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

Amsacrine downregulates BCL2L1 expression and triggers apoptosis in human chronic myeloid leukemia cells through the SIDT2/NOX4/ERK/HuR pathway

Accumulating evidence indicates that the anticancer activity of acridine derivatives is mediated through the regulation of anti-apoptotic and pro-apoptotic BCL2 protein expression. Therefore, we investigated whether the cytotoxicity of amsacrine with an acridine structural scaffold in human chronic myeloid leukemia (CML) K562 cells was mediated by BCL2 family proteins. Amsacrine induced apoptosis, mitochondrial depolarization, and BCL2L1 (also known as BCL-XL) downregulation in K562 cells. BCL2L1 overexpression inhibited amsacrine-induced cell death and mitochondrial depolarization. Amsacrine treatment triggered SIDT2-mediated miR-25 downregulation, leading to increased NOX4-mediated ROS production. ROS-mediated inactivation of ERK triggered miR-22 expression, leading to increased HuR mRNA decay. As HuR is involved in stabilizing BCL2L1 mRNA, downregulation of BCL2L1 was noted in K562 cells after amsacrine treatment. In contrast, amsacrine-induced BCL2L1 downregulation was alleviated by restoring ERK phosphorylation and HuR expression. Altogether, the results of this study suggest that amsacrine triggers apoptosis in K562 cells by inhibiting BCL2L1 expression through the SIDT2/NOX4/ERK-mediated downregulation of HuR. Furthermore, a similar pathway also explains the cytotoxicity of amsacrine in CML MEG-01 and KU812 cells.

Expression of thimet oligopeptidase (THOP) modulated by oxidative stress in human multidrug resistant (MDR) leukemia cells

Thimet oligopeptidase (THOP) is a cytosolic metallopeptidase known to regulate the fate of post-proteasomal peptides, protein turnover and peptide selection in the antigen presentation machinery (APM) system. Oxidative stress influences THOP expression and regulates its proteolytic activity, generating variable cytosolic peptide levels, possibly affecting the immune evasion of tumor cells. In the present work, we examined the association between THOP expression/activity and stress oxidative resistance in human leukemia cells using the K562 cell line, a chronic myeloid leukemia (CML), and the multidrug-resistant (MDR) Lucena 1 (K562-derived MDR cell line) as model. The Lucena 1 phenotype was validated under vincristine treatment and the relative THOP1 mRNA levels and protein expression compared to K562 cell line. Our data demonstrated increased THOP1 gene and protein levels in K562 cells in contrast to the oxidative-resistant Lucena 1, even after H2O2 treatment, suggesting an oxidative stress dependence in THOP regulation. Further, it was observed higher basal levels of reactive oxygen species (ROS) in K562 compared to Lucena 1 cell line using DHE fluorescent probe. Since THOP activity is dependent on its oligomeric state, we also compared its proteolytic activity under reducing agent treatment, which demonstrated that its function modulation with respect to changes in redox state. Finally, the mRNA expression and FACS analyses demonstrated a reduced expression of MHC I only in K562 cell line. In conclusion, our results highlight THOP redox modulation, which could influence antigen presentation in multidrug resistant leukemia cells.

Drug Resistance: The Role of Exosomal miRNA in the Microenvironment of Hematopoietic Tumors

Extracellular vesicles (EVs), including exosomes, have an important role thanks to their ability to communicate and exchange information between tumor cells and the tumor microenvironment (TME), and have also been associated with communicating anti-cancer drug resistance (DR). The increase in proliferation of cancer cells alters oxygen levels, which causes hypoxia and results in a release of exosomes by the cancer cells. In this review, the results of studies examining the role of exosomal miRNA in DR, and their mechanism, are discussed in detail in hematological tumors: leukemia, lymphoma, and multiple myeloma. In conclusion, we underline the exosome's function as a possible drug delivery vehicle by understanding its cargo. Engineered exosomes can be used to be more specific for personalized therapy.

Genome‑wide expression and methylation analyses reveal aberrant cell adhesion signaling in tyrosine kinase inhibitor‑resistant CML cells

Although chronic myeloid leukemia (CML) can be effectively treated using BCR-ABL1 kinase inhibitors, resistance due to kinase alterations or to BCR-ABL1 independent mechanisms remain a therapeutic challenge. For the latter, the underlying mechanisms are widely discussed; for instance, gene expression changes, epigenetic factors and alternative signaling pathway activation. In the present study, in vitro-CML cell models of resistance against the tyrosine kinase inhibitors (TKIs) imatinib (0.5 and 2 µM) and nilotinib (0.1 µM) with biological replicates were generated to identify novel mechanisms of resistance. Subsequently, genome-wide mRNA expression and DNA methylation were analyzed. While mRNA expression patterns differed largely between biological replicates, there was an overlap of 71 genes differentially expressed between cells resistant against imatinib or nilotinib. Moreover, all TKI resistant cell lines demonstrated a slight hypermethylation compared with native cells. In a combined analysis of 151 genes differentially expressed in the biological replicates of imatinib resistance, cell adhesion signaling, in particular the cellular matrix protein fibronectin 1 (FN1), was significantly dysregulated. This gene was also downregulated in nilotinib resistance. Further analyses showed significant FN1-downregulation in imatinib resistance on mRNA (P<0.001) and protein level (P<0.001). SiRNA-mediated FN1-knockdown in native cells reduced cell adhesion (P=0.02), decreased imatinib susceptibility visible by higher Ki-67 expression (1.5-fold, P=0.04) and increased cell number (1.5-fold, P=0.03). Vice versa, recovery of FN1-expression in imatinib resistant cells was sufficient to partially restore the response to imatinib. Overall, these results suggested a role of cell adhesion signaling and fibronectin 1 in TKI resistant CML and a potential target for novel strategies in treatment of resistant CML.

Detachment of Hexokinase II From Mitochondria Promotes Collateral Sensitivity in Multidrug Resistant Chronic Myeloid Leukemia Cells

Chronic Myeloid Leukemia is a neoplastic disease characterized by the abnormal expansion of hematopoietic cells with compromised functions. Leukemic cells often display a multidrug resistance phenotype, enabling them to evade a number of structurally unrelated cytotoxic compounds. One of those mechanisms relies on the high expression of efflux transporters, such as the ABC proteins, whose activity depends on the hydrolysis of ATP to reduce intracellular drug accumulation. In the present work, we employed a well-known erythroleukemia cell line, K562, and a multidrug resistant derivative cell, FEPS, to evaluate how hexokinase II, a key regulator for the rate-limiting step glycolysis, contributes to the establishment of the multidrug resistance phenotype. We found that multidrug resistant cells primarily resort to glycolysis to generate ATP. Clotrimazole reduced the expression of mitochondrial hexokinase II, which destabilized bioenergetic parameters such as reactive oxygen species production, ATP, and glutathione levels on multidrug resistant cells. This impaired the activity of ABCC1, leading to increased drug accumulation and cell death. In summary, we propose that decoupling of hexokinase II from the mitochondria emerges as a promising strategy to generate collateral sensitivity and aid in the management of chronic myeloid leukemia in chemotherapy-refractory patients.

Pharmacogenomics of Impaired Tyrosine Kinase Inhibitor Response: Lessons Learned From Chronic Myelogenous Leukemia

The use of small molecules became one key cornerstone of targeted anti-cancer therapy. Among them, tyrosine kinase inhibitors (TKIs) are especially important, as they were the first molecules to proof the concept of targeted anti-cancer treatment. Since 2001, TKIs can be successfully used to treat chronic myelogenous leukemia (CML). CML is a hematologic neoplasm, predominantly caused by reciprocal translocation t(9;22)(q34;q11) leading to formation of the so-called BCR-ABL1 fusion gene. By binding to the BCR-ABL1 kinase and inhibition of downstream target phosphorylation, TKIs, such as imatinib or nilotinib, can be used as single agents to treat CML patients resulting in 80 % 10-year survival rates. However, treatment failure can be observed in 20-25 % of CML patients occurring either dependent or independent from the BCR-ABL1 kinase. Here, we review approved TKIs that are indicated for the treatment of CML, their side effects and limitations. We point out mechanisms of TKI resistance focusing either on BCR-ABL1-dependent mechanisms by summarizing the clinically observed BCR-ABL1-mutations and their implications on TKI binding, as well as on BCR-ABL1-independent mechanisms of resistances. For the latter, we discuss potential mechanisms, among them cytochrome P450 implications, drug efflux transporter variants and expression, microRNA deregulation, as well as the role of alternative signaling pathways. Further, we give insights on how TKI resistance could be analyzed and what could be learned from studying TKI resistance in CML in vitro.

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.

Analysis of ceRNA networks and identification of potential drug targets for drug-resistant leukemia cell K562/ADR

Background

Drug resistance is the main obstacle in the treatment of leukemia. As a member of the competitive endogenous RNA (ceRNA) mechanism, underlying roles of lncRNA are rarely reported in drug-resistant leukemia cells.

Methods

The gene expression profiles of lncRNAs and mRNAs in doxorubicin-resistant K562/ADR and sensitive K562 cells were established by RNA sequencing (RNA-seq). Expression of differentially expressed lncRNAs (DElncRNAs) and DEmRNAs was validated by qRT-PCR. The potential biological functions of DElncRNAs targets were identified by GO and KEGG pathway enrichment analyses, and the lncRNA-miRNA-mRNA ceRNA network was further constructed. K562/ADR cells were transfected with CCDC26 and LINC01515 siRNAs to detect the mRNA levels of GLRX5 and DICER1, respectively. The cell survival rate after transfection was detected by CCK-8 assay.

Results

The ceRNA network was composed of 409 lncRNA-miRNA pairs and 306 miRNA-mRNA pairs based on 67 DElncRNAs, 58 DEmiRNAs and 192 DEmRNAs. Knockdown of CCDC26 and LINC01515 increased the sensitivity of K562/ADR cells to doxorubicin and significantly reduced the half-maximal inhibitory concentration (IC₅₀) of doxorubicin. Furthermore, knockdown of GLRX5 and DICER1 increased the sensitivity of K562/ADR cells to doxorubicin and significantly reduced the IC₅₀ of doxorubicin.

Conclusions

The ceRNA regulatory networks may play important roles in drug resistance of leukemia cells. CCDC26/miR-140-5p/GLRX5 and LINC01515/miR-425-5p/DICER1 may be potential targets for drug resistance in K562/ADR cells. This study provides a promising strategy to overcome drug resistance and deepens the understanding of the ceRNA regulatory mechanism related to drug resistance in CML cells.

Dysregulation of LINC00470 and METTL3 promotes chemoresistance and suppresses autophagy of chronic myelocytic leukaemia cells

Cytoplasmic lncRNAs have been found to directly interact with target mRNAs and regulate their stability. In this study, we aimed to study the molecular mechanism underlying the function of m⁶ A as a central regulator in chemoresistance and CML proliferation. In this study, we established three mice groups (control group, ADR-R group and ADR-R + shLINC00470 group). We detected PTEN mRNA expression in the presence of LINC00470 in the mice models, as well as in the KCL22 and K562 cells. LINC00470 was significantly enriched for PTEN mRNA to exhibit a negative regulatory relationship between LINC00470 and PTEN mRNA. However, the alteration of LINC00470 had no effect on the luciferase activity of PTEN promoter, while the half-life of PTEN mRNA was affected. It was further validated that LINC00470 down-regulated PTEN expression by positively regulating the m6A modification of PTEN mRNA via RNA methyltransferase METTL3. Moreover, the relative expression of LC3II, Beclin-1, ATG7 and ATG5 was all decreased in cells treated with LINC00470, and down-regulated PTEN expression was observed in chemo-resistant cells, while the expression of PTEN was rescued by the transfection of shMETTL3 into chemo-resistant cells. Moreover, the knockdown of METTL3 also restored the normal level of PTEN m⁶ A modification and LINC00470 expression in chemo-resistant cells. In conclusion, our results demonstrated the molecular mechanism underlying the effect of LINC00470 on CML by reducing the PTEN stability via RNA methyltransferase METTL3, thus leading to the inhibition of cell autophagy while promoting chemoresistance in CML.

Cytotoxic effect of 6-Shogaol in Imatinib sensitive and resistant K562 cells

Chronic Myeloid Leukemia (CML) is a clonal hematopoietic malignancy characterized by the formation of BCR-ABL fusion protein. Imatinib (IMA) is a BCR-ABL tyrosine kinase inhibitor (TKI), which exhibited a high rate of response for newly diagnosed CML patients. Emergence of IMA resistance considered as a major challenge in CML therapy. Recent studies reported the anti-cancer effect of natural extracts such as 6-Shogaol (6-SG) which is extracted from ginger and the mechanisms involved in targeting of cancer cells. In the present study, we aimed to explore the potential anticancer effect of 6-SG on K562S (Imatinib sensitive) and K562R (Imatinib resistant) cells. K562S and K562R cells were incubated with increasing concentrations of 6-SG (5 μM- 50 μM) to determine its cytotoxic and apoptotic effects. Cell viability and apoptosis were investigated with spectrophotometric MTT assay and flow cytometric Annexin V staining, respectively. The mRNA expression levels of apoptotic related genes (BAX and BCL-2) and drug transporter (MDR-1 and MRP-1) genes were evaluated with qRT-PCR. According to our results, 6-SG treatment inhibited cell viability, induced apoptosis in both K562S and K562R cells. Based on our RT-PCR results, 6-SG enhanced pro-apoptotic BAX gene and decreased anti-apoptotic BCL-2 gene expression levels significantly in both treated K562S and K562R cells. Furthermore, 6-SG increased MDR-1 mRNA expression level in K562S and K562R cells in comparison with their control counterparts. Whereas, 6-SG decrease MRP-1 mRNA expression level in K562S cells significantly. It is the first study that reveals the apoptotic effect of 6-SG in CML cell line and IMA resistance. Therefore, 6-SG treatment can be suggested as a promising strategy for CML therapy.

Unraveling survivin expression in chronic myeloid leukemia: Molecular interactions and clinical implications

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the BCR-ABL oncoprotein, known to drive leukemogenesis by orchestrating multiple signaling pathways ultimately involved in cell survival. Despite successful response rates of CML patients to tyrosine kinase inhibitors (TKIs), resistance eventually arises due to BCR-ABL-dependent and independent mechanisms. Survivin is an inhibitor of apoptosis protein acting in the interface between apoptosis deregulation and cell cycle progression. In CML, high levels of survivin have been associated with late stages of disease and therapy resistance. In this review, we provide an overview of important aspects concerning survivin subcellular localization and expression pattern in CML patients and cell lines. Moreover, we highlight the relevance of molecular networks involving survivin for disease progression and treatment resistance. Finally, we discuss the mechanisms accounting for survivin overexpression, as well as novel therapeutic interventions that have been designed to counteract survivin-associated malignancy in CML.

SIRT3, PP2A and TTP protein stability in the presence of TNF-α on vincristine-induced apoptosis of leukaemia cells

The contribution of vincristine (VCR)-induced microtubule destabilization to evoke apoptosis in cancer cells remains to be resolved. Thus, we investigated the cytotoxic mechanism of VCR on U937 and HL-60 human leukaemia cell lines. We discovered that VCR treatment resulted in the up-regulation of TNF-α expression and activation of the death receptor pathway, which evoked apoptosis of U937 cells. Moreover, VCR induced microtubule destabilization and mitotic arrest. VCR treatment down-regulated SIRT3, and such down-regulation caused mitochondrial ROS to initiate phosphorylation of p38 MAPK. p38 MAPK suppressed MID1-modulated degradation of the protein phosphatase 2A (PP2A) catalytic subunit. The SIRT3-ROS-p38 MAPK-PP2A axis inhibited tristetraprolin (TTP)-controlled TNF-α mRNA degradation, consequently, up-regulating TNF-α expression. Restoration of SIRT3 and TTP expression, or inhibition of the ROS-p38 MAPK axis increased the survival of VCR-treated cells and repressed TNF-α up-regulation. In contrast to suppression of the ROS-p38 MAPK axis, overexpression of SIRT3 modestly inhibited the effect of VCR on microtubule destabilization and mitotic arrest in U937 cells. Apoptosis of HL-60 cells, similarly, went through the same pathway. Collectively, our data indicate that the SIRT3-ROS-p38 MAPK-PP2A-TTP axis modulates TNF-α expression, which triggers apoptosis of VCR-treated U937 and HL-60 cells. We also demonstrate that the apoptotic signalling is not affected by VCR-elicited microtubule destabilization.

Identification of H2S/NO-donating artemisinin derivatives as potential antileukemic agents

Three H₂S/NO-donating artemisinin derivatives were designed and synthesized. Their antiproliferative activities were evaluated against human acute myeloid leukemia (AML) cell lines of K562 and K562/ADR and human normal liver cells of LO2. Biological evaluation indicated that NO-donating compound 10c exhibited the most potent cytotoxicity against leukemia cells, similar to the bioactivity of clinical drug of homoharringtonine, but showed less toxicity than homoharringtonine against LO2 cells. Further mechanism studies revealed that 10c could enhance the levels of intracellular NO and ROS, induce apoptosis and S phase cell cycle arrest, and disturb the mitochondrial membrane potential in K562 and K562/ADR cells. Western blot results demonstrated that 10c noticeably promoted autophagy by up-regulating the levels of Beclin1 and L3-II expression, inhibited the AKT signaling, and stimulated the AMPK and JNK signaling in both leukemia cell lines. Overall, 10c exhibited the potential to be a promising candidate for the therapy of AML.

Conjugate 10c exhibited potential antiproliferative activity against human acute myeloid leukemia cells.

5-Nitro-Thiophene-Thiosemicarbazone Derivatives Present Antitumor Activity Mediated by Apoptosis and DNA Intercalation

BACKGROUND

Considering the need for the development of new antitumor drugs, associated with the great antitumor potential of thiophene and thiosemicarbazonic derivatives, in this work we promote molecular hybridization approach to synthesize new compounds with increased anticancer activity.

OBJECTIVE

Investigate the antitumor activity and their likely mechanisms of action of a series of N-substituted 2-(5-nitro-thiophene)-thiosemicarbazone derivatives.

METHODS

Methods were performed in vitro (cytotoxicity, cell cycle progression, morphological analysis, mitochondrial membrane potential evaluation and topoisomerase assay), spectroscopic (DNA interaction studies), and in silico studies (docking and molecular modelling).

RESULTS

Most of the compounds presented significant inhibitory activity; the NCIH-292 cell line was the most resistant, and the HL-60 cell line was the most sensitive. The most promising compound was LNN-05 with IC50 values ranging from 0.5 to 1.9 µg.mL-1. The in vitro studies revealed that LNN-05 was able to depolarize (dose-dependently) the mitochondrial membrane, induceG1 phase cell cycle arrest noticeably, promote morphological cell changes associated with apoptosis in chronic human myelocytic leukaemia (K-562) cells, and presented no topoisomerase II inhibition. Spectroscopic UV-vis and molecular fluorescence studies showed that LNN compounds interact with ctDNA forming supramolecular complexes. Intercalation between nitrogenous bases was revealed through KI quenching and competitive ethidium bromide assays. Docking and Molecular Dynamics suggested that 5-nitro-thiophene-thiosemicarbazone compounds interact against the larger DNA groove, and corroborating the spectroscopic results, may assume an intercalating interaction mode.

CONCLUSION

Our findings highlight 5-nitro-thiophene-thiosemicarbazone derivatives, especially LNN-05, as a promising new class of compounds for further studies to provide new anticancer therapies.

Comparison of BCR-ABL Transcript Variants Between Patients With Chronic Myeloid Leukaemia and Leukaemia Cell Lines

BACKGROUND/AIM

Chronic myeloid leukaemia (CML) is a myeloproliferative disorder characterized by the presence of breakpoint cluster region-Abelson murine leukemia (BCR-ABL1) gene fusion as a hallmark that is expressed as two major transcripts b2a2 and b3a2. The aim of this study was to compare the BCR-ABL transcripts in the blood cells of patients with CML, and in chemoresistant and chemosensitive CML cell lines to validate their use as a good method to elucidate CML biology.

MATERIALS AND METHODS

Twelve patients with CML and CML cell lines (K562, K562-LUCENA and FEPS) were analyzed by real-time polymerase chain reaction to evaluate gene expression of BCR-ABL transcripts.

RESULTS

All patients had the same expression levels of b2a2 and b3a3 transcripts, however, CML cell lines presented only b3a2 expression. There were no significant differences in absolute b3a2 expression between patients and CML cell lines.

CONCLUSION

CML cell lines provide a good in vitro alternative in that they have the same BCR-ABL expression as patients.

Current outlook on drug resistance in chronic myeloid leukemia (CML) and potential therapeutic options

Chronic myeloid leukemia cells are armed with several resistance mechanisms that can make current drugs ineffective. A better understanding of resistance mechanisms is yielding new approaches to management of the disease. Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm the hallmark of which, the breakpoint cluster region-Abelson (BCR-ABL) oncogene, has been the target of tyrosine kinase inhibitors (TKIs), which have significantly improved the survival of patients with CML. However, because of an increase in TKI resistance, it is becoming imperative to identify resistance mechanisms so that drug therapies can be better prescribed and new agents developed. In this review, we discuss the various BCR-ABL-dependent and -independent mechanisms of resistance observed in CML, and the range of therapeutic solutions available to overcome such resistance and to ultimately improve the survival of patients with CML.

Enantioselective Synthesis, DFT Calculations, and Preliminary Antineoplastic Activity of Dibenzo 1-Azaspiro[4.5]decanes on Drug-Resistant Leukemias

The addition of 2-bromobenzylmagnesium bromide to chiral N- tert-butanesulfinyl imines derived from tetralone-type ketones proceeds with high levels of diastereocontrol. The resulting sulfinamide derivatives were transformed into dibenzoazaspiro compounds after a palladium-catalyzed intramolecular N-arylation. DFT calculations have been performed to rationalize the stereochemical course of the reaction. Similar results have been obtained considering either diethyl ether or toluene as a solvent, in both cases in an excellent agreement with experimental findings. NCI topological calculations have also been used to evidence crucial noncovalent interactions. In addition, the azaspiro compounds reduced the viability of chronic myeloid leukemia cells in the micromolar range. Notably, both the halogen-substituted ( R)- and ( S)-8g and -8h as well as ( R)-8j were at least two times more effective on a multidrug-resistant derivative than on the parental cell line, exerting a collateral sensitivity effect.

Effect of inotuzumab ozogamicin on the QT interval in patients with haematologic malignancies using QTc-concentration modelling

AIM

The aim of this study was to characterize the effect of inotuzumab ozogamicin on QT interval in patients with B-cell malignancies.

METHODS

Data were pooled from three clinical studies including 250 patients (n = 2743) who received inotuzumab ozogamicin monotherapy. Patients with relapsed/refractory acute lymphoblastic leukaemia (NCT01564784 and NCT01363297) received 1.8 mg m^-2 per cycle in divided doses (mean C_max 371 ng ml^-1 ; considered therapeutic) and patients with relapsed/refractory non-Hodgkin lymphoma (NCT00868608) received 1.8 mg m^-2 per cycle as a single dose (mean C_max 569 ng ml^-1 ; considered supratherapeutic). Triplicate 12-lead electrocardiograms were performed at baseline and predefined time points postdose with paired pharmacokinetic collections. The exposure-response relationship between corrected QT interval (QTc: QT interval corrected using population-specific formula [QTcS] or QT interval corrected using Fridericia's formula [QTcF]) and inotuzumab ozogamicin concentration was characterized using a linear mixed-effects model, and simulations were performed using the final validated model. Full model development involved testing for covariates that may account for part of the identified variability.

RESULTS

QTc intervals had a small but positive correlation with inotuzumab ozogamicin concentration. Based on 1000 simulations, median (upper 95% CI) QTcS and QTcF changes from baseline were <10 ms at both therapeutic (2.70 ms [5.40 ms] and 2.53 ms [4.92 ms], respectively) and supratherapeutic (4.14 ms [8.28 ms] and 3.87 ms [7.54 ms], respectively) concentrations.

CONCLUSIONS

Inotuzumab ozogamicin (1.8 mg m^-2 per cycle) is not predicted to pose a clinically significant safety risk for QT prolongation in patients with acute lymphoblastic leukaemia or non-Hodgkin lymphoma.

Artesunate enhances adriamycin cytotoxicity by inhibiting glycolysis in adriamycin-resistant chronic myeloid leukemia K562/ADR cells

Adriamycin (ADR) is a widely used drug in multiple cancers including leukemia.

Analogues of the Lignan Pinoresinol as Novel Lead Compounds for P-glycoprotein (P-gp) Inhibitors

To find novel P-gp-inhibitors, a library of pregnane X receptor (PXR) ligands and the ZINC DrugsNow library were superimposed on the P-gp inhibitor (+)-pinoresinol (1) used as a query for a three-dimensional similarity search. After determining the TanimotoCombo index of similarity with 1, eight compounds from the PXR library and two ZINC compounds were selected for biological evaluation. The P-gp inhibition study showed that compounds 7, 8, and 9 successfully increased intracellular doxorubicin (DOX) accumulation in the P-gp overexpressed Lucena 1 cells from 25, 12.5, and 6.25 μM, respectively. Among a series of analogues of 9, compounds 26-30 were shown to be active, with 26 and 27 causing a significant increase in DOX accumulation from 1.56 μM and rendering Lucena 1 sensitive to DOX from 1.56 and 0.78 μM, respectively. Molecular modeling studies showed that both compounds bind to the P-gp at transmembrane helices (TMH) 4, 5, and 6, with 27 also showing contacts with TMH 3.

Tendency of K562 Chronic Myeloid Leukemia Cells Towards Cell Reprogramming

Objective

Cancer cell reprogramming is a potential tool to study cancer progression, disease pathology, and drug sensitivity. Prior to performing cancer reprogramming studies, it is important to evaluate the stemness predisposition of cells that will be reprogrammed. We performed a proof-of-concept study with chronic myeloid leukemia K562 cells in order to evaluate their tendency for cancer cell reprogramming.

Materials and Methods

Expression of reprogramming factors, pluripotency markers, and tumor-suppressor genes was analyzed at gene and protein levels via real-time reverse transcription-polymerase chain reaction and flow cytometry. Human peripheral blood mononuclear cells (PBMCs) were used as a positive control.

Results

K562 cells were shown to express higher levels of most of the reprogramming factors and pluripotency markers. Expression of p53, which is one of the main regulators during the generation of induced pluripotent stem cells, was found to be lower in K562 cells compared to PBMCs, whereas the other tumor-suppressor genes showed higher expression levels.

Conclusion

This study suggested that, similar to healthy human PBMCs, K526 cells could be used in cancer cell reprogramming studies. Generating induced pluripotent stem cells from leukemia cells could help scientists to establish chronic myeloid leukemia models in vitro for a better understanding of therapy resistance and development of novel therapeutic targets.

Crosstalk between BCR-ABL and protease-activated receptor 1 (PAR1) suggests a novel target in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the presence of the Philadelphia chromosome, which generates the oncogene BCR-ABL1. Protease-activated receptor 1 (PAR1) is involved in tumor progression and angiogenesis. We have previously reported that PAR1 expression is elevated in human leukemias that display a more aggressive clinical behavior, including the blast crisis of CML. In this study, we analyzed the crosstalk between the oncoprotein BCR-ABL and PAR1 in CML. Leukemic cell lines transfected with the BCR-ABL1 oncogene showed significantly higher expression levels of PAR1 compared with that of wild-type counterparts. This phenomenon was reversed by treatment with tyrosine kinase inhibitors (TKIs). Conversely, treatment with the PAR1 antagonist SCH79797 inhibited BCR-ABL expression. The PAR1 antagonist induced apoptosis in a dose- and time-dependent manner. Higher vascular endothelial growth factor (VEGF) levels were observed in cells transfected with BCR-ABL1 than in their wild-type counterparts. VEGF expression was strongly inhibited after treatment with either TKIs or the PAR1 antagonist. Finally, we evaluated PAR1 expression in CML patients who were either in the blast or chronic phases and had either received TKI treatment or no treatment. A significant decrease in PAR1 expression was observed in treatment-responsive patients, as opposed to a significant increase in PAR1 expression levels in treatment-resistant patients. Patients classified as high risk according to the Sokal index showed higher PAR1 expression levels. Our results demonstrate the crosstalk between BCR-ABL and PAR1. These data may offer important insight into the development of new therapeutic strategies for CML.

Femtosecond laser pulse assisted photoporation for drug delivery in Chronic myelogenous leukemia cells

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder occurs in the pluripotent hematopoietic stem cell. Currently, first-generation tyrosine kinase inhibitor (TKI) imatinib is the mainstay for the treatment of CML. Second generation TKI's like ponatinib, dasatinib, nilotinib, and bafetinib were treated against resistant CML. However, several CML patients develop resistance towards all existing inhibitors. Curcumin (Curcuma longa) a plant-derived natural compound is an effective bioactive component against various cancers including CML. Many studies have shown that curcumin induces time- and dose-dependent apoptosis in CML cells by regulating various downstream molecular regulators. Despite curcumin's selective cytotoxicity towards cancer cells, it has very poor bioavailability both in in-vitro and in-vivo conditions. In this present study, we have used femtosecond laser (fs-laser) pulses to ablate the cell membrane and standardized the conditions required for creating a cell membrane pores with less lethality. Following fs-laser pulse irradiation, K562 cells were incubated along with curcumin 30 μM for 0 h, 6 h,12 h and 24 h. Interestingly irradiated cells have shown higher sensitivity towards curcumin than non-irradiated cells. Immunoblotting studies showed higher induction levels of cleaved caspase 3 and 9 in irradiated population than non-irradiated. In summary, the results prove that irradiation by fs-laser pulses enhanced the bioavailability of curcumin and shows caspase-mediated cell death in irradiated CML cells than other populations.

Cytotoxic Activity of Extracts from Plants of Central Argentina on Sensitive and Multidrug-Resistant Leukemia Cells: Isolation of an Active Principle from Gaillardia megapotamica

Plants are a significant reservoir of cytotoxic agents, including compounds with the ability to interfere with multidrug-resistant (MDR) cells. With the aim of finding promising candidates for chemotherapy, 91 native and naturalized plants collected from the central region of Argentina were screened for their cytotoxic effect toward sensitive and MDR P-glycoprotein (P-gp) overexpressing human leukemia cells by means of MTT assays. The ethanol extracts obtained from Aldama tucumanensis, Ambrosia elatior, Baccharis artemisioides, Baccharis coridifolia, Dimerostemma aspilioides, Gaillardia megapotamica, and Vernonanthura nudiflora presented outstanding antiproliferative activity at 50 μg/mL, with inhibitory values from 93 to 100%, when tested on the acute lymphoblastic leukemia (ALL) cell line CCRF-CEM and the resistant derivative CEM-ADR5000, while 70-90% inhibition was observed against the chronic myelogenous leukemia (CML) cell K562 and its corresponding resistant subline, Lucena 1. Subsequent investigation showed these extracts to possess marked cytotoxicity with IC50 values ranging from 0.37 to 29.44 μg/mL, with most of them being below 7 μg/mL and with ALL cells, including the drug-resistant phenotype, being the most affected. G. megapotamica extract found to be one of the most effective and bioguided fractionation yielded helenalin (1). The sesquiterpene lactone displayed IC50 values of 0.63, 0.19, 0.74, and 0.16 μg/mL against K562, CCRF-CEM, Lucena 1, and CEM/ADR5000, respectively. These results support the potential of these extracts as a source of compounds for treating sensitive and multidrug-resistant leukemia cells and support compound 1 as a lead for developing effective anticancer agents.

Germacrone reverses adriamycin resistance in human chronic myelogenous leukemia K562/ADM cells by suppressing MDR1 gene/P-glycoprotein expression

Multidrug resistance (MDR) usually causes chemotherapy failure of chronic myelogenous leukemia (CML). Germacrone is a terpenoid compound and has been reported to reverse MDR in breast cancer cells. However, the effect of germacrone on MDR in CML cells was unknown. The aim of the present study was to evaluate the effect of germacrone on MDR in adriamycin resistance of CML cells. Treatment with a combination of germacrone and adriamycin synergistically inhibited the viability and increased LDH release in K562/ADM cells. Adriamycin induced the apoptosis and caspase-3 activity of K562/ADM cells, and the germacrone treatment significantly enhanced the induction. Adriamycin treatment inhibited the expression of Bcl-2 and induced the expression of Bax, and germacrone enhanced the effect of adriamycin. Germacrone decreased adriamycin-induced expression of MDR1 mRNA and P-gp protein. Overexpression of P-glycoprotein (P-gp) reversed the effect of germacrone on adriamycin resistance in K562/ADM cells. In conclusion, germacrone reversed adriamycin resistance in human chronic myelogenous leukemia K562/ADM cells by suppressing MDR1 gene/P-gp expression. The results indicated that germacrone might be a new MDR reversal agent for CML chemotherapy.

Activation of hedgehog signaling and its association with cisplatin resistance in ovarian epithelial tumors

Few studies have evaluated Hedgehog (Hh) signaling pathway activation in different types of ovarian tumors including benign, borderline and malignant ovarian tumors. The present study investigated the expression of Hh signaling pathway components (SHH, SMO, PTCH, and GLI1) in 193 ovarian epithelial tumor specimens (including 147 malignant epithelial ovarian cancers, 30 borderline ovarian tumors, 16 benign ovarian epithelial tumors) and 11 normal ovarian epithelial tissues by immunohistochemistry. The results demonstrated widespread expression of Hh pathway molecules in ovarian tumors. However, there was no significant difference in the expression intensity of SHH among the four groups (P>0.05). Statistically significant differences were identified in the expression intensity of the SMO, PICH and GLI1 among groups (P<0.001). In addition, significant differences were also revealed in the expression levels of SMO (P=0.013) and GLI1 (P=0.0005) between the platinum drug-sensitive and drug-resistant groups. The overexpression of SMO and GLI1 was further confirmed in the cisplatin-resistant ovarian cancer cell line A2780/DDP by immunofluorescence, flow cytometry and western blotting. The results revealed that the Hh pathway components SMO, PICH and GLI1 are activated in ovarian epithelial tumors. Novel potential associations between cisplatin resistance and the overexpression of SMO and Gli1 in malignant epithelial ovarian cancer were also observed, which may provide an innovative approach to the treatment of drug resistant ovarian epithelial cancer.

The anti-apoptotic PON2 protein is Wnt/β-catenin-regulated and correlates with radiotherapy resistance in OSCC patients

Aberrant Wnt signaling and control of anti-apoptotic mechanisms are pivotal features in different types of cancer to undergo cell death programs. The intracellular human enzyme Paraoxonase-2 (PON2) is known to have anti-apoptotic properties in leukemia and oral squamous cell cancer (OSCC) cells. However, the distinct regulating pathways are poorly understood. First, we present a so far unknown regulation of PON2 protein expression through the Wnt/GSK3β/β-catenin pathway in leukemia and OSCC cells. This was confirmed via in silico analysis, promoter reporter studies and treatment of multiple cell lines (K562, SCC-4, PCI-13) with different Wnt ligands/inhibitors in vitro. Ex vivo analysis of OSCC patients revealed a correlation between PON2 and β-catenin expression in tumor tissue. Higher PON2 expression in OSCC is associated with relapse independently of treatment (e.g. surgery/radio-/chemotherapy). These results emphasize the clinical impact of the newly described regulation of PON2 through Wnt/GSK3β/β-catenin. More importantly, the study revealed the fundamental finding of an overall Wnt/GSK3β/β-catenin dependent regulation of PON2 in different cancers, which was confirmed by systematic and multimethodological approaches. Thus, the herein presented mechanistic insight contributes to a better understanding of tumor specific escape from cell death strategies and suggests PON2 as a new potential biomarker for therapy resistance or as a prognostic tumor marker.

Inhibition of Siah2 Ubiquitin Ligase by Vitamin K3 Attenuates Chronic Myeloid Leukemia Chemo-Resistance in Hypoxic Microenvironment

BACKGROUND A hypoxic microenvironment is associated with resistance to tyrosine kinase inhibitors (TKIs) and a poor prognosis in chronic myeloid leukemia (CML). The E3 ubiquitin ligase Siah2 plays a vital role in the regulation of hypoxia response, as well as in leukemogenesis. However, the role of Siah2 in CML resistance is unclear, and it is unknown whether vitaminK3 (a Siah2 inhibitor) can improve the chemo-sensitivity of CML cells in a hypoxic microenvironment. MATERIAL AND METHODS The expression of Siah2 was detected in CML patients (CML-CP and CML-BC), K562 cells, and K562-imatinib-resistant cells (K562-R cells). We measured the expression of PHD3, HIF-1α, and VEGF in both cell lines under normoxia and hypoxic conditions, and the degree of leukemic sensitivity to imatinib and VitaminK3 were evaluated. RESULTS Siah2 was overexpressed in CML-BC patients (n=9) as compared to CML-CP patients (n=13). Similarly, K562-imatinib-resistant cells (K562-R cells) showed a significantly higher expression of Siah2 as compared to K562 cells in a hypoxic microenvironment. Compared to normoxia, under hypoxic conditions, both cell lines had lower PHD3, higher HIF-1α, and higher VEGF expression. Additionally, Vitamin K3 (an inhibitor of Siah2) reversed these changes and promoted a higher degree of leukemic sensitivity to imatinib. CONCLUSIONS Our findings indicate that the Siah2-PHD3- HIF-1α-VEGF axis is an important hypoxic signaling pathway in a leukemic microenvironment. An inhibitor of Siah2, combined with TKIs, might be a promising therapy for relapsing and refractory CML patients.

Encapsulation of Piper cabralanum (Piperaceae) nonpolar extract in poly(methyl methacrylate) by miniemulsion and evaluation of increase in the effectiveness of antileukemic activity in K562 cells

This study aimed to synthesize and characterize nanoparticles (NPs) of poly(methyl methacrylate) (PMMA) and evaluate their ability to incorporate plant extracts with antitumor activity and low dissolution in aqueous media. The extract used was n-hexane partition of the methanol extract of Piper cabralanum (PCA-HEX). PMMA NPs were obtained using the mini-emulsion method, which was able to encapsulate almost 100% of PCA-HEX. The synthesized polymeric particles presented with a size of 200 nm and a negative charge. Cytotoxicity tests by MTT and trypan blue assays showed that NPs without PCA-HEX did not kill leukemic cells (K562 cells). NPs containing PCA-HEX were able to enhance cell death when compared to pure extract. The results showed that PMMA NPs could be useful as a drug delivery system as they can enhance the antitumor activity of the PCA-HEX extract by more than 20-fold. PMMA NPs containing plant extracts with antitumor activities may be an alternative to control the evolution of diseases such as leukemia.

Quinacrine induces the apoptosis of human leukemia U937 cells through FOXP3/miR-183/β-TrCP/SP1 axis-mediated BAX upregulation

Quinacrine, which is clinically used as an antimalarial drug, has anti-cancer activity. However, mechanism underlying its cytotoxic effect remains to be completely elucidated. In the present study, we investigated the cytotoxic effect of quinacrine on human leukemia U937 cells. Quinacrine-induced apoptosis of U937 cells was accompanied with ROS generation, mitochondrial depolarization, and BAX upregulation. Quinacrine-treated U937 cells showed ROS-mediated p38 MAPK activation and ERK inactivation, which in turn upregulated FOXP3 transcription. FOXP3-mediated miR-183 expression decreased β-TrCP mRNA stability and suppressed β-TrCP-mediated SP1 degradation, thus increasing SP1 expression in U937 cells. Upregulated SP1 expression further increased BAX expression. BAX knock-down attenuated quinacrine-induced mitochondrial depolarization and increased the viability of quinacrine-treated cells. Together, our data indicate that quinacrine-induced apoptosis of U937 cells is mediated by mitochondrial alterations triggered by FOXP3/miR-183/β-TrCP/SP1 axis-mediated BAX upregulation.

PIM-1 kinase inhibitor SMI-4a exerts antitumor effects in chronic myeloid leukemia cells by enhancing the activity of glycogen synthase kinase 3β

The development of targeted tyrosine kinase inhibitors (TKIs) has succeeded in altering the course of chronic myeloid leukemia (CML). However, a number of patients have failed to respond or experienced disease relapse following TKI treatment. Proviral integration site for moloney murine leukemia virus-1 (PIM-1) is a serine/threonine kinase that participates in regulating apoptosis, cell cycle, signal transduction and transcriptional pathways, which are associated with tumor progression, and poor prognosis. SMI-4a is a selective PIM-1 kinase inhibitor that inhibits PIM-1 kinase activity in vivo and in vitro. The present study aimed to explore the mechanism underlying the antitumor effect of SMI-4a in K562 and imatinib-resistant K562 (K562/G) cell lines. It was demonstrated that SMI-4a inhibited the proliferation of K562 and K562/G cells using a WST-8 assay. The Annexin V-propidium iodide assay demonstrated that SMI-4a induced apoptosis of K562 and K562/G cells in a dose-, and time-dependent manner. Furthermore, Hoechst 33342 staining was used to verify the apoptosis rate. The clone formation assay revealed that SMI-4a significantly inhibited the colony formation capacity of K562 and K562/G cells. Western blot analysis demonstrated that SMI-4a decreased phosphorylated (p)-Ser9-glycogen synthase kinase (GSK) 3β/pGSK3β and inhibited the translocation of β-catenin. In addition, the downstream gene expression of apoptosis regulator Bax and poly(ADP-ribose) polymerase-1 was upregulated, and apoptosis regulator Bcl-2 and Myc proto-oncogene protein expression levels were downregulated. Immunofluorescence results demonstrated changes in the expression level of β-catenin in the plasma and nucleus. The results of the present study suggest that SMI-4a is an effective drug to use in combination with current chemotherapeutics for the treatment of imatinib-resistant CML.

Indole-3-carbinol induces apoptosis of chronic myelogenous leukemia cells through suppression of STAT5 and Akt signaling pathways

Signal transducer and activator of transcription 5 and Akt pathways, implicated in signaling transduction downstream of BCR-ABL, play critical roles in the pathogenesis of chronic myeloid leukemia. Therefore, idenication of novel compounds that modulate the activity of such pathways could be a new approach in the treatment of chronic myeloid leukemia. Previous studies have demonstrated that indole-3-carbinol inhibits the proliferation and induces apoptosis of various tumor cells. However, its anticancer activity against chronic myeloid leukemia cells and the underlying mechanism remain unclear. Our data revealed that indole-3-carbinol promoted mitochondrial apoptosis of chronic myeloid leukemia-derived K562 cells, as evidenced by the activation of caspases and poly (ADP-ribose) polymerase cleavage. Treatment with indole-3-carbinol was found to be associated with a decrease in the cellular levels of phospho-Akt and phospho-signal transducer and activator of transcription 5. In addition, real-time polymerase chain reaction analysis showed that the downregulation of genes is regulated by Akt and signal transducer and activator of transcription 5. We also found that treatment with indole-3-carbinol resulted in the activation of the p38 mitogen-activated protein kinase and reduced expression of human telomerase and c-Myc. Collectively, these results demonstrate that the oncogenic signal transducer and activator of transcription 5/Akt pathway is a cellular target for indole-3-carbinol in chronic myeloid leukemia cells. Thus, this clinically tested natural compound can be a potential candidate in the treatment of chronic myeloid leukemia following confirmation with clinical studies.

Effectiveness of imatinib mesylate over etoposide in the treatment of sensitive and resistant chronic myeloid leukaemia cells in vitro

Chronic myeloid leukaemia (CML) is a form of leukaemia derived from the myeloid cell lineage. Imatinib mesylate, the breakpoint cluster region-abelson murine leukeamia kinase inhibitor, is a specific reagent used in the clinical treatment of CML. The DNA topoisomerase II inhibitor, etoposide, is also employed as a therapeutic, though it is used to a lesser extent. The present study aims to evaluate the effects of CML-targeted therapy, utilising imatinib mesylate and etoposide in the in vitro treatment of parental sensitive and adriamycin-resistant CML in the K562 and K562/ADM cell lines, respectively. Preliminary work involved the screening of multidrug resistant (MDR) gene expression, including MDR1, MRP1 and B-cell lymphoma 2 (BCL-2) at the mRNA levels. The sensitive and resistant CML cell lines expressed the MRP1 gene, though the sensitive K562 cells expressed low, almost undetectable levels of MDR1 and BCL-2 genes relative to the K562/ADM cells. Following treatment with imatinib mesylate or etoposide, the IC50 for imatinib mesylate did not differ between the sensitive and resistant cell lines (0.492±0.024 and 0.378±0.029, respectively), indicating that imatinib mesylate is effective in the treatment of CML regardless of cell chemosensitivity. However, the IC50 for etoposide in sensitive K562 cells was markedly lower than that of K562/ADM cells (50.6±16.5 and 194±8.46 µM, respectively), suggesting that the higher expression levels of MDR1 and/or BCL-2 mRNA in resistant cells may be partially responsible for this effect. This is supported by terminal deoxynucleotidyl transferase dUTP nick-end labeling data, whereby a higher percentage of apoptotic cells were found in the sensitive and resistant K562 cells treated with imatinib mesylate (29.3±0.2 and 31.9±16.7%, respectively), whereas etoposide caused significant apoptosis of sensitive K562 cells (18.3±8.35%) relative to K562/ADM cells (5.17±3.3%). In addition, the MDR genes in K562/ADM cells were knocked down by short interfering RNAs. The percentage knockdowns were 15.4% for MRP1, 17.8% for MDR and 30.7% for BCL-2, which resulted in a non-significant difference in the half maximal inhibitory concentration value of K562/ADM cells relative to K562 cells upon treatment with etoposide.

P53 tumor suppressor is required for efficient execution of the death program following treatment with a cytotoxic limonoid obtained from Melia azedarach

This work examines the antitumor activity of an isomeric mixture (1), composed of the limonoids meliartenin and its interchangeable isomer 12-hydroxyamoorastatin. The results obtained showed that 1 displayed outstanding cytotoxic activity against CCRF-CEM, K562, A549 and HCT116 cells, with a highly selective effect on the latter, with an IC₅₀ value of 0.2 μM. Based on this finding, HCT116 cells were selected to study the mechanism of action of 1. Cell cycle analysis revealed that 1 induced sustained arrest in the S-phase, which was followed by the triggering of apoptotic cell death and reduced clonogenic capacity. This cytotoxicity was seen to be preceded by the upregulation of the tumor suppressor p53 and its target effector p21. In addition, it was found that p53 expression was required for efficient cell death induction, and thus that the toxicity of 1 relies mainly on p53-dependent mechanisms. Taken together, these findings position 1 as a potent antitumor agent, with potential for the development of novel chemotherapeutic drugs based on the induction of S-phase arrest.

Mechanism Underlying the Reversal of Drug Resistance in P-Glycoprotein-Expressing Leukemia Cells by Pinoresinol and the Study of a Derivative

P-glycoprotein (P-gp) is a membrane protein associated with multidrug resistance (MDR) due to its key role in mediating the traffic of chemotherapeutic drugs outside cancer cells, leading to a cellular response that hinders efforts toward successful therapy. With the aim of finding agents that circumvent the MDR phenotype mediated by P-gp, 15 compounds isolated from native and naturalized plants of Argentina were screened. Among these, the non-cytotoxic lignan (±) pinoresinol successfully restored sensitivity to doxorubicin from 7 μM in the P-gp overexpressed human myelogenous leukemia cells, Lucena 1. This resistance-reversing effect was confirmed by competitively increasing the intracellular doxorubicin accumulation and by significantly inhibiting the efflux of doxorubicin and, to a lesser extent, that of rhodamine 123. The activity obtained was similar to that observed with verapamil. No such results were observed in the sensitive parental K562 cell line. To gain deeper insight into the mode of action of pinoresinol, its effect on P-gp function and expression was examined. The docking simulations indicated that the lignan bound to P-gp at the apex of the V-shaped transmembrane cavity, involving transmembrane helices 4, 5, and 6, and partially overlapped the binding region of tariquidar, which was used as a positive control. These results would shed some light on the nature of its interaction with P-gp at molecular level and merit further mechanistic and kinetic studies. In addition, it showed a maximum 29% activation of ATP hydrolysis and antagonized verapamil-stimulated ATPase activity with an IC₅₀ of 20.9 μM. On the other hand, pinoresinol decreased the presence of P-gp in the cell surface. Derivatives of pinoresinol with improved activity were identified by docking studies. The most promising one, the non-cytotoxic 1-acetoxypinoresinol, caused a reversion of doxorubicin resistance from 0.11 μM and thus higher activity than the lead compound. It also caused a significant increase in doxorubicin accumulation. Results were similar to those observed with verapamil. The results obtained positioned these compounds as potential candidates for effective agents to overcome P-gp-mediated MDR, leading to better outcomes for leukemia chemotherapy.

Targeting P-glycoprotein expression and cancer cell energy metabolism: combination of metformin and 2-deoxyglucose reverses the multidrug resistance of K562/Dox cells to doxorubicin

P-glycoprotein (P-gp) is one of the major obstacles to efficiency of cancer chemotherapy. Here, we investigated whether combination of metformin and 2-deoxyglucose reverses the multidrug resistance (MDR) of K562/Dox cells and tried to elucidate the possible mechanisms. The combination of metformin and 2-deoxyglucose selectively enhanced the cytotoxicity of doxorubicin against K562/Dox cells. Metformin was not a substrate of P-gp but suppressed the elevated level of P-gp in K562/Dox cells. The downregulation of P-gp may be partly attributed to the inhibition of extracellular signal-regulated kinase pathway. The addition of 2-deoxyglucose to metformin initiated a strong metabolic stress in both K562 and K562/Dox cells. Combination of metformin and 2-deoxyglucose inhibited glucose uptake and lactate production in K562 and K562/Dox cells leading to a severe depletion in ATP and a enhanced autophagy. Above all, P-gp substrate selectively aggravated this ATP depletion effect and increased cell apoptosis in K562/Dox cells. In conclusion, metformin decreases P-gp expression in K562/Dox cells via blocking phosphorylation of extracellular signal-regulated kinase. P-gp substrate increases K562/Dox cell apoptosis via aggravating ATP depletion induced by combination of metformin and 2-deoxyglucose. Our observations highlight the importance of combination of metformin and 2-deoxyglucose in reversing multidrug resistance.

Antibacterial and Cytotoxic Activity of Compounds Isolated from Flourensia oolepis

The antibacterial and cytotoxic effects of metabolites isolated from an antibacterial extract of Flourensia oolepis were evaluated. Bioguided fractionation led to five flavonoids, identified as 2′,4′-dihydroxychalcone (1), isoliquiritigenin (2), pinocembrin (3), 7-hydroxyflavanone (4), and 7,4′-dihydroxy-3′-methoxyflavanone (5). Compound 1 showed the highest antibacterial effect, with minimum inhibitory concentration (MIC) values ranging from 31 to 62 and 62 to 250 μg/mL, against Gram-positive and Gram-negative bacteria, respectively. On further assays, the cytotoxic effect of compounds 1–5 was determined by MTT assay on acute lymphoblastic leukemia (ALL) and chronic myeloid leukemia (CML) cell lines including their multidrug resistant (MDR) phenotypes. Compound 1 induced a remarkable cytotoxic activity toward ALL cells (IC₅₀ = 6.6–9.9 μM) and a lower effect against CML cells (IC₅₀ = 27.5–30.0 μM). Flow cytometry was used to analyze cell cycle distribution and cell death by PI-labeled cells and by Annexin V/PI staining, respectively. Upon treatment, 1 induced cell cycle arrest in the G₂/M phase accompanied by a strong induction of apoptosis. These results describe for the first time the antibacterial metabolites of F. oolepis extract, with 1 being the most effective. This chalcone also emerges as a selective cytotoxic agent against sensitive and resistant leukemic cells, highlighting its potential as a lead compound.

Resveratrol induces apoptosis in K562 cells via the regulation of mitochondrial signaling pathways

Resveratrol, an edible polyphenolic phytoalexin obtained primarily from root extracts of the oriental plant, Polygonum cuspidatum and from grapes and red wine, has been reported as an anticancer compound against several types of cancer, the accurate molecular mechanisms of by which it induces apoptosis are limited. In the present study, the molecular mechanisms of resveratrol on human leukemia K562 cells apoptosis was examined. Our results showed that resveratrol significantly decreased cell viability and triggered cell apoptosis in K562 cells. Resveratrol-induced apoptosis of K562 cells was associated with the dissipation of mitochondrial membrane potential (MMP) and the release of cytochrome c into the cytosol. Furthermore, the up-regulation of Bax/Bcl-2 ratio, the activation of caspase-3 and increased cleaved PARP was also observed in K562 cells treated with resveratrol. Thus, we considered that the resveratrol-induced apoptosis of K562 cells might be mediated through the mitochondria pathway, which gives the rationale for in vivo studies on the utilization of resveratrol as a potential cancer therapeutic compound.

The implication of cancer progenitor cells and the role of epigenetics in the development of novel therapeutic strategies for chronic myeloid leukemia

SIGNIFICANCE

Chronic myeloid leukemia (CML) involves the malignant transformation of hematopoietic stem cells, defined largely by the Philadelphia chromosome and expression of the breakpoint cluster region-Abelson (BCR-ABL) oncoprotein. Pharmacological tyrosine kinase inhibitors (TKIs), including imatinib mesylate, have overcome limitations in conventional treatment for the improved clinical management of CML.

RECENT ADVANCES

Accumulated evidence has led to the identification of a subpopulation of quiescent leukemia progenitor cells with stem-like self renewal properties that may initiate leukemogenesis, which are also shown to be present in residual disease due to their insensitivity to tyrosine kinase inhibition.

CRITICAL ISSUES

The characterization of quiescent leukemia progenitor cells as a unique cell population in CML pathogenesis has become critical with the complete elucidation of mechanisms involved in their survival independent of BCR-ABL that is important in the development of novel anticancer strategies. Understanding of these functional pathways in CML progenitor cells will allow for their selective therapeutic targeting. In addition, disease pathogenesis and drug responsiveness is also thought to be modulated by epigenetic regulatory mechanisms such as DNA methylation, histone acetylation, and microRNA expression, with a capacity to control CML-associated gene transcription.

FUTURE DIRECTIONS

A number of compounds in combination with TKIs are under preclinical and clinical investigation to assess their synergistic potential in targeting leukemic progenitor cells and/or the epigenome in CML. Despite the collective promise, further research is required in order to refine understanding, and, ultimately, advance antileukemic therapeutic strategies.

[Interleukin-23 strengthens the anti-apoptotic and drug resistance of human tongue squamous cell carcinoma through the Wingless-related integration site/β-catenin pathway]

OBJECTIVE

This study aims to detect the expression level of interleukin-23 (IL-23) in tongue squamous cell carcinoma tissues and its relationship with clinical prognosis, as well as explore the anti-apoptotic and drug resistance of the tongue squamous cell line-SCC9 before and after treatment with IL-23.

METHODS

The expression of IL-23 in tumor tissues from 28 tongue cancer patients was analyzed by immunohistochemistry assay. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the mRNA expression of Wingless-related integration site (Wnt)1 and c-myc in SCC9 cells treated with different IL-23 concentrations. After interferencing the β-catenin with small interfering RNA (siRNA), the expression of β-catenin, B-cell lymphoma-2 (Bcl-2), ATP-binding cassette sub-family G member 2 (ABCG2), and permeability-glycoprotein (P-gp) in SCC9 was measured by Western blot analysis. The effect of IL-23 on the apoptotic resistance of SCC9 to cisplatin was examined by methyl thiazolyl tetrazolium test.

RESULTS

The expression of IL-23 in tongue cancer tissues was correlated with lymphatic metastasis, nerve invasion, and the recurrence after therapy (P<0.05). After dealing with IL-23, SCC9 showed the upregulation effect of Bcl-2, ABCG2 and P-gp expressions. IL-23 was closely related to the activation level of the Wnt pathway and significantly strengthened the resistance to cisplatin (P<0.01).

CONCLUSION

IL-23 activates the Wnt pathway in tongue squamous cell carcinoma, thereby enhancing its resistance to apoptosis and drug.

Resveratrol induces apoptosis of leukemia cell line K562 by modulation of sphingosine kinase-1 pathway

To explore the effects of resveratrol in a human myelogenous leukemia cell line K562 and its potential molecular mechanisms. The anti-proliferation effect of resveratrol-induced apoptosis on K562 cells were detected using MTT assay. Western blotting was performed for detecting changes of SphK1 expression in total cell protein and membrane/cytosol protein in K562 cells respectively after exposure to resveratrol. A biochemical assay was used to measure the activity of SphK after treatment of resveratrol, and then S1P and ceramide levels were examined using ELISA kits. Hochest 33258 staining and flow cytometry were applied to detect the apoptosis condition of K562 cells treated with resveratrol. Resveratrol inhibited the proliferation and induced apoptosis in K562 cells in a dose and time-dependent manner. Western blotting revealed that resveratrol did not affect total SphK1 expression level in K562 cells, but significantly changed the translocation of SphK1, the membrane SphK1 was decreased while cytosol SphK1 level was elevated. The activity of SphK1 in resveratrol treated groups was decreased compared to control group with a significant decrease of S1P and increase of ceramide level. Furthermore, Hoechst 33258 staining and Annexin V-FITC analysis confirmed the notable apoptotic effect of resveratrol in its anti-leukemia process. Resveratrol-induced proliferation inhibition of K562 cells might be mediated through its modulation activity of SphK1 pathway by regulating S1P and ceramide levels, which then affected the proliferation and apoptosis process of leukemia cells. SphK1/S1P pathway represents a target of resveratrol in human leukemia.