Synergistic effect of basic fibroblast growth factor and vascular endothelial growth factor in murine hepatocellular carcinoma

Halting the interaction between vascular endothelial growth factor and its receptors attenuates liver carcinogenesis in mice

It has been shown that angiogenesis plays an important role not only in tumor growth, but also in early carcinogenesis. The expression of a potent angiogenic factor, vascular endothelial growth factor (VEGF), increased during the early stage of carcinogenesis. In this study, the effects of the neutralizing monoclonal antibodies R1 mAb and R2 mAb of the VEGF receptors Flt-1 (VEGFR-1) and KDR/Flk-1 (VEGFR-2), respectively, on murine hepatocarcinogenesis induced by diethylnitrosamine (DEN) were examined. The effects of R1 mAb and R2 mAb on spontaneous lung metastasis from hepatocellular carcinoma (HCC) were also investigated. VEGF expression and neovascularization in the tumor increased stepwise during hepatocarcinogenesis. Treatment with both R1 mAb and R2 mAb markedly inhibited the development of HCC and adenoma in the liver. The inhibitory effect of R2 mAb was more potent than that of R1 mAb, and the combination treatment with both mAbs almost completely attenuated hepatocarcinogenesis. Both R1 mAb and R2 mAb treatment significantly suppressed the development of angiogenesis in HCC. The suppressive effects against angiogenesis R1 mAb and R2 mAb were similar in magnitude to their inhibitory effects against hepatocarcinogenesis. Furthermore, spontaneous lung metastasis from HCC was also significantly suppressed by R1 mAb and R2 mAb treatment. In conclusion, these results suggest that VEGF and receptor interaction plays an important role in hepatocarcinogenesis and in spontaneous lung metastasis from HCC.

Angiogenesis in hepatocellular carcinoma: the retrospectives and perspectives

Hepatocellular carcinoma (HCC) is a typical hypervascular tumor. Many angiogenic factors have been studied in HCC, and several anti-angiogenic therapies have been tested in animal models and patients. This paper summarizes the latest findings, especially regarding the clinical significance of endothelial cell markers and angiogenic factors in HCC, and experimental and clinical anti-angiogenesis therapies. Further developments in this area, such as endothelial cell-oriented research and better experimental and clinical designs in the evaluation of anti-angiogenic therapies are discussed.

Perlecan and tumor angiogenesis

Perlecan is a major heparan sulfate proteoglycan (HSPG) of basement membranes (BMs) and connective tissues. The core protein of perlecan is divided into five domains based on sequence homology to other known proteins. Commonly, the N-terminal domain I of mammalian perlecan is substituted with three HS chains that can bind a number of matrix molecules, cytokines, and growth factors. Perlecan is essential for metazoan life, as shown by genetic manipulations of nematodes, insects, and mice. There are also known human mutations that can be lethal. In vertebrates, new functions of perlecan emerged with the acquisition of a closed vascular system and skeletal connective tissues. Many of perlecan's functions may be related to the binding and presentation of growth factors to high-affinity tyrosine kinase (TK) receptors. Data are accumulating, as discussed here, that similar growth factor-mediated processes may have unwanted promoting effects on tumor cell proliferation and tumor angiogenesis. Understanding of these attributes at the molecular level may offer opportunities for therapeutic intervention.

Expression of angiogenic factors in hepatocellular carcinoma after transcatheter arterial chemoembolization

In order to investigate the changes of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) expression in residual hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE), the expression levels of VEGF and bFGF expression in specimens surgically removed from 48 HCC patients were detected by immunohistochemical methods, and staining intensity of VEGF and bFGF was assessed by a computer-assisted image-analyzer. Among the 48 patients, 25 underwent partial hepatectomy alone (single operating group), and 23 were subjected to second stage surgical resection after TACE (TACE group). The results showed that the average absorbance value (A) of VEGF was higher in TACE group than that in single operating group (0.152 +/- 0.021 vs 0.131 +/- 0.012, P < 0.01). The Average A of bF-GF in TACE group was 0.127 +/- 0.023, higher than in single operating group (0.111 +/- 0.016, P < 0.05). These results suggested that TACE of HCC can up-regulate the expression of VEGF and bFGF in HCC tissues possibly due to anoxia and ischemia.

Vascular endothelial growth factor synthesis by human omental mesothelial cells is augmented by fibroblast growth factor-2: possible role of mesothelial cell on the development of peritoneal metastasis

Although peritoneal metastasis is an important factor determining the prognosis of patients with gastrointestinal cancer, the mechanisms have not yet been clearly defined. Human peritoneal mesothelial cells (HPMC) are the first line against disseminated tumor cells. Recent reports have shown that mesothelial cells are capable of secreting various cytokines and growth factors. In this study, we isolated human mesothelial cells from surgically resected omental tissue and examined the production and interaction of two major angiogenic factors, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2). Quiescent HPMC produced a considerable amount of VEGF at almost the same level as tumor cells. Interestingly, addition of FGF-2 to the culture significantly increased the mRNA synthesis and protein secretion of VEGF in a dose-dependent manner, as determined by Northern blot and ELISA. The addition of 0.5 ng/mL FGF-2 was enough to stimulate VEGF production, and the effect reached a plateau at 5 ng/mL. Reverse-transcribed polymerase chain reaction (RT-PCR) method clarified that the HPMC-derived VEGF consisted mostly of VEGF(121) and VEGF(165), which are both predominantly soluble forms. These data suggest that HPMC contribute to the development of metastases and the accumulation of malignant ascites due to the production of VEGF, especially in cancers that do not express enough amount of VEGF.

Mechanism and its regulation of tumor-induced angiogenesis

Tumor angiogenesis is the proliferation of a network of blood vessels that penetrates into cancerous growths, supplying nutrients and oxygen and removing waste products. The process of angiogenesis plays an important role in many physiological and pathological conditions. Solid tumors depend on angiogenesis for growth and metastasis in a hostile environment. In the prevascular phase, the tumor is rarely larger than 2 to 3 mm³ and may contain a million or more cells. Up to this size, tumor cells can obtain the necessary oxygen and nutrient supplies required for growth and survival by simple passive diffusion. The properties of tumors to release and induce several angiogenic and anti-angiogenic factors which play crucial roles in regulating endothelial cell (EC) proliferation, migration, apoptosis or survival, cell-cell and cell-matrix adhesion through different intracellular signaling are thought to be the essential mechanisms during tumor-induced angiogenesis. Tumor angiogenesis actually starts with tumor cells releasing molecules that send signals to surrounding normal host tissue. This signaling activates certain genes in the host tissue that, in turn, make proteins to encourage growth of new blood vessels. In this review, we focus the mechanisms of tumor-induced angiogenesis, with an emphasis on the regulatory role of several angiogenic and anti-angiogenic agents during the angiogenic process in tumors. Advances in understanding the mechanisms of tumor angiogenesis have led to the development of several most effective anti-angiogenic and anti-metastatic therapeutic agents and also have provided several techniques for the regulation of cancer's angiogenic switch. The suggestion is made that standard cytotoxic chemotherapy and angiogenesis inhibitors used in combination may produce complementary therapeutic benefits in the treatment of cancer.

Distinct role of fibroblast growth factor-2 and vascular endothelial growth factor on tumor growth and angiogenesis

Tumors express more than a single angiogenic growth factor. To investigate the relative impact of fibroblast growth factor-2 (FGF-2) and vascular endothelial growth factor (VEGF) on tumor growth and neovascularization, we generated tumor cell transfectants differing for VEGF and/or FGF-2 expression. Human endometrial adenocarcinoma HEC-1-B-derived Tet-FGF-2 cells that express FGF-2 under the control of the tetracycline-responsive promoter (Tet-off system) were further transfected with a VEGF(121) anti-sense (AS-VEGF) cDNA. Next, Tet-FGF-2 and AS-VEGF/Tet-FGF-2 cells were transplanted subcutaneously in nude mice that received tetracycline or not in the drinking water. Simultaneous expression of FGF-2 and VEGF in Tet-FGF-2 cells resulted in fast-growing lesions characterized by high blood vessel density, patency and permeability, and limited necrosis. Blood vessels were highly heterogeneous in size and frequently associated with pericytes. Inhibition of FGF-2 production by tetracycline caused a significant decrease in tumor burden paralleled by a decrease in blood vessel density and size. AS-VEGF expression resulted in a similar reduction in blood vessel density associated with a significant decrease in pericyte organization, vascular patency, and permeability. The consequent decrease in tumor burden was paralleled by increased tumor hypoxia and necrosis. A limited additional inhibitory effect was exerted by simultaneous down-regulation of FGF-2 and VEGF expression. These findings demonstrate that FGF-2 and VEGF stimulate vascularization synergistically but with distinctive effects on vessel functionality and tumor survival. Blockade of either one of the two growth factors results in a decrease in blood vessel density and, consequently, in tumor burden. However, inhibition of the expression of VEGF, but not of FGF-2, affects also vessel maturation and functionality, leading to tumor hypoxia and necrosis. Our experimental model represents an unique tool to investigate anti-neoplastic therapies in different angiogenic environments.

Antiangiogenic gene therapy for hepatocellular carcinoma using angiostatin gene

Recent studies have reported that antiangiogenic gene delivery into cancer cells inhibits growth of certain tumors in vivo. Hepatocellular carcinoma (HCC) is a hypervascular cancer, and antiangiogenic gene therapy might be suitable for HCC. In the present study, we investigated the antiangiogenic effects of angiostatin gene transduction into HCC both in vitro and in vivo. Angiostatin gene was cloned into a pSecTag2B mammalian expression vector to construct pSecTag2B-ANG. pSecTag2B or pSecTag2B-ANG were transfected into an HCC cell line, PLC/PRF/5, and then stable transfectants were obtained by Zeocin selection. pSecTag2B or pSecTag2B-ANG transfection did not alter the expression of vascular endothelial growth factor (VEGF), a potent angiogenic stimulator, or pigment epithelium-derived factor (PEDF), an angiogenic inhibitor, in PLC/PRF/5 cells. However, conditioned media (CM) derived from pSecTag2B-ANG-transfected PLC/PRF/5 cells (CM-ANG) suppressed the proliferation and migration of human umbilical vein endothelial cells (HUVEC) by 35% and 50%, respectively, relative to their effects on nontransfected cells. In in vivo experiments, pSecTag2B-ANG stable transfected (CM-Mock) and nontransfected cells (CM-N) were mixed at various proportions and the mixed cells were subcutaneously implanted into athymic mice. Suppression of tumor growth was noted in mice implanted with angiostatin gene-transfected cells, and such suppression was proportional with the percentage of transfected cells. Analysis of the vascular density in these tumors showed that the tumor growth suppression effect of angiostatin gene correlated with suppression of tumor vascularity. In conclusion, antiangiogenic gene therapy using angiostatin gene is potentially suitable for the treatment of patients with HCC.