On the contrary, tumor-infiltrating Treg cells showed quite active inhibitory phenotypes, with high expression of immune checkpoint molecules, including CTLA-4, programmed cell death 1 (PD-1), T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), lymphocyte activation gene-3 (LAG-3) and T-cell immunoreceptor with Ig and ITIM domains (TIGIT) (34). Here, PDCD1 is linked to neoplasm.