Chloroquine enhances the efficacy of chemotherapy drugs against acute myeloid leukemia by inactivating the autophagy pathway.

Current therapy for acute myeloid leukemia (AML) is largely hindered by the development of drug resistance of commonly used chemotherapy drugs, including cytarabine, daunorubicin, and idarubicin. In this study, we investigated the molecular mechanisms underlying the chemotherapy drug resistance and potential strategy to improve the efficacy of these drugs against AML. By analyzing data from ex vivo drug-response and multi-omics profiling public data for AML, we identified autophagy activation as a potential target in chemotherapy-resistant patients. In THP-1 and MV-4-11 cell lines, knockdown of autophagy-regulated genes ATG5 or MAP1LC3B significantly enhanced AML cell sensitivity to the chemotherapy drugs cytarabine, daunorubicin, and idarubicin. In silico screening, we found that chloroquine phosphate mimicked autophagy inactivation. We showed that chloroquine phosphate dose-dependently down-regulated the autophagy pathway in MV-4-11 cells. Furthermore, chloroquine phosphate exerted a synergistic antitumor effect with the chemotherapy drugs in vitro and in vivo. These results highlight autophagy activation as a drug resistance mechanism and the combination therapy of chloroquine phosphate and chemotherapy drugs can enhance anti-AML efficacy.

PARP-1 inhibitors enhance the chemosensitivity of leukemia cells by attenuating NF-кB pathway activity and DNA damage response induced by Idarubicin

Idarubicin (IDA), an anthracycline antineoplastic drug, is commonly used in the treatment of acute myeloid leukemia (AML) with reasonable response rates and clinical benefits. However, some patients still relapse, or do not respond, and suffer high fatality rates. Recent studies have shown that overexpression of PARP-1 may represent an important risk factor in AML patients. The aim of the present study was to determine the underlying molecular mechanisms by which the PARP-1 inhibitor Olaparib enhances the chemosensitivity of the leukemia cell line K562 and THP1 to IDA. Our data demonstrated that PARP-1 is upregulated in AML patients as well as in K562 and THP1 cells, and that the suppression of PARP-1 activity by Olaparib enhances the inhibitory effect of IDA. A mechanistic study revealed that Olaparib decreases the expressions of p-ATM, p-IκBα, XIAP and p65, and upregulates Bax, cleaved-Caspase-3 and γ-H2AX. Olaparib can enhance the induction of DNA damage by IDA, probably mediated by the inhibition of the ATM-related DNA damage response. Moreover, we also found that the nuclear translocation of p65 and the nuclear export of NEMO are inhibited when IDA and Olaparib are combined. Our results suggest that Olaparib attenuates the activity of the NF-κB pathway and decreases the DNA damage response induced by IDA. Therefore, we conclude that Olaparib is a potentially valuable chemosensitizer for leukemia patients.

A novel dipeptide type inhibitor of the Wnt/ß-catenin pathway suppresses proliferation of acute myelogenous leukemia cells.

The Wnt/ß-catenin pathway is an attractive target for the treatment of acute myelogenous leukemia (AML), since aberrant activation of the Wnt/ß-catenin pathway contributes to carcinogenesis in various types of cancers including AML. Screening of an in-house compound library, constructed at Kyoto Pharmaceutical University, identified a novel compound designated "31" that was found to be an inhibitor of the Wnt/ß-catenin pathway. The compound inhibited T-cell factor (TCF) activity in a TCF firefly luciferase-reporter assay and suppressed the proliferation of several human AML cell lines in a dose-dependent manner. Compound 31 arrested the cell cycle of AML cells at the G1 stage and induced apoptosis. Decrease in protein and mRNA expression level of Wnt pathway-related molecules was confirmed by the analyses of western blotting and quantitative reverse transcription-polymerase chain reaction. In addition, compound 31 combined with idarubicin synergistically inhibited the proliferation of AML cells. In conclusion, these results strongly suggest that compound 31 has potential as a novel anti-AML agent targeting the Wnt/ß-catenin signaling pathway.

Anthracycline-induced cytotoxicity in the GL261 glioma model system.

Glioblastoma (GBM) is a lethal astrocyte-derived tumor that is currently treated with a multi-modal approach of surgical resection, radiotherapy, and temozolomide-based chemotherapy. Alternatives to current therapies are urgently needed as its prognosis remains poor. Anthracyclines are a class of compounds that show great potential as GBM chemotherapeutic agents and are widely used to treat solid tumors outside the central nervous system. Here we investigate the cytotoxic effects of doxorubicin and other anthracyclines on GL261 glioma tumor cells in anticipation of novel anthracycline-based CNS therapies. Three methods were used to quantify dose-dependent effects of anthracyclines on adherent GL261 tumor cells, a murine cell-based model of GBM. MTT assays quantified anthracycline effects on cell viability, comet assays examined doxorubicin genotoxicity, and flow cytometry with Annexin V/PI staining characterized doxorubicin-induced apoptosis and necrosis. Dose-dependent reductions in GL261 cell viability were found in cells treated with doxorubicin (EC50 = 4.9 µM), epirubicin (EC50 = 5.9 µM), and idarubicin (EC50 = 4.4 µM). Comet assays showed DNA damage following doxorubicin treatments, peaking at concentrations of 1.0 µM and declining after 25 µM. Lastly, flow cytometric analysis of doxorubicin-treated cells showed dose-dependent induction of apoptosis (EC50 = 5.2 µM). Together, these results characterized the cytotoxic effects of anthracyclines on GL261 glioma cells. We found dose-dependent apoptotic induction; however at high concentrations we find that cell death is likely necrotic. Our results support the continued exploration of anthracyclines as compounds with significant potential for improved GBM treatments.

Structure-based drug repurposing to inhibit the DNA gyrase of Mycobacterium tuberculosis.

Drug repurposing is an alternative avenue for identifying new drugs to treat tuberculosis (TB). Despite the broad-range of anti-tubercular drugs, the emergence of multi-drug-resistant and extensively drug-resistant strains of Mycobacterium tuberculosis (Mtb) H37Rv, as well as the significant death toll globally, necessitates the development of new and effective drugs to treat TB. In this study, we have employed a drug repurposing approach to address this drug resistance problem by screening the drugbank database to identify novel inhibitors of the Mtb target enzyme, DNA gyrase. The compounds were screened against the ATPase domain of the gyrase B subunit (MtbGyrB47), and the docking results showed that echinacoside, doxorubicin, epirubicin, and idarubicin possess high binding affinities against MtbGyrB47. Comprehensive assessment using fluorescence spectroscopy, surface plasmon resonance spectroscopy (SPR), and circular dichroism (CD) titration studies revealed echinacoside as a potent binder of MtbGyrB47. Furthermore, ATPase, and DNA supercoiling assays exhibited an IC50 values of 2.1-4.7 µM for echinacoside, doxorubicin, epirubicin, and idarubicin. Among these compounds, the least MIC90 of 6.3 and 12 µM were observed for epirubicin and echinacoside, respectively, against Mtb. Our findings indicate that echinacoside and epirubicin targets mycobacterial DNA gyrase, inhibit its catalytic cycle, and retard mycobacterium growth. Further, these compounds exhibit potential scaffolds for optimizing novel anti-mycobacterial agents that can act on drug-resistant strains.

Co-Treatments of Edible Curcumin from Turmeric Rhizomes and Chemotherapeutic Drugs on Cytotoxicity and FLT3 Protein Expression in Leukemic Stem Cells.

This study aims to enhance efficacy and reduce toxicity of the combination treatment of a drug and curcumin (Cur) on leukemic stem cell and leukemic cell lines, including KG-1a and KG-1 (FLT3+ LSCs), EoL-1 (FLT3+ LCs), and U937 (FLT3- LCs). The cytotoxicity of co-treatments of doxorubicin (Dox) or idarubicin (Ida) at concentrations of the IC10-IC80 values and each concentration of Cur at the IC20, IC30, IC40, and IC50 values (conditions 1, 2, 3, and 4) was determined by MTT assays. Dox-Cur increased cytotoxicity in leukemic cells. Dox-Cur co-treatment showed additive and synergistic effects in several conditions. The effect of this co-treatment on FLT3 expression in KG-1a, KG-1, and EoL-1 cells was examined by Western blotting. Dox-Cur decreased FLT3 protein levels and total cell numbers in all the cell lines in a dose-dependent manner. In summary, this study exhibits a novel report of Dox-Cur co-treatment in both enhancing cytotoxicity of Dox and inhibiting cell proliferation via FLT3 protein expression in leukemia stem cells and leukemic cells. This is the option of leukemia treatment with reducing side effects of chemotherapeutic drugs to leukemia patients.

Radotinib enhances cytarabine (Ara-C)-induced acute myeloid leukemia cell death.

BACKGROUND: Acute myeloid leukemia (AML) is a heterogeneous disease that frequently relapses after standard chemotherapy. Therefore, there is a need for the development of novel chemotherapeutic agents that could treat AML effectively. Radotinib, an oral BCR-ABL tyrosine kinase inhibitor, was developed as a drug for the treatment of chronic myeloid leukemia. Previously, we reported that radotinib exerts increased cytotoxic effects towards AML cells. However, little is known about the effects of combining radotinib with Ara-C, a conventional chemotherapeutic agent for AML, with respect to cell death in AML cells. Therefore, we investigated combination effects of radotinib and Ara-C on AML in this study. METHODS: Synergistic anti-cancer effects of radotinib and Ara-C in AML cells including HL60, HEL92.1.7, THP-1 and bone marrow cells from AML patients have been examined. Diverse cell biological assays such as cell viability assay, Annexin V-positive cells, caspase-3 activity, cell cycle distribution, and related signaling pathway have been performed. RESULTS: The combination of radotinib and Ara-C was found to induce AML cell apoptosis, which involved the mitochondrial pathway. In brief, combined radotinib and Ara-C significantly induced Annexin V-positive cells, cytosolic cytochrome C, and the pro-apoptotic protein Bax in AML cells including HL60, HEL92.1.7, and THP-1. In addition, mitochondrial membrane potential and Bcl-xl protein were markedly decreased by radotinib and Ara-C. Moreover, this combination induced caspase-3 activity. Cleaved caspase-3, 7, and 9 levels were also increased by combined radotinib and Ara-C. Additionally, radotinib and Ara-C co-treatment induced G0/G1 arrest via the induction of CDKIs such as p21 and p27 and the inhibition of CDK2 and cyclin E. Thus, radotinib/Ara-C induces mitochondrial-dependent apoptosis and G0/G1 arrest via the regulation of the CDKI-CDK-cyclin cascade in AML cells. In addition, our results showed that combined treatment with radotinib and Ara-C inhibits AML cell growth, including tumor volumes and weights in vivo. Also, the combination of radotinib and Ara-C can sensitize cells to chemotherapeutic agents such as daunorubicin or idarubicin in AML cells. CONCLUSIONS: Therefore, our results can be concluded that radotinib in combination with Ara-C possesses a strong anti-AML activity.

Idarubicin Stimulates Cell Cycle- and TET2-Dependent Oxidation of DNA 5-Methylcytosine in Cancer Cells.

The topoisomerase II inhibitor idarubicin (Ida) is an effective anticancer anthracycline drug and has been used for clinical therapies of multiple cancers. It is well-known that Ida and its analogues can induce DNA double strand breakage (DSB) by inhibiting topoisomer II and kill tumor cells. To date, it remains unknown whether they alter DNA epigenomes. Here, we show that Ida significantly stimulates the oxidation of a key epigenetic mark DNA 5-methyl-2'-deoxycytidine (5mC), which results in elevation of 5-hydroxymethyl-2'-deoxycytidine (5hmC) in four tested cell lines. Similarly, Ida analogues also display elevated 5hmC. DSB-causing topoisomer II inhibitor etopside fails to induce 5hmC change even at very high dose, which suggests the independence of the DSB. Moreover, the structure comparison supports that the histone eviction-associated amino sugar moiety is a characteristic of the anthracyclines required to promote the 5hmC elevation. Noteworthy, we also found that the 5mC oxidation is also cell-cycle dependent and mainly occurs during the S and G2/M phases. TET2 depletion diminishes the observed 5hmC elevation, which suggests that the Ida stimulation of 5hmC formation is mainly TET2-dependent. Deep-sequencing shows that 5hmC increases in all regions of the tested genome of T47D cells. The observation of a novel effect of Ida as well as other anthracycline compounds on epigenetic DNA modifications may help to further elucidate their biological and clinical effects.

Final results of a phase 2, open-label study of indisulam, idarubicin, and cytarabine in patients with relapsed or refractory acute myeloid leukemia and high-risk myelodysplastic syndrome.

BACKGROUND: Indisulam possesses anticancer properties through down-regulation of various cell-cycle checkpoint molecules, thereby blocking the phosphorylation of retinoblastoma protein and inducing p53 and p21. Indisulam exhibits synergy with nucleoside analogs and topoisomerase inhibitors. METHODS: The authors designed a phase 2 study of indisulam in combination with idarubicin and cytarabine in patients who had relapsed/refractory acute myeloid leukemia AML and high-risk myelodysplastic syndrome. In stage 1, patients received intravenous indisulam at 400 mg/m2 on days 1 and 8 of a 28-day cycle. If they had no response, then patients received same dose schedule of indisulam followed by intravenous idarubicin 8 mg/m2 daily for 3 days and cytarabine 1.0 g/m2 over 24 hours daily on days 9 through 12 (for those aged < 60 years) or days 9 through 11 (for those aged > 60 years) of a 28-day cycle. Primary endpoints included the overall response rate, and secondary objectives included overall survival. RESULTS: Forty patients were enrolled. Of the 37 evaluable patients, 31 received indisulam with chemotherapy. Of these, 11 (35%) responded for a median duration of 5.3 months. The estimated 1-year overall survival rate was 51% for responders compared with 8 % for nonresponders (P < .001). The most common grade ≥3 nonhematologic toxicities were electrolyte abnormalities (50%) and febrile neutropenia (28%). CONCLUSIONS: The combination of indisulam with idarubicin and cytarabine yielded a 35% response rate in heavily pretreated patients with AML. With emerging data identifying the expression of DCAF15 (DDB1 and CUL4-associated factor 15) as a potential biomarker for activity, the combination of indisulam with idarubicin and cytarabine should be studied in a biomarker-driven trial or in patients who have splicing factor mutations. Cancer 2018;124:2758-65. © 2018 American Cancer Society. Cancer 2018;124:2758-2765. © 2018 American Cancer Society.

A distinct subset of self-renewing human memory CD8+ T cells survives cytotoxic chemotherapy.

The mechanisms that maintain human T cell memory during normal and perturbed homeostasis are not fully understood. The repeated induction of profound lymphocytopenia in patients undergoing multiple cycles of cytotoxic chemotherapy infrequently results in severe infections with viruses controlled by memory T cells, suggesting that some memory T cells survive chemotherapy and restore immunity. Here, we identified a distinct subpopulation of memory CD8(+) T cells with the ability to rapidly efflux and survive exposure to chemotherapy drugs in vitro and in vivo. T cells with high efflux capacity shared expression of molecules with hematopoietic stem cells, were quiescent in nonlymphocytopenic individuals, and were induced to proliferate in patients rendered lymphocytopenic after chemotherapy. Effluxing T cells differentiated into noneffluxing subsets in response to antigen stimulation and inflammatory signals, thereby contributing to repopulation of memory cells after chemotherapy.

Overexpression of TEL-MN1 Fusion Enhances Resistance of HL-60 Cells to Idarubicin.

BACKGROUND: The translocation t(12; 22) (p13;q12) is a recurrent but infrequent chromosome abnormality in human myeloid malignancies. To date, the role of TEL-MN1 fusion in leukemogenic process and drug resistance is still largely unknown. METHODS: In the present study, the TEL-MN1 fusion was transfected into HL-60 cells to upregulate TEL-MN1 expression via a retroviral vector. MTT assay was employed to examine cell viability and flow cytometry was performed to evaluate cell apoptosis. Idarubicin was used to treat HL-60 cells for estimating the effect of TEL-MN1 fusion on the chemotherapy resistance. RESULTS: The results showed that overexpression of TEL-MN1 in HL-60 cells could promote cell proliferation, suggesting that TEL-MN1 may be involved in the leukemogenesis process. HL-60 cells treated with idarubicin showed a weakened cell viability, whereas TEL-MN1 overexpression attenuated the idarubicin-induced inhibition of cell viability and acceleration of cell apoptosis of HL-60 cells. CONCLUSION: Taken together, our results indicated that TEL-MN1 fusion is an oncogene involved in the leukemogenesis process and TEL-MN1 overexpression enhanced resistance of HL-60 cells to idarubicin, which may provide a useful tool for studying the mechanism of leukemogenesis and drug resistance.

The polysialic acid mimetics idarubicin and irinotecan stimulate neuronal survival and neurite outgrowth and signal via protein kinase C.

Polysialic acid (PSA) is a large, negatively charged, linear homopolymer of alpha2-8-linked sialic acid residues. It is generated by two polysialyltransferases and attached to N- and/or O-linked glycans, and its main carrier is the neural cell adhesion molecule (NCAM). PSA controls the development and regeneration of the nervous system by enhancing cell migration, axon pathfinding, synaptic targeting, synaptic plasticity, by regulating the differentiation of progenitor cells and by modulating cell-cell and cell-matrix adhesions. In the adult, PSA plays a role in the immune system, and PSA mimetics promote functional recovery after nervous system injury. In search for novel small molecule mimetics of PSA that are applicable for therapy, we identified idarubicin, an antineoplastic anthracycline, and irinotecan, an antineoplastic agent of the topoisomerase I inhibitor class, as PSA mimetics using a competition enzyme-linked immunosorbent assay. Idarubicin and irinotecan compete with the PSA-mimicking peptide and colominic acid, the bacterial analog of PSA, for binding to the PSA-specific monoclonal antibody 735. Idarubicin and irinotecan stimulate neurite outgrowth and survival of cultured cerebellar neurons after oxidative stress via protein kinase C and Erk1/2 in a similar manner as colominic acid, whereas Fyn, casein kinase II and the phosphatase and tensin homolog are only involved in idarubicin and irinotecan-stimulated neurite outgrowth. These novel results show that the structure and function of PSA can be mimicked by the small organic compounds irinotecan and idarubicin which trigger the same signaling cascades as PSA, thus introducing the possibility of retargeting these drugs to treat nervous system injuries.

Idarubicin is a broad-spectrum enterovirus replication inhibitor that selectively targets the virus internal ribosomal entry site.

Enterovirus 71 (EV71) causes life-threatening diseases with neurological manifestations in young children. However, the treatment of EV71 infections remains an unmet medical need. Idarubicin (IDR) is an anthracycline compound that is used therapeutically for certain types of tumour. In this study, we identified IDR as an EV71 inhibitor, which displayed antiviral potency in the submicromolar range and substantially protected cells from the cytopathic effects and cell death caused by EV71 infections. The antiviral effects extended to several other enterovirus (EV) species, and these effects were independent of cytotoxicity or topoisomerase inhibition. Structure-activity relationship studies indicated the importance of the anthracycline scaffold for anti-EV potency. IDR effectively blocked the synthesis of viral protein and RNA, but not the viral proteolysis processes. Moreover, anthracyclines were demonstrated to suppress EV internal ribosomal entry site (IRES)-mediated translation; conversely, the cellular p53 IRES activity was not sensitive to IDR action. Inhibition of IRES-mediated translation by IDR correlated with the affinity of binding between IDR and the particular IRES. Moreover, IDR impaired binding between the EV71 IRES RNA and hnRNP A1, a known host IRES trans-acting factor. In sum, we have identified a USA FDA-approved anticancer drug with the new indication as a selective EV IRES binder and inhibitor. The finding may also provide leads for the development of novel antiviral therapies directed at the EV IRES RNA.

Genomic and transcriptomic profiles and in vitro resistance to mitoxantrone and idarubicin in pediatric acute leukemias.

BACKGROUND: A major problem in the treatment of leukemia is the development of drug resistance to chemotherapeutic agents. METHODS: To determine the ex vivo drug resistance profile to anthracyclines, an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cytotoxicity assay was performed on mononuclear cells obtained from 155 patients with acute lymphoblastic leukemia (ALL) or acute myeloblastic leukemia (AML). Gene expression profiles (for 51 patients with ALL and 16 with AML) were prepared on the basis of cRNA hybridization to oligonucleotide arrays of the human genome (Affymetrix). Hierarchical clustering, assignment location and biological function were investigated during the correlation analysis for identified probe sets. Comparative genomic hybridization (CGH) array profiles (34 patients with ALL and 12 with AML) were prepared on the basis of DNA hybridization to oligonucleotide arrays of the human genome (Agilent). The validation of the array results was performed by a quantitative reverse transcriptase polymerase chain reaction. RESULTS: The collected expression and CGH microarray experiment results indicate that the ITGB2, SCL6A7, CASP1 and DUSP genes may comprise a resistance marker for acute leukemia cells correlated with anthracyclines. Moreover, there were also identified chromosome rearrangements associated with drug resistance, such as del5q32-35.3 and amp8p12-p11.21. Precise genes, as well as genome aberrations, might be classified as targets in therapy. CONCLUSIONS: In AML, the resistance of blasts to idarubicin and mitoxantrone may reflect an impaired integrin pathway. In ALL, the development of resistance is caused by the inhibition of B and T cell activation. Copyright © 2016 John Wiley & Sons, Ltd.

Analysis to Estimate Genetic Variations in the Idarubicin-Resistant Derivative MOLT-3.

Gene alterations are a well-established mechanism leading to drug resistance in acute leukemia cells. A full understanding of the mechanisms of drug resistance in these cells will facilitate more effective chemotherapy. In this study, we investigated the mechanism(s) of drug resistance in the human acute leukemia cell line MOLT-3 and its idarubicin-resistant derivative MOLT-3/IDR through complete mitochondrial and nuclear DNA analyses. We identified genetic differences between these two cell lines. The ND3 mutation site (p.Thr61Ile) in the mitochondrial DNA sequence was unique to MOLT-3/IDR cells. Moreover, we identified five candidate genes harboring genetic alterations, including GALNT2, via CGH array analysis. Sequencing of the GALNT2 exon revealed a G1716K mutation present within the stop codon in MOLT-3/IDR cells but absent from MOLT-3 cells. This mutation led to an additional 18 amino acids in the protein encoded by GALNT2. Using real-time PCR, we determined an expression value for this gene of 0.35. Protein structure predictions confirmed a structural change in GALNT2 in MOLT-3/IDR cells that corresponded to the site of the mutation. We speculate that this mutation may be related to idarubicin resistance.

Idarubicin induces mTOR-dependent cytotoxic autophagy in leukemic cells.

We investigated if the antileukemic drug idarubicin induces autophagy, a process of programmed cellular self-digestion, in leukemic cell lines and primary leukemic cells. Transmission electron microscopy and acridine orange staining demonstrated the presence of autophagic vesicles and intracellular acidification, respectively, in idarubicin-treated REH leukemic cell line. Idarubicin increased punctuation/aggregation of microtubule-associated light chain 3B (LC3B), enhanced the conversion of LC3B-I to autophagosome-associated LC3B-II in the presence of proteolysis inhibitors, and promoted the degradation of the selective autophagic target p62, thus indicating the increase in autophagic flux. Idarubicin inhibited the phosphorylation of the main autophagy repressor mammalian target of rapamycin (mTOR) and its downstream target p70S6 kinase. The treatment with the mTOR activator leucine prevented idarubicin-mediated autophagy induction. Idarubicin-induced mTOR repression was associated with the activation of the mTOR inhibitor AMP-activated protein kinase and down-regulation of the mTOR activator Akt. The suppression of autophagy by pharmacological inhibitors or LC3B and beclin-1 genetic knockdown rescued REH cells from idarubicin-mediated oxidative stress, mitochondrial depolarization, caspase activation and apoptotic DNA fragmentation. Idarubicin also caused mTOR inhibition and cytotoxic autophagy in K562 leukemic cell line and leukocytes from chronic myeloid leukemia patients, but not healthy controls. By demonstrating mTOR-dependent cytotoxic autophagy in idarubicin-treated leukemic cells, our results warrant caution when considering combining idarubicin with autophagy inhibitors in leukemia therapy.

Sequential combination of decitabine and idarubicin synergistically enhances anti-leukemia effect followed by demethylating Wnt pathway inhibitor promoters and downregulating Wnt pathway nuclear target.

BACKGROUND: The methylation inhibitor 5-Aza-2'-deoxycytidine (decitabine, DAC) has a great therapeutic value for acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS). But decitabine monotherapy was associated with a relatively low rate of complete remission in AML and MDS. We aimed to investigate the effect of several anti-leukemia drugs in combination with decitabine on the proliferation of myeloid leukemia cells, to select the most efficient combination group and explore the associated mechanisms of these combination therapies. METHODS: Cell proliferation was tested by MTT assay and CFU-GM assay. Cell apoptosis was evaluated by Annexin V and PI staining in cell culture, TUNEL assay and transmission electron microscopy in animal study. MicroPET was used to imaging the tumor in mouse model. Molecular studies were conducted using microarray expression analysis, which was used to explore associated pathways, and real-time quantitative reverse transcription-PCR, western blot and immunohistochemistry, used to assess regulation of Wnt/ß-catenin pathway. Statistical significance among groups was determined by one-way ANOVA analysis followed by post hoc Bonferroni's multiple comparison test. RESULTS: Among five anti-leukemia agents in combining with decitabine, the sequential combination of decitabine and idarubicin induced synergistic cell death in U937 cells, and this effect was verified in HEL, SKM-1 cells and AML cells isolated from AML patients. Importantly, tumor growth inhibition in this sequential combination was found to be higher than in single agent or controls in vivo. Moreover, sequential combination of the two agents induced apoptosis and depression of the Wnt/ß-catenin pathway in both AML cell culture and animal studies. CONCLUSIONS: The findings demonstrated that sequentially combination of decitabine and idarubicin had synergistic anti-leukemia effects. These effects were mainly attributed to demethylation of Wnt/ß-catenin pathway inhibitors and downregulation of Wnt/ß-catenin pathway nuclear targets.

Anthracycline resistance mediated by reductive metabolism in cancer cells: the role of aldo-keto reductase 1C3.

Pharmacokinetic drug resistance is a serious obstacle that emerges during cancer chemotherapy. In this study, we investigated the possible role of aldo-keto reductase 1C3 (AKR1C3) in the resistance of cancer cells to anthracyclines. First, the reducing activity of AKR1C3 toward anthracyclines was tested using incubations with a purified recombinant enzyme. Furthermore, the intracellular reduction of daunorubicin and idarubicin was examined by employing the transfection of A549, HeLa, MCF7 and HCT 116 cancer cells with an AKR1C3 encoding vector. To investigate the participation of AKR1C3 in anthracycline resistance, we conducted MTT cytotoxicity assays with these cells, and observed that AKR1C3 significantly contributes to the resistance of cancer cells to daunorubicin and idarubicin, whereas this resistance was reversible by the simultaneous administration of 2'-hydroxyflavanone, a specific AKR1C3 inhibitor. In the final part of our work, we tracked the changes in AKR1C3 expression after anthracycline exposure. Interestingly, a reciprocal correlation between the extent of induction and endogenous levels of AKR1C3 was recorded in particular cell lines. Therefore, we suggest that the induction of AKR1C3 following exposure to daunorubicin and idarubicin, which seems to be dependent on endogenous AKR1C3 expression, eventually might potentiate an intrinsic resistance given by the normal expression of AKR1C3. In conclusion, our data suggest a substantial impact of AKR1C3 on the metabolism of daunorubicin and idarubicin, which affects their pharmacokinetic and pharmacodynamic behavior. In addition, we demonstrate that the reduction of daunorubicin and idarubicin, which is catalyzed by AKR1C3, contributes to the resistance of cancer cells to anthracycline treatment.

Metformin as an Enhancer for the Treatment of Chemoresistant CD34+ Acute Myeloid Leukemia Cells.

Acute myeloid leukemia is the second most frequent type of leukemia in adults. Due to a high risk of development of chemoresistance to first-line chemotherapy, the survival rate of patients in a 5-year period is below 30%. One of the reasons is that the AML population is heterogeneous, with cell populations partly composed of very primitive CD34+CD38- hematopoietic stem/progenitor cells, which are often resistant to chemotherapy. First-line treatment with cytarabine and idarubicin fails to inhibit the proliferation of CD34+CD38- cells. In this study, we investigated Metformin's effect with or without first-line conventional chemotherapy, or with other drugs like venetoclax and S63845, on primitive and undifferentiated CD34+ AML cells in order to explore the potential of Metformin or S63845 to serve as adjuvant therapy for AML. We found that first-line conventional chemotherapy treatment inhibited the growth of cells and arrested the cells in the S phase of the cell cycle; however, metformin affected the accumulation of cells in the G2/M phase. We observed that CD34+ KG1a cells respond better to lower doses of cytarabine or idarubicin in combination with metformin. Also, we determined that treatment with cytarabine, venetoclax, and S63845 downregulated the strong tendency of CD34+ KG1a cells to form cell aggregates in culture due to the downregulation of leukemic stem cell markers like CD34 and CD44, as well as adhesion markers. Also, we found that idarubicin slightly upregulated myeloid differentiation markers, CD11b and CD14. Treatment with cytarabine, idarubicin, venetoclax, metformin, and S63845 upregulated some cell surface markers like HLA-DR expression, and metformin upregulated CD9, CD31, and CD105 cell surface marker expression. In conclusion, we believe that metformin has the potential to be used as an adjuvant in the treatment of resistant-to-first-line-chemotherapy AML cells. Also, we believe that the results of our study will stimulate further research and the potential use of changes in the expression of cell surface markers in the development of new therapeutic strategies.