oxadiazoles and Glioma

Elemene is a second-line broad-spectrum anti-tumour drug that has been used in China for more than two decades. However, its main anti-tumour ingredient, β-elemene, has disadvantages, including excessive lipophilicity and relatively weak anti-tumour efficacy. To improve the anti-tumour activity of β-elemene, based on its minor molecular weight character, we introduced furoxan nitric oxide (NO) donors into the β-elemene structure and designed six series of new generation β-elemene NO donor hybrids. The synthesised compounds could effectively release NO

Topics: Animals; Antineoplastic Agents; Brain Neoplasms; Cell Line, Tumor; Cell Proliferation; Dose-Response Relationship, Drug; Glioma; Humans; Mice; Mice, Nude; Molecular Structure; Neoplasms, Experimental; Nitric Oxide; Oxadiazoles; Sesquiterpenes; Structure-Activity Relationship

Multi-drug resistance (MDR) is a major obstacle to successful cancer treatment. Therefore, in vitro models are necessary for the investigation of the phenotypic changes provoked by cytotoxic agents and more importantly for preclinical testing of new anticancer drugs.. We analyzed chromosomal, numerical, and structural changes after development of MDR, alterations in p53 and PTEN, single nucleotide polymorphisms (SNPs) in the mdr1 gene and corresponding protein expression of P-glycoprotein (P-gp) in three human MDR cancer cell lines: non-small cell lung carcinoma NCI-H460/R, colorectal carcinoma DLD1-TxR, and glioma U87-TxR. In addition, we explored how these molecular and phenotypic alterations influence the anticancer effect of new drugs.. Cytogenetic analysis showed polyploidy reduction after development of MDR in U87-TxR. Losses of 6q in all resistant cancer cell lines and inactivation of p53 in U87-TxR and PTEN in DLD1-TxR were also revealed. Overexpression of P-gp was observed in all MDR cancer cell lines. We evaluated the anticancer activities and MDR reversal potential of Akt inhibitor GSK690693, Ras inhibitor Tipifarnib, and two P-gp inhibitors (jatrophane diterpenoids). Their effects vary due to the cell-type differences, existence of MDR phenotype, presence of mdr1 SNP, and tumor suppressors' alterations. Tipifarnib and jatrophane diterpenoids significantly sensitized MDR cancer cells to paclitaxel.. In conclusion, investigated MDR cancer cells obtained new molecular and cytogenetic characteristics that may serve as potential clinical prognostic markers. In addition, these MDR cancer cell lines present a valuable model for preclinical evaluation of new anticancer agents.

Topics: Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily B, Member 1; Carcinoma, Non-Small-Cell Lung; Cell Line, Tumor; Colorectal Neoplasms; Cytogenetic Analysis; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Glioma; Humans; Lung Neoplasms; Oxadiazoles; Phenotype; Polymorphism, Single Nucleotide; Prognosis; PTEN Phosphohydrolase; Tumor Suppressor Protein p53

The present study reports on G-protein activation by recombinant 5-HT receptors and by native 5-HT1A and 5-HT1B receptors in guinea-pig and rat brain using agonist-stimulated [35S]GTPgammaS binding responses mediated by a new 5-HT ligand, a dimer of sumatriptan. Dimerization of sumatriptan increased the binding affinity for h 5-HT1B (pKi: 9.22 vs. 7.79 for sumatriptan), h 5-HT1D (9.07 vs. 8.08) and also h 5-HT1A receptors (7.80 vs. 6.40), while the binding affinity for h 5-ht1E (6.67 vs. 6.19) and h 5-ht1F (7.37 vs. 7.78) receptors was not affected. Sumatriptan dimer (10 microM) stimulated [35S]GTPgammaS binding mainly in the superficial gray layer of the superior colliculi, hippocampus and substantia nigra of guinea-pig and rat coronal brain sections. This fits with the labelling by the 5-HT1B/1D receptor antagonist [3H] GR 125743. The observed [35S]GTPgammaS binding responses in the substantia nigra are likely to be mediated by stimulation of the 5-HT1B receptor subtype, since they were antagonized by the 5-HT1B inverse agonist SB 224289 (10 microM), and not by the 5-HT2A/1D antagonist ketanserin (10 microM). Quantitative assessment of the [35S]GTPgammaS binding responses in the substantia nigra of rat showed highly efficacious responses for both sumatriptan dimer and its monomer. In contrast, less efficacious agonist responses (51+/-10% and 35+/-13%, respectively) were measured in the guinea-pig substantia nigra. This may suggest that the G-protein coupling efficacy of 5-HT1B receptors is different between the substantia nigra of both species. In addition, the sumatriptan dimer also activated guinea-pig and rat hippocampal 5-HT1A receptors with high efficacy in contrast to sumatriptan. Therefore, dimerization of sumatriptan can be considered as a new approach to transform a partial 5-HT1A agonist into a more efficacious agonist. In conclusion, the sumatriptan dimer stimulates G-protein activation via 5-HT1B receptors besides 5-HT1A receptors in guinea-pig and rat brain. The magnitude of the 5-HT1B receptor responses is superior for sumatriptan and its dimer in rat compared to guinea-pig substantia nigra.

Topics: Animals; Autoradiography; Binding, Competitive; Brain Chemistry; Dimerization; Glioma; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Diphosphate; Guinea Pigs; HeLa Cells; Humans; Male; Membrane Proteins; Oxadiazoles; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT1B; Receptors, Serotonin; Receptors, Serotonin, 5-HT1; Serotonin Receptor Agonists; Sulfur Radioisotopes; Sumatriptan; Tryptamines

The putative coupling between stably expressed recombinant h 5-HT1B or h 5-HT1D receptors and K+ channels which regulate excitability was investigated in C6 glioma cells. Outward K+ currents (IK) were examined in nontransfected C6 glioma cells and in cells expressing cloned h 5-HT1B or h 5-HT1D receptors using the patch-clamp technique in the whole-cell configuration. IK was elicited by a depolarizing step from a holding potential of -60 mV. In C6 glioma cells expressing either recombinant h 5-HT1B or h 5-HT1D receptors, sumatriptan similarly increased IK in a concentration-dependent manner (maximum increase 19.4+/-7.2%, n=8, P<0.05 and 25.1+/-3.9%, n=6, P<0.001, respectively) with EC50 values (geometric mean with 95% confidence intervals in parentheses) of 56.3 nM (7.9-140 nM) and 68.7 nM (16-120 nM), respectively. Sumatriptan failed to elicit increases in IK in non-transfected cells, confirming a specific involvement of the respective membrane h 5-HT1B and h 5-HT1D receptors in transfected C6 cells. In the presence of the mixed 5-HT1B/D receptor antagonist GR 127935 (0.1 microM), sumatriptan (1 microM) failed to significantly increase IK in C6 cells expressing h 5-HT1B receptors (-7.5+/-3.5%, P=NS, n=6), although a higher concentration of GR 127935 (1 microM) was required to significantly inhibit sumatriptan-evoked increases in IK in C6 cells expressing h 5-HT1D receptors (-1.8+/-3.5%, P=NS, n=6), confirming that sumatriptan-evoked responses were indeed mediated by h 5-HT1B and h 5-HT1D receptors, respectively. In C6 cells expressing either cloned h 5-HT1B or h 5-HT1D receptors, sumatriptan-induced increases in IK were prevented by the calcium chelator EGTA (5 mM) when included in the patch pipette (maximum increase 0.57+/-0.6%, n=3, P=NS and -2.8+/-1.6%, n=5, P=NS, respectively). In C6 cells expressing cloned h 5-HT1B receptors, sumatriptan (1 microM) similarly failed to significantly increase IK in the presence of dibutyryl cAMP (10 microM) or when a nominally Ca2+-free medium was included in the patch pipette (-19.4+/-5.1%, n=5 and -5.2+/-4.3%, n=5, respectively, P=NS in each case). In addition, the Ca2+-dependent K+ channel blockers iberiotoxin (0.1 microM) and tetraethylammonium (TEA, 1 mM) abolished sumatriptan-induced increases in IK (-0.5+/-1.0%, n=4 and -3.9+/-3.1%, n=4, respectively, P=NS in each case) in C6 cells expressing h 5-HT1B receptors, confirming the involvement of Ca2+-dependent K+ channels. In C6 cells expressing cloned h 5-HT1B rec

Topics: Animals; Calcium; Cyclic AMP; Dose-Response Relationship, Drug; Glioma; Oxadiazoles; Piperazines; Potassium; Potassium Channels; Rats; Receptors, Serotonin; Recombinant Proteins; Serotonin Antagonists; Sumatriptan; Tumor Cells, Cultured

The long-term modulation of calcium (Ca2+) currents (ICa) was studied in 108CC15 neuroblastoma x glioma hybrid (NxG) cells grown under various culture conditions. The following results were obtained: 1. Addition of 1 mM dibutyryl cyclic adenosine monophosphate (db-cAMP) or 0.1 microM forskolin to the culture medium increased a transient component of ICa two-fold within 3 days, from 21.0 +/- 1.6 pA/pF (n = 22) to a maximum of 40.0 +/- 2.6 pA/pF (n = 28). Under these conditions, cells also expressed a slowly inactivating ICa component (maximum after 3 days, 20.5 +/- 1.6 pA/pF, n = 28). 2. The fast inactivating ICa as well as the db-cAMP-induced slowly inactivating ICa were completely down-regulated during incubation of NxG cells with the inorganic Ca2+ channel blocker, nickel (Ni2+, 100 microM). The suppressing effect was reversed within 3 days of incubation in db-cAMP-containing medium lacking Ni2+. 3. Binding studies on membrane preparations of control and Ni2(+)-pretreated NxG cells revealed a marked difference in the maximal (+)3H-PN200-110 binding. The difference was seen in undifferentiated as well as in db-cAMP-incubated cells. 4. The protein synthesis blocker, cycloheximide, suppressed both the db-cAMP-induced increase and the reappearance of ICa following Ni2+ pretreatment. It is suggested that chronic application of db-cAMP or Ni2+ to NxG cells increases and decreases the number of Ca2+ channel proteins, respectively.

Topics: Animals; Bucladesine; Calcium Channels; Colforsin; Cycloheximide; Glioma; Hybrid Cells; Isradipine; Mice; Neuroblastoma; Nickel; Oxadiazoles; Rats; Tumor Cells, Cultured