Solid‐state 31P NMR investigation on the status of guanine nucleotides in paclitaxel‐stabilized microtubules

Microtubule dynamics is a target for many chemotherapeutic drugs. In order to understand the biochemical effects of paclitaxel on the GTPase activity of tubulin, the status of guanine nucleotides in microtubules was investigated by ³¹P cross‐polarization magic angle spinning (CPMAS) NMR. Microtubules were freshly prepared in vitro in the presence of paclitaxel and then lyophilized in sucrose buffer for solid‐state NMR experiments. A ³¹P CPMAS NMR spectrum with the SNR of 25 was successfully acquired from the lyophilized microtubule sample. The broadness of the ³¹P spectral lines in the spectrum indicates that the molecular environments around the guanine nucleotides inside tubulin may not be as crystalline as reported by many diffraction studies. Deconvolution of the spectrum into four spectral components was carried out in comparison with the ³¹P NMR spectra obtained from five control samples. The spectral analysis suggested that about 13% of the nucleotides were present as GTP and 37% as GDP in the β‐tubulin (E‐site) of the microtubules. It was found that most of the GDPs were present as GDP‐P_i complex in the microtubules, which seems to be one of the effects of paclitaxel binding. Copyright © 2015 John Wiley & Sons, Ltd.     

Quantitative analysis of docetaxel in human plasma using liquid chromatography coupled with tandem mass spectrometry

An assay for the quantitative determination of docetaxel in human plasma is described. Docetaxel was extracted from the matrix using liquid-liquid extraction with ter-butylmethylether, followed by high-performance liquid chromatographic analysis using an alkaline eluent. Paclitaxel was used as internal standard. Positive ionization electrospray tandem mass spectrometry was performed for selective and sensitive detection. The method was validated according to the FDA guidelines on bioanalytical method validation. The validated range for docetaxel was from 0.25--1000 ng/mL using 200 microL plasma aliquots. The method requires only a limited volume (200 microL) of human plasma and the method can be applied in studies requiring a low lower limit of quantitation of 0.25 ng/mL. The assay was applied successfully in several clinical and pharmacological studies with docetaxel.     

Preparation of Catechin Nanoemulsion from Oolong Tea Leaf Waste and Its Inhibition of Prostate Cancer Cells DU-145 and Tumors in Mice

Anti-cancer activity of catechin nanoemulsions prepared from Oolong tea leaf waste was studied on prostate cancer cells DU-145 and DU-145-induced tumors in mice. Catechin nanoemulsions composed of lecithin, Tween-80 and water in an appropriate proportion was prepared with high stability, particle size of 11.3 nm, zeta potential of −67.2 mV and encapsulation efficiency of 83.4%. Catechin nanoemulsions were more effective than extracts in inhibiting DU-145 cell growth, with the IC₅₀ being 13.52 and 214.6 μg/mL, respectively, after 48 h incubation. Furthermore, both catechin nanoemulsions and extracts could raise caspase-8, caspase-9 and caspase-3 activities for DU-145 cell apoptosis, arresting the cell cycle at S and G2/M phases. Compared to control, catechin nanoemulsion at 20 μg/mL and paclitaxel at 10 μg/mL were the most effective in reducing tumor volume by 41.3% and 52.5% and tumor weight by 77.5% and 90.6% in mice, respectively, through a decrease in EGF and VEGF levels in serum.     

A Novel Docetaxel-Biotin Chemical Conjugate for Prostate Cancer Treatment

A novel conjugate of docetaxel and biotin (designated as IDD-1010) was designed and chemically synthesized via an ester linkage at position 2’ carbon in docetaxel. The synthesized pure IDD-1010 exhibits a potent anti-cancer activity in in vitro and in vivo studies. At 10 nM, IDD-1010 has induced increased apoptosis and mitotic arrest of PC3-Luc prostate cancer cells, causing aneuploidy and cell death at higher concentrations. Toxicology studies indicate that the maximal tolerated dose (MTD) of IDD-1010 is 150 mg/kg in mice; equivalent to about 12.2 mg/kg of body weight, or to about an 850 mg dose for a patient weighing 70 kg. The MTD-treated mice exhibited weight gain similar to that of the control group, with no gross pathological signs at 14 days post-dosing. At a lower dose, IDD-1010 treatment did not lead to any significant weight loss in mice, although decreased the tumor volume stemming from injecting cancer cells into the dorsal loop of mouse prostate, and it was found to be more potent than Paclitaxel (reference drug). Similarly, IDD-1010 treatment significantly reduced tumor weight and thereby increased the percentage of mice survival as compared to reference drug-treated and control groups. To summarize, the described experiments using IDD-1010, as compared to the reference drug, strongly suggest a potential treatment utility with a wider therapeutic window for prostate cancer. Henceforth, clinical research on such a novel drug candidate would be greatly worthwhile.     

Synthesis of 14-Bromo and 14-Hydroxy Baccatin III Derviatives

Numerous efforts towards synthesis of anticancer drug paclitaxel (Taxol(r), 1a) with improved activities led to the modification at 13-phenylisoserine side chain and different positions of its core structure-baccatin III 1c1. At the same time, the activities of searching new taxoids for starting materials of new semi-synthetic paclitaxel analogs from Taxus spp. plant have not ever been stopped. Among these taxoids, 14?-hydroxy-10-deacetylbaccatin III 22 and 13-acetyl-9-dihydrobaccatin III …     

In vitro evaluation of antiproliferative effect of ethyl gallate against human oral squamous carcinoma cell line KB

Although some polyphenols are known to possess anticancer activity against different cancer cell lines through induction of apoptosis, the mode of antiproliferative effect of ethyl gallate against human oral squamous carcinoma cell line KB was not studied until now. Therefore, the antiproliferative effect of ethyl gallate was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay in comparison with the reference drug paclitaxel. Generation of reactive oxygen species, mitochondrial membrane potential loss, DNA damage and apoptosis were determined using 2,7-diacetyldichlorofluorescein fluorescence, uptake of rhodamine-123 by mitochondria, comet assay and acridine orange/ethidium bromide dual-dye staining method. Both ethyl gallate and paclitaxel exhibited cytotoxicity in a dose-dependent manner. The 50% inhibitory concentration for ethyl gallate was 30 and 20 μg/mL for paclitaxel. A volume of 50 μg/mL of ethyl gallate was found to be significantly effective (P < 0.05) in controlling the cancer cell proliferation leading to acute apoptosis.     

Omega‐3 Fatty Acid Grafted PAMAM‐Paclitaxel Conjugate Exhibits Enhanced Anticancer Activity in Upper Gastrointestinal Cancer Cells

Upper Gastrointestinal Cancers (UGCs) are a leading cause of cancer‐related deaths worldwide. Paclitaxel (PTX) is frequently used for the treatment of UGCs; however, low bioavailability, reduced solubility, and dose‐dependent toxicity impede its therapeutic use. PAMAMG_4.0‐NH₂‐DHA is synthesized by linking amine‐terminated fourth‐generation poly(amidoamine) (PAMAMG_4.0‐NH₂) dendrimers with omega‐3 fatty acid docosahexaenoic acid (DHA). Next, PAMAMG_4.0‐NH₂‐DHA‐PTX (DHATX) and PAMAMG_4.0‐NH₂‐PTX (PAX) conjugates are synthesized by subsequent covalent binding of PTX with PAMAMG_4.0‐NH₂‐DHA and PAMAMG_4.0‐NH₂, respectively. ¹H‐NMR and MALDI‐TOF analyses are performed to confirm conjugation of DHA to PAMAMG_4.0‐NH₂ and PTX to PAMAMG_4.0‐NH₂‐DHA. The cell viability, clonogenic cell survival, and flow cytometry analyses are used to determine the anticancer activity of PTX, PAX, and DHATX in UGC cell lines. The in vitro data indicate that treatment with DHATX is significantly more potent than PTX or PAX at inhibiting cellular proliferation, suppressing long‐term survival, and inducing cell death in UGC cells.

     

Synergies of urushiol and its pechmann derivative compatible with paclitaxel anti-HepG2 activity

The paper investigated the synergistic inhibitory effects of 1 (triene urushiol), 2 (monoene urushiol), 3 (urushiol pechmann derivative) and paclitaxel on proliferation of human hepatocellular carcinoma cell line HepG2. The inhibitory rate of cell proliferation was detected by MTT assay after HepG2 cells were separately treated with compounds 1, 2 and 3 combined with paclitaxel at different concentrations for 72 h. The joint index analysis was used to examine whether those compatible drugs had synergistic effect. The results showed that compounds 1, 2 and 3 had significant inhibitory effect on the proliferation of HepG2 cells in a dose-dependent manner, and their half inhibitory concentrations IC₅₀ were 29.3, 55.5 and 27.1 μM respectively. The synergistic effect of compounds 1, 2 and 3 combined with paclitaxel significantly inhibited the proliferation of HepG2 cells in vitro.