For example, research has led to significant results in the treatment of melanoma (Eroglu et al., 2015), lymphoma (Robert et al., 2015), Merkel cell carcinoma (Engels, 2019) and other tumors from relieving the immunosuppression of CD8+T cells in the microenvironment (Topalian et al., 2016), immunotherapy drugs for cytotoxic T lymphocyte antigen-4 (CTLA-4), and programmed cell death-1 (PD-1). The gene discussed is PDCD1; the disease is Merkel cell skin cancer.