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At least 127 records · Page 7Linked to original sources
PubMed2006

The significance of aberrant CHFR methylation for clinical response to microtubule inhibitors in gastric cancer.

BACKGROUND: We studied the correlations between CHFR (checkpoint with FHA and RING finger) gene methylation and responses to microtubule inhibitors (MI) in gastric cancer. METHODS: We examined 9 gastric cancer cell lines and 46 gastric cancer specimens from patients who underwent surgical resection. Promoter methylation was determined by methylation-specific polymerase chain reaction (MSP). CHFR mRNA expression was estimated by quantitative reverse transcription-PCR. The MI-induced growth inhibition was assayed by a standard MTT method. RESULTS: CHFR expression was silenced by aberrant promoter methylation in 3 of 9 gastric cancer cell lines. The level of CHFR mRNA expression was closely correlated with IC(50) in the MI-treated cells (R=0.889, P=0.005). In 46 patients with gastric cancers, 24 (52%) presented aberrant CHFR methylation. Among them, 12 patients had received treatment with MI because of advanced-stage tumor or tumor recurrence after surgery. The responders to the MI treatment were 29% in patients with CHFR methylation and 20% in those without the methylation. However, 6 (86%) of 7 patients with methylated CHFR tumor showed some regression or no progression, whereas 4 (80%) of 5 patients with unmethylated CHFR tumor manifested progressive deterioration. CONCLUSIONS: These observations indicated that CHFR methylation may be a clinically useful approach to predict the responsiveness of gastric cancers to treatment with MI.

Adult↗
PubMed2002

Markovian chemicals "in silico" design (MARCH-INSIDE), a promising approach for computer aided molecular design II: experimental and theoretical assessment of a novel method for virtual screening of fasciolicides.

A novel method for in silico selection of fluckicidal drugs is introduced. Two QSARs that permit us to discriminate between fasciolicide and non-fasciolicide drugs (the first) and to outline some conclusions about the possible mechanism of action of a chemical (the second) are performed. The first model correctly classified 93.85% of compounds in the training series and 89.5% of the compounds in the predicting one. This model correctly classified 87.7, 93.8, 92.2 and 93.9% of compounds in leave- n-out cross validation procedures when n takes values from 2 to until 6. The model seems to be stable in around 92% of good classification in leave- n-out cross validation analysis when n>6. The second model correctly classified 70% of non-fasciolicide compounds, 85.71% of beta-tubulin inhibitors and 100% of proton ionophores in the training set. This model recognizes as proton ionophores 100% of any nitrosalicylanilides in the predicting series. Both models have a low p-level <0.05. Finally, the experimental assay of six organic chemicals by an in vivo test permit us to carry out an assessment of the model with a fairly good 100% agreement between experiment and theoretical prediction.

Animals↗
PubMed2004

CoMFA, HQSAR and molecular docking studies of butitaxel analogues with beta-tubulin.

Results from biochemical analyses for a series of 20 butitaxel analogues, paclitaxel and docetaxel were used to build two- and three-dimensional quantitative structure-activity relationship (QSAR) models in order to investigate the properties associated with microtubule assembly and stabilization. A comparative molecular field analysis (CoMFA) model was built using steric and electrostatic fields. The CoMFA model yielded an r2 of 0.943 and a cross-validated r2 (i.e. q2) of 0.376. Hologram quantitative structure-activity relationship (HQSAR) modeling of these same data generated an r2 of 0.919 and a q2 of 0.471. Contour maps used to visualize the steric and electrostatic contributions associated with activity or lack thereof were, as expected, localized to the varied position of the taxane system. Each analogue was docked successfully into a model of beta-tubulin derived from previously determined cryoelectron microscopy analyses of the tubulin alpha/beta heterodimer. All analogues superimposed well with paclitaxel bound to the protein, as well as with each other. Defining the variable region of each structure as the ligand and docking it separately into the paclitaxel site revealed a modest correlation (r2 = 0.53) between activity and docking energy of all the compounds in the dataset. When only the butitaxel derivatives were considered, the correlation increased to 0.61. The mathematical models derived here provide information for the future development of taxanes.

Animals↗
PubMed2006

p38 Mitogen-activated protein kinases is required for counteraction of 2-methoxyestradiol to estradiol-stimulated cell proliferation and induction of apoptosis in ovarian carcinoma cells via phosphorylation Bcl-2.

INTRODUCTION: 2-Methoxyestradiol (2ME2), a natural endogenous product of estradiol (E2) metabolism, has been shown to be a selective apoptotic agent for cancer cells but not for normal cells. In this study, we determined that 2ME2 counteracts E2-stimulated cell growth and induces apoptosis in ovarian carcinoma cells. In addition, we demonstrate that 2ME2 induces apoptosis via p38 and phospho-Bcl2 pathway. METHODS: 2ME2 and/or E2 were administered to the OVCAR-3 (human ovarian cancer) cell line. Cell growth inhibition was analyzed by [3H] Thymidine incorporation assay and DNA fluorometric assay. Cell apoptosis was tested by DNA fragmentation analysis and FACS. The signaling pathway was determined by a series of biochemical assays. RESULTS: 2ME2 inhibited estradiol-stimulated cell growth and induced apoptosis in an ovarian carcinoma cell line. MAPK and p38, but not JNK, were found to be critical mediators in this process. Expression of a dominant negative mutant of p38 kinase or p38 specific inhibitor, SB 203580, almost completely blocked the process. Furthermore, Bcl-2 phosphorylation was required for 2ME2-induced effects. CONCLUSION: Our data suggest that 2ME2 inhibits E2-stimulated proliferation and induces apoptosis in ovarian carcinoma cells. Furthermore, activation of p38 and phosphorylation of Bcl-2 plays a critical role in the mechanism. 2ME2 therefore, may have a clinical application for the treatment of ovarian cancer.

2-Methoxyestradiol↗
PubMed2006

Inducer-and cell type-specific regulation of antiapoptotic MCL1 in myeloid leukemia and multiple myeloma cells exposed to differentiation-inducing or microtubule-disrupting agents.

The antiapoptotic BCL2 family member MCL1 is rapidly upregulated upon exposure of ML-1 myeloid leukemia cells to either differentiation-inducing phorbol 12'-myristate 13'-acetate (PMA) or chemotherapeutic microtubule disrupting agents (MTDAs). This report examined how signaling for MCL1 upregulation is coupled to these two different phenotypic changes, and tested for upregulation in other hematopoietic cancers. With PMA, ERK stimulated MCL1 mRNA expression and ML-1 cell differentiation, and ERK additionally stabilized expression of the MCL1 protein. However, with MTDAs, transient ERK and ensuing JNK activation contributed to initial MCL1 upregulation and viability-retention, but sustained JNK activation eventually resulted in cell death. MCL1 was upregulated by PMA in THP-1 and U937 myeloid leukemia cells, but by MTDAs only in THP-1 cells. MCL1 expression was constitutively elevated in multiple myeloma cell lines, and was not affected by PMA/ERK or MTDAs. Thus, MCL1 expression level and sensitivity to regulation are important considerations in selecting approaches for targeting this antiapoptotic gene product to kill cancer cells.

Apoptosis↗
PubMed2006

A Phase II trial of epothilone B analogue BMS-247550 (NSC #710428) ixabepilone, in patients with advanced pancreas cancer: a Southwest Oncology Group study.

PURPOSE: The purpose of this Phase II multi-institutional study was to define the efficacy and toxicity of ixabepilone in patients with advance pancreatic adenocarcinoma. PATIENTS AND METHODS: Patients were required to have pancreatic adenocarcinoma and metastatic or recurrent disease that was not amenable to curative resection. Performance status was 0-1, and patients could not have had prior chemotherapy, or chemoradiation therapy for their advanced disease although prior local palliative radiation was allowed. Ixabepilone was administered iv as a 3 hour infusion every 21 days. Initially, the dose was 50 mg/m(2) but this was lowered to 40 mg/m(2) shortly after the trial opened because of concerns about neurotoxicity. RESULTS: Sixty-two patients were registered however 2 were ineligible because they did not have recurrent or metastatic disease. For the 60 eligible patients, 22 had performance status of 0 and 38 performance status of 1. The estimated 6-month survival was 60% (95% CI 48%-72%) with a median survival of 7.2 months and an estimated time to treatment failure of 2.3 months. Out of 56 patients with measurable disease there were 5 confirmed partial responses for a confirmed response probability of 9% (95% CI 3%-20%) and 7 unconfirmed partial responses for an overall response probability of 21% (95% CI 12%-34%). Common toxicities were neutropenia/granulocytopenia, nausea and vomiting and neuropathy. There was one death, cause not determined but judged "possibly" related to treatment. CONCLUSION: Ixabepilone shows encouraging activity in patients with advanced pancreatic cancer and should be investigated further in this disease.

Adenocarcinoma↗
PubMed2006

Phase II trial of ixabepilone, an epothilone B analog, given daily for three days every three weeks, in metastatic breast cancer.

Twelve patients with metastatic breast cancer previously exposed to taxanes were treated on a Phase II trial with ixabepilone. Eligible patients had histologically confirmed metastatic breast cancer with measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST), and adequate hematopoietic, renal, and hepatic function. Ixabepilone 8 mg/m(2)/day was given intravenously daily for 3 days for the first 3-week cycle and increased to 10 mg/m(2)/day for subsequent cycles if patients did not have hematologic or other toxicity after the first cycle. Patients continued treatment until progressive disease or unacceptable toxicity. Three, 29, and 33 of 65 cycles administered were at the 7 mg/m(2), 8 mg/m(2) and 10 mg/m(2) dose levels respectively. Grade 4 leukopenia (n=1), grade 3 neutropenia (n=2), grade 2 neuropathy (n=3), and grade 2 transaminase elevation (n=2) were the most notable toxicities. Ten patients had stable disease for at least 6 weeks. No complete or partial responses were observed in 12 evaluable patients treated with ixabepilone daily for 3 days. Although ixabepilone was well-tolerated, the dose of 8-10 mg/m(2) daily for 3 days is not an effective therapy in metastatic breast cancer previously exposed to taxanes.

Adult↗
PubMed2006

Phase I safety, pharmacokinetic and pharmacodynamic studies of 2-methoxyestradiol alone or in combination with docetaxel in patients with locally recurrent or metastatic breast cancer.

PURPOSE: We report the first phase I trials of 2-methoxyestradiol (2ME2, Panzem Capsules, EntreMed, Rockville, MD), alone and in combination with docetaxel, in patients with metastatic breast cancer (MBC). PATIENTS AND METHODS: In Trial 001, 2ME2 monotherapy was administered orally once (200-1000 mg/d, cohorts 1-5) or twice daily (200-800 mg/q12h, cohorts 6-9) for 28 days followed by a 14-day observation period, continuously thereafter. In Trial 002, docetaxel 35 mg/m(2) was administered weekly for four of six weeks for a maximum six cycles; 2ME2 (200-1000 mg/d) was given orally once daily for 28 days followed by a 13-day observation period in cycle one, continuously thereafter. In both trials, responding or stable patients continued 2ME2 until progression. RESULTS: Trial 001 enrolled 31 patients; there were no objective responses. Trial 002 enrolled 15 patients; ORR was 20% including one CR. There were no Grade IV toxicities; MTD was not reached in either study. When combined with docetaxel, three patients had significant transaminase elevations that returned to normal with continued treatment (in two of three patients). There was significant inter-patient variability and extensive metabolism to 2-methoxyestrone (2ME1). Steady-state AUC and trough concentrations of 2ME2 increased linearly up to 400-600 mg/d; doses above 400-600 mg/d did not increase 2ME2 levels. The target trough concentration (3-25 ng/mL) was not attained. Combined administration did not alter docetaxel or 2ME2 pharmacokinetics. CONCLUSION: 2ME2, alone or in combination with docetaxel, was well tolerated in patients with MBC but systemic exposure remained below the expected therapeutic range.

2-Methoxyestradiol↗
PubMed2006

Phase I dose-finding and pharmacokinetic trial of orally administered indibulin (D-24851) to patients with solid tumors.

Indibulin is a synthetic small molecule which antitumor activity is based upon destabilization of microtubules. The primary study objectives were to determine the impact of fasted and fed condition on pharmacokinetic parameters, as well as the maximum tolerated dose of the oral drinking solution of indibulin administered once daily for 14 days every 3 weeks in patients with solid tumors. In the pilot food effect part, patients received a single dose of 20 mg indibulin on day-8 and -4, fasted or fed, in a randomized crossover design. In the dose-escalation part, patients received a single dose of indibulin on day-4. Three dose levels were evaluated: 20, 40 and 80 mg. After a washout period, patients received indibulin once daily for 14 days every 3 weeks (multiple dose part). Blood samples were collected in the pilot food effect- and in the dose escalation study. A total of 14 patients entered, of which 6 completed the food effect study. The ratio of indibulin (fed/fasted) in the food effect study for AUC(0-72) was estimated as 1.24 (P=0.082, 95%CI 0.96-1.41) and C(max) ratio was 0.89 (P=0.54, 95%CI 0.55-1.44). Interpatient variability was high. Higher peak plasma concentrations were reached under fasting conditions which was undesired regarding tolerability. Therefore the dose escalation study was continued under fed conditions. Dose limiting toxicities, nausea and vomiting, appeared to be related to the increased volume of the solvent lactic acid. This study is continued, evaluating indibulin administered as capsules on the recommended dose level of 60 mg daily for 14 days.

Acetamides↗
PubMed2005

Oxidation and methylation status determine the effects of arsenic on the mitotic apparatus.

We investigated the spindle inhibitory properties of six arsenicals differing in their methylation or oxidation state. Human lymphoblasts were exposed for 6 h to either sodium arsenate (NaAs(V)), sodium arsenite (NaAs(III)), monomethylarsonic acid (MMA(V)), monomethylarsonous acid (MMA(III)), dimethylarsinic acid (DMA(V)), or dimethylarsinous acid (DMA(III)). After exposure slides were prepared, and the mitotic indices (MI) were assessed. We also exposed tubulin directly to each arsenical and spectrophotometrically measured its effect on polymerization. NaAs(V) caused a small but significant increase in MI. MMA(V) also caused only a slight increase in MI that just reached statistical significance. In contrast, DMA(V) caused a significant increase in MI, producing approximately 75% the MI of demecolcine and approximately 4 times the MI of the control. NaAs(III) had no significant effect on MI and was quite toxic. MMA(III) induced more than a twofold increase in MI compared to the control, which was about 40% that caused by demecolcine. On a micromolar basis, MMA(III) was the most potent of the arsenicals tested. DMA(III) gave inconsistent results. None of the pentavalent arsenicals had a substantial effect (either inhibition or enhancement) on GTP-induced polymerization of tubulin. In contrast, NaAs(III) inhibited polymerization at concentrations of 1 mM and above and MMA(III) and DMA(III) at 10 microM and above. Taken together, these results present a complex picture of how arsenicals may affect cells. These studies demonstrate that the metabolites of arsenic are active not only as chromosome breaking and DNA damaging agents but can also interfere with cell division via tubulin disruption.

Aneuploidy↗
PubMed2004

Vascular targeting agents.

The role of the vascular network of a tumor has been the focus of much recent research. Angiogenesis, or the growth of new tumor blood vessels, was initially the main target in the development of novel antitumor agents. More recently, new therapeutic strategies have been designed to destroy established tumor blood vessels. These vascular targeting agents (VTAs) exert their action by producing a rapid shutdown of tumor blood flow, resulting in ischemia and tumor cell necrosis. VTAs can be broadly divided into biologic agents and small molecules. In contrast to the biologic agents, drug-based vascular targeting molecules have developed much further, with many clinical trials ongoing. Evidence suggests that VTAs may be useful as single agents but can be more effective when used in combination with other therapeutic regimens.

Angiogenesis Inhibitors↗
PubMed1992

Ethacrynic acid inhibition of microtubule assembly in vitro.

Ethacrynic acid (ECA) is a sulfhydryl reactive diuretic drug. Recent studies show that ocular administration of ECA may have potential efficacy for treatment of glaucoma. ECA affects cell shape in cultured cells from the eye outflow pathway and the microtubule system is disrupted. We have studied the effect of ECA on microtubule protein (MTP) (tubulin and microtubule-associated proteins) and purified tubulin assembly. Fifty percent inhibition of MTP (1.8 mg/ml) assembly was found at 70 microM ECA in buffer and 410 microM ECA in 30% glycerol in buffer. If all sulfhydryl groups were attributed to tubulin, then approximately two sulfhydryls were blocked at 50% inhibition. Tubulin (2 mg/ml) assembly showed 50% inhibition at 175 microM ECA and approximately 2 sulfhydryl groups were lost. Increasing ECA preincubation times (0-60 min) with tubulin showed that the longer the preincubation time, the longer the lag time, and the slower the rate of assembly and that the percentage of inhibition was proportional to the ECA preincubation time. The number of blocked sulfhydryls also increased with preincubation time. Approximately two sulfhydryls were blocked at 50% inhibition of assembly. The critical concentration for assembly increased twofold when tubulin was preincubated with 0.1 mM ECA, suggesting a loss of active tubulin. Fifty percent inhibition of taxol-induced MTP and tubulin assembly occurred at 190 and 280 microM ECA, respectively, with 3.6 to 3.8 sulfhydryls blocked, respectively. Taxol protects microtubules from disassembly by ECA, suggesting that the ECA binding key sulfhydryls are blocked in the microtubule. These results suggest that ECA reacts slowly with tubulin and blocks sulfhydryl groups important for assembly. Microtubule-associated proteins and glycerol protect the sulfhydryls and so more ECA is necessary to inhibit assembly. Since the number of blocked sulfhydryls is greater at 50% inhibition for taxol-induced microtubules, sulfhydryl blocked tubulin incompetent to assemble under normal conditions may be induced to do so with taxol.

Alkaloids↗
PubMed1985

Structure-activity relationships of benzimidazole carbamates as inhibitors of mammalian tubulin, in vitro.

The structure-activity relationships of thirty-two methyl (5(6)-substituted benzimidazol-2yl) carbamates as inhibitors of the rate of polymerisation of mammalian tubulin have been investigated. The size or some colinear physico-chemical characteristic of the substituent in the 5 (or 6)-position has a profound effect on potency. The presence of branching with or without a commensurate increase in the polarity of the 5(6)-substituent adjacent to the benzimidazole ring (alpha-position) resulted in a loss of activity. The nature of the overall site, as reflected by the quantitative models, could relate to either the hydrophobicity or molar volume of the 5 (or 6)-substituents.

Animals↗
PubMed1987

Interaction of phomopsin A and related compounds with purified sheep brain tubulin.

Phomopsins comprise a family of peptide mycotoxins containing a 13-membered ring formed by an ether bridge, produced by the fungus Phomopsis leptostromiformis, the causal agent in lupin poisoning (lupinosis). The biochemical actions of two naturally occurring phomopsins, phomopsin A and B, and the chemical derivatives, phomopsinamine A and octahydrophomopsin A, on purified sheep brain tubulin were investigated. All analogues were potent microtubule inhibitors, blocking the polymerization of tubulin at concentrations of less than 1 microM. They inhibited [3H]vinblastine binding to tubulin and, in common with vinblastine and its competitive inhibitor maytansine, enhanced the binding of [3H]colchicine to tubulin. It is postulated that phomopsin A and its analogues exert their action on tubulin by interaction at or near the vinblastine binding site. Two possible mechanisms for the interaction between vinblastine or phomopsins and colchicine binding to tubulin are proposed.

Animals↗
PubMed1992

Interaction of phomopsin A with porcine brain tubulin. Inhibition of tubulin polymerization and binding at a rhizoxin binding site.

Phomopsin A is an antimitotic cyclic peptide containing a 13-member ring including an ether linkage. It was isolated from the fungus Phomopsis leptostromiformis as the causal agent of lupinosis. Phomopsin A strongly inhibited microtubule assembly (IC50: 2.4 microM). Our study using radiolabeled phomopsin A, prepared biosynthetically by feeding L-[U-14C]isoleucine to the culture of P. leptostromiformis, indicated that at least two binding sites of phomopsin A exist on tubulin on the basis of a Scatchard analysis; i.e. the dissociation constants of a high affinity site (Kd1) and a low affinity site (Kd2) at 37 degrees were determined to be 1 x 10(-8) and 3 x 10(-7) M, respectively. Phomopsin A inhibited the binding of radiolabeled rhizoxin to tubulin with an inhibition constant (Ki) of 0.8 x 10(-8) M. This showed that the high affinity site of phomopsin A is identical to the rhizoxin binding site. The binding of the radiolabeled phomopsin A was also inhibited by rhizoxin and ansamitocin P-3, with an inhibition constant of 10(-7) M, and to a lesser extent by vinblastine. Phomopsin A had no inhibitory effect on colchicine binding to tubulin.

Animals↗
PubMed1993

Dual inhibition of topoisomerase II and tubulin polymerization by azatoxin, a novel cytotoxic agent.

Azatoxin (NSC 640737) is a synthetic molecule that was rationally designed as a topoisomerase II inhibitor (Leteurtre et al., Cancer Res 52: 4478-4483, 1992). The present study was undertaken in order to investigate the molecular pharmacology and the cytotoxic activity of azatoxin in human tumor cells. Alkaline elution experiments performed in HL-60 cells demonstrated that: (1) azatoxin induces DNA-protein cross-links and protein-linked DNA single- and double-strand breaks characteristics of topoisomerase II inhibition in HL-60 cells; and (2) the potency of azatoxin is comparable to that of etoposide (VP-16). Testing of azatoxin in 45 human cell lines in the National Cancer Institute (NCI) in vitro Drug Screening Program indicated that azatoxin was potent (mean IC50 = 0.13 microM), but that its cell line sensitivity profile was correlated with that of tubule inhibitors rather than that of topoisomerase II inhibitors. These data led us to investigate the anti-tubulin activity of azatoxin. We found that azatoxin inhibited tubulin polymerization in vitro and was a mitotic inhibitor at 1 microM and above in the human colon cancer cell line KM20L2. In these cells topoisomerase II inhibition, as detected by the induction of protein-linked DNA strand breaks, required azatoxin concentrations of at least 10 microM. In summary, azatoxin is a potent cytotoxic agent that inhibited both tubulin and topoisomerase II. At lower azatoxin concentrations the former activity prevailed whereas at higher concentrations topoisomerase II inhibition became prominent.

Cell Death↗