Cytotoxicity of a Novel Fibroblast Growth Factor Receptor Targeted Immunotoxin on a Human Ovarian Teratocarcinoma Cell Line

Targeted Diphtheria Toxin-Based Therapy: A Review Article

Cancer remains one of the leading causes of death worldwide. Conventional therapeutic strategies usually offer limited specificity, resulting in severe side effects and toxicity to normal tissues. Targeted cancer therapy, on the other hand, can improve the therapeutic potential of anti-cancer agents and decrease unwanted side effects. Targeted applications of cytolethal bacterial toxins have been found to be especially useful for the specific eradication of cancer cells. Targeting is either mediated by peptides or by protein-targeting moieties, such as antibodies, antibody fragments, cell-penetrating peptides (CPPs), growth factors, or cytokines. Together with a toxin domain, these molecules are more commonly referred to as immunotoxins. Targeting can also be achieved through gene delivery and cell-specific expression of a toxin. Of the available cytolethal toxins, diphtheria toxin (DT) is one of the most frequently used for these strategies. Of the many DT-based therapeutic strategies investigated to date, two immunotoxins, Ontak^TM and Tagraxofusp^TM, have gained FDA approval for clinical application. Despite some success with immunotoxins, suicide-gene therapy strategies, whereby controlled tumor-specific expression of DT is used for the eradication of malignant cells, are gaining prominence. The first part of this review focuses on DT-based immunotoxins, and it then discusses recent developments in tumor-specific expression of DT.

The FGF-1-specific single-chain antibody scFv1C9 effectively inhibits breast cancer tumour growth and metastasis

Immunotherapy mediated by recombinant antibodies is an effective therapeutic strategy for a variety of cancers. In a previous study, we demonstrated that the fibroblast growth factor 1 (FGF-1)-specific recombinant antibody scFv1C9 arrests the cell cycle at the G0/G1 transition by blocking the intracrine FGF-1 pathway in breast cancer cells. Here, we further show that the overexpression of scFv1C9 in MCF-7 and MDA-MB-231 breast cancer cells by lentiviral infection resulted in decreased tumourigenicity, tumour growth and lung metastasis through FGF-1 neutralization. We found that scFv1C9 resulted in the up-regulation of p21, which in turn inhibited the expression of CDK2 and blocked cell cycle progression. To explore the potential role of scFv1C9 in vivo, we delivered the gene into solid tumours by electroporation, which resulted in significant inhibition of tumour growth. In tumour tissue sections, immunohistochemical staining of the cellular proliferation marker Ki-67 and the microvessel marker CD31 showed a reduction in the proliferative index and microvessel density, respectively, upon expression of scFv1C9 compared with the appropriate controls. Thus, our data indicate a central role for scFv1C9 in blocking the intracrine pathway of FGF-1, therefore, scFv1C9 could be developed in an effective therapeutic for breast cancer.

Production and characterization of recombinant pertactin, fimbriae 2 and fimbriae 3 from Bordetella pertussis

BACKGROUND

Bordetella pertussis is a causative agent of pertussis or whooping cough in humans. Pertactin (Prn), fimbriae 2 (Fim2) and fimbriae 3 (Fim3) of B. pertussis are important virulence factors and immunogens which have been included in some acellular pertussis vaccines. In this present study, we cloned, expressed and purified Prn, Fim2 and Fim3, respectively. The immunogenicity and protective efficacy of the three recombinant proteins (rPrn, rFim2 and rFim3) were investigated in mouse model.

RESULTS

Three recombinant proteins with amount of 12 to 25 mg/L were produced. Compared to the control mice only immunized with adjuvant, serum IgG antibody responses were significantly induced in the mice immunized with rPrn, rFim2 or rFim3 (P < 0.001 for all three proteins). Furthermore, T cell responses characteristic of increased production of IL-2 and TNF-alpha (only for rPrn) were elicited in the mice immunized with the three proteins (P < 0.05 for all three proteins). Immunization with rPrn, but not with rFim2 or rFim3, significantly enhanced clearance of bacteria in the lungs of mice after intranasal challenge with B. pertussis (P < 0.05). When tested in a lethal intracerebral infection model, certain protection was observed in mice immunized with rPrn.

CONCLUSIONS

We have developed an efficient method to produce large amounts of rPrn, rFim2, and rFim3 from B. pertussis. The three recombinant proteins induced both humoral and cellular immune responses in mice. Immunization with rPrn also conferred protection against pertussis in mouse infection models. Our results indicated that the recombinant proteins still retain their immunological properties and highlighted the potential of the recombinant proteins for the future development of the B. pertussis vaccines.

Construction and characterization of a novel superantigen fusion protein: bFGF/SEB

BACKGROUND

As one of the bacterial superantigens, Staphylococcal enterotoxins (SEs) are potent activators of T cells, especially for those expressing T cell receptor V(beta) chains, and can induce the production of cytokines such as IFN-gamma, TNF-alpha, IL-1, IL-2, IL-6, IL-12, etc. Thus, SEs could be used in tumor-targeting therapy when cooperated with the vectors that can specifically recognize the tumor cells.

MATERIALS AND METHODS

The coding sequences of Staphylococcal enterotxin B (SEB) was amplified and fused with human basic fibroblast growth factor (bFGF). Recombinant protein SEB and fusion protein bFGF/SEB were expressed and purified. The biological activity was detected, including splenocytes proliferation, cytokine production, and cytotoxicity in tumor cells in vitro. In addition, the binding of bFGF/SEB with tumor cells and the tumor cell apoptosis were also tested by immunofluorescent technique.

RESULTS

The fusion protein bFGF/SEB had similar biological activities compared with natural SEA and recombinant SEB, including tumor-inhibition ratio.

CONCLUSION

The recombinant bFGF/SEB-fusion protein was shown to retain the superantigenic activity of SEB, and might be a novel promising immunotherapeutic agent for the treatment of some carcinomas.