The blockade of immune checkpoint molecules (ICIs) such as programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) on host immune cells showed a remarkable efficacy across different cancer types and significantly improved survival in some patients, especially with advanced stages of the disease [5], [6], [7]. Here, PDCD1 is linked to cancer.