Trastuzumab induced in vivo tissue remodelling associated in vitro with inhibition of the active forms of AKT and PTEN and RhoB induction in an ovarian carcinoma model.

BACKGROUND: The incidence of ovarian cancer has been increasing worldwide and it is currently the leading cause of death from gynaecological malignancy. Unlike breast cancer, the prognostic role of the human epidermal growth factor receptor-2 (HER-2) in ovarian carcinoma remains controversial. METHODS: The aim of this preclinical study was to further characterise the biological, molecular and cellular effects of trastuzumab (Herceptin) using NIH-OVCAR-3 and derived cell lines both in vitro and in vivo. RESULTS: In vitro assessments have shown that trastuzumab treatment inhibited total and phosphorylated HER-2. This was associated with inhibition of the phosphorylated form of phosphatase and tensin homologue (PTEN), mitogen-activated protein kinase and AKT, and the total level of p27(kip). Inhibition of PTEN is associated with phosphorylated MEK1/2 upregulation, suggesting a specific inhibition of the protein phosphatase function of PTEN. Moreover, trastuzumab induced the upregulation of RhoB. These molecular modifications promote inhibition of cell migration and potentially restoration of tumour cell contact inhibition. RhoB induction in NIH-OVCAR-3 control cell lines mimics the molecular and cellular trastuzumab long-time exposition effects. RhoB inhibition in NIH-OVCAR-3 long-time exposed to trastuzumab cell line reverses the cellular and molecular effects observed in this model. In vivo examinations have shown that these changes are also associated with the restoration of structural, morphological and normal functions of the peritoneum of an ovarian carcinoma mouse model. CONCLUSION: These results provide an indication of the mechanisms underlying the anti-tumour activity of trastuzumab that strongly implicate RhoB in an ovarian carcinoma model that does not show HER-2 amplification or overexpression. These findings highlight that trastuzumab effects involve a possible cross-talk between RhoB and PTEN in the early stages of tumour re-growth in a model of micrometastatic ovarian cancer.

Factores relacionados con la vía de parto tras cesárea anterior / Factors related to delivery route after a previous cesarean section

Con el objetivo de evaluar la tasa de parto vaginal tras una cesárea anterior en nuestro medio se hizo un estudio retrospectivo mediante revisión de historias clínicas de las 258 gestantes con cesárea anterior que parieron en nuestro hospital entre 2005 y 2007. Se excluyó a las mujeres que tenían más de una cesárea, incisión uterina clásica o cualquier contraindicación absoluta para parto vaginal. El 59,3% tuvo parto vaginal; el 55% inició trabajo de parto espontáneo, en el 21,7% se indujo el parto y al 23,3% se le programó cesárea. De las variables estudiadas, las mayores tasas de parto vaginal se producen cuando el trabajo de parto se inició espontáneamente (78,87%), cuando el test de Bishop fue superior o igual a 6 (88,51%) y cuando existía el antecedente de parto vaginal previo (66,7%) o posterior (84,25%). En cuanto a la indicación de la cesárea anterior, las peores tasas de parto vaginal (42,2%) se obtienen cuando la indicación previa fue distocia (no progresión/desproporción). No se produjo ninguna rotura uterina en nuestra serie y no hubo un incremento de la morbimortalidad materna ni fetal, por lo que podemos concluir que el parto vaginal es posible en casi el 60% de las gestantes con cesárea anterior sin un incremento de la morbimortalidad maternofetal (AU)

The aimof this study was to evaluate the rate of vaginal birth after a previous cesarean in our population. A retrospective study was performed throug hare view of the clinical histories of the 258 women with a previous cesarean section that delivered in our hospital between 2005 and 2007. Women with more than one prior cesarean section, classical uterine incision or any absolute contraindication for vaginal delivery were excluded.Delivery was through the vaginal route in 59.3%. Fifty-five percent of the women began spontaneous delivery, 21.7%were induced and cesarean section was scheduled in 23.3%. Ofthe variables studied, the high estrates of vaginal birth were produced with spontaneous labor, when Bishop’s scorewas X6 (88.51%) and when there was a history of vaginal birth before a cesarean section (66.7%)or after a cesarean section (84.25%). The low estrates of vaginal delivery (42.2%)were obtained when the previous indication for cesarean sectionwas dystocia (no progression/disproportion). There were no case sof uterine rupture in ourstudy and maternal and fetal complications did not increase. In conclusion, vaginal birthisfeasible in almost 60%of women with a prior cesarean section and does not in crease fetaland maternal complications (AU)

Cetuximab potentiates oxaliplatin cytotoxic effect through a defect in NER and DNA replication initiation.

Preclinical studies have demonstrated that the chemotherapeutic action of oxaliplatin, a third generation platinum derivative, is improved when combined with cetuximab, a monoclonal antibody inhibitor of epidermal growth factor receptors. To explore the mechanism of this synergistic benefit, we used HCT-8 and HCT-116, two human colon cancer cell lines, respectively, responsive and non-responsive to the oxaliplatin/cetuximab combination. We examined the effect of drug exposure on glutathione-S-transferase-mediated oxaliplatin detoxification, DNA-platinum adducts formation, cell cycle distribution, apoptosis, and the expression of multiple targets involved in DNA replication, recombination, and repair. The major changes we found in HCT-8 were a stimulation of oxaliplatin-DNA adduct formation associated with reduced expression of the key enzyme (excision repair cross complementation group1: ERCC1) in the key repair process of oxaliplatin-DNA platinum adduct, the nucleotide excision repair (NER), both at the mRNA and protein levels. We also observed a reduced expression of factors involved in DNA replication initiation, which correlates with an enrichment of cells in the G1 phase of the cell cycle as well as an acceleration of apoptosis. None of these changes occurred in the non-responsive HCT-116 cell that we used as a negative control. These findings support the fact that cetuximab potentiates the oxaliplatin-mediated cytotoxic effect as the result of inhibition of NER and also DNA replication initiation.

Cancellous bone homograft storage with aluminium-polyethylene bags.

In order to transport and cryopreserve human tissues, it is essential to have an easy-to-use recipient where tissues can be kept in sterile conditions. Here we show the results obtained by using Macopharma's tissue freezing bags, an aluminium-polyethylene multilayer bag, in our tissue bank of the Centro Comunitario de Sangre y Tejidos de Asturias. Five hundred and twenty-seven cancellous bone homografts were obtained from hospitals located 120 km around our Bank. The homografts were submitted to bacteriological controls and sent to our bank in these bags. They were stored at -70 degrees C and sent in dry ice to about 50 hospitals, where the tissue was bacteriologically controlled and grafted. Furthermore, the behaviour of these bags at -140 degrees C (vapour nitrogen) or -196 degrees C (liquid nitrogen) was tested. Our results indicate that Macopharma aluminium-polyethylene bags are suitable for the transporting and cryopreserving of cancellous bone homografts. These bags could also be used for keeping tissues in nitrogen containers.

Selective inhibition of HER2 inhibits AKT signal transduction and prolongs disease-free survival in a micrometastasis model of ovarian carcinoma.

Although first-line chemotherapy induces complete clinical remission in many cases of epithelial ovarian cancer, relapse usually occurs 18-28 months from diagnosis owing to micrometastases. The present study aimed to evaluate the effect of trastuzumab on disease-free and overall survival in a specially designed murine model of ovarian cancer (OVCAR-3), which mimicked the natural history of human micrometastatic disease. Trastuzumab can cure the mice if started soon after induction chemotherapy. It can modestly inhibit the proliferation through mitogen-activated protein kinase signal transduction and clearly inhibit AKT phosphorylation, which is involved in survival pathway. As OVCAR-3 cell lines show no HER2 amplification or overexpression, these results warrant further studies to assess the efficacy of trastuzumab in the early stage of relapse in cancer models other than those overexpressing HER2.

A phase I clinical and pharmacokinetic study of capecitabine (Xeloda) and irinotecan combination therapy (XELIRI) in patients with metastatic gastrointestinal tumours.

Capecitabine is a highly active oral fluoropyrimidine that is an attractive alternative to 5-fluorouracil in colorectal cancer treatment. The current study, undertaken in 27 patients with gastrointestinal tumours, aimed to assess the toxicity and potential for significant pharmacokinetic interactions of a combination regimen incorporating capecitabine with 3-weekly irinotecan (XELIRI). Irinotecan (200 and 250 mg m(-2)) was administered as a 90-min infusion on day 1 in combination with escalating capecitabine doses (700-1250 mg m(-2) twice daily) administered on days 2-15 of a 3-week treatment cycle. Pharmacokinetics were characterised on days 1 and 2 of the first two cycles. A total of 103 treatment cycles were administered. The principal dose-limiting toxicities were diarrhoea and neutropenia. Capecitabine 1150 mg m(-2) twice daily with irinotecan 250 mg m(-2) was identified as the maximum-tolerated dose and capecitabine 1000 mg m(-2) with irinotecan 250 mg m(-2) was identified as the recommended dose for further study. Analyses confirmed that there were no significant pharmacokinetic interactions between the two agents. The combination was clinically active, with complete and partial responses achieved in heavily pretreated patients. This study indicates that XELIRI is a potentially feasible and clinically active regimen in patients with advanced gastrointestinal cancer.

Phase I and pharmacological study of an oxaliplatin and carboplatin combination in advanced malignancies.

BACKGROUND: Phase I and pharmacokinetic study to determine the maximal tolerated dose and the recommended dose, as well as the optimal sequence of a carboplatin/oxaliplatin combination delivered every 3 weeks. PATIENTS AND METHODS: Patients received either carboplatin [area under the curve (AUC)-based individually calculated dose (starting dose AUC 4 mg.min/ml), 1 h intravenous (i.v.) infusion] followed by oxaliplatin (110 mg/m(2), 2 h i.v. infusion), every 3 weeks, or the reverse sequence. RESULTS: Sixteen patients were included and only one dose level was assessed. In group A, 10 patients received 23 cycles of carboplatin followed by oxaliplatin. In group B, 6 patients received 20 cycles with the reverse sequence. Delayed recovery from hematological toxicities was treatment-limiting, with mainly moderate thrombocytopenia and neutropenia as dose-limiting toxicities for group A (5 of 10 patients for each) and thrombocytopenia for group B (3 of 6 patients). No febrile neutropenia or grade 3/4 non-hematological toxicity occurred. Pharmacokinetic analysis showed similar mean total platinum AUCs for the two groups: 37.2 +/- 13.7 and 33.6 +/- 9.9 mg.h/l, respectively. One complete response and two partial responses (World Health Organization-International Union Against Cancer criteria, response rate 18.8%) were seen in ovarian, Fallopian and neuroendocrine carcinomas, respectively. CONCLUSIONS: This platinum combination appears feasible and active at the dose of AUC 4 mg.min/ml for carboplatin (Chatelut formula) and oxaliplatin 110 mg/m(2); however, it does not allow a significant increase in platinum dose-intensity delivery.

Pharmacokinetics of low-dose carboplatin and applicability of a method of calculation for estimating individual drug clearance.

BACKGROUND: Carboplatin is the only cancer drug for which conventional doses are individually adjusted according to estimated clearance and target area under the curve (AUC). The aim of this prospective study was (i) to evaluate intra- and interpatient variability of ultrafilterable (UF) carboplatin AUC(0-)(infinity) and (ii) to test whether the prediction of carboplatin clearance according to the Chatelut formula established for conventional carboplatin doses was accurate for low carboplatin doses. MATERIALS AND METHODS: Thirty-one head and neck cancer patients (29 men, two women, mean age 55.9 years) received concomitant radiotherapy (Rgamma 2 Gy/day) and chemotherapy (carboplatin 50 mg/m(2)/day i.v.) for 7 weeks: Rgamma was administered 5 days/week (days 1-5) and carboplatin 2 days/week (days 1 and 4). Pharmacokinetics was performed once per week. A limited sample strategy based on Bayesian analysis was first validated and blood was subsequently taken 1 and 4 h after the end of carboplatin administration. RESULTS: A total of 143 cycles was analyzed. Ultrafilterable carboplatin AUC(0-)(infinity) ranged from 0.360 to 4.200 mg.min/ml (mean 0.830, median 0.670). As a corollary, UF carboplatin clearance ranged from 19.1 to 244.7 ml/min. Ultrafilterable carboplatin concentrations were very stable over time: AUC(0-)(infinity) variability due to treatment duration contributed to <1% of the total variance, while interpatient variability contributed to 68.6%. Accordingly, intrasubject effect was not significant (P = 0.38) whereas intersubject effect was highly significant (P <0.001). These results suggest that optimal dosage for targeting a given AUC may vary within a 13-fold range between patients. The Chatelut formula, based on creatininemia, body weight, age and sex, over estimates carboplatin clearance by 40% on average (bias 95% CI 29.6% to 51.1%). No significant relationship was observed between either bone marrow toxicity or creatinine clearance decrease and carboplatin pharmacokinetics. CONCLUSIONS: The Chatelut carboplatin clearance model established for conventional carboplatin dosages (>100 mg/m(2)) is not applicable for targeting low AUC (<1 mg x min/ml).

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.

Study of implantable calcium phosphate systems for the slow release of methotrexate.

The authors prepared and studied systems implantable in bone, for the slow release of an antineoplasic agent, methotrexate (MTX). The systems were made by compaction of a powdered mixture of an apatitic deficient calcium phosphate, dextran and various amounts of MTX. Used as a matrix, this calcium phosphate has outstanding adsorption and compaction properties. It is an osteoconductor and biodegradable. The in vitro study carried out on these systems showed that the release of MTX with time is slow and prolonged due to the phenomena of adsorption/desorption of MTX onto deficient apatite. The composition of the implants changed with time towards that of stoichiometric apatite. The in vivo pilot study was performed by implantation in the external femoral condyle of rabbits. A pharmacokinetic study revealed that the circulating concentration of MTX in the blood was always below toxic levels. Twenty percent of the initial MTX remained in the implants after 7 days. A study of the biocompatibility and bioreactivity showed no local necrosis at any time, while implants degraded and new bone formed simultaneously. These implantable systems seem appear suitable for use immediately.

Impact of the biochemical assay for serum creatinine measurement on the individual carboplatin dosing: a prospective study.

We previously developed a formula to estimate the individual carboplatin clearance (CL) based on serum creatinine (Scr) determined by an enzymatic assay using creatinine amidohydrolase. An analytical comparison had shown systematic differences between this method and the commonly used Jaffé method (with Jaffé Scr (in microM)=1.08 x enzymatic Scr+1.6, as regression equation). We performed a pharmacokinetic prospective clinical study using the Jaffé assay to evaluate the impact of the method used for Scr measurement on the prediction of the carboplatin CL. In forty patients, carboplatin dosing was performed according to the Chatelut formula where the serum creatinine level was corrected according to the above equation. The population pharmacokinetics of carboplatin were analysed using the NONMEM program to determine the individual carboplatin CL from a limited sampling strategy. Thanks to the correction of the Jaffé Scr, no significant difference was observed between the administered and the optimal dose. In contrast, if no correction of the Scr was done, the patients would have been significantly under-dosed. Moreover, a covariate analysis using NONMEM gave a very consistent result showing that Scr should be decreased by 11.6% when the Jaffé value is used within the Chatelut equation. This study confirmed that differences in the Scr assay has consequences with regard to carboplatin dosing. The correction we propose for Scr obtained by the Jaffé method may help to standardise clinical practice.

Combination of oxaliplatin and irinotecan on human colon cancer cell lines: activity in vitro and in vivo.

The in vitro and in vivo combination of oxaliplatin and irinotecan was investigated in a panel of four human colon cancer cell lines and their counterpart xenografts. In vitro and in vivo experiments demonstrated a synergistic or additive interaction in three cell lines (HCT-116, HCT-8 and HT-29) and an antagonism in SW-620 cells. Since there were clearly opposite interactions depending on the cell line, we further investigated cellular determinants possibly involved in the interaction between the two drugs in HCT-8 and SW-620 cells. Irinotecan slowed down the early platinum-DNA adducts repair (1 h after oxaliplatin exposure) in the presence of irinotecan only in HCT-8 cells (p=0.03, n=3). Moreover, a decrease of the expression of two proteins of the nucleotide excision repair (NER) system, ERCC1 and XPA, was observed. None of these effects was seen in SW-620 cells. Irinotecan induced apoptosis with an increase of poly(ADP-ribose) polymerase (PARP) cleavage in SW-620 cells (60 versus 7% basal level). Pretreatment of these cells with oxaliplatin abolished the increase in PARP cleavage induced by irinotecan (29%). In HCT-8 cells, a very little PARP cleavage was observed whatever the drug treatment. The persistence of platinum-DNA adducts in the presence of irinotecan could be due to a direct impact of irinotecan on NER gene expression or to an indirect effect on topoisomerase I activity. Complementary studies are required to determine if the cellular parameters identified in this study could be translated at the clinical level to predict clinical response after combined treatment with oxaliplatin and irinotecan in humans.

Schedule-dependent activity of topotecan in OVCAR-3 ovarian carcinoma xenograft: pharmacokinetic and pharmacodynamic evaluation.

Topotecan is a topoisomerase (Topo) I inhibitor used in ovarian carcinoma chemotherapy. Topo I inhibitors are thought to be more cytotoxic using protracted schedules of administration. We tested this hypothesis on a preclinical model: human ovarian carcinoma OVCAR-3 implanted i.p. Nude mice were treated i.p. with a total dose of topotecan of 12.5 mg/kg delivered in 1, 5, 10, 20, 40, or 80 daily injections. The toxicity was maximal when the total dose was delivered within 5 and 10 days of treatment. However, the efficacy was the greatest (all of the mice cured) in the 20-day schedule using 0.625 mg/kg/day, hence, making this latter schedule the most efficient without any major toxicity. A pharmacokinetic study was conducted to identify parameters related to the efficacy and toxicity of topotecan in our model. The use of a population pharmacokinetic approach allowed us to define a therapeutic window: maintaining plasma concentrations above 0.2 microM for >10 h was necessary for an optimal antitumor effect and avoiding plasma concentrations >0.7 microM allowed a manageable toxicity. Finally, Topo I activity was monitored in ascites from animals treated with different topotecan administration schedules. The optimal schedule defined above allowed for sustained inhibition of Topo I activity associated with a greater antitumor activity. These in vivo data constitute a rationale for clinical studies testing this type of administration.

Comparison of nonlinear mixed-effect and non-parametric expectation maximisation modelling for Bayesian estimation of carboplatin clearance in children.

OBJECTIVE: The pharmacodynamic-pharmacokinetic relationships for carboplatin involve the area under the curve of ultrafiltrable plasma concentrations versus time (AUC). The objective of the study was to compare two specific population pharmacokinetic methodologies, nonlinear mixed-effect model (NONMEM) and non-parametric expectation maximisation (NPEM), when they are applied to sparse carboplatin pharmacokinetic data in order to obtain an individual value for carboplatin clearance by Bayesian estimation. METHODS: The data from 117 patients (from 1 month to 18 years old) were available. For 20 patients randomly selected, the carboplatin clearance obtained by Bayesian estimation using two plasma ultrafiltrable concentrations was compared with that obtained by individual analysis using all concentrations. RESULTS: Both methodologies were unbiased with mean relative percentage errors (95%CI) of -1.9% ( 7.8; +4.1%) and +6.4% (-2.1; +14.9%) for NONMEM and NPEM, respectively. A comparison of precision between the two methods showed that they were not significantly different (12.5% for NONMEM, and 18.9% for NPEM), but the percentage error ranged between -21% and + 19% for NONMEM, and -35% and + 42% for NPEM. A NONMEM analysis was also performed with all the data available (117 children) in order to update an equation describing the relationship between carboplatin clearance and the patients' covariates. The best relationship corresponded to the equation: clearance (ml/min) = [4.47 x body weight x (1 -0.22 x Np)/(l + 0.0156 x Scr)] +6.4, with body weight in kilograms and where Scr is serum creatinine in micromoles per litre and Np= 1 or 0 for unilateral nephrectomy or not, respectively. CONCLUSION: These methodologies may be useful for dose individualisation and drug monitoring of carboplatin in paediatric patients. Since the mode of administration of carboplatin in paediatric practice in some protocols is daily 1-h i.v. infusion repeated up to five times, dose individualisation may be performed from the clearance observed after the first administration, given an overall target AUC.

Population pharmacokinetics of topotecan: intraindividual variability in total drug.

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 42.51 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.

[Pharmacokinetics and individual dose adjustment of carboplatin]. / Pharmacocinétique et adaptation individuelle de posologie du carboplatine.

Carboplatin differs from cisplatin by its pharmacokinetics and toxicity profile. Carboplatin is mainly eliminated by the kidneys and its dose-limiting toxicity is the bone marrow suppression. Myelosuppression of carboplatin is more closely correlated with the area under the curve (AUC) of ultrafiltrable plasma concentration versus time to which a patient is exposed, than it is with the administered dose. Similar relationships have been shown between AUC and antitumour effect, although they are in a smaller number and less close. Several methods of dosage individualisation a priori (before carboplatin administration) have been proposed. Since carboplatin is often prescribed to patients with altered renal functions, this dose optimisation is particularly justified. Dose individualisation is based on both equations allowing to predict the patient carboplatin clearance and the choice of target AUC. The different equations proposed are based on direct measurement of the renal filtration glomerular rate or on patient demographic and biological characteristics such as weight and serum creatinine. The respective advantages and limits of these equations are now well known. However, the values of optimal AUC that depend on cytotoxic drugs combined to carboplatin and the patient hematopoietic status, are not precisely determined for each protocol of chemotherapy. When carboplatin is given by reiterated administrations within each course, it is possible to adjust the last doses according to a limited number of blood samples following the first infusion and a Bayesian analysis of the observed plasma concentrations. These methodologies are more complex, but they may be useful for the intensification protocols. Carboplatin is still the only cytotoxic drug for which dose is individualised not according to the body surface area but according to pharmacokinetic parameters.

Dose and time dependencies of 5-fluorouracil pharmacokinetics.

OBJECTIVES: The purpose of this study was to examine the interpatient and intrapatient variability of the Michaelis-Menten plasma parameters of 5-fluorouracil administered according to a schedule combining a bolus of 400 mg/m2 followed by 22-hour infusion of 600 mg/m2 for 2 consecutive days. PATIENTS: A pharmacokinetic population approach was used to analyze the data from 21 patients with colorectal cancer. RESULTS: The 5-fluorouracil plasma concentrations versus time were best described by a two-compartment model with nonlinear elimination from the central compartment. The relationships between the pharmacokinetic parameters and patient characteristics were tested. On day 1 the mean values (with interindividual variability as expressed by the coefficient of variation) were 1390 mg x h(-1) (20%), and 5.57 mg x L(-1) (22%) for the maximum rate of elimination, and the half-saturating plasma concentration. The maximum rate of elimination was positively correlated to the body surface area and the percentage of liver involvement by metastatic disease determined by tomodensitometric examination. The model was successfully tested with independent data sets corresponding to other schedules. The analysis of this intrapatient variability showed that the half-saturating plasma concentration increased from day 1 to day 2, especially in the patients with low lymphocyte cell dihydropyrimidine dehydrogenase activity. CONCLUSION: The pharmacokinetic parameters obtained in this study would be useful to predict the 5-fluorouracil plasma concentrations following other schedules of administration of 5-fluorouracil and to study the possible pharmacokinetic interactions between 5-fluorouracil and other drugs.

Characterization of CPT-11 converting carboxylesterase activity in colon tumor and normal tissues: comparison with p-nitro-phenylacetate converting carboxylesterase activity.

Irinotecan (CPT-11) is a topoisomerase I inhibitor commonly used in the treatment of colorectal tumors. It is a prodrug, converted to an active metabolite, SN-38, by carboxylesterases (CEs). CEs are ubiquitary enzymes that react with numerous substrates. A specific CPT-11 converting enzyme was isolated from rat serum, with different kinetic properties than other CEs. We determined kinetic properties of specific CPT-11 CE activity (CPT-CE) in human normal liver and colon tumors. Km were very similar (3.4 microM in liver and 3.8 microM in colon tumors), but Vmax was higher in liver (2.7 pmol/min/mg protein) than in colon tumor (1.7 pmol/min/mg protein). CPT-CE and total CE (using p-nitro-phenylacetate as substrate) were weakly correlated in colon tumors. The large interpatient variability observed in liver CPT-CE activity could play a potential role in the pharmacokinetic variability observed with irinotecan.

Dihydropyrimidine dehydrogenase activity in normal, inflammatory and tumour tissues of colon and liver in humans.

BACKGROUND/PURPOSE: Dihydropyridmidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (5FU). Although this catabolism is likely to occur in the liver in humans, there may be a local inactivation in tumours, modifying the efficacy of 5FU. The aim of this study was to examine the DPD activity in normal, inflammatory and malignant tissues from both the colon and the liver to assess the modifications of DPD activity in the process of tumourigenesis. METHODS: DPD activity was evaluated in 107 patients, corresponding to 194 samples (70 colorectal tumour and normal colon, nine metastases secondary to a colon cancer, ten inflammatory colon, 20 samples of normal liver, seven from primary liver cancer, and eight from inflammatory liver). DPD activity was determined using an enzymatic reaction followed by analysis of 5FU and its catabolite dihydro-5FU by high-performance liquid chromatograph. Results were expressed as pmol of 5FU catabolized/min x mg protein. RESULTS: DPD was highly variable in tumour and normal tissues, both from colon and liver. In colon, the correlation between DPD activity in tumour and normal mucosa was weak, even if it was statistically significant due to the higher number of samples. In inflammatory colon tissue (ulcerative colitis or Crohn's disease), DPD activity was significantly higher than in normal tissue (P = 0.006). In liver metastases from colon cancer, DPD activity was not significantly different from that observed in primary colon tumour (P = 0.32). In liver, DPD activity was significantly lower in primary liver tumour than in uninvolved liver specimens (P = 0.001). In inflammatory liver tissue (hepatitis), DPD activity ranged between normal and tumour tissues, and did not differ significantly either from normal tissue or primary liver cancer. CONCLUSIONS: DPD activity was modified in colon and in liver during a pathological process and the dysregulation of DPD increased from a benign to a malignant tissue.