The modulating effect of PSC 833, cyclosporin A, verapamil and genistein on in vitro cytotoxicity and intracellular content of daunorubicin in childhood acute lymphoblastic leukemia

Emerging nanotechnology-based therapeutics to combat multidrug-resistant cancer

Cancer often develops multidrug resistance (MDR) when cancer cells become resistant to numerous structurally and functionally different chemotherapeutic agents. MDR is considered one of the principal reasons for the failure of many forms of clinical chemotherapy. Several factors are involved in the development of MDR including increased expression of efflux transporters, the tumor microenvironment, changes in molecular targets and the activity of cancer stem cells. Recently, researchers have designed and developed a number of small molecule inhibitors and derivatives of natural compounds to overcome various mechanisms of clinical MDR. Unfortunately, most of the chemosensitizing approaches have failed in clinical trials due to non-specific interactions and adverse side effects at pharmacologically effective concentrations. Nanomedicine approaches provide an efficient drug delivery platform to overcome the limitations of conventional chemotherapy and improve therapeutic effectiveness. Multifunctional nanomaterials have been found to facilitate drug delivery by improving bioavailability and pharmacokinetics, enhancing the therapeutic efficacy of chemotherapeutic drugs to overcome MDR. In this review article, we discuss the major factors contributing to MDR and the limitations of existing chemotherapy- and nanocarrier-based drug delivery systems to overcome clinical MDR mechanisms. We critically review recent nanotechnology-based approaches to combat tumor heterogeneity, drug efflux mechanisms, DNA repair and apoptotic machineries to overcome clinical MDR. Recent successful therapies of this nature include liposomal nanoformulations, cRGDY-PEG-Cy5.5-Carbon dots and Cds/ZnS core–shell quantum dots that have been employed for the effective treatment of various cancer sub-types including small cell lung, head and neck and breast cancers.

Overexpression of P-glycoprotein and MRP-1 are pharmacogenomic biomarkers to determine steroid resistant phenotype in childhood idiopathic nephrotic syndrome

Steroid remains the keystone therapy for Idiopathic Nephrotic Syndrome (NS). Besides genetic factors and histological changes, pharmacogenomic factors also affect the steroid response. The upregulation of P-glycoprotein (P-gp) and Multidrug resistance-associated protein 1 (MRP-1) modulate the pharmacokinetics of steroids and may contribute to steroid resistance. Flow-cytometric analysis of P-gp, MRP-1 expression and functional activity on peripheral blood mononuclear cells (PBMCs) was carried out in steroid-sensitive nephrotic syndrome (SSNS) (n = 171, male 103, mean age = 8.54 ± 4.3); and steroid-resistant nephrotic syndrome (SRNS) (n = 83, male 43, mean age = 7.43 ± 4.6) patients. The genotypings of MDR-1 gene were carried out using PCR-RFLP. We observed that the percentage expression of P-gp (10.01 ± 2.09 and 3.79 ± 1.13, p < 0.001); and MRP-1 (15.91 ± 3.99 and 7.40 ± 2.33, p < 0.001) on lymphocyte gated population were significantly higher in SRNS than that of SSNS. The functional activity of P-gp and MRP-1 was also significantly escalated in SRNS as compared to SSNS (68.10 ± 13.35 and 28.93 ± 7.57, p < 0.001); (72.13 ± 8.34 and 31.56 ± 8.65, p < 0.001) respectively. AUC-ROC curve analysis revealed that P-gp and MRP-1 expression with a cut-off value of 7.13% and 9.62% predicted SRNS with the sensitivity of 90% and 80.7%; and specificity 90% and 80%, respectively. Moreover, MDR-1 homozygous mutant TT+AA for G2677T/A (rs2032582) was significantly associated with SRNS (p = 0.025, OR = 2.86 CI = 1.14-7.14). The expression of P-gp (9.68 ± 4.99 v/s 5.88 ± 3.38, p = 0.002) was significantly higher in the patients of homozygous mutant alleles compared to wildtype GG. The increased expression and functionality of P-gp and MRP-1 contribute to steroid resistance, and MDR-1 homozygous mutant G2677T/A promotes steroid resistance by inducing P-gp expression in NS.

High Expression of Lung Resistance Protein mRNA at Diagnosis Predicts Poor Early Response to Induction Chemotherapy in Childhood Acute Lymphoblastic Leukemia

BACKGROUND

Treatment failure in leukemia is due to either pharmacokinetic resistance or cell resistance to drugs.

MATERIALS AND METHODS

Gene expression of multiple drug resistance protein (MDR-1), multidrug resistance-related protein (MRP) and low resistance protein (LRP) was assessed in 45 pediatric ALL cases and 7 healthy controls by real time PCR. The expression was scored as negative, weak, moderate and strong.

RESULTS

The male female ratio of cases was 2.75:1 and the mean age was 5.2 years. Some 26/45 (58%) were in standard risk, 17/45(38%) intermediate and 2/45 (4%) in high risk categorie, 42/45 (93%) being B-ALL and recurrent translocations being noted in 5/45 (11.0%). Rapid early response (RER) at day 14 was seen in 37/45 (82.3%) and slow early response (SER) in 8/45 (17.7%) cases. Positive expression of MDR-1, LRP and MRP was noted in 14/45 (31%), 15/45 (33%) and 27/45 (60%) cases and strong expression in 3/14 (21%), 11/27 (40.7%) and 8/15 (53.3%) cases respectively. Dual or more gene positivity was noted in 17/45 (38%) cases. 46.5 % (7/15) of LRP positive cases at day 14 were in RER as compared to 100% (30/30) of LRP negative cases (p<0.05). All 8 (100%) LRP positive cases in SER had strong LRP expression (p=<0.05). Moreover, only 53.3% of LRP positive cases were in haematological remission at day 30 as compared to 100% of LRP negative cases (p=<0.05).

CONCLUSIONS

Our study indicated that increased LRP expression at diagnosis in pediatric ALL predicts poor response to early treatment and hence can be used as a prognostic marker. However, larger prospective studies with longer follow up are needed, to understand the clinical relevance of drug resistance proteins.

Risks and benefits of dietary isoflavones for cancer

A high intake of fruits and vegetables is associated with a lower risk of cancer. In this context, considerable attention is paid to Asian populations who consume high amounts of soy and soy-derived isoflavones, and have a lower risk for several cancer types such as breast and prostate cancers than populations in Western countries. Hence, interest focuses on soyfoods, soy products, and soy ingredients such as isoflavones with regard to their possible beneficial effects that were observed in numerous experiments and studies. The outcomes of the studies are not always conclusive, are often contradictory depending on the experimental conditions, and are, therefore, difficult to interpret. Isoflavone research revealed not only beneficial but also adverse effects, for instance, on the reproductive system. This is also the case with tumor-promoting effects on, for example, breast tissue. Isoflavone extracts and supplements are often used for the treatment of menopausal symptoms and for the prevention of age-associated conditions such as cardiovascular diseases and osteoporosis in postmenopausal women. In relation to this, questions about the effectiveness and safety of isoflavones have to be clarified. Moreover, there are concerns about the maternal consumption of isoflavones due to the development of leukemia in infants. In contrast, men may benefit from the intake of isoflavones with regard to reducing the risk of prostate cancer. Therefore, this review examines the risks but also the benefits of isoflavones with regard to various kinds of cancer, which can be derived from animal and human studies as well as from in vitro experiments.

Effects of naturally occurring polymethyoxyflavonoids on cell growth, p-glycoprotein function, cell cycle, and apoptosis of daunorubicin-resistant T lymphoblastoid leukemia cells

Effects of polymethoxyflavonoids tangeretin and nobiletin and the related polyphenolic compounds baicalein, wogonin, quercetin, and epigallocatechin gallate on the cell growth, P-glycoprotein function, apoptosis, and cell cycle of human T lymphoblastoid leukemia MOLT-4 and its daunorubicin-resistant cells were investigated. The IC50 values of these compounds on the cell growth were 7.1-32.2 micromol/L, and the inhibitory effects were observed to be almost equal to the parent MOLT-4 and the daunorubicin-resistant cells. Tangeretin and nobiletin showed the strongest effects with the IC50 values of 7.1-14.0 micromol/L. These polymethoxyflavonoids inhibited the P-glycoprotein function and significantly influenced the cell cycle (p<.05), whereas they did not induce apoptosis.

Major improvement of the reference method of the French drug resistance network for P-glycoprotein detection in human haematological malignancies

The aim of this study was to improve significantly the sensitivity and specificity of the flow cytometric assay of P-glycoprotein (Pgp) implemented and validated by the laboratories of the French Drug Resistance Network [Huet S, Marie JP, Gualde N, Robert J. Reference method for detection of Pgp mediated multidrug resistance in human hematological malignancies: a method validated by the laboratories of the French Drug Resistance Network. Cytometry 1998;34:248-56] in cells displaying low level of resistance. Fluoresceine-conjugated monoclonal antibodies (Mabs) and propidium iodide were respectively replaced by phycoerythrin-conjugated Mabs and Sytox green. The removal of erythrocytes and granulocytes by density gradient was replaced by the lysis of erythrocytes after Mab incubation. Using these conditions, Pgp could be detected in the K-H30 line, which was negative in former studies, with Mab/Control ratios increasing by 3.7- to 5.9-fold, and Mab/Control ratios in the parental sensitive K562 line still ranging between 0.8 and 1.2. When tested on 16 blood samples from patients presenting haematological malignancies, six samples presented low positivity, which was not detected with the former method, while 10 samples remained negative with the two methods. Pgp was specifically detected in pathological blood cells in the six positive samples.

Multiple drug resistance protein (MDR-1), multidrug resistance-related protein (MRP) and lung resistance protein (LRP) gene expression in childhood acute lymphoblastic leukemia

CONTEXT

Despite the advances in the cure rate for acute lymphoblastic leukemia, approximately 25% of affected children suffer relapses. Expression of genes for the multiple drug resistance protein (MDR-1), multidrug resistance-related protein (MRP), and lung resistance protein (LRP) may confer the phenotype of resistance to the treatment of neoplasias.

OBJECTIVE

To analyze the expression of the MDR-1, MRP and LRP genes in children with a diagnosis of acute lymphoblastic leukemia via the semiquantitative reverse transcription polymerase chain reaction (RT-PCR), and to determine the correlation between expression and event-free survival and clinical and laboratory variables.

DESIGN

A retrospective clinical study.

SETTING

Laboratory of Pediatric Oncology, Department of Pediatrics, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Brazil.

METHODS

Bone marrow aspirates from 30 children with a diagnosis of acute lymphoblastic leukemia were assessed for the expression of messenger RNA for the MDR-1, MRP and LRP genes by semi-quantitative RT-PCR.

RESULTS

In the three groups studied, only the increased expression of LRP was related to worsened event-free survival (p = 0.005). The presence of the common acute lymphoblastic leukemia antigen (CALLA) was correlated with increased LRP expression (p = 0.009) and increased risk of relapse or death (p = 0.05). The relative risk of relapse or death was six times higher among children with high LRP expression upon diagnosis (p = 0.05), as confirmed by multivariate analysis of the three genes studied (p = 0.035).

DISCUSSION

Cell resistance to drugs is a determinant of the response to chemotherapy and its detection via RT-PCR may be of clinical importance.

CONCLUSIONS

Evaluation of the expression of genes for resistance to antineoplastic drugs in childhood acute lymphoblastic leukemia upon diagnosis, and particularly the expression of the LRP gene, may be of clinical relevance, and should be the object of prospective studies.

Appraisal of the MTT-based assay as a useful tool for predicting drug chemosensitivity in leukemia

The MTT-based assay relies upon the cellular reduction of tetrazolium salts to their intensely colored formazans. The test is easy to perform in hematological malignancies and is adaptable for high throughput of samples, although there are some minor limitations in its application resulting from metabolic interference. This class of assays are highly accurate for predicting drug resistance, whereas their predictive value for drug sensitivity depends on the type of disease and drug or drug combination used. They have been found to predict clinical response to fludarabine FLD in B-CLL and were useful for predetermining clinical potential of a single drug or drug combination in AML patients. Extensive studies with ALL patients have supported their advantage for selecting effective drug treatment of the disease. To conclude, pretreatment chemosensitivity assays may help in the selection of chemotherapeutic drugs with the greatest likelihood for clinical effectiveness, and in the exclusion of uneffective therapy. This can lead to improved disease management, response, survival and use of financial resources.

P-glycoprotein and multidrug resistance-associated protein mediate specific patterns of multidrug resistance in malignant glioma cell lines, but not in primary glioma cells

Understanding and overcoming multidrug resistance (MDR) may be a promising strategy to develop more effective pharmacotherapies for malignant gliomas. In the present study, human malignant glioma cell lines (n=12) exhibited heterogeneous mRNA and protein expression and functional activity of the mdr gene-encoded P-glycoprotein (PGP) and MDR-associated protein (MRP). Correlation between mRNA expression, protein levels and functional activity was strong. Inhibition of PGP activity by verapamil or PSC 833 enhanced the cytotoxic effects of vincristine, doxorubicin, teniposide and taxol. Inhibition of MRP activity by indomethacin or probenecid enhanced the cytotoxic effects of vincristine, doxorubicin and teniposide. The human cerebral endothelial cell line, SV-HCEC, exhibited the strongest PGP activity of all cell lines. Five primary human glioblastomas and one anaplastic astrocytoma displayed heterogenous protein levels of PGP and MRP-1 in tumor cells and of PGP in biopsy specimens in vivo, but no functional activity of these proteins upon ex vivo culturing. These data suggest that the glioma cell line-associated MDR-type drug resistance is a result of long-term culturing and that cerebral endothelial, but not glioma cells, may contribute to MDR-type drug resistance of gliomas in vivo.

Doxorubicin-resistant, MRP1-expressing U-1285 cells are sensitive to idarubicin

A doxorubicin-resistant subline (U-1285dox(900)) was derived from the human small cell lung carcinoma cell line U-1285. U-1285dox(900) was exposed to a wide range of anticancer agents to determine its resistance profile. In contrast to U-1285 cells, the resistant subline U-1285dox(900) expressed elevated MRP1 mRNA detected by reversed transcriptase-polymerase chain reaction (RT-PCR) and MRP1 protein analyzed with Western blot. Neither MDR1 mRNA nor P-glycoprotein could be detected in the parental cell line or resistant subline. U-1285dox(900) exhibited high resistance to doxorubicin, epirubicin, daunorubicin, and vincristine, an intermediate resistance to mitoxantrone, and a low resistance to etoposide. A collateral sensitivity to cytosine arabinoside, chlorodeoxyadenosine, and melphalan was observed. The resistance could be reversed by buthionine-sulphoximine and verapamil for all tested drugs. Compared with daunorubicin, resistance to idarubicin was very low, 14-fold and 2.6-fold, respectively. This was associated with a higher accumulation due to a slower transport of idarubicin out of U-1285dox(900) cells.

Biology and modulation of multidrug resistance (MDR) in hematological malignancies

Drug resistance is one of the most significant impediments in the treatment of hematological malignancies. There have been a number of studies on the incidence of P-GP expression in tumor cells or tissues, where detectable level of P-GP has been found in all types of hematological malignancies. P-GP expression and significance in the patients varies widely between reported studies on patients with different ages and different disease types. Some of this validation can be accounted for by the threshold used to consider a sample positive for P-GP. However, mdr-1 is likely important in determining therapeutic outcome in patients with AML, NHL, and MM, although there is a suggestion of a different "behavior" between adult and childhood AML. In contrast, the significant prognostic association with expression of MRP and LRP is not consistent with disease types and disease stages. Clinical trials of modulation of MDR have been limited by following major factors. One is inability of achieving adequate blood levels of the modulator to reverse MDR, and the other is presence of other resistance mechanisms in addition to P-GP. The fact that P-GP modulators alter the pharmacokinetics of anti-cancer drugs can potentially increase toxicities if the dose of anticancer drugs is not appropriately reduced. Recently, MDR modulators such as valspodar have demonstrated substantial inhibition of P-GP. In this presentation, a number of characteristics in VCR-resistant cells are reported. We demonstrate that acquisition of MDR or recovery from MDR phenotypes differ in one cell type to another, a marked correlation between P-GP and susuceptibility to oxygen radicals, and altered gene expression of cell membrane antigen and apoptosis cascade genes. The efficacy of immunotherapies depends on the altered or unchanged target molecules of MDR cells. Thus, immunotherapies or reversal agents that aim at these substances in tumor cells should be useful to overcome MDR phenotypes.

P-glycoprotein (P-gp) is upregulated in peripheral T-cell subsets from solid organ transplant recipients

Immunosuppressive agents such as cyclosporine, tacrolimus, sirolimus, and corticosteroids are substrates for the transmembrane multidrug resistance pump P-glycoprotein (P-gp). Experience in oncologyhas suggested that chronic exposure to P-gp substrates induces upregulation of P-gp activity, which could result in resistance to immunosuppressive drugs. The authors investigated P-gp function in CD4+ and CD8+ T cells from the peripheral blood of solid organ transplant recipients (SOTX). Subjects included 14 stable SOTX (10 liver, 4 lung) and 16 healthy controls. Four-color flow cytometry was used to simultaneously measure intracellular concentration of the fluorescent P-gp substrate Rhodamine 123 (Rh123) and surface expression of CD45RO (nominal memory/effector), CD45RA (naive), and either CD4 or CD8. P-glycoprotein function was measured by a dye efflux assay in which activity was inferred from a decrease in Rh123 fluorescence. CD4+ and CD8+ T cells from patients and control subjects eliminated Rh123, and this activity was inhibited by verapamil, a known P-gp substrate. CD8+ T cells had greater P-gp activity than CD4+ cells, and naive and transitional T cells displayed greater activity than memory T cells. Activity was bimodal in CD8+ CD45RO+ T cells, with a subset of these cells expressing the greatest P-gp activity. Patient CD8+ naive and transitional T cells had upregulated P-gp activity compared to control subjects. We conclude that (1) P-gp activityis significantly upregulated in specific T-cell subsets (CD8+/CD45RA+) in the peripheral blood of SOTX, and (2) the bimodal nature of P-gp response in CD8+ T cells complicates analysis of the effect of chronic administration of P-gp substrates to SOTX.

Reversion of multidrug resistance by co-encapsulation of doxorubicin and cyclosporin A in polyalkylcyanoacrylate nanoparticles

Individual and combined polyalkylcyanoacrylate nanoparticle formulation of cyclosporin A and doxorubicin were prepared and evaluated in an attempt to show improved growth inhibition efficacy in a resistant cell culture line. The drug loaded nanoparticles were prepared using the well established emulsion polymerization process without using any modification for the hydrophilic doxorubicin drug whereas the incorporation of cyclosporin A needed to wait a moment after the polymerization reaction started. This was necessary to avoid cyclosporin A precipitation and polymer aggregation. Cyclosporin A release from the nanoparticles was rapid probably because the drug was adsorbed onto the nanoparticles surface rather than embedded into the polymeric core. Doxorubicin displayed also a burst effect but with a slower second phase probably related with the nanoparticles bioerosion rate owing to its entrapment in the polymeric network. Finally, it was shown in resistant cell culture experiments that the association of both cyclosporin A and doxorubicin within a single nanoparticle formulation elicited the most effective growth rate inhibition as compared to other combinations of both drugs while using a lower amount of polymer compared to separated nanoparticle formulations. This result was probably due to the synergistic effect achieved by combining the chemo-sensitizing compound cyclosporin A, with an effective cytotoxic drug like doxorubicin.

Ability of doxorubicin-loaded nanoparticles to overcome multidrug resistance of tumor cells after their capture by macrophages

PURPOSE

Investigation of the ability of doxorubicin-loaded nanoparticles (NP/Dox) to overcome multidrug resistance (MDR) when they have first been taken up by macrophages.

METHODS

The growth inhibition of P388 sensitive (P388) and resistant (P388/ADR) tumor cells was evaluated in a coculture system consisting of wells with two compartments. The tumor cells were seeded into the lower compartment, the macrophages were introduced into the upper part in which the drug preparations were also added.

RESULTS

Doxorubicin exerted lower cytotoxicity on tumor cells in coculture compared with direct contact. In P388/ADR, NP/Dox cytotoxicity was far higher than that of free doxorubicin (Dox). Three different formulations of cyclosporin A (either free (CyA), loaded to nanoparticles (NP/CyA) or in a combined formulation with doxorubicin (NP/Dox-CyA)), were added to modulate doxorubicin efficacy. The addition of cyclosporin A to Dox increased drug cytotoxicity. Both CyA added to NP/Dox and NP/Dox-CyA were able to bypass drug resistance.

CONCLUSIONS

Despite the barrier role of macrophages, NP/Dox remained far more cytotoxic than Dox against P388/ADR. Both NP/Dox + CyA and NP/Dox-CyA allowed to overcome MDR, but the last one should present greater advantage in vivo by confining both drugs in the same compartment, hence reducing the adverse effects.

Different expression of glutathione S-transferase alpha, mu and pi in childhood acute lymphoblastic and myeloid leukaemia

Expression of three major classes of glutathione S-transferases (GSTs), i.e. alpha, mu and pi class, P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) were studied in childhood acute lymphoblastic leukaemia (ALL), acute myeloid leukaemia (AML) and normal peripheral blood lymphocytes by flow cytometry. In vitro cytotoxicity of 4-hydroxy-ifosfamide (IFOS), daunorubicin (DNR) and prednisolone (PRED) was assessed by the MTT assay. Expression of alpha, mu and pi class GST did not significantly differ between leukaemic cells from 100 initial and 14 unrelated relapse ALL patients (GSTalpha P=026; GSTmu P=O009; GSTpi P=0.13). The expression of GSTalpha (1.4-fold, P=0.0004), GSTpi (13-fold, P = 0001) and to a lesser extent also GSTmu (1.1-fold, P=0.03) was higher in ALL compared with normal peripheral blood lymphocytes. Expression of GSTmu and GST7pi was significantly higher in 18 AML compared with 100 ALL patients at initial diagnosis (respectively 1.3-fold, P=0.0005 and 2-fold, P<0.0001). In contrast, GSTalpha was median 2-fold lower expressed in the AML samples (P< 0.0001). Expression levels of alpha, mu and pi class GSTs were not related to the degree of resistance to IFOS, DNR and PRED nor to immunophenotype, white blood cell count or age at presentation of childhood ALL. One exception was a remarkably low expression of GSTalpha in IFOS-sensitive samples compared with a heterogenous expression in IFOS-resistant samples (P= 0.02). Expression of GSTpi, but not of GSTalpha or GSTmu, weakly correlated with the expression of MRP (Rs 0.36, P = 0.002, n = 74) but not with P-gp. However, a high expression of both GSTpi and MRP was not associated with in vitro resistance to IFOS, DNR or PRED. The present data suggest that expression of GSTs is not linked to the degree of resistance to IFOS, DNR and PRED or clinical risk factors in childhood ALL. Whether the high expression of GSTmu and GSTpi in AML cells contributes to the relative resistance to IFOS, DNR and PRED compared with ALL samples (P < or = 0.0001) warrants further study.