Novel mutein of tumor necrosis factor alpha (F4614) with reduced hypotensive effect

Receptor Specificity Engineering of TNF Superfamily Ligands

The tumor necrosis factor (TNF) ligand family has nine ligands that show promiscuity in binding multiple receptors. As different receptors transduce into diverse pathways, the study on the functional role of natural ligands is very complex. In this review, we discuss the TNF ligands engineering for receptor specificity and summarize the performance of the ligand variants in vivo and in vitro. Those variants have an increased binding affinity to specific receptors to enhance the cell signal conduction and have reduced side effects due to a lowered binding to untargeted receptors. Refining receptor specificity is a promising research strategy for improving the application of multi-receptor ligands. Further, the settled variants also provide experimental guidance for engineering receptor specificity on other proteins with multiple receptors.

Integrin targeted delivery of chemotherapeutics

Targeted delivery of chemotherapeutics is defined in the sense, that is, to maximize the therapeutic index of a chemotherapeutic agent by strictly localizing its pharmacological activity to the site or tissue of action. Integrins are a family of heterodimeric transmembrane glycoproteins involved in a wide range of cell-to-extracellular matrix (ECM) and cell-to-cell interactions. As cell surface receptors, integrins readily interact with extracellular ligands and play a vital role in angiogenesis, leukocytes function and tumor development, which sets up integrins as an excellent target for chemotherapy treatment. The peptide ligands containing the arginine-glycine-aspartic acid (RGD), which displays a strong binding affinity and selectivity to integrins, particularly to integrin αvβ3, have been developed to conjugate with various conventional chemotherapeutic agents, such as small molecules, peptides and proteins, and nanoparticle-carried drugs for integtrin targeted therapeutic studies. This review highlights the recent advances in integrin targeted delivery of chemotherapeutic agents with emphasis on target of integrin αvβ3, and describes the considerations for the design of the diverse RGD peptide-chemotherapeutics conjugates and their major applications.

RGD-based strategies for selective delivery of therapeutics and imaging agents to the tumour vasculature

During the past decade, RGD-peptides have become a popular tool for the targeting of drugs and imaging agents to alphavbeta3-integrin expressing tumour vasculature. RGD-peptides have been introduced by recombinant means into therapeutic proteins and viruses. Chemical means have been applied to couple RGD-peptides and RGD-mimetics to liposomes, polymers, peptides, small molecule drugs and radiotracers. Some of these products show impressive results in preclinical animal models and a RGD targeted radiotracer has already successfully been tested in humans for the visualization of alphavbeta3-integrin, which demonstrates the feasibility of this approach. This review will summarize the structural requirements for RGD-peptides and RGD-mimetics as ligands for alphavbeta3. We will show how they have been introduced in the various types of constructs by chemical and recombinant techniques. The importance of multivalent RGD-constructs for high affinity binding and internalization will be highlighted. Furthermore the in vitro and in vivo efficacy of RGD-targeted therapeutics and diagnostics reported in recent years will be reviewed.

Human tumor necrosis factor-alpha mutant RGD-V29 (F4614) shows potent antitumor activity and reduced toxicity against human tumor xenografted nude mice

The antitumor effects of human tumor necrosis factor-alpha (TNF) mutant RGD-V29 (code no. F4614), that includes the cell adhesive sequence (4)Arg-(5)Gly-(6)Asp and (29)Arg-->Val substitution, were evaluated. The therapeutic index, a measure of the extent of the therapeutically-effective range, using three constitutive administrations of RGD-V29 in Meth A-bearing mice was 4.8, whereas that of recombinant human TNF (rhTNF) ((1)SSS(4)RTPSDK...(29)RR...(155)L) was 2.8, clearly indicating that the effective RGD-V29 dose-range was extended. Furthermore, RGD-V29 showed potent antitumor activity against human lung cancer Mqnu-1 xenografted nude mice without severe gastrointestinal and other organ toxicities, even when administered at the maximal tolerated dose (MTD). In contrast, rhTNF induced severe toxicity at the MTD. Direct cytotoxicity of RGD-V29 against Mqnu-1 cells was similar to that of rhTNF. In addition, a cytotoxicity assay using a tumor-derived endothelial-like cell (tEC)/normal endothelial cell (nEC) system used to study TNF antitumor effects on tumor-associated endothelial cells, suggested that RGD-V29 showed preferential cytotoxicity toward tumor-associated endothelial cells compared with rhTNF. Thus, RGD-V29 appears to be a low-toxicity mutant of rhTNF that shows preferential activity towards tumors, and therefore merits further investigation in pre-clinical and clinical studies.

Preferential activity of wild-type and mutant tumor necrosis factor-alpha against tumor-derived endothelial-like cells

Tumor-derived endothelial-like cells (tEC) were prepared by culturing human umbilical vein endothelial cells (HUVEC) in the presence of HT1080 human fibrosarcoma-conditioned medium. tEC showed higher permeability and less cell-adhesion activity than normal HUVEC (nEC). Tumor necrosis factor-alpha (TNF) is known to have tumor-vasculature disrupting activity. tEC showed higher cytotoxicity to recombinant human TNF (rhTNF) than nEC, and was not observed using HUVEC cultured with WI38 human diploid cell-conditioned medium as a medium-control. These results demonstrate that tEC acquire physiological properties of tumor-associated vasculature, and may be a useful model system for the study of the mechanisms of TNF antitumor action. The TNF-mutant RGD-V29 (code No. F4614), which has an inserted 4Arg-Gly-Asp sequence and an 29Arg-->Val replacement, was found to induce greater preferential destruction of tEC compared to rhTNF. When the preferential activities were evaluated in terms of 30% cytotoxicity (IC30) ratio (nEC/tEC), the ratio was 460 for RGD-V29 compared to 4.2 for rhTNF. RGD-V29 also exhibited cell-adhesive function and bound preferentially to the p55 TNF-receptor. Both these properties of RGD-V29 contributed to the tEC selective cytotoxicity, indicating that the RGD ligands and selective p55 receptor binding on the cells, although uncharacterized, are involved in tEC targeting. Therefore, the TNF mutant RGD-V29 may show greater selectivity toward tumor vasculature than wild-type TNF.

A novel human tumor necrosis factor alfa mutein, F4614, inhibits in vitro and in vivo growth of murine and human hepatoma: implication for immunotherapy of human hepatocellular carcinoma

Although treatment for hepatocellular carcinoma (HCC) has recently improved, most patients still relapse and die from this disease. The development of new therapeutic and preventive strategies for HCC is, therefore, required. A novel mutant protein (mutein) of human tumor necrosis factor alfa (TNF-alpha mutein F4614, 1SSSRGDSD... 29V ... 155L) was developed to decrease several adverse effects of TNF-alpha. F4614 is known to lack hypotensive effects of human TNF-alpha without losing its anti-tumor effect in mice transplanted with Meth-A sarcoma. Our study investigated the anti-tumor effects of F4614 against hepatoma cells in vitro and in vivo. F4614 significantly inhibited growth of all four tumor cells in vitro. A murine hepatoma cell line, MH134, when incubated in the presence of F4614, exhibited upregulation of surface major histocompatibility complex (MHC) class-I, intercellular adhesion molecule-1 (ICAM-1) and B7-1 molecules, and a decreased proportion of cells in the G2/M phase of the cell cycle. In addition, F4614 induced apoptosis in a significant number of MH134 cells. TNF-alpha and F4614 (5 microg/mouse daily for 5 days) showed similar anti-tumor activities in syngeneic MH134-bearing mice and heterogeneic PLC/PRF/5-bearing athymic nude mice. Intratumoral injection of F4614 or TNF-alpha was more effective than intravenous injection. Immunohistochemical analysis of the tumors treated by F4614 revealed that tumors were surrounded with a large number of Mac-1+ cells and a small number of CD4+ and CD8+ T cells; that suggests that intratumoral injection of F4614 elicited host immunoreactions. Thus, F4614 may be a new strategy for immunotherapy of HCC.