LncRNA AK036396 inhibits maturation and accelerates immunosuppression of polymorphonuclear myeloid-derived suppressor cells by enhancing the stability of ficolin B

To identify lncRNAs involved in regulating PMN-MDSCs, an Arraystar lncRNA microarray was performed to determine the lncRNA expression profile in PMN-MDSCs. Compared to those in CD11b+Ly6G+ cells under physiological conditions, the expression of abundant lncRNAs was significantly higher in PMN-MDSCs from the tumor microenvironment. In these lncRNAs, lncRNA AK036396, whose sequencing information has been identified in the UCSC database, was one of the most significantly upregulated lncRNAs and its expression was confirmed by quantitative real-time PCR (qRT-PCR). In addition, microarray data indicated that Fcnb expression, which can be used to identify immature granuloctyes and is closely associated with granulocyte maturation, was one of the highest potential target molecules of lncRNA AK036396 in PMN-MDSCs. PMN-MDSCs used for microarray analysis were first isolated from the spleens of wild-type mice and tumor tissue of tumor-bearing mice using a mouse MDSC isolation kit (Miltenyi Biotec, Auburn, CA) following the manufacturer’s protocol. Then, the enriched cells were stained with anti-mouse CD11b-PE/Cy5.5 (0.25 μg for 1×10^6 cells) (clone: M1/70) (eBioscience, San Diego, CA) and anti-mouse Ly6G-PE (0.25 μg for 1×10^6 cells) (clone: RB6-8C5) (eBioscience, San Diego, CA) for 30 minutes at 4°C. Stained cells were collected and further sorted with FACS (FACSAriaII, BD Biosciences) to eliminate interference from other cells. An Arraystar lncRNA microarray was conducted by KangChen Bio-tech.