SUMMARY
Angiogenesis is the process that leads to the formation of new blood vessels. Under physiological conditions it occurs, inter alia, during corpus luteum formation and in some stages of the menstrual cycle. However, angiogenesis plays an essential role in many pathological conditions, particularly cancer. New blood vessel formation provides cancer cells with oxygen and essential nutrients, which stimulates tumor growth and facilitates its metastasis. Increasing evidence indicates that angiogenesis is regulated by microRNAs (miRNAs), which are small non-coding RNA molecules of 19–25 nucleotides. The main function of miRNAs is post-transcriptional regulation of gene expression, which controls many key biological processes, including cell proliferation, differentiation and migration. Endothelial miRNAs, known as angiomiRs, are presumably involved in tumor development and angiogenesis through regulation of pro- and antiangiogenic factors. To date, the miRNAs that stimulate angiogenesis are: miR-9, miR-27a, miR-30d, miR0-130b, miR-139, miR-146a, miR-150, miR-155, miR-200c, miR-296 and miR-558. Conversely, miRNAs that inhibit angiogenesis are: miR-145, miR-519c, miR-22, miR-20a, miR-92, miR-7b, miR-221, miR-222, miR-328 and miR-101.