MiR-150 expression in breast cancer attracts and activates immune cells, and is associated with better patient outcome.

Abstract

570 Background: MicroRNA (miRNA) epigenetically regulate a large number of cancer-related genes and is known as a key player in cancer biology. MiR-150 promote cancer cell proliferation, migration, and invasion. However, there has been no study that investigated the role of miR-150 in the tumor microenvironment (TME) of breast cancer patients. Methods: Total of 1,961 breast cancer patients from multiple independent large cohorts were analyzed. These observational results were validated by in vitro experiments. Lymphocyte attraction was assessed using Transwell system. Results: miR-150 expression was the highest in triple negative breast cancer (TNBC) among subtypes and correlated with Nottingham histological grade (all p<0.001). A high miR-150 was significantly associated with better overall survival (OS) in both METABRIC and TCGA cohorts regardless of subtypes (all p<0.05 except for TNBC in TCGA). MiR-150 expression was strongly correlated with Hallmark immune-related gene sets (Allograft rejection, IL6 signaling, IFN-γ response, Inflammatory response, IL2 signaling, and apoptosis), with cytolytic activity, with infiltration of CD8+ T cells, CD4+ memory T cells, and dendritic cells, as well as with gene expressions of major immune checkpoint molecules (PD-1, CTLA4, IDO1, TIGIT, BTLA, and LAG3), consistently in both METABRIC and TCGA cohorts (all r>0.65, p<0.01). Unexpectedly, overexpression of miR-150 by mimic did not increase growth, migration, nor invasion of neither MDA-MB231 or BT-549 breast cancer cell lines. On the other hand, overexpression of miR-150 in either MDA-MB231 or BT-549 significantly increased attraction of lymphocyte cell line (Jurkart cells), which was abolished by addition of miR-150 inhibitor. By comparing the gene expression profile between miR-150 overexpressed and control cells, we found that many inflammation related gene sets including NF-kB signaling that enhance cell migration was enriched to miR-150 overexpressed cells, implicating that is how miR-150 high cells attract lymphocytes to TME. Conclusions: miR-150 expression is associated with immune cell infiltration and immune response, as well as with better survival in breast cancer patients. Overexpression of miR-150 in breast cancer cells did not promote cancer cell proliferation, migration, nor invasion; however, increased attraction of lymphocytes. Multiple inflammation-related genes were expressed higher in miR150 overexpressed MDA-MB231.