Role of P-glycoprotein in evolution of populations of chronic myeloid leukemia cells treated with imatinib

Novel pharmacological approach for the prevention of multidrug resistance (MDR) in a human leukemia cell line

BACKGROUND

Drug resistance mechanisms are the regulatory factors associated with drug metabolism and drug transport to inward and outward of the target cells. Maybridge fragment (MBF) library is a collection of pharmacophore rich compounds having affinity with membrane transporters. This study has been designed to evaluate the efficacy of MBFs in overcoming the leukemic cells' resistance to imatinib.

METHODS

Imatinib resistant cells (K562-R) were prepared using myelogenous leukemia cell line (K562) by titration method. The four MBFs were prioritized for determining their effect on imatinib resistance. The cells were treated with imatinib and MBFs and the MTT assay was performed to evaluate the efficacy of MBFs in enhancing the imatinib mediated cell death. The transcript levels of Bcr-Abl1 gene and efflux transporter genes were determined by RT-qPCR analysis.

RESULTS

The MBFs enhanced the imatinib mediated cell death of K562-R cells. There was also a significant decrease in the mRNA levels of the major drug efflux genes (ABCB1, ABCB10, ABCC1 and ABCG2) when treated with a combination of imatinib and MBF in comparison to imatinib treatment alone.

CONCLUSION

The drug efflux is one of the mechanisms of multidrug resistance in cancer cells and the MBFs used in this study were all found to significantly overcome the imatinib resistance by limiting the expression of efflux genes. This study, therefore, highlights the potential of Maybridge compounds in treating the drug resistant leukemia.

Longer Hydroxyurea Administration Prior to Imatinib Mesylate is Risk Factor for Unsuccessful Major Molecular Response in Chronic-Phase Chronic Myeloid Leukemia: Possibility of P-Glycoprotein Role

Objective:

This study aimed to identify the association between duration of HU administration prior to IM treatment and MMR achievement in chronic-phase CML while evaluating the role of MDA, HIF-1α and P-gp.

Methods:

The study was conducted at Dr. Cipto Mangunkusumo National General Hospital and Dharmais Cancer Hospital, Jakarta using retrospective cohort design to analyse the association between the duration of HU before IM and its MMR achievement and cross-sectional design to analyse the association between MDA, HIF-1α and P-gp expressions with MMR achievement. Main subjects were chronic-phase CML patients treated by HU prior to IM for ≥ 12 months and HU only. The subjects were divided into four main groups: (1) chronic-phase CML patients treated with HU ≤ 6 months + IM ≥ 12 months and (2) HU > 6 months + IM ≥ 12 months (3) HU only (≤ 6 months), (4) HU only ( >6 months). Subjects were obtained from January 2015 to May 2016. Data were gathered through history taking, physical examination, medical record evaluation, and blood sample analysis. Bivariate analysis was conducted using chi square, independent T-test, and Mann-Whitney according to the variables.

Results:

Administration of HU for more than 6 months prior to IM was associated with unsuccessful MMR achievement (RR 1.60; 95%CI 1.29-2.00). MDA level, HIF-1α, P-glycoprotein expression were not associated with MMR achievement but the mean MDA level (0.63±0.31 vs 0.75±0.41 p=0.461) and median P-glycoprotein expressions {16,92 (0,04 – 43,86) vs. 5,15 (0,02–39,64); p=0.311} were found to be higher in patients receiving HU for > 6 months group than in HU ≤ 6 months group consecutively.

Conclusion:

Administration of HU for more than 6 months prior to IM was associated with unsuccessful MMR achievement in chronic-phase CML. The study suggested that P-glycoprotein overexpression as the predictor for unsuccessful MMR achievement.

Hyaluronated imatinib liposomes with hybrid approach to target CD44 and P-gp overexpressing MDR cancer: an in-vitro, in-vivo and mechanistic investigation

Multi Drug Resistance (MDR) of cancer cells is a constant threat to the clinically used drugs as well as new drug development. In present work, we aimed to assess in-vitro as well as in-vivo efficacy of the developed Imatinib loaded liposomes in MDR cancer. An array of tests was also carried out to comprehensively understand the bio-mechanism that enable these nanocarriers to modulate P-gp activity. Hyaluronic acid coated, Imatinib mesylate containing lipsomes (HA-LIPO-IM) were analysed through in-vitro and in-vivo studies in MDR cancer cells and tumour models. Effect of developed hyaluronated liposomes on various biomolecular mechanisms was also evaluated. Around 3.5 times lower IC₅₀ for HA-LIPO-IM in comparison to drug solution in HT-29 and Colo-320 cells proved the enhanced action of the drug in MDR cells. HA-LIPO formulations were demonstrated to have inhibitory effect on ATPase enzyme. Molecular masking of Imatinib mesylate and CD-44 mediated endocytosis were also found responsible for anti-MDR effect. In-vivo studies revealed the prolonged tumour accumulation and 4-fold increase in tumour regression efficacy of HA-LIPO-IM in comparison to free drug solution. The work demonstrated the target specific accumulation of HA-LIPO-IM in CD-44 overexpressing cancer cells through P-gp modulation.

Concise Review: Chronic Myeloid Leukemia: Stem Cell Niche and Response to Pharmacologic Treatment

Nowadays, more than 90% of patients affected by chronic myeloid leukemia (CML) survive with a good quality of life, thanks to the clinical efficacy of tyrosine kinase inhibitors (TKIs). Nevertheless, point mutations of the ABL1 pocket occurring during treatment may reduce binding of TKIs, being responsible of about 20% of cases of resistance among CML patients. In addition, the presence of leukemic stem cells (LSCs) represents the most important event in leukemia progression related to TKI resistance. LSCs express stem cell markers, including active efflux pumps and genetic and epigenetic alterations together with deregulated cell signaling pathways involved in self-renewal, such as Wnt/β-catenin, Notch, and Hedgehog. Moreover, the interaction with the bone marrow microenvironment, also known as hematopoietic niche, may influence the phenotype of surrounding cells, which evade mechanisms controlling cell proliferation and are less sensitive or frankly resistant to TKIs. This Review focuses on the role of LSCs and stem cell niche in relation to response to pharmacological treatments. A literature search from PubMed database was performed until April 30, 2017, and it has been analyzed according to keywords such as chronic myeloid leukemia, stem cell, leukemic stem cells, hematopoietic niche, tyrosine kinase inhibitors, and drug resistance. Stem Cells Translational Medicine 2018;7:305-314.

Towards Comprehension of the ABCB1/P-Glycoprotein Role in Chronic Myeloid Leukemia

Abstract: The introduction of imatinib (IM), a BCR-ABL1 tyrosine kinase inhibitor (TKI), has represented a significant advance in the first-line treatment of chronic myeloid leukemia (CML). However, approximately 30% of patients need to discontinue IM due to resistance or intolerance to this drug. Both resistance and intolerance have also been observed in treatment with the second-generation TKIs-dasatinib, nilotinib, and bosutinib-and the third-generation TKI-ponatinib. The mechanisms of resistance to TKIs may be BCR-ABL1-dependent and/or BCR-ABL1-independent. Although the role of efflux pump P-glycoprotein (Pgp), codified by the ABCB1 gene, is unquestionable in drug resistance of many neoplasms, a longstanding question exists about whether Pgp has a firm implication in TKI resistance in the clinical scenario. The goal of this review is to offer an overview of ABCB1/Pgp expression/activity/polymorphisms in CML. Understanding how interactions, associations, or cooperation between Pgp and other molecules-such as inhibitor apoptosis proteins, microRNAs, or microvesicles-impact IM resistance risk may be critical in evaluating the response to TKIs in CML patients. In addition, new non-TKI compounds may be necessary in order to overcome the resistance mediated by Pgp in CML.

Problems of Glioblastoma Multiforme Drug Resistance

Glioblastoma multiforme (GBL) is the most common and aggressive brain neoplasm. A standard therapeutic approach for GBL involves combination therapy consisting of surgery, radiotherapy, and chemotherapy. The latter is based on temozolomide (TMZ). However, even by applying such a radical treatment strategy, the mean patient survival time is only 14.6 months. Here we review the molecular mechanisms underlying the resistance of GBL cells to TMZ including genetic and epigenetic mechanisms. Present data regarding a role for genes and proteins MGMT, IDH1/2, YB-1, MELK, MVP/LRP, MDR1 (ABCB1), and genes encoding other ABC transporters as well as Akt3 kinase in developing resistance of GBL to TMZ are discussed. Some epigenetic regulators of resistance to TMZ such as microRNA and EZH2 are reviewed.

MRP1 and P-glycoprotein expression assays would be useful in the additional detection of treatment non-responders in CML patients without ABL1 mutation

We evaluated the ability of the rhodamine-123 efflux assay, multidrug resistance-associated protein-1 (MRP1) expression assay and P-glycoprotein (Pgp) expression assay to discriminate chronic myelogenous leukemia (CML) patients who had failed treatment or were at risk of failure. Each assay was performed in blood samples from CML patients (n=224) treated with tyrosine kinase inhibitors, taken at diagnosis (n=14) and follow-up (n=210). Patient samples were categorized as optimal response (n=120), suboptimal response (n=54), and treatment failure (n=36). Treatment-failed patients had a significantly higher MRP1 expression (5.24% vs. 3.54%, P=0.006) and Pgp expression (5.25% vs. 3.48%, P=0.005) than responders. Both MRP1 (%) and Pgp (%) were highly specific (95.2% and 94.5%) and relatively accurate (83.0% and 82.5%) in the detection of treatment non-responders. Of treatment-failed patients, 41.2% had a positive result in at least one assay and of these patients without ABL1 kinase domain mutation, 51.9% were positive in at least one assay. However, the rhodamine-123 efflux assay failed to discriminate two patient groups. Thus, both MRP1 and Pgp expression assays could be useful for additional identification of treatment non-responders in CML patients without ABL1 mutation.

Mechanisms of resistance to BCR-ABL TKIs and the therapeutic strategies: A review

BCR-ABL caused by the translocation of t(9,22) with elevated tyrosine-kinase activity could induce leukemia in mice, which established BCR-ABL as the molecular pathogenic event in CML (Chronic myeloid leukemia). In recent years, a variety of tyrosine kinase inhibitors (TKIs) targeting at BCR-ABL specifically and effectively have been developed, which has fundamentally promoted the treatment of CML. However, the efficacy of TKIs was limited by its resistance induced by the development of kinase domain mutations and other mechanisms illustrated. In this review, we summarized BCR-ABL inhibitors approved by Food and Drug Administration (FAD), with the same concerns focus on the resistant mechanisms of BCR-ABL inhibitors and therapeutic resistant strategies.

ABCB1 regulation through LRPPRC is influenced by the methylation status of the GC -100 box in its promoter

One of the potential mechanisms of imatinib mesylate (IM) resistance in chronic myeloid leukemia (CML) is increased level of P-glycoprotein (Pgp). Pgp is an efflux pump capable of activating the multidrug resistance (MDR) phenotype. The gene encoding Pgp (ABCB1) has several binding sites in its promoter region, along with CpG islands and GC boxes, involved in its epigenetic control. In previous work, we performed a proteomic study to identify proteins involved in IM cross-resistance in acute leukemia. Among these proteins, we identified LRPPRC as a potential regulator of ABCB1 transcription via an invMED1 binding site in ABCB1. Interestingly, this invMED1 binding site overlaps with the GC -100 box. In this work, we investigated the potential role of LRPPRC in the regulation of ABCB1 transcriptional activity in CML resistance. In addition, we evaluated the potential connection between this regulation and the methylation status of the ABCB1 promoter in its GC -100 box. Our results show that LRPPRC binds prominently to the ABCB1 promoter in Lucena cells, an IM-resistant cell line. Luciferase assays showed that ABCB1 transcription is positively regulated by LRPPRC upon its knockdown. Pyrosequencing analysis showed that the ABCB1 promoter is differentially methylated at its GC -100 box in K562 cells compared with Lucena cells, and in CML patients with different response to IM. Chromatin immunoprecipitation and Pgp expression after DNA demethylation treatment showed that LRPPRC binding is affected by the methylation status of ABCB1 GC -100 box. Taken together, our findings indicate that LRPPRC is a transcription factor related to ABCB1 expression and highlight the importance of epigenetic regulation in CML resistance.

Reduced ABCG2 and increased SLC22A1 mRNA expression are associated with imatinib response in chronic myeloid leukemia

Imatinib mesylate (IM) has become a standard of care in chronic myeloid leukemia (CML) therapy. Single nucleotide polymorphisms (SNPs) and altered expression in drug transporter genes may influence IM response. In order to investigate whether mRNA expression and SNPs in drug transporters are associated with IM resistance, we studied 118 chronic-phase CML patients receiving the standard dose of IM (400 mg/day). They were assigned as responders and non-responders according to European LeukemiaNet criteria (2009). mRNA expression in samples at diagnosis (without IM therapy) and outcomes after IM failure were also evaluated in subgroups of patients. Major molecular response (MMR), complete molecular response and primary and secondary resistance were all assessed. BCR-ABL1, ABCB1, ABCG2, SLC22A1 and SLCO1A2 mRNA expression and SNPs in ABCG2 and SLC22A1 genes were analyzed. ABCG2 mRNA expression in the non-responders was higher before and during IM therapy. Furthermore, ABCG2 was overexpressed in those who did not achieve MMR (P=0.027). In a subgroup of patients who switched to second-generation tyrosine kinase inhibitors, high mRNA expression of ABCG2 was associated with a risk of 24 times that of not achieving complete cytogenetic response (OR 24.00, 95% CI 1.74-330.80; P=0.018). In the responder group, patients who achieved MMR (P=0.009) presented higher mRNA levels of SLC22A1. The SNPs were not associated with mRNA expression of ABCG2 and SLC22A1. Our data suggest that elevated ABCG2 expression (an efflux transporter) could be associated with IM resistance and could impact on second-generation TKI response, whereas high SLC22A1 expression (an influx transporter) may be associated with a successful IM therapy in CML patients.

Multidrug resistance in chronic myeloid leukaemia: how much can we learn from MDR-CML cell lines?

The hallmark of CML (chronic myeloid leukaemia) is the BCR (breakpoint cluster region)-ABL fusion gene. CML evolves through three phases, based on both clinical and pathological features: a chronic phase, an accelerated phase and blast crisis. TKI (tyrosine kinase inhibitors) are the treatment modality for patients with chronic phase CML. The therapeutic potential of the TKI imatinib is affected by BCR-ABL dependent an independent mechanisms. Development of MDR (multidrug resistance) contributes to the overall clinical resistance. MDR involves overexpression of ABC -transporters (ATP-binding-cassette transporter) among other features. MDR studies include the analysis of cancer cell lines selected for resistance. CML blast crisis is accompanied by increased resistance to apoptosis. This work reviews the role played by the influx transporter OCT1 (organic cation transporter 1), by efflux ABC transporters, molecules involved in the modulation of apoptosis (p53, Bcl-2 family, CD95, IAPs (inhibitors of apoptosis protein)], Hh and Wnt/β-catenin pathways, cytoskeleton abnormalities and other features described in leukaemic cells of clinical samples and CML cell lines. An MDR cell line, Lucena-1, generated from K562 by stepwise exposure to vincristine, was used as our model and some potential anticancer drugs effective against the MDR cell line and patients' samples are presented.

XIAP and P-glycoprotein co-expression is related to imatinib resistance in chronic myeloid leukemia cells

P-glycoprotein (Pgp) and XIAP co-expression has been discussed in the process of the acquisition of multidrug resistance (MDR) in cancer. Here, we evaluated XIAP and Pgp expression in chronic myeloid leukemia (CML) samples, showing a positive correlation between them. Furthermore, we evaluated the effects of imatinib in XIAP and Pgp expression using CML cell lines K562 (Pgp(-)) and K562-Lucena (Pgp(+)). Imatinib increased XIAP and Pgp expression in K562-Lucena cells, while in K562 cells a downregulation of these proteins was observed, suggesting that imatinib induces an increment of MDR phenotype of CML cells that previously exhibit high levels of Pgp/XIAP co-expression.

Imatinib increases apoptosis index through modulation of survivin subcellular localization in the blast phase of CML cells

Using MTT, Annexin V/flow cytometry, immunocytochemistry, subcellular fractionation, and Western blotting assays we analyzed the effect of imatinib in two blast phase of chronic myeloid leukemia (CML) cell lines: K562 P-glycoprotein (Pgp)-negative, and Lucena, Pgp-positive. In K562 cell line, the high apoptosis index induced by imatinib was associated with the survivin predominantly in the nucleus. In the Lucena cell line, the low apoptosis index induced by imatinib was associated with a cytoplasmatic survivin localization. Pgp and survivin might be subject to the same molecular regulation, and therefore represent a therapeutic target in the blast phase of CML.

Wnt/β-catenin pathway regulates ABCB1 transcription in chronic myeloid leukemia

BACKGROUND

The advanced phases of chronic myeloid leukemia (CML) are known to be more resistant to therapy. This resistance has been associated with the overexpression of ABCB1, which gives rise to the multidrug resistance (MDR) phenomenon. MDR is characterized by resistance to nonrelated drugs, and P-glycoprotein (encoded by ABCB1) has been implicated as the major cause of its emergence. Wnt signaling has been demonstrated to be important in several aspects of CML. Recently, Wnt signaling was linked to ABCB1 regulation through its canonical pathway, which is mediated by β-catenin, in other types of cancer. In this study, we investigated the involvement of the Wnt/β-catenin pathway in the regulation of ABCB1 transcription in CML, as the basal promoter of ABCB1 has several β-catenin binding sites. β-catenin is the mediator of canonical Wnt signaling, which is important for CML progression.

METHODS

In this work we used the K562 cell line and its derived MDR-resistant cell line Lucena (K562/VCR) as CML study models. Real time PCR (RT-qPCR), electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation (ChIP), flow cytometry (FACS), western blot, immunofluorescence, RNA knockdown (siRNA) and Luciferase reporter approaches were used.

RESULTS

β-catenin was present in the protein complex on the basal promoter of ABCB1 in both cell lines in vitro, but its binding was more pronounced in the resistant cell line in vivo. Lucena cells also exhibited higher β-catenin levels compared to its parental cell line. Wnt1 and β-catenin depletion and overexpression of nuclear β-catenin, together with TCF binding sites activation demonstrated that ABCB1 is positively regulated by the canonical pathway of Wnt signaling.

CONCLUSIONS

These results suggest, for the first time, that the Wnt/β-catenin pathway regulates ABCB1 in CML.

The Interface between BCR-ABL-Dependent and -Independent Resistance Signaling Pathways in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is a clonal hematopoietic disorder characterized by the presence of the Philadelphia chromosome which resulted from the reciprocal translocation between chromosomes 9 and 22. The pathogenesis of CML involves the constitutive activation of the BCR-ABL tyrosine kinase, which governs malignant disease by activating multiple signal transduction pathways. The BCR-ABL kinase inhibitor, imatinib, is the front-line treatment for CML, but the emergence of imatinib resistance and other tyrosine kinase inhibitors (TKIs) has called attention for additional resistance mechanisms and has led to the search for alternative drug treatments. In this paper, we discuss our current understanding of mechanisms, related or unrelated to BCR-ABL, which have been shown to account for chemoresistance and treatment failure. We focus on the potential role of the influx and efflux transporters, the inhibitor of apoptosis proteins, and transcription factor-mediated signals as feasible molecular targets to overcome the development of TKIs resistance in CML.

Influence of proteasome inhibitor bortezomib on the expression of multidrug resistance genes and Akt kinase activity

The goal of this work was to study the mechanisms of ABC family transport proteins' regulation by a new-generation antitumor drug - the proteasome inhibitor bortezomib (Velcade). ABC transporters determine the multidrug resistance of tumor cells (MDR). We confirmed our previously discovered observation that bortezomib affects the expression of genes involved in the formation of MDR (ABCB1 gene, also known as MDR1, and ABCC1-MRP1), reducing the amount of their mRNA. This effect was found to depend on Akt kinase activity: the Akt activity inhibitor Ly 294002 increased the amount of MRP1 mRNA in KB 8-5 cells. It was also shown that bortezomib increased the amount of Akt kinase phosphorylated form in cell lines of malignant cells KB 8-5 and K 562/i-S9 that overexpressed ABCB1 transporter (Pgp), and did not affect the amount of activated Akt in the corresponding wild-type cells. When exposed to bortezomib, selection of resistant to it cell variants was much faster for a Pgp-overexpressing cell population (compared to wild-type cells). It is shown that bortezomib affects the amount of MRP1 gene mRNA, relocating the multifunctional protein YB-1, dependent on Akt activity, from cytoplasm to nuclei of MCF-7 breast cancer cells. The data indicate that the transcriptional activity of YB-1 might be one of the mechanisms that determine the effect of bortezomib on the amount of MRP1 gene mRNA.

Variation of MDR proteins expression and activity levels according to clinical status and evolution of CML patients

The involvement of the multidrug resistance (MDR) mediated by ABC transporter proteins P-glycoprotein (Pgp) and multidrug resistance-associated protein-1 (MRP1) overexpressions in patients with chronic myeloid leukemia (CML) are not completely understood. Pgp and MRP1 expressions and activity were analyzed in samples from 158 patients with chronic myeloid leukemia (CML). Using flow cytometry, Pgp expression was more frequently observed in early chronic (P = 0.00) and in advanced (P = 0.02) CML phases when it was compared to MRP1 expression. Variation of MDR expression and activity were observed during the CML evolution in patients previously treated with interferon and imatinib. In the K562-Lucena cell line, Pgp positive, imatinib caused an enhancing in Pgp expression at protein and mRNA levels, whereas in the Pgp negative cell line, this drug was capable of decreasing MDR1/Pgp mRNA levels. Our result emphasizes the importance of understanding the different aspects of MDR status in patients with CML when they are under investigation in determining imatinib resistance.

Improvement of tumor targeting and antitumor activity by a disulphide bond stabilized diabody expressed in Escherichia coli

We have generated an anti-Pgp/anti-CD3 diabody which can effectively inhibit the growth of multidrug-resistant human tumors. However, the two chains of the diabody are associated non-covalently and are therefore capable of dissociation. Cysteine residues were introduced into the V-domains to promote disulphide cross-linking of the dimer as secreted by Escherichia coli. Compared with the parent diabody, the ds-Diabody obtained was more stable in human serum at 37 degrees C, without loss of affinity or cytotoxicity activity in vitro. Furthermore, the ds-Diabody showed improved tumor localization and a twofold improved antitumor activity over the parent diabody in nude mice bearing Pgp-overexpressing K562/A02 xenografts. Our data demonstrate that ds-Diabody may be more useful in therapeutic applications than the parent diabody.

Transport proteins of the ABC family and multidrug resistance of tumor cells

Some new data concerning the role of transport proteins of the ABC family in multidrug resistance (MDR) of human tumor cells, and problems connected with regulation of these proteins are considered. MDR is a complex phenomenon that may be caused simultaneously by several mechanisms functioning in one and the same cell. Among them there may be the alterations of activity of several transport proteins. Activation of these proteins may be associated with alterations of activities of different cell protective systems and of the signal transduction pathways involved in regulation of proliferation, differentiation, and apoptosis. Clinical significance of multifactor MDR is discussed.