Additionally, the ratio of Ki67+ population fold change in PD-1+CD8+ T cells to tumor burden positively correlates with the responsiveness of PD-1 therapy, indicating that pre-existing proliferative TI PD-1+CD8+ T cell frequency is important in predicting the responsiveness of PD-1 therapy (Huang et al., 2017). The gene discussed is PDCD1; the disease is neoplasm.