Hypoxia can also regulate the expression levels of CTLA4, PD1, PDL1, CD47, lymphocyte activation gene 3 (LAG3), T-cell immunoglobulin and mucin domain 3 (TIM3), as well as other immune checkpoints, through a variety of mechanisms to inhibit T cell activation, thus inhibiting the body’s anti-tumor immune response, leading to tumor immune escape. Here, PDCD1 is linked to neoplasm.