Signature miRNAs in peripheral blood monocytes of patients with gastric or breast cancers

The dysregulation of microRNAs (miRNAs), key posttranscriptional regulators of gene expression, is closely associated with cancer development. However, the miRNAs of monocytes, important cells of tumour immunity, have not been extensively explored. In the present study, the differentially expressed miRNAs of blood monocytes derived from gastric and breast cancer patients and healthy donors were characterized. The results indicated that 74 miRNAs were upregulated and 46 miRNAs were downregulated in monocytes of patients with breast or gastric cancers compared with the healthy donors, suggesting that these 120 miRNAs from transformed monocytes were associated with cancers. The differentially expressed miRNAs, 38 of which were novel, were further validated using quantitative real-time PCR. As an example, the results showed that miR-150-5p downregulated the CCR2 expression in monocytes by targeting Notch 3, thus leading to the suppression of tumorigenesis. The target gene analysis showed that 36 of the 120 miRNAs targeted cancer-related genes. KEGG pathway analysis indicated that the cancer-associated miRNAs were involved in pathways related to cancers, such as the HIF-1 signalling and the mTOR signalling pathways. Thus, our study provided new clues to comprehensively understand the relationship between miRNAs and cancers.