Regional Suppression of Tumor Growth byIn VivoTransfer of a cDNA Encoding a Secreted Form of the Extracellular Domain of theflt-1Vascular Endothelial Growth Factor Receptor

Abstract

Vascular endothelial growth factor (VEGF), a potent angiogenic mediator, is overexpressed in most solid tumors. On the basis of the knowledge that solid tumor growth beyond a small volume is critically dependent on angiogenesis, and that adenovirus (Ad) vectors can mediate efficient in vivo gene transfer and expression, we hypothesized that Ad-mediated transfer of a secreted form of the extracellular domain of the flt-1 VEGF receptor (Adsflt) would suppress tumor growth on a regional basis. To evaluate this concept, three tumor models were examined using a murine colon carcinoma cell line and syngeneic BALB/c mice. First, mice with preestablished splenic CT26.CL25 tumors and liver metastases were given Adsflt on AdNull intravenously and, after 15 days, spleens and livers were harvested to quantify tumor burden. Adslft-treated animals had minimal residual splenic tumors and liver metastases; in contrast, control animals had bulky splenic tumors and extensive liver metastases (p < 0.003). Second, mice with preestablished lung metastases showed a significant reduction in pulmonary metastases with regionally administered Adslft (intratracheal, p < 0.02) but not when the vector was systemically administered (intravenous, p > 0.9). Finally, mice with primary subcutaneous tumors treated with intratumoral administration of Adslft showed significant tumor suppression (p < 0.05) not observed in AdNull-treated mice or mice given Adslft intravenously (p > 0.3). We conclude that Ad-mediated in vivo regional delivery of a secreted form of the extracellular domain of the flt-1 VEGF receptor can effectively inhibit regional tumor growth, a strategy that may provide a means to control tumor growth within the treated organ without the risk of systemic antiangiogenesis.

Potential long-term inhibition of ocular neovascularisation by recombinant adeno-associated virus-mediated secretion gene therapy

“…Treatment with sFlt-1, a naturally-occurring truncated and secreted form of VEGF receptor Flt-1, has been shown to inhibit angiogenesis in a variety of disease models. 29,30,35 The anti-angiogenic action of sFlt-1 is due to its ability to directly sequester VEGF and to form heterodimers with membrane-bound Flt-1 and VEGF receptor 2. 28,36 It is widely believed that VEGF up-regulation also plays a major part in the development of ocular NV.…”

“…Both models have been shown to induce VEGF expression resulting in extensive blood vessel growth in the normally avascular cornea and subretinal space, respectively. 22,26,27 Based upon the proven efficacy of soluble VEGF receptor 1, sFlt-1, as a potent anti-angiogenic agent, [28][29][30] we selected sFlt-1 as our therapeutic gene and investigated the efficacy of AAV-mediated delivery and expression of this protein as SGT against global corneal NV and choroidal NV.…”

Gene therapy targeting to tumor endothelium

“…Examples include TIMP-3, 78 angiostatin, endostatin, 79 platelet factor-4, 80 thrombospondin-1, 81 soluble extracellular domains of growth factor receptors such as Flt-1 82 and FGF-R 83, including fusion proteins containing the Fc portion of antibodies such as Flk1-Fc, 79 sNeuropilin-1-Fc, 84 and intrabodies that block Tie-2 receptor surface expression. 85 All these anti-tumour angiogenesis strategies using adenovirus as a vector showed a significant reduction in tumor angiogenesis and tumor growth, except for endostatin and angiostatin.…”

Antiangiogenic gene therapy with systemically administered sFlt-1 plasmid DNA in engineered gelatin-based nanovectors

“…[8][9][10][11] Successful use of adenoviral vector for sFlt-1-expressing plasmid DNA delivery to tumorbearing animals has already been reported in a number of publications. [12][13][14][15] For systemic gene delivery to tumor mass, viral and non-viral vectors have been used. Although viral vectors are efficient, they have been plagued with serious toxicity concerns.…”