Open multistate Majorana model

The multistate Majorana model in the presence of dissipation and dephasing is considered. It is proven that increasing the Hilbert space dimension the system becomes more and more fragile to quantum noise. The impossibility to recast the problem in the form of a set of independent spin-$1/2$ problems because of the presence of the noise is pointed out

Metabolic reprogramming of oncogene-addicted cancer cells to OXPHOS as a mechanism of drug resistance

The ability to selectively eradicate oncogene-addicted tumors while reducing systemic toxicity has endeared targeted therapies as a treatment strategy. Nevertheless, development of acquired resistance limits the benefits and durability of such a regime. Here we report evidence of enhanced reliance on mitochondrial oxidative phosphorylation (OXPHOS) in oncogene-addicted cancers manifesting acquired resistance to targeted therapies. To that effect, we describe a novel OXPHOS targeting activity of the small molecule compound, OPB-51602 (OPB). Of note, a priori treatment with OPB restored sensitivity to targeted therapies. Furthermore, cancer cells exhibiting stemness markers also showed selective reliance on OXPHOS and enhanced sensitivity to OPB. Importantly, in a subset of patients who developed secondary resistance to EGFR tyrosine kinase inhibitor (TKI), OPB treatment resulted in decrease in metabolic activity and reduction in tumor size. Collectively, we show here a switch to mitochondrial OXPHOS as a key driver of targeted drug resistance in oncogene-addicted cancers. This metabolic vulnerability is exploited by a novel OXPHOS inhibitor, which also shows promise in the clinical setting

Mitochondrial respiration - an important therapeutic target in melanoma

The importance of mitochondria as oxygen sensors as well as producers of ATP and reactive oxygen species (ROS) has recently become a focal point of cancer research. However, in the case of melanoma, little information is available to what extent cellular bioenergetics processes contribute to the progression of the disease and related to it, whether oxidative phosphorylation (OXPHOS) has a prominent role in advanced melanoma. In this study we demonstrate that compared to melanocytes, metastatic melanoma cells have elevated levels of OXPHOS. Furthermore, treating metastatic melanoma cells with the drug, Elesclomol, which induces cancer cell apoptosis through oxidative stress, we document by way of stable isotope labeling with amino acids in cell culture (SILAC) that proteins participating in OXPHOS are downregulated. We also provide evidence that melanoma cells with high levels of glycolysis are more resistant to Elesclomol. We further show that Elesclomol upregulates hypoxia inducible factor 1-α (HIF-1α), and that prolonged exposure of melanoma cells to this drug leads to selection of melanoma cells with high levels of glycolysis. Taken together, our findings suggest that molecular targeting of OXPHOS may have efficacy for advanced melanoma. © 2012 Barbi de Moura et al

PARP Inhibitor PJ34 Protects Mitochondria and Induces DNA-Damage Mediated Apoptosis in Combination With Cisplatin or Temozolomide in B16F10 Melanoma Cells

<p>PARP-1 inhibition has recently been employed in both mono- and combination therapies in various malignancies including melanoma with both promising and contradicting results reported. Although deeper understanding of the underlying molecular mechanisms may help improving clinical modalities, the complex cellular effects of PARP inhibitors make disentangling of the mechanisms involved in combination therapies difficult. Here, we used two cytostatic agents used in melanoma therapies in combination with PARP inhibition to have an insight into cellular events using the B16F10 melanoma model. We found that, when used in combination with cisplatin or temozolomide, pharmacologic blockade of PARP-1 by PJ34 augmented the DNA-damaging and cytotoxic effects of both alkylating compounds. Interestingly, however, this synergism unfolds relatively slowly and is preceded by molecular events that are traditionally believed to support cell survival including the stabilization of mitochondrial membrane potential and morphology. Our data indicate that the PARP inhibitor PJ34 has, apparently, opposing effects on the mitochondrial structure and cell survival. While, initially, it stimulates mitochondrial fusion and hyperpolarization, hallmarks of mitochondrial protection, it enhances the cytotoxic effects of alkylating agents at later stages. These findings may contribute to the optimization of PARP inhibitor-based antineoplastic modalities.</p

WNT/β-catenin signaling regulates mitochondrial activity to alter the oncogenic potential of melanoma in a PTEN-dependent manner

Aberrant regulation of WNT/β-catenin signaling has a crucial role in the onset and progression of cancers, where the effects are not always predictable depending on tumor context. In melanoma, for example, models of the disease predict differing effects of the WNT/β-catenin pathway on metastatic progression. Understanding the processes that underpin the highly context-dependent nature of WNT/β-catenin signaling in tumors is essential to achieve maximal therapeutic benefit from WNT inhibitory compounds. In this study, we have found that expression of the tumor suppressor, phosphatase and tensin homolog deleted on chromosome 10 (PTEN), alters the invasive potential of melanoma cells in response to WNT/β-catenin signaling, correlating with differing metabolic profiles. This alters the bioenergetic potential and mitochondrial activity of melanoma cells, triggered through regulation of pro-survival autophagy. Thus, WNT/β-catenin signaling is a regulator of catabolic processes in cancer cells, which varies depending on the metabolic requirements of tumors

Clonagem e caracaterização funcional do gene da DNA polimerase de trypanosma cruzi

Exportado OPUSMade available in DSpace on 2019-08-12T17:37:43Z (GMT). No. of bitstreams: 1 michele_barbi_de_moura_resumo.dout.pdf: 25246 bytes, checksum: 9fef1a6f10c548aed8668b4e3745baf6 (MD5) Previous issue date: 24As células são constantemente expostas a diversos agentes de origem endógena ou exógena que causam lesões no DNA. Como estas lesões podem gerar mutações ou causar a morte celular, as células desenvolveram complexos sistemas de reparo para minimizar os danos, mantendo assim, a integridade do genoma. Entretanto, muitas lesões podem escapar das proteínas envolvidas no reparo e bloquear a maquinaria de replicação. Uma das maneiras encontradas pelas células para contornar esta situação foi desenvolver um mecanismo para realizar a síntese de DNA passando por estas lesões. Esse processo, denominado de síntese translesão, é realizado por um conjunto de DNA polimerases adaptadas a esta função, as polimerases da família Y. Ao contrário da maioria das polimerases, a Pol é capaz de replicar eficientemente a fita de DNA frente a uma variedade de lesões, como dímeros de timina, sítios AP e 8-oxoG, de uma forma livre de erros. Neste trabalho, nós clonamos e caracterizamos o gene da Pol de Trypanosoma cruzi, o agente causador da doença de Chagas. O gene TcPol codifica uma proteína que contém motivos que são conservados entre as polimerases da família Y. Ensaios in vitro demonstraram que a proteína recombinante é capaz de polimerizar diferentes moldes de DNA contendo ou não lesões. Apesar de complementar o fenótipo de sensibilidade à luz UV de leveduras que tiveram o gene RAD30 mutado, a superexpressão da TcPol em T. cruzi não aumentou a sobrevivência dos parasitos após tratamento com luz UV, cisplatina ou zeocina. A superexpressão também não foi capaz de promover a retomada do crescimento dos parasitos após a irradiação gama, mas aumentou a resistência destes após o tratamento com H2O2. Estes resultados sugerem que a TcPol pode ter um papel importante na síntese translesão de lesões oxidativas remanescente na fita de DNA durante a fase S, impedindo assim, o bloqueio da replicação.Cells are constantly exposed to endogenous or exogenous agents that cause injuries in DNA. These lesions can generate mutations or even lead to cellular death. A variety of repair mechanisms acts to maintain DNA integrity, but many lesions escape these processes leading to a replication fork blockage. To overcome this blockage, cells use a specialized group of DNA polymerases to bypass DNA lesions, restarting the replication forks and enhancing cell survival. This process is called translesion synthesis and is carried out by Y-family polymerases. Pol is member of this group and is able to bypass many type of lesions, as thymine-thymine dimer, AP sites and 8-oxoG. We report the cloning and characterization of the Pol gene (TcPol) from Trypanosoma cruzi, the causative agent of Chagas disease. This gene encodes protein containing motifs that are conserved between Y-family polymerases. In vitro assays showed that the recombinant protein is capable of synthesizing DNA in damage or undamaged primer-templates. Intriguingly, overexpression of TcPol does not increase resistance to UV light, cisplatin or zeocin, despite its ability to enhance UV resistance in a RAD30 mutant of Saccharomyces cerevisiae. T. cruzi overexpressing TcPol is also unable to restore growth after gamma irradiation, but T. cruzi cells overexpressing Pol are more resistant to treatment with hydrogen peroxide (H2O2). The results presented here suggest that TcPol plays an important role in the bypass of oxidative remanescent in DNA during S phase, stopping replication blockage

Sirtuin expression in HEK293 does not affect (A) the rate of cellular growth; (B) mitochondrial mass as judged by western blotting of electron transport chain components; (C)steady-state ATP under basal conditions or after the addition of the metabolic inhibitors etomoxir (Eto, 100 µM), oligomycin (oligo, 1 µM), 2-deoxyglucose (2DG, 100 mM), or combinations thereof; or (D) intramitochondrial NAD⁺.

<p>Growth was measured in quadruplicate wells in two separate experiments which were averaged. ATP was measured in triplicate wells containing equal numbers of cells in two separate experiments which were averaged. NAD+ was measured in three separate preparations of mitochondria and the results averaged. All data are means and standard deviations.</p

Seahorse XF24 extracellular flux analysis of sirtuin-expressing HEK293 cells under 5 mm glucose conditions.

<p>(A) Oxygen consumption and (B) extracellular acidification rates were measured under the same protocol as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106028#pone-0106028-g001" target="_blank">Figures 1</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106028#pone-0106028-g003" target="_blank">3</a>. All graphs depict means and standard deviations. mpH = milli pH units.</p

Effect of mitochondrial sirtuin expression on glycolysis.

<p>Seahorse extracellular acidification rates (A) were measured in quadruplicate wells containing equal numbers of cells. The experiment was repeated with similar results. Data collected over the first 30 minutes were averaged to yield the basal glycolytic rate (B). Oligomycin-stimulated glycolysis (C) was calculated by subtracting the basal values from the maximum values obtained immediately after oligomycin injection. The oxygen consumption/extracellular acidification ratio (D) was calculated by dividing the values shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106028#pone-0106028-g001" target="_blank">Figure 1D</a> by those in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106028#pone-0106028-g003" target="_blank">Figure 3B</a>. All graphs depict means and standard deviations, and *P<0.05. mpH = milli pH units.</p