PTGS2 and hepatocellular carcinoma: We investigated gene and protein expression levels of COX-2 and correlated these to gene expression levels of VEGF-A, VEGFR-1 (Flt-1) and VEGFR-2 (KDR), and Angiopoietin (Ang)-1, Ang-2, and their receptor Tie-2 in HCC, adjacent liver parenchyma and normal liver parenchyma.