E2F3 and cancer: miR-874 is also involved in tumor progression by suppressing the protein expressions of matrix metalloproteinase-2 (MMP-2) and uPA and targeting CDK9, E2F3, HDAC1, aquaporin-3, HCA587/MAGE-C2 and signal transducer-activator of transcription 3 (STAT3), a key transcription factor that plays a significant role in human cancer angiogenesis [9–16, 18, 19].