Doxorubicin Levels Research Articles

Capillary electrophoresis monitors enhancement in subcellular reactive oxygen species production upon treatment with doxorubicin.

This study investigated the role of doxorubicin (DOX) accumulation in reactive oxygen species (ROS) production detected in individually electrophoresed organelles, including mitochondria, acidic organelles, and peroxisomes. While bulk measurements of ROS production in cells and organelles are not capable of discriminating between the effects of preparative procedures on measured ROS production, capillary electrophoresis with dual laser-induced detection of individual organelles demonstrated a difference in the measured ROS production as a result of various preparative procedures. Using this technique, the three different types of detected organelles (i) produce ROS and do not have detectable levels of DOX, (ii) contain detectable DOX but do not produce ROS, or (iii) produce ROS and accumulate DOX. The third type displays two subpopulations of organelles, one of which demonstrated a direct relationship between DOX uptake and subsequent ROS production, corresponding most likely to mitochondria, and a second one with low DOX uptake but large variation in ROS production, corresponding most likely to acidic organelles.

Cytostatic lung perfusion results in heterogeneous spatial regional blood flow and drug distribution: Evaluation of different cytostatic lung perfusion techniques in a porcine model

Comparison of doxorubicin uptake, leakage and spatial regional blood flow, and drug distribution was made for antegrade, retrograde, combined antegrade and retrograde isolated lung perfusion, and pulmonary artery infusion by endovascular inflow occlusion (blood flow occlusion), as opposed to intravenous administration in a porcine model. White pigs underwent single-pass lung perfusion with doxorubicin (320 mug/mL), labeled 99mTc-microspheres, and Indian ink. Visual assessment of the ink distribution and perfusion scintigraphy of the perfused lung was performed. 99mTc activity and doxorubicin levels were measured by gamma counting and high-performance liquid chromatography on 15 tissue samples from each perfused lung at predetermined localizations. Overall doxorubicin uptake in the perfused lung was significantly higher (P = .001) and the plasma concentration was significantly lower (P < .0001) after all isolated lung perfusion techniques, compared with intravenous administration, without differences between them. Pulmonary artery infusion (blood flow occlusion) showed an equally high doxorubicin uptake in the perfused lung but a higher systemic leakage than surgical isolated lung perfusion (P < .0001). The geometric coefficients of variation of the doxorubicin lung tissue levels were 175%, 279%, 226%, and 151% for antegrade, retrograde, combined antegrade and retrograde isolated lung perfusion, and pulmonary artery infusion by endovascular inflow occlusion (blood flow occlusion), respectively, compared with 51% for intravenous administration (P = .09). 99mTc activity measurements of the samples paralleled the doxorubicin level measurements, indicating a trend to a more heterogeneous spatial regional blood flow and drug distribution after isolated lung perfusion and blood flow occlusion compared with intravenous administration. Cytostatic lung perfusion results in a high overall doxorubicin uptake, which is, however, heterogeneously distributed within the perfused lung.

Determination of doxorubicin in rabbit ocular tissues and pharmacokinetics after intravitreal injection of a single dose of doxorubicin-loaded poly-β-hydroxybutyrate microspheres

A validated HPLC method was developed for the quantification of doxorubicin in rabbit ocular tissues using solid phase extraction and ultraviolet detection. Chromatographic separation of doxorubicin in various ocular tissues was performed on a C18 column. The mobile phase was composed of 0.2 M KH 2PO 4 buffer solution, acetonitrile and triethylamine in volumetric ratio of 70/30/0.2, adjusted to pH 4.0 with orthophosphoric acid. The calibration curve was linear over the range of 0.03–10, 0.03–10, 0.05–10 and 0.05–10 μg/ml in vitreous body, iris, retina/choroids and sclera, respectively. The intra-day and inter-day precisions in all ocular tissues were smaller than 4.95% and 5.73%, and the accuracies were about 100%. The extraction recoveries of doxorubicin in all of the ocular tissues were between 83.47% and 96.33%. After intravitreal administration of doxorubicin-loaded poly-β-hydroxybutyrate microspheres, doxorubicin level in ocular tissues was much lower than that for administration of free doxorubicin, which was helpful to reduce the associated toxicity to surrounding tissues. Doxorubicin was detectable even after tens of days in the studied ocular tissues.

Carcinogens induce genome-wide loss of heterozygosity in normal stem cells without persistent chromosomal instability

Widespread losses of heterozygosity (LOH) in human cancer have been thought to result from chromosomal instability caused by mutations affecting DNA repair/genome maintenance. However, the origin of LOH in most tumors is unknown. The present study examined the ability of carcinogenic agents to induce LOH at 53 sites throughout the genome of normal diploid mouse ES cells. Brief exposures to nontoxic levels of methylnitrosourea, diepoxybutane, mitomycin C, hydroxyurea, doxorubicin, and UV light stimulated LOH at all loci at frequencies ranging from 1-8 x 10(-3) per cell (10-123 times higher than in untreated cells). This greatly exceeds the frequencies at which these agents have been reported to induce point mutations and is comparable to the rates of LOH observed in ES cells lacking the gene responsible for Bloom syndrome, an inherited DNA repair defect that results in greatly increased risk of cancer. These results suggest that LOH contributes significantly to the carcinogenicity of a variety of mutagens and raises the possibility that genome-wide LOH observed in some human cancers may reflect prior exposure to genotoxic agents rather than a state of chromosomal instability during the carcinogenic process. Finally, as a practical matter, chemically induced LOH is expected to enhance the recovery of homozygous recessive mutants from phenotype-based genetic screens in mammalian cells.

Pharmacokinetic and Safety Study of Doxorubicin-eluting Beads in a Porcine Model of Hepatic Arterial Embolization

To present the pathologic and pharmacokinetic findings from hepatic embolization in a porcine model comparing doxorubicin-eluting beads with bland embolization and to correlate these findings with in vitro release kinetics. Drug-eluting beads (DEB; 100-300 microm and 700-900 microm) loaded with 37.5 mg doxorubicin per milliliter hydrated beads were used to embolize the hepatic artery feeding the left lobe of the liver in young adult Yucatan pigs (n = 5 per group). Control animals underwent embolization with bland beads (100-300 microm; n = 5). Systemic plasma levels of doxorubicin were measured and correlated to in vitro drug release. Blood sampling and histopathologic examination were performed during the 90-day follow-up. All animals underwent successful embolization, and the treatment was well tolerated. Mean volumes of beads administered were 2.0-3.4 mL, with mean doses of 127.5 mg and 78.7 mg of doxorubicin for the 100- to 300-microm and 700- to 900-microm DEB groups, respectively. Gross pathologic examination revealed no effects on organs other than the liver. There was a transient increase in liver enzyme levels, particularly in the groups of animals who underwent embolization with 100- to 300-microm DEB. Histopathologic study showed mostly nonnecrotic changes with bland beads, whereas the effects of DEB were more severe, with large areas of pannecrosis evident with the 100- to 300-microm DEB. Maximum plasma concentrations were 651 ng/mL and 42.8 ng/mL for the 100- to 300-microm and 700- to 900-microm DEB groups, respectively, observed at 1 minute for both groups. Correlation with in vitro data showed a strong linear relationship. Hepatic arterial embolization with DEB was shown to be safe and well tolerated. The locoregional delivery of doxorubicin from DEB caused targeted tissue damage with minimal systemic impact and could be a promising new approach to transarterial chemoembolization of solid tumors.

Her2-targeted pegylated stealth liposomal doxorubicin (PLD) retains its specific targeting ability to Her2-expressing tumor cells after in vivo circulation and extravasation to mouse malignant ascites

13097 Background: Receptor-directed targeting of ligand-bearing liposomes to tumor cells may enhance therapeutic efficacy by intracellular delivery of a concentrated payload of liposomal drug. The goal of this study was to assess whether Her2-targeted PLD retains its binding ability to Her2-expressing target cells through circulation in the blood and extravasation to the ascitic fluid of mice with malignant ascites. Methods: PLD was grafted with a pegylated lipophilic conjugate of an anti-Her2 scFv antibody fragment (F5) at a ratio of 15 ligands per liposome. BALB/c mice were injected with J6456 lymphoma cells into the peritoneal cavity to generate malignant ascites. When abdominal swelling developed, Her2-targeted PLD and nontargeted PLD were injected into the mice i.v. at a dose of 15 mg/kg. The ascitic fluid was collected 48 hr later, ascitic tumor cells were removed, and the doxorubicin levels in the cell-free ascitic fluid and plasma were determined. Binding of the liposome-containing ascitic fluid was tested in vitro against Her2-expressing human tumor cell lines (N87, SKBR-3) and compared to the binding of shelf formulations (not passaged in vivo) of Her2-PLD and PLD, using as parameter the amount of cell-associated doxorubicin. Results: Plasma and ascitic fluid levels of Her2-PLD were only slightly below those of PLD indicating that the Her2 ligand did not cause any significant change in the clearance rate of PLD. Her2-PLD and PLD bound to an equal extent to J6456 cells in vivo. The in vitro binding of Her2-PLD from ascites to Her2- expressing cells was increased 10 to 20-fold above that of PLD from ascites, similarly to the 20-fold difference in binding between shelf Her2-PLD and PLD. Conclusions: Her2-targeted PLD demonstrates similar circulation time to that of nontargeted PLD. After in vivo passage, the targeted liposome retains most of its original binding capacity to Her2 expressing cells indicating that the ligand is stably maintained in association with the doxorubicin liposomal carrier. Targeting of PLD using this Her2 antibody fragment should provide an important means of selective drug delivery to tumors expressing the Her2 receptor. [Table: see text]

A phase I study of pegylated doxorubicin (DOX) and weekly topotecan (TOP) in patients (pts) with advanced solid tumors

12018 Background: The primary endpoint of this prospective phase I study of DOX-TOP in pts with advanced solid tumors was to identify the maximum tolerated dose and dose-limiting toxicities (DLT) of this combination. Other objectives included a description of additional toxicities and efficacy in this patient population with refractory cancers. Pharmacokinetic sampling of TOP plasma levels will be reported separately. Methods: Eligible pts had advanced solid tumors and had either failed standard chemotherapy (chemo) or were pts for whom no standard therapy existed. They had ECOG PS = 0–2, adequate organ function, and gave written, informed consent. Initial doses included DOX 40 mg/m2 day 1 and TOP 2 mg/m2 days 1, 8 and 15 q 28 days. TOP was to be escalated in cohorts of pts. DLT was defined as febrile neutropenia, grade 4 thrombocytopenia, any grade 3 non-hematologic toxicity, or the inability to receive subsequent treatment due to ongoing toxicity. Treatment was held for ANC &lt; 1000 or platelets &lt; 75,000. Results: Fourteen pts have been enrolled on this phase I study, all of whom were evaluable for toxicity. There were 12 males and 2 females, and the median age was 57 years (range 25–86). Four had ECOG PS = 0, 9 had PS = 1, and 1 had PS = 2. Cancer types included head and neck (3), renal (2), and breast, pancreas, liver, esophagus, germ cell tumor, sarcoma, and others (one each). In the 6 pts treated at dose level 1, toxicities included grade 3 anemia (1) and neutropenia (2), and grade 4 neutropenia (1). DLT consisted of grade 4 thrombocytopenia (1) and inability to deliver day 15 TOP in 3/6 pts at this dose. Thus, TOP was reduced to 1.5 mg/m2 weekly for dose level -1, and 8 pts have been treated. Toxicities included grade 3 anemia (1)and neutropenia (2), and grade 4 neutropenia (1) and thrombocytopenia (1). Enrollment continues at this dose level to confirm tolerability. No patient achieved an objective response to therapy, but 2 pts have stable disease for up to 4 cycles. Conclusions: DOX-TOP can be safely combined in pts with advanced solid tumors, with hematologic toxicity as the DLT. The preliminary recommended phase II dose is DOX 40 mg/m2 and TOP 1.5 mg/m2. We plan to explore an additional dose level of DOX 30 mg/m2 and TOP 2 mg/m2. Phase II evaluation is contemplated in selected tumor types. [Table: see text]

An open-label study to evaluate dose and cycle dependence of the pharmacokinetics (PK) of pegylated liposomal doxorubicin (PLD)

2012 Background: There are no definitive data in humans on the dose dependency and/or cycle dependency of the pharmacokinetics of PLD. The skin toxicity of PLD tends to worsen after several treatment cycles. Therefore, it is important to characterize the PK of PLD after 2 or more cycles. Methods: Fifteen patients with various solid tumors were randomized to two arms of treatment in an open-label study. Arm A received PLD at doses of 60, 30, and 45 mg/m2 in 3 successive cycles every 4 weeks (q4w). Arm B received PLD at doses of 30, 60, and 45 mg/m2 in 3 successive cycles q4w. Twelve patients, 6 on each arm, completed all three cycles and were fully evaluable. Plasma levels of doxorubicin were analyzed by HPLC and fluorimetry following a previously published method (J Chromatogr B, 779:259–69, 2002) with minor modifications. PK analysis was done by non-compartmental method. The following parameters were obtained: Cmax, AUC∞, terminal half-life (T1/2), and Clearance (CL). The paired t test was used for statistical analysis. Results: There was no significant difference in the parameters examined when the dose was increased from 30 to 60 mg/m2. However, when we analyzed the effect of cycle number on the PK, we found a gradual and significant inhibition of CL when patients advance from the 1st through the 3rd cycle of PLD (p=0.0003), with a mean increase of 44% in AUC/mg dose (p=0.0011). Cmax and T1/2 mean values increased by 17% and 18% respectively between the 1st and 3rd cycles, but only the increase in T1/2 was statistically significant (p=0.0127). Conclusion: While the PK of PLD is not dose-dependent within the dose range of 30 to 60mg/m2, there is evidence of a cycle-dependent effect that results in inhibition of CL when patients receive successive cycles of PLD. This effect may account for the delayed skin toxicity of PLD. These results suggest the need for dose adjustments of PLD to minimize the risk of toxicity, such as an initial high loading dose followed by reduced maintenance doses from the 2nd or 3rd cycle onwards. [Table: see text] [Table: see text]

Phase I-II Study of Pegylated Liposomal Doxorubicin Combined With Weekly Paclitaxel as First-Line Treatment in Patients With Metastatic Breast Cancer

Pegylated liposomal doxorubicin (PLD) appears to be as active as doxorubicin in first-line metastatic breast cancer (MBC) patients, with lower cardiac toxicity. This phase I-II trial aimed to determine the dose limiting toxicity (DLT) and recommended dose (RD) of a first-line combination of PLD and weekly paclitaxel. MBC patients received PLD on day 1, administered over 60 minutes IV. (starting dose 30 mg/m2, escalation by 5 mg/m2 increments), and paclitaxel on days 1, 8, and 15. Initially (schedule A), paclitaxel was administered over 60 minutes (starting dose 80 mg/m2, 10 mg/m2 increments), then (schedule B) over 24 hours on day 1 (at a dose of 70 mg/m2, 10 mg/m2 increments), and in a 60 minute IV infusion at a fixed dose of 90 mg/m2 on days 8 and 15. Pharmacokinetics were assessed during cycle 1 in schedule B. Thirty patients were treated (schedules A = 9; B = 21). Because of cutaneomucous toxicities in all patients in schedule A with discontinuation in 5 patients, schedule B was explored. Two DLTs (febrile neutropenia) occurred, with PLD 35 mg/m2 with paclitaxel 80 mg/m2 day 1 and 90 mg/m2 days 8 and 15 identified as recommended dose. Pharmacokinetic evaluation revealed an interaction, with increased levels of free doxorubicin and PLD during the paclitaxel infusion. This combination according to schedule and dosages results in cutaneomucous and hematological toxicity, probably because of a pharmacokinetic interaction, which is poorly compatible with a good quality of life for MBC patients.

Enhancement of antitumor effect of doxorubicin by its complexation with γ-cyclodextrin in pegylated liposomes

In the present study, we examined tissue distribution and the antitumor effect of doxorubicin (DOX) after intravenous injection of the pegylated liposomes entrapping the DOX complex with γ-cyclodextrin (γ-CyD) (complex-in-liposome) in BALB/c mice bearing colon-26 tumor cells, compared with those of DOX solution, pegylated liposomes entrapping DOX alone (DOX-in-liposome), pegylated liposomes entrapping γ-CyD (CyD-in-liposome) and the binary system of DOX-in-liposome and CyD-in-liposome. When injected to the mice, complex-in-liposome provided the high DOX levels in plasma and solid tumors, compared with the other preparations. Reflecting the result, complex-in-liposome elicited the retardation of tumor growth and the improvement of survival rate without suppression of increase in the body weight of mice. These results suggest the potential use of pegylated liposomes entrapping the DOX complex with γ-CyD for a promising carrier for improvement of antitumor effects of DOX.

A Multicenter Phase I/II Trial Evaluating the Safety and Efficacy of Lenalidomide [Revlimidä (R), CC-5013] in Combination with Doxorubicin and Dexamethasone (RAD) in Patients with Relapsed or Refractory Multiple Myeloma.

Introdution:Lenalidomide (Revlimid™) is Celgene's lead clinical compound in a new group of drugs called IMiDs, which have immunomodularory properties. The drug has been evaluated in phase-I, II, and III clinical trials for the treatment of multiple myeloma (MM). Lenalidomide shows substantial anti-tumor activity in patients with refractory or relapsed MM and significantly prolongs time to tumor progression (TTP) compared to standard therapy in these patients. Lenalidomide was well tolerated in these trials, the only dose limiting toxicity in a phase-I trial was myelosuppression. In order to further improve therapeutic efficacy and to overcome drug resistance we are currently evaluating Lenalidomide (Revlimid™) in combination with doxorubicin and dexamethasone (RAD) for the treatment of patients with refracrory or relapsed MM in a phase-I/II trial.Methods:Patients with relapsed or refractory multiple myeloma recieve a fixed dose of either 10 mg or 15 mg Revlimid Revlimid™ given daily for 21 days (d 1–21) in combination with doxorubicin (adriamycin) and dexamethasone, to be repeated on day 29. Three dose levels of doxorubicin (adramycin) are planned: 4 mg/m2 day 1–4, 6 mg/m2 day 1–4 and 9 mg/m2 day 1–4. 40 mg dexamethasone is given orally day 1–4 and day 17–20 at a fixed dose. 3– 6 cycles are applicated unless severe toxicity or disease progression occurs.Results:RAD treatment was well tolerated at dose level 1 and dose level 2. Therefore, current dose escalation is continued. All patients treated at the first two dose levels (6/6) responded to RAD treatment. Further updated results on this trial will be presented.

Determination of Doxorubicin Levels in Whole Tumor and Tumor Nuclei in Murine Breast Cancer Tumors

Pharmacokinetic studies on liposomal drugs have previously measured total drug levels in tumors, which include non-bioavailable drug. However, drugs must be released from liposomes to have activity. We have developed a method for measuring levels of bioavailable (released) doxorubicin in vivo in tumors that will allow therapeutic activity to be correlated with bioavailable drug levels. Mice orthotopically implanted with mammary carcinoma (4T1) were injected i.v. 10 days after implantation with free doxorubicin or formulations of liposomal doxorubicin with different drug release rates. Tumors were excised at various times after injection, and total tumor doxorubicin levels were determined by acidified isopropanol extraction of whole tumor homogenates. Bioavailable doxorubicin levels were determined by extraction of doxorubicin from isolated tumor nuclei. Free doxorubicin had high levels of bioavailability in tumor tissue; 95% of the total doxorubicin in tumors was bound to nuclear DNA by 24 hours after injection. Administration of Doxil, a slow release liposomal formulation of doxorubicin, gave an area under the time-versus-concentration curve (AUC) for total doxorubicin 7 days after injection that was 87-fold higher than that obtained for free doxorubicin, and 49% of the liposomal doxorubicin was bioavailable. For liposomes with a more rapid doxorubicin release rate, by 7 days after injection, the AUC(0-7 days) for total doxorubicin was only 14-fold higher than that for free doxorubicin and only 27% of liposomal doxorubicin was bioavailable. This technique allows correlations to be made between drug bioavailability and therapeutic activity and will help in the rational design of drug carriers.

An NCIC-CTG phase I dose escalation pharmacokinetic study of the matrix metalloproteinase inhibitor BAY 12-9566 in combination with doxorubicin

This phase I study was performed to evaluate the safety, tolerability, and efficacy of the oral matrix metalloproteinase inhibitor BAY 12-9566 in combination with doxorubicin in patients with advanced solid tumours, and to identify the maximum tolerated dose of these agents in combination and the dose for use in subsequent studies. 14 patients were entered onto 3 dose levels consisting of escalating doses of doxorubicin (50 mg/m(2), 60 mg/m(2) and 70 mg/m(2)) with 800 mg po bid BAY 12-9566. At all three dose levels, patients received doxorubicin alone in cycle one on day 1. Daily oral dosing with BAY 12-9566 was started on day 8 of cycle 1, and thus doxorubicin was given concurrently with BAY 12-9566 in cycle 2. Patients were continued on treatment until a dose limiting toxicity or tumour progression occurred. Pharmacokinetic studies from cycles 1 and 2 from the patients treated in the first three dose levels demonstrated that the addition of BAY 12-9566 increased the AUC(0-12h) levels of doxorubicin by a median of 48%. No effects were seen on the BAY 12-9566 pharmacokinetic values. Two dose limiting toxicities were seen at the third dose level. One patient experienced grade 3 stomatitis in cycle 2, and another patient experienced grade 4 granulocytopenia in cycle 1 and grade 4 thrombocytopenia in cycle 2. Thus the maximum tolerated dose of 60 mg/m(2) was declared. These toxicities were those that would have been expected from doxorubicin alone. BAY 12-9566 can be safely administered with full doses of doxorubicin without evidence of clinical interaction. The recommended dose of doxorubicin to be combined with BAY 12-9566 800 mg po b.i.d is 60 mg/m(2), however, further development of BAY 12-9566 has been abandoned.

Enhanced intracellular delivery and improved antitumor efficacy of doxorubicin by sterically stabilized liposomes modified with a synthetic RGD mimetic

While sterically stabilized liposomes (SSL) can passively accumulate into tumor tissue due to the effect of enhanced permeability and retention (EPR), the intracellular uptake of the entrapped anticancer drugs by the tumor cells should be a determinant step for their antitumor activities. Therefore, strategies that can enhance the intracellular uptake of SSL into tumor cells could lead to an improved therapeutic efficacy for the drugs. To check this possibility, RGD-mimetic-modified SSL (RGDm-SSL) were constructed aimed to achieve tumor accumulation as well as enhanced intracellular delivery, and were loaded with doxorubicin (DOX), an anticancer drug. Flow cytometry and confocal microscopy reveal that RGDm-SSL facilitated the DOX uptake into the melanoma cells via integrin-mediated endocytosis. DOX-loaded RGDm-SSL (RGDm-SSL-DOX) displayed higher cytotoxicity on melanoma cells than DOX-loaded SSL (SSL-DOX). Tissue distribution and therapeutic experiments were examined in C57BL/6 mice carrying melanoma B16 tumors. RGDm-SSL-DOX displayed similar DOX accumulation in tumor tissue to that of SSL-DOX but showed significantly lower DOX level in blood and remarkably higher DOX level in spleen than SSL-DOX. Administration of RGDm-SSL-DOX at a dose of 5 mg DOX/kg resulted in effective retardation of tumor growth and prolonged survival times compared with SSL-DOX. These results suggest that RGDm-modified SSL may be a promising intracellular targeting carrier for efficient delivery of chemotherapeutic agents into tumor cells.

Human Splicing Factor SPF45 (RBM17) Confers Broad Multidrug Resistance to Anticancer Drugs When Overexpressed— a Phenotype Partially Reversed By Selective Estrogen Receptor Modulators

The splicing factor SPF45 (RBM17) is frequently overexpressed in many solid tumors, and stable expression in HeLa cells confers resistance to doxorubicin and vincristine. In this study, we characterized stable transfectants of A2780 ovarian carcinoma cells. In a 3-day cytotoxicity assay, human SPF45 overexpression conferred 3- to 21-fold resistance to carboplatin, vinorelbine, doxorubicin, etoposide, mitoxantrone, and vincristine. In addition, resistance to gemcitabine and pemetrexed was observed at the highest drug concentrations tested. Knockdown of SPF45 in parental A2780 cells using a hammerhead ribozyme sensitized A2780 cells to etoposide by approximately 5-fold relative to a catalytically inactive ribozyme control and untransfected cells, suggesting a role for SPF45 in intrinsic resistance to some drugs. A2780-SPF45 cells accumulated similar levels of doxorubicin as vector-transfected and parental A2780 cells, indicating that drug resistance is not due to differences in drug accumulation. Efforts to identify small molecules that could block SPF45-mediated drug resistance revealed that the selective estrogen receptor (ER) modulators tamoxifen and LY117018 (a raloxifene analogue) partially reversed SPF45-mediated drug resistance to mitoxantrone in A2780-SPF45 cells from 21-fold to 8- and 5-fold, respectively, but did not significantly affect the mitoxantrone sensitivity of vector control cells. Quantitative PCR showed that ERbeta but not ERalpha was expressed in A2780 transfectants. Coimmunoprecipitation experiments suggest that SPF45 and ERbeta physically interact in vivo. Thus, SPF45-mediated drug resistance in A2780 cells may result in part from effects of SPF45 on the transcription or alternate splicing of ERbeta-regulated genes.

Changes in P-glycoprotein activity are mediated by the growth of a tumour cell line as multicellular spheroids.

BackgroundExpression of P-glycoprotein (P-gp), the multidrug resistance (MDR) 1 gene product, can lead to multidrug resistance in tumours. However, the physiological role of P-gp in tumours growing as multicellular spheroids is not well understood. Recent evidence suggests that P-gp activity may be modulated by cellular components such as membrane proteins, membrane-anchoring proteins or membrane-lipid composition. Since, multicellular spheroids studies have evidenced alterations in numerous cellular components, including those related to the plasma membrane function, result plausible that some of these changes might modulate P-gp function and be responsible for the acquisition of multicellular drug resistance. In the present study, we asked if a human lung cancer cell line (INER-51) grown as multicellular spheroids can modify the P-gp activity to decrease the levels of doxorubicin (DXR) retained and increase their drug resistance.ResultsOur results showed that INER-51 spheroids retain 3-folds lower doxorubicin than the same cells as monolayers however; differences in retention were not observed when the P-gp substrate Rho-123 was used. Interestingly, neither the use of the P-gp-modulating agent cyclosporin-A (Cs-A) nor a decrease in ATP-pools were able to increase DXR retention in the multicellular spheroids. Only the lack of P-gp expression throughout the pharmacological selection of a P-gp negative (P-gpneg) mutant clone (PSC-1) derived from INER-51 cells, allow increase of DXR retention in spheroids.ConclusionThus, multicellular arrangement appears to alter the P-gp activity to maintain lower levels of DXR. However, the non expression of P-gp by cells forming multicellular spheroids has only a minor impact in the resistance to chemotherapeutic agents.

Trastuzumab and Liposomal Doxorubicin in the Treatment of MCF-7 Xenograft Tumor-Bearing Mice: Combination Does Not Affect Drug Serum Levels

We assessed the combination of doxorubicin or liposomal doxorubicin with trastuzumab for alterations in peak serum drug levels, as these agents are increasingly being paired in the treatment of aggressive breast cancer. We hypothesized that trastuzumab would exhibit a slower rate of elimination from the serum when in combination with liposomal doxorubicin based on the known effects of liposomal doxorubicin on phagocytic cells of the mononuclear phagocyte system (MPS), which are responsible in part for the uptake and degradation of antibodies. Doxorubicin and trastuzumab serum levels were assessed following injection of free doxorubicin, liposomal doxorubicin, or trastuzumab into female RAG2-M mice bearing subcutaneous MCF-7(HER-2) tumors. The effects of combination drug treatment on tumor growth were compared to single-agent treatment. Peak serum trastuzumab levels were not altered as a result of addition of doxorubicin therapy, nor were doxorubicin levels altered over 24 h as a result of coadministration of trastuzumab. Liposomal doxorubicin administration did result in serum doxorubicin levels 200- to 1000-fold higher than with injection of free doxorubicin. For the specific combination of trastuzumab with doxorubicin, either in free or liposomal form, coadministered in mice, there was no impact of one drug on the other in terms of peak serum drug levels or efficacy.

IMPACT OF ENDOTOXIN-INDUCED CHANGES IN P-GLYCOPROTEIN EXPRESSION ON DISPOSITION OF DOXORUBICIN IN MICE

P-glycoprotein (PGP) encoded by the Mdr1 gene mediates the excretion of drugs in organs such as the liver and kidney. Inflammation has been shown to suppress the expression and activity of PGP in rodent liver, thus potentially altering the pharmacokinetics of drugs that are substrates of PGP. Here we examined the effect of endotoxin (lipopolysaccharide; LPS)-induced inflammation on the disposition of the PGP substrate doxorubicin (DOX) in the mouse. Male CD-1 mice received 5 mg/kg LPS intraperitoneally. DOX (5 mg/kg) was administered intravenously 24 h after LPS treatment. The time course of DOX levels in plasma, urine, bile, and tissues was analyzed by high performance liquid chromatography. PGP protein and mRNA expression in liver and kidney was measured using Western blots and reverse transcriptase polymerase chain reaction. As compared to controls, LPS-treated mice exhibited a significant decrease (50%) in biliary clearance and 3-fold increased renal clearance of DOX. These changes were associated with strongly reduced PGP protein levels (30% controls, p < 0.05) in the liver and increased PGP levels in the kidney (140% controls, p < 0.05). Hepatic mRNA levels of all Mdr isoforms were reduced in LPS-treated mice, whereas renal Mdr1b levels were increased. In LPS-treated mice, we also measured an increased area under the plasma concentration-time curve and reduced systemic clearance of DOX, as well as a 2- to 5-fold increase in the urinary excretion of the doxorubicin and doxorubicinol aglycones. Our data suggest that endotoxin-induced inflammation in mice causes differential regulation of PGP in liver and kidney, thereby altering the clearance profile of DOX.

Doxorubicin loaded pH-sensitive polymeric micelles for reversal of resistant MCF-7 tumor

In order to overcome multidrug resistance in solid tumors, doxorubicin (DOX) loaded pH-sensitive micelles of which surface was decorated with folate (PHSM/f) were evaluated both in vitro and in vivo experiments. PHSM/f were fabricated from a mixture of two block copolymers of poly( l-histidine) (M n: 5K)- b-PEG (M n: 2K)-folate (polyHis/PEG-folate) (75 wt.%) and poly( l-lactic acid) (M n: 3K)- b-PEG (M n: 2K)-folate (PLLA/PEG-folate) (25 wt.%). The PHSM/f showed more than 90% cytotoxicity of DOX resistant MCF-7 (MCF-7/DOX R) when cultured with PHSM/f at a concentration of 10 μg/ml DOX. The result was interpreted by a sequential event of active internalization of PHSM/f via folate-receptor mediated endocytosis and ionization of His residues which result in micelle destabilization and probably disturbance of endosomal membranes. This potential mechanism may endow the drug carriers to bypass Pgp efflux pump and sequestration of DOX in acidic intracellular compartments, yielding high cytotyoxicity. Experimental evaluation of tumor regression was carried out in a small animal model bearing s.c. MCF-7 or MCF-7/DOX R xenografts. The tumor (MCF-7/DOX R) volumes of mice treated with PHSM/f were significantly less than control groups treated with free DOX or similar micelles but without folate (PHSM). In the MCF-7/DOX R xenograft model, the accumulated DOX level of PHSM/f in solid tumors was 20 times higher than free DOX group, and 3 times higher than PHSM group. The results demonstrate that PHSM/f is a viable means for treating drug resistant tumors.

Development of multidrug resistance in a canine lymphoma cell line

New multidrug resistant cell lines developed from the canine B cell lymphoma cell line (GL-1) were characterized in terms of chemosensitivity to some antineoplastics and P-glycoprotein (Pgp) expression. GL-1 was continuously exposed to a culture medium containing gradually increasing levels of doxorubicin and the cells that could grow in the presence of doxorubicin were obtained. Chemosensitivity of these cells to various antineoplastics were investigated with or without verapamil, which reversed Pgp-mediated drug resistance. The expression of Pgp on the cells was also examined by Western blot analysis. As a result, three kinds of resistant cell lines, designated as GL-DOX60, 300, and 4000 were obtained. These cell lines showed stable proliferation in the medium containing 60, 300, and 4000 ng/ml, respectively. These cells were much more resistant to vincristine than doxorubicin. This resistance was strongly reversed by the presence of verapamil. On the other hand, cisplatin was effective enough in killing these derived cells. In the Western Blot analysis, some bands that reacted to the anti-human Pgp monoclonal antibodies were observed in GL-DOX4000. The cells derived from GL-1 have multidrug resistance potential mediated by canine Pgp. The cells produced in this experimental trial are considered to be useful models for various investigations on canine multidrug resistance.