Quantitation of anthracyclines in human hematopoietic cell subpopulations by flow cytometry correlated with high pressure liquid chromatography

Effects of orally active taxanes on P-glycoprotein modulation and colon and breast carcinoma drug resistance

BACKGROUND

The taxane paclitaxel (Taxol) is often of limited efficacy in chemotherapeutic regimens because some cancer cells express high levels of the efflux pump, P-glycoprotein (Pgp), which removes the drug from the cells. The orally active paclitaxel analog IDN-5109 has been reported to overcome Pgp-mediated drug resistance. We tested whether IDN-5109 acts by modulating Pgp activity.

METHODS

Human MDA435/LCC6mdr1 and MDA435/LCC6 breast carcinoma cells, which express and do not express Pgp, respectively, were incubated with [3H]IDN-5109 and paclitaxel to determine intracellular drug accumulation. Flow cytometry was used to analyze intracellular retention of two Pgp substrates, rhodamine 123 (Rh-123) and doxorubicin, in both breast carcinoma cell lines and in human colon carcinoma cells (SW-620, DLD1, and HCT-15, whose Pgp levels vary) treated with different taxanes. The effects of IDN-5109 and paclitaxel on tumor growth in vivo were studied with the use of tumors established through xenografts of Pgp-expressing SW-620 and DLD1 cells in severe combined immunodeficiency mice. All statistical tests were two-sided.

RESULTS

Pgp-expressing cells treated with IDN-5109 or with the taxane-based drug resistance reversal agent tRA96023, which blocks Pgp activity, retained 8.1- and 9.4-fold more Rh-123 (P =.0001), respectively, and 1.7- and 1.9-fold more doxorubicin (P =.001), respectively, than cells treated with paclitaxel. Non-Pgp-expressing cells treated similarly demonstrated no increased retention of either substrate. MDA435/LCC6mdr1 cells retained 5.3-fold more [3H]IDN-5109 than [3H]paclitaxel after 2 hours (P =.01). IDN-5109 showed statistically significantly higher tumor growth inhibition than paclitaxel against the SW-620 xenograft (P =.003).

CONCLUSIONS

IDN-5109 modulates Pgp activity, resulting in superior tumor growth inhibition against Pgp-expressing tumors as compared with paclitaxel. IDN-5109 may broaden the spectrum of taxane use to include colon tumors.

Carbamoylation of glutathione reductase by N,N-bis(2-chloroethyl)-N- nitrosourea associated with inhibition of multidrug resistance protein (MRP) function

Intracellular glutathione (GSH) concentrations have been implicated recently as a regulatory determinant of multidrug resistance protein (MRP)-mediated drug efflux. Inhibition of glutathione reductase (GR) activity of N,N-bis(2-chloroethyl)-N-nitrosourea (BCNU) has been employed extensively to investigate the role of GSH redox cycle in cellular function. The present study examined the effect of BCNU on the MRP-mediated efflux of doxorubicin in the multidrug-resistant human fibrosarcoma cell line HT1080/DR4 overexpressing MRP. No significant difference in GR activity between HT1080 (parental) and multidrug-resistant HT1080/DR4 cells was detected (38.6 +/- 2.2 and 37.8 +/- 5.28 nmol/min/10(6) cells, respectively). Exposure of HT1080 and HT1080/DR4 cells to 100-500 microM BCNU decreased GR activity concentration dependently with subsequent reduction in cellular GSH pools in both cell lines. Inhibition of GSH biosynthesis by D,L-buthionine-(S,R)-sulfoximine (D,L-BSO), a specific inhibitor of gamma-glutamylcysteine synthetase, significantly reduced MRP-mediated drug efflux and potentiated the cytotoxicity of doxorubicin in MRP-expressing HT1080/DR4 cells (dose modifying factor 20.8). While equally effective inhibition of GR activity by BCNU was observed in parental and resistant cells, a significant increase in intracellular retention of doxorubicin was only achieved in MRP-expressing HT1080/DR4 cells. Furthermore, inhibition of MRP function following treatment with BCNU or D,L-BSO was directly related to the degree of GSH depletion in MRP-expressing tumor cells [r = 0.94 (P < 0.001) and 0.99 (P < 0.001), respectively]. Based on northern blot analysis of MRP mRNA levels, exposure of HT1080/DR4 cells to BCNU did not produce down-regulation of MRP gene expression. The results reported herein indicate that derivatives of nitrosourea with carbamoylating properties are potent inhibitors of MRP function. Depletion of intracellular GSH pools by inhibition of the GSH redox cycle or GSH de novo biosynthesis significantly inhibited MRP-mediated doxorubicin transport and restored intracellular drug concentrations in vitro.

DiOC2(3) is not a substrate for multidrug resistance protein (MRP)-mediated drug efflux

Multidrug resistance (MDR) is often related to expression of P-glycoprotein (Pgp) or Multidrug Resistance Protein (MRP). Pgp-mediated MDR can be evaluated by determining cellular retention of fluorescent substrates by flow cytometry. This study determined if agents used to evaluate Pgp function also can be used to evaluate MRP function. Cellular retention of doxorubicin (Dox), Rhodamine-123 (Rh-123), and 3,3'-diethyloxacarbocyanine iodide (DiOC2(3)) were studied in MRP-expressing cell lines (HL60/Adr and HT1080/DR4), whereas a Pgp expressing cell line (A2780/Dx5) served as a positive control. Overexpression of Pgp correlated inversely with retention of Dox, Rh-123, and DiOC2(3); however, under identical experimental conditions (1 h reincubation in drug-free medium), no retention difference of the three agents was detected between parental and MRP-expressing resistant cells. Upon extending the reincubation time to 4 h, an efflux of Rh-123 and Dox in the resistant lines became apparent and even more pronounced after 24h; however, still no efflux was detectable for DiOC2(3). Incubation of the cells with a modulator of MDR, PAK-104P, negated the observed drug efflux in Pgp and MRP expressing cells, which correlated with increased sensitivity of the MDR lines to doxorubicin. Thus both Dox and Rh-123 can be used to evaluate MRP-function, but DiOC2(3) can not.

Serum can inhibit reversal of multidrug resistance by chemosensitisers

The purpose of this study was to evaluate to what extent the ability of various chemosensitisers (CS) to reverse P-glycoprotein-associated multidrug resistance (MDR) is reduced when tested in physiological serum protein concentrations. Utilising drug sensitivity and accumulation assays, the CS were tested in medium containing 10% fetal bovine serum and in 100% horse or human serum. Two RPMI 8226 human myeloma sublines were used which express different levels of P-glycoprotein. The CS were tested at various concentrations, including clinically achievable blood levels. When using the CS at high doses, wide differences were observed in the extent CS activity was diminished by serum. Verapamil, cyclosporin A and quinine were not affected, quinidine and medroxyprogesterone acetate were moderately inhibited, and amiodarone and trifluoperazine were largely inactivated. When the CS were used at concentrations achievable in humans, the activity of all agents except quinine was markedly reduced by serum. With respect to the extent to which CS activity was diminished by serum, good statistical correlation (r > 0.90, P < 0.001) was found between the use of cytotoxicity and drug accumulation assays, horse and human serum or cell lines with high and low levels of P-glycoprotein, respectively. These studies demonstrated that physiological serum protein concentrations can profoundly diminish the MDR reversing activity of particular CS. Some drugs, such as amiodarone and trifluoperazine, are largely inactivated by serum when used at a wide range of concentrations. Other agents, such as verapamil and cyclosporin A, are essentially unaffected when used at high doses but markedly inhibited at concentrations achievable in humans. These data suggest that in vitro studies of CS in medium containing low serum protein concentrations can result in misleading conclusions regarding the potential clinical activity of such agents.

Cell cycle kinetics of hematopoiesis before and after in vivo administration of GM-CSF in refractory anemia: evidence for a shortening of the granulocyte release time

GM-CSF administration to patients with refractory anemia (RA) induces an increase in neutrophils and eosinophils. We studied cell kinetic mechanisms underlying this observation using clonogenic assays and in vivo iododeoxyuridine labeling of bone marrow cells. Cell cycle kinetics were studied in three patients before and during GM-CSF administration (two daily subcutaneous injections of 54 or 108 micrograms). No consistent effect on the relative number of bone marrow CFU-GM was noticed. The DNA synthesis time and potential doubling time of low-density bone marrow cells remained essentially the same. A slight decrease (1.5-3.7%) in labeling index was found, originating from the myelo(-mono)cytic lineage. In all three patients the release time of labeled granulocytes from the bone marrow into the peripheral blood was shortened (before GM-CSF treatment 5-7 days and during GM-CSF 3-4 days). Cell cycle kinetics of CD34+ cells were studied in order to obtain kinetic information on immature precursor and progenitor cells. The DNA synthesis time of the CD34+ cells was shortened during GM-CSF therapy, resulting in a shorter potential doubling time. GM-CSF administration to patients with RA results in a rise in granulocytes that might be due partly to an accelerated release of granulocytes from the bone marrow compartment into the circulating blood and partly to an increased proliferative activity of the immature precursor and progenitor cells.

Chemomodulation of drugs involved in multidrug resistance in chronic lymphatic leukemia of the B-cell type

Reduced drug accumulation may be one reason for intrinsic drug resistance in chronic lymphatic leukemia of the B-cell type (B-CLL). Immunophenotyped leukemic human B-cells from 38 cases of B-CLL were characterized for P-glycoprotein (PGP) content. In all, 30 cases of B-CLL were additionally analyzed for further parameters: accumulation of daunorubicin (DNR, n = 20) and rhodamine 123 (Rh123, n = 30) in both the presence and the absence of verapamil (VRP). Also, 16 cases of B-CLL were analyzed for vincristine (VCR) accumulation with or without VRP. Concerning the relative expression of PGP, these 16 cases of B-CLL were representative for the whole group of 30 cases. Spontaneous accumulation of Rh123 and VCR varied over a wide range: accumulation of Rh123, by a factor of 11.8; accumulation of VCR, by a factor of 9.7; and accumulation of DNR, by a factor of 3.6. VRP modulated the accumulation of RH123 in 16/30 cases (53%), that of VCR in 69% of cases, and that of DNR in 11% of cases. The maximal VRP-mediated increases in accumulation amounted to factors of 1.3 for DNR, 2.3 for Rh123, and 7.8 for VCR. Spontaneous drug accumulation did not correlate with the extent of chemomodulation. The amount of PGP in B-CLL cells (all cases studied were PGP-positive) did not correlate with drug accumulation or with the extent of VRP-mediated chemomodulation. Thus, high expression of PGP is only partially responsible for defective drug accumulation in B-CLL. Only the degree of chemomodulation by VRP is predictive for the extent of the PGP-related functional drug accumulation defect. Thus, in B-CLL, PGP-independent drug accumulation defects seem to be as important as those mediated by PGP. The extent of this drug accumulation defect varies for the different drugs in the following order VCR > Rh123 > DNR. The relevance of PGP-mediated and -independent drug accumulation defects in vivo may depend to a large extent on the drug being used and on the individual cell type. Both types of defect in drug accumulation are of high importance when regimens include VCR a drug commonly used in second-line chemotherapy of B-CLL. Both defects in drug accumulation may be responsible for intrinsic VCR resistance in B-CLL.

Quantitation of cell-associated doxorubicin by high-performance liquid chromatography after enzymatic desequestration

A method for measuring cellular concentrations of the anthracycline doxorubicin was developed. The assay involves cell lysis and protein degradation by detergent and proteinase K treatment followed by DNA hydrolysis using DNase I. Prior to high-performance liquid chromatography, samples are deproteinized by the addition of ZnSO4 and methanol. The assay is linear with respect to both the cellular drug content and the number of cells assayed over the ranges tested, and drug recovery is close to 100%. The method has a limit of detection of 50 fmol injected doxorubicin. Within run and between-day coefficients of variation have consistently been found to be in the 5% and 10% range, respectively, in different cell lines exposed to doxorubicin in vitro. The method has been evaluated in analyses of doxorubicin levels in mononuclear blood cells of patients. The assay offers several advantages over commonly used organic extraction techniques and may improve cellular drug monitoring during anthracycline therapy in patients.

Intranuclear concentration measurements of doxorubicin in living leucocytes from patients treated for a lympho-proliferative disorder

The accumulation of doxorubicin (DOX) in white blood cells of treated patients has been studied by quantitative microspectrofluorometry. From blood samples of treated patients, leucocyte subpopulations were separated by the gradient method. Emission fluorescence spectra from a microvolume of a single living cell nucleus were analysed in terms of spectral shape and fluorescence yield between free and DNA-bound doxorubicin. With this non-destructive analysis technique, intranuclear doxorubicin concentrations were determined within +/- 10%. Doxorubicin concentrations were measured in patients treated with bolus injection. After an accumulation of DOX in leucocytes during the first 30 min, intranuclear doxorubicin concentration did not vary significantly for 24 h, whereas its concentration in plasma decreased. Despite large differences between patients, monocytes accumulated significantly more doxorubicin than granulocytes or lymphocytes did.

Chromatographic analysis of anticancer drugs

The present review on the methods for the analysis of anticancer drugs should be seen as an addition to the excellent work of Eksborg and Ehrsson published half a decade ago in this journal (Vol. 340, p.31). The style and format have been followed closely, with the focus again on chromatographic techniques. We felt it important to add a list of compound (group) structures as a service to the reader. Methods have been reviewed for alkylating agents, platinum compounds, antitumour antibiotics, antimetabolites, alkaloids, suramin, 1-hydroxy-3-amino-propylidene-1,1-bisphosphonate and tamoxifen.

HPLC and flow cytometric analyses of uptake of adriamycin and menogaril by monolayers and multicell spheroids

We have used both HPLC and flow cytometry to measure and compare the uptake of two anthracyclines, menogaril (MEN) and Adriamycin (ADR), in V79 Chinese hamster lung fibroblasts grown as monolayers and as 650 microns multicell spheroids. In order to compare intracellular drug accumulation in spheroid cells measured by the two methods, we converted mean channel fluorescence of the flow cytometer to drug uptake expressed as ng/10(6) cells by using a standard curve. The standard curve related the flow cytometric mean channel fluorescence, of monolayer cells exposed to either drug, to the intracellular drug accumulation determined by HPLC. This standard curve was then used to convert the mean channel fluorescence of cells from drug-exposed spheroids to ng/10(6) cells. Our results show that equal intracellular drug accumulation (determined by HPLC) in spheroids and monolayers does not result in equal cellular fluorescence emission (determined by flow cytometry) by these 2 cell populations. For example, monolayer cells with an intracellular MEN accumulation of 650 ng/10(6) cells, emit 40 units of fluorescence as measured by flow cytometry. However, spheroid cells with the same intracellular accumulation emit about 80 units of fluorescence. This results in the intracellular MEN uptake in spheroids measured by flow cytometry being as much as 2- to 3-fold higher than that measured by HPLC. Intracellular ADR accumulation measured by flow cytometry was also higher than that obtained by HPLC. In spite of the quantitative difference between the two methods, qualitatively both methods gave similar results. Thus, both techniques showed that at equal drug concentration in medium drug uptake in monolayers was much greater than in spheroids.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of verapamil on the cellular accumulation of daunorubicin in blast cells and on the chemosensitivity of leukaemic blast progenitors in acute myelogenous leukaemia

Verapamil, a calcium channel blocker, was studied for its effects on the cellular daunorubicin (DNR) accumulation in blast cells and on the sensitivity of the blast progenitors to DNR in 30 acute myelogenous leukaemia (AML) patients. Using flow cytometry, verapamil was shown to increase the accumulation of DNR in blast cells. The effect was more prominent in the patients who showed poorer response to chemotherapy including DNR. The per cent increases of DNR content by verapamil were 6.4 +/- 6.3% and 19.5 +/- 23.1% in the 16 responders and the 14 nonresponders, respectively (P less than 0.05). The data suggest the presence of enhanced efflux of DNR in nonresponders. Marked variation in the effects of verapamil among nonresponders suggests the heterogeneity of the mechanisms of drug resistance involved. Verapamil also enhanced the sensitivity of blast progenitors to DNR. The degree of increase of cellular DNR accumulation by verapamil correlated with the degree of increase in chemosensitivity of blast progenitors (nonresponders, P less than 0.005; responders, P less than 0.05). We conclude that enhanced efflux of DNR in blast progenitors may be related to remission induction failure in at least some of resistant AML patients.

Clinical pharmacokinetics of doxorubicin

Doxorubicin (adriamycin) has a very wide antitumour spectrum, compared with other anticancer drugs; however, except for Hodgkin's disease, it is not associated with curative chemotherapy. Doxorubicin has been in clinical use for more than 2 decades, and only recently has it been recognised that the cytotoxic effect is produced at the cellular level by multiple mechanisms which have not yet been conclusively identified. Key factors are a combination of doxorubicin-induced free radical formation due to metabolic activation, deleterious actions at the level of the membrane, and drug-intercalation into DNA. Multiple aspects of the clinical pharmacokinetics of this drug have been described. Wide interpatient variations in plasma pharmacokinetics have been noted, but without firm relation to clinical outcome. An apparent volume of distribution of approximately 25 L/kg points to extensive uptake by tissues. Up to several weeks after administration, significant concentrations of doxorubicin have been found in haematopoietic cells and in several other tissues. The maximum cellular doxorubicin concentrations reached in vivo remain significantly below those at which all clonogenic leukaemic cells are killed in vitro. Doxorubicin has been administered as frequent (weekly) low doses, single high doses, and as a continuous infusion. The optimal schedule with respect to tumour cytotoxicity and dose-limiting side effects such as myelosuppression or cardiotoxicity, has never been investigated in a prospective, randomised manner. Clinical trials large enough to study optimal, and possibly individualised, doxorubicin chemotherapy need to be performed. This review summarises pharmacological and pharmacodynamic data of doxorubicin, and discusses these in relation to possible improvement of its therapeutic index. Furthermore, drug interactions, dose-response relationships, mechanisms of action, multidrug resistance, and treatment scheduling are discussed in the perspective of the development of novel treatment strategies.

In vivo cellular adriamycin concentrations related to growth inhibition of normal and leukemic human bone marrow cells

Inhibition of clonogenicity of normal and leukemic human hematopoietic progenitor cells was studied after in vivo and in vitro exposure of bone marrow to adriamycin (ADM). Flow cytometric determination of cellular ADM concentrations in blast cells, expressed in fluorescence units/cell (FU/cell), correlated well with the extent of cytotoxicity. After 2 h in vitro exposure to 500 ng ADM/ml, the ADM concentration of leukemic (n = 7) and normal (n = 4) bone marrow blast cells amounted to 231 +/- 180 and 249 +/- 53 FU/cell respectively, producing moderate decreases in clonogenicity by 44 +/- 30 and 54 +/- 27%. Exposure to 2000 ng/ml produced ADM concentrations of 1184 +/- 472 FU/cell for leukemic blast cells and 1024 +/- 281 FU/cell for normal blast cells. Inhibition of clonogenicity was 96 +/- 7% in leukemic blasts and 99 +/- 1% in normal blasts. In vivo ADM concentrations in leukemic blast cells at 1-2 h after administration were 216 +/- 98 FU/cell (n = 8 patients). This implies that inhibition of clonogenicity after administration of conventional dosages of ADM will be approx. 60-70% for both leukemic and normal bone marrow progenitor cells. Such values were noted in four patients of whom bone marrow was cultured, which was obtained shortly after ADM monotherapy.

In-beam light absorption measurement of anthracyclines in cells with a flow-through system

A flow-through cuvette in which cells attach as a monolayer to a quartz plate was developed for measurement of the light absorbance of anthracyclines in cells. Despite the drawback of a short path-length (of the order of the cell diameter), a dynamic flow-through set-up and baseline storage made it possible to measure intracellular absorbance and obtain spectral data for daunomycin and carminomycin. Stopping the flow and allowing the drug to equilibrate between medium and cells led to a 20% decrease of molar light absorption of cellular anthracycline, which permitted measurement of the total cellular concentration. Furthermore, accumulation and efflux kinetics were determined for H35 rat hepatoma cells. On the basis of the reported formation constant of the iron-complex of carminomycin, which is of the order of 10(34), we expected to find this complex within the cells. However, the spectrum of cellular drug did not show absorbance bands characteristic of the complex. A red shift and hypochromism were found in the daunomycin spectrum after intracellular binding, which corresponds with the spectral change observed after intercalation of daunomycin into DNA.

Leukemic cell and plasma daunomycin concentrations after bolus injection and 72 h infusion

The effect of the duration of daunomycin (DNM) infusion on leukemic cell drug concentrations was evaluated. Cellular and plasma DNM concentrations were measured in 20 patients with acute non-lymphocytic leukemia. DNM 45 mg/m2 was administered either as a bolus injection or as a 4-, 8- or 72-h constant-rate infusion during 3 consecutive days. Peak plasma DNM levels amounted to 227 +/- 116 ng/ml after bolus injection and were only 16 +/- 6 ng/ml after 72-h DNM infusions. Terminal plasma DNM half-lives were 14 +/- 4 h. Peak leukemic cell DNM concentrations at the 3rd day of administration were 16810 +/- 2580 ng/10(9) cells (bolus injections) and 10310 +/- 5510 ng/10(9) cells (72-h infusions). The areas under the cellular curve were similar and independent of the duration of the DNM infusion. Peak leukemic cell daunomycinol (DNMol) concentrations were respectively 3500 +/- 1600 ng/10(9) cells and 2850 +/- 1720 ng/10(9) cells. Cellular DNM terminal half-life was 13 +/- 4 h. DNM concentrations in nucleated blood and bone marrow cells correlated well (r = 0.93, n = 26). Long-term infusion produced less severe side effects. Therapeutic efficacy was maintained during long-term infusion.

Cellular and plasma adriamycin concentrations in long-term infusion therapy of leukemia patients

To determine whether long-term adriamycin (ADM) infusions resulted in cellular ADM concentrations at least comparable to those observed after bolus injections, ADM cellular and plasma concentrations were measured in 18 patients with leukemia. ADM was administered at 30 mg/m2 per day for 3 days, either as bolus injections or as 4-, 8-, or 72-h infusions. Negligible accumulation of plasma ADM was observed. Peak plasma ADM concentrations after bolus injections were 1640 +/- 470 ng/ml (n = 7). Maximum levels were 176 +/- 34 ng/ml during 4-h infusion (n = 5); 85 +/- 50 ng/ml during 8-h infusion (n = 4); and 47 +/- 5 ng/ml (n = 2) after 72-h infusion. ADM concentrations in nucleated blood and bone marrow cells correlated well (r = 0.82, n = 47). ADM accumulated in leukemic cells up to 30-100 times the plasma concentrations. The shorter the administration time-span, the higher the peak leukemic cell concentration and the greater the loss of drug immediately after the end of the administration. The final cellular ADM half-life was approximately 85-110 h. After long-term infusion and bolus injection of the same dose, similar areas under the curve for plasma or leukemic blast cell ADM concentrations were attained. Since comparable therapeutic efficacy was observed in all regimens, the antileukemic effect appeared not to be related to the peak plasma concentrations, while acute toxicity phenomena decreased with increasing duration of the infusion. Long-term ADM infusion deserves more attention in the treatment of patients with anthracyclines.

Infusion-rate independent cellular adriamycin concentrations and cytotoxicity to human bone marrow clonogenic cells (CFU-GM)

The effect of adriamycin (ADM) infusion-rate on cellular ADM concentrations and on clonogenicity of human haematopoietic cells was studied in vivo and in vitro. In patients an ADM dose of 30 mg m-2 was administered as a bolus injection, or as a 4 h or a 24 h infusion. In vitro the effect of ADM on clonogenic cell growth was determined after exposure during 5 min, 2 h and 24 h of human bone marrow cells to increasing ADM concentrations. ADM showed rapid intracellular accumulation, to levels 100-fold the plasma concentration in vivo or the incubation medium concentration in the in vitro experiments. After a bolus injection or 5 min exposure only approximately 10% of the cellular peak ADM was retained after elimination of the drug from the plasma or the incubation medium. Ninety percent of the ADM was apparently 'loosely' bound. After 4 h and 24 h constant-rate infusions and also after 2 h and 24 h incubations in vitro, the cells accumulated ADM gradually, and the subsequent washing-out of the cellular ADM was substantially less, most of the ADM being 'tightly' bound. Despite these different patterns of uptake and retention after in vivo short- and long-lasting infusion of the same total dose, the 'tightly-bound' cellular ADM concentrations were the same. Moreover, comparable cellular ADM concentrations, retained after efflux of the 'loosely-bound' cellular ADM fraction were equally cytotoxic to normal human clonogenic cells. Short-lasting cellular peak ADM concentrations which occur after a bolus injection or after short exposure to high ADM concentrations are not essential for the cytotoxic effect, in contrast to the retained, 'tightly-bound' cellular ADM levels.

Investigation of the role of mononuclear phagocytes in the transportation of doxorubicin-containing liposomes into a solid tumor

The present paper is concerned with the question whether cells of the mononuclear phagocyte system (MPS) function as a transport system for doxorubicin (DXR)-containing liposomes into solid tumors. The investigations were performed in solid IgM immunocytoma bearing Lou/M Wsl rats. In this tumor system macrophage accumulation was observed during DXR and cisplatin induced tumor regression. Tumor-bearing rats were treated i.v. with 1 mg/kg DXR (either free or entrapped in liposomes) for 4 consecutive days. Changes in the cellular composition of the tumor were studied by histology and cytology comparing free and liposomal DXR treatment. Therapy with DXR-liposomes (lip DXR) induced macrophage accumulation similar to free DXR. No differences in cellular changes in the tumor between both types of treatment were found. The DXR-content of tumor-associated cells was measured at various times during treatment with free or lip DXR by means of flow cytometry. Most DXR-fluorescence was associated with dead cells and cellular debris. No clear-cut differences in DXR-content were found between macrophages isolated from tumors of free DXR treated animals and those isolated from lip DXR treated animals. In order to investigate whether DXR-liposomes are taken up by tumor tissue (either via macrophages or directly by the tissue itself), [3H]inulin-labeled DXR-liposomes were administered to tumor-bearing rats. The distribution of radiolabeled lip DXR in non-treated rats was compared with that in rats which were pretreated with non-radiolabeled lip DXR to induce macrophage accumulation. In both untreated and pretreated animals most of the administered 3H-dose was recovered in liver and spleen. Only a minor fraction was recovered from the tumor and other tissues. This fraction was not higher than that obtained when a comparable amount of free [3H]inulin was injected. In conclusion, this study suggests that DXR-liposomes do not enter the solid IgM immunocytoma, even when during therapy macrophages pass the endothelial barrier. Therefore, it is unlikely that macrophage-mediated transportation of DXR-liposomes into the tumor is involved in the mechanism of tumor regression induced by liposome-entrapped DXR.

Cellular and plasma pharmacokinetics of weekly 20-mg 4'-epi-adriamycin bolus injection in patients with advanced breast carcinoma

Weekly low-dose injections of 20 mg 4'-epi-adriamycin (E-ADM) were given to 12 patients with advanced postmenopausal breast cancer for at least 8 weeks. In advance, all patients were given hormonal therapy and polychemotherapy not containing anthracyclines. E-ADM concentrations in plasma and urine and in blood and bone marrow cells were determined during 8 consecutive weeks. Plasma concentrations in the range of a few nanograms per milliliter were seen up to 72-96 h. Cellular concentrations appeared to be more than 100-fold the plasma concentrations, and were 190 +/- 66 ng/10(9) cells on day 8, before the next injection was given. Nevertheless, no serious bone marrow toxicity was observed. In two patients with an increased plasma bilirubin concentration, cellular E-ADM concentrations were 20%-40% higher than those observed in the other patients. Plasma concentrations of E-ADM and 4'-epi-adriamycinol showed terminal half-lives 2-3 times longer and could be followed throughout the week. In three patients biopsies of skin metastases were examined. In two patients E-ADM could be demonstrated in the tumor tissue up to 7 days after the last injection. Although the number of patients investigated is too small to relate the drug kinetics to clinical response, it is of interest that the two patients with the highest cellular E-ADM concentrations responded better than the others.

Characterization of a doxorubicin-resistant murine melanoma line: studies on cross-resistance and its circumvention

A B16 mouse melanoma cell line resistant to doxorubicin was obtained by continuous in vitro exposure to the drug. The ID50 for this line was 200 times higher than that for the parental cell line. The resistant cell line had some biological characteristics similar to those of the sensitive parental cell line, like saturation density and protein content. Differences were found in doubling time which was longer, cloning efficiency which was lower and DNA content which was higher in the resistant as compared to the parental line. Intracellular distribution of doxorubicin was also different having a nuclear-cytoplasmic ratio higher in sensitive than in resistant cells. Melanin content was an unstable feature in the sensitive cell line, whereas melanin was always present in resistant cells. Resistance to doxorubicin was maintained during 50 in vitro passages in the absence of the drug. Cross-resistance was found with vincristine and other anthracyclines, like daunorubicin and 4'-epi-doxorubicin but not with cis-platinum, and a new doxorubicin derivative, 4'-deoxy-4'-iodio-doxorubicin. The B16 line showed a lower resistance index to 4'-deoxy-doxorubicin and 4-demethoxy-daunorubicin (30 and 3 respectively), as compared to doxorubicin. Doxorubicin-resistance was partially circumvented by pretreatment of resistant cells with verapamil, a calcium chelating agent, and by trifluoperazine, a calmodulin-antagonist.

Anthracycline antitumour agents. A review of physicochemical, analytical and stability properties

A review of physicochemical and analytical properties of anthracycline antitumour agents is presented. The following subjects are discussed: protolytic equilibria, partition and partition coefficients, self-association, adsorptive properties, metal complexation, spectroscopy and chromatography. Furthermore, the stability of anthracyclines in solutions, in pharmaceutical preparations and in biological media is discussed.

Cell size, DNA, and cytokeratin analysis of human head and neck tumors by flow cytometry

Cell subsets have been discriminated in cell suspensions derived from 37 human head and neck tumors by means of light scatter, DNA, and cytokeratin flow cytometry (FCM). Cell dispersion was performed overnight at 4 degrees C in two different enzyme mixtures, i.e., trypsin/dithioerythritol and collagenase/DNase, under slight agitation of sliced tumor tissue. Cells were examined before and after fractionation on a discontinuous low-density bovine serum albumin (BSA) gradient. Forward and right-angle light scatter FCM of 23 tumor specimens revealed four main subpopulations with different size and structure. Fractionation of primary cell suspensions on a BSA gradient at unit gravity separated debris, small cells and large cells. DNA FCM of the enriched populations demonstrated a relation between large cells and DNA aneuploidy. Epithelial cells, as recognized by cytokeratin antibodies, were also related with large cells. The results demonstrated the usefulness of light scatter, DNA, and cytokeratin analysis of crude and fractionated tumor cell suspensions for assessment of the efficacy of a particular dispersion technique and to obtain information of the cell subsets dispersed.