phenanthrenes and Leukemia--Myelogenous--Chronic--BCR-ABL-Positive

A portion of patients with chronic myeloid leukaemia (CML) develop resistance to the Bcr-Abl tyrosine kinase inhibitors (TKIs), limiting the clinical applications. Previous results have demonstrated the synergistic effects between cryptotanshinone (CPT) and imatinib on apoptosis of CML cells. To determine the antileukemia effects of CPT and TKIs on the resistant CML cells, and further investigate the effect of combined treatment of CPT and imatinib on tumour growth and apoptosis in the xenograft model and clarify its regulatory mechanisms.. The combination effects of CPT and second-generation TKIs were evaluated in resistant CML cells K562-R. CPT and imatinib were orally administered once daily for 21 days on K562-R xenografts in nude mice (6 per group). Tumour proliferation and apoptosis were examined by Ki-67, PCNA and TUNEL staining. The expression levels of apoptotic markers and activities of STAT3 and eIF4E pathways were determined via immunohistochemistry staining and western blotting analysis.. CPT significantly enhanced the antiproliferative effects of TKIs, via triggering cleavages of caspase proteins, and inhibiting activities of STAT3 and eIF4E pathways. The administration of CPT and imatinib dramatically inhibited the tumour growth of xenografts and achieved a suppression of 60.2%, which is 2.6-fold higher than that of single imatinib group. Furthermore, CPT and imatinib increased the apoptotic rates and markedly decreased the phosphorylation levels of STAT3 and eIF4E.. Our results demonstrated that CPT could significantly enhance the antileukemia efficacy of TKIs, suggesting the therapeutic potential of CPT to overcome CML resistance.

Topics: Animals; Apoptosis; Cell Proliferation; Drug Resistance, Neoplasm; Drug Synergism; Eukaryotic Initiation Factor-4E; Female; Humans; Imatinib Mesylate; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Mice; Mice, Nude; Phenanthrenes; Phosphorylation; Protein Kinase Inhibitors; Signal Transduction; STAT3 Transcription Factor; Xenograft Model Antitumor Assays

C-Myc and signal transducer and activator of transcription (STAT) family proteins have been proposed to be important downstream genes of BCR-ABL, which characterizes most cases of chronic myeloid leukemia (CML). Here, we report a c-Myc pathway-targeted screening of seven natural anticancer compounds, in which we identified cryptotanshinone as a highly promising agent for CML therapy. Cryptotanshinone depletes c-Myc in CML by repressing the phosphorylation of STAT5. Decreased viability of K562 cells correlated with p-STAT5 suppression. Unexpectedly, imatinib activates rather than inhibits the phosphorylation of STAT3 in K562 cells. We demonstrated that cryptotanshinone, as a dual inhibitor of p-STAT5 and p-STAT3, can effectively block IL-6-mediated STAT3 activation and reverse BCR-ABL kinase-independent drug resistance. Moreover, we showed that the epigenetic rebalance between decreased BCR-ABL/STAT5/c-Myc and enhanced STAT3/multi-drug resistance (MDR) pathways is characteristic of the cancer stem cell-like property of K562/ADR. Simultaneously suppressing these two pathways using cryptotanshinone proves to be critical for the malignant network redress and MDR reversal of K562/ADR. These studies reveal the dual functions of cryptotanshinone that suppress key oncogenic proliferation and drug-resistant pathways in CML cells by targeting p-STAT5 and p-STAT3, providing a new strategy for CML therapy that takes advantage of natural products.

Topics: Antineoplastic Agents; Cell Proliferation; Drug Resistance, Neoplasm; Gene Expression Regulation, Leukemic; Humans; Imatinib Mesylate; Interleukin-6; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Neoplastic Stem Cells; Phenanthrenes; Phosphorylation; Proto-Oncogene Proteins c-myc; STAT3 Transcription Factor; STAT5 Transcription Factor

Imatinib resistance has emerged as a significant clinical problem in chronic myeloid leukemia (CML) treatment. In this study, we investigated the effect and mechanism of combination treatment with imatinib and cryptotanshinone (CPT) in CML cells. Cotreatment with imatinib and CPT showed a significant synergistic killing effect in both imatinib sensitive and resistant CML cell lines, as well as primary CML cells. Furthermore, combination treatment induced apoptosis significantly, as indicated by increases in apoptotic cell fraction and activities of proapoptotic proteins. Subsequent studies revealed that CPT significantly inhibited Bcr/Abl protein expression, as well as phosphorylation expression levels of signal transducer and activator of transcription 3 (STAT3), mammalian target of rapamycin (mTOR) and eukaryotic translation initiation factor 4E (eIF4E), which are critical mediators of Bcr/Abl transformation. Furthermore, CPT in combination with imatinib dramatically decreased the activity of the Bcr/Abl pathway in both K562 and K562-R cells. Our results demonstrated that CPT increased imatinib-induced apoptosis in a Bcr/Abl dependent manner, suggesting a novel strategy for the treatment of CML.

Topics: Apoptosis; Blotting, Western; Cell Survival; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Drug Synergism; Drugs, Chinese Herbal; Eukaryotic Initiation Factor-4E; Fusion Proteins, bcr-abl; Gene Expression Regulation, Neoplastic; Humans; Imatinib Mesylate; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Phenanthrenes; Phosphorylation; Protein Kinase Inhibitors; Reverse Transcriptase Polymerase Chain Reaction; STAT3 Transcription Factor; TOR Serine-Threonine Kinases; Tumor Cells, Cultured

Cryptotanshinone (CPT), a lipid soluble active compound in Salvia miltiorrhiza, has a significant inhibitory effect on multiple malignant tumors, e. g. chronic myeloid leukemia (CML) cells and can effectively enhance imatinib's chemotherapeutic effect. However, its functional molecular mechanism remained unclear. In this experiment, the authors conducted a systematic study on the effect of CPT on the imatinib sensitivity and P-glycoprotein (P-gp) expression in CML cells by using CML cells K562 and imatinib persister K562-R. The MTT assays were performed to determine CPT's impact on the inhibitory effect of imatinib. Annexin V-FITC/PI staining analysis was used to detect the changes in the cell apoptosis rate. The active changes in apoptosis regulatory proteins Caspase-3, Caspase-9 and PARP were determined by Western blot. After the cells were pretreated with the gradient concentration of CPT, the expression of P-gp was analyzed by Western blot and flow cytometry. The changes in intracellular concentrations of imatinib were determined by HPLC analysis. The results indicated that the pretreatment with CPT significantly increased the proliferation inhibiting and apoptosis inducing effects of imatinib on K562 and K562-R cells as well as the degradation product expression of pro-apoptotic proteins Caspase-3, Caspase-9 and PARP, with a significant difference with the control group (P < 0.01). However, CPT showed no impact on the P-gp expression in CML cells and the intracellular concentrations of imatinib. In summary, the findings suggested that CPT enhanced the sensitivity of CML cells to imatinib. Its mechanism is not dependent on the inhibition in P-gp expression and the increase in intracellular drug concentration.

Topics: Antineoplastic Agents; Apoptosis; ATP Binding Cassette Transporter, Subfamily B, Member 1; Caspase 3; Caspase 9; Drug Resistance, Neoplasm; Drugs, Chinese Herbal; Humans; Imatinib Mesylate; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Phenanthrenes

Despite being highly effective for newly diagnosed chronic myeloid leukemia (CML), imatinib not only is inactive against quiescent CML stem cells, but also has limited activity against blast crisis (BC) CML. The relative activity of Bcr-Abl and the expression levels of antiapoptotic proteins in proliferating and quiescent CD34(+) BC CML progenitor cells and the effects of targeting antiapoptotic proteins in these cells are unknown. Here we report higher levels of p-CrkL in quiescent than in proliferating CD34(+) progenitor cells and comparable expression levels of Bcl-2, Bcl-xL, Mcl-1 and XIAP in the two populations in BC CML. Inhibition of Bcl-2/Bcl-xL by ABT-737 in cells from patients with tyrosine kinase inhibitor (TKI)-resistant BC CML promoted apoptosis in quiescent CD34(+) progenitor cells with an efficacy similar to that in proliferating cells. Combination of ABT-737 with imatinib (which decreases Mcl-1 levels) or triptolide (which decreases Mcl-1 and XIAP) synergistically induced death of both proliferating and quiescent CD34(+) progenitor cells obtained from TKI-resistant BC CML patients. These results suggest that antiapoptotic proteins are critical targets in BC CML and that activation of apoptosis signaling can eliminate both proliferating and quiescent CD34(+) progenitor cells in BC CML, independent of response to TKIs.

Topics: Antigens, CD34; Apoptosis; Benzamides; Biphenyl Compounds; Blast Crisis; Cell Line, Tumor; Diterpenes; Epoxy Compounds; Fusion Proteins, bcr-abl; Hematopoietic Stem Cells; Humans; Imatinib Mesylate; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Nitrophenols; Phenanthrenes; Piperazines; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-bcl-2; Pyrimidines; RNA, Messenger; Signal Transduction; Sulfonamides

This study has investigated the growth-inhibitory and apoptosis-inducing effects of dihydrotanshinone, tanshinone I, tanshinone IIA, and cryptotanshinone on hematological malignancy cell lines, aiming to explore their structure-activity relationship. The growth-inhibitory effects of the tanshinones on K562 and Raji cells were assessed using a modified MTT assay; the apoptosis-inducing effects were assessed by fluorescence microscopy and flow cytometry analysis. The changes in cellular morphology were observed using an inverted phase-contrast microscope. MTT results revealed that these tanshinones inhibited cell proliferation in a concentration-dependent and time-dependent manner. The IC50 values of dihydrotanshinone, tanshinone I, tanshinone IIA, and cryptotanshinone for K562 cells were 3.50, 13.52, 19.32, and 47.52 μmol/l at 24 h; 1.36, 4.70, 5.67, and 22.72 μmol/l at 48 h; and 1.15, 1.59, 2.82, and 19.53 μmol/l at 72 h, and the values for Raji cells were 3.30, 4.37, 12.92, and 52.36 μmol/l at 24 h; 1.55, 1.71, 6.54, and 25.45 μmol/l at 48 h; and 1.07, 1.38, 1.89, and 18.47 μmol/l at 72 h. The flow cytometry analysis demonstrated that these tanshinones induced apoptosis of K562 cells in a concentration-dependent manner, and dihydrotanshinone as well as tanshinone I were more potent than tanshinone IIA and cryptotanshinone. Some noticeable apoptotic morphologies could be observed by fluorescence microscopy on tanshinones-treated Raji cells. Collectively, these tanshinones caused growth inhibition and apoptosis in hematological malignancy cell lines, with dihydrotanshinone being the most potent, followed by tanshinone I, tanshinone IIA, and cryptotanshinone. These results suggested that the structure of aromatic ring A enhanced the cytotoxicity and the structure of ring C may have contributed to the cytotoxicity, but the mechanisms need to be further investigated.

Topics: Abietanes; Antineoplastic Agents, Phytogenic; Apoptosis; Burkitt Lymphoma; Cell Line, Tumor; Dose-Response Relationship, Drug; Flow Cytometry; Humans; Inhibitory Concentration 50; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Microscopy, Fluorescence; Phenanthrenes; Structure-Activity Relationship; Time Factors

Cryptotanshinone (CPT), a diterpene quinone isolated from Salvia miltiorrhiza, is recently reported to have obvious anticancer activities against diverse cancer cells. However, the effect and regulatory mechanism of CPT remain unclear in human chronic myeloid leukemia (CML) cells. In this study, we investigated the antiproliferative activity of CPT on the multidrug resistant CML cells K562/ADM. Our results demonstrated that CPT decreased the cell viability of K562/ADM cells by inducing cell cycle arrest and apoptosis through suppressing the expression of cyclin D1 and Bcl-2. Further studies indicated that CPT mainly functions at post-transcriptional levels, suggesting the involvement of eukaryotic initiation factor 4E (eIF4E). CPT significantly reduced the expression and activity of eIF4E in K562/ADM cells. Overexpression of eIF4E obvious conferred resistance to the CPT antiproliferation and proapoptotic activity as well as the cyclin D1 and Bcl-2 expressions. Knockdown of eIF4E significantly reduced the inhibitory effect of CPT in K562/ADM, confirming the participation of eIF4E during CPT function process. More importantly, the relative inhibitory efficiency of CPT positively correlated with the reductions on eIF4E in primary CML specimens. These results demonstrated that CPT played antitumor roles in K562/ADM cells by inhibiting the eIF4E regulatory system. Our results provide a novel anticancer mechanism of CPT in human CML cells.

Topics: Apoptosis; Cell Cycle Checkpoints; Cyclin D1; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Eukaryotic Initiation Factor-4E; Gene Expression Regulation, Leukemic; Gene Knockdown Techniques; Humans; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Peptide Chain Initiation, Translational; Phenanthrenes; Proto-Oncogene Proteins c-bcl-2

Cryptotanshinone is a biologically active compound from the root of Salvia miltiorrhiza. In the present study, we investigated the molecular mechanisms by which cryptotanshinone is in synergy with tumor necrosis factor-alpha (TNF-α) for the induction of apoptosis in human chronic myeloid leukemia (CML) KBM-5 cells. The co-treatment of cryptotanshinone with TNF-α reduced the viability of the cells [combination index (CI) < 1]. Concomitantly, the co-treatment of cryptotanshinone and TNF-α elicited apoptosis, manifested by enhanced the number of terminal deoxynucleotide transferase-mediated dUTP-nick-end labeling (TUNEL)-positive cells, the sub-G1 cell populations, and the activation of caspase-8 and -3, in comparison with the treatment with either drug alone. The treatment with cryptotanshinone further suppressed TNF-α-mediated expression of c-FLIP(L), Bcl-x(L), but the increased level of tBid (a caspase-8 substrate). Furthermore, cryptotanshinone activated p38 but not NF-κB in TNF-α-treated KBM-5 cells. The addition of a specific p38 MAPK inhibitor SB203580 significantly attenuated cryptotanshinone/TNF-α-induced apoptosis. The combination treatment of cryptotanshinone and TNF-α also stimulated the reactive oxygen species (ROS) generation. N-acetyl-L-cysteine (NAC, a ROS scavenger) was not only able to block cryptotanshinone/TNF-α-induced ROS production but also the activation of caspase-8 and p38 MAPK. Overall, our findings suggest that cryptotanshinone can sensitize TNF-α-induced apoptosis in human myeloid leukemia KBM-5 cells, which appears through ROS-dependent activation of caspase-8 and p38.

Topics: Apoptosis; Cell Line, Tumor; Cell Survival; Drug Synergism; Enzyme Activation; Humans; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; MAP Kinase Kinase Kinases; NF-kappa B; Phenanthrenes; Proto-Oncogene Proteins; Reactive Oxygen Species; Signal Transduction; Tumor Necrosis Factor-alpha

Imatinib (STI571) is the frontline targeted-therapeutic agent for patients with chronic myelogenous leukemia (CML). However, resistance to imatinib due to point mutations in Bcr-Abl kinase domain is an emerging problem. We recently reported that triptolide (compound 1) could effectively kill CML cells including those harboring T315I mutant Bcr-Abl. In the present study, we designed a series of C-14 triptolide derivatives with C-14-hydroxyl substituted by different amine esters (3-18): 3-6 and 13 (by aliphatic chain amine esters); 7-9, 11, 12 and 15-18 (by alicyclic amine esters with different size), and 10 and 14 (by aralkylamine esters).The compounds were examined for their antineoplastic activity against CML cells (including KBM5-T315I cells) in terms of proliferation inhibition, apoptosis and signal transduction. Nude mouse xenograft model was also used to evaluate the in vivo activity. Compounds 2-9, 11-14, 17 and 18 exhibited a potent inhibitory activity against KBM5 and KBM5-T315I cells. This series of derivatives down-regulated Bcr-Abl mRNA. Compounds 4, 5, 8 and 9 were further examined for their impact on signaling and apoptosis with immunoblotting. Compound 5 was chosen for evaluation in a nude mouse xenograft model. The stereo-hindrance of C-14 group appeared to be responsible for the antitumor effect. The computational small molecule-protein docking analysis illustrated the possible interaction between compound 9 and RNA polymerase II. Our results suggest that this series of derivatives may be promising agents to overcome imatinib-resistance caused by the Bcr-Abl-T315I mutation.

Topics: Amino Acid Substitution; Animals; Antineoplastic Agents; Apoptosis; Benzamides; Binding Sites; Cell Line; Computer Simulation; Diterpenes; Down-Regulation; Drug Design; Drug Resistance, Neoplasm; Epoxy Compounds; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Mice; Mice, Nude; Phenanthrenes; Piperazines; Pyrimidines; RNA, Messenger; Signal Transduction; Water; Xenograft Model Antitumor Assays

Resistance to STI571 is an emerging problem for patients with chronic myelogenous leukemia (CML). Mutation in the kinase domain of Bcr-Abl is the predominant mechanism of the acquired resistance to STI571. In the present study, we investigated the effect of triptolide on cell survival or apoptosis in CML cells bearing Bcr-Abl-T315I or wild-type Bcr-Abl.. CML cell lines (KBM5 versus KBM5-T315I, BaF3-Bcr-Abl versus BaF3-Bcr-Abl-T315I) and primary cells from CML patients with clinical resistance to STI571 were treated with triptolide, and analyzed in terms of growth, apoptosis, and signal transduction. Nude mouse xenograft model was also used to evaluate the antitumor activity.. Triptolide potently down-regulated the mRNA and protein levels of Bcr-Abl independently of the caspase or proteosome activation in CML cells. It induced mitochondrial-dependent apoptosis in Bcr-Abl-T315I CML cells and primary cells from CML patients with clinical resistance to STI571. Additionally, triptolide inhibited the growth of STI571-sensitive KBM5 and STI571-resistant KBM5-T315I CML cells in nude mouse xenografts. Triptolide also down-regulated the expression of survivin, Mcl-1, and Akt in CML cells, which suggests that it may have multiple targets.. These findings suggest that triptolide is a promising agent to overcome STI571-resistant CML cells, and warrant a clinical trial of triptolide derivatives for CML with Bcr-Abl-T315I mutation.

Topics: Adolescent; Adult; Aged; Animals; Antineoplastic Agents, Alkylating; Apoptosis; Benzamides; Blotting, Western; Cell Cycle; Cell Proliferation; Diterpenes; Drug Resistance, Neoplasm; Epoxy Compounds; Female; Flow Cytometry; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; Immunoenzyme Techniques; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Male; Membrane Potential, Mitochondrial; Mice; Mice, Inbred BALB C; Mice, Nude; Middle Aged; Mutation; Myeloid Cell Leukemia Sequence 1 Protein; Phenanthrenes; Piperazines; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Pyrimidines; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Transcription, Genetic; Tripterygium; Tumor Cells, Cultured; Tumor Stem Cell Assay; Xenograft Model Antitumor Assays; Young Adult

The advent of Bcr-Abl tyrosine kinase inhibitors (TKI) has revolutionized the treatment of chronic myelogenous leukemia (CML). However, resistance evolves due to BCR-ABL mutations and other mechanisms. Furthermore, patients with blast crisis CML are less responsive and quiescent CML stem cells are insensitive to these inhibitors. We found that triptolide, a diterpenoid, at nanomolar concentrations, promoted equally significant death of KBM5 cells, a cell line derived from a Bcr-Abl-bearing blast crisis CML patient and KBM5STI571 cells, an imatinib-resistant KBM5 subline bearing the T315I mutation. Similarly, Ba/F3 cells harboring mutated BCR-ABL were as sensitive as Ba/F3Bcr-Abl(p210wt) cells to triptolide. Importantly, triptolide induced apoptosis in primary samples from blast crisis CML patients, who showed resistance to Bcr-Abl TKIs in vivo, with less toxicity to normal cells. Triptolide decreased X-linked inhibitor of apoptosis protein, Mcl-1, and Bcr-Abl protein levels in K562, KBM5, and KBM5STI571 cells and in cells from blast crisis CML patients. It sensitized KBM5, but not KBM5STI571, cells to imatinib. More importantly, triptolide also induced death of quiescent CD34(+) CML progenitor cells, a major problem in the therapy of CML with TKIs. Collectively, these results suggest that triptolide potently induces blast crisis CML cell death independent of the cellular responses to Bcr-Abl TKIs, suggesting that triptolide could eradicate residual quiescent CML progenitor cells in TKI-treated patients and benefit TKI-resistant blast crisis CML patients.

Topics: Antigens, CD34; Antineoplastic Agents, Alkylating; Apoptosis; Benzamides; Blast Crisis; Blotting, Western; Cell Line, Tumor; Diterpenes; Epoxy Compounds; Fusion Proteins, bcr-abl; Humans; Imatinib Mesylate; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Phenanthrenes; Piperazines; Protein-Tyrosine Kinases; Pyrimidines; Reverse Transcriptase Polymerase Chain Reaction

Interest in exploiting traditional medicines for prevention or treatment of cancer is increasing. Extracts from the herb Tripterygium wilfordii hook F have been used in China for centuries to treat immune-related disorders. Recently it was reported that triptolide, a purified compound from Tripterygium, possessed antitumor properties and induced apoptosis in a variety of malignant cell lines. K562 cells are usually resistant to apoptosis induction, probably because of the expression of bcr-abl, the hybrid gene characteristic of the Philadelphia chromosome t (9;22). Present studies demonstrate that triptolide inhibited K562 cells proliferation and induced apoptosis in a dose and time-dependent manner. The growth-inhibitory IC50 value for triptolide treatment was 40 ng/ml. Characteristic apoptotic features were confirmed by morphology, internucleosomal DNA fragmentation, and Annexin V Staining. Significantly, triptolide-induced apoptosis of K562 cells was associated with a decline in bcr-abl expression levels, at the concentrations of 20 ng/ml, 40 ng/ml and 80 ng/ml, triptolide was able to decrease the expression of bcr-abl down to 50%, 30% and 20% respectively of the basal value after 72 h. Our findings strongly suggest that triptolide might be an effective therapeutic agent against CML cells.

Topics: Annexin A5; Antineoplastic Agents; Antineoplastic Agents, Alkylating; Apoptosis; Blotting, Western; Cell Division; Cell Line, Tumor; Diterpenes; Dose-Response Relationship, Drug; Down-Regulation; Enzyme Inhibitors; Epoxy Compounds; Fusion Proteins, bcr-abl; Humans; Inhibitory Concentration 50; K562 Cells; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Phenanthrenes; Reverse Transcriptase Polymerase Chain Reaction; Time Factors; Translocation, Genetic