Synthesis and evaluation of stereoisomers of methylated catechin and epigallocatechin derivatives on modulating P-glycoprotein-mediated multidrug resistance in cancers.

P-glycoprotein (P-gp; ABCB1)-mediated drug efflux causes multidrug resistance in cancer. Previous synthetic methylated epigallocatechin (EGC) possessed promising P-gp modulating activity. In order to further improve the potency, we have synthesized some novel stereoisomers of methylated epigallocatechin (EGC) and gallocatechin (GC) as well as epicatechin (EC) and catechin (C).

Increased S1P induces S1PR2 internalization to blunt the sensitivity of colorectal cancer to 5-fluorouracil via promoting intracellular uracil generation.

Sphingosine-1-phosphate (S1P), the backbone of most sphingolipids, activating S1P receptors (S1PRs) and the downstream G protein signaling has been implicated in chemoresistance. In this study we investigated the role of S1PR2 internalization in 5-fluorouracil (5-FU) resistance in human colorectal cancer (CRC). Clinical data of randomly selected 60 CRC specimens showed the correlation between S1PR2 internalization and increased intracellular uracil (P < 0.

SphK2 confers 5-fluorouracil resistance to colorectal cancer via upregulating H3K56ac-mediated DPD expression.

Aberrant sphingolipid metabolism has been implicated in chemoresistance, but the underlying mechanisms are still poorly understood. Herein we revealed a previously unrecognized mechanism of 5-fluorouracil (5-FU) resistance contributed by high SphK2-upregulated dihydropyrimidine dehydrogenase (DPD) in colorectal cancer (CRC), which is evidenced from human CRC specimens, animal models, and cancer cell lines. TMA samples from randomly selected 60 CRC specimens firstly identified the clinical correlation between high SphK2 and increased DPD (p < 0.

Novel α-Lipoic Acid/3--Butylphthalide Conjugate Enhances Protective Effects against Oxidative Stress and 6-OHDA Induced Neuronal Damage.

Neurodegenerative diseases are irreversible conditions that result in progressive degeneration and death of nerve cells. Although the underlying mechanisms may vary, oxidative stress is considered to be one of the major causes of neuronal loss. Importantly, there are still no comprehensive treatments to completely cure these diseases.

S1PR2 inhibitors potently reverse 5-FU resistance by downregulating DPD expression in colorectal cancer.

In this study, S1PR2 was reckoned as a brand-new GPCR target for designing inhibitors to reverse 5-FU resistance. Herein a series of pyrrolidine pyrazoles as the S1PR2 inhibitors were designed, synthesized and evaluated for their activities of anti-FU-resistance. Among them, the most promising compound JTE-013, exhibited excellent inhibition on DPD expression and potent anti-FU-resistance activity in various human cancer cell lines, along with the in vivo HCT116 cells xenograft model, in which the inhibition rate of 5-FU was greatly increased from 13.

Structural modification of oridonin DAST induced rearrangement.

A simple and efficient protocol was developed for the syntheses of oridonin analogues, 6,20-epoxy -kaurane diterpenoid analogues from oridonin diethylaminosulfur trifluoride (DAST) promoted rearrangement, most of which exhibited superior anticancer activities compared with their precursor.

Extending the structure-activity relationship study of marine natural ningalin B analogues as P-glycoprotein inhibitors.

In the present study, a total of 25 novel ningalin B analogues were synthesized and evaluated for their P-gp modulating activity in a P-gp overexpressed breast cancer cell line LCC6MDR. Preliminary structure-activity study shows that A ring and its two methoxy groups are important pharmacophores for P-gp inhibiting activity. Among all derivatives, 23 is the most potent P-gp modulator with EC of 120-165 nM in reversing paclitaxel, DOX, vinblastine and vincristine resistance.

Optimization of permethyl ningalin B analogs as P-glycoprotein inhibitors.

In the present study, a total of 9 novel permethyl ningalin B analogs have been synthesized and evaluated for their P-gp modulating activity in a P-gp overexpressed breast cancer cell line LCC6MDR. Among these derivatives, compound 12 with dimethoxy groups at rings A and B and tri-substitution at ring C with ortho-methoxyethylmorpholine, meta-bromo and para-benzyloxy groups displays the most potent P-gp modulating activity with EC50 of 423 nM to reverse paclitaxel resistance. It is non-toxic towards L929 fibroblast with IC50 greater than 100 μM and with selective index greater than 236.

Potent and Nontoxic Chemosensitizer of P-Glycoprotein-Mediated Multidrug Resistance in Cancer: Synthesis and Evaluation of Methylated Epigallocatechin, Gallocatechin, and Dihydromyricetin Derivatives.

We are interested in developing novel natural product-derived P-gp inhibitors to reverse cancer drug resistance. Here, we have synthesized 55 novel derivatives of methylated epigallocatechin (EGC), gallocatechin (GC), and dihydromyricetin (DHM). Three EGC derivatives (23, 35, and 36) and three GC derivatives (50, 51, and 53) are significantly better than epigallocatechin gallate (EGCG) with a relative fold (RF) ranging from 31.

Modification of marine natural product ningalin B and SAR study lead to potent P-glycoprotein inhibitors.

In this study, new marine ningalin B analogues containing a piperazine or a benzoloxy group at ring C have been synthesized and evaluated on their P-gp modulating activity in human breast cancer and leukemia cell lines. Their structure-activity relationship was preliminarily studied. Compounds 19 and 20 are potent P-gp inhibitors.

[An experimental study of the cervical lymphatic imaging in interstitial magnetic resonance lymphography of tongue using Dextran-DTPA-Gd].

Purpose: To explore the application value of the cervical lymphatic imaging in interstitial magnetic resonance lymphography using submucosal injection of Dextran-DTPA-Gd.

Methods: 0.2 mL Dextran-DTPA-Gd (3.

Sensitizing human multiple myeloma cells to the proteasome inhibitor bortezomib by novel curcumin analogs.

The proteasome plays a vital role in the degradation of proteins involved in several pathways including the cell cycle, cellular proliferation and apoptosis and is a validated target in cancer treatment. Bortezomib (Velcade®, PS-341) is the first US FDA approved proteasome inhibitor anticancer drug used in the treatment of refractory multiple myeloma. In spite of its improved efficacy compared to alternative therapies, about 60% of patients do not respond to bortezomib due to the emergence of resistance.

EGCG, green tea polyphenols and their synthetic analogs and prodrugs for human cancer prevention and treatment.

Cancer-preventive effects of tea polyphenols, especially epigallocatechin-3-gallate (EGCG), have been demonstrated by epidemiological, preclinical, and clinical studies. Green tea polyphenols such as EGCG have the potential to affect multiple biological pathways, including gene expression, growth factor-mediated pathways, the mitogen-activated protein kinase-dependent pathway, and the ubiquitin/proteasome degradation pathway. Therefore, identification of the molecular targets of EGCG should greatly facilitate a better understanding of the mechanisms underlying its anticancer and cancer-preventive activities.

Evaluation of curcumin acetates and amino acid conjugates as proteasome inhibitors.

Curcumin (diferuloylmethane) is the main active ingredient of turmeric, a traditional herbal medicine and food of south Asia. Curcumin has been found to have a wide range of biological activities, including antioxidant, anti-inflammatory, chemopreventive and chemotherapeutic activities. Curcumin is currently being tested in clinical trials for treatment of various types of cancers, including multiple myeloma, pancreatic cancer and colon cancer.

Design and syntheses of permethyl ningalin B analogues: potent multidrug resistance (MDR) reversal agents of cancer cells.

A series of novel N-arylalkyl-3,4-diaryl-substituted pyrrole-2,5-diones were synthesized. They exhibited promising P-gp modulating activity in a P-gp overexpressing breast cancer cell line (LCC6MDR). Compound 6 (with three methoxy groups at D-ring) displayed the highest P-gp modulating activity.

Antitumor activity of novel fluoro-substituted (-)-epigallocatechin-3-gallate analogs.

Epidemiological studies support the cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin gallate [(-)-EGCG], however, (-)-EGCG is unstable under physiological conditions. Here we report that two novel fluoro-substituted (-)-EGCG analogs inhibited tumor growth with similar potency to that of Pro-EGCG (1) which has improved potency over parental compound (-)-EGCG in human breast cancer MDA-MB-231 xenografts. MDA-MB-231 tumors treated with each fluoro-substituted (-)-EGCG analog showed proteasome inhibition and apoptotic cell death, suggesting that the proteasome might be one of the cellular targets of fluoro-(-)-EGCGs and that proteasome inhibition is partially responsible for the observed antitumor activity.

Prodrugs of fluoro-substituted benzoates of EGC as tumor cellular proteasome inhibitors and apoptosis inducers.

The most potent catechin in green tea is (-)-epigallocatechin-3-gallate [(-)-EGCG], which, however, is unstable under physiological conditions. To discover more stable and more potent polyphenol proteasome inhibitors, we synthesized several novel fluoro-substituted (-)-EGCG analogs, named F-EGCG analogs, as well as their prodrug forms with all of -OH groups protected by acetate. We report that the prodrug form of one F-EGCG analog exhibited greater potency than the previously reported peracetate of (-)-EGCG to inhibit proteasomal activity, suppress cell proliferation, and induce apoptosis in human leukemia Jurkat T cells, demonstrating the potential of these compounds to be developed into novel anti-cancer and cancer-preventive agents.

Methylation suppresses the proteasome-inhibitory function of green tea polyphenols.

Under physiological conditions, biotransformation reactions, such as methylation, can modify green tea polyphenols (GTPs) and therefore limit their in vivo cancer-preventive activity. Although a recent study suggested that methylated polyphenols are less cancer-protective, the molecular basis is unknown. We previously reported that ester bond-containing GTPs, for example (-)-epigallocatechin-3-gallate [(-)-EGCG] or (-)-epicatechin-3-gallate [(-)-ECG], potently and specifically inhibit the proteasomal chymotrypsin-like activity.

Methylation of green tea polyphenols affects their binding to and inhibitory poses of the proteasome beta5 subunit.

Previously, we showed that ester carbon-containing tea polyphenols, including (-)-epigallocatechin gallate [(-)-EGCG] and (-)-epicatechin-3-gallate [(-)-ECG], potently inhibit proteasomal chymotrypsin-like activity. In addition, our in silico docking study suggested that a particular pose of (-)-EGCG could lead to potential covalent modification of the N-terminal threonine (Thr 1) of the proteasome beta5 subunit in the chymotrypsin-like active site. It has been suggested that some major biotransformation reactions, such as methylation, could result in reduced biological activity of (-)-EGCG in vivo.

Evaluation of proteasome-inhibitory and apoptosis-inducing potencies of novel (-)-EGCG analogs and their prodrugs.

The anti-cancer and cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin gallate [(-)-EGCG] are well documented by a variety of studies, including epidemiological, cell culture, animal, and clinical studies. While (-)-EGCG remains the most potent polyphenol in green tea, it is very unstable in neutral or alkaline conditions (i.e.

Structure-activity study of epi-gallocatechin gallate (EGCG) analogs as proteasome inhibitors.

The structure-activity relationship of a number of synthetic green tea polyphenol analogs involving modifications of A ring and B ring of epi-gallocatechin gallate (EGCG) as proteasome inhibitors has been examined. It was found that in B ring, a decrease in the number of OH groups led to decreased potency. Introduction of a hydrophobic benzyl group into the 8 position of A ring did not significantly affect the proteasome-inhibitory potency.

Green tea and tea polyphenols in cancer prevention.

The cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin gallate [(-)-EGCG] are widely supported by results from epidemiological, cell culture, animal and clinical studies in the recent decade. In vitro cell culture studies show that tea polyphenols potently induce apoptotic cell death and cell cycle arrest in tumor cells but not in their normal cell counterparts. Green tea polyphenols affect several signal transduction pathways, including growth factor-mediated, the mitogen-activated protein kinase (MAPK)-dependent, and ubiquitin/proteasome degradation pathways.

Study of the green tea polyphenols catechin-3-gallate (CG) and epicatechin-3-gallate (ECG) as proteasome inhibitors.

The green tea polyphenol catechin-3-gallate (CG) and epicatechin-3-gallate (ECG) were synthesized enantioselectively via a Sharpless hydroxylation reaction followed by a diastereoselective cyclization. Their potencies to inhibit the proteasome activity were measured. The unnatural enantiomers were found to be equally potent to the natural compounds.

7-imidazolylalkanamido-1-carboxylalkylbenzo-diazepine, a novel series of farnesyltransferase inhibitors.

Aim: Design, synthesis and evaluation of a series of 7-imidazolylalkanamido-1-carboxylalkylbenzodiazepine farnesyltransferase (FTase) inhibitors.

Methods And Results: Coupling of imidazolylalkylcarboxylic acids and 1-substituted 7-aminobenzodiazepines (5a-5c) yielded 10 new compounds (6-12, 16-18) which were biologically tested against FTase using scintillation proximity assay method.

Conclusion: Five target compounds were found to be potential farnesyltransferase inhibitors.