: Immune checkpoint inhibitor (ICI), such as those targeting programmed death 1 (PD1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA4), have both demonstrated remarkable anti-tumor effects in patients with advanced melanoma, renal cell carcinoma, non-small cell lung cancer, and malignant pleural mesothelioma [9].