CD274 and cancer: Considering both expression levels of PD-L1 and specific tumor-infiltrating lymphocytes as candidate biomarkers to predict the immune response, Teng et al. proposed to classify cancers based on T-cell infiltration and PD-L1 into four different types of TMEs: tumor-infiltrating lymphocytes TIL+PD-L1+, TIL+PD-L1−, TIL−PD-L1+, TIL−PD-L1−21.