Transcriptomic analysis of PD-L1 positive and negative hot lung adenocarcinomas identifies a different molecular immunogenic landscape

Lung cancer is a major global health problem, as it is the leading cause of cancer- related deaths worldwide. Non-small-cell lung cancer (NSCLC), the most common form, is a heterogeneous disease with adenocarcinoma and squamous cell carcinoma being the predominant subtypes. Immune-inhibiting interaction of Programmed cell death-ligand 1 (PD-L1) with programmed cell death-protein 1 (PD-1) causes checkpoint mediated immune evasion and is, accordingly, an important therapeutic target in cancer. In NSCLC, improved understanding of PD-1/PD-L1 checkpoint blockade-responsive biology is warranted. We aimed to identify the landscape of immune cell infiltration in primary lung adeno- carcinoma (LUAD) in the context of tumor PD-L1 expression and the extent of immune infiltration (“hot” vs. “cold” phenotype). Therefore, the study comprises LUAD cases (n=138) with “hot” and “cold” tumor immune phenotype and positive and negative tumor PD-L1 expression, respectively. Tumor samples were immunohistochemically analyzed for expression of PD-L1, CD4 and CD8 and further analyzed on transcriptomic level by Nanostring nCouter Pan Cancer Immune Profiling Panel. We detected significantly differentially expressed genes associated with PD-L1 positive and “hot” versus PD-L1 negative and “cold” phenotype. The presented study illustrates novel aspects of PD-L1 regulation, with potential biological relevance, as well as relevance for immunotherapy response stratification. 144 lung adenocarcinomas were classified into four different groups, depending on their PD-L1 expression status determined by IHC and total immune infiltration determined by H&E. Cases with tumors expressing PD-L1 and high total immune cell infiltration were designated as PH (n=23), cases with tumors expressing PD-L1 and low total immune cell infiltration were designated as PC (n=7), cases with no PD-L1 expression and high total immune cell infiltration were designated as NH (n=53) and cases with no PD-L1 expression and low total immune cell infiltration were designated as NC (n=55).