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Kwang Woon Kim

Bio: Kwang Woon Kim is an academic researcher from Vanderbilt University. The author has contributed to research in topics: Programmed cell death & Clonogenic assay. The author has an hindex of 30, co-authored 43 publications receiving 7551 citations. Previous affiliations of Kwang Woon Kim include Pusan National University & Vanderbilt University Medical Center.

Papers
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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: Testing the ability of the mTOR inhibitor RAD001 (everolimus) to enhance the cytotoxic effects of radiation on two prostate cancer cell lines found that both cell lines became more vulnerable to irradiation after treatment with RAD001, with the PTEN-deficient PC-3 cell line showing the greater sensitivity.
Abstract: The phosphatidylinositol 3-kinase/Akt pathway plays a critical role in oncogenesis, and dysregulation of this pathway through loss of PTEN suppression is a particularly common phenomenon in aggressive prostate cancers. The mammalian target of rapamycin (mTOR) is a downstream signaling kinase in this pathway, exerting prosurvival influence on cells through the activation of factors involved in protein synthesis. The mTOR inhibitor rapamycin and its derivatives are cytotoxic to a number of cell lines. Recently, mTOR inhibition has also been shown to radiosensitize endothelial and breast cancer cells in vitro. Because radiation is an important modality in the treatment of prostate cancer, we tested the ability of the mTOR inhibitor RAD001 (everolimus) to enhance the cytotoxic effects of radiation on two prostate cancer cell lines, PC-3 and DU145. We found that both cell lines became more vulnerable to irradiation after treatment with RAD001, with the PTEN-deficient PC-3 cell line showing the greater sensitivity. This increased susceptibility to radiation is associated with induction of autophagy. Furthermore, we show that blocking apoptosis with caspase inhibition and Bax/Bak small interfering RNA in these cell lines enhances radiation-induced mortality and induces autophagy. Together, these data highlight the emerging importance of mTOR as a molecular target for therapeutic intervention, and lend support to the idea that nonapoptotic modes of cell death may play a crucial role in improving tumor cell kill.

338 citations

Journal ArticleDOI
TL;DR: It is concluded that PARP-1 inhibition shows promise as an effective means of enhancing tumor sensitivity to radiation, and future clinical studies are needed to determine the potential of ABT-888 as a radiation enhancer.
Abstract: Purpose: Poly(ADP-ribose) polymerase-1 (PARP-1) is the founding member of a family of enzymes that catalyze the addition of ADP-ribose units to proteins that mediate DNA repair pathways. Ionizing radiation induces DNA strand breaks, suggesting that PARP-1 inhibition may sensitize tumor cells to radiation. Experimental Design: We investigated the combination of PARP-1 inhibition with radiation in lung cancer models. ABT-888, a novel potent PARP-1 inhibitor, was used to explore the effects of PARP-1 inhibition on irradiated tumors and tumor vasculature. Results: ABT-888 reduced clonogenic survival in H460 lung cancer cells, and inhibited DNA repair as shown by enhanced expression of DNA strand break marker histone γ-H2AX. Both apoptosis and autophagy contributed to the mechanism of increased cell death. Additionally, ABT-888 increased tumor growth delay at well-tolerated doses in murine models. For a 5-fold increase in tumor volume, tumor growth delay was 1 day for ABT-888 alone, 7 days for radiation alone, and 13.5 days for combination treatment. Immunohistochemical staining of tumor sections revealed an increase in terminal deoxyribonucleotide transferase–mediated nick-end labeling apoptotic staining, and a decrease in Ki-67 proliferative staining after combination treatment. Matrigel assay showed a decrease in in vitro endothelial tubule formation with ABT-888/radiation combination treatment, and von Willebrand factor staining of tumor sections revealed decreased vessel formation in vivo , suggesting that this strategy may also target tumor angiogenesis. Conclusions: We conclude that PARP-1 inhibition shows promise as an effective means of enhancing tumor sensitivity to radiation, and future clinical studies are needed to determine the potential of ABT-888 as a radiation enhancer.

259 citations

Journal ArticleDOI
TL;DR: This is the first report to demonstrate that inhibition of pro-apoptotic proteins and induction of autophagy sensitizes cancer cells to therapy and Therapeutically targeting this novel pathway may yield significant benefits for cancer patients.

176 citations

Journal ArticleDOI
TL;DR: It is concluded that RAD001 attenuates radiation-induced prosurvival Akt/mTOR signaling and enhances the cytotoxic effects of radiation in breast cancer cell models, showing promise as a method of radiosensitization of breast cancer.
Abstract: The phosphatidylinositol 3-kinase (PI3K)/Akt pathway is known to be activated by radiation. The mammalian target of rapamycin (mTOR) is downstream of Akt, and we investigated the effects of radiation on Akt/mTOR signaling in breast cancer cell models. RAD001 (everolimus), a potent derivative of the mTOR inhibitor rapamycin, was used to study the effects of mTOR inhibition, as the role of mTOR inhibition in enhancing radiation remains unexplored. RAD001 decreased clonogenic cell survival in both breast cancer cell lines MDA-MB-231 and MCF-7, although the effect is greater in MDA-MB-231 cells. Irradiation induced Akt and mTOR signaling, and this signaling is attenuated by RAD001. The radiation-induced signaling activation is mediated by PI3K because inhibition of PI3K with LY294002 inhibited the increase in downstream mTOR signaling. Additionally, caspase-dependent apoptosis is an important mechanism of cell death when RAD001 is combined with 3 Gy radiation, as shown by induction of caspase-3 cleavage. An increase in G(2)-M cell cycle arrest was seen in the combination treatment group when compared with controls, suggesting that cell cycle arrest may have been a contributing factor in the increased radiosensitization seen in this study. We conclude that RAD001 attenuates radiation-induced prosurvival Akt/mTOR signaling and enhances the cytotoxic effects of radiation in breast cancer cell models, showing promise as a method of radiosensitization of breast cancer.

173 citations


Cited by
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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

Journal ArticleDOI
TL;DR: A functional classification of cell death subroutines is proposed that applies to both in vitro and in vivo settings and includes extrinsic apoptosis, caspase-dependent or -independent intrinsic programmed cell death, regulated necrosis, autophagic cell death and mitotic catastrophe.
Abstract: In 2009, the Nomenclature Committee on Cell Death (NCCD) proposed a set of recommendations for the definition of distinct cell death morphologies and for the appropriate use of cell death-related terminology, including 'apoptosis', 'necrosis' and 'mitotic catastrophe'. In view of the substantial progress in the biochemical and genetic exploration of cell death, time has come to switch from morphological to molecular definitions of cell death modalities. Here we propose a functional classification of cell death subroutines that applies to both in vitro and in vivo settings and includes extrinsic apoptosis, caspase-dependent or -independent intrinsic apoptosis, regulated necrosis, autophagic cell death and mitotic catastrophe. Moreover, we discuss the utility of expressions indicating additional cell death modalities. On the basis of the new, revised NCCD classification, cell death subroutines are defined by a series of precise, measurable biochemical features.

2,238 citations

Journal ArticleDOI
TL;DR: A way forward is suggested for the effective targeting of autophagy by understanding the context-dependent roles of autophile and by capitalizing on modern approaches to clinical trial design.
Abstract: Autophagy is a mechanism by which cellular material is delivered to lysosomes for degradation, leading to the basal turnover of cell components and providing energy and macromolecular precursors. Autophagy has opposing, context-dependent roles in cancer, and interventions to both stimulate and inhibit autophagy have been proposed as cancer therapies. This has led to the therapeutic targeting of autophagy in cancer to be sometimes viewed as controversial. In this Review, we suggest a way forwards for the effective targeting of autophagy by understanding the context-dependent roles of autophagy and by capitalizing on modern approaches to clinical trial design.

1,606 citations

Journal ArticleDOI
TL;DR: This work evaluates the accumulating body of literature that argues that cell death occurs by autophagy and lists the caveats that must be considered when deciding whether or notAutophagy is an important effector mechanism of cell death.
Abstract: Dying cells often display a large-scale accumulation of autophagosomes and hence adopt a morphology called autophagic cell death. In many cases, it is agreed that this autophagic cell death is cell death with autophagy rather than cell death by autophagy. Here, we evaluate the accumulating body of literature that argues that cell death occurs by autophagy. We also list the caveats that must be considered when deciding whether or not autophagy is an important effector mechanism of cell death.

1,383 citations