In contrast, some miRNAs, such as miR-146a, stimulate the growth of new blood vessels in the tumour microenvironment (TME) by regulating the expression of breast cancer 1 (BRCA1) and platelet-derived growth factor receptor alpha (PDGFRA) to enhance angiogenesis in HCC endothelial cells (Zhu et al., 2013). The gene discussed is BRCA1; the disease is hepatocellular carcinoma.