MicroRNA‐326 negatively regulates CD155 expression in lung adenocarcinoma

Treatment with immune checkpoint inhibitors induces a durable response in some patients with non‐small‐cell lung cancer, but eventually gives rise to drug resistance. Upregulation of CD155 expression is implicated as one mechanism of resistance to programmed death receptor‐1 (PD‐1)/PD‐1 ligand (PD‐L1) inhibitors, and it is therefore important to characterize the mechanisms underlying regulation of CD155 expression in tumor cells. The aim of this study was to identify microRNAs (miRNAs) that might regulate CD155 expression at the posttranscriptional level in lung cancer. Comprehensive miRNA screening with target prediction programs and a dual‐luciferase reporter assay identified miR‐346, miR‐328‐3p, miR‐326, and miR‐330‐5p as miRNAs that bind to the 3′‐UTR of CD155 mRNA. Forced expression of these miRNAs suppressed CD155 expression in lung cancer cell lines. Immunohistochemical staining of CD155 in tissue specimens from 57 patients with lung adenocarcinoma revealed the median tumor proportion score for CD155 to be 68%. The abundance of miR‐326 in these specimens with a low level of CD155 expression was significantly greater than in specimens with a high level (p < 0.005). Our results thus suggest that miR‐326 negatively regulates CD155 expression in lung adenocarcinoma and might therefore play a role in the development of resistance to PD‐1/PD‐L1 inhibitors.