Tumor Mutation Burden and Differentially Mutated Genes Among Immune Phenotypes in Patients with Lung Adenocarcinoma

Abstract

Hao Wang,1,2 Shanhao Chen,1 Die Meng,1,2 Chunyan Wu,3 Junjie Zhu,4 Minlin Jiang,1,2 Jing Ning,1,2 Shengyu Wu,1,2 Lijia Wu,5 Jingjie Li,5 Bin Chen,1 Sha Zhao,1 Wei Li,1 Jia Yu,1,2 Qiyu Fang,1,2 Jun Zhu,1,2 Wencheng Zhao,1,2 Yayi He,1 Caicun Zhou1 1Department of Medical Oncology, Shanghai Pulmonary Hospital, Shanghai, 200433, People’s Republic of China; 2Medical School, Tongji University, Shanghai, 200433, People’s Republic of China; 3Pathology Department, Shanghai Pulmonary Hospital, Shanghai, 200433, People’s Republic of China; 4Surgery Department, Shanghai Pulmonary Hospital, Shanghai, 200433, People’s Republic of China; 5Genecast Biotechnology Co., Ltd, Wuxi City, Jiangsu, 214104, People’s Republic of ChinaCorrespondence: Yayi He; Caicun ZhouDepartment of Medical Oncology, Shanghai Pulmonary Hospital, No. 507 Zhengmin Road, Shanghai, People’s Republic of ChinaTel [phone]; Tel [phone]Email [email protected]; [email protected]: Nowadays, immune checkpoint blockades (ICBs) have been extensively applied in non-small cell lung cancer (NSCLC) treatment. However, the outcome of anti-program death-1/program death ligand-1 (anti-PD-1/PD-L1) therapy is not satisfying in EGFR-mutant lung adenocarcinoma (LUAD) patients and its exact mechanisms have not been fully understood. Since tumor mutation burden (TMB) and tumor immune phenotype had been thought as potential predictors for efficacy of ICBs, we further studied the TMB and immune phenotype in LUAD patients to explore potential mechanisms for poor efficacy of ICBs in EGFR positive mutated patients and to find possible factors that could impact the tumor immune phenotype which might uncover some new therapeutic strategies or combination therapies.Methods: We enrolled 223 LUAD patients who underwent surgery in our hospital. We evaluated TMB through targeted panel sequencing. The tumor immune phenotype, which could be divided into non-inflamed, intermediate and inflamed, was determined through immunohistochemistry using formalin-fixed paraffin-embedded samples. Enumeration data were analyzed by Chi-square test or Fisher exact test and shown as number (proportion). Logistic regression model was employed for univariate and multivariate analysis of the association between TMB levels and clinical characteristics.Results: The median TMB level was 4.0445 mutations/Mb. Multivariate analysis showed the TMB level was significantly associated with age (P=0.026), gender (P=0.041) and EGFR mutation status (P=0.015), and in EGFR-mutant patients we found a lower proportion of patients with mutated KRAS and BRCA2. Furthermore, we found patients with or without metastatic lesions would have different immune phenotype (P=0.007). And the mutational frequencies of ALK, CDKN2A, MAP2K1, IDH2 and PTEN were significantly different among three immune phenotypes.Conclusion: Low TMB level could be the reason for the poor efficacy of ICBs in patients having EGFR mutation. And mutational frequencies of KRAS and BRCA2 were lower in EGFR-mutant patients. Furthermore, ALK, CDKN2A, MAP2K1, IDH2 and PTEN might involve in the formation of immune phenotypes.Keywords: lung adenocarcinoma, EGFR mutation, tumor mutation burden, immune phenotype, immune checkpoint blockade

Keywords

• lung adenocarcinoma
• egfr mutation
• tumor mutation burden
• immune phenotype
• immune checkpoint blockade