Paclitaxel resistance development is associated with biphasic changes in reactive oxygen species, mitochondrial membrane potential and autophagy with elevated energy production capacity in lung cancer cells: A chronological study.
01 Feb 2017-Tumor Biology (Tumour Biol)-Vol. 39, Iss: 2, pp 1010428317694314
TL;DR: Increase in activity of catalase, glutathione peroxidase and glutathion content over these periods may attribute in bringing down the reactive oxygen species levels and normalisation of mitochondrial membrane potential in spite of comparatively higher reactive oxygen Species production by the Tx-resistant cells.
Abstract: Paclitaxel (Tx) is one of the first-line chemotherapeutic drugs used against lung cancer, but acquired resistance to this drug is a major challenge against successful chemotherapy. In this work, we...
TL;DR: Autophagy inhibition by CQ pre-treatment can be used as a fruitful strategy to combat the phenomenon of paclitaxel resistance development as well as metastasis in lung cancer.
Abstract: Paclitaxel is one of the most commonly used drugs for the treatment of nonsmall cell lung cancer (NSCLC). However acquired resistance to paclitaxel, epithelial to mesenchymal transition and cancer stem cell formation are the major obstacles for successful chemotherapy with this drug. Some of the major reasons behind chemoresistance development include increased ability of the cancer cells to survive under stress conditions by autophagy, increased expression of drug efflux pumps, tubulin mutations etc. In this study we found that inhibition of autophagy with chloroquine prevented development of paclitaxel resistance in A549 cells with time and potentiated the effect of paclitaxel by increased accumulation of superoxide-producing damaged mitochondria, with elevated ROS generation, it also increased the apoptotic rate and sub G0/ G1 phase arrest with time in A549 cells treated with paclitaxel and attenuated the metastatic potential and cancer stem cell population of the paclitaxel-resistant cells by ROS mediated modulation of the Wnt/β-catenin signaling pathway, thereby increasing paclitaxel sensitivity. ROS here played a crucial role in modulating Akt activity when autophagy process was hindered by chloroquine, excessive ROS accumulation in the cell inhibited Akt activity. In addition, chloroquine pre-treatment followed by taxol (10 nM) treatment did not show significant toxicity towards non-carcinomas WI38 cells (lung fibroblast cells). Thus autophagy inhibition by CQ pre-treatment can be used as a fruitful strategy to combat the phenomenon of paclitaxel resistance development as well as metastasis in lung cancer.
TL;DR: Insight is provided into systems-level changes to protein structures and interactions that occur with paclitaxel treatment in known drug targets including tubulins, as well as many other proteins and protein complexes involved in apoptotic signaling and cellular homeostasis.
Abstract: Cell-cycle inhibitors, including paclitaxel, are among the most widely used and effective cancer therapies. However, several challenges limit the success of paclitaxel, including drug resistance and toxic side effects. Paclitaxel is thought to act primarily by stabilizing microtubules, locking cells in a mitotic state. However, the resulting cytotoxicity and tumor shrinkage rates observed cannot be fully explained by this mechanism alone. Here we apply quantitative chemical cross-linking with mass spectrometry analysis to paclitaxel-treated cells. Our results provide large-scale measurements of relative protein levels and, perhaps more importantly, changes to protein conformations and interactions that occur upon paclitaxel treatment. Drug concentration-dependent changes are revealed in known drug targets including tubulins, as well as many other proteins and protein complexes involved in apoptotic signaling and cellular homeostasis. As such, this study provides insight into systems-level changes to protein structures and interactions that occur with paclitaxel treatment.
TL;DR: Heme plays a pivotal role in OXPHOS and oxygen consumption and the lesser explored area of heme metabolism in lung cancer is delved into.
Abstract: Contrary to Warburg’s hypothesis, mitochondrial oxidative phosphorylation (OXPHOS) contributes significantly to fueling cancer cells. Several recent studies have demonstrated that radiotherapy-resistant and chemotherapy-resistant cancer cells depend on OXPHOS for survival and progression. Several cancers exhibit an increased risk in association with heme intake. Mitochondria are widely known to carry out oxidative phosphorylation. In addition, mitochondria are also involved in heme synthesis. Heme serves as a prosthetic group for several proteins that constitute the complexes of mitochondrial electron transport chain. Therefore, heme plays a pivotal role in OXPHOS and oxygen consumption. Further, lung cancer cells exhibit heme accumulation and require heme for proliferation and invasion in vitro. Abnormalities in mitochondrial biogenesis and mutations are implicated in cancer. This review delves into mitochondrial OXPHOS and lesser explored area of heme metabolism in lung cancer.
TL;DR: This work focuses on the causes of taxane resistance, and envisages an integrated model of the 'taxane resistance phenome', which could help the development of novel therapeutic strategies to treat taxane-resistant neoplasms.
Abstract: Taxanes are chemotherapeutic drugs employed in the clinic to treat a variety of malignancies. Despite their overall efficacy, cancer cells often display resistance to taxanes. Therefore, new strategies to increase the effectiveness of taxane-based chemotherapeutics are urgently needed. Multiple molecular players are linked to taxane resistance; these include efflux pumps, DNA repair mechanisms, and hypoxia-related pathways. In addition, emerging evidence indicates that both non-coding RNAs and epigenetic effectors might also be implicated in taxane resistance. Here we focus on the causes of taxane resistance, with the aim to envisage an integrated model of the 'taxane resistance phenome'. This model could help the development of novel therapeutic strategies to treat taxane-resistant neoplasms.
TL;DR: A comprehensive overview of the miRNA network involved in docetaxel resistance is described, highlighting the pathway/s affected by their activity.
Abstract: One of the main problems with the treatment of metastatic prostate cancer is that, despite an initial positive response, the majority of patients develop resistance and progress. In particular, the resistance to docetaxel, the gold standard therapy for metastatic prostate cancer since 2010, represents one of the main factors responsible for the failure of prostate cancer therapy. According to the present knowledge, different processes contribute to the appearance of docetaxel resistance and non-coding RNA seems to play a relevant role in them. In this review, a comprehensive overview of the miRNA network involved in docetaxel resistance is described, highlighting the pathway/s affected by their activity.
TL;DR: This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr with little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose.
Abstract: A protein determination method which involves the binding of Coomassie Brilliant Blue G-250 to protein is described. The binding of the dye to protein causes a shift in the absorption maximum of the dye from 465 to 595 nm, and it is the increase in absorption at 595 nm which is monitored. This assay is very reproducible and rapid with the dye binding process virtually complete in approximately 2 min with good color stability for 1 hr. There is little or no interference from cations such as sodium or potassium nor from carbohydrates such as sucrose. A small amount of color is developed in the presence of strongly alkaline buffering agents, but the assay may be run accurately by the use of proper buffer controls. The only components found to give excessive interfering color in the assay are relatively large amounts of detergents such as sodium dodecyl sulfate, Triton X-100, and commercial glassware detergents. Interference by small amounts of detergent may be eliminated by the use of proper controls.
TL;DR: It is proposed that the metabolism of cancer cells, and indeed all proliferating cells, is adapted to facilitate the uptake and incorporation of nutrients into the biomass needed to produce a new cell.
Abstract: In contrast to normal differentiated cells, which rely primarily on mitochondrial oxidative phosphorylation to generate the energy needed for cellular processes, most cancer cells instead rely on aerobic glycolysis, a phenomenon termed “the Warburg effect.” Aerobic glycolysis is an inefficient way to generate adenosine 5′-triphosphate (ATP), however, and the advantage it confers to cancer cells has been unclear. Here we propose that the metabolism of cancer cells, and indeed all proliferating cells, is adapted to facilitate the uptake and incorporation of nutrients into the biomass (e.g., nucleotides, amino acids, and lipids) needed to produce a new cell. Supporting this idea are recent studies showing that (i) several signaling pathways implicated in cell proliferation also regulate metabolic pathways that incorporate nutrients into biomass; and that (ii) certain cancer-associated mutations enable cancer cells to acquire and metabolize nutrients in a manner conducive to proliferation rather than efficient ATP production. A better understanding of the mechanistic links between cellular metabolism and growth control may ultimately lead to better treatments for human cancer.
TL;DR: A quantitative, spectrophotometric technique for following the breakdown of hydrogen peroxide has been developed for routine studies of catalase kinetics and appears to give lower values forCatalase activity than do titration techniques.
Abstract: Several methods have been developed for following the breakdown of hydrogen peroxide catalyzed by catalase, but these either have not been sufficiently quantitative or have not proved rapid enough to yield reliable data during the critical 1st or 2nd minute of the reaction. Chemical procedures in which residual peroxide is titrated with permanganate (l-3) or an excess of permanganate is measured calorimetrically (4) are accurate except for reaction times of less than a minute, although Lemberg and Foulkes (5) developed a micromethod for obtaining data every 10 seconds (see also Ogura et al. (6)). Considerable variability is unavoidable, however, when samples must-be taken at such short intervals. The manometric method for measuring oxygen evolved from the system proved in detailed studies to be unsuited for following the rapid breakdown of peroxide in which a diffusion process across the liquid-air interface becomes limiting. This is manifested by changes in both the order of the reaction and the rate of evolution of oxygen with variations in the rate of agitation of the reaction mixture (7). Direct measurement of hydrogen peroxide by polarography provides good quantitative data during the 1st minute of the reaction which fit first order kinetics (8). However, an elaborate, special, electronic circuit is needed for such measurements. Furthermore, as pointed out by Bonmschen, Chance, and Theorell (8), this method appears to give lower values for catalase activity than do titration techniques. Preliminary experiments for following the breakdown of hydrogen peroxide by observing the decrease in light absorption of peroxide solutions in the ultraviolet were reported by Chance (9) and Chance and Herbert (10). The potentialities of this method have been investigated and a quantitative, spectrophotometric technique for following the breakdown of hydrogen peroxide has been developed for routine studies of catalase kinetics.
TL;DR: Because malignant tumors no longer execute functions necessary for homeostasis (such as the production of adequate amounts of adenosine triphosphate), the physiology-based definitions of the term "hypoxia" are not necessarily valid for malignant tumor patients.
Abstract: Tissue hypoxia results from an inadequate supply of oxygen (O(2)) that compromises biologic functions. Evidence from experimental and clinical studies increasingly points to a fundamental role for hypoxia in solid tumors. Hypoxia in tumors is primarily a pathophysiologic consequence of structurally and functionally disturbed microcirculation and the deterioration of diffusion conditions. Tumor hypoxia appears to be strongly associated with tumor propagation, malignant progression, and resistance to therapy, and it has thus become a central issue in tumor physiology and cancer treatment. Biochemists and clinicians (as well as physiologists) define hypoxia differently; biochemists define it as O(2)-limited electron transport, and physiologists and clinicians define it as a state of reduced O(2) availability or decreased O(2) partial pressure that restricts or even abolishes functions of organs, tissues, or cells. Because malignant tumors no longer execute functions necessary for homeostasis (such as the production of adequate amounts of adenosine triphosphate), the physiology-based definitions of the term "hypoxia" are not necessarily valid for malignant tumors. Instead, alternative definitions based on clinical, biologic, and molecular effects that are observed at O(2) partial pressures below a critical level have to be applied.