PDCD1 and neoplasm: Upregulation of PD-L1 expression in ALK-rearranged NSCLC was supported by an in vitro study by Hong et al., where cell apoptosis and viability tests were used to study immune suppression by ALK activation and immune reactivation by ALK TKIs and anti-PD-1 antibody in a NSCLC tumor cell and DC-CIK cell co-culture system.