AGO2 and cancer: Considering that let-7 miRNAs are repressed in cancers (Büssing et al., 2008), and Lin28a or Lin28b are highly expressed in many cancers (Piskounova et al., 2011), we speculate that the Ago2-mediated regulation of let-7 miRNPs may also be employed by cancer cells for their dysregulated proliferation.