Osada & Takahashi (2011) reported that the miR-17–92 cluster interacts with E2F1 and MYC to promote tumor development in lung cancer. Although individual miRNAs can have either tumorigenic or tumor-suppressive functions, Lu et al. (2005) analyzed 217 mammalian miRNAs from 334 samples and found that miRNAs were globally down-regulated in cancers. Thomson et al. (2006) indicated that this widespread down-regulation of miRNAs is due to a failure in a Drosha processing step, suggesting that miRNA biogenesis may be impaired in cancer. This evidence concerns the gene E2F1 and cancer.