To study this further in our patient cohort, subjects were divided into three groups based on their CTL-EC engagement and tumor PD-L1 expression: Group 1: high engagement and high PD-L1 expression representing reactive upregulation; Group 2: high engagement and low PD-L1 expression suggestive of a passive relationship between tumor cells and CTLs; Group 3: low engagement and low PD-L1 expression representing inherent immune resistance (Fig. 5F). This evidence concerns the gene CD274 and neoplasm.