The Translational Research in Child Cancer group at Vall d’Hebron Institute of Research (VHIR), led by Dr. Josep Sánchez de Toledo, has started a European Project, unique in Spain, for the study of microRNAs as a therapeutic tool against the most aggressive neuroblastomas, a child cancer type. It is known that more than one third of all our genes are regulated through microRNAs, which are small molecules that regulate the gene expression. They play a key role in numerous cellular processes, especially in the onset and progression of tumors. The main goal of this research line is to restore the levels of miRNA using a complete collection of miRNAs (nearly 2,000 miRNAs) in neuroblastoma cells resistant to chemotherapy, and supervising the response to the miRNA. VHIR researchers have been working for some years now in the characterization of microRNAs as possible therapeutic tools or molecular markers for prognosis. With this study, its coordinator, Dr. Miguel Segura, explains that "all knowledge available about microRNAs will be used for developing a new therapeutic tool based on nanoparticles in order to direct them to neuroblastoma cells and modulate the expression of the necessary gens to obtain the best therapeutic response, as it was a Trojan Horse". Complementary, the levels of miRNAs will be retrospectively assessed in tumor samples, with the aim to determine whether its expression might indicate the aggressiveness of the tumor or its possible response to the treatment. Neuroblastoma is a rare malignant tumor, but the most common among newborns and children under 2 years, which affects one out of 100,000 children.