Determination of free extracellular levels of methotrexate by microdialysis in muscle and solid tumor of the rabbit

Simultaneous hyperthermia-chemotherapy effect by arterial injection of Fe(Salen) for femur tumor

We previously identified a novel nanomagnetic particle, N,N′‐bis(salicylidene)ethylenediamine iron [Fe(Salen)]. Fe(Salen) not only shows antitumor effects but also magnetic properties. We found that Fe(Salen) can be used for magnet‐guided drug delivery and visualization of accumulated drug by magnetic resonance imaging (MRI) because of its magnetism. In addition, Fe(Salen) can generate heat by itself when exposed to an alternating current magnetic field (AMF), resulting in a hyperthermia effect. Herein, we partly elucidated the antitumor mechanism of Fe(Salen) and carried out an i.v. repeated dose toxicity study to decide the therapeutic amount. Furthermore, we evaluated the antitumor effect of selective intra‐arterial injection or i.v. injection of Fe(Salen) by catheter and the hyperthermia effect of Fe(Salen) when exposed to AMF in vivo. We used a rabbit model grafted with VX2 cells (rabbit squamous cell carcinoma) on the right leg. Intra‐arterial injection of Fe(Salen) showed a greater antitumor effect than did i.v. injection. The combination of Fe(Salen) intra‐arterial injection and AMF exposure showed a greater antitumor effect than did either Fe(Salen) or methotrexate (MTX) without AMF exposure, suggesting that AMF exposure greatly enhanced the antitumor effect of Fe(Salen) by arterial injection by catheter. This is the first report that the effectiveness of Fe(Salen) was evaluated in the point of administration route; that is, selective intra‐arterial injection by catheter. Taken together, these results indicate a new administration route; that is, selective arterial injection of Fe(Salen) by catheter, and the development of a new strategy of simultaneous hyperthermia‐chemotherapy in the future.

Pharmacokinetic profile of methotrexate in psoriatic skin via the oral or subcutaneous route using dermal microdialysis showing higher methotrexate bioavailability in psoriasis plaques than in non-lesional skin

AIMS

The aim of this pilot study was to use microdialysis to evaluate levels of Methotrexate (MTX) directly in psoriatic skin following oral or subcutaneous administration of MTX to elaborate a complete pharmacokinetic profile within the dermal skin.

METHODS

Six patients with chronic plaque psoriasis on the arm undergoing treatment with MTX were included in a mono-centre clinical trial. Patients were under treatment with p.o. or s.c. MTX (7.5 and 15 mg) for at least 3 months. Interstitial fluid was collected ex vivo via dermal microdialysis from lesional or non-lesional skin and via intravenous microdialysis as well as blood serum every hour up to 10 h after methotrexate administration every hour. MTX was analysed via liquid chromatography.

RESULTS

The area under the curve (AUC) of methotrexate from peripheral blood was up to four times higher than from microdiaylsis, which detection of free unbound MTX. The AUC from dialysates in psoriatic lesional skin was higher than in non-lesional psoriatic skin, and the AUC levels from i.v. microdialysis were non-significantly higher than those from lesional psoriatic skin. Pharmacokinetic profiles were individually quite different and did not primarily depend on the dose or the means (p.o. vs. s.c.) in which it was administered.

CONCLUSION

Dermal microdialysis is a valid tool to evaluate levels of methotrexate in the skin of psoriasis patients. Drug levels and bioavailability of methotrexate were higher in lesional than non-lesional psoriatic skin. The individual AUC of MTX was not primarily dependent on the route or dose of administration.

Combined Microdialysis-Tumor Homogenate Method for the Study of the Steady State Compartmental Distribution of a Hydrophobic Anticancer Drug in Patient-Derived Xenografts

PURPOSE

To develop a reproducible microdialysis-tumor homogenate method for the study of the intratumor distribution of a highly hydrophobic anticancer drug (SN-38; 7-ethyl-10-hydroxycamptothecin) in neuroblastoma patient-derived xenografts.

METHODS

We studied the nonspecific binding of SN-38 to the microdialysis tubing in the presence of 2-hydroxypropyl-beta-cyclodextrin (HPBCD) in the perfusate. We calibrated the microdialysis probes by the zero flow rate (ZFR) method and calculated the enhancement factor (f = extrapolated SN-38 concentration at the ZFR / SN-38 concentration in the dialysed solution) of HPBCD. We characterized the extravasation of HPBCD to tumors engrafted in mice. In vivo microdialysis and terminal homogenate data at the steady state (subcutaneous pump infusions) were used to calculate the volume of distribution of unbound SN-38 (Vu,tumor) in neuroblastoma.

RESULTS

HPBCD (10% w/v) in the perfusate prevented the nonspecific binding of SN-38 to the microdialysis probe and enhanced SN-38 recovery (f = 1.86). The extravasation of HPBCD in the tumor during microdialysis was lower than 1%. Vu,tumor values were above 3 mL/g tumor for both neuroblastoma models and suggested efficient cellular penetration of SN-38.

CONCLUSIONS

The method contributes to overcome the limitations of the microdialysis technique in hydrophobic drugs and provides a powerful tool to characterize compartmental anticancer drug distribution in xenografts.

Effect of blood brain barrier permeability in recurrent high grade gliomas on the intratumoral pharmacokinetics of methotrexate: a microdialysis study

PURPOSE

Determining whether potentially therapeutic drug exposure is achieved within brain tumors in an exploratory clinical investigation would provide a rational basis for selecting agents for evaluation in phase II trials. This study investigated the use of microdialysis to assess intratumoral drug distribution in patients with recurrent high grade gliomas (HGG).

PATIENTS AND METHODS

Microdialysis catheters were placed during surgery for residual HGG 1-day before giving methotrexate (MTX) 12-g/m(2) by 4-h i.v. infusion. MTX was measured by Liquid Chromatography/Mass Spectrometry (LC/MS) in plasma and microdialysate during the infusion and for 24-h thereafter. Blood brain barrier (BBB) permeability of tissue in which the microdialysis probe was located was determined by digitally fusing brain CT and contrast enhanced MRI images.

RESULTS

The microdialysis probe was located in contrast enhancing tumor in two patients and nonenhancing tissue in two others. Cerebral drug penetration, as indicated by the ratio of the area under the MTX concentration-time curves in brain extracellular fluid and plasma, was considerably greater in contrast enhancing tumor (0.28-0.31) than nonenhancing tissue (0.032-0.094). Nevertheless, MTX concentrations in ECF exceeded 2-microM, the average concentration for 50% cell kill against glioma cell lines in vitro, for 20-26 h in both regions of the tumor.

CONCLUSIONS

Microdialysis is a very informative technique for characterizing the intratumoral pharmacokinetics of drugs, such as MTX, that do not freely penetrate the BBB. Establishing the catheter probe location relative to areas of BBB disruption is required to properly assess the significance of microdialysis data in this context.

Review of microdialysis in brain tumors, from concept to application: first annual Carolyn Frye-Halloran symposium

In individuals with brain tumors, pharmacodynamic and pharmacokinetic studies of therapeutic agents have historically used analyses of drug concentrations in serum or cerebrospinal fluid, which unfortunately do not necessarily reflect concentrations within the tumor and adjacent brain. This review article introduces to neurological and medical oncologists, as well as pharmacologists, the application of microdialysis in monitoring drug metabolism and delivery within the fluid of the interstitial space of brain tumor and its surroundings. Microdialysis samples soluble molecules from the extracellular fluid via a semipermeable membrane at the tip of a probe. In the past decade, it has been used predominantly in neurointensive care in the setting of brain trauma, vasospasm, epilepsy,and intracerebral hemorrhage. At the first Carolyn Frye-Halloran Symposium held at Massachusetts General Hospital in March 2002, the concept of microdialysis was extended to specifically address its possible use in treating brain tumor patients. In doing so we provide a rationale for the use of this technology by a National Cancer Institute consortium, New Approaches to Brain Tumor Therapy, to measure levels of drugs in brain tissue as part of phase 1 trials.

Use of microdialysis to study platinum anticancer agent pharmacokinetics in preclinical models

Microdialysis sampling of blood and extracellular fluid (ECF) of living tissue offers unique advantages for studying anticancer drug distribution, metabolism, and mechanisms of tumor drug resistance. We applied microdialysis sampling in a rat model to describe the pharmacokinetics of cisplatin and carboplatin simultaneously in blood and several peripheral tissues, including tumor tissue. After i.v. bolus drug administration, samples were collected every 10 min for 4-6 h using microdialysis probes implanted into the jugular vein, kidney, and either liver or subcutaneously growing breast tumor tissue in anesthetized Fisher 344 rats. Analyte concentrations are expressed as absolute extracellular concentrations obtained by correction of the data for in vivo recovery. For cisplatin, peak renal concentrations (mean, 36.7 and 80.1 micrograms/mL) always exceeded peak plasma (8.4 and 13.2 micrograms/mL) and hepatic (6.3 and 10.4 micrograms/mL) concentrations following 5 and 10 mg/kg doses, respectively. For carboplatin, doses of 20 and 30 mg/kg also resulted in high peak renal concentrations, which were similar at both dose levels (mean, 87.9 and 89.3 micrograms/mL). However, at 30 mg/kg peak hepatic carboplatin concentrations were increased significantly, resulting in a disproportionate 3.5-fold increase in mean AUC at the higher dose level. Tumor cisplatin and carboplatin AUCs were similar to that in the circulation, but variable, ranging from 52 to 109% of the corresponding plasma AUCs. Microdialysis was determined to be a reliable methodology for examining the in vivo disposition of platinum anticancer agents in multiple tissue types. Our results revealed expected large renal exposures following i.v. administration, and variable tumor exposure with dose. Significant increases in hepatic carboplatin exposure with increasing dose suggest a possible mechanism for high-dose carboplatin-induced hepatic toxicity.

Application of microdialysis to characterize drug disposition in tumors

Microdialysis is an in vivo sampling technique that was initially developed to measure endogenous substances in the field of neurotransmitter research. In the past decade, microdialysis has been increasingly applied to study the pharmacokinetics and drug metabolism in the blood and various tissues of both animals and humans. This paper describes the general aspects of this in vivo sampling technique followed by the survey of the recent papers regarding the application of microdialysis to characterize anticancer drug disposition in solid tumors. It can be concluded that microdialysis is a very suitable method to obtain drug concentration-time profiles in the interstitial fluid of solid tumors as well as of other variety of tissues.

Lowering of tumoral interstitial fluid pressure by prostaglandin E(1) is paralleled by an increased uptake of (51)Cr-EDTA

High intra-tumoral fluid pressure (TP(IF)) may impair uptake of anticancer drugs into tumors, contributing to poor efficiency in treatment of carcinomas. Here, we demonstrate that lowering of TP(IF) parallels increased transport of (51)Cr-EDTA (m.w. 341) into tumor interstitium. Introduction of 15 microg prostaglandin E(1) (PGE(1)) -methyl ester into the s.c. tissue surrounding transplanted rat colonic (PROb) carcinomas or chemically-induced rat mammary carcinomas, lowered TP(IF) by 30%. Transcapillary transport into the interstitium of PROb tumors quantified by microdialysis increased by 39.6% after PGE(1) treatment 40 min prior to administration of (51)Cr-EDTA (n=6; p<0.05) compared to vehicle (n=10). In mammary tumors, PGE(1) increased transport into the tumors by 86.9% over controls (n=16; p<0.05). Both tumors had well developed stroma containing collagen and hyaluronan. Our data demonstrate that adjuvant treatment with PGE(1) lowers TP(IF), and enhances transport into the tumors. This principle may be of value as adjuvant therapy in treatment of solid malignancies with currently used anticancer drugs.