Kwang Hoe Chung

Estrogen release from metallic stent surface for the prevention of restenosis.

For the prevention of coronary restenosis, estrogen was coupled onto a metallic stent and in vitro release of estrogen was investigated. Estrogen was introduced to the metal surface using a hydrolysable covalent bond for local sustained delivery of drug as follows: (i) the stainless steel (SS) surface was activated with silane by plasma polymerization, (ii) the activated surface (SS-Si surface) was treated with acrylic acid by plasma polymerization (SS-Si-AAc surface), and (iii) 17beta-estradiol (E2) was covalently linked to the carboxyl group on that surface (SS-Si-AAc-E2 surface). The modified surfaces were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and water contact angle measurement. The amount of E2 was measured by UV-visible spectrophotometry and high performance liquid chromatography (HPLC). The in vitro release profile of E2 demonstrated sustained release of E2 in aqueous buffer. In summary, a novel method of immobilizing estrogen onto a metallic stent surface using plasma polymerization has been developed. The obtained results attest to the usefulness of the estrogen-releasing stent for preventing restenosis.

Inhibition of angiogenesis and tumor progression by hydrodynamic cotransfection of angiostatin K1-3, endostatin, and saxatilin genes

In vivo expression of angiostatin and endostatin, two different types of endothelial cell growth inhibitor, have been reported to inhibit vascularization in tumor tissues, resulting in tumor growth inhibition. Recently, in vivo expression of saxatilin, a novel disintegrin purified from snake (Gloydius saxatilis) venom, was able to strongly inhibit endothelial cell proliferation and smooth muscle cell migration, resulting in tumor growth inhibition. However, the antitumor efficacy of the individual antiangiogenic molecules expressed in vivo was not sufficiently potent to induce tumor regression in animal models. Therefore, in this study, we have systemically examined how combinational transfer of angiostatin, endostatin, and saxatilin genes affects neovascularization in tumor tissues and tumor progression in a mouse model. In Matrigel-implanted mice, cotransfection with plasmids encoding angiostatin K1-3 (pFLAG-Angio K1/3), endostatin (pFLAG-Endo), and saxatilin (pFLAG-Sax) resulted in the most effective inhibition of angiogenesis. In addition, hydrodynamic cotransfection of the three genes induced more inhibition of B16BL6 melanoma growth and pulmonary metastasis than other combinations of transfected genes. Compared with the empty vector-treated control group, cotreatment with the three plasmids reduced B16BL6 tumor growth by 89% and pulmonary metastasis by 90%. These results provide additional evidence supporting the combined systemic expression of antiangiogenic factors, such as angiostatin K1-3, endostatin, and saxatilin, as an alternative procedure for antiangiogenic cancer therapy.

Inhibitory effect of salmosin, a Korean snake venomderived disintegrin, on the integrin αv-mediated proliferation of SK-Mel-2 human melanoma cells

We have investigated the inhibitory effect of salmosin on integrin‐mediated human tumour cell proliferation. SK‐Mel‐2 human melanoma cell adhesion to denatured collagen or vitronectin was found to be significantly and statistically inhibited by salmosin in a dose‐dependent manner (P < 0.05). Moreover, the binding of SK‐Mel‐2 cells to salmosin‐coated plates was specifically disrupted by anti‐integrin αv monoclonal antibody at 8αg mL−1, but not by anti‐integrin monoclonal antibody. These findings indicated that salmosin inhibited the adhesion of SK‐Mel‐2 cells to denatured collagen by specifically blocking integrin αv. The proliferation of SK‐Mel‐2 cells on a denatured collagen‐coated plate was statistically and significantly inhibited by salmosin induced apoptosis in a dose‐dependent manner (P < 0.05). Anti‐integrin αv monoclonal antibody, anti‐integrin αvβ3 monoclonal antibody, and synthetic RGD peptide also suppressed SK‐Mel‐2 cell proliferation. Several lines of experimental evidence strongly suggested that the inhibition of SK‐Mel‐2 cell proliferation by salmosin was due to the induction of apoptosis via the blocking of integrin αv‐mediated cell survival.

Inhibition of angiogenesis by salmosin expressed in vitro.

Recently, salmosin, a novel snake venom-derived disintegrin containing the Arg-Gly-Asp (RGD) sequence, was reported to be both antiangiogenic and antitumorigenic. The antitumor activity was substantiated by in vivo administration of recombinant salmosin into mice bearing tumors. However, it was difficult to prepare functionally active recombinant salmosin and to maintain a therapeutically effective concentration of the protein in the circulatory system by daily injections. Hence, we have suggested that salmosin gene transfer mediated by cationic liposomes may be a practical alternative for cancer treatment. Plasmids encoding the salmosin gene were constructed and then transferred by means of cationic liposomes into transformed human embryonic kidney (HEK) 293 cells. The transfected genes were able to produce functionally active salmosin proteins in vitro. In fact, the expressed salmosin remarkably inhibited proliferation of bovine capillary endothelial (BCE) cells and effectively inhibited the migration of highly metastatic B16BL6 mouse melanoma cells. Neovascularization in chick chorio-allantoic membranes (CAM) and in Matrigel implanted subcutaneously into mice was greatly inhibited in the presence of the expressed salmosin. Based on these experimental results, we suggest that the antitumor effect induced by salmosin gene transfection may be due to the antiangiogenic activity of the expressed salmosin proteins.