Abstract 5028: Characterization of the tumor immune microenvironment in treatment-naïve EGFR-mutant NSCLC uncovers a low IFN-gamma suppressive immune phenotype

Abstract

Abstract Background: Although immune checkpoint blockade has been successfully utilized in treating patients with non-small cell lung cancer (NSCLC), the benefit of immunotherapy for patients with advanced EGFR-mutant (EGFRm) NSCLC has been limited. Data from IMpower150 trial’s subgroup analysis suggests modulation of the tumor immune microenvironment (TME) with antiangiogenic agents and chemotherapy might enhance response to anti-PD-1/PD-L1 blockade in EGFRm lung cancers. We aim to gain a deep understanding of EGFRm NSCLC TME as the first step to make EGFRm amenable to immune therapy. Methods: We queried two cohorts of resected stage I-III lung adenocarcinomas: PROSPECT (94 tumors) and Immune Genomic Profiling of NSCLC (ICON, 76 tumors). In the PROSPECT cohort (14 EGFRm vs 80 WT), we compared 10 immune markers by IHC (PD-L1, PD-1, CD3, CD4, CD8, CD45RO, CD57, CD68, FoxP3 and Granzyme B) and 44 immune regulator genes’ expression levels and pathway signatures from microarray data. We subsequently validated the observation of differentially expressed genes in the ICON cohort (15 EGFRm vs 61 WT) using IF, RNAseq and WES. Results: In the PROSPECT cohort, lower PD-L1 (2.2 vs 10.4 H-score, p<0.01) and lower GzmB (212 vs. 358 counts/mm2, p=0.02) were observed in the EGFRm compared to WT tumors. This is validated in the ICON cohort, showing lower PD-L1 expression (0.18% vs 7.28% p=0.05) and lower TMB (1.8 vs 9.0 mut/Mb, p<0.01) in EGFRm compared to WT tumors. IFN-gamma gene expression (3.89 vs 4.71 p=0.03 in PROSPECT) and signatures were low in the EGFRm tumors, suggesting a suppressive tumor microenvironment. Different than some prior reports, we found CD8+ T cells were not significantly different in EGFRm vs. WT groups. Among known immune regulators, TGFbeta was higher in the EGFRm tumors in the PROSPECT cohort, but not in the ICON cohort. Other known immune regulators, including CTLA4, LAG3, TIM3, TIGIT, IL6 and VEGFA were not differentially expressed. Conclusion: Our analysis showed that EGFR-mutant NSCLCs demonstrate a PD-L1 low, GzmB low, IFN-gamma low immune phenotype, suggesting a suppressive tumor microenvironment. We found that the CD8+ T cells were present in the tumor, but likely suppressed functionally by the negative regulators in the TME. These results direct future analysis of suppressive immune cell populations (CD4+ subpopulation, macrophages and dendritic cells) in EGFRm lung cancers, and represent an initial step for rationale combination of immune therapy to modulate the suppressed TME, which might lead to enhanced treatment efficacy to benefit patients with EGFR-mutant lung cancers. Citation Format: Xiuning Le, Marcelo V. Negrao, Alexandre Reuben, Won-Chul Lee, Edwin Parra, Jun Li, Tatiana Karpinets, Carmen Behrens, Boris Sepesi, Ara Vaporiciyan, Jack Roth, Cara Haymaker, Emily Roarty, Jianhua Zhang, Chantale Bernatchez, Jianjun Zhang, Ignacio Wistuba, Don Gibbons, John Heymach. Characterization of the tumor immune microenvironment in treatment-naïve EGFR-mutant NSCLC uncovers a low IFN-gamma suppressive immune phenotype [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5028.