PD-L1 and alternative immune checkpoints (AICs) in non-small cell lung cancer (NSCLC): Insights into the tumor immune microenvironment (TIME) and immunotherapy (IO) outcomes.

Abstract

8531 Background: PD-L1 and recently identified AICs (B7x, B7-H3, and HHLA2) may function as key immune evasion mechanisms in NSCLC and influence IO efficacy. This study explores the expression patterns of PD-L1 and AICs within the TIME and their impact on IO outcomes in NSCLC, including key molecular subtypes. Methods: NSCLC samples (n=27,629) were analyzed (Caris Life Sciences) with NextGen Sequencing on DNA (592 genes or whole exome)/RNA (whole transcriptome). Tumor cell PD-L1 expression (22c3) was assessed by IHC. Gene expression profiles were analyzed for IFN-γ score and QuantiSEQ was used to assess immune cell infiltration in the TIME. Real-world overall survival (rwOS: from time of biopsy to last contact), time on treatment [TOT: from the first pembrolizumab (pembro) treatment to the last], and OS on pembro (OSpem: from pembro start to last contact) were calculated. Mann-Whitney U, X2/Fisher-Exact, and log-rank tests were applied where appropriate. Results: PD-L1 IHC+ NSCLC and cases with high PD-L1 RNA expression had higher IFN-γ score and immune cell fractions (p<0.0001 for both) vs PD-L1 IHC- and low expression, respectively. Additionally, PD-L1 IHC+ NSCLC was associated with (a/w) higher median transcript levels (TPM) of PD-L1 and B7-H3, while PD-L1 IHC- NSCLC was a/w higher TPM of HHLA2 and B7x (p<0.0001 for all). AICs expression varied by molecular subtype, e.g., higher HHLA2/B7x RNA in EGFR mutant vs wild-type (WT) NSCLC. Moreover, PD-L1 IHC+ NSCLC and cases with high PD-L1 RNA and low B7H3 RNA were a/w longer rwOS, OSpem, and TOT; high HHLA2 RNA was a/w longer rwOS and OSpem with similar TOT; and low B7x RNA expression was a/w longer OSpem and TOT with similar rwOS (Table). Conclusions: Both PD-L1 IHC+ NSCLC and cases with high PD-L1 RNA expression are a/w a more inflammatory TIME, and superior survival and IO outcomes. Moreover, consistent with our prior HHLA2 IHC work (PMIDs: 27553831, 29374053), HHLA2 RNA expression was significantly higher in PD-L1 IHC- and EGFR mutant cases. These findings support the potential utility of transcriptomics along with protein expression for assessing novel predictive biomarkers for IO. Furthermore, the distinct expression profiles of AICs identified in our study may represent key subtypes mediating IO response in WT and EGFR mutant NSCLC. [Table: see text]