Comparison of microbial and transient expression (tobacco plants and plant-cell packs) for the production and purification of the anticancer mistletoe lectin viscumin.

Cancer is the leading cause of death in industrialized countries. Cancer therapy often involves monoclonal antibodies or small-molecule drugs, but carbohydrate-binding lectins such as mistletoe (Viscum album) viscumin offer a potential alternative treatment strategy. Viscumin is toxic in mammalian cells, ruling them out as an efficient production system, and it forms inclusion bodies in Escherichia coli such that purification requires complex and lengthy refolding steps. We therefore investigated the transient expression of viscumin in intact Nicotiana benthamiana plants and Nicotiana tabacum Bright Yellow 2 plant-cell packs (PCPs), comparing a full-length viscumin gene construct to separate constructs for the A and B chains. As determined by capillary electrophoresis the maximum yield of purified heterodimeric viscumin in N. benthamiana was ~7 mg/kg fresh biomass with the full-length construct. The yield was about 50% higher in PCPs but reduced 10-fold when coexpressing A and B chains as individual polypeptides. Using a single-step lactosyl-Sepharose affinity resin, we purified viscumin to ~54%. The absence of refolding steps resulted in estimated cost savings of more than 80% when transient expression in tobacco was compared with E. coli. Furthermore, the plant-derived product was ~3-fold more toxic than the bacterially produced counterpart. We conclude that plants offer a suitable alternative for the production of complex biopharmaceutical proteins that are toxic to mammalian cells and that form inclusion bodies in bacteria.

The heparin-binding domain of HB-EGF as an efficient cell-penetrating peptide for drug delivery.

Cell-penetrating peptides (CPPs) have been shown to be potential drug carriers for cancer therapy. The inherently low immunogenicity and cytotoxicity of human-derived CPPs make them more suitable for intracellular drug delivery compared to other delivery vehicles. In this work, the protein transduction ability of a novel CPP (termed HBP) derived from the heparin-binding domain of HB-EGF was evaluated. Our data shows, for the first time, that HBP possesses similar properties to typical CPPs and is a potent drug delivery vector for improving the antitumor activity of impermeable MAP30. The intrinsic bioactivities of recombinant MAP30-HBP were well preserved compared to those of free MAP30. Furthermore, HBP conjugated to the C-terminus of MAP30 promoted the cellular uptake of recombinant MAP30-HBP. Moreover, the fusion of HBP to MAP30 gave rise to significantly enhanced cytotoxic effects in all of the tumor cell lines tested. In HeLa cells, this cytotoxicity was mainly caused by the induction of cell apoptosis. Further investigation revealed that HBP enhanced MAP30-induced apoptosis through the activation of the mitochondrial- and death receptor-mediated signaling pathways. In addition, the MAP30-HBP fusion protein caused more HeLa cells to become arrested in S phase compared to MAP30 alone. These results highlight the MAP30-HBP fusion protein as a promising drug candidate for cancer therapy and demonstrate HBP, a novel CPP derived from human HB-EGF, as a new potential vector for antitumor drug delivery. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Expression of Momordica charantia MAP30 and its antitumor effect on bladder cancer cells.

BACKGROUND: Momordica charantia (MC) is an edible medicinal plant that is known for its diversified biological functions. Momordica Antiviral Protein 30kD (MAP30) is a type I single chain ribosome-inactivating protein (RIP) isolated from the mature fruit and seeds of MC. Since MAP30 content in MC is limited, the study aim was to generate the recombinant MAP30 protein using prokaryotic expression system and determine its apoptotic/growth inhibitory effects on bladder cancer 5637 cells. METHODS: MAP30 gene was amplified by PCR from MC genomic DNA and identified by sequencing. The target gene was inserted into pET-28a (+) vector and transformed into E. coli BL21 (DE3) cells. Positive clones were selected by PCR. Recombinant protein was efficiently expressed under induction with 1.0 mM Isopropylthio-ß-D-galactoside (IPTG) at 30° C for 4 hours. Cytotoxicity studies were performed using MTT assay by treating 5637 bladder cancer cells with 100 µg/mL, 200 µg/mL, and 400 µg/mL concentrations of MAP30 for 24 hours and 48 hours, respectively. Flow cytometry was used to measure the apoptosis of MAP30-treatedcells in time course experiments. RESULTS: Full-length MAP30 gene was successfully expressed in Escherichia coli (E. coli) BL21 strain and MAP30 recombinant protein inhibited the growth of bladder cancer 5637 cells at 200 µg/mL and 400 µg/mL concentrations by inducing apoptosis of target cells in a dose- and time-dependent manner. CONCLUSION: It was, therefore, concluded that the MAP30 recombinant protein displayed potent antitumor activity in vitro.

Recombinant expression and purification of a MAP30-cell penetrating peptide fusion protein with higher anti-tumor bioactivity.

MAP30 (Momordica Antiviral Protein 30 Kd), a single-stranded type-I ribosome inactivating protein, possesses versatile biological activities including anti-tumor abilities. However, the low efficiency penetrating into tumor cells hampers the tumoricidal effect of MAP30. This paper describes MAP30 fused with a human-derived cell penetrating peptide HBD which overcome the low uptake efficiency by tumor cells and exhibits higher anti-tumor bioactivity. MAP30 gene was cloned from the genomic DNA of Momordica charantia and the recombinant plasmid pET28b-MAP30-HBD was established and transferred into Escherichia coli BL21 (DE3). The recombinant MAP30-HBD protein (rMAP30-HBD) was expressed in a soluble form after being induced by 0.5mM IPTG for 14h at 15°C. The recombinant protein was purified to greater than 95% purity with Ni-NTA affinity chromatography. The rMAP30-HBD protein not only has topological inactivation and protein translation inhibition activity but also showed significant improvements in cytotoxic activity compared to that of the rMAP30 protein without HBD in the tested tumor cell lines, and induced higher apoptosis rates in HeLa cells analyzed by Annexin V-FITC with FACS. This paper demonstrated a new method for improving MAP30 protein anti-tumor activity and might have potential applications in cancer therapy area.

[Expression of recombinant ribosome inactivating protein MAP30 in E.coli and its biological activity].

OBJECTIVE: To clone and produce ribosome inactivating protein MAP30 from the seeds of Momordica charantia L(bitter melon), and to evaluate the biological activity of the recombinant protein. METHODS: The DNA sequence encoding MAP30 was cloned from the fresh seeds of Momordica charantia by PCR, the target DNA fragments were sequenced after T-A cloning. The expression plasmid was constructed by inserting the MAP30 fragment into vector pET30a. MAP30 was expressed in E.coli by addition of IPTG into final concentration of 1.0 mmol/L. The recombinant MAP30 was identified by SDS-PAGE, and the biological activity of MAP30 protein was evaluated by using MTT assay in cancer cells and normal cells following fluid-phase endocytosis. RESULT: The nucleotide and amino acid sequences of the cloned MAP30 were identical with those of reported MAP30. The solubility of recombinant protein was analyzed by SDS-PAGE, and the MAP30 was mainly produced in soluble form. The recombinant MAP30 showed a greater cytotoxicity to cancer cells than that to normal cells. CONCLUSION: The gene of MAP30 has been successfully cloned.The recombinant MAP30 protein expressed by E.coli is bioactive.