[Synergistic apoptotic effect of the combination of diosgenin and TRAIL on non-small-cell lung cancer cell line A549 evaluated with the Chou-Talalay method].

This study is to investigate the apoptotic induction effect of the combination of diosgenin and TNF-related apoptosis-inducing ligand (TRAIL) on non-small-cell lung cancer cell line A549 by using the Chou-Talalay method, and observe the mechanism of the combination. The apoptotic effect of diosgenin or TRAIL alone and their combination on A549 and normal cell line 293T proliferation was measured by MTT assay. Chou-Talalay method was used to evaluate the combination effect. Apoptosis was examined by Hoechst 33342 staining and flow cytometry assay. Western blotting detects the expression of apoptosis-associated proteins. Diosgenin or TRAIL alone can inhibit proliferation ofA549 in a concentration-dependent manner. According to the Chou-Talalay method, when f(a) = 0.1, CI > 1, when f(a) > 0.1, CI < 1. Combined with TRAIL, the IC50 of diosgenin decreases from 21.864 to 14.810 micromol x L(-1) (P < 0.05) on A549 cells. But for 293T cells, IC50 of diosgenin does not change significantly. As with Hoechst 33342 staining and flow cytometry assay, the apoptosis ratios also increased in the combination group. At protein expression level, combination-treated group displays increased Caspase-8, Caspase-9, Bid, Caspase-3 activation and PARP cleavage, significantly decreased Bcl-2 and increased Bax expression, and MAPK pathways were activated. The combination of diosgenin and TRAIL has synergistic effect on A549 cells.

Expression, purification and characterization of C-FADD.

FADD is an important proapoptotic adaptor in death receptor-induced apoptosis. Recently, FADD has been found to participate in a variety of non-apoptotic processes, such as development, cell cycle progression and survival. Its non-apoptotic activities were regulated by the phosphorylated status of the serine residue located at the C-terminal region, a domain distinct from the proapoptotic function related DED and DD domains. However, due to the difficulties in expression and crystallization of natural FADD, by far the molecular structures of all FADD variants did not contain the C-terminal region. To elucidate the structure-function relationship of C-terminal region, we need to obtain an FADD variant that containing C-terminal region. In this study, mouse FADD (80-205) containing DD domain and C-terminal region, designated as C-FADD, was expressed in E. coli with His-tag at the N-terminus and purified by Ni2+ affinity chromatography. The purified protein existed as a homogenous monomer in glutaraldehyde cross-linking analysis and exhibited a typical alpha-helix spectrum in CD (circular dichroism) assay. In vitro His-tag pull-down assay demonstrated that the purified C-FADD possessed the CK Ialpha-binding activity which was important for its non-apoptotic function.

Enhancement of antitumor properties of TRAIL by targeted delivery to the tumor neovasculature.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a promising anticancer agent with tumor-selective apoptotic activity. TRAIL plays a role in the innate and adaptive immune response and autoimmune disease and may also be involved in hepatic cell death and inflammation. For these reasons, chronic exposure to TRAIL may have deleterious side effects in patients as a cancer therapeutic. In this study, we have improved the antitumor activity of TRAIL by targeted delivery to the tumor vasculature, leading to dramatic enhancement of its therapeutic properties. TRAIL was fused to the ACDCRGDCFC peptide (named RGD-L-TRAIL), a ligand of alpha(V)beta(3) and alpha(V)beta(5) integrins. Biological activity was evaluated in vitro and antitumor efficacy was investigated in vivo as a single agent and in combination with irinotecan hydrochloride (CPT-11). The fusion protein RGD-L-TRAIL, but not TRAIL or RGE-L-TRAIL, specifically bound to microvascular endothelial cells in a dose-dependent manner and showed enhanced apoptosis-inducing activity (caspase-3 and caspase-8 activation) in alpha(V)beta(3) and alpha(V)beta(5) integrin-positive cancer cells. In addition, RGD-L-TRAIL was more effective in suppressing tumor growth of COLO-205 tumor-bearing mice than an equivalent dose of TRAIL. The antitumor effect of RGD-L-TRAIL was further enhanced by combination with CPT-11 in both TRAIL-sensitive COLO-205 and TRAIL-resistive HT-29 tumor xenograft models. Our findings suggest that the novel fusion protein RGD-L-TRAIL can directly target tumor endothelial cells as well as alpha(V)beta(3) and alpha(V)beta(5) integrin-positive tumor cells. The tumor-targeted delivery of TRAIL derivatives, such as RGD-L-TRAIL, may prove to be a promising lead candidate for cancer therapy.

Immobilized protein ZZ, an affinity tool for immunoglobulin isolation and immunological experimentation.

At present, the common tool for affinity purification of IgG is immobilized Protein A, which is separated from native cell-wall components of Staphylococcus aureus. It is complicated and costly to prepare natural Protein A. ZZ protein is a synthetic Fc region-binding domain originated from B domain of Protein A. In the present study, recombinant ZZ protein with a hexahistidine tag at the N-terminus was expressed in BL21 (DE3) under the control of T7 promoter. The protein was purified through one-step Ni2+ chelating affinity chromatography at a yield of 50 mg of protein/litre of culture. Then it was covalently coupled with Sepharose 4B with butane-1,4-diol diglycidyl ether. The protein ZZ-Sepharose 4B resin exhibited good performance in affinity purification of IgG, as well as in capturing the protein-interacting complexes in immunoprecipitation experiments. Compared with natural Protein A, the expression and purification of ZZ protein at high yield are very simple and low-cost. At this point, extensive applications of protein ZZ in immunoassays are practicable and to be anticipated.

Application to immunoassays of the fusion protein between protein ZZ and enhanced green fluorescent protein.

Enhanced green fluorescent protein (EGFP) from Aequorea victoria was fused to the C terminal region of protein ZZ, an artificial synthetic IgG Fc fragment binding protein derived from tandem repeats of the B domain of protein A. The ZZ-EGFP fusion protein was expressed in Escherichia coli with a His(6) tag and purified in high yield by one-step Ni(2+) chelating affinity chromatography. It was then used in the immunoblot analysis of GST and TNFalpha as well as in immunofluorescent assays of 293T cells transfected with IRF3, an interferon regulatory factor which localized in cytoplasm without virus infection. The fusion protein also performed effectively in FACS analysis of surface integrin beta3 subunit on 293 T cells. The chimeric protein bound various antibodies from different animal sources, directed against a variety of proteins. Thus, ZZ-EGFP showed broad promise in potential immunological applications.

Fusion protein between protein ZZ and red fluorescent protein DsRed and its application to immunoassays.

In the present study, a red fluorescent protein (DsRed) from the coral Discosoma was fused to the C-terminus of protein ZZ, a synthetic artificial IgG-Fc-fragment-binding protein derived from the B-domain of staphylococcal Protein A. The chimaeric protein, tagged with six histidine residues at the N-terminus, was expressed in Escherichia coli and easily purified by one-step Ni2+-chelating affinity chromatography. Its fluorescence and IgG-binding activities were validated using fluorescence-spectrum analysis, ELISA and dot-blot analysis. Furthermore, in subsequent dot-blotting immunoanalysis of glutathione S-transferase and tumour necrosis factor-alpha, and immunofluorescent microscopy assay of interferon regulatory factor 3, the chimaeric protein enabled effective detection of target molecules. Compared with fluorescence-conjugated antibodies, ZZ-DsRed is less susceptible to photobleaching and easy to produce. In addition, unlike HRP (horseradish peroxidase)-conjugated antibodies, using ZZ-DsRed needs no addition of a chromogenic reagent. Our results indicate that ZZ-DsRed shows a wide and promising application potential in immunological detection as a substitute for fluorescent or HRP-conjugated anti-IgGs.

Enhanced therapeutic effect by combination of tumor-targeting Salmonella and endostatin in murine melanoma model.

The growth of tumor is angiogenesis-dependent and it often contains hypoxia and necrotic areas. Salmonella VNP20009 could target and replicate in hypoxia and necrotic areas within tumor and induce antitumor effect. Angiogenesis inhibitor endostatin could reduce tumor angiogenesis and inhibit its growth. However, in the phase I trials of VNP20009 and endostatin at the maximum-tolerated dose, no antitumor effects for bacteria therapy and minor therapeutic effects for endostatin treatment were seen. The ineffectiveness of these agents in clinical trials suggests that the combination of these agents with synergic modalities might be necessary. Here we described antitumor effects mediated by the combination of VNP20009 with recombinant human endostatin in B16F10 murine melanoma model with the aim to exploit tumor-targeting of bacteria and anti-angiogenesis strategy to enhance therapeutic efficacy. Combination therapy of these agents significantly enhanced antitumor effects by inducing greater tumor growth inhibition, more severe tumor tissue necrosis as well as less blood vessel density than those induced by either of treatments. The findings suggest that the combination of tumor-targeting bacteria with angiogenesis inhibitor might be of value for the treatment of solid tumors.