Identification of rate-limiting enzymes involved in paclitaxel biosynthesis pathway affected by coronatine and methyl-ß-cyclodextrin in Taxus baccata L. cell suspension cultures.

BACKGROUND: Paclitaxel is a potent antitumor alkaloid widely used for the treatment of several cancer types. This valuable secondary metabolite naturally exists in the inner bark of Taxus species in very low amounts. The small-scale production of paclitaxel in Taxus cell cultures requires utilization of several elicitors. OBJECTIVE: The main objective of this work was to identify key genes that encode rate-limiting enzymes in paclitaxel biosynthesis pathway by investigating the possible relationship between paclitaxel production and a set of 13 involved genes' relative expression in Taxus baccata L. cell suspension cultures affected by coronatine and methyl-ß-cyclodextrin. METHODS: In the present research, the most important key genes were identified using gene expression profiling evaluation and paclitaxel production assessment in Taxus baccata L. cell cultures affected by mentioned elicitors. RESULTS AND CONCLUSION: Gene expression levels were variably increased using methyl-ß-cyclodextrin, and in some cases, a synergistic effect on transcript accumulation was observed when culture medium was supplemented with both elicitors. It was revealed that DBAT, BAPT, and DBTNBT are the most important rate-limiting enzymes in paclitaxel biosynthesis pathway in Taxus baccata L. cell suspension cultures under coronatine and methyl-ß-cyclodextrin elicitation condition. Moreover, PAM was identified as one of the important key genes especially in the absence of ß-phenylalanine. In cell cultures affected by these elicitors, paclitaxel was found largely in the culture media (more than 90%). The secretion of this secondary metabolite suggests a limited feedback inhibition and reduced paclitaxel toxicity for producer cells. It is the result of the ABC gene relative expression level increment under methyl-ß-cyclodextrin elicitation and highly depends on methyl-ß-cyclodextrin's special property (complex formation with hydrophobic compounds). Paclitaxel biosynthesis was obviously increased due to the effect of coronatine and methyl-ß-cyclodextrin elicitation, leading to the production level of 5.62 times higher than that of the untreated cultures. Graphical abstract Rate Limiting Enzymes in Paclitaxel Biosynthesis Pathway: DBAT, BAPT, DBTNBT and PAM.

Pharmacognostic studies on Taxus baccata L.: A brilliant source of Anti-cancer agents.

The present investigation was undertaken to establish standardization profile of Taxus baccata L. with the help of pharmacognostic parameters, which is not done before. T. baccata(Taxaceae), is native to Europe, is an evergreen needle-leaved tree, growing up to 28 m high. A large number of phytochemicals like taxoids viz. taxusin, baccatin, baccatin, lignans, flavanoids, steroids, paclitaxel and sugar derivatives have been isolated from it. For the treatment of different types of cancer like ovarian and breast cancers, Kaposi's sarcoma and lung cancers Paclitaxel (taxol) has been approved. Paclitaxel is also under clinical trial for remedy of number of other cancers in combination with other chemotherapeutic medications. Pharmacognostical and preliminary phytochemical screening of T. baccata will be useful to authenticate and avoid adulteration in the raw material. The diagnostic microscopic characters, physiochemical data and FTIR will be useful in the development of monograph.

Transcript profiling of jasmonate-elicited Taxus cells reveals a ß-phenylalanine-CoA ligase.

Plant cell cultures constitute eco-friendly biotechnological platforms for the production of plant secondary metabolites with pharmacological activities, as well as a suitable system for extending our knowledge of secondary metabolism. Despite the high added value of taxol and the importance of taxanes as anticancer compounds, several aspects of their biosynthesis remain unknown. In this work, a genomewide expression analysis of jasmonate-elicited Taxus baccata cell cultures by complementary DNA-amplified fragment length polymorphism (cDNA-AFLP) indicated a correlation between an extensive elicitor-induced genetic reprogramming and increased taxane production in the targeted cultures. Subsequent in silico analysis allowed us to identify 15 genes with a jasmonate-induced differential expression as putative candidates for genes encoding enzymes involved in five unknown steps of taxane biosynthesis. Among them, the TB768 gene showed a strong homology, including a very similar predicted 3D structure, with other genes previously reported to encode acyl-CoA ligases, thus suggesting a role in the formation of the taxol lateral chain. Functional analysis confirmed that the TB768 gene encodes an acyl-CoA ligase that localizes to the cytoplasm and is able to convert ß-phenylalanine, as well as coumaric acid, into their respective derivative CoA esters. ß-phenylalanyl-CoA is attached to baccatin III in one of the last steps of the taxol biosynthetic pathway. The identification of this gene will contribute to the establishment of sustainable taxol production systems through metabolic engineering or synthetic biology approaches.

Plant natural products: history, limitations and the potential of cambial meristematic cells.

Humans have utilised plant derived natural products as medicines for millenia. Moreover, many contemporary pharmaceuticals are also natural products or derivatives thereof. However, the full potential of these compounds remains to be exploited because often they are: complex and difficult to synthesise; found in low quantities; produced by undomesticated and sometimes rare plants; and, their synthesis is routinely influenced by weather conditions. Potentially, the in vitro culture of cells from the corresponding plant species could circumvent some of these problems but the growth of plant cells on an industrial scale is also problematic. The recent isolation and culture of cambial meristematic cells (CMCs), stem cells which ordinarily generate the plant vasculature, may now provide a key platform technology to help realise the full potential of plant natural products.

Production of paclitaxel and the related taxanes by cell suspension cultures of Taxus species.

Medicinal plants are the most promising source for the development of drugs, and many types of active ingredients from the plant resources have been studied in order to clarify the relationship between the chemical structure and the activity. However, it is not easy to develop drugs from those active compounds, and in many cases, the supply of active compounds can have some problems: 1) limited quantity of active compounds in plant; 2) low plant growth rate; 3) the limited localization of active ingredients in the specific organs; and 4) from the perspective of the conservation of natural resources. Therefore, the stable supply of the compounds commercially is very difficult and contains risk hedge. Plant cell culture is an attractive technology to solve these problems by securing the stable supply of the active compounds without damage to the natural plant resources. Recently, an efficient production process of anticancer drug paclitaxel by Taxus cell suspension cultures was constructed. The established Taxus cell lines produced paclitaxel and related taxanes by specific external stimuli, such as methyl jasmonate. The time-course analysis revealed that there are two regulatory steps existing in the paclitaxel biosynthesis: the taxane-ring formation step that is up-regulated by MeJA, and the acylation step at the C-13 position. By applying the data from the two-stage culture and the high-density culture, a large-scale culture process was developed with a stable paclitaxel production in the range of 140-295 mg L(-1), reaching 295 mg L(-1) at maximum.

[LC-ESI-MS metabolic profiling analysis of taxanes from the extracts of Taxus chinensis cell cultures].

AIM: To develop a rapid analytical method for small amount biological samples of taxanes by using liquid chromatography coupled with electrospray ionization tandem mass spectrometry (LC-ESI-MS) in small amount biological samples. METHODS: A solution containing five given taxane constituents and the extract from cell cultures of Taxus chinensis were analysed separately. According to the performance of the given taxanes in ESI-MS/MS, run parameters of the mass spectrometer were optimized. Positive and negative electrospray modes were employed to simultaneously scan the cell cultures sample, and the full ion chromatogram and the molecular weight of individual peak were obtained. The qualitative analysis of taxanes was achieved by comparison of the retention time and molecular weight with those of the reference substances or was based on the interpretation of the MS/MS spectra of the analytes and the knowledge of the concerning genetic backgrounds of taxanes published in literatures. RESULTS: The taxanes with several acetyl substituents tended to produce ammonium adduct ions peak, while multi-hydroxy taxanes were subject to give protonized molecular ion peaks in positive ion ESI-MS. Thirteen taxanes in cell samples were assigned. Eight compounds of them were identified to be 1 -acetyl-5, 7, 10-deacetyl-baccatin I (DAB-I, 1) , baccatin III (B-III, 3), baccatin VI (B-VI, 8), taxol (9), yunnanxane (10 ), taxuyunnanine C (Tc, 11), sinenxane B (12), sinenxane C (13), separately. For the other five constituents, character of taxane and the number of substituents were deduced. CONCLUSION: The results confirm the feasibility of characterizing taxanes in biological samples by LC-ESI-MS analysis. The analytical methodology provided a rapid, conventional and reliable tool to study metabolic profiling of taxanes for structural elucidation in taxol biosynthesis.

[Isolation and identification of taxane from Taxus chinensis cell cultures].

OBJECTIVE: To study taxanes of the cell cultures of Taxus chinensis. METHODS: The cell cultures were extracted with 95% alcohol, distributed by different solvents, isolated via column chromatogaphy on silica gel by eluting with various proportions of petroleum ether-ethyl acetate and purified by crystallization with ethanol. RESULT: A taxane was isolated from the cell cultures of Taxus chinensis and its structure was identified as 2alpha,5alpha, 10beta, 14beta-tetraacetoxy-taxa-4 (20), 11-diene (Taxuyunnanine C) on the base of spectrum data. CONCLUSION: The compound was isolated from the cell cultures of Taxus chinensis for the first time.

Identification of a cDNA clone specific for the taxol synthesis phase of Taxus chinensis cells by mRNA differential display.

In order to identify genes related to Taxol biosynthesis, the mRNA differential display method was employed to compare mRNA populations from suspension cultured Taxus chinensis cells before and after beginning to produce Taxol. From a total display of about 4000 PCR products, 104 were derived from cells during the Taxol synthesis phase but not the non-Taxol synthesis phase. These products were cloned, and one such cDNA clone, named TS1, was confirmed to be specifically expressed in the Taxol synthesis phase by northern blot analysis. The length of the transcript corresponding TS1 was approximately 2.1 kb. DNA sequencing and homology search showed the sequence of TS1 contains a partial open reading frame and has no homologies with other known genes. Hence, this report demonstrated the potential of mRNA differential display for the isolation of genes specific for the period of secondary metabolite production as well as the feasibility of the approach for the identification of genes potentially related to the synthesis of secondary metabolites in higher plants.

[Study on anti-tumor activity of extracts from cultured cells of Taxus chinensis].

OBJECTIVE: To analyze the cytotoxicity and inhibitory effect of extracts from cultured cells(from stems) of Taxus chinensis on cancer cell line SMMC-7721. METHODS: MTT assay for cell viability and flow cytometry for cell cycle analysis. RESULTS: MTT results showed that the extact by dichloromethane was more effective than that by methanol on SMMC-7721, IC50 were 0.0834 mg DCW.ml-1 and 0.8002 mg DCW.ml-1 respectively. SMMC-7721 cells in G2-M stage increased with higher concentration of dichloromethane extracts from Taxus chinensis cells and longer incubation. CONCLUSION: Extracts from cultured cells of Taxus chinensis could have cytotoxic effect on SMMC-7721 and could induce apoptosis of cancer cells.

Effects of inoculum size and age on biomass growth and paclitaxel production of elicitor-treated Taxus yunnanensis cell cultures.

Suspension cultures of Taxus yunnanensis cells were inoculated with cells of different culture ages (12-24 days) at various densities [50-250 g fresh weight (fw)/l], and treated (on day 7) with a mixture of elicitors, including Ag(+), chitosan and methyl jasmonate. The biomass productivity (during the production stage) increased dramatically with inoculum size, but decreased with inoculum age over 16 days. The volumetric yield and productivity of taxol (paclitaxel) also increased with inoculum size, while the specific taxol yield (per cell) was mainly dependent on inoculum age, with an optimum of 20 days, during the early stationary phase. The highest taxol yield and productivity, 39.8 mg/l and 1.9 mg/l per day, respectively, were obtained with a 20-day-old inoculum at 200 g fw/l. Taxol excretion by the cells increased with inoculum age but decreased with inoculum size. The elicitor-induced activities of catalase (CAT) and phenylalanine ammonia-lyase (PAL) also depended mainly on inoculum age; higher PAL activity and lower CAT activity were obtained with an older inoculum, corresponding to a higher taxol yield. The results show that both inoculum size and age are important variables for taxol production, though the latter more profoundly influences elicitor-induced taxol biosynthesis of the cells. Inoculum size and age are also interrelated and should be optimized together in a two-stage culture process.

Jasmonic acid stimulates taxane production in cell suspension culture of yew (Taxus x media).

Cell lines of Taxus x media Rehd. were established via embryo and callus culture and grown on B5 medium containing 10 microM 2,4-D and 1 microM kinetin. Jasmonic acid (JA) was used to elicit taxane synthesis in a selected yew cell line. 100 microM JA was added 7 days after subculture. JA strongly increased taxane content in the cells and in the medium. At the time of the highest amount in elicited cultures, the enhancement of paclitaxel production was 19-fold and 4-fold in the cells and medium, respectively, compared to controls (non-elicited cultures). The time course of taxane accumulation in the cells and in the medium and the release of taxanes into the medium were not changed after JA elicitation.

Immunoaffinity chromatography for the sample pretreatment of Taxus plant and cell extracts prior to analysis of taxanes by high-performance liquid chromatography.

The application of immunoaffinity chromatography for the purification of Taxus plant and cell extracts prior to the HPLC analysis is described. Polyclonal antibodies raised against 10-deacetylbaccatin III (10-DAB III), paclitaxel's main precursor in plant, were characterised by enzymed-linked immunosorbent assay. Immunoglobulins from selected antisera were immobilised on CNBr-activated Sepharose 4B. The immunoaffinity column was used for the purification of plant and plant cell culture extracts prior to their analysis by HPLC. Immunoaffinity chromatography enabled the selective concentration of taxoids and enhanced sample clean-up.

Stimulation of taxol production and excretion in Taxus spp cell cultures by rare earth chemical lanthanum.

The trivalent ion of a rare earth element, lanthanum, was tested for elicitor-like effects on taxol production in suspension cultures of four different Taxus spp cells. In T. yunnanensis cell cultures, the lanthanum ion at concentrations from 1.15 to 23.0 microM stimulated taxol production. The lanthanum ion also promoted taxol excretion by the T. yunnanensis cells considerably. The maximum stimulation of taxol production was achieved by the addition of 5.8 microM La3+ to the culture during mid-log growth phase, increasing the volumetric taxol yield by nearly threefold, from 2.61+/-0.37 to 9.89+/-1.92 mg l(-1) over a 28 day culture period. At higher concentrations, i.e. 23.1 and 46.2 microM, however, the lanthanum ion caused significant growth inhibition. For the other three Taxus cell lines, namely an embryo and a leave cell of T. chinensis and a stem cell of T. chinensis marv, the addition of lanthanum ion to the culture only had a significant effect on taxol production by the T. chinensis marv stem cells, increasing the volumetric yield by about threefold to 4.69+/-0.76 mg l(-1). These results suggest that lanthanum has elicitor-like effects on secondary metabolite synthesis of plant cell cultures.

[Selection of high taxol content cell lines of Taxus yunnanensis Cheng et L. K. Fu].

OBJECTIVE: To select high taxol content cell lines of Taxus yunnanensis. METHOD: Choosing different cell aggregates according to their color, texture, growth rate and secretion of colorful substances, culturing them separately, and further analyzing their growth rates and taxolcontents. RESULT AND CONCLUSION: Cell lines with higher taxol contents could be obtained by careful selection; those with darker color, lower growth rate and higher ratio of dry cell weight vs. fresh cell weight usually has higher taxol contents.

Cell lines of Taxus species as source of the anticancer drug taxol.

Callus culture of Taxus baccata and Taxus x Media were induced using explants of young stems and female gametophyte. Culture conditions have been established for the cell suspension of the different callus cell lines. Callus were induced from Taxus baccata and Taxus x Media using Murashige and Skoog (MS) medium supplemented with different concentrations of 2,4 D (2,4-dichlorophenoxyacetic) and benzylaminopurine (BA). All the cultures grew slowly following the first subculture and the majority turned brown and ceased growth. The fast growing callus lines constituted a habituated callus lines (CFGTB; CFGTM; CSTB and CSTB). These callus lines were used to induce cell suspension in the best nutritional medium (1 mg/l 2,4-D and 0.1 mg/l BA). The callus exhibited levels of taxol ranging from 0.1 to 15 mg/Kg on a dry weight basis. Suspension cultures of Taxus baccata (CSTB and CFGTB) and Taxus x Media (CSTM and CFGTM) were maintained at 25 degrees C on a MS medium with two weeks transfers. The maximum taxol production for suspension cell was within the range 5 to 6 mg/l.

Cell lines of Taxus species as source of the anticancer drug taxol

Callus culture of Taxus baccata and Taxus x Media were induced using explants of young stems and female gametophyte. Culture conditions have been established for the cell suspension of the different callus cell lines. Callus were induced from Taxus baccata and Taxus x Media using Murashige and Skoog (MS) medium supplemented with different concentrations of 2,4 D (2,4-dichlorophenoxyacetic) and benzylaminopurine (BA). All the cultures grew slowly following the first subculture and the majority turned brown and ceased growth. The fast growing callus lines constituted a habituated callus lines (CFGTB; CFGTM; CSTB and CSTB). These callus lines were used to induce cell suspension in the best nutritional medium (1 mg/l 2,4-D and 0.1 mg/l BA). The callus exhibited levels of taxol ranging from 0.1 to 15 mg/Kg on a dry weight basis. Suspension cultures of Taxus baccata (CSTB and CFGTB) and Taxus x Media (CSTM and CFGTM) were maintained at 25 degrees C on a MS medium with two weeks transfers. The maximum taxol production for suspension cell was within the range 5 to 6 mg/l.(AU)

The configuration of methyl jasmonate affects paclitaxel and baccatin III production in Taxus cells.

All stereoisomers of methyl jasmonate (MJA) were prepared, and their effects on cell yield and promotion of paclitaxel (Taxol) and baccatin III production investigated in cell suspension cultures of Taxus media. (3R,7S)-MJA showed the strongest cell growth inhibition, followed by (3R,7R)-MJA. In contrast, (3S,7R)- and (3S,7S)-MJA had very low inhibitory effects, indicating that this inhibition depends largely on the (3R)-configuration. In terms of the promotion of paclitaxel and baccatin III production, (3R,7R)-MJA had the highest activity. Although it showed considerable activity at low concentration, at higher concentrations the activity was decreased due to strong inhibition of cell growth. Interestingly, paclitaxel and baccatin III contents increased even at a high (3S,7R)-MJA concentration, whereas the other isomers had the opposite effects. These findings are interpreted to suggest that the optimum configuration is (3R,7R), the (3R)-configuration not being indispensable, and that the (7R)-configuration is suitable for the promotion of paclitaxel and baccatin III production.

Kinetic studies of paclitaxel production by Taxus canadensis cultures in batch and semicontinuous with total cell recycle.

Suspension cultures of Taxus canadensis were elicited with methyl jasmonate (MJ) under defined headspace ethylene concentrations. Kinetic studies of growth, nutrient consumption, pH variation, and paclitaxel accumulation were conducted in batch cultures and semicontinuous culture with total cell recycle. A dramatic increase of paclitaxel was obtained when the cultures were elicited with 100 microM MJ, but cell growth was thereby arrested. Supplementation of acetyl-CoA and MJ to the culture proved to be another way to improve paclitaxel yields. Using semicontinuous culture with total cell recycle, paclitaxel accumulation was increased by a factor of 4.0 relative to that in the batch culture during 35 days of cultivation.

[Effects of phenylalanine, sucrose and mannitol on the growth and production of taxol, baccatin III and 10-deacetylbaccatin III in suspension cells of Taxus media].

The effects of phenylalanine, sucrose and mannitol on the cell growth and the production of taxol, baccatin III and 10-deacetylbaccatin III in the suspension cells of Taxus media were studied. The results showed that phenylalanine 1.0 mmol.L-1 or 2.0 mmol.L-1 initially added into the medium, and sucrose 73.0 mmol.L-1 and mannitol 173.3 mmol.L-1 added into the medium at the 28th d of culture strongly promoted the cell growth and the formation of the three taxanes in the suspension cells. Compared with those of the control, the cell biomass of the treatments supplemented with phenylalanine and added with sucrose and mannitol at the 28th d of culture increased by 0.6-0.8-fold, taxol yield by 9-10-fold, baccatin III yield by 2.5-3.0-fold, and 10-deacetylbaccatin III yield by 7-fold. Addition of sucrose 73.0 mmol.L-1 at the 28th d of culture significantly promoted the cell growth, but showed little effect on the contents of the three taxanes in the suspension cultures.

[Cell clone technique for Taxus cuspidata Sieb. et Zuicc].

The cell clone technique was studied for Taxus cuspidata with needle-derived calli cells. The plating efficiency(PE) of the third generation of suspension culture cells was found to be the highest one and the PE of the medium solidified with phytagel was found to be almost the same as that of the medium solidified with low melting agarose gel. Solid-solid double layer culture was found to promote the PE of Taxus cuspidata cells moderately. A large number of stable cell lines with high growth rate were obtained and the browning problem of cells was completely solved via plate culture of the cell clones of T. cuspidata. The growth rate of the best cell line reached 0.4 g.FW/g.FW.d.