| 1. |
- Brest, Patrick, et al.
(författare)
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Histone deacetylase inhibitors promote the tumoricidal effect of HAMLET.
- 2007
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Ingår i: Cancer Research. - 1538-7445. ; 67:23, s. 11327-11334
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Tidskriftsartikel (refereegranskat)abstract
- Histone deacetylase inhibitors (HDIs) and HAMLET (human alpha-lactalbumin made lethal to tumor cells) interact with histones, modify the structure of chromatin, and trigger tumor cell death. This study investigated how the combination of HDIs and HAMLET influences cell viability, histone acetylation, and DNA integrity. The pretreatment of tumor cells with HDIs was shown to enhance the lethal effect of HAMLET and the histone hyperacetylation response to HDIs increased even further after HAMLET treatment. HDIs and HAMLET were shown to target different histone domains as HAMLET bound tailless core histones, whereas HDIs modify the acetylation of the histone tail. DNA damage in response to HAMLET was increased by HDIs. The DNA repair response (p21WAFI expression) was induced by both agonists but abolished when the two agonists were combined. The results suggest that the synergy of HDIs and HAMLET is based on different but converging death pathways, both involving chromatin alterations. We speculate that HAMLET and HDIs might be combined to promote tumor cell death in vivo.
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| 2. |
- Düringer, Caroline, et al.
(författare)
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Agonist-specific patterns of beta(2)-adrenoceptor responses in human airway cells during prolonged exposure.
- 2009
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Ingår i: British Journal of Pharmacology. - : Wiley. - 1476-5381 .- 0007-1188. ; 158, s. 169-179
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: beta(2)-Adrenoceptor agonists (beta(2)-agonists) are important bronchodilators used in the treatment of asthma and chronic obstructive pulmonary disease. At the molecular level, beta(2)-adrenergic agonist stimulation induces desensitization of the beta(2)-adrenoceptor. In this study, we have examined the relationships between initial effect and subsequent reduction of responsiveness to restimulation for a panel of beta(2)-agonists in cellular and in vitro tissue models. Experimental approach: beta(2)-Adrenoceptor-induced responses and subsequent loss of receptor responsiveness were studied in primary human airway smooth muscle cells and bronchial epithelial cells by measuring cAMP production. Receptor responsiveness was compared at equi-effective concentrations, either after continuous incubation for 24 h or after a 1 h pulse exposure followed by a 23 h washout. Key findings were confirmed in guinea pig tracheal preparations in vitro. Key results: There were differences in the reduction of receptor responsiveness in human airway cells and in vitro guinea pig trachea by a panel of beta(2)-agonists. When restimulation occurred immediately after continuous incubation, loss of responsiveness correlated with initial effect for all agonists. After the 1 h pulse exposure, differences between agonists emerged, for example isoprenaline and formoterol induced the least reduction of responsiveness. High lipophilicity was, to some extent, predictive of loss of responsiveness, but other factors appeared to be involved in determining the relationships between effect and subsequent loss of responsiveness for individual agonists. Conclusions and implications: There were clear differences in the ability of different beta(2) agonists to induce loss of receptor responsiveness at equi-effective concentrations.
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| 3. |
- Düringer, Caroline, et al.
(författare)
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HAMLET; a novel tool to identify apoptotic pathways in tumor cells.
- 2005
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Ingår i: Application of apoptosis to cancer treatment.. - Berlin/Heidelberg : Springer-Verlag. - 9781402033032 ; , s. 223-245
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Tumor cells often carry mutations in genes that control cell survival, and become resistant to signals that trigger cell death. Yet, some cell death pathways remain intact in tumor cells. If identified, these pathways might be exploited to selectively remove tumor cells. HAMLET (human α-lactalbumin made lethal to tumor cells) is a protein-lipid complex derived from human milk that activates cell death programs in tumor cells but not in healthy differentiated cells. We use HAMLET as a tool to identify apoptosis and apoptosis-like cell death mechanisms in tumor cells and to understand if these mechanisms differ between tumor and healthy cells. HAMLET interacts with the cell surface, translocates into the cytoplasm and accumulates in cell nuclei, where it disrupts the chromatin. Recent in vivo studies have shown that HAMLET maintains the tumoricidal activity in glioblastoma, papilloma and bladder cancer models, with no significant side effects. The results suggest that HAMLET should be explored as a new therapeutic agent with selectivity for the tumor and with little toxicity for adjacent healthy tissue. Such therapies are a much-needed complement to conventional treatments, to reduce the side effects and improve the selectivity.
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| 4. |
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| 5. |
- Düringer, Caroline
(författare)
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Nuclear mechanisms in cell death induced by HAMLET (human alpha-lactalbumin made lethal to tumour cells)
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- HAMLET (human alpha-lactalbumin made lethal to tumour cells), a protein-lipid complex originally isolated from human milk, induces programmed cell death selectively in tumour cells. It consists of partially unfolded alpha-lactalbumin in complex with oleic acid. It was previously not known if the unfolding of alpha-lactalbumin alone accounts for the activity of HAMLET or if the lipid adds biological activity. This was investigated using alpha-lactalbumin mutants that are present in the unfolded state at physiological conditions. These proteins were not active in cell death assays but could be converted to biologically active complexes with oleic acid, showing that unfolding of alpha-lactalbumin is not sufficient and that lipid structures are required for the cell death-inducing activity of HAMLET. HAMLET targets and accumulates in nuclei of sensitive cells but does not reach the nuclei of resistant cells, suggesting that a nuclear effect may be important for the cell death induction. We identified histones as nuclear targets for HAMLET, and HAMLET interacted with both denatured and native histones, as well as with histones in nucleosomes. In vivo, in tumour cell nuclei, HAMLET colocalised with histones and perturbed the global chromatin structure. The interaction with histones required partial unfolding of alpha-lactalbumin, achieved either by removal of calcium from the protein or conversion to HAMLET-like complexes with lipids. The lipid stabilised a histone-binding conformation of alpha-lactalbumin, but did not contribute to the binding specificity. Although there was a species variation in the ability of alpha-lactalbumin to bind histones, all but one of the biologically active HAMLET-like complexes tested were able to interact with histones. The HAMLET-histone interaction may induce damage to the chromatin, and cell death resulting from nuclear damage is often signalled through the p53 system. However, using cells with defined p53 status, we found no correlation between p53 and sensitivity of cells to HAMLET. We propose that the interaction of HAMLET with histones in the nuclei of tumour cells may lead to cell death in a p53-independent manner by disrupting the structure and function of chromatin.
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| 6. |
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| 7. |
- Svanborg, Catharina, et al.
(författare)
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HAMLET kills tumor cells by an apoptosis-like mechanism--cellular, molecular, and therapeutic aspects.
- 2003
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Ingår i: Advances in Cancer Research. - 0065-230X. ; 88, s. 1-29
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Forskningsöversikt (refereegranskat)abstract
- HAMLET (human α-lactalbumin made lethal to tumor cells) is a protein-lipid complex that induces apoptosis-like death in tumor cells, but leaves fully differentiated cells unaffected. This review summarizes the information on the in vivo effects of HAMLET in patients and tumor models, on the tumor cell biology, and on the molecular characteristics of the complex. HAMLET limits the progression of human glioblastomas in a xenograft model and removes skin papillomas in patients. This broad anti-tumor activity includes >40 different lymphomas and carcinomas and apoptosis is independent of p53 or bcl-2. In tumor cells, HAMLET enters the cytoplasm, translocates to the perinuclear area, and enters the nuclei, where it accumulates. HAMLET binds strongly to histones and disrupts the chromatin organization. In the cytoplasm, HAMLET targets ribosomes and activates caspases. The formation of HAMLET relies on the propensity of α-lactalbumin to alter its conformation when the strongly bound Ca2+ ion is released and the protein adopts the apo-conformation that exposes a new fatty acid binding site. Oleic acid (C18:1,9 cis) fits this site with high specificity, and stabilizes the altered protein conformation. The results illustrate how protein folding variants may be beneficial, and how their formation in peripheral tissues may depend on the folding change and the availability of the lipid cofactor. One example is the acid pH in the stomach of the breast-fed child that promotes the formation of HAMLET This mechanism may contribute to the protective effect of breastfeeding against childhood tumors. We propose that HAMLET should be explored as a novel approach to tumor therapy.
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| 8. |
- Svensson, Malin, et al.
(författare)
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alpha-Lactalbumin unfolding is not sufficient to cause apoptosis, but is required for the conversion to HAMLET (human alpha-lactalbumin made lethal to tumor cells).
- 2003
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Ingår i: Protein Science. - : Wiley. - 1469-896X .- 0961-8368. ; 12:12, s. 2794-2804
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Tidskriftsartikel (refereegranskat)abstract
- HAMLET (human -lactalbumin made lethal to tumor cells) is a complex of human -lactalbumin and oleic acid (C18:1:9 cis) that kills tumor cells by an apoptosis-like mechanism. Previous studies have shown that a conformational change is required to form HAMLET from -lactalbumin, and that a partially unfolded conformation is maintained in the HAMLET complex. This study examined if unfolding of -lactalbumin is sufficient to induce cell death. We used the bovine -lactalbumin Ca2+ site mutant D87A, which is unable to bind Ca2+, and thus remains partially unfolded regardless of solvent conditions. The D87A mutant protein was found to be inactive in the apoptosis assay, but could readily be converted to a HAMLET-like complex in the presence of oleic acid. BAMLET (bovine -lactalbumin made lethal to tumor cells) and D87A-BAMLET complexes were both able to kill tumor cells. This activity was independent of the Ca2+site, as HAMLET maintained a high affinity for Ca2+ but D87A-BAMLET was active with no Ca2+ bound. We conclude that partial unfolding of -lactalbumin is necessary but not sufficient to trigger cell death, and that the activity of HAMLET is defined both by the protein and the lipid cofactor. Furthermore, a functional Ca2+-binding site is not required for conversion of -lactalbumin to the active complex or to cause cell death. This suggests that the lipid cofactor stabilizes the altered fold without interfering with the Ca2+site.
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