Determination of platinum complexes in clinical samples by a rapid flameless atomic absorption spectrometry assay

The Impact of Integrin-Mediated Matrix Adhesion on Cisplatin Resistance of W1 Ovarian Cancer Cells

BACKGROUND

Tumor cell binding to the microenvironment is regarded as the onset of therapeutic resistance, referred to as cell adhesion mediated drug resistance (CAM-DR). Here we elucidate whether CAM-DR occurs in ovarian cancer cells and contributes to still-existing cisplatin resistance.

METHODS

Cultivation of W1 and cisplatin-resistant W1CR human ovarian cancer cells on collagen-type I (COL1) was followed by whole genome arrays, MTT assays focusing cisplatin cytotoxicity, and AAS detection of intracellular platinum levels. Expression of cisplatin transporters Ctr1 and MRP2 was analyzed. Mechanistic insight was provided by lentiviral β1-integrin (ITGB1) knockdown, or inhibition of integrin-linked kinase (ILK).

RESULTS

EC₅₀ values of cisplatin cytotoxicity increased twofold when W1 and W1CR cells were cultivated on COL1, associated with significantly diminished intracellular platinum levels. Transporter deregulation could not be detected at mRNA levels but appears partially responsible at protein levels. The ITGB1 knockdown confirms that CAM-DR follows a COL1/ITGB1 signaling axis in W1 cells; thus, a blockade of ILK re-sensitized W1 cells on COL1 for cisplatin. In contrast, CAM-DR adds to cisplatin resistance in W1CR cells independent of ITGB1.

CONCLUSIONS

CAM-DR appears relevant for ovarian cancer cells, adding to existing genetic resistance and thus emerges as a target for sensitization strategies.

Relevance of copper transporter 1 and organic cation transporters 1-3 for oxaliplatin uptake and drug resistance in colorectal cancer cells

Oxaliplatin is a routinely used drug in the treatment of colorectal cancer. However, development of resistance is a major hurdle of the chemotherapy success. Defects in cellular accumulation represent a frequently reported feature of cells with acquired resistance to platinum drugs. Nevertheless, the mechanisms of oxaliplatin uptake and their role in oxaliplatin resistance remain poorly elucidated. The aim of this study was to investigate the relevance of copper transporter 1 (CTR1) and organic cation transporters 1-3 (OCT1-3) for oxaliplatin uptake and resistance to the drug in sensitive and oxaliplatin-resistant ileocecal colorectal adenocarcinoma cells. Co-incubation with copper(ii) sulfate, a CTR1 substrate, significantly decreased oxaliplatin accumulation but not cytotoxicity in both cell lines. Pre- as well as co-incubation with the OCT1 inhibitor atropine led to a significant reduction in oxaliplatin accumulation in sensitive but not in resistant cells. However, oxaliplatin cytotoxicity was also decreased in the presence of atropine in both cell lines. Cimetidine, an inhibitor of OCT2, induced a significant reduction in the cellular accumulation and potency of oxaliplatin in sensitive and resistant cells. An inhibitor of OCT3, decynium-22, had no influence on oxaliplatin accumulation and cytotoxicity in either cell line. No differences in the transporter expressions were observed between the cell lines, drug-treated or not, either at the mRNA or protein levels. A fluorescent oxaliplatin derivative CFDA-oxPt co-localized with CTR1, OCT1 and OCT2 in sensitive cells, but only with CTR1 and OCT2 in the resistant cell line. Our results suggest that oxaliplatin is transported into the cell by CTR1 in both cell lines. However, contribution of CTR1-mediated uptake to resistance seems unlikely. Uptake of oxaliplatin via OCT1 appears to take place in the sensitive but not in the resistant cell line underscoring the transporter relevance for oxaliplatin resistance. OCT2 is likely to be involved in the uptake of oxaliplatin to a similar extent in both cell lines suggesting no major contribution of this transporter to resistance. In contrast, OCT3 appears to be irrelevant for oxaliplatin transport into the cell and resistance.

Comparison of different sample preparation methods for platinum determination in cultured cells by graphite furnace atomic absorption spectrometry

BACKGROUND

Platinum-based agents are widely used in chemotherapy against solid tumors and insufficient intracellular drug accumulation is one of the leading causes of platinum resistance which is associated with poor survival of tumor patients. Thus, the detection of intracellular platinum is pivotal for studies aiming to overcome platinum resistance. In the present study, we aimed to establish a reliable graphite furnace atomic absorption spectrometry (GFAAS)-based assay to quantify the intracellular platinum content for cultured cells.

METHODS

Several most commonly applied cell preparation methods, including 0.2% HNO3, 0.2% Triton X-100, concentrated nitric acid, RIPA combined with concentrated nitric acid and hydroxide, followed by GFAAS for platinum detection were compared in ovarian, cervical and liver cancer cell lines to obtain the optimal one, and parameters regarding linearity, accuracy, precision and sensitivity were evaluated. Influence of other metals on platinum detection and the storage conditions of samples were also determined.

RESULTS

The treatment of cells with 0.2% HNO3 was superior to other approaches with fewer platinum loss and better repeatability. The recovery rate and precision of this method were 97.3%-103.0% and 1.4%-3.8%, respectively. The average recoveries in the presence of other metals were 95.1%-103.1%. The detection limit was 13.23 ug/L. The recovery rate of platinum remained acceptable even in cell samples stored in -20 °C or -80 °C for two months.

DISCUSSION

After comparison, we found that 0.2% HNO3 was optimal for intracellular platinum quantification based on GFAAS, which presented values compatible with that of inductively-coupled plasma mass-spectrometry (ICP-MS), and this is partially attributed to the simplicity of this method. Moreover, the assay was proved to be accurate, sensitive, cost-effective and suitable for the research of platinum-based antitumor therapy.

HIPEC ROC I: a phase I study of cisplatin administered as hyperthermic intraoperative intraperitoneal chemoperfusion followed by postoperative intravenous platinum-based chemotherapy in patients with platinum-sensitive recurrent epithelial ovarian cancer

This phase I study tested the safety, feasibility, pharmacokinetics and pharmacodynamics of cisplatin administered as hyperthermic intraoperative intraperitoneal chemoperfusion (HIPEC) in patients with platinum-sensitive recurrent epithelial ovarian cancer (EOC) undergoing secondary cytoreductive surgery followed by postoperative platinum-based intravenous chemotherapy. Twelve patients with operable, recurrent platinum-sensitive EOC (recurrence ≥6 months after first-line therapy) were included according to the classical 3+3 dose-escalation design at three dose levels-60, 80 and 100 mg/m(2). After surgical cytoreduction, a single dose of cisplatin was administered via HIPEC for 90 min at 41-43°C. Postoperatively, all patients were treated with standard intravenous platinum-based combination chemotherapy. One of six patients experienced a dose-limiting toxicity (grade 3 renal toxicity) at a dose of 100 mg/m(2). The remaining five patients treated with 100 mg/m(2) tolerated their treatment well. The recommended phase II dose was established at 100 mg/m(2). The mean peritoneal-to-plasma AUC ratio was 19·5 at the highest dose level. Cisplatin-induced DNA adducts were confirmed in tumor samples. Common postoperative grade 1-3 toxicities included fatigue, postoperative pain, nausea, and surgical site infection. The ability to administer standard intravenous platinum-based chemotherapy after HIPEC was uncompromised. Cisplatin administered as HIPEC at a dose of 100 mg/m(2) has an acceptable safety profile in selected patients undergoing secondary cytoreductive surgery for platinum-sensitive recurrent EOC. Favorable pharmacokinetic and pharmacodynamic properties of HIPEC with cisplatin were confirmed at all dose levels, especially at 100 mg/m(2). The results are encouraging to determine the efficacy of HIPEC as a complementary treatment in patients with EOC.

A phase I study of sorafenib in combination with S-1 plus cisplatin in patients with advanced gastric cancer

BACKGROUND

Sorafenib inhibits several receptor tyrosine kinases involved in tumor progression and angiogenesis. S-1, an oral fluorouracil antitumor drug, plus cisplatin (CDDP) is the standard regimen for advanced gastric adenocarcinoma (AGC) in Japan. The purpose of this phase I study was to evaluate the safety, pharmacokinetics, and preliminary efficacy of sorafenib in combination with S-1 plus CDDP.

METHODS

Patients with histologically confirmed previously untreated AGC were evaluated for eligibility and treated with sorafenib (400 mg bid, days 1-35), S-1 (40 mg/m(2) bid, days 1-21), and CDDP (60 mg/m(2), day 8). Treatment was continued until disease progression or unacceptable toxicity. Pharmacokinetics for sorafenib, 5-FU, and CDDP were investigated in cycle 1.

RESULTS

Thirteen patients were enrolled and received at least one dose of the study treatment. No specific or serious adverse event was newly reported in this study. Five patients had partial response and 8 had stable disease as the best response. Pharmacokinetic analysis showed no significant differences in the exposures of sorafenib when administered alone or in combination with S-1 and CDDP.

CONCLUSIONS

The present phase I study demonstrates the acceptable toxicity and preliminary efficacy of combined treatment with S-1, CDDP, and sorafenib.

Endoplasmic reticulum stress is involved in the response of human laryngeal carcinoma cells to Carboplatin but is absent in Carboplatin-resistant cells

The major obstacle of successful tumor treatment with carboplatin (CBP) is the development of drug resistance. In the present study, we found that following treatment with CBP the amount of platinum which enters the human laryngeal carcinoma (HEp2)-derived CBP-resistant (7T) cells is reduced relative to the parental HEp2. As a consequence, the formation of reactive oxidative species (ROS) is reduced, the induction of endoplasmic reticulum (ER) stress is diminished, the amount of inter- and intrastrand cross-links is lower, and the induction of apoptosis is depressed. In HEp2 cells, ROS scavenger tempol, inhibitor of ER stress salubrinal, as well as gene silencing of ER stress marker CCAAT/enhancer-binding protein (CHOP) increases their survival and renders them as resistant to CBP as 7T cell subline but did not influence the survival of 7T cells. Our results suggest that in HEp2 cells CBP-induced ROS is a stimulus for ER stress. To the contrary, despite the ability of CBP to induce formation of ROS and activate ER stress in 7T cells, the cell death mechanism in 7T cells is independent of ROS induction and activation of ER stress. The novel signaling pathway of CBP-driven toxicity that was found in the HEp2 cell line, i.e. increased ROS formation and induction of ER stress, may be predictive for therapeutic response of epithelial cancer cells to CBP-based therapy.

Contribution of intracellular ATP to cisplatin resistance of tumor cells

Decreased cellular accumulation of cisplatin is a frequently observed mechanism of resistance to the drug. Beside passive diffusion, several cellular proteins using ATP hydrolysis as an energy source are assumed to be involved in cisplatin transport in and out of the cell. This investigation aimed at clarifying the contribution of intracellular ATP as an indicator of energy-dependent transport to cisplatin resistance using the A2780 human ovarian adenocarcinoma cell line and its cisplatin-resistant variant A2780cis. Depletion of intracellular ATP with oligomycin significantly decreased cellular platinum accumulation (measured by flameless atomic absorption spectrometry) in sensitive but not in resistant cells, and did not affect cisplatin efflux in both cell lines. Inhibition of Na(+),K(+)-ATPase with ouabain reduced platinum accumulation in A2780 cells but to a lesser extent compared with oligomycin. Western blot analysis revealed lower expression of Na(+),K(+)-ATPase α(1) subunit in resistant cells compared with sensitive counterparts. The basal intracellular ATP level (determined using a bioluminescence-based assay) was significantly higher in A2780cis cells than in A2780 cells. Our results highlight the importance of ATP-dependent transport, among other processes mediated by Na(+),K(+)-ATPase, for cisplatin influx in sensitive cells. Cellular platinum accumulation in resistant cells is reduced and less dependent on energy sources, which may partly result from Na(+),K(+)-ATPase downregulation. Our data suggest the involvement of other ATP-dependent processes beside those regulated by Na(+),K(+)-ATPase. Higher basal ATP level in cisplatin-resistant cells, which appears to be a consequence of enhanced mitochondrial ATP production, may represent a survival mechanism established during development of resistance.

Preparation and characterization of artificial antigens for cadmium and lead

Cadmium and lead were conjugated to two carrier proteins using a bifunctional chelator [2-(4-aminobenzyl)-diethylenetriaminepentaacetic acid] to synthesize artificial antigens for cadmium and lead. The techniques, including ultraviolet spectrometry, circular dichroism, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and inductively coupled plasma optical emission spectroscopy, were utilized for characterizing the artificial antigens. The results of ultraviolet spectrometry showed characteristic absorption peak shifts between conjugates and carrier proteins. Circular dichroism resulted that the second structure of the conjugates was α-helix. The sodium dodecyl sulfate polyacrylamide gel electrophoresis results revealed the differences of band migration and molecular weight among antigens, chelator protein conjugate, and carrier proteins. The result of coupling ratios revealed that the metal content of the antigens was much higher than that of carrier proteins. These results indicated that the artificial antigens of cadmium and lead were synthesized successfully and had potential application in immunoassays of cadmium and lead ions.

Relevance of copper transporter 1 for cisplatin resistance in human ovarian carcinoma cells

Defects in intracellular accumulation of the antitumour drug cisplatin are a commonly observed feature in the cells selected for cisplatin resistance. Copper transporter 1 (CTR1) has been suggested to play an important role in drug uptake and resistance. Here, we describe a detailed investigation of the involvement of CTR1 in cisplatin uptake and its relevance for cisplatin resistance using a well characterised sensitive/cisplatin-resistant cell line pair: A2780 human ovarian carcinoma cell line and its cisplatin-resistant variant A2780cis. A2780cis cells showed decreased cisplatin accumulation and lower CTR1 expression compared to A2780 cells. Co-incubation with copper sulphate affected neither cisplatin accumulation (determined by flameless atomic absorption spectrometry) nor its cytotoxicity (determined using an MTT-assay, MTT=3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide). In both cell lines, CTR1 was localised near the nucleus as found using confocal fluorescence microscopy. The steady-state localisation of the protein in perinuclear region appears to involve its continuous endocytosis from cell surface. In contrast to copper, cisplatin exposure had no influence on the sub cellular localisation of CTR1. Co-localisation between CTR1 and a fluorescent cisplatin analogue labelled with carboxyfluorescein-diacetate could be observed in vesicular structures when continuous retrieval of the protein from cell membrane was inhibited. Our results strongly suggest that CTR1 mediates cisplatin uptake in the cell lines studied. Upon its transport across the plasma membrane by CTR1 the platinum drug is likely to be internalised along with the protein. Our findings imply that reduced CTR1 expression accounts for decreased cisplatin accumulation and represents one of the determinants of cisplatin resistance in A2780cis cell line.

Effect of reactivity on cellular accumulation and cytotoxicity of oxaliplatin analogues

The purpose of this study was to systematically investigate the relationships between reactivity, cellular accumulation, and cytotoxicity of a panel of oxaliplatin analogues with different leaving groups in human carcinoma cells. The reactivity of the complexes towards the nucleotides 2'-deoxyguanosine 5'-monophosphate and 2'-deoxyadenosine 5'-monophosphate was studied using capillary electrophoresis. Cellular accumulation and cytotoxicity were measured in an oxaliplatin-sensitive and oxaliplatin-resistant ileocecal colorectal adenocarcinoma cell line pair (HCT-8/HCT-8ox). Platinum concentrations were determined by flameless atomic absorption spectrometry. The 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to assess cytotoxicity. Early cellular platinum accumulation was predominantly affected by lipophilicity. A relationship between reactivity and cellular accumulation was observed for three of four platinum complexes investigated, whereas the most lipophilic oxaliplatin analogue was an exception. Increased reactivity and reduced lipophilicity were associated with high cytotoxic activity. Resistance was influenced by lipophilicity but not by reactivity. The observed relationships may help in the design of analogues with high antitumoral activity in oxaliplatin-sensitive as well as oxaliplatin-resistant cells.

Effect of age on systemic exposure and haematological toxicity of carboplatin in advanced non-small cell lung cancer patients

The aim of this study was to evaluate systemic exposure to carboplatin and its haematological toxicity in patients with advanced non-small cell lung cancer both older and younger than 70 years when the target area under the curve (AUC) in elderly patients was reduced by 20%. For this purpose, a population pharmacokinetic model was developed and the haematological toxicity of the drug was assessed. A total of 33 patients received carboplatin on day 1 and gemcitabine (1250 mg/m(2) ) on days 1 and 8. This schedule was repeated every 21 days. The Calvert-Crokcoft-Gault formula was employed to calculate a dose of carboplatin with a target AUC of 5 mg/min./mL in patients under 70 years and 4 mg/min./mL in patients aged 70 or older. The data of 24 patients were treated for population modelling performed with the nonmem (University of California, San Francisco, CA, USA) approach. Haematological toxicity was evaluated for all 33 patients enrolled in the study. The carboplatin systemic exposure measured by the AUC (mg/min./mL) was 5.98 (5.45; 6.51) and 5.36 (5.02; 5.69) for the younger patients and older groups, respectively. No significant differences were observed between the two groups with respect to rates of grade 3+ anaemia, neutropenia or thrombocytopenia. In clinical practice, a target AUC of 4 mg/min./mL carboplatin is applied to patients aged 70 and over, but the actual systemic exposure to the drug is higher. This supports a target AUC of 4 mg/min./mL carboplatin for patients older than 70 years when the dose is calculated by means of the Calvert-Crokcoft-Gault formula.

Enhancing lipophilicity as a strategy to overcome resistance against platinum complexes?

Decreased influx represents one of the major resistance mechanisms of platinum complexes. In order to address the question if this mechanism of resistance can be overcome by enhancing the lipophilicity of platinum complexes, we investigated the influence of lipophilicity on cellular accumulation and cytotoxicity in a panel of oxaliplatin analogues with different carrier ligands. Cellular accumulation, DNA platination and cytotoxicity were measured in a cisplatin-sensitive and -resistant ovarian carcinoma (A2780/A2780cis) and in an oxaliplatin-sensitive and -resistant ileocecal colorectal adenocarcinoma (HCT-8/HCT-8ox) cell line pair. Platinum concentrations were determined by flameless atomic absorption spectrometry or adsorptive stripping voltammetry. Passive diffusion represented the main influx mechanism of oxaliplatin analogues during the first minutes of incubation as indicated by a correlation between lipophilicity and early influx rate. Afterwards, the predominant influx mechanism was lipophilicity-independent. More lipophilic complexes showed a reduced cytotoxic activity, although the early influx rate was increased. The resistance profiles of the two cell line pairs were found to be different: HCT-8ox cells were less resistant against more lipophilic complexes, whereas A2780cis cells exhibited a comparable degree of resistance against all investigated compounds. However, the reduction in resistance factor of HCT-8ox cells cannot be explained by increased influx suggesting that other resistance mechanisms are circumvented upon exposure to more lipophilic compounds. Though resistance against more lipophilic platinum complexes analogues is lower we conclude that enhancing lipophilicity is not a successful strategy to overcome platinum resistance as higher lipophilicity is also associated with lower cytotoxic activity.

Population pharmacokinetics of high-dose carboplatin in children and adults

INTRODUCTION

Although for conventional dosing of carboplatin, several strategies are available to individualize the dose based on renal function measurements, such approaches are still rare for high-dose regimens with autologous stem cell support. The purpose of this study was to investigate the influence of patient- and regimen-specific factors on the pharmacokinetics of carboplatin and to compare the performance of different dose individualization strategies (Calvert, Newell, Chatelut, flat dosing, dosing according to body surface area).

PATIENTS AND METHODS

A combined data set with 69 patients from five studies, including 13 pediatric patients, was subject to a population pharmacokinetic analysis using NONMEM.

RESULTS

The covariate analysis revealed that carboplatin clearance after high-dose chemotherapy was highly related to creatinine clearance, body height, and infusion duration. After inclusion of these covariates, the population parameter variability of clearance decreased from 53% in the base model to 21% in the final model. We also developed an alternative model that related body weight, instead of height, to clearance by means of allometric scaling. An evaluation of the predictive performance of existing a priori dose individualization strategies revealed that flat dosing is appropriate for adult patients with normal renal function receiving a 1-hour infusion. For a long-term infusion schedule, a dose increase may be necessary. The existing dosing strategies performed poorly for the children in our data set. For this subpopulation, our allometric scaling model may be most appropriate.

CONCLUSION

The two population pharmacokinetic models presented can be applied to estimate individual carboplatin clearance in high-dose chemotherapy based on body weight or height, infusion duration, and creatinine clearance. After prospective evaluation, our models may be suitable for dose adjustments.

Colloidal gold probe-based immunochromatographic assay for the rapid detection of lead ions in water samples

One-step immunochromatographic assay (ICA) has been developed using colloidal gold-labeled monoclonal antibody probe for the rapid detection of lead ions in water samples. The ICA was based on the theory of competitive reactivity, and the results can be easily judged based on the presence or absence of a red colored test line with visual detection. Under optimal conditions, this method shows high detecting sensitivity with a LOD (limit of detection) of 50 ng/ml. Stability test indicates that the immunochromatographic strips are stable for 8 weeks at room temperature. During practical application, nanometer TiO2 is used to enrich the lead ions in water samples. The ICA is successfully applied in the measurement of lead ion concentrations in local water samples, and the results are highly consistent with that of ICP-MS. Detecting lead ions with ICA can be done within 4 min and is very useful for the rapid onsite testing.

A competitive indirect enzyme-linked immunoassay for lead ion measurement using mAbs against the lead-DTPA complex

Immunoassays for quantitative measurement of environmental heavy metals offer several advantages over other traditional methods. To develop an immunoassay for lead, Balb/c mice were immunized with a lead-chelate-protein conjugate to allow maximum exposure of the metal to the immune system. Three stable hybridoma cell lines were obtained through spleen cells fusion with Sp2/0 cells. One cell line, 2A11D11, produced mAbs with preferential selectivity and sensitivity for Pb-DTPA than DTPA, exhibiting an affinity constant of 3.34 + or - 0.24 x 10(9) M(-1). Cross reactivity (CR) with other metals were below 1%, except for Fe(III) with a CR less than 5%. This quantitative indirect ELISA for the lead ion was used to detect environmental lead content in local water sources; importantly, the results from the immunoassay were in excellent agreement with those from ICP-MS. Development of immunoassays for metal ions may thus facilitate the detection and regulation of environmental pollution.

ATP sensitizes H460 lung carcinoma cells to cisplatin-induced apoptosis

Platinum resistance of cancer cells may evolve due to a decrease in intracellular drug accumulation, decreased cell permeability or by an increased deactivation of the drug by glutathione (GSH). The aim of this study was (1) to investigate the effect of adenosine 5'-triphosphate (ATP) on the cytotoxicity of cisplatin in a large cell lung carcinoma cell line (H460), and (2) to examine the potential involvement of increased cisplatin uptake, GSH depletion and pyrimidine starvation by ATP in this effect. H460 cells were harvested and seeded (5% CO(2); 37 degrees C). Subsequently, cells were incubated with medium or ATP followed by an incubation with cisplatin. Cytotoxicity screening was analyzed by the sulforhodamine B (SRB) colorimetric assay, lactate dehydrogenase and caspase-3/7 activity. Pre-incubation for 72h with 0.3 and 3mM ATP strongly enhanced the anti-proliferative potency of cisplatin 2.9- and 7.6-fold, respectively. Moreover, after incubation of H460 cells with 0.3mM ATP the intracellular platinum concentration increased, indicating increased cisplatin uptake by ATP. ATP, despite lowering the LD(50) of cisplatin, did not modulate GSH levels in H460 cells. ATP itself showed a biphasic effect on H460 cell growth: 0.3mM inhibited H460 cell growth via the pyrimidine starvation effect, activation of caspase-3/7 and LDH leakage, while 3mM ATP showed no effect on cell growth. In conclusion, ATP sensitizes the H460 cells to cisplatin-induced apoptosis. The effect of 0.3mM ATP is not due to GSH depletion but involves increased cisplatin uptake and pyrimidine starvation due to ATP conversion to adenosine followed by cellular uptake.

Determination of intact oxaliplatin in human plasma using high performance liquid chromatography-tandem mass spectrometry

A HPLC-tandem mass spectrometry method was developed and validated for the quantitation of intact oxaliplatin in human plasma. Plasma ultrafiltrates were precipitated with acetonitrile and separation was performed on a 250 mm Beckman ODS reverse phase column using a gradient mobile phase. The mass spectrometer was operated in positive ionization mode using TurboionSpray and precursor-product ion combinations of m/z 391.1-->305.1 and 371.1-->247.0 were monitored for oxaliplatin and carboplatin, the internal standard, respectively. The lower limit of quantitation for oxaliplatin was 20 ng/ml. The linear range of the method was 20-1000 ng/ml. The between- and within-day relative standard deviations ranged from 3.1 to 7.7%, and accuracy was within 5%. This method was successfully applied in a clinical study of oxaliplatin.

Oxaliplatin-DNA adduct formation in white blood cells of cancer patients

In this study, we investigated the kinetics of oxaliplatin-DNA adduct formation in white blood cells of cancer patients in relation to efficacy as well as oxaliplatin-associated neurotoxicity. Thirty-seven patients with various solid tumours received 130 mg m(-2) oxaliplatin as a 2-h infusion. Oxaliplatin-DNA adduct levels were measured in the first cycle using adsorptive stripping voltammetry. Platinum concentrations were measured in ultrafiltrate and plasma using a validated flameless atomic absorption spectrometry method. DNA adduct levels showed a characteristic time course, but were not correlated to platinum pharmacokinetics and varied considerably among individuals. In patients showing tumour response, adduct levels after 24 and 48 h were significantly higher than in nonresponders. Oxaliplatin-induced neurotoxicity was more pronounced but was not significantly different in patients with high adduct levels. The potential of oxaliplatin-DNA adduct measurements as pharmacodynamic end point should be further investigated in future trials.

alpha(v)beta(3) Integrin-mediated drug resistance in human laryngeal carcinoma cells is caused by glutathione-dependent elimination of drug-induced reactive oxidative species

As a model for determination of the role of integrins in drug resistance, we used alpha(v)beta(3) integrin-negative human laryngeal carcinoma cell line (HEp2) and three HEp2-derived cell clones with a gradual increase of alpha(v)beta(3) integrin expression. The alpha(v)beta(3) integrin expression protects cells from cisplatin, mitomycin C, and doxorubicin. In HEp2-alpha(v)beta(3) integrin-expressing cells, the constitutive expression of Bcl-2 protein and the level of glutathione (GSH) were increased compared with HEp2 cells. Pretreatment of HEp2-alpha(v)beta(3) integrin-expressing cells with an inhibitor of GSH synthesis, buthionine sulfoximine (BSO), decreased the level of GSH and partially reverted drug resistance to all above-mentioned drugs, but it did not influence the expression of Bcl-2. Sensitivity to selected anticancer drugs did not change with overexpression of Bcl-2 in HEp2 cells, nor with silencing of Bcl-2 in HEp2-alpha(v)beta(3) integrin-expressing cells, indicating that Bcl-2 is not involved in resistance mechanism. There was no difference in DNA platination between HEp2 and HEp2-alpha(v)beta(3) integrin-expressing cells, indicating that the mechanism of drug resistance is independent of cisplatin detoxification by GSH. A strong increase of reactive oxidative species (ROS) formation during cisplatin or doxorubicin treatment in HEp2 cells was reduced in HEp2-alpha(v)beta(3) integrin-expressing cells. Since this increased elimination of ROS could be reverted by GSH depletion, we concluded that multidrug resistance is the consequence of GSH-dependent increased ability of alpha(v)beta(3)-expressing cells to eliminate drug-induced ROS.

Characterization of monoclonal antibodies for lead-chelate complexes: applications in antibody-based assays

Monoclonal antibodies against lead were generated by immunizing BALB/c mice with lead conjugated to keyhole limpet hemocyanin (KLH) via a bifunctional chelator, S-2-(4-aminobenzyl)diethylenetriamine pentaacetic acid (DTPA). Stable hybridoma cell lines were produced by fusion of murine splenocytes and SP2/0 myeloma cells. One of the hybridomas generated from this fusion (4/7) synthesized and secreted an antibody that bound tightly to Pb2+-DTPA complexes but not to metal-free DTPA. The performance for a competitive inhibition enzyme-linked immunosorbent assay (ELISA) incorporating this antibody was assessed for its sensitivity to changes in pH, ionic strength, and blocking reagents. The cross-reactivities in this ELISA were less than 3% for Fe3+, Cd2+, Hg2+, and Cu2+ and less than 0.3% for Cr3+, Mn2+, Mg2+, In3+, Ag1+, Ni2+, Co2+, Zn2+, Ca2+, Cu1+, and Hg1+. The IC50 value achieved for lead was 2.72 +/- 0.034 microM, showing the detection range of 0.092-87.2 microM and the lowest detection limit of 0.056 +/- 0.005 microM. Recoveries from the analyte-fortified tap water and ultrapure water were in the range of 80-114% . These results indicate that the ELISA could be a convenient analytical tool for monitoring lead residues in drinking water.

Pharmacokinetics of oxaliplatin in patients with severe hepatic dysfunction

PURPOSE

Data are lacking on the pharmacokinetics of oxaliplatin in patients with severe hepatic dysfunction. The aim of this study was to determine the pharmacokinetic parameters of platinum after administration of oxaliplatin in cancer patients with severe hepatic impairment due to extended metastases into the liver.

PATIENTS AND METHODS

Two female breast cancer patients and one male colon cancer patient were treated with oxaliplatin monotherapy at 130 mg/m(2) given as a 3-h intravenous infusion. The patients exhibited bilirubin concentrations of 9.6, 22.5 and 41.1 mg/dl indicating severe hepatic dysfunction. Serial blood samples were collected immediately before treatment, and at fixed intervals up to 27 h after start of therapy. Platinum concentrations in plasma, ultrafilterable plasma, and whole blood were determined using a validated flameless atomic absorption spectrometry (FAAS) method. Pharmacokinetic data analysis was performed assuming a two-compartment model. Individual pharmacokinetic parameters were compared with a reference population with normal hepatic function.

RESULTS

The area under the curve (AUC from 0 to infinity) as well as the elimination half-life of platinum in ultrafilterable plasma were substantially increased and clearance accordingly decreased in the three patients with severe hepatic dysfunction. In plasma and whole blood, the deviations from the reference population were less pronounced. However, partial AUC from 0 up to 2 h after end of infusion reflecting better the exposure with cytotoxic platinum species was not different or only slightly altered. Moreover, no acute oxaliplatin-associated neurotoxicity was observed.

CONCLUSIONS

The comparable platinum exposure early after administration in conjunction with the lack of acute toxicity do not support a dose reduction of oxaliplatin in patients with markedly elevated bilirubin concentrations. However, a larger number of patients must be examined before valid dose recommendations can be derived.

Determination of ruthenium originating from the investigational anti-cancer drug NAMI-A in human plasma ultrafiltrate, plasma, and urine by inductively coupled plasma mass spectrometry

We present a highly sensitive, rapid method for the determination of ruthenium originating from the investigational anti-cancer drug NAMI-A in human plasma ultrafiltrate, plasma, and urine. The method is based on the quantification of ruthenium by inductively coupled plasma mass spectrometry and allows quantification of 30 ng L(-1) ruthenium in plasma ultrafiltrate and urine, and 75 ng L(-1) ruthenium in human plasma, in 150 microL of matrix. The sample pretreatment procedure is straightforward and only involves dilution with appropriate diluents. The performance of the method, in terms of accuracy and precision, fulfilled the most recent FDA guidelines for bioanalytical method validation. Validated ranges of quantification were 30.0 to 1 x 10(4) ng L(-1) for ruthenium in plasma ultrafiltrate and urine and 75.0 to 1 x 10(4) ng L(-1) for ruthenium in plasma. The applicability of the method and its superiority to atomic-absorption spectrometry were demonstrated in two patients who were treated with intravenous NAMI-A in a phase I trial. The assay is now successfully used to support pharmacokinetic studies in cancer patients treated with NAMI-A.

Continuous or repeated prolonged cisplatin infusions in children: a prospective study on ototoxicity, platinum concentrations, and standard serum parameters

BACKGROUND

To overcome the ototoxicity of cisplatin, single bolus infusions were replaced by repeated prolonged infusions of lower doses or by continuous infusions at still lower infusion rates. However, considering ototoxicity little is, in fact, known about the tolerance of repeated prolonged or continuous infusion in children.

PROCEDURE

Auditory function was monitored along with plasma concentrations of free and total platinum (Pt), and with standard serum parameters (sodium, potassium, calcium, magnesium, phosphate, chloride, and creatinine) in 24 children receiving cisplatin by continuous infusion for the treatment of neuroblastoma and osteosarcoma or by repeated 1 or 6 hr infusions for the treatment of germ cell tumors.

RESULTS

Hearing deteriorated in 10/15 osteosarcoma patients, 2/3 neuroblastoma patients, and 1/6 patients with germ cell tumors. Ototoxicity occurred after cumulative doses between 120 and 360 mg/m(2) cisplatin. In osteosarcoma patients, ototoxicity was associated with a comparatively higher mean plasma concentration of free Pt. However, Pt plasma concentrations did not discriminate between patients with or without ototoxicity. In patients experiencing ototoxicity serum creatinine increased by 45% compared to pre-treatment levels (mean). Serum creatinine increased by 26% in patients without ototoxicity (P < 0.05, Mann-Whitney Rank sum test). Despite standardized hydration, discrete but significant changes of potassium, sodium, magnesium, and phosphate were observed during and/or after cisplatin infusion, which, however, did not discriminate between patients with and without ototoxicity.

CONCLUSIONS

While continuous cisplatin infusions are less nephrotoxic than repeated prolonged infusions, we observed considerable ototoxicity in patients treated with continuous cisplatin infusions, which necessitates further evaluations on the tolerance of continuous cisplatin infusions in children.

Cisplatin nephrotoxicity is critically mediated via the human organic cation transporter 2

Cis-platin is an effective anti-neoplastic agent, but it is also highly nephrotoxic. Here, we clearly identify the human organic cation transporter 2 (hOCT2) as the critical transporter for cis-platin nephrotoxicity in isolated human proximal tubules and offer a potential mechanism for reducing nephrotoxicity in clinical practice. Interaction of cis-platin with hOCT2 in kidney or hOCT1 in liver was investigated with the fluorescent cation 4-[4-(dimethyl-amino)styril]-methylpyridinium in stably transfected HEK293 cells and for the first time in tissues physiologically expressing these transporters, human proximal tubules, and human hepatocyte couplets. Cis-platin (100 micromol/L) inhibited transport via hOCT2-HEK293 but not hOCT1-HEK293. In human proximal tubules cis-platin competed with basolateral organic cation transport, whereas it had no effect in tubules from a diabetic kidney or in hepatocytes. In hOCT2-HEK293 cells treated for 15 hours, incubation with cis-platin induced apoptosis, which was completely suppressed by contemporaneous incubation with the hOCT2 substrate cimetidine (100 micromol/L). These findings demonstrate that uptake of cis-platin is mediated by hOCT2 in renal proximal tubules, explaining its organ-specific toxicity. A combination of cis-platin with other substrates that compete for hOCT2 offers an effective option to decrease nephrotoxicity in the clinical setting.

High-performance Liquid Chromatographic Assay for Carboplatin in Ultrafiltered Plasma Combined with Hyperbaric Oxygenation

A specific, sensitive and reproducible high-performance liquid chromatographic procedure was developed for the quantitative analysis of carboplatin in human plasma. Plasma was ultrafiltered with an Amicon Centrifree system and then injected onto an analytical NH2 column. Carboplatin was monitored at 230 nm and eluted by 10 min using acetonitrile/methanol/5 mM sodium perchlorate buffer (pH 2.4) (75:15:10, v/v) as a mobile phase. The method yielded intra-day and inter-day precision and accuracy of <6% with a linearly from 0.1 to 80 microg/mL and a recovery of >98%. Plasma concentrations of intravenously administered carboplatin in three patients could be determined by this system. Slightly higher plasma concentrations of carboplatin were detected even 30 min after hyperbaric oxygenation therapy for 60 min than expected. The results suggest that this method could be applicable for measurement of carboplatin in plasma samples to evaluate carboplatin therapy together with hyperbaric oxygenation.

The Raf kinase inhibitor BAY 43-9006 reduces cellular uptake of platinum compounds and cytotoxicity in human colorectal carcinoma cell lines

Raf kinase plays a central role in oncogenic signaling and acts as a downstream effector of Ras in the extracellular signal-regulated (ERK) kinase pathway. BAY 43-9006 (BAY) is a novel signal transduction inhibitor that prevents tumor cell proliferation and angiogenesis through blockade of the Raf/MEK/ERK pathway at the level of Raf kinase and the receptor tyrosine kinases vascular endothelial growth factor receptor-2 and platelet-derived growth factor receptor-beta. The present study evaluates the effects of combining BAY and platinum derivatives on human colorectal cancer cells using different incubation protocols. Our data show that the combination of oxaliplatin or cisplatin with BAY results in marked antagonism irrespective of the used application schedule. Furthermore, BAY abrogates the cisplatin-induced G2 arrest as well as the G1 arrest induced by oxaliplatin. BAY alone arrests cancer cells in their current cell cycle phase and affects cell cycle regulative genes. Specifically, BAY reduced the protein expression of p21Cip1 as well as cyclin D1, and inhibits the expression of cdc2 (cdk1). Utilizing atom absorption spectrometry, BAY significantly reduced cellular uptake of platinum compounds and thereby the generation of DNA adducts. Taken together, co-incubation with BAY results in reduced cellular uptake of platinum compounds and consecutively reduced generation of DNA adducts, and eventually decreased cellular cytotoxicity in human colorectal cancer cells. Our results indicate that the Raf kinase inhibitor BAY 43-9006 might also directly or indirectly interact with platinum transporter proteins in vitro.

Determination of oxaliplatin in human plasma and plasma ultrafiltrate by graphite-furnace atomic-absorption spectrometry

A method for sensitive determination of the anti-cancer agent oxaliplatin in human plasma and human plasma ultrafiltrate (pUF) is presented. The method is based on the quantification of platinum by graphite-furnace atomic-absorption spectrometry, with Zeeman correction and an atomisation temperature of 2,700 degrees C. Sample pretreatment involves dilution of the samples with a solution containing 0.15 mol L(-1) NaCl and 0.20 mol L(-1) HCl in water. Validation was performed in accordance with the most recent FDA guidelines for bioanalytical method validation. All results were within requirements. The validated ranges of quantification were 0.10-400 micromol L(-1) for human pUF and 0.50-400 micromol L(-1) for plasma. The assay is now successfully used to support pharmacokinetic studies of cancer patients treated with oxaliplatin.

Long-term activation of SAPK/JNK, p38 kinase and fas-L expression by cisplatin is attenuated in human carcinoma cells that acquired drug resistance

Tumor cells chronically exposed to cisplatin (cDDP) acquire cDDP resistance that impacts tumor therapy. To elucidate the mechanism of acquired cDDP resistance (ACR), we compared HeLa cells that gained ACR upon chronic cDDP treatment with the parental strain. We show that ACR is due to a lower level of induced apoptosis. Further, upon cDDP treatment, the levels of Fas, Bax and Bid remained unchanged, whereas Bcl-2 and p-Bad were reduced at late times (120 hr) after treatment. At early times, Fas ligand (fas-L) expression was significantly enhanced in sensitive compared to resistant cells and remained upregulated up to the onset of apoptosis. Thus, activation of the Fas system is critical, which is in line with the finding that in sensitive cells, caspase-8 along with caspase-9 and -3 were activated by cDDP. cDDP provoked the activation of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) and p38 kinase dose-dependently, with significantly lower levels in ACR cells than in the sensitive parental line. cDDP induces c-Jun and AP-1 activity, as measured by a reporter gene assay, which was again attenuated in ACR cells. Time course analysis revealed that SAPK/JNK and p38 kinase activity was sustained upregulated (> 72 hr postexposure), which occurred at much higher level in sensitive than in ACR cells. Inhibition of either JNK or p38 kinase (by JNK inhibitor II and SB 203580, respectively) attenuated cDDP-induced apoptosis, supporting the role of JNK and p38 kinase in the cDDP response. Since several independently derived cDDP-resistant cell lines displayed attenuated MAPK signaling, sustained SAPK/JNK and p38 kinase activation may be a general mechanism of cDDP-induced cell death. ACR cells displayed a reduced level of DNA damage, indicating long-term stimulation of SAPK/JNK and p38 kinase is triggered by nonrepaired cDDP-induced DNA lesions.

Individualised dosing strategy for high-dose carboplatin in patients with germ cell cancer

In contrast to conventional chemotherapy, carboplatin is still dosed per unit of body surface area (BSA) in high-dose chemotherapy protocols in clinical practice. To individualise dosing, a population pharmacokinetic model for poor-risk germ cell tumour patients receiving 1500 mg m(-2) carboplatin was developed. The typical central volume of distribution (19.9 l) and typical clearance (110 ml min(-1)) corresponded approximately to the extracellular fluid space or glomerular filtration rate, respectively. The covariate analysis identified several patient-specific factors. Carboplatin clearance was significantly related to creatinine clearance and body height, explaining 73% of the interindividual variability. Thus, an equation to predict individual clearance prior to treatment was developed (CL=0.41 x creatinine clearance+1.05 x body height-124.4). The relative frequency of developing toxicity increased significantly with higher AUC values for different types of toxicity. In addition, overall nonhaematological toxicity correlated significantly with exposure of carboplatin, leading to the assessment of a target AUC. Based on the prediction of individual clearance and the definition of a target AUC associated with moderate toxicity, an individualised dosing equation is proposed. Retrospectively, the individualised dosing strategy would have led to a higher dose on average and a broader range to be administered, compared to empirical dosing per unit BSA in the high-dose setting.

Technique and results of hyperthermic (41 degrees C) isolated lung perfusion with high-doses of cisplatin for the treatment of surgically relapsing or unresectable lung sarcoma metastasis

OBJECTIVE

A technique of hyperthermic isolated lung perfusion (ILP) chemotherapy was developed.

METHODS

Since April 1999, four patients with unilateral (n=2) or bilateral (n=2) sarcoma metastasis confined to a lobe (n=2) or entire lung (n=2) entered into a pilot study of hyperthermic (41 degrees C) ILP with high doses of cisplatin (70 mg/m(2)). Eligibility included drug resistant metastasis and at least four previous surgical metastectomies. The ILP of the lung segments was carried out following metastectomy, for 20-40 min at a rate of 0.3-0.5 l/min, a mean perfusion pressure lower than the own mean pulmonary artery pressure, and an inflow temperature of 41 degrees C or higher. Before and following ILP, the isolated lung segments were flushed with normothermic saline (1 l). Flow was continuously maintained by a centrifugal pump.

RESULTS

All patients successfully completed 31.7+/-9 min perfusion time at 41.4+/-0.3 degrees C, and this time-point corresponded to the maximal platinum lung-uptake (93.8 ng/mg tissue). The total vascular isolation was confirmed by continuously low systemic cisplatin plasma levels. There was no systemic drug-related toxicity but all patients experienced transient pulmonary toxicity as non-cardiogenic edema of the treated lung segments. With a median follow-up of 12 months, three patients are alive and disease-free and one died from cerebral metastasis without autopsy evidence of local recurrence 13 months following ILP.

CONCLUSION

Hyperthermic perfusion chemotherapy can be done safely and effectively. It represents a new treatment modality and deserves further investigations for patients with advanced, drug resistant or surgically refractory, lung sarcoma metastasis. However, further studies are needed to limit the ILP-induced pulmonary toxicity.

Toxicity of high-dose carboplatin: ultrafiltered and not total plasma pharmacokinetics is of clinical relevance

Combination chemotherapy containing high-dose carboplatin is a therapeutic option for patients with poor-risk germ cell tumors. Since such treatment is relatively toxic, pharmacokinetic characteristics of total and ultrafiltered platinum, representing different species of platinum complexes formed, were investigated in 29 patients in relation to toxicity. The goodness-of-fit parameters revealed that a two-compartment model with weighting (1/C2i) resulted in the best fit. The terminal half-life of total platinum > 5 days was fourfold longer than that of ultrafiltered platinum, indicating long-term retention. At stem cell rescue, an ultrafiltered concentration of < or = 0.223 microg/ml did not impair hematological recovery. Ultrafiltered but not total platinum concentrations or AUC values were significantly correlated to an increase in creatinine concentration and different types of toxicity associated with high-dose treatment. Since the fraction unbound is time dependent and highly variable among patients, measuring ultrafiltered concentrations is highly recommended as they represent the clinically relevant platinum complexes in high-dose treatment.

Simple and rapid determination of carboplatin in plasma by high-performance liquid chromatography. Error pattern and application to clinical pharmacokinetic studies

Carboplatin is an antitumor agent widely employed in cancer chemotherapy. A specific and selective method for the determination of carboplatin in human plasma and its applications to pharmacokinetic investigations is described. One ultrafiltration step, through a Centrifree micropartition system (Amicon) at 2000 g for 10 min, is the only requirement as sample treatment. The resulting solution is injected into an Inertsil ODS-2 (5 microm, 25 cm x 4.6 mm I.D.) analytical column. The mobile phase consisted of 0.1 M potassium dihydrogenphosphate with 1 mM dipotassium edetate adjusted to a pH between 3 and 3.5. The limit of quantitation was 1 mg/l. The method showed good recovery (100.68+/-5.49%) and precision: the within-day relative standard deviation (RSD) for carboplatin (3-350 mg/l) was 2.07% and the between-day RSD for carboplatin, in the previously described range, was 1.31%. We determined the assay error pattern for proper weighting of serum level data in pharmacokinetic models. The selectivity (discrimination between the parent drug and platinum-containing species such as carboplatin metabolites), simplicity and speed of this assay for free carboplatin quantitation should facilitate pharmacokinetic investigations and therapeutic drug monitoring.

Adsorptive voltametry to determine platinum levels in plasma from testicular cancer patients treated with cisplatin

Patients cured of metastatic testicular cancer with cisplatin chemotherapy may suffer late adverse effects even after 20 years. The cause of these late adverse effects has not been elucidated yet. One cause might be prolonged tissue retention of platinum in these patients. Therefore, an extremely sensitive method for measuring platinum in plasma was used to investigate whether platinum is still detectable in plasma 10 to 20 years after cisplatin chemotherapy. High-pressure decomposition of plasma is followed by adsorptive voltametric determination of platinum, with a limit of quantification of 6 pg/g plasma. This procedure appeared suitable for the measurement of platinum in 44 former patients with platinum levels ranging from 22 to 140 pg/g plasma. This method is approximately 6000 times more sensitive than the standard flameless atomic absorption spectrophotometry (AAS) method. The platinum levels of these 44 patients were significantly elevated when compared with 20 control patients who were cured of testicular cancer but did not receive cisplatin chemotherapy (p < 0.001). There was a significant correlation between plasma platinum concentrations and follow-up time after cisplatin administration (r = -0.658, p < 0.001). This study shows that patients with testicular cancer who were treated with cisplatin can retain platinum in their body for at least 20 years. More data are needed to investigate whether there is a relation between the prolonged retention of platinum and long-term toxicity.