Expression and purification of truncated diphtheria toxin, DT386, in Escherichia coli: An attempt for production of a new vaccine against diphtheria

Production of recombinant DNA fragmentation factor 40 in fusion to an antimicrobial peptide from spider venom and evaluation of its cytotoxic effects

Background and purpose

DNA fragmentation factor 40 (DFF40) as an apoptotic molecule can represent a novel approach to cancer treatment. Lycosin-I (LYC-I), a peptide derived from spider venom, was considered for the targeted delivery of DFF40 to cancer cells. This study attempted to produce soluble DFF40-LYC-I and evaluate its selective lethal effects on HeLa cells.

Experimental approach

pTWINl vector was used to produce LYC-I and DFF40-LYC-I in E. coli BL21 (DE3) fused to inteins 1 and 2. IPTG concentration and incubation temperature were optimized to achieve the highest level of soluble product. To remove inteins 1 and 2 from the recombinant peptide or protein, pH shift and dithiothreitol were used for a 24-h incubation period at room temperature, respectively. MTT assay was performed to assess the biological effects of these bio-molecules on HeLa and HUVEC cell lines.

Findings/Results

LYC-I and DFF40-LYC-I were detected in SDS-PAGE with bands of approximately 57 and 97 kDa, respectively. Furthermore, the 3 and 43 kDa bands showed the purified molecules. The IC50 value of DFF40-LYC-I and DFF40 was determined as 6.6 and 17.03 μg/mL for HeLa, respectively. LYC-I had no cytotoxic effects on both cell lines, even at high concentrations.

Conclusion and implications

A new fusion protein with targeted cancer treatment potential was produced for the first time by LYC-I with a safe profile on normal cells. This fusion protein exhibited higher cytotoxic effects in cancer cells compared to normal cells. However, additional investigations are required to determine the apoptosis induction and evaluate selective toxicity against other cancer and normal cell lines.

In vivo solid tumor targeting with recombinant VEGF-diphtheria immunotoxin

Objectives

A variety of signaling molecules have been identified that play a role in angiogenesis, of prime importance, vascular endothelial growth factor (VEGF) and its resceptor (VEGFR), which is highly expressed in most human solid tumors. Targeting VEGF or/and VEGFR with immunotoxin may be a promising approach to directly affect cancer cells. Immunotoxins are for targeted treatment comprising two functional moieties, an antibody that binds to target cells along with toxin that kills molecules.

Materials and Methods

In this study, an immunotoxin comprising domain of diphtheria toxin subunit A (DT386) genetically fused to mouse VEGF (mVEGF-DT) was developed. The second construct, which contains the DT386 domain, was made to investigate the action of the DT386 domain on tumor cells. Both gene constructs were cloned, expressed, and were further purified. The biological activity of mVEGF-DT and DT386 proteins was assessed on the TC1 cell line bearing mouse model. Proteins were injected intra-tumoral in mice, in separate groups.

Results

Tumors in the mVEGF-DT group started to dwindle after six injections, but tumor size in both control groups (DT386 and PBS), continued to grow.

Conclusion

Successful targeting of solid tumor cells by mVEGF-DT immunotoxin demonstrates the therapeutic potential utility of these conjugates for tumor targeting.