MicroRNAs and the hallmarks of cancer

It has become clear that particular microRNAs (miRNAs) function either as tumour suppressors or oncogenes, whose loss or overexpression, respectively, has diagnostic and prognostic significance. In several cases, miRNAs have been shown to affect target genes that are involved in the control of cell proliferation and apoptosis. However, malignant tumours display additional traits beyond the acquisition of enhanced growth potential and decreased cell death. Malignant disease is associated with altered tumour–host interactions leading to sustained angiogenesis and the ability to invade and metastasize. It is possible that miRNAs may act as master regulators of these aspects of tumour biology. Bioinformatic analysis of putative miRNA binding sites has indicated several novel potential gene targets of cancer-associated miRNAs that function in aspects of cell adhesion, neovascularization and tissue invasion. Among others, we speculate that miRNAs may find new roles in the regulation of E-cadherin, integrin αvβ3, hypoxia-inducible factor-1α, syndecan-1, lysyl oxidase, adamalysin metalloproteinase-17, tissue inhibitors of metalloproteinase-3, c-Met and CXCR-4 that underpin the tissue architectural changes associated with malignancy.