Tumor growth and progression depend on angiogenesis, a process of new blood vessels formation from a preexisting vascular endothelium. Tumors promote angiogenesis by secreting or activating angiogenic factors that stimulate endothelial proliferation and migration and capillary morphogenesis. The newly formed blood vessels provide nutrients and oxygen to the tumor, increasing its growth. Thus, angiogenesis plays a key role in cancer progression and development of metastases. An important growth factor that promotes angiogenesis and participates in a variety of physiological and pathological processes is the vascular endothelial growth factor (VEGF-A or VEGF). Overexpression of VEGF results in increased angiogenesis in normal and pathological conditions. The existence of an alternative site of splicing at the 3' untranslated region of the mRNA results in the expression of isoforms with a C-terminal region which are downregulated in tumors and may have differential inhibitory effects. This suggests that control of splicing can be an important regulatory mechanism of angiogenesis in cancer.

Introduction: Liver cirrhosis (LC) is a heterogeneous liver disease, the last stage of liver fibrosis, and the major risk factor for hepatocellular carcinoma (HCC). Our study aimed to evaluate the expression of microRNAs and the endothelial vascular growth factor (VEGFA) gene in LC and HCC. Material and methods: The sample group consisted of 46 tissue samples: 21 of LC, 15 of HCC, and 10 of non-tumoural and non-cirrhotic liver tissue (control group). MiRNAs were chosen based on a mirDIP prediction database as regulators of the VEGFA gene. Gene expression of VEGF and miRNAs was quantified by real-time quantitative polymerase chain reaction. VEGFA protein expression was evaluated by ELISA. Results: VEGFA gene expression was significantly overexpressed in LC compared to the control group (p < 0.0001). Hsa-miR-206 (p = 0.0313) and hsa-miR-637 (p = 0.0156) were down-expressed in LC. In HCC, hsa-miR-15b (p = 0.0010), hsa-miR-125b (p = 0.0010), hsa-miR-423-3p (p = 0.0010), hsa-miR-424 (p = 0.0313), hsa-miR-494 (p < 0.0001), hsa-miR-497 (p < 0.0001), hsa-miR-612 (p = 0.0078), hsa-miR-637 (p < 0.0001), and hsa-miR-1255b (p = 0.0156) presented down-expression. Conclusions: Overexpression of VEGFA in LC suggests impairment of angiogenesis in this tissue. The differential expression of microRNAs in LC and HCC observed in our study can lead to the evaluation of possible biomarkers for these diseases.

MicroRNAs (miRNAs) are short non-coding RNA molecules acting as important posttranscriptional gene and protein expression regulators in cancer. The study goal was to examine VEGFA (vascular endothelial growth factor A) expression in hepatocellular carcinoma (HCC) cell lines upon transfection miR-612, miR-637, or miR-874. Methods: MiR-612 mimics, miR-637 mimics, or miR-874 inhibitors were transfected using Lipofectamine RNAiMax in both HCC cell lines, HepG2 and HuH-7. Real-time PCR, Western blotting, and ELISA methods were used to evaluate VEGFA regulation by the miRNAs. Results: Gene and protein expression levels of VEGFA were down-expressed in both cell lines, HepG2 and HuH-7, transfected with miR-612 or miR-637. Transfection with miR-874 inhibitor showed an increase in VEGFA gene expression in HepG2 and HuH-7 cell lines; however, no regulation was observed on VEGFA protein expression by miR-874 inhibition. Correlation analysis between miRNAs and VEGFA protein expression showed that miR-637 and miR-874 expression present inversely correlated to VEGFA protein expression. Conclusions: VEGFA was down-regulated in response to hsa-miR-612 or hsa-miR-637 overexpression; however, the modulation of VEGFA by miR-874 was observed only at the gene expression and thus, needs further investigation.