TFF3 and FXII were knocked down by short interfering RNA (siRNA) in WT and Alb/AEG-1 Selleckchem INK 128 hepatocytes (Supporting Fig. 7), and the CM were subjected to HUVEC differentiation and CAM assays. Although control siRNA did not affect angiogenesis induced by CM from Alb/AEG-1 hepatocytes, inhibition of either TFF3 or FXII resulted in marked inhibition of angiogenesis (Fig. 6A,B). It should be noted that although inhibition of either TFF3 or FXII abrogated

sprouting of small vessels in a similar magnitude, knocking down FXII exhibited more-pronounced inhibition in the growth of larger blood vessels, suggesting a pivotal role of FXII in mediating AEG-1-induced angiogenesis. FXII cross-talks with epidermal growth factor receptor (EGFR), activating MAPK and Akt signaling to promote proliferation and differentiation of endothelial cells (ECs). We treated HUVECs with CM

from Alb/AEG-1 hepatocytes transfected with either control siRNA or FXII siRNA. Although CM from control siRNA-treated HUVECs maintained activation of EGFR, Akt, ERK, and p38 MAPK, the absence of FXII in the CM form FXII knock-down cells significantly Bortezomib purchase abrogated the activation of EGFR, Akt, ERK, and p38 MAPK in HUVECs (Fig. 6C). These findings further support that FXII plays an important role in AEG-1-induced proliferation and differentiation of ECs. We analyzed FXII mRNA level in WT and Alb/AEG-1 hepatocytes and observed only modest changes (data not shown), indicating that AEG-1 may preferentially increase FXII at the protein level. In WT hepatocytes, AEG-1 is expressed at low levels and is predominantly localized in the nucleus (Fig. 7A). In contrast, in Alb/AEG-1 hepatocytes, AEG-1 is almost exclusively contained in the cytoplasm (Fig. 7A). We hypothesized that cytoplasmic AEG-1 might augment the translation of FXII mRNA by facilitating its association with polysomes. Polysomal fractions were collected from WT

and Alb/AEG-1 hepatocytes, RNA was extracted from each fraction, and an equal amount of RNA from each fraction was subjected PI-1840 to complementary DNA synthesis and Taqman real-time PCR for FXII. The mean cycle threshold (Ct) value for FXII amplification was significantly lower in Alb/AEG-1 hepatocytes, compared to WT hepatocytes, indicating that AEG-1 preferentially helps FXII mRNA associate with polysomes and thereby facilitates translation (Fig. 7B). In addition to increased polysomal association of FXII mRNA, miRNA-mediated regulation might also be involved in the increased protein level of FXII. One known miRNA-targeting FXII mRNA is miR-181a.16 We analyzed the expression levels of mature miR-181a in WT and Alb/AEG-1 hepatocytes and did not observe any difference (Supporting Fig. 8). Thus, miRNA-mediated regulation might not be a major mechanism of FXII induction by AEG-1.