Abstract

Objectives We aimed at investigating whether serum exosomal miR-16-5p could be utilized as an immunotherapy biomarker in lung adenocarcinoma (LUAD) patients administered by programmed cell death ligand-1 (PD-L1) inhibitors, and to evaluate its functions in LUAD progression. Methods Sixty LUAD sufferers and 20 healthy controls (HCs) were covered in this work. We applied both IHC and WB to examine PD-L1 level in clinical tissue samples and utilized WB to quantify PD-L1 expression in LUAD cells and LUAD xenograft tissues, respectively. Transmission electron microscopy (TEM), WB, and nanoparticle tracking analysis (NTA) were executed to confirm the exosomes isolated from serum specimens and cell culture media. To quantify of exosomal miR-16-5p level from serum and culture medium of cultured cell, qRT-PCR experiment was utilized. The connection between tissue PD-L1 level and serum exosomal miR-16-5p expression in PD-L1-positive sufferers administered by PD-L1 inhibitors was verified using Spearman correlation coefficient analysis. In addition, the overall survival (OS) and progression-free survival (PFS) rates among PD-L1 inhibitor managed sufferers were acquired through a follow-up visit. Finally, we used a group of assays, including 5-bromo-2′-dexoyuridine (BrdU) and colony formation test, wound healing experiment, flow cytometry, and nude mice xenograft experiment, to explore the functions of circulating exosomal miR-16-5p on LUAD cell proliferation, apoptosis, and migration, as well as tumor development, respectively. Results PD-L1 expression was positively related to T stage (tumor size stage), and PD-L1 inhibitor treatment reduced the PD-L1 expression and mitigated T stage in PD-L1-positive LUAD sufferers. For PD-L1-positive LUAD sufferers, elevated PD-L1 expression or reduced serum exosomal miR-16-5p level were linked to longer PFS and OS upon PD-L1 inhibitor treatment. The number of exosomes in patient's serum was more than that in the serum of healthy individua