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Aluminum Partitioning in Intact Roots of Aluminum-Tolerant and Aluminum-Sensitive Wheat (Triticum aestivum L.) Cultivars.

Aluminum (Al) partitioning in intact roots of wheat (Triticum aestivum L.) cultivars that differ in sensitivity to Al was investigated. Roots of intact seedlings were exposed to Al for up to 24 hours and distribution of Al was assessed visually by hematoxylin staining or by direct measurement of concentration of Al by atomic absorption spectrophotometry or ion chromatography. Major differences in Al accumulation between Al-tolerant (Atlas 66) and Al-sensitive (Tam 105) cultivars were found in the growing regions 0 to 2 and 2 to 5 millimeters from the root apex. Al content was 9 to 13 times greater in the 0 to 2 millimeters root tips of cv Tam 105 than in the tips of cv Atlas 66 when exposed to 50 micromolar Al for 19 to 24 hours. The oxidative phosphorylation inhibitor carbonyl cyanide m-chlorophenylhydrazone and the protein synthesis inhibitor cycloheximide increased Al uptake by intact root tips of cv Atlas 66. Also, loss of Al from the roots of both cultivars was measured after the roots were "pulsed" with 50 micromolar Al for 2 hours and then placed in an Al-free nutrient solution for 6 hours. The 0 to 2 millimeter root tips of cv Tam 105 lost 30% of the absorbed Al, whereas the tips of cv Atlas 66 lost 60%. In light of these results, we conclude that the differential Al sensitivity in wheat correlates with the concentration of Al in the root meristems. The data support the hypothesis that part of the mechanism for Al tolerance in wheat is based on a metabolism-dependent exclusion of Al from the sensitive meristems.

Journal Article↗

2.9 A crystal structure of ligand-free tryptophanyl-tRNA synthetase: domain movements fragment the adenine nucleotide binding site.

The crystal structure of ligand-free tryptophanyl-tRNA synthetase (TrpRS) was solved at 2.9 A using a combination of molecular replacement and maximum-entropy map/phase improvement. The dimeric structure (R = 23.7, Rfree = 26.2) is asymmetric, unlike that of the TrpRS tryptophanyl-5'AMP complex (TAM; Doublié S, Bricogne G, Gilmore CJ, Carter CW Jr, 1995, Structure 3:17-31). In agreement with small-angle solution X-ray scattering experiments, unliganded TrpRS has a conformation in which both monomers open, leaving only the tryptophan-binding regions of their active sites intact. The amino terminal alphaA-helix, TIGN, and KMSKS signature sequences, and the distal helical domain rotate as a single rigid body away from the dinucleotide-binding fold domain, opening the AMP binding site, seen in the TAM complex, into two halves. Comparison of side-chain packing in ligand-free TrpRS and the TAM complex, using identification of nonpolar nuclei (Ilyin VA, 1994, Protein Eng 7:1189-1195), shows that significant repacking occurs between three relatively stable core regions, one of which acts as a bearing between the other two. These domain rearrangements provide a new structural paradigm that is consistent in detail with the "induced-fit" mechanism proposed for TyrRS by Fersht et al. (Fersht AR, Knill-Jones JW, Beduelle H, Winter G, 1988, Biochemistry 27:1581-1587). Coupling of ATP binding determinants associated with the two catalytic signature sequences to the helical domain containing the presumptive anticodon-binding site provides a mechanism to coordinate active-site chemistry with relocation of the major tRNA binding determinants.

Adenine Nucleotides↗

Role of the oestrogen receptor in liver regeneration in the male rat.

Partial hepatectomy in male rats results in raised serum oestrogen levels, nuclear binding of oestrogen receptor (ER) and feminization of certain aspects of hepatic metabolism. It has been proposed that these changes may have an important role in liver regeneration. The present study was performed to ascertain the effects of the oestrogen agonist diethylstilbestrol (DES), 2 mg/kg, and the oestrogen antagonist tamoxifen (TAM), 2 mg/kg, on liver regeneration induced by partial hepatectomy in the male rat. Regenerative activity was determined by incorporation of [3H]-thymidine into hepatic DNA as well as by measurement of liver remnant weight. Following partial hepatectomy, there was a trend towards an increase in liver remnant weight at 24 h in rats treated with DES (DES, 5.95 +/- 1.52 g; vehicle, 4.87 +/- 0.66 g; P = 0.06) though by 48 h no effect was found. Tamoxifen treatment did not significantly affect liver weight at 24 h but by 48 h there was a highly significant reduction in liver remnant weight (TAM, 5.41 +/- 0.85 g; vehicle, 7.31 +/- 1.43 g; P < 0.001). Neither DES nor TAM treatment influenced liver regeneration as determined by [3H]-thymidine incorporation into hepatic DNA. We conclude that pharmacologic manipulation of oestrogens does not influence the initiation of the regenerative process but that oestrogen may facilitate later phases of hepatic growth.

Animals↗

HIV-1 reverse transcriptase (RT) genotypic patterns and treatment characteristics associated with the K65R RT mutation.

BACKGROUND: The K65R HIV-1 reverse transcriptase (RT) mutation is a multidrug resistance mutation which may be correlated with specific antiretroviral combinations and with the presence or absence of other RT resistance mutations. OBJECTIVES: The aims of this study were: (i) to determine the prevalence of the K65R mutation in a cohort of antiretroviral-treated patients; (ii) to study genotypic patterns and treatment characteristics in patients in whom the K65R mutation was present. STUDY DESIGN: We included in the study all antiretroviral-experienced patients followed up at the Bordeaux University Hospital in 2003 and 2004 for whom an HIV-1 genotypic resistance analysis was available. Information on RT resistance mutations was reported from a hospital database including therapeutic and biological parameters. The prevalence of K65R was investigated for all patients. Genotypic patterns and treatment characteristics were examined at the time of detection of the K65R mutation. RESULTS: The prevalence of K65R was 1.9% (26 of 1404 patients). K65R was associated with nucleoside RT inhibitor-based regimens in 22 patients, and with tenofovir disoproxil fumarate, lamivudine, didanosine and abacavir in 23, 17, 17 and eight patients, respectively. The M184V and Q151M mutations were the most commonly co-selected substitutions. Thymidine analogue mutations (TAMs) were rarely co-selected with K65R and inversely associated with K65R. CONCLUSION: The K65R mutation may emerge preferentially in the absence of zidovudine and TAMs, suggesting the possibility of an antagonistic interaction between K65 and TAMs.

Anti-HIV Agents↗

Effects of thrombopoietin (c-mpl ligand) on growth of blast cells from patients with transient abnormal myelopoiesis and acute myeloblastic leukemia.

Thrombopoietin (TPO) is a ligand for c-mpl that promotes both proliferation and differentiation of megakaryocytes in vivo and in vitro. We investigated the expression of c-mpl transcripts and the effects of recombinant human TPO (rhTPO) on the proliferation and differentiation of human leukemic cell lines or fresh samples obtained from 32 patients with transient abnormal myelopoiesis (TAM) or acute myeloblastic leukemia (AML). Cells were cultured with TPO alone or combined with rh interleukin-3 (IL-3) or stem cell factor (SCF). Expression of c-mpl was verified in 6 of 13 cases tested. All but one of the cases that showed c-mpl expression responded to TPO. Blasts from all cases of TAM or French-American-British (FAB) subtype M7 showed growth responses to TPO with higher sensitivity than cells of other FAB subtypes and these responses were increased by addition of rhIL-3 or rhSCF in some cases. Responses of cells of other FAB subtypes varied. In addition, increased expression of platelet-specific surface antigens on MO7E cells after incubation with rhTPO was observed. These data suggest that TPO may be involved in the abnormal proliferation and differentiation of human leukemic cells, especially of M7 and TAM cells, considered to be of megakaryocytic lineage.

Adult↗

Biotransformation of melatonin in human breast cancer cell lines: role of sulfotransferase 1A1.

The biologically active melatonin metabolite, 6-hydroxymelatonin (6-OHMel), is conjugated to form 6-hydroxymelatonin sulfate (6-OHMelS). To elucidate the role of the sulfotransferase (SULT) enzyme 1A1, considerably expressed in normal and malignant human breast cells, we measured the formation of 6-OHMelS by ELISA in hormone-dependent MCF-7 and hormone-independent MDA-MB231 (MDA) breast cancer cell lines after stable transfection with SULT1A1. In parent MDA cells, low SULT1A1 mRNA expression was associated with moderate 6-OHMelS formation as determined after application (24 hr) of 0.1 microM 6-OHMel. As expected, overexpression of SULT1A1 in MDA cells resulted in a 2.9- and 110-fold increase in 6-OHMelS in the cytosol and cellular supernatant respectively. Furthermore, 6.3- and 115-fold increases were observed after 0.5 microM, and 12.6- and 101-fold increases after 1 microM 6-OHMel respectively. In MCF-7 cells, because of high basal SULT1A1 expression, only two- to threefold increases in 6-OHMelS were observed after transfection with the enzyme. In total, 866 and 539 pmol/mg protein 6-OHMelS were formed from 1 microM 6-OHMel in SULT1A1 overexpressing MDA and MCF-7 cells, respectively, whereas application of 1 microM melatonin produced only <1% of 6-OHMelS. Possible interactions with the SULT1A1 substrate tamoxifen (tam), an anti-estrogen applied in the therapy of breast cancer, were also studied. A concentration of 1 microM tam increased 6-OHMelS formation by approximately threefold in the presence of 1 microM melatonin or 1 microM 6-OHMel respectively. However, no alterations were detected after application of 1 microM 4-hydroxy-tamoxifen. In summary, we demonstrate the importance of SULT1A1 for the biotransformation of 6-OHMel in human breast cancer cells. Our data further suggest that tam can modulate melatonin biotransformation.

Antineoplastic Agents, Hormonal↗

Directed evolution of pyruvate decarboxylase-negative Saccharomyces cerevisiae, yielding a C2-independent, glucose-tolerant, and pyruvate-hyperproducing yeast.

The absence of alcoholic fermentation makes pyruvate decarboxylase-negative (Pdc(-)) strains of Saccharomyces cerevisiae an interesting platform for further metabolic engineering of central metabolism. However, Pdc(-) S. cerevisiae strains have two growth defects: (i) growth on synthetic medium in glucose-limited chemostat cultures requires the addition of small amounts of ethanol or acetate and (ii) even in the presence of a C(2) compound, these strains cannot grow in batch cultures on synthetic medium with glucose. We used two subsequent phenotypic selection strategies to obtain a Pdc(-) strain without these growth defects. An acetate-independent Pdc(-) mutant was obtained via (otherwise) glucose-limited chemostat cultivation by progressively lowering the acetate content in the feed. Transcriptome analysis did not reveal the mechanisms behind the C(2) independence. Further selection for glucose tolerance in shake flasks resulted in a Pdc(-) S. cerevisiae mutant (TAM) that could grow in batch cultures ( micro (max) = 0.20 h(-1)) on synthetic medium, with glucose as the sole carbon source. Although the exact molecular mechanisms underlying the glucose-tolerant phenotype were not resolved, transcriptome analysis of the TAM strain revealed increased transcript levels of many glucose-repressible genes relative to the isogenic wild type in nitrogen-limited chemostat cultures with excess glucose. In pH-controlled aerobic batch cultures, the TAM strain produced large amounts of pyruvate. By repeated glucose feeding, a pyruvate concentration of 135 g liter(-1) was obtained, with a specific pyruvate production rate of 6 to 7 mmol g of biomass(-1) h(-1) during the exponential-growth phase and an overall yield of 0.54 g of pyruvate g of glucose(-1).

Culture Media↗

Identification of a distinctive mutation spectrum associated with high levels of transcription in yeast.

High levels of transcription are associated with increased mutation rates in Saccharomyces cerevisiae, a phenomenon termed transcription-associated mutation (TAM). To obtain insight into the mechanism of TAM, we obtained LYS2 forward mutation spectra under low- versus high-transcription conditions in which LYS2 was expressed from either the low-level pLYS2 promoter or the strong pGAL1-10 promoter, respectively. Because of the large size of the LYS2 locus, forward mutations first were mapped to specific LYS2 subregions, and then those mutations that occurred within a defined 736-bp target region were sequenced. In the low-transcription strain base substitutions comprised the majority (64%) of mutations, whereas short insertion-deletion mutations predominated (56%) in the high-transcription strain. Most notably, deletions of 2 nucleotides (nt) comprised 21% of the mutations in the high-transcription strain, and these events occurred predominantly at 5'-(G/C)AAA-3' sites. No -2 events were present in the low-transcription spectrum, thus identifying 2-nt deletions as a unique mutational signature for TAM.

Base Sequence↗

Dominant-negative TAK1 induces c-Myc and G(0) exit in liver.

Transforming growth factor-beta (TGF-beta)-activated kinase 1 (TAK1), a serine/threonine kinase, is reported to function in the signaling pathways of TGF-beta, interleukin 1, and ceramide. However, the physiological role of TAK1 in vivo is largely unknown. To assess the function of TAK1 in vivo, dominant-negative TAK1 (dnTAK1) was expressed in the rat liver by adenoviral gene transfer. dnTAK1 expression abrogated c-Jun NH(2)-terminal kinase and c-Jun but not nuclear factor (NF)-kappaB or SMAD activation after partial hepatectomy (PH). Expression of dnTAK1 or TAM-67, a dominant-negative c-Jun, induced G(0) exit in quiescent liver and accelerated cell cycle progression after PH. Finally, dnTAK1 and TAM-67 induced c-myc expression in the liver before and after PH, suggesting that G(0) exit induced by dnTAK1 and TAM-67 is mediated by c-myc induction.

Animals↗

Anti-inflammatory properties of the novel antitumor agent yondelis (trabectedin): inhibition of macrophage differentiation and cytokine production.

Yondelis (Trabectedin) is a novel antitumor agent of marine origin extracted from the tunicate Ecteinascidia turbinata. This original compound is active against several human tumors including sarcoma and ovarian and breast adenocarcinoma, as evidenced in phase II clinical trials in advanced multitreated patients. Yondelis is a DNA minor groove binder that blocks cell cycle and interferes with inducible gene transcription in a selective manner. In this study, we investigated the immunomodulatory properties of Yondelis on leukocytes. Human blood monocytes were highly susceptible in vitro to its cytotoxic effect and underwent apoptosis at pharmacologically relevant concentrations (5 nmol/L), whereas lymphocytes were up to 5-fold less sensitive. Macrophages differentiated in vitro with macrophage colony-stimulating factor and tumor-associated macrophages (TAM), isolated from patients with ovarian cancer, were also susceptible. At subcytotoxic concentrations, Yondelis inhibited the in vitro differentiation of monocytes to macrophages. In tumor-treated patients, drug infusion caused a selective decrease of monocyte counts and of ex vivo macrophage differentiation. The in vitro production of two proinflammatory mediators, CCL2 and IL-6, was markedly reduced by Yondelis in monocytes, macrophages, TAM, and freshly isolated ovarian tumor cells. The chemokine CCL2 is the major determinant of monocyte recruitment at tumor sites, whereas IL-6 is a growth factor for ovarian tumors. In view of the protumor activity of TAM and of the strong association between chronic inflammation and cancer progression, the inhibitory effect of Yondelis on macrophage viability, differentiation, and cytokine production is likely to contribute to the antitumor activity of this agent in inflammation-associated human tumors.

Antineoplastic Agents, Alkylating↗

Targeting myelomonocytic cells to revert inflammation-dependent cancer promotion.

Tumor development and progression are strongly linked to inflammation and the presence of tumor-associated macrophages (TAMs). In murine tumors, antitumor activity can be achieved by targeting TAM recruitment, survival, activation, polarization, effector signaling, or extracellular matrix interactions. Thus, it may be possible to increase the efficacy of conventional cancer therapeutic strategies by targeting TAMs.

Animals↗

Functional screen for genes responsible for tamoxifen resistance in human breast cancer cells.

Antiestrogens, such as tamoxifen, are widely used for endocrine treatment of estrogen receptor-positive breast cancer. However, as breast cancer progresses, development of tamoxifen resistance is inevitable. The mechanisms underlying this resistance are not well understood. To identify genes involved in tamoxifen resistance, we have developed a rapid screening method. To alter the tamoxifen-sensitive phenotype of human ZR-75-1 breast cancer cells into a tamoxifen-resistant phenotype, the cells were infected with retroviral cDNA libraries derived from human placenta, human brain, and mouse embryo. Subsequently, the cells were selected for proliferation in the presence of 4-hydroxy-tamoxifen (OH-TAM) and integrated cDNAs were identified by sequence similarity searches. From 155 OH-TAM-resistant cell colonies, a total of 25 candidate genes were isolated. Seven of these genes were identified in multiple cell colonies and thus cause antiestrogen resistance. The epidermal growth factor receptor, platelet-derived growth factor receptor-alpha, platelet-derived growth factor receptor-beta, colony-stimulating factor 1 receptor, neuregulin1, and fibroblast growth factor 17 that we have identified have been described as key regulators in the mitogen-activated protein kinase pathway. Therefore, this pathway could be a valuable target in the treatment of patients with breast cancer resistant to endocrine treatment. In addition, the putative gene LOC400500, predicted by in silico analysis, was identified. We showed that ectopic expression of this gene, designated as breast cancer antiestrogen resistance 4 (BCAR4), caused OH-TAM resistance and anchorage-independent cell growth in ZR-75-1 cells and that the intact open reading frame was required for its function. We conclude that retroviral transfer of cDNA libraries into human breast cancer cells is an efficient method for identifying genes involved in tamoxifen resistance.

Animals↗

Mitogen-activated protein kinase cascade in breast cancer.

The mitogen-activated protein (MAP) kinase is considered to play a central role in diverse cellular events including carcinogenesis and tumor progression. Indeed, expression of MAP kinase, tyrosine-phosphorylated MAP kinase, and Raf-1 protein was greater in cancerous human tissues than in the surrounding noncancerous glands. In a 7,12-dimethylbenz[a]anthracene-induced rat mammary carcinoma model, estrogen promoted and ovariectomy and antiestrogen, tamoxifen (TAM) inhibited the tumor growth. Ovariectomy suppressed expression of MAP kinase, tyrosine-phosphorylated MAP kinase and Raf-1, whereas estrogen as well as TAM induced expression of MAP kinase and Raf-1 under castrated conditions. Since it was reported that MAP kinase was activated during the progression of breast carcinoma cells, such estrogenic actions of TAM toward the MAP kinase cascade might be responsible for malignant progression.

Animals↗

Estrogen receptor profiles: changes in mouse and rat mammary tumors by treatment with selective estrogen receptor modifiers.

OBJECTIVE: The aim of this work was to analyze the effect of estradiol (E(2)), medroxyprogesterone and the two selective estrogen receptor modulators (SERMs) (tamoxifen (Tam) and raloxifene (Ral)) on the estrogen receptor (ER) conformers profile performed by size exclusion HPLC in relation to hormone dependence of mammary tumors. MATERIALS AND METHODS: Two types of mammary tumors were studied: tumors transplanted in BALB/c mice that are medroxyprogesterone acetate (MPA)-dependent for growth, and tumors induced in Sprague-Dawley rats by intraperitoneal injection of N-nitroso-N-methylurea (NMU). Tumors from mice treated with MPA, E(2), Tam or Ral and NMU-treated rats were analyzed and compared to that of control. RESULTS: The tumor conformer profiles were as follows: control and MPA-treated mice showed only one peak (oligomeric form); E(2)-treated mice also showed only one peak (dimer); Tam-treated mice showed one peak corresponding to a possible proteolytic fragment, and Ral-treated mice showed two peaks (oligomeric and a possible proteolytic fragment). On the other hand, NMU-induced mammary tumors from rats showed three peaks (oligomeric, monomeric and proteolytic). CONCLUSION: Our findings may indicate that SERMs affect the aggregation state of ER and thereby its ability to modulate genomic transcription mechanisms related to growth rate.

Animals↗

Expression of plasminogen activator as a marker of stimulation in tumor-associated macrophages.

Tumor-associated macrophages (TAM) are a peculiar subpopulation of resident phagocytes with activities possibly important at the tumor host interface. Among these activities the production of proteases could obviously influence tumor cell detachment and migration from the primary. We have evaluated the expression of plasminogen activator (PA) in different types of murine tumors with differing immunogenic capacity. In TAM from all tumors studied the expression of PA was markedly greater than that of resident peritoneal macrophages. The fact that PA was similarly enhanced in peritoneal macrophages responding to a standard stimulation (thioglycolate) and in TAM suggests that the expression of PA is part of a more general cellular inflammatory response to injury.

Animals↗

Influence of hormones on proliferation of ER-positive cells and ER-negative cells of human breast cancer (MCF-7).

The influence of endocrine therapy on the proliferation of estrogen receptor (ER)-positive cells and ER-negative cells of human breast cancer (MFC-7) serially transplanted into nude mice was analyzed by tumor growth, dextran-coated charcoal (DCC) method, ER-immunocytochemical assay (ER-ICA) and ER-immunocytochemically stained 3H-thymidine autoradiography. In the tamoxifen (TAM) group and the medroxyprogesterone acetate (MPA) group, tumor growth was inhibited, but it was promoted in the 17-beta-estradiol dipropionate (E2) group. The ER level by the DCC method was significantly decreased in the TMA, the MPA and the E2 groups. The ER-ICA showed that the percentage of ER-positive cells was decreased in the TAM and the MPA group, but it was increased in E2 group. However, the ER-immunocytochemically stained 3H-thymidine autoradiography showed that not only the labelling index of ER-positive cells but also that of ER-negative cells was significantly decreased in the TAM and the MPA groups, while the labelling index was significantly increased in the E2 groups. Therefore, it was concluded that endocrine therapy affected the proliferation of both ER-positive cells and ER-negative cells of ER-positive breast cancer.

Animals↗

Effects of OK-432 (Picibanil) on estrogen receptor levels and tamoxifen treatment in 7,12-dimethylbenz[a]anthracene-induced rat mammary cancers.

The effects of OK-432 (Picibanil) on estrogen receptor (ER) levels and subsequent tamoxifen (TAM) treatment were examined in 189 female Sprague-Dawley rats with 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary cancers. When OK-432 was administered (0.1 KE/kg i.p. once weekly) for 12 weeks to the rats after DMBA, the average ER level of the TAM-responsive tumors in the OK-432-treated group was significantly higher than that in the control group. The antitumor effect of TAM was significantly greater in the OK-432-treated group. When OK-432 was administered to rats with established DMBA tumors, the average ER levels did not change significantly after 2 or 4 weeks of treatment. ER levels in the control group (no treatment) fell significantly after 2 or 4 weeks. These results suggest that hormone dependence of DMBA-induced rat mammary cancers may be maintained or augmented by the administration of OK-432.

9,10-Dimethyl-1,2-benzanthracene↗

Effects of OK-432 (picibanil) on the estrogen receptors of MCF-7 cells and potentiation of antiproliferative effects of tamoxifen in combination with OK-432.

OK-432 (picibanil), a streptococcal preparation, has a strong biological response modifier (BRM) function and is expected to produce clinical improvement and prolongation of survival in treated cancer patients in Japan. We were interested in whether OK-432 augments estrogen receptor (ER) levels in breast cancer. To investigate the effect of the BRMs on cellular growth and the characteristics of ER and progesterone receptors (PgR) in the human breast cancer cell line MCF-7, we used OK-432, Krestin (PSK), a protein-bound polysaccharide extracted from Coriolus versicolor, and lentinan, a fungal branched (1...3)-beta-D-glycan. OK432 and PSK dose dependently inhibited DNA synthesis of MCF-7 cells, and the 50% inhibitory concentrations of OK-432 and PSK were 1.2 KE (klinische Einheit, clinical unit)/ml and 200 micrograms/ml, respectively. Lentinan showed no direct anticancer effect in vitro. We found that OK-432 induced a 2-fold increase in ER levels in MCF-7 cells at 0.005 KE/ml, but not in PgR. Lentinan and low-dose PSK did not change ER or PgR levels, but high-dose PSK decreased ER and PgR. We also studied the combined effect of OK-432 and antiestrogens, tamoxifen (TAM) and DP-TAT-59. The combined treatment with OK-432 and TAM showed an additive inhibitory effect on MCF-7 cells. These results suggest that OK-432 may augment the therapeutic effect of TAM in breast cancer.

Antineoplastic Agents↗