PDCD1 and neoplasm: On one hand, tumor-infiltrating lymphocytes (TILs) can transfer surface proteins to cancer cells such as CTLA-4, PD-1, LAG-3, TIM-3, VISTA, CD38, CD80, CD86, MHC II and PD-L1 leading to an immunosuppressive TME and dampened anti-tumor immune activity (Kim et al., 2025; Suzuki et al., 2015; Shin et al., 2021; Pagliano et al., 2022; Li et al., 2021).