Abstract 627: NLRC5 co-mutations are associated with impaired antigen presentation and immune exclusion in KRAS-mutant lung adenocarcinoma

Abstract

Abstract Background: We recently reported that co-occurring genetic events constitute major determinants of the molecular diversity of KRAS-mutant lung adenocarcinoma (LUAC) (Skoulidis et al., Cancer Discovery, 2015). However, comprehensive evaluation of the functional impact of KRAS co-mutations on key cancer hallmarks is thus far lacking. Here, we find that inactivating mutations in NLRC5, a major transactivator of MHC class I molecules, are significantly enriched in KRAS-mutant LUAC and examine the impact of NLRC5 loss on the composition of the tumor immune microenvironment. Methods: Our cohorts consist of 513 LUACs from the TCGA (145 KRAS-mutant), 152 chemotherapy-naïve surgically resected LUAC from the PROSPECT cohort, 20 platinum-refractory KRAS-mutant LUAC from the BATTLE-2 clinical trial, as well as a panel of 31 KRAS-mutant NSCLC cell lines. Analysis of immune cell sub-population was performed using automated IF-based enumeration. Antigen presentation score was defined as the geometric mean mRNA expression of HLA-A, HLA-B, HLA-C and β2M. Results: In an unbiased analysis for genes significantly co-mutated with KRAS in LUAC (TCGA cohort) we identified NLRC5 (NLR family, CARD domain containing 5), encoding a recently discovered major transactivator of MHC class I genes (~11% of KRAS-mutant LUAC, odds ratio 2.99, P=0.0197).The spectrum of NLRC5 somatic mutations includes several nonsense and frameshift mutations, as well as missense mutations, many of which are predicted to abrogate normal NLRC5 function. In the TCGA cohort, KRAS/NLRC5 co-mutated tumors exhibited lower antigen presentation score compared to KRAS-mutant NLRC5 wild-type tumors (P=0.0369, t-test). Among KRAS-mutant LUAC from the TCGA, PROSPECT, BATTLE-2 cohorts expression of NLRC5 mRNA correlated tightly with the expression of core antigen presentation pathway components including HLA-A, HLA-B, HLA-C, β2M, TAP1, TAP2, PSMB8 and PSMB9 [in BATTLE-2: HLA-A r=0.7616, P=9.572e-05, HLA-B r=0.834, P=4.884e-06, HLA-C r=0.8029, P=2.036e-05, TAP1 r=0.8189, P=1.009e-05 ]. Similar results were obtained in a panel of 31 KRAS-mutant NSCLC cell line. Thus, both mutational and non-mutational mechanisms can account for NLRC5 inactivation. Finally, in a tumor microarray encompassing surgically resected, chemotherapy naïve LUAC (PROSPECT), NLRC5-low tumors (lower tertile for NLRC5 mRNA expression, N=34), exhibited reduced density of infiltrating CD3+ (P<0.0001, Mann-Whitney U test), CD8+(P<0.0001, Mann-Whitney U test) as well as PD-1+ cells (P<0.0001, Mann-Whitney U test) and PD-L1 Histo-score (P=0.0036, Mann-Whitney U test) compared to NLRC5-high tumors (N=41). Conclusions: Co-mutations in NLRC5, are enriched in KRAS-mutant LUAC and are associated with immune exclusion. KRAS co-mutations can shape the tumor immune micro-environment and may therefore predict for response - or lack thereof- to immunotherapy. Citation Format: Ferdinandos Skoulidis, Taghreed Hirz, Xiang Dong Lee, Jaime Rodriguez Canales, Edwin R. Parra, Pan Tong, Carmen Behrens, Vassiliki A. Papadimitrakopoulou, Jing Wang, Ignacio Wistuba, John V. Heymach. NLRC5 co-mutations are associated with impaired antigen presentation and immune exclusion in KRAS-mutant lung adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 627. doi:10.1158/1538-7445.AM2017-627