CD274 and neoplasm: Single silencing of PD-1 and PD-L1 and, more effectively, their combination improved the cytotoxic effect; indeed, at the middle ratio of 30:1 (effector:target) the percentage of killing efficacy of tumor infiltrating T lymphocytes to MCF-7 cells was 21% in the baseline condition and became 39% in the double siRNA condition, indicating that knocking down both immune checkpoint molecules led to a significant (p < 0.05) improvement of tumor infiltrating T lymphocyte antitumor effects.