A team from the Oncology and Molecular Pathology group at Vall d’Hebron Institute of Research (VHIR), led by Dr. Matilde Lleonart, have discovered the important role of miR-125b in diverse biological processes related to breast cancer. This finding allowed researchers to identify 4 new target proteins in breast tumors. The results of the study, funded by BBVA Foundation, were published in "http://www.plosone.org/article/info%3Adoi/10.1371/journal.pone.0076247" PLOS ONE. MicroRNAs are regulators of the expression of thousands of genes. It has been estimated that half of the genes of our genome are regulated by microRNAs which are also emerging as key regulators of tumorigenesis and tumor progression. Studies are mainly focused in the biological and functional characterization of microRNAs with substantial differences between cancer tissue and normal breast tissue. For some years now, VHIR’s group is working in the study of microRNAs differently expressed in cancer tissue and normal breast tissue. With the expression pattern of microRNAs, researchers can predict, even without the information of the origin of the tissue, whether it comes from a tumor or not. In fact, microRNAs are not only useful for prognosis, but also for diagnosis and therapy. The research led at Vall d’Hebron had the aim to characterize therapeutic microRNAs to eradicate malignant processes. A total of 35 miRNAs were identified in different types of breast cancer that according to Dr. Lleonart, “represent a molecular signature which is representative of malignancy, because they have an effect on multiple genes”. The research line started the experimental work with human tumors. MiR-125b exhibited the largest decrease in expression when comparing cancer tissue and adjacent normal breast tissue, and it was found to perform its tumor suppressor function via the direct targeting of the 4 new genes identified, –CK2-alpha, ENPEP, CCNK y MEGF9–.