LncRNA Inhibits Maturation and Accelerates Immunosuppression of Polymorphonuclear Myeloid-Derived Suppressor Cells by Enhancing the Stability of Ficolin B.

Long noncoding RNAs (lncRNA) are emerging as crucial regulators of cell biology. However, the role of lncRNAs in the development and function of polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC) remains unclear. Here, we identified that the lncRNA was highly expressed in PMN-MDSCs and that lncRNA knockdown promoted the maturation and decreased the suppressive function of PMN-MDSCs. Ficolin B (), the expression of which could be assessed as a surrogate for PMN-MDSC development, was the predicted target gene of lncRNA based on microarray results. LncRNA knockdown attenuated Fcnb protein stability in a manner dependent on the ubiquitin-proteasome system. Moreover, Fcnb inhibition downregulated the suppressive function of PMN-MDSCs. In addition, the expression of human M-ficolin, which is an ortholog of mouse Fcnb, was increased and positively correlated with arginase1 () expression. This suppressive molecule is released by MDSCs, and its production is commonly used to represent the suppressive activity of MDSCs in patients with lung cancer, suggesting clinical relevance for these findings. These results indicate that lncRNA can inhibit maturation and accelerate immunosuppression of PMN-MDSCs by enhancing Fcnb protein stability.