Genetic dissection of intratumor heterogeneity of PD‐L1 expression in EGFR ‐mutated lung adenocarcinoma

In this study, we investigated the association between PD‐L1 expression in tumor cells and underlying genetic mutations, which was analyzed in detail using laser microdissection and next‐generation sequencing analysis. To investigate whether driver mutations are involved in the background of PD‐L1 expression, the EGFR major activating mutation was selected as the most frequent driver mutation. Surgical resection specimens were used to extract sufficient amounts of nucleic acids for analysis, and the high tumor proportion score (TPS:100%) and low (TPS: 0%) PD‐L1‐expressing parts of the tumor were each laser microdissected to examine the association between PD‐L1 expression heterogeneity and genetic mutations within the same tumor. The association between PD‐L1 heterogeneity and gene mutations within the same tumor was investigated. Analysis showed no association between PD‐L1 expression heterogeneity and genetic variants, which were found to be almost identical. However, PD‐L1 expression was found to be associated with the number of tumor infiltrating lymphocytes (TILs) present in the tumor, which may be related to whether or not lymphocytes can infiltrate into the tumor depending on the tumor histological type (solid pattern, lepidic pattern, etc.) and other factors.