Tumor Associated Macrophage Mirna Expression Spectrum And Mir - 146 - A Role In The Tam Differentiation Mechanism

Highly infiltrated macrophage in malignant tumours is called tumor associated macrophage (TAM). In recent years, more and more studys indicated that TAM supports a series of pro-tumoral function such as tumor proliferation, invasion and metastasis, it is highly correlated with tumor poor prognosis.There are at least two types of macrophage:M1phenotype, classically activivated macrophages; M2phenotype, alternatively activated macrophages. The molecular mechnism of TAM development is still unknown. This study took mice carring breast cancer cell line4T1tumor as model, we studied the phenotype switching in TAM development, discovered M1type takes great amount in early TAM, in advanced TAM M2type takes majority amount. Which shows the cell type changed significantly in TAM development; use4T1supernate to stimulate mouse peritoneal macrophage (PM), the expression of M1macrophage specialized molecule up-regulated sharply, after the stimulation sustained for a period of time, cell turns to express M2phenotype molecule, it told us macrophage can switch in vitro as TAM does.MicroRNA is a kind of single-stranded small RNA which is less than25nt, it takes part in regulation of a lot of physical function of human body. However, the mechanism of regulation in TAM development by microRNA is poorly reported.In this study, we use microRNA chip array to investigate the profile of microRNA expression in early/advanced stage of tumor associated macrophage (TAM). The analysis suggesting that in TAM, there are23microRNAs upregulated and36microRNAs downregulated compared to PM. In early stage TAM, there are13microRNAs downregulated and17microRNA upregulated compared to advanced TAM. We then checked the expression of miR-146a, miR-222, miR-877and miR-31between PM and advanced TAM by q-PCR, which kept in line with the chip result. The GO (Gene ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) analysis of microRNA which show significant difference between TAM and PM shows the target genes of these microRNAs include Tgfbr2, Parp14, Nlk, Pkd2, Axin2, Fzd3, Azi2, Trp53ill, ect. The involved pathway includes Wnt, MAPK, Jak-STAT pathway, etc. Which indicates these microRNAs can influence TAM differentiation by those important biological function controlled by their target genes.In this study, we found in human breast cancer TAM, miR-146a expression down-regulated, which is identical with mouse expreiment result. The miR-146a expression first up-regulated, then down-regulated according to TAM development, this description comes from detection of TAM miR-146a expression in different tumor development stage. We also found the M1phenotype of PM up-expressed sharply when stimulated by4T1supernate in a short time, however, the M2special molecules up-expressed while M1special molecules down expression is detected after a period of time. The result of our study suggest that miR-146a upregulated in PM which stimulated by4T1supernate.In the functional study of miR-146a, we found that miR-146a can inhibit NO synthesis in macrophage. miR-146a overexpression promoted M2specialized molecules expression in macrophages stimulated by IL-4. Which indicated the dynamic change of TAM in different stage of tumor might be related with different expression level of miR-146a during these stages.Our study offered new evidence and data for study in the role of microRNA during TAM differentiation, its molecular mechnism and tumor therapy methods.