E2F1 and glioblastoma: miR-21 has also been reported to modulate chemosensitivity through the activation of nuclear factor-κB (NF-κB) signaling in glioblastoma [14]; the suppression of DNA repair proteins, including human DNA MutS homolog 2 (hMSH2), in gastrointestinal cancers [14]; the regulation of Tissue Inhibitor Of Metalloproteinases 3 (TIMP3) expression in hepatocellular carcinoma [16]; and the downregulation of the transcription factors E2F Transcription Factor 1 (E2F1) and Twist in lung adenocarcinoma [17].