A CRISPR screen reveals PD-L1 regulating genes. (A) Cell surface expression of PD-L1 in ATLL cell lines, ALK⁺ ALCL cell lines, and T-ALL cell lines measured by flow cytometry. (B) Schematic design of the CRISPR library screen in the study. Two Cas9-transducing ATLL cell lines, ST1 and KK1, were used for identifying genes whose knockout decreases or increases PD-L1 expression, respectively. (C) Log₂ fold-changes (sorted/unsorted population) of genes enriched in ST1 expressing low level PD-L1 (left panel) and in KK1 expressing high level PD-L1 (right panel). (D) Top 10 log₂ fold change genes with 3 or 4 sgRNA log₂ fold changes ≥1.0 in ST1 expressing low level PD-L1 (left panel) and in KK1 expressing high level PD-L1 (right panel).