Pierre Canal

Cellular determinants of oxaliplatin sensitivity in colon cancer cell lines

Oxaliplatin (L-OHP) is a new platinum analogue that has shown antitumour activity against colon cancer both in vitro and in vivo and is now used in the chemotherapeutic treatment of metastatic colon and rectal cancer. L-OHP like cisplatin (CDDP), is detoxified by glutathione (GSH)-related enzymes and forms platinum (Pt)-DNA adducts lesions that are repaired by the nucleotide excision repair system (NER). We investigated the cytotoxicity and the pharmacology of L-OHP and CDDP on a panel of six colon cell lines in vitro. We showed that GSH and glutathione S-transferase (GST) activity were not correlated to oxaliplatin cytotoxicity. Pt-DNA adducts formation and repair were correlated with CDDP, but not with L-OHP cytotoxicity. The determination of ERCC1 and XPA expression, two enzymes of the NER pathway, by reverse transcriptase-polymerase chain reaction (RT-PCR), demonstrated that ERCC1 expression was predictive of L-OHP sensitivity (r(2)=0.67, P=0.02) and XPA level after oxaliplatin exposure was also correlated to L-OHP IC(50) (r(2)=0.5; P=0.04). The knowledge of such correlations could help predict the sensitivity of patients with colon cancer to L-OHP.

Co-variables influencing 5-fluorouracil clearance during continuous venous infusion. A NONMEM analysis

The objective of this study was to attempt to identify patient co-variables which could influence interpatient variability in 5-fluorouracil (5-FU) clearance during a 5-day continuous venous infusion (CVI, cisplatin 100 mg/m2 day 1 then 5-FU 1 g/m2/day days 2-6). The analysis was performed using a NONMEM program according to a linear one-compartment model. A total of 186 cycles (2 samples per day, 8 a.m. and 5 p.m.) were analysed from 104 patients with various cancers (the majority of head and neck and oesophagus). The study co-variables were age, sex, body surface area, hepatic metastases, peripheral mononuclear cell dihydropyrimidine dehydrogenase activity (PMNC-DPD), liver enzymes, clock-time (8 a.m. versus 5 p.m.), elapsed time during CVI. The data showed that 5-FU clearance was significantly reduced by increased age, low PMNC-DPD, high serum alkaline phosphatase and elapsed time during infusion. These data may be useful for improving knowledge of predictive factors which can influence 5-FU exposure and thus predispose to toxic manifestations.

Comparison of the pharmacokinetics and efficacy of irinotecan after administration by the intravenous versus intraperitoneal route in mice

Abstract Irinotecan (CPT-11) is a new drug active in colorectal cancer. A comparison was made of the efficacy and pharmacokinetics of CPT-11 after i.p. versus i.v. administration to mice. We found that i.p. administration of CPT-11 to mice bearing C26 colon cancer was more efficient and less toxic than i.v. administration; a 100-mg i.p. dose induced an increase in life span equivalent to that produced by a 300-mg i.v. dose, and toxic deaths appeared after doses of 400 mg/kg given i.v. and 800 mg/kg given i.p. Pharmacokinetic parameters of CPT-11 and SN-38 were compared after i.v. or i.p. administration in mice bearing P388 leukemia ascites. Peritoneal CPT-11 and SN-38 AUC values were higher after i.p. administration than after i.v. injection. Plasmatic AUC values remained equivalent. Moreover, peritoneal CPT-11 clearance was 10-fold lower after i.p. versus i.v. administration. If the survival and pharmacologic advantage of i.p. CPT-11 in the murine model considered can be translated to a safe and practical mode of therapy in patients and if local toxicity does not prove to be a major adverse effect, then a potentially useful agent could be added to the drugs known to be active when given by the i.p. route for adjuvant therapy in colon cancer.

A limited sampling strategy for determining carboplatin AUC and monitoring drug dosage

There are several convincing reports showing relationships between the area under the curve of ultrafilterable concentration versus time (AUC) and pharmacodynamics of carboplatin. It is advisable, in treated patients, to check the AUC that is effectively delivered as compared with the prescribed AUC. To this end, limited sampling strategy seems to be an adequate approach since it limits the constraints of repeated blood sampling for both patients and nursing staff. A flexible limited sampling method for assessing ultrafilterable carboplatin AUC was developed. This method was based on a Bayesian estimation of carboplatin clearance using the NON linear Mixed Effect Model (NONMEN) program and a large pharmacokinetic and covariates database (103 patients). The optimal sampling design was a two-sample schedule (1 and 4 h after the end of infusion). During a prospective evaluation, it allowed an adequate estimation of carboplatin clearance with a non-significant bias (-4.5%) and a good precision (9%). In a second stage, this method was clinically applied to monitor carboplatin AUC in a group of 5 patients with metastatic germ cell tumours treated with intensified high dose carboplatin-based chemotherapy for 4 days. Dosage adjustments were performed according to daily controls of their AUC in order to obtain a total AUC of 20 mg/ml x min. By using this strategy all patients effectively received a total AUC very close to this targeted AUC, thus proving the clinical usefulness of this limited sampling method.

Population pharmacokinetics of topotecan: intraindividual variability in total drug.

Abstract The inter- and intraindividual variabilities in topotecan clearance (CL) were explored using a population pharmacokinetic approach. Total (lactone + hydroxy acid) topotecan plasma concentrations were obtained in 31 women with metastatic epithelial ovarian cancer treated by the 30-min intravenous infusion on 5 subsequent days. The data corresponding to three occasions (days 1 and 5 of cycle 1, and day 1 of cycle 2), were analyzed using the nonlinear mixed effect model program. A large interindividual variability was observed, with CL varying from 9.1 to 42.5 l per hour (mean 21.0). Topotecan CL was related to serum creatinine level, and age. A close relationship was also observed between topotecan CL and creatinine clearance. Intraindividual variability both within cycle 1 and between the two first cycles was limited, with a mean variation of −2 ± 17%, and +5 ± 20%, respectively. A limited sampling strategy using Bayesian estimation based on two samples (5 min before the end of the 30-min infusion, and 4 h after the end of infusion) was developed. The results of this study combine relationships between topotecan pharmacokinetic parameters and patient covariates that may be useful for a priori dose adjustment, and convenient sampling procedure that can be used for further studies and drug monitoring.

Serum apolipoproteins A-I, A-II and B in hepatic metastases. Comparison with other liver diseases: hepatomas and cirrhosis

Serum concentrations of lipids and apolipoprotein A-I, A-II and B were determined in patients with hepatic metastases of colorectal cancer, with primary liver cancer and with cirrhosis. In all three liver diseases, the HDL fraction and apolipoproteins A-I and A-II showed significantly low values, while apolipoprotein B was only increased in hepatic metastases. The decrease of apolipoprotein A-II levels was more prominent in cirrhosis, thereby enhancing the A-I/A-II ratio. This ratio is decreased in metastasis and normal in hepatomas. In patients with hepatic metastases a correlation was observed between alkaline phosphatase and apolipoprotein A-II (p less than 0.05), and between gamma-glutamyltransferase and the A-I/A-II ratio (p less than 0.05). The present work suggests that determination of apolipoproteins and lipids of the HDL fraction offers a new approach to the study of liver diseases.

A limited-sampling strategy for estimation of etoposide pharmacokinetics in cancer patients.

Abstract Etoposide (VP16), a widely used anticancer drug, is a topoisomerase II inhibitor. A number of studies have highlighted a correlation between hematologic toxicity and pharmacokinetic or physiological parameters. Other studies have also suggested that the anti-tumor response could be related to the plasma etoposide concentration. Therefore, it would seem of interest to individualize VP16 dose regimens on the basis of pharmacokinetic parameters. The aim of this study was to develop and validate a limited-sampling strategy allowing VP16 pharmacokinetic evaluation with minimal disturbance to the patient. A total of 34 patients (54 kinetics) received VP16 at various dose regimens, with doses ranging between 30 and 200 mg and infusion times varying between 0.5 and 2 h. The statistical characteristics of the pharmacokinetic parameters were assessed from the first courses of treatment performed in 23/34 patients; then the following three-sample protocol was designed: the end of the infusion and 5 and 24 h after the start of the infusion. For validation of the model the main pharmacokinetic parameters (clearance, half-lives, volume of distribution) were estimated in the 11 remaining patients by maximum-likelihood estimation (ML) and by Bayesian estimation (BE) using the three sampling times designed. Statistical comparison showed a good concordance between ML and BE estimates (the bias for clearance was –1.72%). The limited-sampling strategy presented herein can thus be used for accurate estimation of VP16 pharmacokinetic parameters.

Contribution of apoptosis in the cytotoxicity of the oxaliplatin–irinotecan combination in the HT29 human colon adenocarcinoma cell line

Interactions between the topoisomerase I inhibitor irinotecan (CPT-11) and the platinum derivative oxaliplatin (L-OHP) were investigated in HT29 colon cancer cell line. Synergism was observed when cells were simultaneously exposed to drugs or when cells were first exposed to CPT-11. Flow cytometric studies showed a G(2)/M accumulation when cells were exposed to the simultaneous and CPT-11-->L-OHP combinations whereas a persistent S phase delay was observed when cells were first exposed to L-OHP. We characterised the cytotoxic effect by assessing the induction of apoptosis. Irinotecan induced substantial DEVDase activity and poly(ADP-ribose) polymerase cleavage while this activity was moderate and delayed after exposure to L-OHP. Combination experiments showed a sequence-dependent onset of apoptosis, the CPT-11-->L-OHP schedule being the earliest and the most effective; on the other hand the apoptotic signaling generated by CPT-11 was partly inhibited in the simultaneous combination and in the L-OHP-->CPT-11 sequence. Cell death studies using a dual staining technique showed a shift from apoptosis to necrosis when combining these drugs at high concentrations. Synergistic interactions observed using CPT-11 before L-OHP may be linked to an early apoptotic signaling while the L-OHP-induced S phase block could account for the observed additive effect in the reverse sequence. An additional phenomenon might work towards synergism for the simultaneous combination.

Modulation of cisplatin cytotoxicity by human recombinant interferon-γ in human ovarian cancer cell lines

Cytotoxic interactions between recombinant human interferon-gamma (IFN gamma) and cisplatin have been studied in six ovarian cell lines (IGROV1, NIHOVCAR3, SKOV3, OVCCR1, 2008 and its cisplatin resident variant 2008/C13*). Studies were performed using a cell survival assay. Results were assessed using median effect analysis. Synergy between these two drugs was observed in cell lines sensitive to IFN gamma, whatever their relative sensitivity or resistance to cisplatin, suggesting that IFN gamma enhances the cytotoxic activity of cisplatin. This interaction is not due to an increase in platinum accumulation in cells. This combination of drugs should be evaluated against human ovarian cancer xenografts in nude mice before its use in clinical practice.

Chronopharmacokinetics of doxorubicin in patients with breast cancer

SummaryThe chronopharmacokinetics of doxorubicin (DOX) has been studied in 18 patients suffering from breast cancer. They received combined chemotherapy, including DOX (50 mg/m2 as an iv bolus), given at two different times (09.00 h or 21.00 h). The two randomized courses of the protocol were given to each patient at a four week interval.The total body clearance (CL) of DOX was significantly decreased when the drug was administered at 21.00 h, resulting in a longer elimination half-life and an increase in AUC. The renal clearance of DOX did not differ at the different times of administration, and it appears that the decrease in CL was related to a change in hepatic blood flow. The volume of distribution of the drug was not changed.