The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Alan S. B. Khoo - One of the best experts on this subject based on the ideXlab platform.
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Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma
Cell & Bioscience, 2016Co-Authors: Sang-nee Tan, Sai-peng Sim, Alan S. B. KhooAbstract:Background Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC. Results In the present study, we showed that hydrogen peroxide (H_2O_2) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of Caspases 3/7 was detected in H_2O_2-treated cells. This activity was inhibited by Caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H_2O_2-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H_2O_2-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia ( MLL ) gene in acute lymphoblastic leukemia (ALL) patient. Conclusions In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.
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Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma
Cell & bioscience, 2016Co-Authors: Sang‑nee Tan, Sai-peng Sim, Alan S. B. KhooAbstract:Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC. In the present study, we showed that hydrogen peroxide (H2O2) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of Caspases 3/7 was detected in H2O2-treated cells. This activity was inhibited by Caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H2O2-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H2O2-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia (MLL) gene in acute lymphoblastic leukemia (ALL) patient. In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.
Sai-peng Sim - One of the best experts on this subject based on the ideXlab platform.
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Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells: implications in chromosome rearrangement
BMC cancer, 2018Co-Authors: Sang-nee Tan, Sai-peng SimAbstract:Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, Caspase-Activated Deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC. We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and Caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, Caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced. BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and Caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a Caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient. These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells.
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Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells : implications in chromosome rearrangement
'Springer Science and Business Media LLC', 2018Co-Authors: Sang-nee Tan, Sai-peng SimAbstract:Background: Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, Caspase-Activated Deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC. Methods: We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and Caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, Caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced. Results: BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and Caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a Caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient. Conclusions: These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells
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Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma
Cell & Bioscience, 2016Co-Authors: Sang-nee Tan, Sai-peng Sim, Alan S. B. KhooAbstract:Background Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC. Results In the present study, we showed that hydrogen peroxide (H_2O_2) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of Caspases 3/7 was detected in H_2O_2-treated cells. This activity was inhibited by Caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H_2O_2-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H_2O_2-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia ( MLL ) gene in acute lymphoblastic leukemia (ALL) patient. Conclusions In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.
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Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma
Cell & bioscience, 2016Co-Authors: Sang‑nee Tan, Sai-peng Sim, Alan S. B. KhooAbstract:Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC. In the present study, we showed that hydrogen peroxide (H2O2) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of Caspases 3/7 was detected in H2O2-treated cells. This activity was inhibited by Caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H2O2-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H2O2-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia (MLL) gene in acute lymphoblastic leukemia (ALL) patient. In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.
Sang-nee Tan - One of the best experts on this subject based on the ideXlab platform.
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Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells: implications in chromosome rearrangement
BMC cancer, 2018Co-Authors: Sang-nee Tan, Sai-peng SimAbstract:Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, Caspase-Activated Deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC. We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and Caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, Caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced. BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and Caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a Caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient. These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells.
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Bile acids at neutral and acidic pH induce apoptosis and gene cleavages in nasopharyngeal epithelial cells : implications in chromosome rearrangement
'Springer Science and Business Media LLC', 2018Co-Authors: Sang-nee Tan, Sai-peng SimAbstract:Background: Chronic rhinosinusitis (CRS) increases the risk of developing nasopharyngeal carcinoma (NPC) while nasopharyngeal reflux is known to be one of the major aetiological factors of CRS. Bile acid (BA), the component of gastric duodenal contents, has been recognised as a carcinogen. BA-induced apoptosis was suggested to be involved in human malignancies. Cells have the potential and tendency to survive apoptosis. However, cells that evade apoptosis upon erroneous DNA repair may carry chromosome rearrangements. Apoptotic nuclease, Caspase-Activated Deoxyribonuclease (CAD) has been implicated in mediating translocation in leukaemia. We hypothesised that BA-induced apoptosis may cause chromosome breaks mediated by CAD leading to chromosome rearrangement in NPC. This study targeted the AF9 gene located at 9p22 because 9p22 is one of the most common deletion sites in NPC. Methods: We tested the ability of BA at neutral and acidic pH in inducing phosphatidylserine (PS) externalisation, reactive oxygen species (ROS) production, mitochondrial membrane potential (MMP) disruption, and Caspase 3/7 activity in normal nasopharyngeal epithelial (NP69) and NPC (TWO4) cells. Inverse-PCR (IPCR) was employed to detect AF9 gene cleavages. To investigate the role of CAD in mediating these cleavages, Caspase inhibition was performed. IPCR bands representing AF9 cleaved fragments were sequenced. Results: BA-treated cells showed higher levels of PS externalisation, ROS production, MMP loss and Caspase 3/7 activity than untreated control cells. The effect of BA in the induction of these intracellular events was enhanced by acid. BA at neutral and acidic pH also induced significant cleavage of the AF9 gene. These BA-induced gene cleavages were inhibited by Z-DEVD-FMK, a Caspase-3 inhibitor. Intriguingly, a few chromosome breaks were identified within the AF9 region that was previously reported to participate in reciprocal translocation between the mixed lineage leukaemia (MLL) and AF9 genes in an acute lymphoblastic leukaemia (ALL) patient. Conclusions: These findings suggest a role for BA-induced apoptosis in mediating chromosome rearrangements in NPC. In addition, CAD may be a key player in chromosome cleavages mediated by BA-induced apoptosis. Persistent exposure of sinonasal tract to gastric duodenal refluxate may increase genomic instability in surviving cells
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Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma
Cell & Bioscience, 2016Co-Authors: Sang-nee Tan, Sai-peng Sim, Alan S. B. KhooAbstract:Background Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC. Results In the present study, we showed that hydrogen peroxide (H_2O_2) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of Caspases 3/7 was detected in H_2O_2-treated cells. This activity was inhibited by Caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H_2O_2-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H_2O_2-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia ( MLL ) gene in acute lymphoblastic leukemia (ALL) patient. Conclusions In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.
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Identification of chromosome breaks mediated by stress-induced apoptosis in nasopharyngeal carcinoma (NPC)
2012Co-Authors: Sang-nee TanAbstract:hromOSOmal rearrangements such as additions and deletions are genomIc instability frequently observed in nasopharyngeal carcinoma (NPC). However, the molecular mechanism underlying the NPC chromosomal rearrangements remains elusive. Recently, there is increasing evidence that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation process in leukaemia. In normal cells, CAD exists as a complex with inhibitor of CAD (ICAD). ICAD possesses two Caspase-3 deavage sites which are cleaved by Caspase-3 when the apoptotic inducer is present. This releases the CAD from ICAD and allows it to degrade the chromosomal DNA. Although apoptosis is a cell death process, cells have the potential to survive apoptosis upon DNA repair) In human cells, chromosomal double-strand breaks (DSB) are primarily repaired by multiple repair pathways including non-homologous end joining (NHEJ) system. Non-homologous end joining pathway joins two cleaved DNA ends with microhomology, thus potentially resulting in erroneous DNA repair. Eventually, the surviving cells may carry chromosomal rearrangements. Apoptosis can be triggered by oxidative stress which occurs when the reactive oxygen species (ROS) generation exceeds the antioxidant defence capability. Oxidative DNA damage is strongly associated with carcinogenesis. It has recently become apparent that DNA breaks do not randomly distribute throughout a gene but usually cluster in certain regions containing specific chromatin structures. Matrix attachment region/scaffold attachment region (MARJSAR) is a binding site of DNA loop structure to nuclear scaffold proteins. It has DNA unwinding property which makes it to be a region of DNA fragility. This study hypothesised that stress-induced apoptosis may cause DNA breaks at MARJSAR and subsequently contribute to NPC chromosomal rearrangements in cells that survive apoptosis upon DNA repair. This study focused on the AF9 gene at 9p22 and the ABL gene at 9q34 because they are involved in translocations in leukaemia and are located at NPC common deletion sites. We aimed to identify DNA breaks mediated by stress-induced apoptosis, to relate the breakpoints to MARJSAR sites and to investigate the role of CAD in DNA cleavage mediated by stress-induced apoptosis. Upon hydrogen peroxide (H202) treatment, apoptotic evidence was observed in NPC and normal nasopharyngeal epithelial cells by flow cytometry. Numerous DNA breaks were detected in H202-treated NPC and normal nasopharyngeal epithelial cells by nested Inverse Polymerase Chain Reaction (IPCR). All breakpoints were mapped within close proximity to the MARJSAR sites. Besides, translocations were identified in H202-treated normal nasopharyngeal epithelial cells. Regions of microhomology were found at the translocation junctions. Furthermore, pre-treatment of Caspase inhibitor which indirectly inhibits CAD significantly reduced the DNA breaks in H202-cotreated NPC and nonnal nasopharyngeal epithelial cells. In addition, a comparison of SAR and non-SAR regions showed that there were more chromosomal breaks detected within the non-SAR region which is occupied by nearly 60% of repeat elements. However, these breaks are not H202 dependent. This result shows that repeat elements might play an important role in inducing spontaneous chromosomal breaks, but not in chromosomal cleavage mediated by stress-induced apoptosis. Taken together, these findings suggested that under oxidative stress, surviving apoptosis involving compromised DNA repair could be one of the mechanisms contributing to NPC carcinogenesis. Matrix attachment region/scaffold attachment region located at the base of chromosomal loop structure could be the preferential sites of chromosomal cleavage. The apoptotic nuclease CAD may play an important role in DNA cleavage mediated by oxidative stress-induced apoptosis. Therefore, a potential model for oxidative stress-induced chromosomal rearrangements in NPC is proposed.
Sang‑nee Tan - One of the best experts on this subject based on the ideXlab platform.
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Potential role of oxidative stress-induced apoptosis in mediating chromosomal rearrangements in nasopharyngeal carcinoma
Cell & bioscience, 2016Co-Authors: Sang‑nee Tan, Sai-peng Sim, Alan S. B. KhooAbstract:Genetic aberrations have been identified in nasopharyngeal carcinoma (NPC), however, the underlying mechanism remains elusive. There are increasing evidences that the apoptotic nuclease Caspase-Activated Deoxyribonuclease (CAD) is one of the players leading to translocation in leukemia. Oxidative stress, which has been strongly implicated in carcinogenesis, is a potent apoptotic inducer. Most of the NPC etiological factors are known to induce oxidative stress. Although apoptosis is a cell death process, cells possess the potential to survive apoptosis upon DNA repair. Eventually, the surviving cells may carry rearranged chromosomes. We hypothesized that oxidative stress-induced apoptosis may cause chromosomal breaks mediated by CAD. Upon erroneous DNA repair, cells that survive apoptosis may harbor chromosomal rearrangements contributing to NPC pathogenesis. This study focused on the AF9 gene at 9p22, a common deletion region in NPC. We aimed to propose a possible model for molecular mechanism underlying the chromosomal rearrangements in NPC. In the present study, we showed that hydrogen peroxide (H2O2) induced apoptosis in NPC (HK1) and normal nasopharyngeal epithelial (NP69) cells, as evaluated by flow cytometric analyses. Activity of Caspases 3/7 was detected in H2O2-treated cells. This activity was inhibited by Caspase inhibitor (CI). By nested inverse polymerase chain reaction (IPCR), we demonstrated that oxidative stress-induced apoptosis in HK1 and NP69 cells resulted in cleavages within the breakpoint cluster region (BCR) of the AF9 gene. The gene cleavage frequency detected in the H2O2-treated cells was found to be significantly higher than untreated control. We further found that treatment with CI, which indirectly inhibits CAD, significantly reduced the chromosomal breaks in H2O2-cotreated cells. Intriguingly, a few breakpoints were mapped within the AF9 region that was previously reported to translocate with the mixed lineage leukemia (MLL) gene in acute lymphoblastic leukemia (ALL) patient. In conclusion, our findings suggested that oxidative stress-induced apoptosis could be one of the mechanisms underlying the chromosomal rearrangements in NPC. CAD may play an important role in chromosomal cleavages mediated by oxidative stress-induced apoptosis. A potential model for oxidative stress-induced apoptosis mediating chromosomal rearrangements in NPC is proposed.
J M Freyssinet - One of the best experts on this subject based on the ideXlab platform.
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Apoptosis in vascular disease.
Thrombosis and haemostasis, 1999Co-Authors: J M Freyssinet, Florence Toti, Bénédicte Hugel, Gidon-jeangirard C, Corinne Kunzelmann, Dominique MeyerAbstract:Introduction: Apoptosis, the term introduced 27 years ago to characterize a particular form of cell death distinct from necrosis,1 is now considered a genetically-controlled and energy-dependent process of fundamental significance in the development and maintenance of homeostasis in multicellular organisms.2-4 For instance, in the nematode Caenorhabditis elegans, a model widely used for the study of programmed cell death, 131 of the 1,090 somatic cells generated during hermaphrodite development undergo this form of death.5 Embryologists have suspected cell death of being instrumental in the “sculpture” of parts of the body well before the initial definition of apoptosis. In fact, cell proliferation can no longer be dissociated from apoptosis and it is obvious that variety of disorders involve either an excess of cell death for those referred to as disorders of cell loss, or a defect of apoptosis for those resulting in cell accumulation. Substantial information has been gained from studies of the hierarchical control of lymphocyte survival.6 Apoptosis is accompanied by characteristic changes in cell morphology, among which shrinkage, membrane blebbing, and nucleus condensation are the most frequently evoked (Fig. 1). Budding and disintegration by fragmentation in multiple bodies is the ultimate stage of this death process.7 Alterations are induced by external signals as different as physical (radiation, mechanical stress), chemical (oxidants, xenobiotics) or biological (granzymes, receptor-mediated signals, ceramide), and also by survival factor deprivation. Interestingly, some of these signals can result from subnecrotic damage. In the so-called induction phase, each agent exerts its proapoptotic action through a “private” pathway, leading to the common pathways composed of the effector and degradation phases. The effector phase consists of a mitochondrial checkpoint involving the Bcl-2/Bax anti/proapoptotic balance, immediately after which cytochrome c is released from the injured mitochondrion and binds to adaptor proteins to activate the Caspase cascade. The degradation phase is achieved by reactive oxygen species (ROS) generated at the mitochondrial level, cytoplasmic changes (depletion of glutathione and variations of cytosolic calcium), and by Caspases. Caspases, also referred to as interleukin-1-converting enzyme (ICE)-like proteases, are a family of cysteine proteinases showing specificity for Asp residue and having various cytoplasmic or nuclear substrates, such as cytoskeletal proteins or proteins involved in DNA repair or control of endonucleases. The latter mechanism explains why DNA ladders, multiples of the 180 bp nucleosomal unit, constitute one of the hallmarks of apoptotic cells.8 Plasma membrane remodeling, resulting in the occurrence of phosphatidylserine (PS) in the exoplasmic leaflet and the shedding of membrane microparticles, are other hallmarks worth considering.9-12 The Caspase cascade can, alternatively, be directly Activated by granzyme B, which penetrates into the cytoplasm through perforin channels, or after Fas (CD95) or tumor necrosis factor (TNF) receptor 1 (TNFR1) ligation. The generation of Caspase-3 (CPP32) appears to be a pivotal step, since this enzyme mediates both the activation of CAD (Caspase-Activated Deoxyribonuclease) and PS externalization.8,13 A number of determinants, including PS, are expressed in apoptotic cells and derived fragments for their noninflammatory engulfment by phagocytes, whereas tissue necrosis is accompanied by proinflammatory events.9,11,14,15 Despite extensive investigations, major gaps still exist in trying to connect and define the relative contribution of the different components of this basic process, but recently, apoptotic features have been described in unicellular, primitive eukaryotes, such as yeast,16,17 which could be used as model organisms to expand our knowledge. Owing to the presence of the effector machinery for programmed cell death in virtually all nucleated cell types, it is obvious that mechanisms have evolved in parallel for a tight regulation of apoptosis, as detailed in most of the references quoted in this section.
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Apoptosis in Vascular Disease
Thrombosis and Haemostasis, 1999Co-Authors: Florence Toti, Bénédicte Hugel, Corinne Kunzelmann, Dominique Meyer, Carole Gidon-jeangirard, M. Carmen Martínez, J M FreyssinetAbstract:IntroductionApoptosis, the term introduced 27 years ago to characterize a particular form of cell death distinct from necrosis,1 is now considered a genetically-controlled and energy-dependent process of fundamental significance in the development and maintenance of homeostasis in multicellular organisms.2-4 For instance, in the nematode Caenorhabditis elegans, a model widely used for the study of programmed cell death, 131 of the 1,090 somatic cells generated during hermaphrodite development undergo this form of death.5 Embryologists have suspected cell death of being instrumental in the “sculpture” of parts of the body well before the initial definition of apoptosis. In fact, cell proliferation can no longer be dissociated from apoptosis and it is obvious that variety of disorders involve either an excess of cell death for those referred to as disorders of cell loss, or a defect of apoptosis for those resulting in cell accumulation. Substantial information has been gained from studies of the hierarchical control of lymphocyte survival.6 Apoptosis is accompanied by characteristic changes in cell morphology, among which shrinkage, membrane blebbing, and nucleus condensation are the most frequently evoked (Fig. 1). Budding and disintegration by fragmentation in multiple bodies is the ultimate stage of this death process.7 Alterations are induced by external signals as different as physical (radiation, mechanical stress), chemical (oxidants, xenobiotics) or biological (granzymes, receptor-mediated signals, ceramide), and also by survival factor deprivation. Interestingly, some of these signals can result from subnecrotic damage. In the so-called induction phase, each agent exerts its proapoptotic action through a “private” pathway, leading to the common pathways composed of the effector and degradation phases. The effector phase consists of a mitochondrial checkpoint involving the Bcl-2/Bax anti/proapoptotic balance, immediately after which cytochrome c is released from the injured mitochondrion and binds to adaptor proteins to activate the Caspase cascade. The degradation phase is achieved by reactive oxygen species (ROS) generated at the mitochondrial level, cytoplasmic changes (depletion of glutathione and variations of cytosolic calcium), and by Caspases.Caspases, also referred to as interleukin-1-converting enzyme (ICE)-like proteases, are a family of cysteine proteinases showing specificity for Asp residue and having various cytoplasmic or nuclear substrates, such as cytoskeletal proteins or proteins involved in DNA repair or control of endonucleases. The latter mechanism explains why DNA ladders, multiples of the 180 bp nucleosomal unit, constitute one of the hallmarks of apoptotic cells.8 Plasma membrane remodeling, resulting in the occurrence of phosphatidylserine (PS) in the exoplasmic leaflet and the shedding of membrane microparticles, are other hallmarks worth considering.9-12 The Caspase cascade can, alternatively, be directly Activated by granzyme B, which penetrates into the cytoplasm through perforin channels, or after Fas (CD95) or tumor necrosis factor (TNF) receptor 1 (TNFR1) ligation. The generation of Caspase-3 (CPP32) appears to be a pivotal step, since this enzyme mediates both the activation of CAD (Caspase-Activated Deoxyribonuclease) and PS externalization.8,13 A number of determinants, including PS, are expressed in apoptotic cells and derived fragments for their noninflammatory engulfment by phagocytes, whereas tissue necrosis is accompanied by proinflammatory events.9,11,14,15 Despite extensive investigations, major gaps still exist in trying to connect and define the relative contribution of the different components of this basic process, but recently, apoptotic features have been described in unicellular, primitive eukaryotes, such as yeast,16,17 which could be used as model organisms to expand our knowledge. Owing to the presence of the effector machinery for programmed cell death in virtually all nucleated cell types, it is obvious that mechanisms have evolved in parallel for a tight regulation of apoptosis, as detailed in most of the references quoted in this section.In such an active context, the impact of apoptosis has not escaped the attention of cardiovascular biologists. Recent reviews emphasize the role of programmed cell death in cardiac development, heart failure and ischemic heart disease,18-21 and in vascular disease. Of these, a majority deal with atherosclerosis and concern endothelial or smooth muscle cells and leukocytes.22-25 To avoid redundancy, then, the purpose of the present state-of-the-art review is to focus on aspects related to plasma membrane modifications contributing to the acquisition of hemorrhagic or thrombogenic phenotypes or to the development of (auto)immune response, in vitro and in vivo, in the vascular compartment.