Recombinant alpha-fetoprotein receptor-binding domain co-expression with polyglutamate tags facilitates in vivo folding in E. coli

The Role of Alpha-Fetoprotein (AFP) in Contemporary Oncology: The Path from a Diagnostic Biomarker to an Anticancer Drug

This article presents contemporary opinion on the role of alpha-fetoprotein in oncologic diagnostics and treatment. This role stretches far beyond the already known one-that of the biomarker of hepatocellular carcinoma. The turn of the 20th and 21st centuries saw a significant increase in knowledge about the fundamental role of AFP in the neoplastic processes, and in the induction of features of malignance and drug resistance of hepatocellular carcinoma. The impact of AFP on the creation of an immunosuppressive environment for the developing tumor was identified, giving rise to attempts at immunotherapy. The paper presents current and prospective therapies using AFP and its derivatives and the gene therapy options. We directed our attention to both the benefits and risks associated with the use of AFP in oncologic therapy.

Preparation and self-cleavage of fusion soluble farnesyl diphosphate synthase in E. coli

Farnesyl diphosphate synthase (FPPS) is a crucial protein in terpenoid production. However, its industrial application is limited owing to its low solubility in Escherichia coli. In this study, we focused on ispA encoding FPPS and designed a fusion expression system to reduce inclusion body (IB) formation. Among the chosen fusion tags, the GB1-domain (GB1) exhibited the highest ability to solubilize the recombinant protein. Increased rare tRNA abundance not only improved the GB1-FPPS yield but also increased its soluble level. A "one-step" method for the acquisition of soluble FPPS was also considered. By combining GB1-FPPS expression and Tobacco Etch Virus protease (TEVp) cleavage in vivo, a controllable GB1-FPPS "self-cleavage" system was constructed. Overall, this study provides an efficient approach for obtaining soluble forms of FPPS, which show great potential for use in the soluble expression of other homologous diphosphate synthase.

Alpha-fetoprotein mediated targeting of polymeric nanoparticles to treat solid tumors

Background: Serious side effects caused by paclitaxel formulation, containing toxic solubilizer Cremophor^® EL, and its nonspecific accumulation greatly limit clinical paclitaxel application. Aim: To design paclitaxel-loaded copolymer of lactic and glycolic acids nanoparticles decorated with alpha-fetoprotein third domain (rAFP3d-NP) to increase paclitaxel safety profile. Methods: rAFP3d-NP was obtained via carbodiimide technique. Results: The particles were characterized with high paclitaxel loading content of 5% and size of 280 nm. rAFP3d-NP revealed biphasic profile with 67% release of paclitaxel during 220 h. Increased area under the curve_inf and mean residence time values after rAFP3d-NP administration confirmed prolonged blood circulation compared with paclitaxel. rAFP3d-NP demonstrated significant tumor growth inhibition at 4T1 and SKOV-3 models. Conclusion: rAFP3d-NP is a promising delivery system for paclitaxel and can be applied similarly for delivery of other hydrophobic drugs.

Expression of acid cleavable Asp-Pro linked multimeric AFP peptide in E. coli

Background

Difficult to express peptides are usually produced by co-expression with fusion partners. In this case, a significant mass part of the recombinant product falls on the subsequently removed fusion partner. On the other hand, multimerization of peptides is known to improve its proteolytic stability in E. coli due to the inclusion of body formation, which is sequence specific. Thereby, the peptide itself may serve as a fusion partner and one may produce more than one mole of the desired product per mole of fusion protein. This paper proposes a method for multimeric production of a human alpha-fetoprotein fragment with optimized multimer design and processing. This fragment may further find its application in the cytotoxic drug delivery field or as an inhibitor of endogenous alpha-fetoprotein.

Results

Multimerization of the extended alpha-fetoprotein receptor-binding peptide improved its stability in E. coli, and pentamer was found to be the largest stable with the highest expression level. As high as 10 aspartate-proline bonds used to separate peptide repeats were easily hydrolyzed in optimized formic acid-based conditions with 100% multimer conversion. The major product was represented by unaltered functional alpha-fetoprotein fragment while most side-products were its formyl-Pro, formyl-Tyr, and formyl-Lys derivatives. Single-step semi-preparative RP-HPLC was enough to separate unaltered peptide from the hydrolysis mixture.

Conclusions

A recombinant peptide derived from human alpha-fetoprotein can be produced via multimerization with subsequent formic acid hydrolysis and RP-HPLC purification. The reported procedure is characterized by the lower reagent cost in comparison with enzymatic hydrolysis of peptide fusions and solid-phase synthesis. This method may be adopted for different peptide expression, especially with low amino and hydroxy side chain content.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-021-00265-5.