Tumor cells upregulate PD-L1 expression via genomic amplification, PTEN loss leading to PI3K pathway activation (Zhao et al., 2020), or interferon signaling induction; other checkpoints like LAG-3, TIM-3, TIGIT are often co-expressed on exhausted T cells, synergistically inhibiting anti-tumor immunity. The gene discussed is CD274; the disease is neoplasm.