Paclitaxel is an anticancer natural product with several biomedical applications produced by Taxus species, with a demand exceeding its supply. We have developed cambial meristematic cells (CMCs) from Taxus cuspidata as high yield source of paclitaxel. The biosynthesis of paclitaxel is predominantly under transcriptional control. Thus, the identification of transcriptional regulators of paclitaxel biosynthesis and their subsequent manipulation may enable further yield enhancement in Taxus CMCs. Previously, Roche 454 sequencing was employed to establish the transcriptome of T. cuspidata CMCs treated with the plant immune activator methyl jasmonate (MeJA). The bioinformatic analysis identified 19 jasmonate related transcription factors (TFs), based on their differential expression. Results of the Arabidopsis thaliana transient assay screen identified two MYB TFs that constitute positive regulators for paclitaxel genes, named MYB3 and MYB4. In this thesis, MYB3 and MYB4 showed in vitro binding to the cis-elements in ten promoters of paclitaxel genes using the electrophoretic mobility shift assay (EMSA). Then, a Taxus CMC protoplasts transient assay demonstrated that the expression of MYB3 and MYB4 trans-activated all tested genes. Further, MYB4 was found to activate the 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) gene, key in the mevalonate pathway and precursor of paclitaxel biosynthesis. MYB3 and MYB4 were capable of auto-regulating their own transcription, constituting an important control point for paclitaxel biosynthesis. A possible mechanism for the early activation of MYB3 and MYB4 after MeJA elicitation is proposed. Finally, preliminary results on the expression of MYB3 and MYB4 in unelicited T. baccata CMC protoplasts indicate that their transient expression was sufficient to increase accumulation of paclitaxel and the precursor, 10-deacetyl baccatin III, highlighting their utility for paclitaxel production.

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A biodiversidade de plantas brasileiras é uma fonte muito rica de moléculas bioativas, dentro da proposta da busca por novas drogas antitumorais, avaliamos neste estudo o potencial antiproliferativo do composto 7-epi-clusianona. Foram utilizadas duas linhagens celulares derivadas de tumor de mama humana, Hs 578T e MCF-7, cultivadas em monocamada e como esferoides. O IC50 após 48 horas de tratamento das células é de 20 μM para Hs 578T e 6 μM para MCF-7. A análise do ciclo celular mostrou que o composto é capaz de reter as células em fase G1/G0 em ambas as linhagens em 2D, mas não em 3D. O composto é capaz de induzir as células a senescência celular, como mostrado pelo ensaio de detecção de β-galactosidase. Esses dados indicam que o composto 7-epi-clusianona é uma molécula promissora, que demonstrou potencial antitumoral em células de tumor de mama. A cultura tridimensional se mostrou mais resistente ao tratamento com 7-epi-clusianona, portanto estudos mais abrangentes são necessários para melhor entendimento dos efeitos do composto sobre esse tipo de cultura. / Brazilian flora is considered one of the most diverse in the world and natural products are some of the important sources of new antitumoral compounds. The aim of this study was to evaluate the antiproliferative potential of 7-epi-clusianone. Two cell lines derived from human breast tumor were used, Hs 578T and MCF-7, cultured in monolayer and as spheroids. The IC50 after 48 hours of treatment is 20 μM to Hs 578T cells and 6 μM to MCF-7 cells. Cell cycle analysis showed induction of cell cycle arrest in G1/S phase in cells cultured in monolayers, but not in spheroids. The amount of cells in senescence after the treatment with 7-epi-clusianone is higher than the control group, as seen by the senescence β-galactosidase staining assay. These data suggest that 7-epi-clusianone is a promising molecule against breast cancer cells. We show that 3D culture was more resistant to treatment than 2D culture, therefore more comprehensive studies are needed to better understand the effects of 7-epi-clusianone on this kind of culture.

A biodiversidade de plantas brasileiras é uma fonte muito rica de moléculas bioativas, dentro da proposta da busca por novas drogas antitumorais, avaliamos neste estudo o potencial antiproliferativo do composto 7-epi-clusianona. Foram utilizadas duas linhagens celulares derivadas de tumor de mama humana, Hs 578T e MCF-7, cultivadas em monocamada e como esferoides. O IC50 após 48 horas de tratamento das células é de 20 μM para Hs 578T e 6 μM para MCF-7. A análise do ciclo celular mostrou que o composto é capaz de reter as células em fase G1/G0 em ambas as linhagens em 2D, mas não em 3D. O composto é capaz de induzir as células a senescência celular, como mostrado pelo ensaio de detecção de β-galactosidase. Esses dados indicam que o composto 7-epi-clusianona é uma molécula promissora, que demonstrou potencial antitumoral em células de tumor de mama. A cultura tridimensional se mostrou mais resistente ao tratamento com 7-epi-clusianona, portanto estudos mais abrangentes são necessários para melhor entendimento dos efeitos do composto sobre esse tipo de cultura. / Brazilian flora is considered one of the most diverse in the world and natural products are some of the important sources of new antitumoral compounds. The aim of this study was to evaluate the antiproliferative potential of 7-epi-clusianone. Two cell lines derived from human breast tumor were used, Hs 578T and MCF-7, cultured in monolayer and as spheroids. The IC50 after 48 hours of treatment is 20 μM to Hs 578T cells and 6 μM to MCF-7 cells. Cell cycle analysis showed induction of cell cycle arrest in G1/S phase in cells cultured in monolayers, but not in spheroids. The amount of cells in senescence after the treatment with 7-epi-clusianone is higher than the control group, as seen by the senescence β-galactosidase staining assay. These data suggest that 7-epi-clusianone is a promising molecule against breast cancer cells. We show that 3D culture was more resistant to treatment than 2D culture, therefore more comprehensive studies are needed to better understand the effects of 7-epi-clusianone on this kind of culture.