Selective enhancement by tumor necrosis factor-alpha of vascular permeability of new blood vessels induced with agarose hydrogel-entrapped Meth-A fibrosarcoma cells

Vascularization and Improved In Vivo Survival of VEGF-Secreting Cells Microencapsulated in HEMA-MMA

Vascularization caused by encapsulated cells engineered to secrete vascular endothelial growth factor (VEGF) improved the in vivo survival of the encapsulated cells in a syngeneic mouse Matrigel plug model. Murine fibroblast cells (L929) were engineered to secrete recombinant human vascular endothelial growth factor (rhVEGF(165)). Transfected and nontransfected L929 cells were microencapsulated in a 75:25 hydroxyethyl methacrylate-methyl methacrylate (HEMA-MMA) copolymer. Capsules containing transfected cells induced vascularization in vivo at 1 and 3 weeks postimplantation. In histological sections, a significant positive correlation was seen between the number of capsules and blood vessel density for VEGF-secreting cell capsule implants. New vessels, many positively stained for smooth muscle cells and pericytes, were seen surrounding these VEGF-secreting cell capsule explants. Few vessels were seen in nontransfected L929 capsule implants. The viability of transfected and nontransfected encapsulated cells was assessed on explantation. Although the viability of all encapsulated cells decreased at both 1 and 3 weeks, encapsulated VEGF-secreting cells retained more of the viability than did encapsulated nontransfected control cells. Genetically modified cells promoted vascularization in this context and appeared to enhance the viability of the encapsulated cells, although the extent of the functional benefit was less than expected. Additional effort is required to enhance the benefit, to quantify it, and to understand further the host response to HEMA-MMA microencapsulated cells and tissue constructs, more generally.

Development of Novel DDS Technologies for Pharmacoproteomic-based Drug Discovery and Development

With the success of the Human Genome Project, the focus of life science research has shifted to the functional and structural analyses of proteins, such as proteomics and structural genomics. These novel approaches to the analysis of proteins, including newly identified ones, are expected to help in the identification and development of protein therapies for various diseases. Thus pharmacoproteomic-based drug discovery currently has a very high profile. Nevertheless, the use of bioactive proteins in the clinical setting is not straightforward because in vivo these proteins have low stability and pleiotropic action. To promote pharmacoproteomic-based drug discovery and development, we have attempted to establish a system for creating functional mutant proteins (muteins) with the desired properties and to develop a site-specific bioconjugation system for further improving their therapeutic potency. These innovative protein-drug systems are discussed in this review.

[DDS and Me]

With the success of the human genome project, the focus of life science research has shifted to the functional and structural analyses of proteins, such as proteomics and structural genomics. These analyses of proteins including newly identified proteins are expected to contribute to the identification of therapeutically applicable proteins for various diseases. Thus, pharmaco-proteomic-based drug discovery and development for protein therapies, including gene therapy, cell therapy, and vaccine therapy, is attracting current attention. However, there is clinical difficulty in using almost all bioactive proteins, because of their very low stability and pleiotropic actions in vivo. To promote pharmaco-proteomic-based drug discovery and development, we have attempted to develop drug delivery systems (DDSs), such as the protein-drug innovation system and the optimal cell therapeutic system. In this review, we introduce our original DDSs.

Immunotherapy of tumors with vaccine based on quail homologous vascular endothelial growth factor receptor-2

The breaking of immune tolerance of "self-antigens" associated with angiogenesis is an attractive approach to cancer therapy by active immunity. We used vascular endothelial growth factor receptor-2 (VEGFR-2) as a model antigen to explore the feasibility of the immunotherapy with a vaccine based on a xenogeneic homologous protein. To test this concept, we prepared a quail homologous VEGFR-2 protein vaccine (qVEGFR) based on quail VEGFR-2. At the same time, a protein vaccine based on the corresponding ligand-binding domain of mouse self-VEGFR-2 (mVEGFR) was also prepared and used as a control. We found that immunotherapy with qVEGFR was effective at protective and therapeutic antitumor immunity in several solid and hematopoietic tumor models in mice. Autoantibodies against mouse VEGFR-2 (Flk-1) were identified by Western blot analysis and enzyme-linked immunosorbent assay (ELISA). Anti-VEGFR antibody-producing B cells were detectable by ELISPOT. Endothelial deposition of immunoglobulins developed within tumor. VEGF-mediated endothelial cell proliferation was inhibited in vitro by immunoglobulins from qVEGFR-immunized mice. Antitumor activity was caused by the adoptive transfer of the purified immunoglobulins. Antitumor activity and production of autoantibodies against Flk-1 could be abrogated by the depletion of CD4+ T lymphocytes. Angiogenesis was apparently inhibited within the tumors, and the vascularization of alginate beads was also reduced. No marked toxicity was found in the immunized mice. The observations may provide a vaccine strategy for cancer therapy through the induction of autoimmunity against the growth factor receptor associated with angiogenesis in a cross-reaction with single xenogeneic homologous protein.

Site-specific PEGylation of a lysine-deficient TNF-alpha with full bioactivity

Addition of polyethylene glycol to protein (PEGylation) to improve stability and other characteristics is mostly nonspecific and may occur at all lysine residues, some of which may be within or near an active site. Resultant PEGylated proteins are heterogeneous and can show markedly lower bioactivity. We attempted to develop a strategy for site-specific mono-PEGylation using tumor necrosis factor-alpha (TNF-alpha). We prepared phage libraries expressing TNF-alpha mutants in which all the lysine residues were replaced with other amino acids. A fully bioactive lysine-deficient mutant TNF-alpha (mTNF-alpha-Lys(-)) was isolated by panning against TNF-alpha-neutralizing antibody despite reports that some lysine residues were essential for its bioactivity. mTNF-alpha-Lys(-) was site-specifically mono-PEGylated at its N terminus. This mono-PEGylated mTNF-alpha-Lys(-), with superior molecular uniformity, showed higher bioactivity in vitro and greater antitumor therapeutic potency than randomly mono-PEGylated wild-type TNF-alpha. These results suggest the usefulness of the phage display system for creating functional mutant proteins and of our site-specific PEGylation approach.

Tumor necrosis factor alpha-gene therapy for an established murine melanoma using RGD (Arg-Gly-Asp) fiber-mutant adenovirus vectors

Although adenovirus vectors (Ad) provide high-level transduction efficacy to many cell types, extremely high doses of Ad are required for sufficient gene transduction into several tumors, including melanoma. Here, we demonstrated that the expression of coxsackie-adenovirus receptor, a primitive Ad-receptor, was very low in murine and human melanoma cells. We also found that fiber-mutant Ad containing the Arg-Gly-Asp (RGD) sequence in the fiber knob remarkably augmented gene transduction efficacy in melanoma cells by targeting alpha(v)-integrins. In addition, intratumoral injection of RGD fiber-mutant Ad containing the tumor necrosis factor alpha gene (Ad-RGD-TNFalpha) revealed dramatic anti-tumor efficacy through hemolytic necrosis in an established murine B16 BL6 melanoma model. Ad-RGD-TNFalpha required one-tenth the dosage of Ad-TNFalpha to induce an equal therapeutic effect. These results suggest that alpha(v)-integrin-targeted Ad will be a very powerful tool for the advancement of melanoma gene therapy.

Fiber-mutant technique can augment gene transduction efficacy and anti-tumor effects against established murine melanoma by cytokine-gene therapy using adenovirus vectors

Melanoma cells are relatively resistant to adenovirus vector (Ad)-mediated gene transfer due to the low expression of Coxsackie-adenovirus receptor (CAR), which acts as a primitive Ad-receptor. Therefore, extremely high doses of Ad are required for effective gene therapy against melanoma. In the present study, we investigated whether fiber-mutant Ad containing the Arg-Gly-Asp (RGD) sequence in the fiber knob could promote gene delivery and anti-tumor effects in the murine B16 BL6 tumor model. B16 BL6 cells (in vitro) and tumors (in vivo) infected with RGD fiber-mutant Ad containing a tumor necrosis factor alpha gene (Ad-RGD-TNFalpha) produced more TNFalpha than those infected with conventional Ad-TNFalpha. In addition, Ad-RGD-TNFalpha required about one-tenth the dosage of Ad-TNFalpha for induction of equal therapeutic effects upon intratumoral injection into established B16 BL6 tumors. Furthermore, the combination of both TNFalpha- and interleukin 12-expressing RGD fiber-mutant Ads exhibited more effective tumor regression than the Ad expressing each alone. These results suggested that the fiber-mutant for altering Ad-tropism is a very potent technology for advancing gene therapy for melanoma.

In vivo anti-tumor efficacy of polyethylene glycol-modified tumor necrosis factor-alpha against tumor necrosis factor-resistant tumors

We previously reported that the optimally PEGylated tumor necrosis factor-alpha (MPEG-TNF-alpha), in which 56% of the TNF-alpha-lysine amino groups were coupled with polyethylene glycol (PEG), had about 100-fold greater anti-tumor effect than native TNF-alpha. Here, we assessed the usefulness of MPEG-TNF-alpha as a systemic anti-tumor therapeutic drug, using B16-BL6 melanoma and colon-26 adenocarcinoma, which have been reported to be resistant to TNF-alpha in vivo, as compared with Meth-A fibrosarcoma. MPEG-TNF-alpha markedly inhibited the growth of both tumors without causing any TNF-alpha-mediated side-effects, whereas native TNF-alpha had no anti-tumor effects and caused adverse side-effects. In addition, MPEG-TNF-alpha drastically inhibited the metastatic colony formation of B16-BL6 melanoma. MPEG-TNF-alpha may, thus, be a potential systemic anti-tumor therapeutic agent.

Evaluation of angiogenic inhibitors with an in vivo quantitative angiogenesis method using agarose microencapsulation and mouse hemoglobin enzyme-linked immunosorbent assay

In the present work, using a previously reported in vivo quantitative tumor-angiogenesis model, we attempted to ascertain whether this animal model is suitable for practical use in monitoring inhibitors of tumor angiogenesis. Mouse sarcoma-180 cells, human A431 cells or rat C6 cells microencapsulated in agarose beads were implanted s.c. into C57BL/6 mice. The level of blood vessel induction at the agarose pellet site was evaluated using mouse hemoglobin enzyme-linked immunosorbent assay on day 10 after implantation. Hydrocortisone, tetrahydro-S, medroxyprogesterone acetate, pentosan polysulfate and suramin inhibited blood vessel growth in our in vivo tumor-angiogenesis assay system, and heparin enhanced the antiangiogenic effects of hydrocortisone and tetrahydro-S. These results are almost entirely consistent with those observed in common assay systems, and suggest that this method may be useful for the identification and quantitative evaluation of inhibitors of tumor angiogenesis.