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Mark M. Kockx

Bio: Mark M. Kockx is an academic researcher from University of Antwerp. The author has contributed to research in topics: Apoptosis & Programmed cell death. The author has an hindex of 55, co-authored 153 publications receiving 11076 citations.


Papers
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TL;DR: In this article, the authors performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib.
Abstract: Background Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors. Methods We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed. Results Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L–mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)–pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L–mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or...

937 citations

Journal ArticleDOI
TL;DR: The Blueprint (BP) Programmed Death Ligand 1 (PD-L1) Immunohistochemistry Comparability Project is a pivotal academic/professional society and industrial collaboration to assess the feasibility of harmonizing the clinical use of five independently developed commercial PD-L 1 immunohistochemical assays.

550 citations

Journal ArticleDOI
TL;DR: It is demonstrated that phagocytosis of ACs is impaired in atherosclerotic plaques, which is at least partly attributed to oxidative stress and cytoplasmic saturation with indigestible material.
Abstract: Objective— Apoptotic cell death has been demonstrated in advanced human atherosclerotic plaques. Apoptotic cells (ACs) should be rapidly removed by macrophages, otherwise secondary necrosis occurs, which in turn elicits inflammatory responses and plaque progression. Therefore, we investigated the efficiency of phagocytosis of ACs by macrophages in atherosclerosis. Methods and Results— Human endarterectomy specimens and human tonsils were costained for CD68 (macrophages) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) (apoptosis). Free and phagocytized ACs were counted in both tissues. The ratio of free versus phagocytized AC was 19-times higher in human atherosclerotic plaques as compared with human tonsils, indicating a severe defect in clearance of AC. Impaired phagocytosis of AC was also detected in plaques from cholesterol-fed rabbits and did not further change with plaque progression. In vitro experiments with J774 or peritoneal mouse macrophages showed that several factors caused impaired phagocytosis of AC including cytoplasmic overload of macrophages with indigestible material (beads), free radical attack, and competitive inhibition among oxidized red blood cells, oxidized low-density lipoprotein and ACs for the same receptor(s) on the macrophage. Conclusion— Our data demonstrate that phagocytosis of ACs is impaired in atherosclerotic plaques, which is at least partly attributed to oxidative stress and cytoplasmic saturation with indigestible material.

439 citations

Journal ArticleDOI
TL;DR: It is concluded that SMCs within human fatty streaks express BAX, which increases the susceptibility of these cells to undergo apoptosis, which could be important in the understanding of the transition of fatty streaks into atherosclerotic plaques, which are characterized by regions of cell death.
Abstract: Background—The transition of a fatty streak into an atherosclerotic plaque is characterized by the appearance of focal and diffuse regions of cell death. We have investigated the distribution of apoptotic cell death and apoptosis-related proteins in early and advanced atherosclerotic lesions. Methods and Results—Human atherosclerotic plaques were studied by whole-mount carotid endarterectomy specimens (n=18). This approach allowed comparison of adaptive intimal thickenings, fatty streaks, and advanced atherosclerotic plaques of the same patient. The fatty streaks differed from adaptive intimal thickenings by the presence of BAX (P<0.01), a proapoptotic protein of the BCL-2 family. Both regions were composed mainly of smooth muscle cells (SMCs), and macrophage infiltration was low and not different. Apoptosis, as detected by DNA in situ end labeling (terminal deoxynucleotidyl transferase end labeling [TUNEL] and in situ nick translation) was not present in these regions. Apoptosis of SMCs and macrophages, ...

428 citations

Journal ArticleDOI
TL;DR: Evidence is provided that oxidative DNA damage and repair increase significantly in human atherosclerotic plaques and this is accompanied by the upregulation of DNA repair mechanisms.
Abstract: Background— The formation of reactive oxygen species is a critical event in atherosclerosis because it promotes cell proliferation, hypertrophy, growth arrest, and/or apoptosis and oxidation of LDL. In the present study, we investigated whether reactive oxygen species-induced oxidative damage to DNA occurs in human atherosclerotic plaques and whether this is accompanied by the upregulation of DNA repair mechanisms. Methods and Results— We observed increased immunoreactivity against the oxidative DNA damage marker 7,8-dihydro-8-oxo-2′-deoxyguanosine (8-oxo-dG) in plaques of the carotid artery compared with the adjacent inner media and nonatherosclerotic mammary arteries. Strong 8-oxo-dG immunoreactivity was found in all cell types of the plaque including macrophages, smooth muscle cells, and endothelial cells. As shown by competitive ELISA, carotid plaques contained 160±29 8-oxo-dG residues/105 dG versus 3±1 8-oxo-dG residues/105 dG in mammary arteries. Single-cell gel electrophoresis showed elevated level...

405 citations


Cited by
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TL;DR: Current evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion, which is presented in detail in this review.
Abstract: The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

5,514 citations

Journal ArticleDOI
Daniel J. Klionsky1, Kotb Abdelmohsen2, Akihisa Abe3, Joynal Abedin4  +2519 moreInstitutions (695)
TL;DR: In this paper, the authors present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macro-autophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes.
Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular assays, we hope to encourage technical innovation in the field.

5,187 citations

Journal ArticleDOI
TL;DR: These guidelines are presented for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes.
Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.

4,316 citations

Journal ArticleDOI
TL;DR: This review will discuss the activation and function of NF-κB in association with inflammatory diseases and highlight the development of therapeutic strategies based on NF-σB inhibition.
Abstract: The transcription factor NF-κB regulates multiple aspects of innate and adaptive immune functions and serves as a pivotal mediator of inflammatory responses. NF-κB induces the expression of various pro-inflammatory genes, including those encoding cytokines and chemokines, and also participates in inflammasome regulation. In addition, NF-κB plays a critical role in regulating the survival, activation and differentiation of innate immune cells and inflammatory T cells. Consequently, deregulated NF-κB activation contributes to the pathogenic processes of various inflammatory diseases. In this review, we will discuss the activation and function of NF-κB in association with inflammatory diseases and highlight the development of therapeutic strategies based on NF-κB inhibition.

4,110 citations

Journal ArticleDOI
Lorenzo Galluzzi1, Lorenzo Galluzzi2, Ilio Vitale3, Stuart A. Aaronson4  +183 moreInstitutions (111)
TL;DR: The Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives.
Abstract: Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

3,301 citations