Bimodal effects on lipid droplets induced in cancer and non-cancer cells by chemotherapy drugs as revealed with a green-emitting BODIPY fluorescent probe.

Lipid droplets (LDs) are cytoplasmic lipid-rich organelles with important roles in lipid storage and metabolism, cell signaling and membrane biosynthesis. Additionally, multiple diseases, such as obesity, fatty liver, cardiovascular diseases and cancer, are related to the metabolic disorders of LDs. In various cancer cells, LD accumulation is associated with resistance to cell death, reduced effectiveness of chemotherapeutic drugs, and increased proliferation and aggressiveness. In this work, we present a new viscosity-sensitive, green-emitting BODIPY probe capable of distinguishing between ordered and disordered lipid phases and selectively internalising into LDs of live cells. Through the use of fluorescence lifetime imaging microscopy (FLIM), we demonstrate that LDs in live cancer (A549) and non-cancer (HEK 293T) cells have vastly different microviscosities. Additionally, we quantify the microviscosity changes in LDs under the influence of DNA-damaging chemotherapy drugs doxorubicin and etoposide. Finally, we show that doxorubicin and etoposide have different effects on the microviscosities of LDs in chemotherapy-resistant A549 cancer cells.

DNA Damage Response After Treatment of Cycling and Quiescent Cord Blood Hematopoietic Stem Cells With Distinct Genotoxic Noxae.

Hematopoietic stem cells (HSC) from cord blood can be applied as an alternative to bone marrow in transplantation to treat hematological diseases. Umbilical cord blood (UCB) consists of cycling and non-cycling CD34+/CD45low cells needed for long-term and short-term engraftment. After sorting and subsequent in vitro culture, quiescent HSCs enter the cell cycle. This enables the analysis of HSCs in 2 different cell cycle stages and the comparison of their responses to different genotoxic noxae. To analyze different mechanisms of DNA damage induction in cells, 2 different genotoxins were compared: etoposide, a topoisomerase II inhibitor that targets mitosis in the S/G2-phase of the cell cycle and the alkylating nitrosamine N-Nitroso-N-methylurea (MNU), which leads to the formation of methyl DNA adducts resulting in DNA double breaks during DNA replication and persistent mutations. Cycling cells recovered after treatment even with higher concentrations of etoposide (1.5µM/ 5µM/10µM), while sorted cells treated with MNU (0.1mM/0.3mM/0.5mM/1mM/3Mm/ 5mM) recovered after treatment with the lower MNU concentrations whereas high MNU concentrations resulted in apoptosis activation. Quiescent cells were not affected by etoposide treatment showing no damage upon entry into the cell cycle. Treatment with MNU, similarly to the cycling cells, resulted in a dose-dependent cell death. In conclusion, we found that depending on the genotoxic trigger and the cycling status, CD34+cells have distinct responses to DNA damage. Cycling cells employ both DDR and apoptosis mechanisms to prevent damage accumulation. Quiescent cells predominantly undergo apoptosis upon damage, but their cell cycle status protects them from certain genotoxic insults.

Multiparametric analysis of etoposide exposed mesenchymal stem cells and Fanconi anemia cells: implications in development of secondary myeloid malignancy.

Secondary acute myeloid leukemia (sAML) may develop following a prior therapy or may evolve from an antecedent hematological disorder such as Fanconi Anemia (FA). Pathophysiology of leukemic evolution is not clear. Etoposide (Eto) is a chemotherapeutic agent implicated in development of sAML. FA is an inherited bone marrow (BM) failure disease characterized by genomic instability and xenobiotic susceptibility. Here, we hypothesized that alterations in the BM niche may play a critical/driver role in development of sAML in both conditions. Expression of selected genes involved in xenobiotic metabolism, DNA double-strand break response, endoplasmic reticulum (ER) stress, heat shock response and cell cycle regulation were determined in BM mesenchymal stem cells (MSCs) of healthy controls and FA patients at steady state and upon exposure to Eto at different concentrations and in recurrent doses. Expression of CYPA1, p53, CCNB1, Dicer1, CXCL12, FLT3L and TGF-Beta genes were significantly downregulated in FA-MSCs compared with healthy controls. Eto exposure induced significant alterations in healthy BM-MSCs with increased expression of CYP1A1, GAD34, ATF4, NUPR1, CXCL12, KLF4, CCNB1 and nuclear localization of Dicer1. Interestingly, FA-MSCs did not show significant alterations in these genes upon Eto exposure. As opposed to healthy MSCs DICER1 gene expression and intracellular localization was not altered on FA BM-MSCs after Eto treatment. These results showed that Eto is a highly potent molecule and has pleiotropic effects on BM-MSCs, FA cells show altered expression profile compared to healthy controls and Eto exposure on FA cells shows differential profile than healthy controls.

Etoposide-Entrapped Progesterone-Cationic Lipid Nanoaggregates as Selective Therapeutics against Etoposide-Resistant Colorectal Cancer Cells.

Drug resistance has a major impact on the treatment of several cancers. This is mainly due to the overexpression of cellular drug efflux proteins. Hence, drug-delivery systems that can avoid this resistance are needed. We report PR10, a progesterone-cationic lipid conjugate, as a self-assembling nanoaggregate that delivers a drug cargo of etoposide, a topoisomerase inhibitor, selectively to cancer cells. In this study, we observed that etoposide nanoaggregates (P : E) caused selective and enhanced toxicity in etoposide-resistant CT26 cancer cells (IC50 9 µM) compared to when etoposide (IC50 >20 µM) was used alone. Concurrently, no toxicity was observed in etoposide-sensitive HEK293 cells for P : E treatment (IC50 >20 µM). The P : E-treated cancer cells seem to have no effect on ABCB1 expression, but etoposide-treated cells exhibited a twofold increase in ABCB1 expression, a potent efflux protein for several xenobiotic compounds. This observation supports the notion that the enhanced toxicity of P : E nanoaggregates is due to their ability to keep the expression of ABCB1 low, thus allowing longer intracellular residence of etoposide. In a BALB/c orthotopic colorectal cancer model, the nanoaggregates led to enhanced survival (45 days) compared to etoposide-treated mice (39 days). These findings suggest that PR10 could be used as a potential cancer-selective etoposide delivery vehicle to treat several etoposide-resistant cancers with fewer side effects due to the nonspecific toxicity of the drug.

Development of a synthetic transcription factor-based S-adenosylmethionine biosensor in Saccharomyces cerevisiae.

S-Adenosylmethionine (SAM) is a crucial small-molecule metabolite widely used in food and medicine. The development of high-throughput biosensors for SAM biosynthesis can significantly improve the titer of SAM. This paper constructed a synthetic transcription factor (TF)-based biosensor for SAM detecting in Saccharomyces cerevisiae. The synthetic TF, named MetJ-hER-VP16, consists of an Escherichia coli-derived DNA-binding domain MetJ, GS linker, the human estrogen receptor binding domain hER, and the viral activation domain VP16. The synthetic biosensor is capable of sensing SAM in a dose-dependent manner with fluorescence as the output. Additionally, it is tightly regulated by the inducer SAM and ß-estradiol, which means that the fluorescence output is only available when both are present together. The synthetic SAM biosensor could potentially be applied for high-throughput metabolic engineering and is expected to improve SAM production.

Transcriptional Reactivation of Lignin Biosynthesis for the Heterologous Production of Etoposide Aglycone in Nicotiana benthamiana.

Nicotiana benthamiana is a valuable plant chassis for heterologous production of medicinal plant natural products. This host is well suited for the processing of organelle-localized plant enzymes, and the conservation of the primary metabolism across the plant kingdom often provides required plant-specific precursor molecules that feed a given pathway. Despite this commonality in metabolism, limited precursor supply and/or competing host pathways can interfere with yields of heterologous products. Here, we use transient transcriptional reprogramming of endogenous N. benthamiana metabolism to drastically improve flux through the etoposide pathway derived from the medicinal plant Podophyllum spp. Specifically, coexpression of a single lignin-associated transcription factor, MYB85, with pathway genes results in unprecedented levels of heterologous product accumulation in N. benthamiana leaves: 1 mg/g dry weight (DW) of the etoposide aglycone, 35 mg/g DW (-)-deoxypodophyllotoxin, and 3.5 mg/g DW (-)-epipodophyllotoxin─up to two orders of magnitude above previously reported biosynthetic yields for the etoposide aglycone and eight times higher than what is observed for (-)-deoxypodophyllotoxin in the native medicinal plant. Unexpectedly, transient activation of lignin metabolism by transcription factor overexpression also reduces the production of undesired side products that likely result from competing N. benthamiana metabolism. Our work demonstrates that synthetic activation of lignin biosynthesis in leaf tissue is an effective strategy for optimizing the production of medicinal compounds derived from phenylpropanoid precursors in the plant chassis N. benthamiana. Furthermore, our results highlight the engineering value of MYB85, an early switch in lignin biosynthesis, for on-demand modulation of monolignol flux and support the role of MYB46 as a master regulator of lignin polymer deposition.

Ameliorative potential role of Rosmarinus officinalis extract on toxicity induced by etoposide in male albino rats.

The present work was showed to assess the effect of administration of rosemary extract on etoposide-induced toxicity, injury and proliferation in male rats were investigated. Forty male albino rats were arranged into four equal groups. 1st group, control; 2nd group, etoposide; 3rd group, co-treated rosemary & etoposide; 4th group, rosemary alone. In comparison to the control group, etoposide administration resulted in a significant increase in serum ALT, AST, ALP, total bilirubin, total protein, and gamma GT. In contrast; a significant decrease in albumin level in etoposide group as compared to G1. G3 revealed a significant decrease in AST, ALT, ALP, total protein and total bilirubin levels and a significant rise in albumin level when compared with G2. Serum levels of urea, creatinine, potassium ions, and chloride ions significantly increased; while sodium ions were significantly decreased in G2 when compared with G1. Also, there was an increase of MDA level for etoposide treated group with corresponding control rats. However, there was a remarkable significant decrease in SOD, GPX and CAT levels in G2 as compared to G1. There was a significant increase in serum hydrogen peroxide (H2O2) and Nitric oxide (NO) levels in group treated with etoposide when compared to control group. It was noticeable that administrated by rosemary alone either with etoposide had not any effect on the levels of H2O2 and Nitric oxide. Serum level of T3 and T4 was significantly increased in etoposide-administered rats in comparison with G1. The administration of rosemary, either alone or with etoposide, increased the serum levels of T3 and T4 significantly when compared to control rats. The gene expression analysis showed significant downregulation of hepatic SOD and GPx in (G2) when compared with (G1). The treatment with rosemary extract produced significant upregulation of the antioxidant enzymes mRNA SOD and GPx. MDA gene was increased in (G2) when contrasted with (G1). Treatment of the etoposide- induced rats with rosemary extract delivered significant decrease in MDA gene expression when compared with etoposide group. Rats treated with etoposide showed significant decline in hepatic Nrf2 protein expression, when compared with G1. While, supplementation of Etoposide- administered rats with the rosemary produced a significant elevation in hepatic Nrf2 protein levels. Additionally, the liver histological structure displayed noticeable degeneration and cellular infiltration in liver cells. It is possible to infer that rosemary has a potential role and that it should be researched as a natural component for etoposide-induced toxicity protection.

DNA Damage Increases Secreted Aß40 and Aß42 in Neuronal Progenitor Cells: Relevance to Alzheimer's Disease.

BACKGROUND: Recent studies suggest a strong association between neuronal DNA damage, elevated levels of amyloid-ß (Aß), and regions of the brain that degenerate in Alzheimer's disease (AD). OBJECTIVE: To investigate the nature of this association, we tested the hypothesis that extensive DNA damage leads to an increase in Aß40 and Aß42 generation. METHODS: We utilized an immortalized human neuronal progenitor cell line (NPCs), ReN VM GA2. NPCs or 20 day differentiated neurons were treated with hydrogen peroxide or etoposide and allowed to recover for designated times. Sandwich ELISA was used to assess secreted Aß40 and Aß42. Western blotting, immunostaining, and neutral comet assay were used to evaluate the DNA damage response and processes indicative of AD pathology. RESULTS: We determined that global hydrogen peroxide damage results in increased cellular Aß40 and Aß42 secretion 24 h after treatment in ReN GA2 NPCs. Similarly, DNA double strand break (DSB)-specific etoposide damage leads to increased Aß40 and Aß42 secretion 2 h and 4 h after treatment in ReN GA2 NPCs. In contrast, etoposide damage does not increase Aß40 and Aß42 secretion in post-mitotic ReN GA2 neurons. CONCLUSION: These findings provide evidence that in our model, DNA damage is associated with an increase in Aß secretion in neuronal progenitors, which may contribute to the early stages of neuronal pathology in AD.

Characterization of Induction and Targeting of Senescent Mesenchymal Stromal Cells.

Mesenchymal stromal cells (MSCs) from older donors have limited potential for bone tissue formation compared with cells from younger donors, and cellular senescence has been postulated as an underlying cause. There is a critical need for methods to induce premature senescence to study this phenomenon efficiently and reproducibly. However, the field lacks consensus on the appropriate method to induce and characterize senescence. Moreover, we have a limited understanding of the effects of commonly used induction methods on senescent phenotype. To address this significant challenge, we assessed the effect of replicative, hydrogen peroxide, etoposide, and irradiation-induced senescence on human MSCs using a battery of senescent cell characteristics. All methods arrested proliferation and resulted in increased cell spreading compared with low passage controls. Etoposide and irradiation increased expression of senescence-related genes in MSCs at early time points, proinflammatory cytokine secretion, DNA damage, and production of senescence-associated ß-galactosidase. We then evaluated the effect of fisetin, a flavonoid and candidate senolytic agent, to clear senescent cells and promote osteogenic differentiation of MSCs entrapped in gelatin methacryloyl (GelMA) hydrogels in vitro. When studying a mixture of nonsenescent and senescent MSCs, we did not observe decreases in senescent markers or increases in osteogenesis with fisetin treatment. However, the application of the same treatment toward a heterogeneous population of human bone marrow-derived cells entrapped in GelMA decreased senescent markers and increased osteogenesis after 14 days in culture. These results identify best practices for inducing prematurely senescent MSCs and motivate the need for further study of fisetin as a senolytic agent. Impact Statement The accumulation of senescent cells within the body has detrimental effects on tissue homeostasis. To study the role of senescent cells on tissue repair and regeneration, there is a need for effective means to induce premature cell senescence. Herein, we characterized the influence of common stressors to induce premature senescence in human mesenchymal stromal cells (MSCs). Irradiation of MSCs resulted in a phenotype most similar to quiescent, high-passage cells. These studies establish key biomarkers for evaluation when studying senescent cells in vitro.

Cytotoxic Action of Palladium-Based Compound on Prostate Stem Cells, Primary Prostate Epithelial Cells, Prostate Epithelial Cells, and Prostate Cell Lines.

Objective: Prostate cancer is one of the most common types of cancer found to occur in males and is ranked as the second-highest cause of cancer-associated deaths among male patients. In this study, we have shown the influence of a new palladium-based anticancer agent in contrast to the six distinct prostate cancer lines and the primary cultures. Methods: In this study, we have used six distinct prostate cell lines, that is, PNT2-C2, LNCaP, BPH-1, PC-3, PNT1A, and P4E6. The MTP and ATP assay were performed to evaluate the growth of the cell and the flow cytometry to investigate the status of the cell cycle. The antigrowth effect of the palladium complex was evaluated against different cell lines at three time zones 24 h, 48 h, and 72 h. [PdCl(terpy)] (capsule)-2H2O is synthesized by direct encapsulation of equimolar amounts of capsule ions into [Pd (terpy) Cl] Cl-2H2O. Results: A comparative analysis was done on 25 mM etoposide and 12 mM cisplatin, cytotoxic agents. The lowest IC50 value at 72 hours was 0.128 mM for BPH-1 cell lines with 0.139 mM, whereas PNT2-C2 cells were found to be most resistant with IC50 values of 0.829 mM. The antigrowth effect of palladium complex on cell lines was measured using the MTS assay at 24, 48, and 72 hours. BPH-1, PNT2-C2, and PNT1A either possess normal tissues or have benign prostatic hyperplasia tissues whereas P4E6, PC-3, and LNCaP cell lines possess malignant origin. The Pd complex exhibited significant cytotoxic action in stem cells when compared against etoposide. An antigrowth effect was reported for Pd complex at lower concentration, but it was more cytotoxic than etoposide with significant cytotoxicity (P=0.001). Conclusion: The palladium complex experienced a substantial antigrowth influence over most of the prostate tumor cell lines and the primary cultures, eventually, leading to the implementation of this Pd complex in the treating procedure of metastatic prostate cancer, which is tremendously resistant to the traditional treatment.

Comparative study of the ameliorative effects of omega-3 versus selenium on etoposide-induced changes in Sertoli cells and ectoplasmic specialization of adult rat testes: immunohistochemical and electron microscopic study.

Etoposide (Eto) is an anti-cancer drug that is associated with serious adverse effects on male reproductive function. Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) and selenium (Se) are known as anti-inflammatory, anti-apoptotic and anti-oxidant agents. This work was designed to investigate changes in the biochemical parameters as well as alterations in Sertoli cell vimentin expression, ultrastructure and ectoplasmic specializations (ESs) following Eto treatment and to assess the ameliorative effect of ω-3 versus Se on these alterations. Eighty four adult male albino rats were used and classified into four groups: group I (control group), group II (Eto group) received Eto in a single intra-peritoneal (IP) dose (60 mg/kg B.W.), group III (Eto & ω-3 group) received the single IP dose of Eto as well as ω-3 (300 mg/kg B.W./day by intra-gastric intubation) starting 5 days before Eto injection till the time of sacrifice & group IV (Eto & Se group) received the single IP dose of Eto as well as Se (0.5 mg/kg B.W./day IP) starting 5 days before Eto injection till the time of sacrifice. The rats were subdivided into 2 subgroups (a) and (b) that were sacrificed 3 and 7 days after Eto injection respectively. Eto administration in group II induced increase in malondialdehyde (MDA), decrease in superoxide dismutase (SOD), collapse of Sertoli cell vimentin filaments and ultrastructural degenerative changes in both Sertoli cells and ESs. Se (group IV) reversed Eto toxic effects potently, while ω-3 (group III) had some limited protective effects.

Induction of Cellular Senescence in Rat Vaginal Fibroblasts and Treatment With Senolytics: An in Vitro Model for the Study of Pelvic Organ Prolapse.

OBJECTIVE: The objective of this study was to develop an in vitro model of cellular senescence using rat vaginal fibroblasts and determine the effects of treatment with senolytics. METHODS: Rat vaginal tissue biopsies were collected. Primary vaginal fibroblasts were isolated and characterized by immunofluorescence. To induce cellular senescence, fibroblasts were treated with etoposide at 3, 10, and 20 mM for 24 hours, followed by treatment with the senolytics dasatinib (1 mM) and/or quercetin (20 mM). After treatment, RNA was extracted and the expression of selected genes was quantified. Immunostaining of senescence markers was also performed. RESULTS: Fibroblasts were confirmed by positive immunostaining for α-smooth muscle actin and vimentin, and negative immunostaining for pan-cytokeratin. Treatment with etoposide resulted in a dose-dependent increase in expression of the senescence-associated secretory phenotype markers MMP-7, MMP-9, and IL-b1 (P < 0.05) compared with controls. Immunostaining showed increased expression of γ-H2A and p21 after treatment with etoposide. Cells treated with dasatinib and quercetin after etoposide treatment had decreased expression of p21, MMP-7, MMP-9, and IL-1b compared with cells treated only with etoposide (P < 0.05). CONCLUSIONS: Upregulation of senescence-associated factors provided evidence that senescence can be induced in vaginal fibroblasts in vitro. Furthermore, treatment with the senolytics dasatinib and quercetin abrogated the senescence phenotype induced by etoposide in rat vaginal fibroblasts. Our findings provide a novel model for the study and development of new therapies targeting the disordered extracellular matrix associated with pelvic organ prolapse.

Etoposide and olaparib polymer-coated nanoparticles within a bioadhesive sprayable hydrogel for post-surgical localised delivery to brain tumours.

Glioblastoma is a malignant brain tumour with a median survival of 14.6 months from diagnosis. Despite maximal surgical resection and concurrent chemoradiotherapy, reoccurrence is inevitable. To try combating the disease at a stage of low residual tumour burden immediately post-surgery, we propose a localised drug delivery system comprising of a spray device, bioadhesive hydrogel (pectin) and drug nanocrystals coated with polylactic acid-polyethylene glycol (NCPPs), to be administered directly into brain parenchyma adjacent to the surgical cavity. We have repurposed pectin for use within the brain, showing in vitro and in vivo biocompatibility, bio-adhesion to mammalian brain and gelling at physiological brain calcium concentrations. Etoposide and olaparib NCPPs with high drug loading have shown in vitro stability and drug release over 120 h. Pluronic F127 stabilised NCPPs to ensure successful spraying, as determined by dynamic light scattering and transmission electron microscopy. Successful delivery of Cy5-labelled NCPPs was demonstrated in a large ex vivo mammalian brain, with NCPP present in the tissue surrounding the resection cavity. Our data collectively demonstrates the pre-clinical development of a novel localised delivery device based on a sprayable hydrogel containing therapeutic NCPPs, amenable for translation to intracranial surgical resection models for the treatment of malignant brain tumours.

A Novel Cytotoxic Conjugate Derived from the Natural Product Podophyllotoxin as a Direct-Target Protein Dual Inhibitor.

Natural products are the ideal basis for the design of novel efficient molecular entities. Podophyllotoxin, a naturally occurring cyclolignan, is an example of natural product which displays a high versatility from a biological activity point of view. Based on its unique chemical structure, different derivatives have been synthesized presenting the original antitumoral properties associated with the compound, i.e., the tubulin polymerization inhibition and arising anti-topoisomerase II activity from structural modifications on the cyclolignan skeleton. In this report, we present a novel conjugate or hybrid which chemically combines both biological activities in one single molecule. Chemical design has been planned based in our lead compound, podophyllic aldehyde, as an inhibitor of tubulin polymerization, and in etoposide, an approved antitumoral drug targeting topoisomerase II. The cytotoxicity and selectivity of the novel synthetized hybrid has been evaluated in several cell lines of different solid tumors. In addition, these dual functional effects of the novel compound have been also evaluated by molecular docking approaches.

Pausing sites of RNA polymerase II on actively transcribed genes are enriched in DNA double-stranded breaks.

DNA double-stranded breaks (DSBs) are strongly associated with active transcription, and promoter-proximal pausing of RNA polymerase II (Pol II) is a critical step in transcriptional regulation. Mapping the distribution of DSBs along actively expressed genes and identifying the location of DSBs relative to pausing sites can provide mechanistic insights into transcriptional regulation. Using genome-wide DNA break mapping/sequencing techniques at single-nucleotide resolution in human cells, we found that DSBs are preferentially located around transcription start sites of highly transcribed and paused genes and that Pol II promoter-proximal pausing sites are enriched in DSBs. We observed that DSB frequency at pausing sites increases as the strength of pausing increases, regardless of whether the pausing sites are near or far from annotated transcription start sites. Inhibition of topoisomerase I and II by camptothecin and etoposide treatment, respectively, increased DSBs at the pausing sites as the concentrations of drugs increased, demonstrating the involvement of topoisomerases in DSB generation at the pausing sites. DNA breaks generated by topoisomerases are short-lived because of the religation activity of these enzymes, which these drugs inhibit; therefore, the observation of increased DSBs with increasing drug doses at pausing sites indicated active recruitment of topoisomerases to these sites. Furthermore, the enrichment and locations of DSBs at pausing sites were shared among different cell types, suggesting that Pol II promoter-proximal pausing is a common regulatory mechanism. Our findings support a model in which topoisomerases participate in Pol II promoter-proximal pausing and indicated that DSBs at pausing sites contribute to transcriptional activation.

Advanced nanoscale carrier-based approaches to overcome biopharmaceutical issues associated with anticancer drug 'Etoposide'.

Etoposide (ETS), topoisomerase-II inhibitor, is a first-line anticancer therapeutics used in diverse cancer types. However, the therapeutic potential of this molecule has mainly impeded due to its detrimental toxicity profile, unfavorable rejection by the cancer cells due to P-glycoprotein (P-gp) efflux activity, and rapid hepatic clearance through extensive metabolism by Cytochrome-P450. To increase the therapeutic potency without significant adverse effects, the implication of novel ETS-nanoformulation strategies have recommended mainly. Nanomedicine based nanoformulation approaches based on nanoparticles (NPs), dendrimers, carbon-nanotubes (CNTs), liposomes, polymeric micelles, emulsions, dendrimers, solid-lipid NPs, etc offers immense potential opportunities to improve the therapeutic potential of pharmaceutically problematic drugs. This review provides an up-to-date argument on the work done in the field of nanomedicine to resolve pharmacokinetic and pharmacodynamic issues associated with ETS. The review also expounds the progress in regards to the regulatory, patenting and clinical trials related to the innovative formulation aspects of ETS.

Total Biosynthesis for Milligram-Scale Production of Etoposide Intermediates in a Plant Chassis.

Etoposide is a plant-derived drug used clinically to treat several forms of cancer. Recent shortages of etoposide demonstrate the need for a more dependable production method to replace the semisynthetic method currently in place, which relies on extraction of a precursor natural product from Himalayan mayapple. Here we report milligram-scale production of (-)-deoxypodophyllotoxin, a late-stage biosynthetic precursor to the etoposide aglycone, using an engineered biosynthetic pathway in tobacco. Our strategy relies on engineering the supply of coniferyl alcohol, an endogenous tobacco metabolite and monolignol precursor to the etoposide aglycone. We show that transient expression of 16 genes, encoding both coniferyl alcohol and main etoposide aglycone pathway enzymes from mayapple, in tobacco leaves results in the accumulation of up to 4.3 mg/g dry plant weight (-)-deoxypodophyllotoxin, and enables isolation of high-purity (-)-deoxypodophyllotoxin after chromatography at levels up to 0.71 mg/g dry plant weight. Our work reveals that long (>10 step) pathways can be efficiently transferred from difficult-to-cultivate medicinal plants to a tobacco plant production chassis, and demonstrates mg-scale total biosynthesis for access to valuable precursors of the chemotherapeutic etoposide.

Enzymatic O-Glycosylation of Etoposide Aglycone by Exploration of the Substrate Promiscuity for Glycosyltransferases.

The 4-O-ß-d-glucopyranoside of DMEP ((-)-4'-desmethylepipodophyllotoxin) (GDMEP), a natural product from Podophyllum hexandrum, is the direct precursor to the topoisomerase inhibitor etoposide, used in dozens of chemotherapy regimens for various malignancies. The biosynthesis pathway for DMEP has been completed, while the enzyme for biosynthesizing GDMEP is still unclear. Here, we report the enzymatic O-glycosylation of DMEP with 53% conversion by exploring the substrate promiscuity and entrances of glycosyltransferases. Notably, we found 6 essential amino acid residues surrounding the putative substrate entrances exposed to the protein surface in UGT78D2, CsUGT78D2, and CsUGT78D2-like, and these residues may determine substrate specificity and high O-glycosylation activity toward DMEP. Our results provide an effective route for one-step synthesis of GDMEP. Identification of the key residues and entrances of glycosyltransferases will promote precise identification of glycosyltransferase biocatalysts for novel substrates and provide a rational basis for glycosyltransferase engineering.

Real-time monitoring of etoposide prodrug activated by hydrogen peroxide with improved safety.

Etoposide is one of the most used first-line chemotherapeutic drugs. However, its application is still limited by its side effects. Herein, we designed a novel H2O2 sensitive prodrug 6YT for selectively releasing the anti-cancer drug etoposide in cancer cells. In this paper, etoposide and a hydrogen peroxide (H2O2) sensitive aryl borate ester group were linked by a fluorescent coumarin and finally the prodrug 6YT was generated. The fluorescence of coumarin was quenched before the connected aryl borate ester group was cleaved by H2O2. However, in the high level H2O2 environment of the tumor, the fluorescence could be activated simultaneously with the release of etoposide, and the drug release state of the prodrug was monitored real-time. With the support of 6YT, we obtained direct and visual evidence of etoposide release in a high H2O2 environment both in cells and zebrafish. The prodrug 6YT was also verified with comparable activity and improved safety with etoposide both in cells and in a mouse model. As a safe and effective prodrug, 6YT is expected to be one of the promising candidates in chemotherapy against cancer.

Smoothed Potential MD Simulations for Dissociation Kinetics of Etoposide To Unravel Isoform Specificity in Targeting Human Topoisomerase II.

Human type II topoisomerases (TopoII) are essential for controlling DNA topology within the cell. For this reason, there are a number of TopoII-targeted anticancer drugs that act by inducing DNA cleavage mediated by both TopoII isoforms (TopoIIα and TopoIIß) in cells. However, recent studies suggest that specific poisoning of TopoIIα may be a safer strategy for treating cancer. This is because poisoning of TopoIIß appears to be linked to the generation of secondary leukemia in patients. We recently reported that enzyme-mediated DNA cleavage complexes (in which TopoII is covalently linked to the cleaved DNA during catalysis) formed in the presence of the anticancer drug etoposide persisted approximately 3-fold longer with TopoIIα than TopoIIß. Notably, enhanced drug-target residence time may reduce the adverse effects of specific TopoIIα poisons. However, it is still not clear how to design drugs that are specific for the α isoform. In this study, we report the results of classical molecular dynamics (MD) simulations to comparatively analyze the molecular interactions formed within the TopoII/DNA/etoposide complex with both isoforms. We also used smoothed potential MD to estimate etoposide dissociation kinetics from the two isoform complexes. These extensive classical and enhanced sampling simulations revealed stabilizing interactions of etoposide with two serine residues (Ser763 and Ser800) in TopoIIα. These interactions are missing in TopoIIß, where both amino acids are alanine residues. This may explain the greater persistence of etoposide-stabilized cleavage complexes formed with Topo TopoIIα. These findings could be useful for the rational design of specific TopoIIα poisons.