Noncoding RNA 886 alleviates tumor cellular immunological rejection in host C57BL/C mice

Non-coding RNA 886 (nc886/VTRNA2-1) is a Pol III transcript and an atypical imprinted gene. Its exact function as a negative regulator of protein kinase R establishes its connection with innate immunity. Studies have shown that nc886 silencing is closely associated with prostate cancer progression. Previous work has constructed a cell model of stable nc886 overexpression ("mimic" or "nc886⁺ ") in PC-3M-1E8 cell lines (1E8), which are highly bone-metastatic human prostate cancer cells with low expression of nc886, and cells expressing the mimic were validated to have lower invasive and metastatic abilities than cells expressing the scramble transcript in vitro and in vivo. In this study, we directly injected mimic or scramble cells into the left ventricle of C57BL/C mice, an immunocompetent animal model, to elucidate the immune mechanisms of tumor-host interactions. Interestingly, we found that tumor cells induced the inflammation of many important organs due to xenogeneic antigen rejection; this inflammation was ultimately repaired by tissue fibrosis after 28 days, except for in the spleen. The reason is that mimic cells, as heterogeneous antigens, are mostly directly recognized by macrophages or T cells in blood, and few mimic cells enter the spleen compared with scramble cells. The induction of splenic macrophage polarization to M2 macrophages by scramble cells is a critical factor in maintaining chronic splenic inflammation. In addition, we recognize that nc886 broadly decreases the expression of some human leukocyte antigen molecules and antigen transporters. This evidence reveals the interesting role of nc886 in regulating tumor cell antigens.