Abstract
Myeloid-derived suppressor cells (MDSCs) are a group of heterogeneous myeloid cells that can suppress antitumor immunity. MDSCs are divided into granulocytic (G‑MDSCs) and monocytic subsets. In the present study, the microRNA profiles of the G‑MDSCs were determined and the differential expression of microRNAs between G‑MDSCs from tumor‑bearing mice and tumor‑free mice was examined. The number of G‑MDSCs in spleens of Lewis lung carcinoma (LLC)‑bearing mice was ~6‑fold higher than in spleens of normal mice (13.54±1.74% vs. 2.14±1.44%; P<0.01) and G‑MDSCs account for about 72.9% of all MDSCs. The microRNA (miRNA) profiles of the G‑MDSCs from spleen of LLC‑bearing mice were obtained using a microRNA microarray and compared with their counterparts from spleens of tumor‑free mice. A total of 43 miRNAs with >1.3‑fold increased or decreased change were differentially expressed between the experimental and control group mice. The levels of nine of these differentially expressed miRNAs, miRNA‑468 (miR‑486), miR‑192, miR‑128, miR‑125a, miR‑149, miR‑27a, miR‑125b, miR‑350 and miR‑328, were also analyzed by RT‑qPCR to validate the microarray data. The concordance rate between the results tested by the two methods was 88.9%. Bioinformatics analyses revealed that these miRNAs may act on various target genes, including Adar, Pik3r1, Rybp and Rabgap1, to regulate the survival, differentiation and the function of tumor‑induced granulocytic MDSCs. The results revealed microRNAs and potential targets that may be vital for regulating survival, differentiation and function of G‑MDSCs induced by LLC. Further investigation should be performed to clarify the roles of these microRNAs in regulating LLC‑induced granulocytic MDSCs and the target genes that mediate their functions.