The Research Progress of Taxol in Taxus

Enhancing the biosynthesis of taxadien-5α-yl-acetate in Escherichia coli by combinatorial metabolic engineering approaches

Biosynthesis of paclitaxel (Taxol™) is a hot topic with extensive and durable interests for decades. However, it is severely hindered due to the very low titers of intermediates. In this study, Escherichia coli was employed to de novo synthesize a key intermediate of paclitaxel, taxadien-5α-yl-acetate (T5OAc). Plasmid-based pathway reconstruction and optimization were conducted for T5OAc production. The endogenous methylerythritol phosphate pathway was enhanced to increase the precursor supply. Three taxadien-5α-ol O-acetyltransferases were tested to obtain the best enzyme for the acetylation step. Metabolic burden was relieved to restore cell growth and promote production through optimizing the plasmid production system. In order to achieve metabolic balance, the biosynthesis pathway was regulated precisely by multivariate-modular metabolic engineering. Finally, in a 5-L bioreactor, the T5OAc titer was enhanced to reach 10.9 mg/L. This represents an approximately 272-fold increase in production compared to the original strain, marking the highest yield of T5OAc ever documented in E. coli, which is believed to be helpful for promoting the progress of paclitaxel biosynthesis.

Compound Taxus exerts marked anti-tumor activity and radiosensitization effect on hepatocellular carcinoma cells

Background

Compound Taxus capsule, as an antineoplastic Chinese patent drug, has been increasingly applied as an adjunctive treatment for the management of non-small-cell lung cancer (NSCLC) and some other malignancies, but research about its antitumor activity and radiosensitization effect on hepatocellular carcinoma (HCC) cells is very rare.

Purpose

To investigate the antitumor activity and radiosensitization effect of Compound Taxus on HCC cells and to preliminarily explore the possible molecule mechanisms involved.

Methods

Cell viability, cell cycle distribution, apoptosis, DNA damage repair and protein expression levels were detected by CCK-8 assay, flow cytometry, immunofluorescence staining, western blotting analysis and immunohistochemical staining, respectively. The migration and invasion activities and vasculogenic mimicry (VM) formation and angiogenesis were evaluated by tube formation and VM formation assay. Radiation survival curves were obtained from the colony formation assay in human HCC cell lines, Smmc7721 and Bel7402 cells, pretreated with or without Compound Taxus before receiving X-ray irradiation. A Bel7402 tumor-bearing mouse model was established and the radiosensitization effect of Compound Taxus in vivo was evaluated by analyzing tumor volume and tumor weight in different groups receiving different treatments.

Results

Compound Taxus decreased viability, induced G2/M arrest, promoted apoptosis, suppressed migration and invasion, and inhibited VM formation and angiogenesis in Smmc7721 and Bel7402 cells. Furthermore, Compound Taxus inhibited irradiation-induced DNA damage repair, enhanced the radiosensitivity of Smmc7721 and Bel7402 cells and improved the anti-tumor therapeutic efficacy of irradiation in Bel7402 tumor-bearing mice. Radiotherapy in combination with Compound Taxus showed the best tumor inhibition compared to that of Compound Taxus alone or irradiation alone. In addition, Compound Taxus significantly down-regulated NF-κB p65, p-NF-κB p65 and Bcl-2, and up-regulated Bax in vitro and in vivo, yet NF-κB p65 overexpression reversed the proapoptotic effect of Taxus on HCC cells, indicating that the NF-κB signaling pathway might be an important signal mediator in the Compound-Taxus-modulated biological responses.

Conclusion

Our findings suggest that Compound Taxus shows marked antitumor activity and significant radiosensitization effect on HCC cells, making it possible for Compound Taxus to become a promising auxiliary modality for HCC management and a potential radiosensitizer of HCC in the future.

Changes in marker secondary metabolites revealed the medicinal parts, harvest time, and possible synthetic sites of Rubia cordifolia L

Rubia cordifolia L. is a significant medicinal plant. To investigate the changes of marker metabolites of R. cordifolia, the purpurin, mollugin, carbon, nitrogen contents, and the expression of genes involved in anthraquinones synthesis were examined. The findings indicated that the two secondary metabolites were only detected in stems and roots. Root purpurin content was 5-26 times higher than in stems, and root mollugin content was 92 times higher than in stems in June. These findings suggest that the potential of the roots as a medicinal part. The roots were found to have highest purpurin content in October (2.406 mg g-1), whereas the mollugin content was highest in August (6.193 mg g-1). However, the purpurin content in August was only 0.029 mg g-1 lower than that in October, making August a suitable harvest period for R. cordifolia. The expression 1-deoxy-D-xylulose 5-phosphate synthase (dxs) and 1-deoxy-D-xylulose-5-phosphate reductorisomerase (dxr) genes in roots showed an upward trend. However, the expression level of dxr gene was significantly higher than dxs with the range of 60-518 times higher, indicating the important role of dxr gene. Through correlation and redundancy analyses, it was found that mollugin showed positive correlation with carbon contents and carbon-nitrogen ratio of aerial parts. Additionally, purpurin showed a positive correlation with the expression of both genes. As a result, mollugin is likely to be synthesized in the aerial parts and then stored in the roots, whereas purpurin might be synthesized in the stems and roots. These findings could provide cultivation guidelines for R. cordifolia.

Silencing of circ_002136 sensitizes gastric cancer to paclitaxel by targeting the miR-16-5p/HMGA1 axis

The dysregulated expression of circRNA in gastric cancer (GC) induces paclitaxel (Tax) resistance of cancer cells, which in turn affects disease progression and prognosis. Here, we sought to investigate the role and mechanism of circ_002136 in Tax-resistant GC. In this study, we found the enriched circ_002136 level and the declined miR-16-5p level in Tax-resistant GC tissues and cells. Biologically, knockdown of circ_002136 elevated the Tax sensitivity of Tax-resistant GC cells, inhibited the cell motility properties, and simultaneously drove the apoptosis. Mechanically, circ_002136 promoted the HMGA1-mediated cellular Tax resistance and cell invasion by sponging miR-16-5p. Furthermore, circ_002136 silencing impeded the growth of Tax-resistant GC tumors in vivo. Overall, our study revealed a novel signaling pathway that could be used for future clinical applications, namely the circ_002136/miR-16-5p/HMGA1 axis to regulate the Tax resistance of GC cells.

Biosynthetic Mechanisms of Secondary Metabolites Promoted by the Interaction Between Endophytes and Plant Hosts

Endophytes is a kind of microorganism resource with great potential medicinal value. The interactions between endophytes and host not only promote the growth and development of each other but also drive the biosynthesis of many new medicinal active substances. In this review, we summarized recent reports related to the interactions between endophytes and hosts, mainly regarding the research progress of endophytes affecting the growth and development of host plants, physiological stress and the synthesis of new compounds. Then, we also discussed the positive effects of multiomics analysis on the interactions between endophytes and their hosts, as well as the application and development prospects of metabolites synthesized by symbiotic interactions. This review may provide a reference for the further development and utilization of endophytes and the study of their interactions with their hosts.

Identification and Optimization of a Novel Taxanes Extraction Process from Taxus cuspidata Needles by High-Intensity Pulsed Electric Field

Taxanes are a series of natural compounds with great application potential in antitumor therapy, whereas the lack of efficient taxanes extraction methods significantly hinders the development of taxanes. The high-intensity pulsed electric field (PEF) is a novel technology used to extract bioactive ingredients from food and other natural products. However, the prospect of using PEF for taxanes extraction remains to be elucidated. Herein, we extracted taxanes from Taxus cuspidata via PEF and explored the effects of seven extraction conditions on the yields of target compounds. The Placket–Burman design (PBD) assay revealed that electric field strength, pulse number, and particle size are key factors for taxanes extraction. The response surface methodology (RSM) and back-propagation neural network conjugated with genetic algorithm (GA-BP) were further used to model and predict the optimal extraction conditions, and GA-BP exerted higher reliability, leading to a maximum extraction yield of 672.13 μg/g under electric field strength of 16 kV/cm, pulse number of 8, particle size of 160 meshes, solid–liquid ratio of 1:60, a single extraction, centrifugal speed of 8000 r/min, and flow rate of 7 mL/min, which was 1.07–1.84 folds that of control, solid–liquid extraction (SL), and ultrasonic extraction (US) groups. Additionally, the scanning electron microscopy (SEM) results indicated that the sample particles extracted by PEF method exhibited a coarser surface morphology. Thus, we present for the first time that PEF is feasible for the extraction of taxanes from Taxus cuspidata and highlight the application value of the PBD, RSM, and GA-BP models in parameters optimization during extraction process.

Characterization of lipid droplets from a Taxus media cell suspension and their potential involvement in trafficking and secretion of paclitaxel

Our paper describes the potential roles of lipid droplets of Taxus media cell suspension in the biosynthesis and secretion of paclitaxel and, therefore, highlights their involvement in improving its production. Paclitaxel (PTX) is a highly potent anticancer drug that is mainly produced using Taxus sp. cell suspension cultures. The main purpose of the current study is to characterize cellular LDs from T. media cell suspension with a particular focus on the biological connection of their associated proteins, the caleosins (CLOs), with the biosynthesis and secretion of PTX. A pure LD fraction obtained from T. media cells and characterized in terms of their proteome. Interestingly, the cellular LD in T. media sequester the PTX. This was confirmed in vitro, where about 96% of PTX (C⁰_PTX,_aq [mg L^-1]) in the aqueous solution was partitioned into the isolated LDs. Furthermore, silencing of CLO-encoding genes in the T. media cells led to a net decrease in the number and size of LDs. This coincided with a significant reduction in expression levels of TXS, DBAT and DBTNBT, key genes in the PTX biosynthesis pathway. Subsequently, the biosynthesis of PTX was declined in cell culture. In contrast, treatment of cells with 13-hydroperoxide C18:3, a substrate of the peroxygenase activity, induced the expression of CLOs, and, therefore, the accumulation of cellular LDs in the T. media cells cultures, thus increasing the PTX secretion. The accumulation of stable LDs is critically important for effective secretion of PTX. This is modulated by the expression of caleosins, a class of LD-associated proteins with a dual role conferring the structural stability of LDs as well as regulating lipidic bioactive metabolites via their enzymatic activity, thus enhancing the biosynthesis of PTX.

Biotransformation ability of endophytic fungi: from species evolution to industrial applications

Increased understanding of the interactions between endophytic fungi and plants has led to the discovery of a new generation of chemical compounds and processes between endophytic fungi and plants. Due to the long-term co-evolution between fungal endophytes and host plants, endophytes have evolved special biotransformation abilities, which can have critical consequences on plant metabolic processes and their composition. Biotransformation or bioconversion can impact the synthesis and decomposition of hormones, sugars, amino acids, vitamins, lipids, proteins, and various secondary metabolites, including flavonoids, polysaccharides, and terpenes. Endophytic fungi produce enzymes and various bioactive secondary metabolites with industrial value and can degrade or sequester inorganic and organic small molecules and macromolecules (e.g., toxins, pollutants, heavy metals). These fungi also have the ability to cause highly selective catalytic conversion of high-value compounds in an environmentally friendly manner, which can be important for the production/innovation of bioactive molecules, food and nutrition, agriculture, and environment. This work mainly summarized recent research progress in this field, providing a reference for further research and application of fungal endophytes. KEY POINTS: •The industrial value of degradation of endophytes was summarized. • The commercial value for the pharmaceutical industry is reviewed.

Recent Research Progress in Taxol Biosynthetic Pathway and Acylation Reactions Mediated by Taxus Acyltransferases

Taxol is one of the most effective anticancer drugs in the world that is widely used in the treatments of breast, lung and ovarian cancer. The elucidation of the taxol biosynthetic pathway is the key to solve the problem of taxol supply. So far, the taxol biosynthetic pathway has been reported to require an estimated 20 steps of enzymatic reactions, and sixteen enzymes involved in the taxol pathway have been well characterized, including a novel taxane-10β-hydroxylase (T10βOH) and a newly putative β-phenylalanyl-CoA ligase (PCL). Moreover, the source and formation of the taxane core and the details of the downstream synthetic pathway have been basically depicted, while the modification of the core taxane skeleton has not been fully reported, mainly concerning the developments from diol intermediates to 2-debenzoyltaxane. The acylation reaction mediated by specialized Taxus BAHD family acyltransferases (ACTs) is recognized as one of the most important steps in the modification of core taxane skeleton that contribute to the increase of taxol yield. Recently, the influence of acylation on the functional and structural diversity of taxanes has also been continuously revealed. This review summarizes the latest research advances of the taxol biosynthetic pathway and systematically discusses the acylation reactions supported by Taxus ACTs. The underlying mechanism could improve the understanding of taxol biosynthesis, and provide a theoretical basis for the mass production of taxol.