Concerning lung cancer, Valdmanis et al. recently described that the expression of a cluster of ∼53 microRNAs and mRNAs at the DLK1-DIO3 locus on mouse chromosome 12qF1 was markedly increased in tumors compared to non-tumoral tissue, and they have proposed a role for the cluster in the origin of cancer cells [26]. The gene discussed is DIO3; the disease is lung carcinoma.