Engineering of the Saccharomyces cerevisiae yeast strain with multiple chromosome-integrated genes of human alpha-fetoprotein and its high-yield secretory production, purification, structural and functional characterization

Structural characteristics of alpha-fetoprotein, including N-glycosylation, metal ion and fatty acid binding sites

Alpha-fetoprotein (AFP), a serum glycoprotein, is expressed during embryonic development and the pathogenesis of liver cancer. It serves as a clinical tumor marker, function as a carcinogen, immune suppressor, and transport vehicle; but the detailed AFP structural information has not yet been reported. In this study, we used single-particle cryo-electron microscopy(cryo-EM) to analyze the structure of the recombinant AFP obtained a 3.31 Å cryo-EM structure and built an atomic model of AFP. We observed and identified certain structural features of AFP, including N-glycosylation at Asn251, four natural fatty acids bound to distinct domains, and the coordination of metal ions by residues His22, His264, His268, and Asp280. Furthermore, we compared the structural similarities and differences between AFP and human serum albumin. The elucidation of AFP's structural characteristics not only contributes to a deeper understanding of its functional mechanisms, but also provides a structural basis for developing AFP-based drug vehicles.

Engineering strategies for enhanced heterologous protein production by Saccharomyces cerevisiae

Microbial proteins are promising substitutes for animal- and plant-based proteins. S. cerevisiae, a generally recognized as safe (GRAS) microorganism, has been frequently employed to generate heterologous proteins. However, constructing a universal yeast chassis for efficient protein production is still a challenge due to the varying properties of different proteins. With progress in synthetic biology, a multitude of molecular biology tools and metabolic engineering strategies have been employed to alleviate these issues. This review first analyses the advantages of protein production by S. cerevisiae. The most recent advances in improving heterologous protein yield are summarized and discussed in terms of protein hyperexpression systems, protein secretion engineering, glycosylation pathway engineering and systems metabolic engineering. Furthermore, the prospects for efficient and sustainable heterologous protein production by S. cerevisiae are also provided.

Comparison of Yeasts as Hosts for Recombinant Protein Production

Recombinant protein production emerged in the early 1980s with the development of genetic engineering tools, which represented a compelling alternative to protein extraction from natural sources. Over the years, a high level of heterologous protein was made possible in a variety of hosts ranging from the bacteria Escherichia coli to mammalian cells. Recombinant protein importance is represented by its market size, which reached $1654 million in 2016 and is expected to reach $2850.5 million by 2022. Among the available hosts, yeasts have been used for producing a great variety of proteins applied to chemicals, fuels, food, and pharmaceuticals, being one of the most used hosts for recombinant production nowadays. Historically, Saccharomyces cerevisiae was the dominant yeast host for heterologous protein production. Lately, other yeasts such as Komagataella sp., Kluyveromyces lactis, and Yarrowia lipolytica have emerged as advantageous hosts. In this review, a comparative analysis is done listing the advantages and disadvantages of using each host regarding the availability of genetic tools, strategies for cultivation in bioreactors, and the main techniques utilized for protein purification. Finally, examples of each host will be discussed regarding the total amount of protein recovered and its bioactivity due to correct folding and glycosylation patterns.

Recombinant human alpha fetoprotein synergistically potentiates the anti-cancer effects of 1'-S-1'-acetoxychavicol acetate when used as a complex against human tumours harbouring AFP-receptors

Purpose

Previous in vitro and in vivo studies have reported that 1′-S-1′-acetoxychavicol acetate (ACA) isolated from rhizomes of the Malaysian ethno-medicinal plant Alpinia conchigera Griff (Zingiberaceae) induces apoptosis-mediated cell death in tumour cells via dysregulation of the NF-κB pathway. However there were some clinical development drawbacks such as poor in vivo solubility, depreciation of biological activity upon exposure to an aqueous environment and non-specific targeting of tumour cells. In the present study, all the problems above were addressed using the novel drug complex formulation involving recombinant human alpha fetoprotein (rhAFP) and ACA.

Experimental Design

To study the synergistic effect of both agents on human cancer xenografts, athymic nude (Nu/Nu) mice were used and treated with various combination regimes intraperitoneally. Serum levels of tumour markers for carcinoembryonic antigen (CEA) and prostate specific antigen (PSA) were assessed using sandwich ELISA. IHC and Western blotting were also conducted on in vivo tumour biopsies to investigate the involvement of NF-κB regulated genes and inflammatory biomarkers. Quantification and correlation between drug efficacies and AFP-receptors were done using IF-IC and Pearson's correlation analysis.

Results

Mice exposed to combined treatments displayed higher reductions in tumour volume compared to stand alone agents, consistent with in vitro cytotoxicity assays. Milder signs of systemic toxicity, such as loss in body weight and inflammation of vital organs were also demonstrated compared to stand alone treatments. Tumour marker levels were consistent within all rhAFP/ACA treatment groups where levels of CEA and PSA were initially elevated upon commencement of treatment, and consecutively reduced corresponding to a decrease in tumour bulk volume. Both IHC and Western blotting results indicated that the combined action of rhAFP/ACA was not only able to down-regulate NF-κB activation, but also reduce the expression of NF-κB regulated genes and inflammatory biomarkers. The efficacy of rhAFP/ACA complex was also found to be weakly negatively correlated to the level of surface AFP-receptors between tumour types.

Conclusions

This drug complex formulation shows great therapeutic potential against AFP-receptor positive tumours, and serves as a basis to overcome insoluble and non-specific anti-neoplastic molecules.

The use of α-fetoprotein for the delivery of cytotoxic payloads to cancer cells

One approach to improving the activity of anticancer drugs is to bind them to the human α-fetoprotein (HAFP) that recognizes the tumor-associated cell-surface HAFP receptor. A drug can be bound to the HAFP by covalent conjugation or within a non-covalent complex. Specially designed linkers couple cytotoxins to the HAFP and ensure the stability of the HAFP-drug conjugate in the circulation and the activation of the drug in the cancer cell. On the other hand, AFP-drug non-covalent complexes can exploit the natural role of the AFP as a nutrition delivery "shuttle". In this article we review the design of HAFP-drug conjugates and AFP-drug complexes and their potential uses.

Alpha-fetoprotein contributes to THP-1 cell invasion and chemotaxis via protein kinase and Gi-protein-dependent pathways

Alpha-fetoprotein (AFP) for long was known as immunomodulator and tumor marker having multifaceted actions on the activity of normal and transformed cells. In present study, we have investigated the involvement of AFP in regulation of THP-1 cell line invasion and underlying mechanisms. Treatment with human recombinant AFP causes up-regulation of MMP9 expression, chemotaxis and calcium mobilization, and increases invasion through Matrigel, with no significant impact on THP-1 cell growth or viability. Using small molecule inhibitors, we have shown that the rhAFP-induced MMP9 expression depends on the activation of ERK1,2, JNK and Akt kinases, with the involvement of NFκB and likely, AP-1 transcription factors. In contrast, inhibition of p38 kinase, but not of JNK, had dramatic suppressive effect on the rhAFP-triggered chemotaxis. In addition, rhAFP-induced MMP9 expression and calcium response were completely blocked by pertussis toxin, indicating that Gi-protein-coupled receptor(s) has a mediatory role in these processes. CCR5 chemokine receptor is the only known Gi-protein binding to AFP. The action of CCR5 inhibitor Maraviroc results in partial suppression of MMP9 up-regulation and calcium response suggesting that CCR5 might be involved in these effects.