scholarly journals Molecular imaging of the kinetics of hyperactivated ERK1/2-mediated autophagy during acquirement of chemoresistance

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Aniketh Bishnu ◽  
Pratham Phadte ◽  
Ajit Dhadve ◽  
Asmita Sakpal ◽  
Bharat Rekhi ◽  
...  
Keyword(s):  
Strong Association ◽  
Live Cells ◽  
Ovarian Cancer Cells ◽  
Autophagic Flux ◽  
Tumor Xenografts ◽  
Early Stages ◽  
Apoptosis Inhibition ◽  
Kinetics Of ◽  
Late Stages ◽  
Combinatorial Treatment

AbstractAlterations in key kinases and signaling pathways can fine-tune autophagic flux to promote the development of chemoresistance. Despite empirical evidences of strong association between enhanced autophagic flux with acquired chemoresistance, it is still not understood whether an ongoing autophagic flux is required for both initiation, as well as maintenance of chemoresistance, or is sufficient for one of the either steps. Utilizing indigenously developed cisplatin–paclitaxel-resistant models of ovarian cancer cells, we report an intriguing oscillation in chemotherapy-induced autophagic flux across stages of resistance, which was found to be specifically elevated at the early stages or onset of chemoresistance. Conversely, the sensitive cells and cells at late stages of resistance showed stalled and reduced autophagic flux. This increased flux at early stages of resistance was found to be dictated by a hyperactive ERK1/2 signaling, which when inhibited either pharmacologically (U0126/Trametinib) or genetically, reduced p62 degradation, number of LC3+veLAMP1+ve puncta, autophagolysosome formation, and led to chemo-sensitization and apoptosis. Inhibition of ERK1/2 activation also altered the level of UVRAG and Rab7, the two key proteins involved in autophagosome–lysosome fusion. Noninvasive imaging of autophagic flux using a novel autophagy sensor (mtFL-p62 fusion reporter) showed that combinatorial treatment of platinum–taxol along with Trametinib/chloroquine blocked autophagic flux in live cells and tumor xenografts. Interestingly, Trametinib was found to be equally effective in blocking autophagic flux as chloroquine both in live cells and tumor xenografts. Combinatorial treatment of Trametinib and platinum–taxol significantly reduced tumor growth. This is probably the first report of real-time monitoring of chemotherapy-induced autophagy kinetics through noninvasive bioluminescence imaging in preclinical mouse model. Altogether our data suggest that an activated ERK1/2 supports proper completion of autophagic flux at the onset of chemoresistance to endure initial chemotherapeutic insult and foster the development of a highly chemoresistant phenotype, where autophagy becomes dispensable.

Gadolinium Oxide Nanoparticles Enhance the Cytotoxicity of Chemotherapeutic Drugs by Blocking Autophagic Flux in Human Ovarian Cancer Cells

2020 ◽  
Vol 16 ◽  
Author(s):  
Zhixiong Xie ◽  
Tianyu Zhang ◽  
Cheng Zhong
Keyword(s):  
Ovarian Cancer ◽  
Cancer Cells ◽  
Hela Cells ◽  
Late Stage ◽  
Ovarian Cancer Cells ◽  
Oxide Nanoparticles ◽  
Autophagic Flux ◽  
Human Ovarian Cancer ◽  
Chemotherapeutic Drugs ◽  
Chemotherapy Drugs

Background: During chemotherapy, drugs can damage cancer cells’ DNA and cytomembrane structure, and then induce cell death. However, autophagy can increase the chemotherapy resistance of cancer cells, reducing the effect of chemotherapy. Objective: To block the autophagic flux in cancer cells, it is vital to enhance the anti-cancer efficacy of chemotherapy drugs; for this purpose, we test the gadolinium oxide nanoparticles (Gd2O3 NPs)’ effect on autophagy. Methods: The cytotoxicity of Gd2O3 NPs on HeLa cells was evaluated by a (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Then, monodasylcadaverine staining, immunofluorescence, immunoblot and apoptosis assay were conducted to evaluate the effect of Gd2O3 NPs on autophagy and efficacy of chemotherapy drugs in human ovarian cancer cells. Results: We found that Gd2O3 NPs, which have great potential for use as a contrast agent in magnetic resonance imaging, could block the late stage of autophagic flux in a dose-dependent manner and then cause autophagosome accumulation in HeLa cells. When co-treated with 8 μg/mL Gd2O3 NPs and 5 μg/mL cisplatin, the number of dead HeLa cells increased by about 20% compared with cisplatin alone. We observed the same phenomenon in cisplatin-resistant COC1/DDP cells. Conclusion: We conclude that Gd2O3 NPs can block the late stage of autophagic flux and enhance the cytotoxicity of chemotherapeutic drugs in human ovarian cancer cells. Thus, the nanoparticles have significant potential for use in both diagnosis and therapy of solid tumor.

scholarly journals Quinacrine-Induced Autophagy in Ovarian Cancer Triggers Cathepsin-L Mediated Lysosomal/Mitochondrial Membrane Permeabilization and Cell Death

Cancers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 2004
Author(s):  
Prabhu Thirusangu ◽  
Christopher L. Pathoulas ◽  
Upasana Ray ◽  
Yinan Xiao ◽  
Julie Staub ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Cell Death ◽  
Cytochrome C ◽  
Cancer Cells ◽  
Apoptotic Cell ◽  
Cathepsin L ◽  
Membrane Permeabilization ◽  
Apoptotic Cell Death ◽  
Ovarian Cancer Cells ◽  
Autophagic Flux

We previously reported that the antimalarial compound quinacrine (QC) induces autophagy in ovarian cancer cells. In the current study, we uncovered that QC significantly upregulates cathepsin L (CTSL) but not cathepsin B and D levels, implicating the specific role of CTSL in promoting QC-induced autophagic flux and apoptotic cell death in OC cells. Using a Magic Red® cathepsin L activity assay and LysoTracker red, we discerned that QC-induced CTSL activation promotes lysosomal membrane permeability (LMP) resulting in the release of active CTSL into the cytosol to promote apoptotic cell death. We found that QC-induced LMP and CTSL activation promotes Bid cleavage, mitochondrial outer membrane permeabilization (MOMP), and mitochondrial cytochrome-c release. Genetic (shRNA) and pharmacological (Z-FY(tBU)-DMK) inhibition of CTSL markedly reduces QC-induced autophagy, LMP, MOMP, apoptosis, and cell death; whereas induced overexpression of CTSL in ovarian cancer cell lines has an opposite effect. Using recombinant CTSL, we identified p62/SQSTM1 as a novel substrate of CTSL, suggesting that CTSL promotes QC-induced autophagic flux. CTSL activation is specific to QC-induced autophagy since no CTSL activation is seen in ATG5 knockout cells or with the anti-malarial autophagy-inhibiting drug chloroquine. Importantly, we showed that upregulation of CTSL in QC-treated HeyA8MDR xenografts corresponds with attenuation of p62, upregulation of LC3BII, cytochrome-c, tBid, cleaved PARP, and caspase3. Taken together, the data suggest that QC-induced autophagy and CTSL upregulation promote a positive feedback loop leading to excessive autophagic flux, LMP, and MOMP to promote QC-induced cell death in ovarian cancer cells.

scholarly journals KD determination from time-resolved experiments on live cells with LigandTracer and reconciliation with end-point flow cytometry measurements

2021 ◽  
Author(s):  
Diana Spiegelberg ◽  
Jonas Stenberg ◽  
Pascale Richalet ◽  
Marc Vanhove
Keyword(s):  
Flow Cytometry ◽  
Live Cells ◽  
Time Resolved ◽  
Surface Receptors ◽  
Full Characterization ◽  
End Point ◽  
Titration Curves ◽  
Kinetics Of

AbstractDesign of next-generation therapeutics comes with new challenges and emulates technology and methods to meet them. Characterizing the binding of either natural ligands or therapeutic proteins to cell-surface receptors, for which relevant recombinant versions may not exist, represents one of these challenges. Here we report the characterization of the interaction of five different antibody therapeutics (Trastuzumab, Rituximab, Panitumumab, Pertuzumab, and Cetuximab) with their cognate target receptors using LigandTracer. The method offers the advantage of being performed on live cells, alleviating the need for a recombinant source of the receptor. Furthermore, time-resolved measurements, in addition to allowing the determination of the affinity of the studied drug to its target, give access to the binding kinetics thereby providing a full characterization of the system. In this study, we also compared time-resolved LigandTracer data with end-point KD determination from flow cytometry experiments and hypothesize that discrepancies between these two approaches, when they exist, generally come from flow cytometry titration curves being acquired prior to full equilibration of the system. Our data, however, show that knowledge of the kinetics of the interaction allows to reconcile the data obtained by flow cytometry and LigandTracer and demonstrate the complementarity of these two methods.

scholarly journals SIMILARITY OF THE KINETICS OF INVERTASE ACTION IN VIVO AND IN VITRO. II

1932 ◽  
Vol 16 (2) ◽  
pp. 233-242 ◽  
Author(s):  
B. G. Wilkes ◽  
Elizabeth T. Palmer
Keyword(s):  
Physiological Activity ◽  
Outer Region ◽  
Living Cells ◽  
Yeast Cells ◽  
Live Cells ◽  
Intracellular Enzyme ◽  
Relationship Of ◽  
Kinetics Of

1. The pH-activity relationship of invertase has been studied in vivo and in vitro under identical external environmental conditions. 2. The effect of changing (H+) upon the sucroclastic activity of living cells of S. cerevisiae and of invertase solutions obtained therefrom has been found, within experimental error, to be identical. 3. The region of living yeast cells in which invertase exerts its physiological activity changes its pH freely and to the same extent as that of the suspending medium. It is suggested that this may indicate that this intracellular enzyme may perform its work somewhere in the outer region of the cell. 4. In using live cells containing maltase, no evidence of increased sucroclastic activity around pH 6.9, due to the action of Weidenhagen's α-glucosidase (maltase), was found.

scholarly journals Increasing autophagy does not affect neurogenic muscle atrophy

2018 ◽  
Vol 28 (3) ◽  
Author(s):  
Eva Pigna ◽  
Krizia Sanna ◽  
Dario Coletti ◽  
Zhenlin Li ◽  
Ara Parlakian ◽  
...  
Keyword(s):  
Muscle Mass ◽  
Muscle Atrophy ◽  
Ubiquitin Proteasome System ◽  
Autophagic Flux ◽  
Molecular Pathways ◽  
Muscle Loss ◽  
Relative Contribution ◽  
Ubiquitin Proteasome ◽  
Muscle Mass Loss ◽  
Kinetics Of

Physiological autophagy plays a crucial role in the regulation of muscle mass and metabolism, while the excessive induction or the inhibition of the autophagic flux contributes to the progression of several diseases. Autophagy can be activated by different stimuli, including cancer, exercise, caloric restriction and denervation. The latter leads to muscle atrophy through the activation of catabolic pathways, i.e. the ubiquitin-proteasome system and autophagy. However, the kinetics of autophagy activation and the upstream molecular pathways in denervated skeletal muscle have not been reported yet. In this study, we characterized the kinetics of autophagic induction, quickly triggered by denervation, and report the Akt/mTOR axis activation. Besides, with the aim to assess the relative contribution of autophagy in neurogenic muscle atrophy, we triggered autophagy with different stimuli along with denervation, and observed that four week-long autophagic induction, by either intermitted fasting or rapamycin treatment, did not significantly affect muscle mass loss. We conclude that: i) autophagy does not play a major role in inducing muscle loss following denervation; ii) nonetheless, autophagy may have a regulatory role in denervation induced muscle atrophy, since it is significantly upregulated as early as eight hours after denervation; iii) Akt/mTOR axis, AMPK and FoxO3a are activated consistently with the progression of muscle atrophy, further highlighting the complexity of the signaling response to the atrophying stimulus deriving from denervation.

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