The Experts below are selected from a list of 270 Experts worldwide ranked by ideXlab platform
Zigang Dong - One of the best experts on this subject based on the ideXlab platform.
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polycomb pcg proteins bmi1 and suz12 regulate arsenic induced Cell Transformation
Journal of Biological Chemistry, 2012Co-Authors: Shengqing Li, Ann M. Bode, Xiang Li, Zigang DongAbstract:Abstract Inorganic arsenic is a well-documented human carcinogen associated with cancers of the skin, lung, liver, and bladder. However, the underlying mechanisms explaining the tumorigenic role of arsenic are not well understood. The present study explored a potential mechanism of Cell Transformation induced by arsenic exposure. Exposure to a low dose (0.5 μm) of arsenic trioxide (As2O3) caused Transformation of BALB/c 3T3 Cells. In addition, in a xenograft mouse model, tumor growth of the arsenic-induced transformed Cells was dramatically increased. In arsenic-induced transformed Cells, polycomb group (PcG) proteins, including BMI1 and SUZ12, were activated resulting in enhanced histone H3K27 tri-methylation levels. On the other hand, tumor suppressor p16INK4a and p19ARF mRNA and protein expression were dramatically suppressed. Introduction of small hairpin (sh) RNA-BMI1 or -SUZ12 into BALB/c 3T3 Cells resulted in suppression of arsenic-induced Transformation. Histone H3K27 tri-methylation returned to normal in BMI1- or SUZ12-knockdown BALB/c 3T3 Cells compared with BMI1- or SUZ12-wildtype Cells after arsenic exposure. As a consequence, the expression of p16INK4a and p19ARF was recovered in arsenic-treated BMI1- or SUZ12-knockdown Cells. Thus, arsenic-induced Cell Transformation was blocked by inhibition of PcG function. Taken together, these results strongly suggest that the polycomb proteins, BMI1 and SUZ12 are required for Cell Transformation induced by organic arsenic exposure.
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Mitogen- and stress-activated kinase 1 (MSK1) is required for neoplastic Cell Transformation
Cancer Research, 2008Co-Authors: Hong-gyum Kim, Yong Yeon Cho, Ann M. Bode, Ki Won Lee, Zigang DongAbstract:3473 Mitogen- and stress-activated kinase 1 (MSK1) is a nuclear kinase that acts downstream of both ERK and p38 mitogen-activated protein (MAP) kinases and is activated in response to stress or mitogenic extraCellular stimuli. However, the physiological role of MSK1 in malignant Transformation and cancer development is not clear . Here, we report that MSK1 is involved in 12-O-tetradecanoylphorbol-13-acetate (TPA)- or epidermal growth factor (EGF)-induced Cell Transformation of JB6 Cl41 Cells. H89, a potent inhibitor of MSK1, strongly suppressed TPA- or EGF-induced Cell Transformation. When Cells overexpressing wildtype MSK1 were treated with TPA or EGF, colony formation increased markedly compared to untreated Cells or Cells that did not overexpress MSK1. In contrast, MSK1 C-terminal or N-terminal dead dominant negative mutants dramatically suppressed Cell Transformation. Introduction of small interfering (si) RNA-MSK1 into JB6 Cl41 Cells resulted in suppressed TPA- or EGF-induced Cell Transformation. In addition, Cell proliferation was inhibited in MSK1 knockdown Cells compared to MSK1 wildtype Cells. In wildtype MSK1-overexpressing Cells, AP-1 activation increased after TPA or EGF stimulation, whereas AP-1 activation decreased in both MSK1 dominant-negative mutants and MSK1 knockdown Cells. Moreover, TPA- or EGF-induced phosphorylation of histone H3 at Ser10 was increased in wildtype Cells but the induced phosphorylation was abolished in MSK1 dominant-negative mutant or MSK1 knockdown Cells. Histone H3 mutant (S10A) Cells also inhibited EGF- or TPA-induced colony Transformation. Thus, MSK1 is required for tumor promoter-induced Cell Transformation through its phosphorylation of histone H3 at Ser10 and AP-1 activation.
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Ribosomal S6 Kinase 2 Is a Key Regulator in Tumor Promoter–Induced Cell Transformation
Cancer research, 2007Co-Authors: Yong Yeon Cho, Ann M. Bode, Ke Yao, Bong Seok Kang, Hong-gyum Kim, Duo Zheng, Zigang DongAbstract:The ribosomal S6 kinase 2 (RSK2), a member of the p90RSK (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extraCellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances Cell survival. However, the roles of RSK2 in Cell Transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of Cell Transformation. When Cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2−/− mouse embryonic fibroblasts (MEFs) compared with RSK2+/+ MEFs. Moreover, RSK2−/− MEFs accumulated at the G1 phase of the Cell cycle under normal Cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent Cell Transformation assay (soft agar), stable expression of RSK2 in JB6 Cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (RasG12V)-induced foci formation in NIH3T3 Cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 Cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser10). These results showed that RSK2 is a key regulator for Cell Transformation induced by tumor promoters such as EGF and TPA. [Cancer Res 2007;67(17):8104–12]
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ribosomal s6 kinase 2 is a key regulator in tumor promoter induced Cell Transformation
Cancer Research, 2007Co-Authors: Yong Yeon Cho, Ann M. Bode, Ke Yao, Bong Seok Kang, Hong-gyum Kim, Duo Zheng, Zigang DongAbstract:The ribosomal S6 kinase 2 (RSK2), a member of the p90RSK (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extraCellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances Cell survival. However, the roles of RSK2 in Cell Transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of Cell Transformation. When Cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2−/− mouse embryonic fibroblasts (MEFs) compared with RSK2+/+ MEFs. Moreover, RSK2−/− MEFs accumulated at the G1 phase of the Cell cycle under normal Cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent Cell Transformation assay (soft agar), stable expression of RSK2 in JB6 Cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (RasG12V)-induced foci formation in NIH3T3 Cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 Cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser10). These results showed that RSK2 is a key regulator for Cell Transformation induced by tumor promoters such as EGF and TPA. [Cancer Res 2007;67(17):8104–12]
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Involvement of the Paxillin Pathway in JB6 Cl41 Cell Transformation
Cancer research, 2006Co-Authors: Yasuaki Tatsumi, Yong Yeon Cho, Hideya Mizuno, Hong Seok Choi, Ann M. Bode, Zigang DongAbstract:Paxillin is a substrate of the Src tyrosine onco-kinase and is involved in Cell Transformation, Cell spreading, migration, and cancer development mediated through the mitogen-activated protein kinase signaling cascades. Here, we showed that paxillin plays a key role in skin Cell Transformation induced by epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA). To investigate the mechanism of paxillin9s role in Cell Transformation, we established a paxillin knockdown stably transfected Cell line by introducing small interfering RNA-paxillin (si-paxillin). The si-paxillin Cells displayed a dramatic suppression of Cell proliferation and anchorage-independent Cell Transformation induced by EGF or TPA compared with si-mock control Cells. In si-paxillin Cells, decreased activator protein-1 (AP-1)–dependent luciferase activity corresponded with suppressed AP-1 DNA binding activity. Importantly, knockdown of paxillin inhibited EGF- or TPA-induced c-Jun phosphorylation at Ser 63 and Ser 73 . Furthermore, total c-Jun protein level was dramatically decreased in si-paxillin Cells and was dependent on serum deprivation time. The down-regulation of c-Jun was restored in si-paxillin Cells by treatment with the proteasome inhibitor lactacystin but not by the lysosome inhibitor leupeptin. These results clearly provided evidence that paxillin regulates c-Jun protein level and plays a key role in Cell Transformation most likely through the regulation of c-Jun stability. (Cancer Res 2006; 66(11): 5968-74)
Yong Yeon Cho - One of the best experts on this subject based on the ideXlab platform.
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abstract 39 fibroblast growth factor induces neoplastic Cell Transformation through a non canonical signaling pathway
Cancer Research, 2015Co-Authors: Sunmi Yoo, Meehyun Lee, Cheoljung Lee, Yong Yeon ChoAbstract:Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Induction of Cell proliferation is closely related with the Cellular signaling pathway activation by stimulation of diverse growth factors such as epidermal growth factor (EGF) and fibroblast growth factor. The stimulation of growth factors induces activation of extraCellular signal-regulated kinases (ERKs)/p90 ribosomal S6 kinases (p90RSK), resulting in induction of Cell proliferation and Cell Transformation. Although fibroblast growth factor (FGF) is a well-known growth factor and acts as a ligand of FGF receptor (FGFR), a receptor tyrosine kinase, in cytoplasmic membrane, the tumor promoter potential has not been clearly understood. Here, we provided the evidences that FGF acted as a tumor promoter. We found that FGF-induced Cell proliferation and anchorage-independent Cell Transformation were correlated with the induction of G1/S Cell cycle transition. Importantly, we found that kaempferol targeted and inhibited FGFR phosphorylation by in vitro and ex vivo. Interestingly, FGF stimulation utilized a non-canonical signaling pathway to activate RSK2 and ATF-1, which was not transduced by EGF stimulation. We confirmed that kaempferol inhibited tyrosine phosphorylation of FGFR, resulted in nuclear accumulation of phospho-ATF-1 at Ser63. Importantly, kaempferol, PKC412, PD98059 and U0126 inhibited EGF-induced anchorage-independent Cell Transformation in JB6 Cl41 Cells. In contrast, FGF-induced Cell Transformation in soft agar was not inhibited by PD98059 and U0126. Taken together, these results demonstrate that FGF acts as a tumor promoter and dual inhibition of kaempferol on the kinase activities of FGFR and RSK2 suppresses the FGF-induced neoplastic Cell Transformation through a non-canonical signaling pathway which is not utilized by EGF stimulation. Citation Format: Sun-Mi Yoo, Cheol-Jung Lee, Mee-Hyun Lee, Yong-Yeon Cho. Fibroblast growth factor induces neoplastic Cell Transformation through a non-canonical signaling pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 39. doi:10.1158/1538-7445.AM2015-39
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Phosphorylation of Histone H2B Serine 32 Is Linked to Cell Transformation
The Journal of biological chemistry, 2011Co-Authors: Andy T Y Lau, Yong Yeon Cho, Hong-gyum Kim, Duo Zheng, Sung Young Lee, Feng Zhu, Zhiguo Zhang, Ann M. BodeAbstract:Various types of post-translational modifications of the histone tails have been revealed, but a few modifications have been found within the histone core sequences. Histone core post-translational modifications have the potential to modulate nucleosome structure and DNA accessibility. Here, we studied the histone H2B core domain and found that phosphorylation of H2B serine 32 occurs in normal cycling and mitogen-stimulated Cells. Notably, this phosphorylation is elevated in skin cancer Cell lines and tissues compared with normal counterparts. The JB6 Cl41 mouse skin epidermal Cell line is a well established model for tumor promoter-induced Cell Transformation and was used to study the function of H2B during EGF-induced carcinogenesis. Remarkably, Cells overexpressing a nonphosphorylatable H2BS32A mutant exhibited suppressed growth and EGF-induced Cell Transformation, possibly because of decreased activation of activator protein-1, compared with control Cells overexpressing wild type H2B. We identified ribosomal S6 kinase 2 (RSK2) as the kinase responsible for H2BS32 phosphorylation. Serum-starved JB6 Cells contain very little endogenous H2BS32 phosphorylation, and EGF treatment induced this phosphorylation. The phosphorylation was attenuated in RSK2 knock-out MEFs and RSK2 knockdown JB6 Cells. Taken together, our results demonstrate a novel role for H2B phosphorylation in Cell Transformation and show that H2BS32 phosphorylation is critical for controlling activator protein-1 activity, which is a major driver in Cell Transformation.
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Mitogen- and stress-activated kinase 1 (MSK1) is required for neoplastic Cell Transformation
Cancer Research, 2008Co-Authors: Hong-gyum Kim, Yong Yeon Cho, Ann M. Bode, Ki Won Lee, Zigang DongAbstract:3473 Mitogen- and stress-activated kinase 1 (MSK1) is a nuclear kinase that acts downstream of both ERK and p38 mitogen-activated protein (MAP) kinases and is activated in response to stress or mitogenic extraCellular stimuli. However, the physiological role of MSK1 in malignant Transformation and cancer development is not clear . Here, we report that MSK1 is involved in 12-O-tetradecanoylphorbol-13-acetate (TPA)- or epidermal growth factor (EGF)-induced Cell Transformation of JB6 Cl41 Cells. H89, a potent inhibitor of MSK1, strongly suppressed TPA- or EGF-induced Cell Transformation. When Cells overexpressing wildtype MSK1 were treated with TPA or EGF, colony formation increased markedly compared to untreated Cells or Cells that did not overexpress MSK1. In contrast, MSK1 C-terminal or N-terminal dead dominant negative mutants dramatically suppressed Cell Transformation. Introduction of small interfering (si) RNA-MSK1 into JB6 Cl41 Cells resulted in suppressed TPA- or EGF-induced Cell Transformation. In addition, Cell proliferation was inhibited in MSK1 knockdown Cells compared to MSK1 wildtype Cells. In wildtype MSK1-overexpressing Cells, AP-1 activation increased after TPA or EGF stimulation, whereas AP-1 activation decreased in both MSK1 dominant-negative mutants and MSK1 knockdown Cells. Moreover, TPA- or EGF-induced phosphorylation of histone H3 at Ser10 was increased in wildtype Cells but the induced phosphorylation was abolished in MSK1 dominant-negative mutant or MSK1 knockdown Cells. Histone H3 mutant (S10A) Cells also inhibited EGF- or TPA-induced colony Transformation. Thus, MSK1 is required for tumor promoter-induced Cell Transformation through its phosphorylation of histone H3 at Ser10 and AP-1 activation.
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Fyn is a novel target of (-)-epigallocatechin gallate in the inhibition of JB6 Cl41 Cell Transformation.
Molecular carcinogenesis, 2008Co-Authors: Faqing Tang, Yong Yeon Cho, Hong Seok Choi, Ann M. Bode, Svetlana P. Ermakova, Qing Zhao, Chung S. YangAbstract:The cancer preventive action of (-)-epigallocatechin gallate (EGCG), found in green tea, is strongly supported by epidemiology and laboratory research data. However, the mechanism by which EGCG inhibits carcinogenesis and Cell Transformation is not clear. In this study, we report that EGCG suppressed epidermal growth factor (EGF)-induced Cell Transformation in JB6 Cells. We also found that EGCG inhibited EGF-induced Fyn kinase activity and phosphorylation in vitro and in vivo. Fyn was implicated in the process because EGF-induced JB6 Cell Transformation was inhibited by small interfering RNA (siRNA)-Fyn-JB6 Cells. With an in vitro protein-binding assay, we found that EGCG directly bound with the GST-Fyn-SH2 domain but not the GST-Fyn-SH3 domain. The K(d) value for EGCG binding to the Fyn SH2 domain was 0.367 +/- 0.122 microM and B(max) was 1.35 +/- 0.128 nmol/mg. Compared with control JB6 Cl41 Cells, EGF-induced phosphorylation of p38 MAP kinase (p38 MAPK) (Thr180/Tyr182), ATF-2 (Thr71) and signal transducer and activator of transcription 1 (STAT1) (Thr727) was decreased in siRNA-Fyn-JB6 Cells. EGCG could inhibit the phosphorylation of p38 MAPK, ATF-2, and STAT1. The DNA binding ability of AP-1, STAT1, and ATF-2 was also decreased in siRNA-Fyn-JB6 Cells. Overall, these results demonstrated that EGCG interacted with Fyn and inhibited Fyn kinase activity and thereby regulated EGF-induced Cell Transformation. Inhibition of Fyn kinase activity is a novel and important mechanism that may be involved in EGCG-induced inhibition of Cell Transformation.
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Ribosomal S6 Kinase 2 Is a Key Regulator in Tumor Promoter–Induced Cell Transformation
Cancer research, 2007Co-Authors: Yong Yeon Cho, Ann M. Bode, Ke Yao, Bong Seok Kang, Hong-gyum Kim, Duo Zheng, Zigang DongAbstract:The ribosomal S6 kinase 2 (RSK2), a member of the p90RSK (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extraCellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances Cell survival. However, the roles of RSK2 in Cell Transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of Cell Transformation. When Cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2−/− mouse embryonic fibroblasts (MEFs) compared with RSK2+/+ MEFs. Moreover, RSK2−/− MEFs accumulated at the G1 phase of the Cell cycle under normal Cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent Cell Transformation assay (soft agar), stable expression of RSK2 in JB6 Cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (RasG12V)-induced foci formation in NIH3T3 Cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 Cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser10). These results showed that RSK2 is a key regulator for Cell Transformation induced by tumor promoters such as EGF and TPA. [Cancer Res 2007;67(17):8104–12]
Ann M. Bode - One of the best experts on this subject based on the ideXlab platform.
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polycomb pcg proteins bmi1 and suz12 regulate arsenic induced Cell Transformation
Journal of Biological Chemistry, 2012Co-Authors: Shengqing Li, Ann M. Bode, Xiang Li, Zigang DongAbstract:Abstract Inorganic arsenic is a well-documented human carcinogen associated with cancers of the skin, lung, liver, and bladder. However, the underlying mechanisms explaining the tumorigenic role of arsenic are not well understood. The present study explored a potential mechanism of Cell Transformation induced by arsenic exposure. Exposure to a low dose (0.5 μm) of arsenic trioxide (As2O3) caused Transformation of BALB/c 3T3 Cells. In addition, in a xenograft mouse model, tumor growth of the arsenic-induced transformed Cells was dramatically increased. In arsenic-induced transformed Cells, polycomb group (PcG) proteins, including BMI1 and SUZ12, were activated resulting in enhanced histone H3K27 tri-methylation levels. On the other hand, tumor suppressor p16INK4a and p19ARF mRNA and protein expression were dramatically suppressed. Introduction of small hairpin (sh) RNA-BMI1 or -SUZ12 into BALB/c 3T3 Cells resulted in suppression of arsenic-induced Transformation. Histone H3K27 tri-methylation returned to normal in BMI1- or SUZ12-knockdown BALB/c 3T3 Cells compared with BMI1- or SUZ12-wildtype Cells after arsenic exposure. As a consequence, the expression of p16INK4a and p19ARF was recovered in arsenic-treated BMI1- or SUZ12-knockdown Cells. Thus, arsenic-induced Cell Transformation was blocked by inhibition of PcG function. Taken together, these results strongly suggest that the polycomb proteins, BMI1 and SUZ12 are required for Cell Transformation induced by organic arsenic exposure.
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Phosphorylation of Histone H2B Serine 32 Is Linked to Cell Transformation
The Journal of biological chemistry, 2011Co-Authors: Andy T Y Lau, Yong Yeon Cho, Hong-gyum Kim, Duo Zheng, Sung Young Lee, Feng Zhu, Zhiguo Zhang, Ann M. BodeAbstract:Various types of post-translational modifications of the histone tails have been revealed, but a few modifications have been found within the histone core sequences. Histone core post-translational modifications have the potential to modulate nucleosome structure and DNA accessibility. Here, we studied the histone H2B core domain and found that phosphorylation of H2B serine 32 occurs in normal cycling and mitogen-stimulated Cells. Notably, this phosphorylation is elevated in skin cancer Cell lines and tissues compared with normal counterparts. The JB6 Cl41 mouse skin epidermal Cell line is a well established model for tumor promoter-induced Cell Transformation and was used to study the function of H2B during EGF-induced carcinogenesis. Remarkably, Cells overexpressing a nonphosphorylatable H2BS32A mutant exhibited suppressed growth and EGF-induced Cell Transformation, possibly because of decreased activation of activator protein-1, compared with control Cells overexpressing wild type H2B. We identified ribosomal S6 kinase 2 (RSK2) as the kinase responsible for H2BS32 phosphorylation. Serum-starved JB6 Cells contain very little endogenous H2BS32 phosphorylation, and EGF treatment induced this phosphorylation. The phosphorylation was attenuated in RSK2 knock-out MEFs and RSK2 knockdown JB6 Cells. Taken together, our results demonstrate a novel role for H2B phosphorylation in Cell Transformation and show that H2BS32 phosphorylation is critical for controlling activator protein-1 activity, which is a major driver in Cell Transformation.
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Mitogen- and stress-activated kinase 1 (MSK1) is required for neoplastic Cell Transformation
Cancer Research, 2008Co-Authors: Hong-gyum Kim, Yong Yeon Cho, Ann M. Bode, Ki Won Lee, Zigang DongAbstract:3473 Mitogen- and stress-activated kinase 1 (MSK1) is a nuclear kinase that acts downstream of both ERK and p38 mitogen-activated protein (MAP) kinases and is activated in response to stress or mitogenic extraCellular stimuli. However, the physiological role of MSK1 in malignant Transformation and cancer development is not clear . Here, we report that MSK1 is involved in 12-O-tetradecanoylphorbol-13-acetate (TPA)- or epidermal growth factor (EGF)-induced Cell Transformation of JB6 Cl41 Cells. H89, a potent inhibitor of MSK1, strongly suppressed TPA- or EGF-induced Cell Transformation. When Cells overexpressing wildtype MSK1 were treated with TPA or EGF, colony formation increased markedly compared to untreated Cells or Cells that did not overexpress MSK1. In contrast, MSK1 C-terminal or N-terminal dead dominant negative mutants dramatically suppressed Cell Transformation. Introduction of small interfering (si) RNA-MSK1 into JB6 Cl41 Cells resulted in suppressed TPA- or EGF-induced Cell Transformation. In addition, Cell proliferation was inhibited in MSK1 knockdown Cells compared to MSK1 wildtype Cells. In wildtype MSK1-overexpressing Cells, AP-1 activation increased after TPA or EGF stimulation, whereas AP-1 activation decreased in both MSK1 dominant-negative mutants and MSK1 knockdown Cells. Moreover, TPA- or EGF-induced phosphorylation of histone H3 at Ser10 was increased in wildtype Cells but the induced phosphorylation was abolished in MSK1 dominant-negative mutant or MSK1 knockdown Cells. Histone H3 mutant (S10A) Cells also inhibited EGF- or TPA-induced colony Transformation. Thus, MSK1 is required for tumor promoter-induced Cell Transformation through its phosphorylation of histone H3 at Ser10 and AP-1 activation.
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Fyn is a novel target of (-)-epigallocatechin gallate in the inhibition of JB6 Cl41 Cell Transformation.
Molecular carcinogenesis, 2008Co-Authors: Faqing Tang, Yong Yeon Cho, Hong Seok Choi, Ann M. Bode, Svetlana P. Ermakova, Qing Zhao, Chung S. YangAbstract:The cancer preventive action of (-)-epigallocatechin gallate (EGCG), found in green tea, is strongly supported by epidemiology and laboratory research data. However, the mechanism by which EGCG inhibits carcinogenesis and Cell Transformation is not clear. In this study, we report that EGCG suppressed epidermal growth factor (EGF)-induced Cell Transformation in JB6 Cells. We also found that EGCG inhibited EGF-induced Fyn kinase activity and phosphorylation in vitro and in vivo. Fyn was implicated in the process because EGF-induced JB6 Cell Transformation was inhibited by small interfering RNA (siRNA)-Fyn-JB6 Cells. With an in vitro protein-binding assay, we found that EGCG directly bound with the GST-Fyn-SH2 domain but not the GST-Fyn-SH3 domain. The K(d) value for EGCG binding to the Fyn SH2 domain was 0.367 +/- 0.122 microM and B(max) was 1.35 +/- 0.128 nmol/mg. Compared with control JB6 Cl41 Cells, EGF-induced phosphorylation of p38 MAP kinase (p38 MAPK) (Thr180/Tyr182), ATF-2 (Thr71) and signal transducer and activator of transcription 1 (STAT1) (Thr727) was decreased in siRNA-Fyn-JB6 Cells. EGCG could inhibit the phosphorylation of p38 MAPK, ATF-2, and STAT1. The DNA binding ability of AP-1, STAT1, and ATF-2 was also decreased in siRNA-Fyn-JB6 Cells. Overall, these results demonstrated that EGCG interacted with Fyn and inhibited Fyn kinase activity and thereby regulated EGF-induced Cell Transformation. Inhibition of Fyn kinase activity is a novel and important mechanism that may be involved in EGCG-induced inhibition of Cell Transformation.
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Ribosomal S6 Kinase 2 Is a Key Regulator in Tumor Promoter–Induced Cell Transformation
Cancer research, 2007Co-Authors: Yong Yeon Cho, Ann M. Bode, Ke Yao, Bong Seok Kang, Hong-gyum Kim, Duo Zheng, Zigang DongAbstract:The ribosomal S6 kinase 2 (RSK2), a member of the p90RSK (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extraCellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances Cell survival. However, the roles of RSK2 in Cell Transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of Cell Transformation. When Cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2−/− mouse embryonic fibroblasts (MEFs) compared with RSK2+/+ MEFs. Moreover, RSK2−/− MEFs accumulated at the G1 phase of the Cell cycle under normal Cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent Cell Transformation assay (soft agar), stable expression of RSK2 in JB6 Cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (RasG12V)-induced foci formation in NIH3T3 Cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 Cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser10). These results showed that RSK2 is a key regulator for Cell Transformation induced by tumor promoters such as EGF and TPA. [Cancer Res 2007;67(17):8104–12]
Hong-gyum Kim - One of the best experts on this subject based on the ideXlab platform.
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Phosphorylation of Histone H2B Serine 32 Is Linked to Cell Transformation
The Journal of biological chemistry, 2011Co-Authors: Andy T Y Lau, Yong Yeon Cho, Hong-gyum Kim, Duo Zheng, Sung Young Lee, Feng Zhu, Zhiguo Zhang, Ann M. BodeAbstract:Various types of post-translational modifications of the histone tails have been revealed, but a few modifications have been found within the histone core sequences. Histone core post-translational modifications have the potential to modulate nucleosome structure and DNA accessibility. Here, we studied the histone H2B core domain and found that phosphorylation of H2B serine 32 occurs in normal cycling and mitogen-stimulated Cells. Notably, this phosphorylation is elevated in skin cancer Cell lines and tissues compared with normal counterparts. The JB6 Cl41 mouse skin epidermal Cell line is a well established model for tumor promoter-induced Cell Transformation and was used to study the function of H2B during EGF-induced carcinogenesis. Remarkably, Cells overexpressing a nonphosphorylatable H2BS32A mutant exhibited suppressed growth and EGF-induced Cell Transformation, possibly because of decreased activation of activator protein-1, compared with control Cells overexpressing wild type H2B. We identified ribosomal S6 kinase 2 (RSK2) as the kinase responsible for H2BS32 phosphorylation. Serum-starved JB6 Cells contain very little endogenous H2BS32 phosphorylation, and EGF treatment induced this phosphorylation. The phosphorylation was attenuated in RSK2 knock-out MEFs and RSK2 knockdown JB6 Cells. Taken together, our results demonstrate a novel role for H2B phosphorylation in Cell Transformation and show that H2BS32 phosphorylation is critical for controlling activator protein-1 activity, which is a major driver in Cell Transformation.
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Mitogen- and stress-activated kinase 1 (MSK1) is required for neoplastic Cell Transformation
Cancer Research, 2008Co-Authors: Hong-gyum Kim, Yong Yeon Cho, Ann M. Bode, Ki Won Lee, Zigang DongAbstract:3473 Mitogen- and stress-activated kinase 1 (MSK1) is a nuclear kinase that acts downstream of both ERK and p38 mitogen-activated protein (MAP) kinases and is activated in response to stress or mitogenic extraCellular stimuli. However, the physiological role of MSK1 in malignant Transformation and cancer development is not clear . Here, we report that MSK1 is involved in 12-O-tetradecanoylphorbol-13-acetate (TPA)- or epidermal growth factor (EGF)-induced Cell Transformation of JB6 Cl41 Cells. H89, a potent inhibitor of MSK1, strongly suppressed TPA- or EGF-induced Cell Transformation. When Cells overexpressing wildtype MSK1 were treated with TPA or EGF, colony formation increased markedly compared to untreated Cells or Cells that did not overexpress MSK1. In contrast, MSK1 C-terminal or N-terminal dead dominant negative mutants dramatically suppressed Cell Transformation. Introduction of small interfering (si) RNA-MSK1 into JB6 Cl41 Cells resulted in suppressed TPA- or EGF-induced Cell Transformation. In addition, Cell proliferation was inhibited in MSK1 knockdown Cells compared to MSK1 wildtype Cells. In wildtype MSK1-overexpressing Cells, AP-1 activation increased after TPA or EGF stimulation, whereas AP-1 activation decreased in both MSK1 dominant-negative mutants and MSK1 knockdown Cells. Moreover, TPA- or EGF-induced phosphorylation of histone H3 at Ser10 was increased in wildtype Cells but the induced phosphorylation was abolished in MSK1 dominant-negative mutant or MSK1 knockdown Cells. Histone H3 mutant (S10A) Cells also inhibited EGF- or TPA-induced colony Transformation. Thus, MSK1 is required for tumor promoter-induced Cell Transformation through its phosphorylation of histone H3 at Ser10 and AP-1 activation.
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Ribosomal S6 Kinase 2 Is a Key Regulator in Tumor Promoter–Induced Cell Transformation
Cancer research, 2007Co-Authors: Yong Yeon Cho, Ann M. Bode, Ke Yao, Bong Seok Kang, Hong-gyum Kim, Duo Zheng, Zigang DongAbstract:The ribosomal S6 kinase 2 (RSK2), a member of the p90RSK (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extraCellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances Cell survival. However, the roles of RSK2 in Cell Transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of Cell Transformation. When Cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2−/− mouse embryonic fibroblasts (MEFs) compared with RSK2+/+ MEFs. Moreover, RSK2−/− MEFs accumulated at the G1 phase of the Cell cycle under normal Cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent Cell Transformation assay (soft agar), stable expression of RSK2 in JB6 Cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (RasG12V)-induced foci formation in NIH3T3 Cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 Cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser10). These results showed that RSK2 is a key regulator for Cell Transformation induced by tumor promoters such as EGF and TPA. [Cancer Res 2007;67(17):8104–12]
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ribosomal s6 kinase 2 is a key regulator in tumor promoter induced Cell Transformation
Cancer Research, 2007Co-Authors: Yong Yeon Cho, Ann M. Bode, Ke Yao, Bong Seok Kang, Hong-gyum Kim, Duo Zheng, Zigang DongAbstract:The ribosomal S6 kinase 2 (RSK2), a member of the p90RSK (RSK) family of proteins, is a widely expressed serine/threonine kinase that is activated by extraCellular signal-regulated kinase 1/2 and phosphoinositide-dependent kinase 1 in response to many growth factors and peptide hormones. Its activation signaling enhances Cell survival. However, the roles of RSK2 in Cell Transformation have not yet been elucidated. Here, we found that RSK2 is a critical serine/threonine kinase for the regulation of Cell Transformation. When Cells were stimulated with tumor promoters, such as epidermal growth factor (EGF) or 12- O -tetradecanoylphorbol-13-acetate (TPA), phosphorylation of RSK was increased within 5 min. Cell proliferation was suppressed in RSK2−/− mouse embryonic fibroblasts (MEFs) compared with RSK2+/+ MEFs. Moreover, RSK2−/− MEFs accumulated at the G1 phase of the Cell cycle under normal Cell culture conditions as well as after stimulation with EGF or TPA. In the anchorage-independent Cell Transformation assay (soft agar), stable expression of RSK2 in JB6 Cells significantly enhanced colony formation in either the presence or absence of tumor promoters. Furthermore, knockdown of RSK2 with small interfering RNA-RSK2 suppressed constitutively active Ras (RasG12V)-induced foci formation in NIH3T3 Cells. In addition, kaempferol, an inhibitor of RSK2, suppressed EGF-induced colony formation of JB6 Cl41 Cells in soft agar, which was associated with inhibition of histone H3 phosphorylation (Ser10). These results showed that RSK2 is a key regulator for Cell Transformation induced by tumor promoters such as EGF and TPA. [Cancer Res 2007;67(17):8104–12]
Robert J. Isfort - One of the best experts on this subject based on the ideXlab platform.
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Mechanisms of Cell Transformation in the Syrian hamster embryo (SHE) Cell Transformation system.
Annals of the New York Academy of Sciences, 2006Co-Authors: Robert J. IsfortAbstract:The Syrian hamster embryo (SHE) Cell Transformation system has been used for investigational studies of basic mechanisms of neoplastic Transformation, as well as determining the carcinogenic potential of chemical, physical, and biological agents. Many of these investigations utilize an intermediate step in the SHE Cell neoplastic Transformation process, known as morphological Transformation, as an indicator that the Cells have acquired an increased potential to progress to malignancy. While the nature of the morphologically transformed phenotype is not completely understood, it is believed to result from a block in the Cellular differentiation of stem Cells present within the SHE Cell population. In terms of determination of the transforming potential of biological/chemical/physical agents, more than 500 agents have been tested in the SHE Cell Transformation assay with an 80-90% correlation between MT and carcinogenic potential. As such, the SHE Cell Transformation assay has utility as a test to provide short-term information on the carcinogenic potential of chemicals. One class of agents of current interest with regard to SHE Cell Transformation assay utilization consists of growth and differentiation factors (GDFs). Analysis of the SHE Cell Transformation potential of the GDFs, epidermal growth factor (EGF), fibroblast growth factor 4 (FGF-4), platelet-derived growth factor AA (PDGF AA), PDGF AB, PDGF BB, and the antimitogenic GDF, transforming growth factor beta one (TGF-beta1), was performed. All GDFs, with the exception of TGF-beta1, induced SHE Cell Transformation. However, an interesting difference between the GDFs was observed--PDGF A/B and PDGF B/B, but not PDGF A/A, EGF, or FGF-4, induced Transformation after both a transient 1-day exposure and a continuous 7-day exposure, while continuous 7-day exposure was required for Transformation by PDGF A/A, EGF, and FGF-4. Interestingly, both transient 1-day and continuous 7-day TGF-beta1 exposure resulted in suppression of Transformation induced by a variety of transforming agents including growth factors, Ames assay-positive carcinogens, Ames assay-negative carcinogens, and spontaneous Transformation. Interestingly TGF-beta1 was not able to suppress Transformation by the tumor promoter, TPA. Together, these data demonstrate the utility of the Syrian hamster embryo Cell Transformation system for analyzing the transforming potential of GDFs and for characterizing differences in transforming mechanisms between different GDFs.
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The pH 6.7 Syrian hamster embryo Cell Transformation assay for assessing the carcinogenic potential of chemicals
Mutation research, 1996Co-Authors: Robert A. Leboeuf, Gary A. Kerckaert, David P. Gibson, Marilyn J. Aardema, R Brauninger, Robert J. IsfortAbstract:Cell Transformation models have been established for studying the Cellular and molecular basis of the neoplastic process. Transformation models have also been utilized extensively for studying mechanisms of chemical carcinogenesis and, to a lesser degree, screening chemicals for their carcinogenic potential. Complexities associated with the conduct of Cell Transformation assays have been a significant factor in discouraging broad use of this approach despite their reported good predictivity for carcinogenicity. We previously reported that many of the experimental difficulties with the Syrian hamster embryo (SHE) Cell Transformation assay could be reduced or eliminated by culturing these Cells at pH 6.7 culture conditions compared to the historically used pH 7.1-7.3. We and others have shown that morphological Transformation (MT), the earliest recognizable phenotype in the multi-step Transformation process and the endpoint used in the standard assay to indicate a chemical's transforming activity, represents a pre-neoplastic stage in this model system. In the collaborative study reported here, in which approx. 50% of the chemicals were tested under code in one laboratory (Hazelton) and the other 50% evaluated by several investigators in the second laboratory (P & G), we have evaluated 56 chemicals (30 carcinogens, 18 non-carcinogens, 8 of inconclusive carcinogenic activity) in the SHE Cell Transformation assay conducted at pH 6.7 culture conditions with a standardized, Good Laboratory Practices-quality protocol. An overall concordance of 85% (41/48) between SHE Cell Transformation and rodent bioassay results was observed with assay sensitivity of 87% (26/30) and specificity of 83% (15/18), respectively. The assay exhibited a sensitivity of 78% (14/18) for Salmonella assay negative carcinogens, supporting its value for detecting non-mutagenic carcinogens. For maximum assay sensitivity, two exposure durations were required, namely a 24-h exposure and a 7-day exposure assay. Depending on the duration of chemical treatment required to induce Transformation, insight into the mechanism of Transformation induction may also be gained. Based on the data reported here, as well as the larger historical dataset reviewed by Isfort et al. (1996), we conclude that the SHE Cell Transformation assay provides an improved method for screening chemicals for carcinogenicity relative to current standard genotoxicity assays.
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Application of in vitro Cell Transformation assays to predict the carcinogenic potential of chemicals.
Mutation research, 1996Co-Authors: Robert J. Isfort, Robert A. LeboeufAbstract:Abstract Genotoxicity test batteries have become a standard tool for identifying chemicals that may have potential carcinogenic risk to humans. It is now apparent, however, that the use of genotoxicity batteries for assessing carcinogenic potential has limitations including an overall low specificity and a limited ability to detect carcinogens acting via ‘nongenotoxic’ mechanisms. In vitro Cell Transformation models, because they measure a chemical's ability to induce preneoplastic or neoplastic endpoints regardless of mechanism, may fulfil the current need for an in vitro biologically relevant model with increased predictiveness for determining carcinogenic potential. This review will focus on data demonstrating the similarities of chemically induced Cell Transformation in vitro to carcinogenesis in vivo. Furthermore, a growing database demonstrating a high overall correlation between Cell Transformation results with those of the rodent bioassay will also be discussed. Finally, the inclusion of Cell Transformation approaches for assessing the carcinogenic potential of chemicals relative to currently used genotoxicity batteries will be presented.