ORCID Profile
0000-0001-9068-0860
Current Organisation
UNSW Sydney
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Publisher: Bentham Science Publishers Ltd.
Date: 09-2012
DOI: 10.2174/156800912803251199
Abstract: Membrane transporters govern the movement of drugs and their metabolites across biological membranes, thereby determining their pharmacokinetics, efficacy and adverse drug reactions. Platinum-based anticancer drugs are a mainstay of chemotherapy for many human malignancies. However, their clinical utility is limited by tumor resistance and normal tissue toxicities, which are determined at least in part by the level of tissue accumulation of platinum. Recently, several members of the ATP-binding cassette (ABC), solute carrier (SLC) and ATPase membrane protein superfamilies have been found to contribute to the net accumulation of platinum drugs in malignant and normal tissues. Herein, a review has been carried out to critically evaluate current preclinical and clinical evidence implicating membrane transporters as determinants of the pharmacology of cisplatin, oxaliplatin, carboplatin and related investigational compounds. The evidence includes studies of recombinant cell systems with genetically modified expression of in idual membrane transporters, platinum-resistant or -sensitive human cancer cells and in vivo xenografted tumors, animal models of platinum-induced nephro-, oto- or neurotoxicity, and clinical studies of associations between the membrane transporter tumor expression and patient outcomes from platinum-based chemotherapy. Understanding the role of membrane transporters as determinants of the pharmacology of platinum drugs will be a basis for targeting these drug transporters in in idualized and optimized platinum-based cancer therapy, and new drug development.
Publisher: Informa UK Limited
Date: 18-11-2019
DOI: 10.1080/07391102.2018.1539411
Abstract: The interaction of trypsin with Gensenoside-Rg1 (G-Rg1) was studied using fluorescence, ultraviolet-visible (UV-vis), and circular dichroism (CD) spectroscopies along with enzyme activity assay and molecular docking. The enzyme activity assays showed that G-Rg1 inhibited the activity of trypsin effectively. The fluorescence experiments indicated that a complex of G-Rg1-trypsin was formed and that the fluorescence of trypsin was quenched by G-Rg1 via a mixed-quenching mechanism (both static and dynamic quenching). The thermodynamic analysis suggested that hydrophobic interaction and hydrogen bond were the major forces between G-Rg1 and trypsin. According to the theory of Förster's non-radiation energy transfer, the binding distance between trypsin and G-Rg1 was calculated to be 2.01 nm, which implies that energy transfer occurred within the complex. The experimental results obtained from UV-vis absorption spectra, synchronous fluorescence spectra, and CD spectra indicated that G-Rg1 was mainly located on tryptophan moiety and that the interaction between G-Rg1 and trypsin led to conformational changes of trypsin with some α-helix and unordered coil structures being transformed into β-sheet structures. In addition, docking results supported the above experimental findings and suggested the possible binding location of G-Rg1 on trypsin along with the possible hydrogen bonds and hydrophobic interactions between G-Rg1 and trypsin. The experimental results from this study should be useful to minimize the antinutritional effects and make full use of Genseng extracts in the food industry and also be helpful to the design of the drugs for the diseases related to overexpression of trypsin. Communicated by Ramaswamy H. Sarma.
Publisher: Wiley
Date: 28-05-2013
Abstract: The purpose of the present study was to determine whether copper histidine could inhibit copper transporter 1 (Ctr1)-mediated transport of oxaliplatin in vitro and thereby limit the accumulation of platinum and neurotoxicity of oxaliplatin in dorsal root ganglion (DRG) tissue in vivo. In HEK293 cells overexpressing rat Ctr1, copper histidine was shown to be transported by Ctr1 and to inhibit their Ctr1-mediated uptake of oxaliplatin. Pilot in vivo dose-finding studies showed that copper histidine at doses up to 2 mg/kg, p.o., daily for 5 days/week could be added to maximum tolerated doses of oxaliplatin (1.85 mg/kg, i.p., twice weekly) for 8 week combination treatment studies in female Wistar rats. After treatment, rats showed significant changes in sensory neuron size profiles in DRG tissue induced by oxaliplatin that were not altered by its coadministration with copper histidine. The expression of copper transporters (Ctr1 and copper-transporting P-type ATPase 1 (Atp7a)) in DRG tissue appeared unchanged following treatment with oxaliplatin given alone or with copper histidine. Platinum and copper tissue levels were higher in DRG than in most other tissues, but were unaltered by the addition of copper histidine to oxaliplatin treatment. In conclusion, copper histidine inhibited cellular uptake of oxaliplatin mediated by Ctr1 in vitro without altering the accumulation of platinum or neurotoxicity of oxaliplatin in DRG tissue in vivo at doses tolerated in combination with oxaliplatin treatment.
Publisher: Wiley
Date: 29-10-2008
DOI: 10.1111/J.1440-1681.2008.05017.X
Abstract: 1. Satraplatin is an investigational orally administered platinum-based antitumour drug. The present study compared the plasma protein binding, stability and degradation of satraplatin with that of its active metabolite JM118 and cisplatin. 2. The platinum complexes were incubated in human plasma for up to 2 h at 37 degrees C and quantified in plasma fractions by inductively coupled plasma-mass spectrometry on- or off-line to high-performance liquid chromatography. 3. All three platinum drugs became irreversibly bound to plasma proteins and showed negligible reversible protein binding. They were also unstable in plasma and generated one or more platinum-containing degradation products during their incubation. However, the three platinum complexes differed in the kinetics of their instability and protein binding, as well as in the number of degradation products formed during their incubation. 4. In conclusion, the plasma protein binding, instability and degradation of satraplatin and its active metabolite JM118 are qualitatively similar to that of cisplatin and other clinically approved platinum-based drugs. Quantitative differences in their irreversible protein binding and degradation were related to their respective physiochemical properties and bioactivation mechanisms.
Publisher: Springer Science and Business Media LLC
Date: 13-09-2018
DOI: 10.1007/S11033-018-4306-5
Abstract: Study on the binding properties of helicid by pepsin systematically using multi-spectroscopic techniques and molecular docking method, and these interactions comprise biological recognition at molecular level and backbone of biological significance in medicine concerned with the uses, effects, and modes of action of drugs. We investigated the mechanism of interaction between helicid and pepsin by using various spectroscopic techniques viz., fluorescence spectra, UV-Vis absorption spectra, circular dichroism (CD), 3D spectra, synchronous fluorescence spectra and molecular docking methods. The quenching mechanism associated with the helicid-pepsin interaction was determined by performing fluorescence measurements at different temperatures. From the experimental results show that helicid quenched the fluorescence intensity of pepsin via a combination of static and dynamic quenching process. The binding constants (K
Publisher: Springer Science and Business Media LLC
Date: 24-05-2009
DOI: 10.1007/S00280-009-1017-6
Abstract: We report the neuronal expression of copper transporter 1 (CTR1) in rat dorsal root ganglia (DRG) and its association with the neurotoxicity of platinum-based drugs. CTR1 expression was studied by immunohistochemistry and RT-PCR. The toxicity of platinum drugs to CTR1-positive and CTR1-negative neurons was compared in DRG from animals treated with maximum tolerated doses of oxaliplatin (1.85 mg/kg), cisplatin (1 mg/kg) or carboplatin (8 mg/kg) twice weekly for 8 weeks. Abundant CTR1 mRNA was detected in DRG tissue. CTR1 immunoreactivity was associated with plasma membranes and cytoplasmic vesicular structures of a subpopulation (13.6 +/- 3.1%) of mainly large-sized (mean cell body area, 1,787 +/- 127 microm(2)) DRG neurons. After treatment with platinum drugs, the cell bodies of these CTR1-positive neurons became atrophied, with oxaliplatin causing the greatest percentage reduction in the mean cell body area relative to controls (42% P < 0.05), followed by cisplatin (18% P < 0.05) and carboplatin causing the least reduction (3.2% P = NS). CTR1-negative neurons, with no immunoreactivity or only diffuse cytoplasmic staining, showed less treatment-induced cell body atrophy than CTR1-positive neurons. CTR1 is preferentially expressed by a subset of DRG neurons that are particularly vulnerable to the toxicity of platinum drugs. These findings, together with its neuronal membrane localization, are suggestive of CTR1-related mechanisms of platinum drug neuronal uptake and neurotoxicity.
Publisher: Springer Science and Business Media LLC
Date: 30-11-2015
DOI: 10.1038/SREP17348
Abstract: Here, we investigated the impact of mulberry fruit (MBF) extracts on lipopolysaccharide (LPS)-induced inflammatory responses in RAW 264.7 macrophages and the therapeutic efficacy of MBF diet in mice with dextran sulfate sodium (DSS)-induced acute colitis and MUC2 −/− mice with colorectal cancer. In vitro , LPS-induced nitric oxide (NO) production was significantly inhibited by MBF extracts via suppressing the expression of proinflammatory molecules, including inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin-1 beta (IL-β) and IL-6. Particularly, a dose-dependent inhibition on LPS-induced inflammatory responses was observed following treatment with MBF dichloromethane extract (MBF-DE), in which linoleic acid and ethyl linolenate were identified as two active compounds. Moreover, we elucidated that MBF-DE attenuated LPS-induced inflammatory responses by blocking activation of both NF-κB 65 and pERK/MAPK pathways. In vivo , DSS-induced acute colitis was significantly ameliorated in MBF-fed mice as gauged by weight loss, colon morphology and histological damage. In addition, MBF-fed MUC2 −/− mice displayed significant decrease in intestinal tumor and inflammation incidence compared to control diet-fed group. Overall, our results demonstrated that MBF suppressed the development of intestinal inflammation and tumorgenesis both in vitro and in vivo and supports the potential of MBF as a therapeutic functional food for testing in human clinical trials.
Publisher: Springer Science and Business Media LLC
Date: 06-2003
Publisher: Springer Science and Business Media LLC
Date: 12-2002
DOI: 10.1007/BF03192337
Publisher: Elsevier BV
Date: 12-2017
DOI: 10.1016/J.JINORGBIO.2017.04.022
Abstract: Oxaliplatin-based chemotherapy is the mainstay for the treatment of advanced colorectal cancer. Copper transporter proteins have been implicated in the transport of platinum-based anticancer drugs, but their expression in human colorectal cancer cell lines and roles in controlling their sensitivity to oxaliplatin are not well studied or understood. The endogenous and modified expression of copper uptake transporter 1 (hCTR1) was studied in a panel of human colorectal cancer cell lines (DLD-1, SW620, HCT-15 and COLO205) with ~20-fold variation in oxaliplatin sensitivity. hCTR1 protein was expressed more abundantly than ATP7A and ATP7B proteins, but with broadly similar levels and patterns of expression across four colorectal cancer cell lines. In a colorectal cancer cell-line background (DLD-1), stable transfection of the hCtr1 gene enhanced hCTR1 protein expression and increased the sensitivity of the cells to the cytotoxicity of copper and oxaliplatin. Treatment with copper chelators (ammonium tetrathiomolybdate, bathocuproinedisulfonic acid and D-penicillamine) increased expression of hCTR1 protein in DLD-1 and SW620 cells, and potentiated the cytotoxicity of oxaliplatin in DLD-1 but not SW620 cells. Treatment with copper chloride altered neither the expression of copper transporters nor cytotoxicity of oxaliplatin in colorectal cancer lines. In conclusion, human colorectal cancer cell lines consistently express hCTR1 protein despite their variable sensitivity to oxaliplatin. Genetic or pharmacological modification of hCTR1 protein expression may potentiate oxaliplatin sensitivity in some but not all colorectal cancer cell lines.
Publisher: OMICS Publishing Group
Date: 2015
Publisher: Springer Science and Business Media LLC
Date: 11-05-2005
DOI: 10.1007/S00280-004-0953-4
Abstract: Peripheral neuropathy is induced by multiple doses of oxaliplatin and interferes with the clinical utility of the drug in patients with colorectal cancer. In this study, we sought to determine whether cell loss or selective neuronal damage was the basis for the peripheral neuropathy caused by oxaliplatin. Adult female rats were given 1.85 mg/kg oxaliplatin twice per week for 8 weeks. Nerve conduction and L5 dorsal root ganglia (DRG) were studied 1 week after the completion of all treatment. No mortality occurred during oxaliplatin treatment, but the rate of body weight gain was reduced compared to age-matched vehicle-treated controls. Oxaliplatin slowed conduction velocity and delayed conduction times in peripheral sensory nerves, without affecting central or motor nerve conduction. In L5 DRG, total numbers of neurons were unchanged by oxaliplatin, but there were significant reductions in neuronal size distribution, ganglion volume, average cell size and the relative frequency of large cells. In addition, the relative frequency of small DRG cells was increased by oxaliplatin. Oxaliplatin significantly altered the size distribution and average cell body area of the predominantly large parvalbumin-immunoreactive DRG neurons without affecting the frequency of parvalbumin staining. On the contrary, neither the staining frequency nor the size distribution of the predominantly small substance P-immunoreactive DRG neurons was changed by oxaliplatin. In conclusion, oxaliplatin causes selective atrophy of a subpopulation of DRG neurons with predominantly large parvalbumin-expressing cells without inducing neuronal loss. Because DRG cell body size and axonal conduction velocity are positively correlated, neuronal atrophy may be the morphological basis for the development of decreased sensory nerve conduction velocity that characterizes oxaliplatin-induced peripheral neuropathy.
Publisher: Elsevier BV
Date: 02-2008
DOI: 10.1016/J.JINORGBIO.2007.09.003
Abstract: In this study we characterised the in vitro antitumour and hepatotoxicity profiles of a series of Au(I) and Ag(I) bidentate phenyl and pyridyl complexes in a panel of cisplatin-resistant human ovarian cancer cell-lines, and in isolated rat hepatocytes. The gold and silver compounds overcame cisplatin-resistance in the CH1-cisR, 41M-cisR and SKOV-3 cell-lines, and showed cytotoxic potencies strongly correlated with their lipophilicity. Complexes with phenyl or 2-pyridyl ligands had high antitumour and hepatotoxic potency and low selectivity between different cell-lines. Their cytotoxicity profiles were similar to classic mitochondrial poisons and an ex le of this type of compound was shown to accumulate preferentially in the mitochondria of cancer cells in a manner that depended upon the mitochondrial membrane potential. In contrast, complexes with 3- or 4-pyridyl ligands had low antitumour and hepatotoxic potency and cytotoxicity profiles similar to 2-deoxy-D-glucose. In addition, they showed high selectivity between different cell-lines that was not attributable to variation in uptake in different cell-types. The in vitro hepatotoxic potency of the series of gold and silver compounds varied by over 61-fold and was closely related to their lipophilicity and hepatocyte uptake. In conclusion, Au(I) and Ag(I) bidendate pyridyl phosphine complexes demonstrate activity against cisplatin-resistant human cancer cells and in vitro cytotoxicity that strongly depends upon their lipophilicity.
Publisher: Springer Science and Business Media LLC
Date: 31-08-2006
DOI: 10.1007/S00280-006-0321-7
Abstract: To evaluate the antitumour activity of 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a vascular disrupting agent currently under phase II clinical trials in combination with cancer chemotherapy, in rats bearing chemically induced primary mammary tumours. Tumours were induced in female Wistar rats by injection of N-nitroso-N-methylurea at 100 mg/kg subcutaneously. A clinically relevant single dose of DMXAA (1,800 mg/m(2)) was given to animals when tumours were measurable. Tumour volume, extent of necrosis and cytokine profiles were measured. Compared with the control group, DMXAA treatment significantly delayed tumour doubling time and extended the time from treatment to euthanasia. Four of five DMXAA-treated animals showed necrosis involving 3.7-41.2% of the area of the tumour section at 24 h compared with none of four control animals (P < 0.028, Chi-square test). Intratumoural levels of TNFalpha, IL-6, VEGF and IL-1alpha were increased 4 h after DMXAA treatment. This study shows for the first time that DMXAA has significant in vivo antitumour activity against non-transplanted autochthonous tumours and in a host species other than the mouse.
Publisher: Elsevier BV
Date: 11-2007
DOI: 10.1016/J.NEURO.2007.04.009
Abstract: Paclitaxel-induced sensory neuropathy is a problematic side-effect of cancer chemotherapy. Previous studies in rodents have shown paclitaxel treatment to have many effects on different parts of the peripheral nervous system, but those responsible for its bothersome clinical side-effects are still unclear. In the current study, we sought to obtain information about the involvement of sensory neurons in paclitaxel neurotoxicity at the level of the dorsal root ganglion. Rats were treated with a clinically relevant dose of paclitaxel (87.5mg/m(2) weekly for a total of nine doses) to induce a sensory neuropathy then their L5 dorsal root ganglia were studied by morphometry and immunohistochemistry. Paclitaxel treatment was generally well tolerated, and slowed conduction velocity and prolonged conduction latencies in the peripheral sensory nerves without altering conduction in the central or motor pathways of the H-reflex arc. In the L5 dorsal root ganglion, nucleolus size and the number of neurons with eccentric nuclei were increased only in a subpopulation of dorsal root ganglion neurons with cell body cross-sectional areas greater than 1750 microm(2), which made up less than 10% of the total population. Paclitaxel treatment increased immunohistochemical staining for activating transcription factor-3 (ATF-3), c-Jun and neuropeptide Y (NPY) but only in a small percentage of neuronal cell bodies and mainly in those with large cell bodies. In conclusion, we have demonstrated that nucleolar enlargement, nuclear eccentricity, ATF-3, c-Jun and NPY are neuronal markers of paclitaxel-induced sensory neuropathy, however, these axotomy-like cell body reactions are infrequent and occur in mainly large-sized sensory neurons.
Publisher: Elsevier BV
Date: 2013
DOI: 10.1016/J.BCP.2012.10.023
Abstract: Dorsal root ganglion (DRG) neurons are affected by platinum-induced neurotoxicity and neurodegenerative processes associated with disturbed copper homeostasis and transport. This study aimed to understand the role of copper transporter 1 (Ctr1) in the uptake and toxicity of copper and platinum drugs in cultured rat DRG neurons, and the functional activities of rat Ctr1 (rCtr1) as a membrane transporter of copper and platinum drugs. Heterologous expression of rCtr1 in HEK293 cells (HEK/rCtr1 cells) increased the uptake and cytotoxicity of copper, oxaliplatin, cisplatin and carboplatin, in comparison to isogenic vector-transfected control cells. Cultured rat DRG neurons endogenously expressed rCtr1 protein on their neuronal cell body plasma membranes and cytoplasm, and displayed substantial capacity for taking up copper, but were resistant to copper toxicity. The uptake of copper by both cultured rat DRG neurons and HEK/rCtr1 cells was saturable and inhibited by cold temperature, silver and zinc, consistent with it being mediated by rCtr1. Cultured rat DRG neurons accumulated platinum during their exposure to oxaliplatin and were sensitive to oxaliplatin cytotoxicity. The accumulation of platinum by both cultured rat DRG neurons and HEK/rCtr1 cells, during oxaliplatin exposure, was saturable and temperature dependent, but was inhibited by copper only in HEK/rCtr1 cells. In conclusion, rCtr1 can transport copper and platinum drugs, and sensitizes cells to their cytotoxicities. DRG neurons display substantial capacity for accumulating copper via a transport process mediated by rCtr1, but appear able to resist copper toxicity and use alternative mechanisms to take up oxaliplatin.
Publisher: Wiley
Date: 28-10-2015
DOI: 10.1111/JNC.13355
Abstract: Platinum-based anticancer drugs cause peripheral neurotoxicity by damaging sensory neurons within the dorsal root ganglia (DRG), but the mechanisms are incompletely understood. The roles of platinum DNA binding, transcription inhibition and altered cell size were investigated in primary cultures of rat DRG cells. Click chemistry quantitative fluorescence imaging of RNA-incorporated 5-ethynyluridine showed high, but wide ranging, global levels of transcription in in idual neurons that correlated with their cell body size. Treatment with platinum drugs reduced neuronal transcription and cell body size to an extent that corresponded to the amount of preceding platinum DNA binding, but without any loss of neuronal cells. The effects of platinum drugs on neuronal transcription and cell body size were inhibited by blocking platinum DNA binding with sodium thiosulfate, and mimicked by treatment with a model transcriptional inhibitor, actinomycin D. In vivo oxaliplatin treatment depleted the total RNA content of DRG tissue concurrently with altering DRG neuronal size. These findings point to a mechanism of chemotherapy-induced peripheral neurotoxicity, whereby platinum DNA damage induces global transcriptional arrest leading in turn to neuronal atrophy. DRG neurons may be particularly vulnerable to this mechanism of toxicity because of their requirements for high basal levels of global transcriptional activity. Findings point to a new stepwise mechanism of chemotherapy-induced peripheral neurotoxicity, whereby platinum DNA damage induces global transcriptional arrest leading in turn to neuronal atrophy. Dorsal root ganglion neurons may be particularly vulnerable to this neurotoxicity because of their high global transcriptional outputs, demonstrated in this study by click chemistry quantitative fluorescence imaging.
Publisher: Royal Society of Chemistry (RSC)
Date: 2008
DOI: 10.1039/B716925F
Publisher: American Society for Microbiology
Date: 02-2003
DOI: 10.1128/AAC.47.2.820-823.2003
Abstract: A comparative in vivo pharmacokinetic study of florfenicol was conducted in 18 crossbred pigs infected with Actinobacillus pleuropneumoniae following intravenous (i.v.), intramuscular (i.m.), or oral (p.o.) administration of a single dose of 20 mg/kg. The disease model was confirmed by clinical signs, X rays, pathohistologic examinations, and organism isolation. Florfenicol concentrations in plasma were determined by a validated high-performance liquid chromatography method with UV detection at a wavelength of 223 nm. Pharmacokinetic parameters were calculated by using the MCPKP software (Research Institute of Traditional Chinese Veterinary Medicine, Lanzhou, China). The disposition of florfenicol after a single i.v. bolus was described by a two-compartment model with values for the half-life at α phase ( t 1/2α ), the half-life at β phase ( t 1/2β ), the area under the concentration-time curve (AUC 0-∞ ), and the volume of distribution at steady state ( V ss ) of 0.37 h, 2.91 h, 64.86 μg · h/ml, and 1.2 liter/kg, respectively. The concentration-time data fitted the one-compartment (after i.m.) and two-compartment (after p.o.) models with first-order absorption. The values for the maximum concentration of drug in serum ( C max ), t 1/2α , t 1/2β , and bioavailability after i.m. and p.o. dosing were 4.00 and 8.11 μg/ml, 0.12 and 3.91 h, 13.88 and 16.53 h, and 122.7 and 112.9%, respectively, for the two models. The study showed that florfenicol was absorbed quickly and completely, distributed widely, and eliminated slowly in the infected pigs, and there was no statistically significant difference between the pharmacokinetic profiles for the infected and healthy pigs.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Wiley
Date: 10-2004
DOI: 10.1111/J.1440-1681.2004.03065.X
Abstract: A specific and efficient liquid chromatography-mass spectrometry (LC-MS) method was established for monitoring patient plasma cyclophosphamide levels in a phase I trial of an oral cyclophosphamide-based combination chemotherapy regimen. An Agilent 1100 Series LC-MSD system (Agilent Technologies, Avondale, PA, USA), with a single quadrupole mass detector using a positive atmospheric pressure chemical ionization (APCI) interface and single ion monitoring at m/z 261, was used. Chromatography was performed using a LUNA C8 5 microm 30 x 4.6 mm stainless steel column (Phenomenex, Torrance, CA, USA) and a mobile phase of aqueous acetonitrile pumped at a flow rate of 0.7 mL/min. High-throughput solid-phase s le extraction was performed using a Gilson ASPEC XL4 system (Gilson Medical, Middleton, WI, USA) controlled by prestored programs. The standard curve for cyclophosphamide was linear over the concentration range 0.026-1.08 microg/mL (r(2) > 0.994). Intra- and interassay accuracy and precision were 97-107 and 3-10%, respectively. The limit of detection was determined to be 0.01 microg/mL. Single ion monitoring at m/z 261 provided a high degree of specificity without interference from the matrix or other chemotherapy drugs. Automated s le processing allowed the analysis of a large number of plasma s les from a clinical trial of repeated daily oral dosing of cyclophosphamide. One hour after dosing, cyclophosphamide was detected in 98 of 106 plasma specimens at concentrations ranging between 0.03 and 4.88 microg/mL. Twenty-four hours after dosing, cyclophosphamide was detected in 72 of 77 plasma specimens at concentrations ranging between 0.06 and 3.13 microg/mL. There were no time-dependent changes in cyclophosphamide concentration during the 43 day period of repeated daily oral dosing. There was no correlation between cyclophosphamide dose and plasma concentration, despite the wide range of doses given in the clinical trial (50-125 mg/m(2)). We conclude that a solid-phase extraction LC-MS technique was validated for determining cyclophosphamide in human plasma. Interoccasion variability in the rate of oral absorption and in the clearance of systemically available drug may have contributed to the wide range of cyclophosphamide concentrations found at 1 and 24 h after tablet ingestion.
Publisher: Springer Science and Business Media LLC
Date: 19-02-2019
DOI: 10.1038/S41598-019-38667-8
Abstract: Oxaliplatin is important for the clinical treatment of colorectal cancer and other gastrointestinal malignancies, but tumour resistance is limiting. Several oxaliplatin transporters were previously identified but their relative contributions to determining oxaliplatin tumour responses and gastrointestinal tumour cell sensitivity to oxaliplatin remains unclear. We studied clinical associations between tumour expression of oxaliplatin transporter candidate genes and patient response to oxaliplatin, then experimentally verified associations found with MRP2 in models of human gastrointestinal cancer. Among 18 oxaliplatin transporter candidate genes, MRP2 was the only one to be differentially expressed in the tumours of colorectal cancer patients who did or did not respond to FOLFOX chemotherapy. Over-expression of MRP2 (endogenously in HepG2 and PANC-1 cells, or induced by stable transfection of HEK293 cells) decreased oxaliplatin accumulation and cytotoxicity but those deficits were reversed by inhibition of MRP2 with myricetin or siRNA knockdown. Mice bearing subcutaneous HepG2 tumour xenografts were sensitised to oxaliplatin antitumour activity by concurrent myricetin treatment with little or no increase in toxicity. In conclusion, MRP2 limits oxaliplatin accumulation and response in human gastrointestinal cancer. Screening tumour MRP2 expression levels, to select patients for treatment with oxaliplatin-based chemotherapy alone or in combination with a MRP2 inhibitor, could improve treatment outcomes.
Publisher: Elsevier BV
Date: 06-2006
DOI: 10.1016/J.JCHROMB.2006.03.063
Abstract: We have developed a specific assay for cisplatin in human plasma ultrafiltrate (PUF) and cell culture medium ultrafiltrate (MUF) using HPLC on-line with inductively coupled plasma mass spectrometry (ICP-MS). Separation of cisplatin (6 min) and monohydrated cisplatin (12 min) was achieved using a muBondapak C(18) column (Waters) and a mobile phase (0.075 mM sodium dodecyl sulfate and 3% methanol, adjusted to pH 2.5 with triflic acid) pumped at a flow rate of 0.5 mL/min. The analytes were detected with little background interference by ICP-MS monitoring of platinum masses (m/z 194/195). Calibration curves were linear over three orders of magnitude (0.05-8 microM) and the limit of quantitation was 0.1 microM. Intra- and inter-assay accuracy (range 91.6-113%) and precision (range 1.00-12.3%) were acceptable for PUF and MUF. The method was applied to determining cisplatin during ex vivo incubation of the drug in whole human blood at 37 degrees C. In conclusion, a specific, sensitive and reliable HPLC-ICP-MS assay has been established for determining intact cisplatin in PUF and MUF.
Publisher: Wiley
Date: 03-2006
Publisher: Bentham Science Publishers Ltd.
Date: 14-10-2015
DOI: 10.2174/1389450116666150330113506
Abstract: The superfamily of human ATP-binding cassette (ABC) transporters comprises seven subfamilies (ABCA to G) with 48 members. In addition to their profound physiological and pharmacological functions, ABC transporters play important roles in instigating multidrug resistance (MDR) in cancer by mediating the efflux of many anticancer drugs, particularly, ABCB1, ABCG2 and ABCC subfamily members. Previous development of ABCB1 transporter inhibitors has provided insights into seeking novel strategies in developing new classes of compound that inhibit ABCB1 and other MDRrelated ABC transporters. We herein review and evaluate current evidence in this area, with an emphasis on experimental and investigational agents that are under preclinical and clinical tests, including tyrosine kinase inhibitors, natural products, microRNAs and novel chemical entities. New strategies targeting ABC transporters in cancer stem cells and future perspectives in this field are also discussed.
Publisher: Springer Science and Business Media LLC
Date: 14-01-2020
Publisher: MDPI AG
Date: 08-09-2019
Abstract: Our recent publications showed that multidrug resistance protein 2 (MRP2, encoded by the ABCC2 gene) conferred oxaliplatin resistance in human liver cancer HepG2 cells. However, the contribution of MRP2 to oxaliplatin resistance remains unclear in colorectal and pancreatic cancer lines. We investigated the effects of silencing MRP2 by siRNA on oxaliplatin accumulation and sensitivity in human colorectal cancer Caco-2 cells and pancreatic cancer PANC-1 cells. We characterized the effects of oxaliplatin on MRP2 ATPase activities using membrane vesicles. Over-expression of MRP2 (endogenously in Caco-2 and PANC-1 cells) was associated with decreased oxaliplatin accumulation and cytotoxicity, but those deficits were reversed by inhibition of MRP2 with myricetin or siRNA knockdown. Silencing MRP2 by siRNA increased oxaliplatin-induced apoptotic rate in Caco-2 and PANC-1 cells. Oxaliplatin stimulated MRP2 ATPase activity with a concentration needed to reach 50% of the maximal stimulation (EC50) value of 8.3 ± 0.7 µM and Hill slope 2.7. In conclusion, oxaliplatin is a substrate of MRP2 with possibly two binding sites, and silencing MRP2 increased oxaliplatin accumulation and cytotoxicity in two widely available gastrointestinal tumour lines (PANC-1 and Caco-2).
Publisher: SAGE Publications
Date: 2009
Abstract: Oxaliplatin and related chemotherapeutic drugs cause painful chronic peripheral neuropathies in cancer patients. We investigated changes in neuronal size profiles and neurofilament immunoreactivity in L5 dorsal root ganglion (DRG) tissue of adult female Wistar rats after multiple-dose treatment with oxaliplatin, cisplatin, carboplatin or paclitaxel. After treatment with oxaliplatin, phosphorylated neurofilament heavy subunit (pNF-H) immunoreactivity was reduced in neuronal cell bodies, but unchanged in nerve fibres, of the L5 DRG. Morphometric analysis confirmed significant changes in the number (-75% P 0.0002) and size (-45% P 0.0001) of pNF-H-immunoreactive neurons after oxaliplatin treatment. pNF-H-immunoreactive neurons had overlapping size profiles and co-localisation with neurons displaying cell body immunoreactivity for parvalbumin, non-phospho-specific neurofilament medium subunit (NF-M) and non-phospho-specific neurofilament heavy subunit (NF-H), in control DRG. However, there were no significant changes in the numbers of neurons with immunoreactivity for parvalbumin (4.6%, P = 0.82), NF-M (-1%, P = 0.96) or NF-H (0% P = 0.93) after oxaliplatin treatment, although the sizes of parvalbumin (-29%, P = 0.047), NF-M (-11%, P = 0.038) and NF-H (-28% P = 0.0033) immunoreactive neurons were reduced. In an independent comparison of different chemotherapeutic agents, the number of pNF-H-immunoreactive neurons was significantly altered by oxaliplatin (-77.2% P 0.0001) and cisplatin (-35.2% P = 0.03) but not by carboplatin or paclitaxel, and their mean cell body area was significantly changed by oxaliplatin (-31.1% P = 0.008) but not by cisplatin, carboplatin or paclitaxel. This study has demonstrated a specific pattern of loss of pNF-H immunoreactivity in rat DRG tissue that corresponds with the relative neurotoxicity of oxaliplatin, cisplatin and carboplatin. Loss of pNF-H may be mechanistically linked to oxaliplatin-induced neuronal atrophy, and serves as a readily measureable endpoint of its neurotoxicity in the rat model.
Publisher: American Society for Pharmacology & Experimental Therapeutics (ASPET)
Date: 23-05-2011
Abstract: The organic cation/carnitine transporters OCTN1 and OCTN2 are related to other organic cation transporters (OCT1, OCT2, and OCT3) known for transporting oxaliplatin, an anticancer drug with dose-limiting neurotoxicity. In this study, we sought to determine whether OCTN1 and OCTN2 also transported oxaliplatin and to characterize their functional expression and contributions to its neuronal accumulation and neurotoxicity in dorsal root ganglion (DRG) neurons relative to those of OCTs. [(14)C]Oxaliplatin uptake, platinum accumulation, and cytotoxicity were determined in OCTN-overexpressing human embryonic kidney (HEK) 293 cells and primary cultures of rat DRG neurons. Levels of mRNA and functional activities of rat (r)Octns and rOcts in rat DRG tissue and primary cultures were characterized using reverse transcription-polymerase chain reaction and uptake of model OCT/OCTN substrates, including [(3)H]1-methyl-4-phenylpyridinium (MPP(+)) (OCT1-3), [(14)C]tetraethylammonium bromide (TEA(+)) (OCT1-3 and OCTN1/2), [(3)H]ergothioneine (OCTN1), and [(3)H]l-carnitine (OCTN2). HEK293 cells overexpressing rOctn1, rOctn2, human OCTN1, and human OCTN2 showed increased uptake and cytotoxicity of oxaliplatin compared with mock-transfected HEK293 controls in addition, both uptake and cytotoxicity were inhibited by ergothioneine and L-carnitine. The uptake of ergothioneine mediated by OCTN1 and of L-carnitine mediated by OCTN2 was decreased during oxaliplatin exposure. rOctn1 and rOctn2 mRNA was readily detected in rat DRG tissue, and they were functionally active in cultured rat DRG neurons, more so than rOct1, rOct2, or rOct3. DRG neuronal accumulation of [(14)C]oxaliplatin and platinum during oxaliplatin exposure depended on time, concentration, temperature, and sodium and was inhibited by ergothioneine and to a lesser extent by L-carnitine but not by MPP(+). Loss of DRG neuronal viability during oxaliplatin exposure was inhibited by ergothioneine but not by L-carnitine or MPP(+). OCTN1 and OCTN2 both transport oxaliplatin and are functionally expressed by DRG neurons. OCTN1-mediated transport of oxaliplatin appears to contribute to its neuronal accumulation and treatment-limiting neurotoxicity more so than OCTN2 or OCTs.
Publisher: SAGE Publications
Date: 2010
Abstract: ATP7A, ATP7B and CTR1 are metal transporting proteins that control the cellular disposition of copper and platinum drugs, but their expression in dorsal root ganglion (DRG) tissue and their role in platinum-induced neurotoxicity are unknown. To investigate the DRG expression of ATP7A, ATP7B and CTR1, lumbar DRG and reference tissues were collected for real time quantitative PCR, RT-PCR, immunohistochemistry and Western blot analysis from healthy control adult rats or from animals treated with intraperitoneal oxaliplatin (1.85 mg/kg) or drug vehicle twice weekly for 8 weeks. In DRG tissue from healthy control animals, ATP7A mRNA was clearly detectable at levels similar to those found in the brain and spinal cord, and intense ATP7A immunoreactivity was localised to the cytoplasm of cell bodies of smaller DRG neurons without staining of satellite cells, nerve fibres or co-localisation with phosphorylated heavy neurofilament subunit (pNF-H). High levels of CTR1 mRNA were detected in all tissues from healthy control animals, and strong CTR1 immunoreactivity was associated with plasma membranes and vesicular cytoplasmic structures of the cell bodies of larger-sized DRG neurons without co-localization with ATP7A. DRG neurons with strong expression of ATP7A or CTR1 had distinct cell body size profiles with minimal overlap between them. Oxaliplatin treatment did not alter the size profile of strongly ATP7A-immunoreactive neurons but significantly reduced the size profile of strongly CTR1-immunoreactive neurons. ATP7B mRNA was barely detectable, and no specific immunoreactivity for ATP7B was found, in DRG tissue from healthy control animals. In conclusion, adult rat DRG tissue exhibits a specific pattern of expression of copper transporters with distinct subsets of peripheral sensory neurons intensely expressing either ATP7A or CTR1, but not both or ATP7B. The neuron subtype-specific and largely non-overlapping distribution of ATP7A and CTR1 within rat DRG tissue may be required to support the potentially differing cuproenzyme requirements of distinct subsets of sensory neurons, and could influence the transport and neurotoxicity of oxaliplatin.
No related grants have been discovered for Johnson Liu.