Expression and recovery of biologically active recombinant Apolipoprotein AI(Milano) from transgenic safflower (Carthamus tinctorius) seeds

Low-density lipoprotein: a versatile nanoscale platform for targeted delivery

Low-density lipoprotein (LDL) is a small lipoprotein that plays a vital role in controlling lipid metabolism. LDL has a delicate nanostructure with unique physicochemical properties: superior payload capacity, long residence time in circulation, excellent biocompatibility, smaller size, and natural targeting. In recent decades, the superiority and feasibility of LDL particles as targeted delivery carriers have attracted much attention. In this review, we introduce the structure, composition, advantages, defects, and reconstruction of LDL delivery systems, summarize their research status and progress in targeted diagnosis and therapy, and finally look forward to the clinical application of LDL as an effective delivery vehicle.

Expression of recombinant human Apolipoprotein A-IMilano in Nicotiana tabacum

Apolipoprotein A-IMilano (Apo A-IMilano) is a natural mutant of Apolipoprotein. It is currently the only protein that can clear arterial wall thrombus deposits and promptly alleviate acute myocardial ischemia. Apo A-IMilano is considered as the most promising therapeutic protein for treating atherosclerotic diseases without obvious toxic or side effects. However, the current biopharmaceutical platforms are not efficient for developing Apo A-IMilano. The objectives of this research were to express Apo A-IMilano using the genetic transformation ability of N. tabacum. The method is to clone the coding sequence of Apo A-IMilano into the plant binary expression vector pCHF3 with a Flag/His6/GFP tag. The constructed plasmid was transformed into N. tabacum by a modified agrobacterium-mediated method, and transformants were selected under antibiotic stress. PCR, RT-qPCR, western blot and co-localization analysis was used to further verify the resistant N. tabacum. The stable expression and transient expression of N. tabacum were established, and the pure product of Apo A-IMilano was obtained through protein A/G agarose. The results showed that Apo A-IMilano was expressed in N. tabacum with a yield of 0.05 mg/g leaf weight and the purity was 90.58% ± 1.65. The obtained Apo A-IMilano protein was subjected to amino acid sequencing. Compared with the theoretical sequence of Apo A-IMilano, the amino acid coverage was 86%, it is also found that Cysteine replaces Arginine at position 173, which indicates that Apo A-IMilano, a mutant of Apo A-I, is accurately expressed in N. tabacum. The purified Apo A-IMilano protein had a lipid binding activity. The established genetic modification N. tabacum will provide a cost-effective system for the production of Apo A-IMilano. Regarding the rapid propagation of N. tabacum, this system provides the possibility of large-scale production and accelerated clinical translation of Apo A-IMilano.

A modular approach toward producing nanotherapeutics targeting the innate immune system

Immunotherapies controlling the adaptive immune system are firmly established, but regulating the innate immune system remains much less explored. The intrinsic interactions between nanoparticles and phagocytic myeloid cells make these materials especially suited for engaging the innate immune system. However, developing nanotherapeutics is an elaborate process. Here, we demonstrate a modular approach that facilitates efficiently incorporating a broad variety of drugs in a nanobiologic platform. Using a microfluidic formulation strategy, we produced apolipoprotein A1-based nanobiologics with favorable innate immune system-engaging properties as evaluated by in vivo screening. Subsequently, rapamycin and three small-molecule inhibitors were derivatized with lipophilic promoieties, ensuring their seamless incorporation and efficient retention in nanobiologics. A short regimen of intravenously administered rapamycin-loaded nanobiologics (mTORi-NBs) significantly prolonged allograft survival in a heart transplantation mouse model. Last, we studied mTORi-NB biodistribution in nonhuman primates by PET/MR imaging and evaluated its safety, paving the way for clinical translation.

Seeds as Economical Production Platform for Recombinant Proteins

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The cost-effective production of high-quality and biologically active recombinant molecules especially proteins is extremely desirable. Seed-based recombinant protein production platforms are considered as superior choice owing to lack of human/animal pathogenic organisms, lack of cold chain requirements for transportation and long-term storage, easy scalability and development of edible biopharmaceuticals in plants with objective to be used in purified or partially processed form is desirable. This review article summarizes the exceptional features of seed-based biopharming and highlights the needs of exploiting it for commercial purposes. Plant seeds offer a perfect production platform for high-value molecules of industrial as well as therapeutic nature owing to lower water contents, high protein storage capacity, weak protease activity and long-term storage ability at ambient temperature. Exploiting extraordinarily high protein accumulation potential, vaccine antigens, antibodies and other therapeutic proteins can be stored without effecting their stability and functionality up to years in seeds. Moreover, ability of direct oral consumption and post-harvest stabilizing effect of seeds offer unique feature of oral delivery of pharmaceutical proteins and vaccine antigens for immunization and disease treatment through mucosal as well as oral route.

Biotechnological Production of the Cell Penetrating Antifungal PAF102 Peptide in Pichia pastoris

Antimicrobial peptides (AMPs) have potent and durable antimicrobial activity to a wide range of fungi and bacteria. The growing problem of drug-resistant pathogenic microorganisms, together with the lack of new effective compounds, has stimulated interest in developing AMPs as anti-infective molecules. PAF102 is an AMP that was rationally designed for improved antifungal properties. This cell penetrating peptide has potent and specific activity against major fungal pathogens. Cecropin A is a natural AMP with strong and fast lytic activity against bacterial and fungal pathogens, including multidrug resistant pathogens. Both peptides, PAF102 and Cecropin A, are alternative antibiotic compounds. However, their exploitation requires fast, cost-efficient production systems. Here, we developed an innovative system to produce AMPs in Pichia pastoris using the oleosin fusion technology. Oleosins are plant-specific proteins with a structural role in lipid droplet formation and stabilization, which are used as carriers for recombinant proteins to lipid droplets in plant-based production systems. This study reports the efficient production of PAF102 in P. pastoris when fused to the rice plant Oleosin 18, whereas no accumulation of Cecropin A was detected. The Ole18-PAF102 fusion protein targets the lipid droplets of the heterologous system where it accumulates to high levels. Interestingly, the production of this fusion protein induces the formation of lipid droplets in yeast cells, which can be additionally enhanced by the coexpression of a diacylglycerol transferase gene that allows a three-fold increase in the production of the fusion protein. Using this high producer strain, PAF102 reaches commercially relevant yields of up to 180 mg/l of yeast culture. Moreover, the accumulation of PAF102 in the yeast lipid droplets facilitates its downstream extraction and recovery by flotation on density gradients, with the recovered PAF102 being biologically active against pathogenic fungi. Our results demonstrate that plant oleosin fusion technology can be transferred to the well-established P. pastoris cell factory to produce the PAF102 antifungal peptide, and potentially other AMPs, for multiple applications in crop protection, food preservation and animal and human therapies.

Rice Seeds as Biofactories of Rationally Designed and Cell-Penetrating Antifungal PAF Peptides

PAFs are short cationic and tryptophan-rich synthetic peptides with cell-penetrating antifungal activity. They show potent and selective killing activity against major fungal pathogens and low toxicity to other eukaryotic and bacterial cells. These properties make them a promising alternative to fulfill the need of novel antifungals with potential applications in crop protection, food preservation, and medical therapies. However, the difficulties of cost-effective manufacturing of PAFs by chemical synthesis or biotechnological production in microorganisms have hampered their development for practical use. This work explores the feasibility of using rice seeds as an economical and safe production system of PAFs. The rationally designed PAF102 peptide with improved antifungal properties was selected for assessing PAF biotechnological production. Two different strategies are evaluated: (1) the production as a single peptide targeted to protein bodies and (2) the production as an oleosin fusion protein targeted to oil bodies. Both strategies are designed to offer stability to the PAF peptide in the host plant and to facilitate its downstream purification. Our results demonstrate that PAF does not accumulate to detectable levels in rice seeds when produced as a single peptide, whereas it is successfully produced as fusion protein to the Oleosin18, up to 20 μg of peptide per gram of grain. We show that the expression of the chimeric Ole18-PAF102 gene driven by the Ole18 promoter results in the specific accumulation of the fusion protein in the embryo and aleurone layer of the rice seed. Ole18-PAF102 accumulation has no deleterious effects on seed yield, germination capacity, or seedling growth. We also show that the Oleosin18 protein serves as carrier to target the fusion protein to oil bodies facilitating PAF102 recovery. Importantly, the recovered PAF102 is active against the fungal phytopathogen Fusarium proliferatum. Altogether, our results prove that the oleosin fusion technology allows the production of PAF bioactive peptides to assist the exploitation of these antifungal compounds.

Russell-Like Bodies in Plant Seeds Share Common Features With Prolamin Bodies and Occur Upon Recombinant Protein Production

Although many recombinant proteins have been produced in seeds at high yields without adverse effects on the plant, endoplasmic reticulum (ER) stress and aberrant localization of endogenous or recombinant proteins have also been reported. The production of murine interleukin-10 (mIL-10) in Arabidopsis thaliana seeds resulted in the de novo formation of ER-derived structures containing a large fraction of the recombinant protein in an insoluble form. These bodies containing mIL-10 were morphologically similar to Russell bodies found in mammalian cells. We confirmed that the compartment containing mIL-10 was enclosed by ER membranes, and 3D electron microscopy revealed that these structures have a spheroidal shape. Another feature shared with Russell bodies is the continued viability of the cells that generate these organelles. To investigate similarities in the formation of Russell-like bodies and the plant-specific protein bodies formed by prolamins in cereal seeds, we crossed plants containing ectopic ER-derived prolamin protein bodies with a line accumulating mIL-10 in Russell-like bodies. This resulted in seeds containing only one population of protein bodies in which mIL-10 inclusions formed a central core surrounded by the prolamin-containing matrix, suggesting that both types of protein aggregates are together removed from the secretory pathway by a common mechanism. We propose that, like mammalian cells, plant cells are able to form Russell-like bodies as a self-protection mechanism, when they are overloaded with a partially transport-incompetent protein, and we discuss the resulting challenges for recombinant protein production.

APOA-1Milano muteins, orally delivered via genetically modified rice, show anti-atherogenic and anti-inflammatory properties in vitro and in Apoe-/- atherosclerotic mice

BACKGROUND

Atherosclerosis is a slowly progressing, chronic multifactorial disease characterized by the accumulation of lipids, inflammatory cells, and fibrous tissue that drives to the formation of asymmetric focal thickenings in the tunica intima of large and mid-sized arteries. Despite the high therapeutic potential of ApoA-1 proteins, the purification and delivery into the disordered organisms of these drugs is still limited by low efficiency in these processes.

METHODS AND RESULTS

We report here a novel production and delivery system of anti-atherogenic APOA-1Milano muteins (APOA-1M) by means of genetically modified rice plants. APOA-1M, delivered as protein extracts from transgenic rice seeds, significantly reduced macrophage activation and foam cell formation in vitro in oxLDL-loaded THP-1 model. The APOA-1M delivery method and therapeutic efficacy was tested in healthy mice and in Apoe^-/- mice fed with high cholesterol diet (Western Diet, WD). APOA-1M rice milk significantly reduced atherosclerotic plaque size and lipids composition in aortic sinus and aortic arch of WD-fed Apoe^-/- mice as compared to wild type rice milk-treated, WD-fed Apoe^-/- mice. APOA-1M rice milk also significantly reduced macrophage number in liver of WD-fed Apoe^-/- mice as compared to WT rice milk treated mice.

TRANSLATIONAL IMPACT

The delivery of therapeutic APOA-1M full length proteins via oral administration of rice seeds protein extracts (the 'rice milk') to the disordered organism, without any need of purification, might overcome the main APOA1-based therapies' limitations and improve the use of this molecules as therapeutic agents for cardiovascular patients.

Efficacy and safety assessment of a TRAF6-targeted nanoimmunotherapy in atherosclerotic mice and non-human primates

Macrophage accumulation in atherosclerosis is directly linked to the destabilization and rupture of plaque, causing acute atherothrombotic events. Circulating monocytes enter the plaque and differentiate into macrophages, where they are activated by CD4+ T lymphocytes through CD40-CD40 ligand signalling. Here, we report the development and multiparametric evaluation of a nanoimmunotherapy that moderates CD40-CD40 ligand signalling in monocytes and macrophages by blocking the interaction between CD40 and tumour necrosis factor receptor-associated factor 6 (TRAF6). We evaluated the biodistribution characteristics of the nanoimmunotherapy in apolipoprotein E-deficient (Apoe-/-) mice and in non-human primates by in vivo positron-emission tomography imaging. In Apoe-/- mice, a 1-week nanoimmunotherapy treatment regimen achieved significant anti-inflammatory effects, which was due to the impaired migration capacity of monocytes, as established by a transcriptome analysis. The rapid reduction of plaque inflammation by the TRAF6-targeted nanoimmunotherapy and its favourable toxicity profiles in both mice and non-human primates highlights the translational potential of this strategy for the treatment of atherosclerosis.

Lipoproteins for therapeutic delivery: recent advances and future opportunities

The physiological role(s) of mammalian plasma lipoproteins is to transport hydrophobic molecules (primarily cholesterol and triacylglycerols) to their respective destinations. Lipoproteins have also been studied as drug-delivery agents due to their advantageous payload capacity, long residence time in the circulation and biocompatibility. The purpose of this review is to briefly discuss current findings with the focus on each type of formulation's potential for clinical applications. Regarding utilizing lipoprotein type formulation for cancer therapeutics, their potential for tumor-selective delivery is also discussed.

Production of Biologically Active Cecropin A Peptide in Rice Seed Oil Bodies

Cecropin A is a natural antimicrobial peptide that exhibits fast and potent activity against a broad spectrum of pathogens and neoplastic cells, and that has important biotechnological applications. However, cecropin A exploitation, as for other antimicrobial peptides, is limited by their production and purification costs. Here, we report the efficient production of this bioactive peptide in rice bran using the rice oleosin 18 as a carrier protein. High cecropin A levels were reached in rice seeds driving the expression of the chimeric gene by the strong embryo-specific oleosin 18 own promoter, and targeting the peptide to the oil body organelle as an oleosin 18-cecropin A fusion protein. The accumulation of cecropin A in oil bodies had no deleterious effects on seed viability and seedling growth, as well as on seed yield. We also show that biologically active cecropin A can be easily purified from the transgenic rice seeds by homogenization and simple flotation centrifugation methods. Our results demonstrate that the oleosin fusion technology is suitable for the production of cecropin A in rice seeds, which can potentially be extended to other antimicrobial peptides to assist their exploitation.

Liquid-Liquid Phase Separation of Oil Bodies from Seeds

Fundamentally, oil bodies are discrete storage organelles found in oilseeds, comprising a hydrophobic triacylglycerol core surrounded by a half-unit phospholipid membrane and an outer shell of specialized proteins known as oleosins. Oil bodies possess a number of attributes that were exploited by SemBioSys Genetics to isolate highly enriched fractions of oil bodies through liquid-liquid phase separation for a number of commercial applications. The current chapter provides a general guide for the isolation of oil bodies from Arabidopsis and/or safflower seed, from which protocols can be refined for different oilseed sources. For SemBioSys Genetic's recombinant technology, therapeutic proteins were covalently attached to oleosins or fused in-frame with ligands which bound oil bodies, facilitating their recovery to high levels of purity during "upstream processing" of transformed seed. Core to this technology was oil body isolation consisting of simple manipulation including homogenization of seeds to free the oil bodies, followed by the removal of insoluble fractions, and phase separation to recover the oil bodies. During oil body enrichment (an increase in oil body content concomitant with removal of impurities), a number of options and tips are provided to aid researchers in the manipulation and monitoring of these robust organelles.

HDL/ApoA-1 infusion and ApoA-1 gene therapy in atherosclerosis

The HDL hypothesis stating that simply raising HDL cholesterol (HDL-C) may produce cardiovascular benefits has been questioned recently based on several randomized clinical trials using CETP inhibitors or niacin to raise HDL-C levels. However, extensive pre-clinical data support the vascular protective effects of administration of exogenous ApoA-1 containing preβ-HDL like particles. Several small proof-of-concept clinical trials using such HDL/ApoA-1 infusion therapy have shown encouraging results but definitive proof of efficacy must await large scale clinical trials. In addition to HDL infusion therapy an alternative way to exploit beneficial cardiovascular effects of HDL/ApoA-1 is to use gene transfer. Preclinical studies have shown evidence of benefit using this approach; however clinical validation is yet lacking. This review summarizes our current knowledge of the aforementioned strategies.

Learning from biology: synthetic lipoproteins for drug delivery

Synthetic lipoproteins represent a relevant tool for targeted delivery of biological/chemical agents (chemotherapeutics, siRNAs, photosensitizers, and imaging contrast agents) into various cell types. These nanoparticles offer a number of advantages for drugs delivery over their native counterparts while retaining their natural characteristics and biological functions. Their ultra-small size (<30 nm), high biocompatibility, favorable circulation half-life, and natural ability to bind specific lipoprotein receptors, i.e., low-density lipoprotein receptor (LDLR) and Scavenger receptor class B member 1 (SRB1) that are found in a number of pathological conditions (e.g., cancer, atherosclerosis), make them superior delivery strategies when compared with other nanoparticle systems. We review the various approaches that have been developed for the generation of synthetic lipoproteins and their respective applications in vitro and in vivo. More specifically, we summarize the approaches employed to address the limitation on use of reconstituted lipoproteins by means of natural or recombinant apolipoproteins, as well as apolipoprotein mimetic molecules. Finally, we provide an overview of the advantages and disadvantages of these approaches and discuss future perspectives for clinical translation of these nanoparticles.

Proteolysis of recombinant proteins in bioengineered plant cells

Plants are increasingly used as alternative expression hosts for the production of recombinant proteins offering many advantages including higher biomass and the ability to perform post-translational modifications on complex proteins. Key challenges for optimized accumulation of recombinant proteins in a plant system still remain, including endogenous plant proteolytic activity, which may severely compromise recombinant protein stability. Several strategies have recently been applied to improve protein stability by limiting protease action such as recombinant protein production in various sub-cellular compartments or application of protease inhibitors to limit protease action. A short update on the current strategies applied is provided here, with particular focus on sub-cellular sites previously selected for recombinant protein production and the co-expression of protease inhibitors to limit protease activity.

Plant molecular pharming for the treatment of chronic and infectious diseases

Plant molecular pharming has emerged as a niche technology for the manufacture of pharmaceutical products indicated for chronic and infectious diseases, particularly for products that do not fit into the current industry-favored model of fermenter-based production campaigns. In this review, we explore the areas where molecular pharming can make the greatest impact, including the production of pharmaceuticals that have novel glycan structures or that cannot be produced efficiently in microbes or mammalian cells because they are insoluble or toxic. We also explore the market dynamics that encourage the use of molecular pharming, particularly for pharmaceuticals that are required in small amounts (such as personalized medicines) or large amounts (on a multi-ton scale, such as blood products and microbicides) and those that are needed in response to emergency situations (pandemics and bioterrorism). The impact of molecular pharming will increase as the platforms become standardized and optimized through adoption of good manufacturing practice (GMP) standards for clinical development, offering a new opportunity to produce inexpensive medicines in regional markets that are typically excluded under current business models.

The Escherichia coli-derived thymosin β4 concatemer promotes cell proliferation and healing wound in mice

Thymosin β4 (Tβ4) is one of the most promising thymosins for future clinical applications, and it is anticipated that commercial demand for Tβ4 will increase. In order to develop a new approach to produce recombinant Tβ4, a 168 bp DNA (termed Tβ4) was designed based on the Tβ4 protein sequence and used to express a 4 × Tβ4 concatemer (four tandem copies of Tβ4, termed 4 × Tβ4) together with a histidine tag (6 × His) in E. coli (strain BL21). SDS-PAGE and western blot analysis were used to confirm that a recombinant 4 × Tβ4 protein of the expected size (30.87 kDa) was produced following the induction of the bacterial cultures with isopropyl β-D-thiogalactoside (IPTG). The E. coli-derived 4 × Tβ4 was purified by Ni-NTA resin, and its activities were examined with regard to both stimulating proliferation of the mice spleen cells in vitro and in vivo wound healing. The results demonstrate that these activities of the E. coli-derived recombinant 4 × Tβ4 were similar or even better than existing commercially obtained Tβ4. This production strategy therefore represents a potentially valuable approach for future commercial production of recombinant Tβ4.

Improving pharmaceutical protein production in Oryza sativa

Application of plant expression systems in the production of recombinant proteins has several advantages, such as low maintenance cost, absence of human pathogens, and possession of complex post-translational glycosylation capabilities. Plants have been successfully used to produce recombinant cytokines, vaccines, antibodies, and other proteins, and rice (Oryza sativa) is a potential plant used as recombinant protein expression system. After successful transformation, transgenic rice cells can be either regenerated into whole plants or grown as cell cultures that can be upscaled into bioreactors. This review summarizes recent advances in the production of different recombinant protein produced in rice and describes their production methods as well as methods to improve protein yield and quality. Glycosylation and its impact in plant development and protein production are discussed, and several methods of improving yield and quality that have not been incorporated in rice expression systems are also proposed. Finally, different bioreactor options are explored and their advantages are analyzed.

Conference Scene: Molecular pharming: manufacturing medicines in plants

Within the expanding area of molecular pharming, the development of plants for manufacturing immunoglobulins, enzymes, virus-like particles and vaccines has become a major focus point. On 21 September 2012, the meeting ‘Molecular Pharming – recent progress in manufacturing medicines in plants’, hosted by EuroSciCon, was held at the Bioscience Catalyst campus, Stevenage, UK. The scientific program of this eventful meeting covered diverse highlights of biopharming: monoclonal antibodies, virus-like particles from transient and chloroplast expression systems, for example, for Dengue and HPV, apolipoproteins from safflower seeds, and new production platforms, such as potato or hydroponics by rhizosecretion. This report summarizes the stimulating scientific presentations and fruitful panel discussions on the current topics in this promising research field.

Transgenic expression of therapeutic proteins in Arabidopsis thaliana seed

The production of therapeutic proteins in plant seed augments alternative production platforms such as microbial fermentation, cell-based systems, transgenic animals, and other recombinant plant production systems to meet increasing demands for the existing biologics, drugs under evaluation, and undiscovered therapeutics in the future. We have developed upstream purification technologies for oilseeds which are designed to cost-effectively purify therapeutic proteins amenable to conventional downstream manufacture. A very useful tool in these endeavors is the plant model system Arabidopsis thaliana. The current chapter describes the rationale and methods used to over-express potential therapeutic products in A. thaliana seed for evaluation and definitive insight into whether our production platform, Safflower, can be utilized for large-scale manufacture.

Purification of the therapeutic antibody trastuzumab from genetically modified plants using safflower Protein A-oleosin oilbody technology

Production of therapeutic monoclonal antibodies using genetically modified plants may provide low cost, high scalability and product safety; however, antibody purification from plants presents a challenge due to the large quantities of biomass that need to be processed. Protein A column chromatography is widely used in the pharmaceutical industry for antibody purification, but its application is limited by cost, scalability and column fouling problems when purifying plant-derived antibodies. Protein A-oleosin oilbodies (Protein A-OB), expressed in transgenic safflower seeds, are relatively inexpensive to produce and provide a new approach for the capture of monoclonal antibodies from plants. When Protein A-OB is mixed with crude extracts from plants engineered to express therapeutic antibodies, the Protein A-OB captures the antibody in the oilbody phase while impurities remain in the aqueous phase. This is followed by repeated partitioning of oilbody phase against an aqueous phase via centrifugation to remove impurities before purified antibody is eluted from the oilbodies. We have developed this purification process to recover trastuzumab, an anti-HER2 monoclonal antibody used for therapy against specific breast-cancers that over express HER2 (human epidermal growth factor receptor 2), from transiently infected Nicotiana benthamiana. Protein A-OB overcomes the fouling problem associated with traditional Protein A chromatography, allowing for the development of an inexpensive, scalable and novel high-resolution method for the capture of antibodies based on simple mixing and phase separation.

Lipoprotein-inspired nanoparticles for cancer theranostics

Over hundreds of millions of years, animals have evolved endogenous lipoprotein nanoparticles for shuttling hydrophobic molecules to different parts of the body. In the last 70 years, scientists have developed an understanding of lipoprotein function, often in relationship to lipid transport and heart disease. Such biocompatible, lipid–protein complexes are also ideal for loading and delivering cancer therapeutic and diagnostic agents, which means that lipoprotein and lipoprotein-inspired nanoparticles also offer opportunities for cancer theranostics. By mimicking the endogenous shape and structure of lipoproteins, the nanocarrier can remain in circulation for an extended period of time, while largely evading the reticuloendothelial cells in the body’s defenses. The small size (less than 30 nm) of the low-density (LDL) and high-density (HDL) classes of lipoproteins allows them to maneuver deeply into tumors. Furthermore, lipoproteins can be targeted to their endogenous receptors, when those are implicated in cancer, or to other cancer receptors.

In this Account, we review the field of lipoprotein-inspired nanoparticles related to the delivery of cancer imaging and therapy agents. LDL has innate cancer targeting potential and has been used to incorporate diverse hydrophobic molecules and deliver them to tumors. Nature’s method of rerouting LDL in atherosclerosis provides a strategy to extend the cancer targeting potential of lipoproteins beyond its narrow purview. Although LDL has shown promise as a drug nanocarrier for cancer imaging and therapy, increasing evidence indicates that HDL, the smallest lipoprotein, may also be of use for drug targeting and uptake into cancer cells. We also discuss how synthetic HDL-like nanoparticles, which do not include human or recombinant proteins, can deliver molecules directly to the cytoplasm of certain cancer cells, effectively bypassing the endosomal compartment. This strategy could allow HDL-like nanoparticles to be used to deliver drugs that have increased activity in the cytoplasm. Lipoprotein nanoparticles have evolved to be ideal delivery vehicles, and because of that specialized function, they have the potential to improve cancer theranostics.

High level accumulation of gamma linolenic acid (C18:3Δ6.9,12 cis) in transgenic safflower (Carthamus tinctorius) seeds

Gamma linolenic acid (GLA; C18:3Δ6,9,12 cis), also known as γ-Linolenic acid, is an important essential fatty acid precursor for the synthesis of very long chain polyunsaturated fatty acids and important pathways involved in human health. GLA is synthesized from linoleic acid (LA; C18:2Δ9,12 cis) by endoplasmic reticulum associated Δ6-desaturase activity. Currently sources of GLA are limited to a small number of plant species with poor agronomic properties, and therefore an economical and abundant commercial source of GLA in an existing crop is highly desirable. To this end, the seed oil of a high LA cultivated species of safflower (Carthamus tinctorius) was modified by transformation with Δ6-desaturase from Saprolegnia diclina resulting in levels exceeding 70% (v/v) of GLA. Levels around 50% (v/v) of GLA in seed oil was achieved when Δ12-/Δ6-desaturases from Mortierella alpina was over-expressed in safflower cultivars with either a high LA or high oleic (OA; C18:1Δ9 cis) background. The differences in the overall levels of GLA suggest the accumulation of the novel fatty acid was not limited by a lack of incorporation into the triacylgylcerol backbone (>66% GLA achieved), or correlated with gene dosage (GLA levels independent of gene copy number), but rather reflected the differences in Δ6-desaturase activity from the two sources. To date, these represent the highest accumulation levels of a newly introduced fatty acid in a transgenic crop. Events from these studies have been propagated and recently received FDA approval for commercialization as Sonova™400.

Agrobacterium-mediated transformation of safflower and the efficient recovery of transgenic plants via grafting

BACKGROUND

Safflower (Carthamus tinctorius L.) is a difficult crop to genetically transform being susceptible to hyperhydration and poor in vitro root formation. In addition to traditional uses safflower has recently emerged as a broadacre platform for the production of transgenic products including modified oils and pharmaceutically active proteins. Despite commercial activities based on the genetic modification of safflower, there is no method available in the public domain describing the transformation of safflower that generates transformed T1 progeny.

RESULTS

An efficient and reproducible protocol has been developed with a transformation efficiency of 4.8% and 3.1% for S-317 (high oleic acid content) and WT (high linoleic acid content) genotypes respectively. An improved safflower transformation T-DNA vector was developed, including a secreted GFP to allow non-destructive assessment of transgenic shoots. Hyperhydration and necrosis of Agrobacterium-infected cotyledons was effectively controlled by using iota-carrageenan, L-cysteine and ascorbic acid. To overcome poor in vitro root formation for the first time a grafting method was developed for safflower in which ~50% of transgenic shoots develop into mature plants bearing viable transgenic T1 seed. The integration and expression of secreted GFP and hygromycin genes were confirmed by PCR, Southern and Western blot analysis. Southern blot analysis in nine independent lines indicated that 1-7 transgenes were inserted per line and T1 progeny displayed Mendelian inheritance.

CONCLUSIONS

This protocol demonstrates significant improvements in both the efficiency and ease of use over existing safflower transformation protocols. This is the first complete method of genetic transformation of safflower that generates stably-transformed plants and progeny, allowing this crop to benefit from modern molecular applications.