The Experts below are selected from a list of 207 Experts worldwide ranked by ideXlab platform

John Digiovanni - One of the best experts on this subject based on the ideXlab platform.

  • A novel mechanism of skin tumor promotion involving interferon‐gamma (IFNγ)/signal transducer and activator of transcription‐1 (Stat1) signaling
    Molecular carcinogenesis, 2014
    Co-Authors: Ronald Bozeman, Erika L. Abel, Linda M Beltran, Everardo Macias, Tianyi Cheng, John Digiovanni
    Abstract:

    The current study was designed to explore the role of signal transducer and activator of transcription 1 (Stat1) during tumor promotion using the mouse skin multistage carcinogenesis model. Topical treatment with both 12-O-tetradecanoylphorbol-13-acetate (TPA) and 3-methyl-1,8-dihydroxy-9-anthrone (Chrysarobin or CHRY) led to rapid phosphorylation of Stat1 on both tyrosine (Y701) and serine (S727) residues in epidermis. CHRY treatment also led to upregulation of unphosphorylated Stat1 (uStat1) at later time points. CHRY treatment also led to upregulation of interferon regulatory factor 1 (IRF-1) mRNA and protein, which was dependent on Stat1. Further analyses demonstrated that topical treatment with CHRY but not TPA upregulated interferon-gamma (IFNγ) mRNA in the epidermis and that the induction of both IRF-1 and uStat1 was dependent on IFNγ signaling. Stat1 deficient (Stat1−/−) mice were highly resistant to skin tumor promotion by CHRY. In contrast, the tumor response (in terms of both papillomas and squamous cell carcinomas) was similar in Stat1−/− mice and wild-type littermates with TPA as the promoter. Maximal induction of both cyclooxygenase-2 and inducible nitric oxide synthase in epidermis following treatment with CHRY was also dependent on the presence of functional Stat1. These studies define a novel mechanism associated with skin tumor promotion by the anthrone class of tumor promoters involving upregulation of IFNγ signaling in the epidermis and downstream signaling through activated (phosphorylated) Stat1, IRF-1 and uStat1. © 2014 Wiley Periodicals, Inc.

  • Abstract 2556: Stat1 plays a major role in skin tumor promotion by Chrysarobin but not TPA
    Carcinogenesis, 2012
    Co-Authors: Ronald Bozeman, John Digiovanni
    Abstract:

    The cellular and molecular mechanisms that underlie promotion by diverse tumor promoting agents remain to be fully elucidated. Studies using Stat1 knockout (KO) mice have shown that they were highly resistant to two-stage skin carcinogenesis using Chrysarobin as the promoter. In contrast, Stat1 KO mice treated with 12-O-tetradecanoylphorbol 13-acetate (TPA) as the tumor promoter exhibited no significant differences in tumor formation. To further investigate mechanism(s) whereby Stat1 mediates skin tumor promotion by Chrysarobin Stat1 KO mice and wild-type (WT) controls were treated with the respective tumor promoters and Stat1-dependent signaling pathways were evaluated. Mice deficient in Stat1 displayed an attenuated induction of epidermal Cox-2 mRNA and protein as well as reduced PGE2 levels compared to WT controls following topical application of Chrysarobin, whereas, mice treated with TPA exhibited no significant differences in Cox-2 levels or PGE2 levels. Other results also suggest that Stat1 may regulate various cytokine/chemokines involved in the inflammatory response following Chrysarobin treatment. Preliminary experiments have also shown that Stat1 KO mice exhibit reduced induction of interferon regulatory factor-1 (IRF-1) following Chrysarobin treatment, compared to WT controls. In contrast, treatment with TPA caused no significant differences in expression of IRF-1. Collectively, these findings suggest that Chrysarobin may elicit a Stat1-dependent signaling response that is dependent on IRF-1, whereas TPA-mediated tumorigenesis is independent of this signaling pathway. These and other ongoing studies aimed at characterizing the role of Stat1 and IRF-1 signaling in Chrysarobin-mediated tumor promotion will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2556. doi:1538-7445.AM2012-2556

  • Abstract 2730: Role of Stat1 in skin tumor promotion
    Carcinogenesis, 2011
    Co-Authors: Ronald Bozeman, John Digiovanni, Erika L. Abel
    Abstract:

    Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Inflammation is a key component of cancer development in many tissues. Emerging clinical observations support the idea of a strong association of chronic inflammation and cancer. The JAK-STAT pathway is one of the major signaling pathways involved in modulating both pro- and anti-inflammatory responses. Aberrant expression of STATs has been reported in multiple human cancers and in animal models of tumorigenesis. Previous work performed in our lab demonstrated a role for Stat1 in mediating the promotion stage of epithelial multi-stage carcinogenesis in mouse skin when Chrysarobin was used as the promoting agent. To further investigate the role of Stat1 in Chrysarobin-mediated skin tumor promotion, Stat1 knockout (KO) mice and wild-type controls were treated with Chrysarobin and the inflammatory response was assessed. Stat1 deficiency caused a reduction in the dermal inflammatory response following a single topical application of Chrysarobin. In this regard, Stat1 KO mice had reduced dermal immune cell influx following Chrysarobin treatment. In particular, Stat1 KO mice exhibited reduced influx of macrophages following a single application. Other results also suggest that Stat1 may regulate various cytokine/chemokines involved in the inflammatory response following Chrysarobin treatment. Mice deficient in Stat1 displayed an attenuated induction of Cox-2 mRNA and protein compared to wild-type controls following a single application of Chrysarobin (200 nmol per mouse). This latter data suggest that Stat1 may be involved in the regulation of Cox-2 in keratinocytes. Collectively, these findings suggest that Stat1 may contribute to Chrysarobin-mediated skin tumor promotion by regulating, in part, levels of Cox-2, PGE2 and ultimately skin inflammation. These and other ongoing studies aimed at identifying the mechanistic basis for the role of Stat1 in Chrysarobin-mediated tumor promotion will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2730. doi:10.1158/1538-7445.AM2011-2730

  • Abstract 2480: Role of Stat1 in epithelial carcinogenesis
    Carcinogenesis, 2010
    Co-Authors: Ronald Bozeman, Erika L. Abel, John Digiovanni
    Abstract:

    Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Aberrant expression and/ or activity of STATs 1, 3, and 5 have been reported in multiple human cancers as well as in murine models of tumorigenesis. Previous work performed in our lab demonstrated a critical role for Stat3 in mediating the initiation and promotion stages of epithelial multi-stage carcinogenesis in mouse skin. In light of these findings, we have begun investigating the role of other STATs, particularly Stat1, in multistage skin carcinogenesis using both wild-type and Stat1 knockout (KO) mice. Western blot analyses revealed that topical application of the skin tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and Chrysarobin induced phosphorylation of Stat1 in mouse epidermis. In addition, following treatment with Chrysarobin, the level of total Stat1 protein was also dramatically elevated. To further investigate the role of Stat1 during epithelial carcinogenesis, Stat1 KO mice and wild-type littermates were initiated with 25 nmol DMBA and promoted with either 6.8 nmol TPA or 220 nmol Chrysarobin. No significant differences were observed in either tumor incidence or multiplicity when TPA was used as the promoting agent, suggesting that Stat1 does not play a significant role in TPA-mediated skin tumor promotion. In contrast, Stat1 KO mice exhibited a dramatic reduction in both tumor multiplicity and incidence as compared to wild-type littermates when Chrysarobin was used as the promoting agent. Additionally, following topical treatment with Chrysarobin, Stat1 KO mice had a reduced epidermal proliferative response. To further investigate the impact of Stat1 deletion on Chrysarobin-induced tumor promotion, Stat1 KO mice and wild-type controls were treated topically with Chrysarobin and the inflammatory response was assessed. Stat1 KO mice displayed a significant reduction in Cox-2 induction compared to wild-type controls. Preliminary findings also showed that Stat1 KO mice have reduced immune cell influx following Chrysarobin treatment. To investigate the potential role of reactive oxygen species (ROS) in the effects of Chrysarobin on Stat1 activation, the dorsal skin of FVB mice were pre-treated topically with the anti-oxidants ascorbyl palmitate and α-tocopherol acetate. Topical application of α-tocopherol acetate significantly attenuated the epidermal proliferative response and Stat1 activation suggesting that Chrysarobin-mediated generation of ROS may play a role in its effects on Stat1 during tumor promotion. Additional studies are underway to further determine the mechanistic basis for the role of Stat1 in Chrysarobin-mediated tumor promotion. Supported by NIH grant CA 76520. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2480.

  • Abstract 2475: Effect of mTOR inhibition by rapamycin on promotion of skin tumors in BK5. Aktwt transgenic mice
    Carcinogenesis, 2010
    Co-Authors: Okkyung Rho, Guiyu Jiang, Allyson Sandifer, John Digiovanni
    Abstract:

    Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Akt is a serine/threonine kinase involved in a variety of cellular responses including cell survival and proliferation. It has been shown that PI3K/Akt signaling is frequently altered (upregulated) in human cancers. mTOR is one of the Akt downstream signaling pathways that regulates protein synthesis, cell growth and proliferation. mTOR exists in two complexes, mTORC1 and mTORC2. Our laboratory previously reported that tumor promoters including TPA, okadaic acid (OA), and Chrysarobin (CHRY) activate epidermal Akt after topical treatment of mouse epidermis and mouse primary cultured keratinocytes. Activation of Akt during tumor promoter treatment leads to enhanced downstream signaling including mTORC1 pathways. BK5. Aktwt transgenic mice where Akt is overexpressed in basal epidermis were significantly more sensitive to two-stage carcinogenesis, showing tumors with a much shorter latency, considerably larger in size, and enhanced progression of papillomas to SCCs. Importantly, Akt transgenic mice showed significant elevations in several downstream signaling pathways both in the absence and presence of TPA, including mTORC1 activity. Collectively, the studies with transgenic mice overexpressing Akt in epidermis (BK5.Aktwt) have suggested that activation of mTORC1 signaling may contribute to the process of skin tumor promotion. In this study, we have examined the ability of rapamycin, a known inhibitor of mTOR, on mTORC1 signaling in relation to its effect on TPA-induced epidermal cell proliferation and skin tumor promotion. Rapamycin given at doses of 1 μmol, 100 nmol, 20 nmol, and 5 nmol 30 min prior to 6.8 nmol TPA treatment inhibited mTORC1 activity in a dose-dependent manner. Notably, in a multiple treatment regimen (4 applications of rapamycin and TPA over a two week period) high doses of rapamycin significantly inhibited TPA-induced Akt phosphorylation at serine 473 as well as mTORC1 signaling in a dose dependent way, suggesting mTORC2 inhibition induced by prolonged high dose rapamycin treatment. The ability of rapamycin (at doses of 100, 20, and 5 nmol per mouse) to inhibit skin tumor promotion by TPA in BK5. Aktwt transgenic mice was compared with wild-type mice. Rapamycin significantly reduced TPA promotion in BK5.Aktwt mice, however, it was less effective compared to similar doses used in wild-type mice. The data demonstrate that rapamycin, although less effective, still retained significant inhibitory activity toward TPA promotion even when Akt and mTOR activities were elevated. These data demonstrate an important role for mTOR signaling in skin tumor promotion of TPA. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2475.

Linda M Beltran - One of the best experts on this subject based on the ideXlab platform.

  • A novel mechanism of skin tumor promotion involving interferon‐gamma (IFNγ)/signal transducer and activator of transcription‐1 (Stat1) signaling
    Molecular carcinogenesis, 2014
    Co-Authors: Ronald Bozeman, Erika L. Abel, Linda M Beltran, Everardo Macias, Tianyi Cheng, John Digiovanni
    Abstract:

    The current study was designed to explore the role of signal transducer and activator of transcription 1 (Stat1) during tumor promotion using the mouse skin multistage carcinogenesis model. Topical treatment with both 12-O-tetradecanoylphorbol-13-acetate (TPA) and 3-methyl-1,8-dihydroxy-9-anthrone (Chrysarobin or CHRY) led to rapid phosphorylation of Stat1 on both tyrosine (Y701) and serine (S727) residues in epidermis. CHRY treatment also led to upregulation of unphosphorylated Stat1 (uStat1) at later time points. CHRY treatment also led to upregulation of interferon regulatory factor 1 (IRF-1) mRNA and protein, which was dependent on Stat1. Further analyses demonstrated that topical treatment with CHRY but not TPA upregulated interferon-gamma (IFNγ) mRNA in the epidermis and that the induction of both IRF-1 and uStat1 was dependent on IFNγ signaling. Stat1 deficient (Stat1−/−) mice were highly resistant to skin tumor promotion by CHRY. In contrast, the tumor response (in terms of both papillomas and squamous cell carcinomas) was similar in Stat1−/− mice and wild-type littermates with TPA as the promoter. Maximal induction of both cyclooxygenase-2 and inducible nitric oxide synthase in epidermis following treatment with CHRY was also dependent on the presence of functional Stat1. These studies define a novel mechanism associated with skin tumor promotion by the anthrone class of tumor promoters involving upregulation of IFNγ signaling in the epidermis and downstream signaling through activated (phosphorylated) Stat1, IRF-1 and uStat1. © 2014 Wiley Periodicals, Inc.

  • Activation of epidermal akt by diverse mouse skin tumor promoters.
    Molecular cancer research : MCR, 2007
    Co-Authors: Okkyung Rho, Linda M Beltran, Erik Wilker, John Digiovanni
    Abstract:

    Akt is a serine/threonine kinase involved in a variety of cellular responses, including cell proliferation and cell survival. Recent studies from our laboratory suggest that Akt signaling may play an important role in skin tumor promotion. To explore this premise, we examined epidermal Akt activation and signaling in response to chemically diverse skin tumor promoters. Mice received single or multiple applications of 12-O-tetradecanoylphorbol-13-acetate (TPA), okadaic acid, or Chrysarobin. All three tumor promoters were able to activate epidermal Akt as early as 1 h after treatment. Activation of Akt following tumor promoter treatment led to enhanced downstream signaling, including hyperphosphorylation of glycogen synthase kinase-3beta and Bad. Structure activity studies with phorbol ester analogues revealed that the magnitude of activation paralleled tumor-promoting activity. In cultured primary keratinocytes, TPA treatment also led to activation of Akt. Activation of the epidermal growth factor receptor (EGFR) seemed to underlie the ability of TPA to activate Akt as both PD153035, an inhibitor of EGFR, and GW2974, a dual-specific inhibitor of both EGFR and erbB2, were able to effectively reduce TPA-induced Akt phosphorylation as well as TPA-stimulated EGFR and erbB2 tyrosine phosphorylation in a dose-dependent manner. Furthermore, inhibition of protein kinase C (PKC) activity blocked TPA-stimulated heparin-binding EGF production and EGFR transactivation. Inhibition of PKC also led to a decreased association of Akt with the PP2A catalytic subunit, leading to increased Akt phosphorylation. However, combination of EGFR inhibitor and PKC inhibitor completely abrogated TPA-induced activation of Akt. Collectively, the current results support the hypothesis that elevated Akt activity and subsequent activation of downstream signaling pathways contribute significantly to skin tumor promotion. In addition, signaling through the EGFR via EGFR homodimers or EGFR/erbB2 heterodimers may be the primary event leading to Akt activation during tumor promotion in mouse skin.

  • Enhancement of susceptibility to diverse skin tumor promoters by activation of the insulin-like growth factor-1 receptor in the epidermis of transgenic mice.
    Molecular carcinogenesis, 1999
    Co-Authors: Erik Wilker, Linda M Beltran, Kaoru Kiguchi, Tim Rupp, David Bol, John Digiovanni
    Abstract:

    Insulin-like growth factor-1 (IGF-1) and its receptor are believed to play an important role in mitogenesis and neoplastic transformation. The purpose of this study was to further examine the role of IGF-1 during tumor promotion in mouse skin. HK1.IGF1 transgenic mice, which overexpress IGF-1 in epidermis via the human keratin 1 promoter, were previously shown to be hypersensitive to skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA). We examined these mice for their sensitivity to diverse classes of tumor-promoting agents. HK1.IGF-1 transgenic mice initiated with 7,12-dimethylbenz[a]anthracene were more sensitive to treatment with a wide variety of tumor promoters, including Chrysarobin, okadaic acid, and benzoyl peroxide, which resulted in more rapid development of tumors and a dramatic increase in the number of tumors per mouse compared with corresponding non-transgenic mice treated with the same compounds. Histological analyses of skin from HK1.IGF-1 mice treated with various tumor promoters revealed that these mice were also more sensitive to the induction of epidermal hyperplasia and cell proliferation. Analysis of the IGF-1 receptor (IGF-1r) and epidermal growth factor (EGFr) in the epidermis of TPA-treated HK1.IGF-1 transgenic and non-transgenic mice revealed that both receptors were activated (hyperphosphorylated on tyrosine residues), and the level of activation was higher in transgenic mice. The mechanism for the increased sensitivity of HK1.IGF-1 mice to tumor promoters may involve cooperation between the IGF-1r and EGFr signaling pathways. Our data suggest that IGF-1r signaling may play an important role in the process of tumor promotion by diverse classes of tumor promoters.

  • Altered expression of epidermal growth factor receptor ligands in tumor promoter-treated mouse epidermis and in primary mouse skin tumors induced by an initiation-promotion protocol.
    Molecular carcinogenesis, 1998
    Co-Authors: Kaoru Kiguchi, Linda M Beltran, Tim Rupp, John Digiovanni
    Abstract:

    Multiple epidermal growth factor receptor (EGFr) ligands have been identified, including transforming growth factor α (TGFα), heparin-binding epidermal growth factor (HB-EGF), amphiregulin (AR), and betacellulin (BTC). Previous work from our laboratory demonstrated that TGFα mRNA and protein are upregulated in epidermis during tumor-promoter treatment of mouse skin and in skin tumors produced by initiation-promotion regimens. The purpose of the study described here was to explore the role of other EGFr ligands in multistage skin carcinogenesis. A single topical treatment of either 12-O-tetradecanoylphorbol-13-acetate (TPA) or Chrysarobin or a single full-thickness wound induced the expression of HB-EGF and AR in mRNA samples isolated from whole mouse skin. However, only full-thickness wounding significantly elevated expression of the BTC transcript. The levels of HB-EGF and AR transcripts were significantly elevated in skin tumors (both papillomas and squamous cell carcinomas) induced by initiation-promotion protocols. BTC transcript levels were low and barely detectable in all skin tumors examined. The level of keratinocyte growth factor (KGF) mRNA was also examined as a possible mechanism for upregulation of EGFr ligands. Only full-thickness wounding significantly elevated KGF transcript levels in whole-skin RNA samples. Furthermore, no evidence for upregulation of KGF mRNA in skin tumors was obtained. The results are discussed in terms of the role of EGFr activation in skin carcinogenesis and the mechanisms for altered regulation of EGFr ligands. Mol. Carcinog. 22:73–83, 1998. © 1998 Wiley-Liss, Inc.

  • Elevation of transforming growth factor‐α mRNA and protein expression by diverse tumor promoters in sencar mouse epidermis
    Molecular carcinogenesis, 1995
    Co-Authors: Kaoru Kiguchi, Linda M Beltran, Jinsong You, Okkyung Rho, John Digiovanni
    Abstract:

    The study presented here was designed to further investigate the role of transforming growth factor-alpha (TGF alpha) in skin tumor promotion by examining the ability of 12-O-tetradecanoylphorbol-13-acetate (TPA) and several non-phorbol ester promoters to alter TGF alpha mRNA and protein levels in mouse epidermis. Total RNA was isolated from SENCAR mouse epidermis at various times after single topical treatments with TPA (3.4 nmol), Chrysarobin (220 nmol), okadaic acid (2.5 nmol), and thapsigargin (8.5 nmol). Northern analyses of these isolated RNA samples revealed that all four tumor promoters transiently elevated TGF alpha mRNA levels. Whereas TPA, okadaic acid, and thapsigarin elevated TGF alpha mRNA levels over similar time courses (peak at 4-8 h), Chrysarobin elevated TGF alpha mRNA levels with a markedly delayed time course (peak at 24-48 h). More detailed studies with TPA also revealed that multiple treatments (four over a 2-wk period) transiently elevated TGF alpha mRNA in both the epidermis and the dermis. The time courses for changes in TGF alpha mRNA after multiple TPA treatments were similar for both tissues. To facilitate studies of altered TGF alpha mRNA expression in mouse epidermis and possibly other mouse tissues, a semiquantitative reverse transcriptase-polymerase chain reaction method was developed. This method faithfully revealed changes in TGF alpha mRNA levels with all four tumor-promoting agents similar to those determined by northern blot analyses. Immunofluorescence analysis of frozen sections from promoter-treated skin revealed elevated TGF alpha protein levels in both epidermis and dermis, although staining was most intense in the epidermal layer. Immunofluorescence analysis of epidermal hyperplasia adjacent to a full-thickness wound also demonstrated significant epidermal TGF alpha staining. Collectively, these results indicate that mechanistically diverse tumor promoter stimuli elevate TGF alpha mRNA and protein in SENCAR mouse epidermis. Elevated levels of TGF alpha may play an essential role in mitogenic stimulation during tumor promotion by diverse promoting stimuli.

Erika L. Abel - One of the best experts on this subject based on the ideXlab platform.

  • A novel mechanism of skin tumor promotion involving interferon‐gamma (IFNγ)/signal transducer and activator of transcription‐1 (Stat1) signaling
    Molecular carcinogenesis, 2014
    Co-Authors: Ronald Bozeman, Erika L. Abel, Linda M Beltran, Everardo Macias, Tianyi Cheng, John Digiovanni
    Abstract:

    The current study was designed to explore the role of signal transducer and activator of transcription 1 (Stat1) during tumor promotion using the mouse skin multistage carcinogenesis model. Topical treatment with both 12-O-tetradecanoylphorbol-13-acetate (TPA) and 3-methyl-1,8-dihydroxy-9-anthrone (Chrysarobin or CHRY) led to rapid phosphorylation of Stat1 on both tyrosine (Y701) and serine (S727) residues in epidermis. CHRY treatment also led to upregulation of unphosphorylated Stat1 (uStat1) at later time points. CHRY treatment also led to upregulation of interferon regulatory factor 1 (IRF-1) mRNA and protein, which was dependent on Stat1. Further analyses demonstrated that topical treatment with CHRY but not TPA upregulated interferon-gamma (IFNγ) mRNA in the epidermis and that the induction of both IRF-1 and uStat1 was dependent on IFNγ signaling. Stat1 deficient (Stat1−/−) mice were highly resistant to skin tumor promotion by CHRY. In contrast, the tumor response (in terms of both papillomas and squamous cell carcinomas) was similar in Stat1−/− mice and wild-type littermates with TPA as the promoter. Maximal induction of both cyclooxygenase-2 and inducible nitric oxide synthase in epidermis following treatment with CHRY was also dependent on the presence of functional Stat1. These studies define a novel mechanism associated with skin tumor promotion by the anthrone class of tumor promoters involving upregulation of IFNγ signaling in the epidermis and downstream signaling through activated (phosphorylated) Stat1, IRF-1 and uStat1. © 2014 Wiley Periodicals, Inc.

  • Proteomic and pathway analyses reveal a network of inflammatory genes associated with differences in skin tumor promotion susceptibility in DBA/2 and C57BL/6 mice.
    Carcinogenesis, 2012
    Co-Authors: Jianjun Shen, Erika L. Abel, Penny K. Riggs, John Repass, Sean C. Hensley, Lisa J. Schroeder, Angelina Temple, Alexander Chau, S. Alex Mcclellan, Okkyung Rho
    Abstract:

    Genetic susceptibility to two-stage skin carcinogenesis is known to vary significantly among different stocks and strains of mice. In an effort to identify specific protein changes or altered signaling pathways associated with skin tumor promotion susceptibility, a proteomic approach was used to examine and identify proteins that were differentially expressed in epidermis between promotion-sensitive DBA/2 and promotion-resistant C57BL/6 mice following treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). We identified 19 differentially expressed proteins of which 5 were the calcium-binding proteins annexin A1, parvalbumin α, S100A8, S100A9, and S100A11. Further analyses revealed that S100A8 and S100A9 protein levels were also similarly differentially upregulated in epidermis of DBA/2 versus C57BL/6 mice following topical treatment with two other skin tumor promoters, okadaic acid and Chrysarobin. Pathway analysis of all 19 identified proteins from the present study suggested that these proteins were components of several networks that included inflammation-associated proteins known to be involved in skin tumor promotion (e.g. TNF-α, NFκB). Follow-up studies revealed that Tnf, Nfkb1, Il22, Il1b, Cxcl1, Cxcl2 and Cxcl5 mRNAs were highly expressed in epidermis of DBA/2 compared with C57BL/6 mice at 24h following treatment with TPA. Furthermore, NFκB (p65) was also highly activated at the same time point (as measured by phosphorylation at ser276) in epidermis of DBA/2 mice compared with C57BL/6 mice. Taken together, the present data suggest that differential expression of genes involved in inflammatory pathways in epidermis may play a key role in genetic differences in susceptibility to skin tumor promotion in DBA/2 and C57BL/6 mice.

  • Identification of a Network of Inflammatory Genes Associated with Differences in Skin Tumor Promotion Susceptibility
    Journal of biomolecular techniques, 2012
    Co-Authors: Erika L. Abel, Penny K. Riggs, John Repass, Sean C. Hensley, Lisa J. Schroeder, Angelina Temple, Alexander Chau, S. Alex Mcclellan, Michael D. Ward, O. John Semmes
    Abstract:

    Genetic susceptibility to two-stage skin carcinogenesis is known to vary significantly among different stocks and strains of mice. In an effort to identify specific protein changes or altered signaling pathways associated with skin tumor promotion susceptibility, a proteomic approach of two-dimensional (2-D) gel electrophoresis and mass spectrometry was used to examine and identify proteins that were differentially expressed in epidermis between promotion-sensitive DBA/2 and promotion-resistant C57BL/6 mice following treatment with the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate. We identified 19 differentially expressed proteins of which 5 were the calcium-binding proteins including annexin A1, parvalbumin a, S100A8, S100A9, and S100A11. The differential expression of two of these calcium-binding proteins, S100A8 and S100A9, was further examined and validated by the following methods: i) one-dimensional (1-D) Western blot analysis; ii) 2-D Western blot analysis; iii) immunohistochemical analysis; and iv) quantitative real-time PCR. Further analyses revealed that S100A8 and S100A9 protein levels were also similarly differentially up-regulated in epidermis of DBA/2 vs C57BL/6 mice following topical treatment with two other skin tumor promoters, okadaic acid and Chrysarobin. Pathway analysis of all 19 identified proteins from the present study suggested that these proteins were components of several networks that included inflammation associated proteins known to be involved in skin tumor promotion (e.g. TNF-a, NFkB). Follow-up studies revealed that Tnf, Nfkb1, Il22, and Il1a mRNAs were highly expressed in epidermis of TPA-treated DBA/2 (>2-fold, P

  • Abstract 2730: Role of Stat1 in skin tumor promotion
    Carcinogenesis, 2011
    Co-Authors: Ronald Bozeman, John Digiovanni, Erika L. Abel
    Abstract:

    Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Inflammation is a key component of cancer development in many tissues. Emerging clinical observations support the idea of a strong association of chronic inflammation and cancer. The JAK-STAT pathway is one of the major signaling pathways involved in modulating both pro- and anti-inflammatory responses. Aberrant expression of STATs has been reported in multiple human cancers and in animal models of tumorigenesis. Previous work performed in our lab demonstrated a role for Stat1 in mediating the promotion stage of epithelial multi-stage carcinogenesis in mouse skin when Chrysarobin was used as the promoting agent. To further investigate the role of Stat1 in Chrysarobin-mediated skin tumor promotion, Stat1 knockout (KO) mice and wild-type controls were treated with Chrysarobin and the inflammatory response was assessed. Stat1 deficiency caused a reduction in the dermal inflammatory response following a single topical application of Chrysarobin. In this regard, Stat1 KO mice had reduced dermal immune cell influx following Chrysarobin treatment. In particular, Stat1 KO mice exhibited reduced influx of macrophages following a single application. Other results also suggest that Stat1 may regulate various cytokine/chemokines involved in the inflammatory response following Chrysarobin treatment. Mice deficient in Stat1 displayed an attenuated induction of Cox-2 mRNA and protein compared to wild-type controls following a single application of Chrysarobin (200 nmol per mouse). This latter data suggest that Stat1 may be involved in the regulation of Cox-2 in keratinocytes. Collectively, these findings suggest that Stat1 may contribute to Chrysarobin-mediated skin tumor promotion by regulating, in part, levels of Cox-2, PGE2 and ultimately skin inflammation. These and other ongoing studies aimed at identifying the mechanistic basis for the role of Stat1 in Chrysarobin-mediated tumor promotion will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2730. doi:10.1158/1538-7445.AM2011-2730

  • Abstract 2729: Proteomic analysis reveals a network of inflammatory genes in epidermis associated with skin tumor promotion susceptibility in DBA/2 and C57BL/6 mice
    Carcinogenesis, 2011
    Co-Authors: Jianjun Shen, Erika L. Abel, Penny K. Riggs, John Repass, Sean C. Hensley, Lisa J. Schroeder, Alexander Chau, Joe M. Angel, Angelina Traner, Michael D. Ward
    Abstract:

    Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Genetic susceptibility to two-stage skin carcinogenesis is known to vary significantly among different stocks and strains of mice. In an effort to identify specific protein changes or altered signaling pathways associated with tumor promotion susceptibility by the phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), a proteomic approach of two-dimensional (2-D) gel electrophoresis and mass spectrometry was used. In these experiments, we examined epidermal protein lysates and identified proteins that were differentially expressed in epidermis between promotion-sensitive DBA/2 and promotion-resistant C57BL/6 mice following TPA treatment. Among 19 differentially expressed proteins identified using this methodology were two calcium-binding proteins, S100A8 and S100A9. Their differential expression was further examined and validated by one or more of the following methods: i) one-dimensional (1-D) Western blot analysis; ii) 2-D Western blot analysis; iii) immunohistochemical analysis; and iv) quantitative real-time PCR. Further analyses revealed that S100A8 and S100A9 protein levels were also similarly differentially up-regulated in epidermis of DBA/2 vs C57BL/6 mice following topical treatment with two other tumor promoters, okadaic acid and Chrysarobin. Pathway analysis of all 19 identified proteins from the present study suggested that S100A8/A9 could be linked to several inflammatory networks. Further analyses revealed significantly increased expression of several inflammation-related genes including TNF-α, NFκB and IL-22 in epidermis of TPA-treated DBA/2 mice. Follow-up studies confirmed that these three inflammation related genes were upregulated in epidermis of TPA-treated DBA/2 mice compared to similarly treated C57BL/6 mice. These data suggest that differential expression of inflammation related genes in epidermis contributes to TPA-induced inflammation and skin tumor promotion susceptibility in DBA/2 mice. Taken together, our present data provide further insight into potential molecular mechanisms for the differential susceptibility of DBA/2 and C57BL/6 mice in terms of both inflammation and skin tumor promotion. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2729. doi:10.1158/1538-7445.AM2011-2729

Okkyung Rho - One of the best experts on this subject based on the ideXlab platform.

  • Proteomic and pathway analyses reveal a network of inflammatory genes associated with differences in skin tumor promotion susceptibility in DBA/2 and C57BL/6 mice.
    Carcinogenesis, 2012
    Co-Authors: Jianjun Shen, Erika L. Abel, Penny K. Riggs, John Repass, Sean C. Hensley, Lisa J. Schroeder, Angelina Temple, Alexander Chau, S. Alex Mcclellan, Okkyung Rho
    Abstract:

    Genetic susceptibility to two-stage skin carcinogenesis is known to vary significantly among different stocks and strains of mice. In an effort to identify specific protein changes or altered signaling pathways associated with skin tumor promotion susceptibility, a proteomic approach was used to examine and identify proteins that were differentially expressed in epidermis between promotion-sensitive DBA/2 and promotion-resistant C57BL/6 mice following treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). We identified 19 differentially expressed proteins of which 5 were the calcium-binding proteins annexin A1, parvalbumin α, S100A8, S100A9, and S100A11. Further analyses revealed that S100A8 and S100A9 protein levels were also similarly differentially upregulated in epidermis of DBA/2 versus C57BL/6 mice following topical treatment with two other skin tumor promoters, okadaic acid and Chrysarobin. Pathway analysis of all 19 identified proteins from the present study suggested that these proteins were components of several networks that included inflammation-associated proteins known to be involved in skin tumor promotion (e.g. TNF-α, NFκB). Follow-up studies revealed that Tnf, Nfkb1, Il22, Il1b, Cxcl1, Cxcl2 and Cxcl5 mRNAs were highly expressed in epidermis of DBA/2 compared with C57BL/6 mice at 24h following treatment with TPA. Furthermore, NFκB (p65) was also highly activated at the same time point (as measured by phosphorylation at ser276) in epidermis of DBA/2 mice compared with C57BL/6 mice. Taken together, the present data suggest that differential expression of genes involved in inflammatory pathways in epidermis may play a key role in genetic differences in susceptibility to skin tumor promotion in DBA/2 and C57BL/6 mice.

  • Abstract 2475: Effect of mTOR inhibition by rapamycin on promotion of skin tumors in BK5. Aktwt transgenic mice
    Carcinogenesis, 2010
    Co-Authors: Okkyung Rho, Guiyu Jiang, Allyson Sandifer, John Digiovanni
    Abstract:

    Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Akt is a serine/threonine kinase involved in a variety of cellular responses including cell survival and proliferation. It has been shown that PI3K/Akt signaling is frequently altered (upregulated) in human cancers. mTOR is one of the Akt downstream signaling pathways that regulates protein synthesis, cell growth and proliferation. mTOR exists in two complexes, mTORC1 and mTORC2. Our laboratory previously reported that tumor promoters including TPA, okadaic acid (OA), and Chrysarobin (CHRY) activate epidermal Akt after topical treatment of mouse epidermis and mouse primary cultured keratinocytes. Activation of Akt during tumor promoter treatment leads to enhanced downstream signaling including mTORC1 pathways. BK5. Aktwt transgenic mice where Akt is overexpressed in basal epidermis were significantly more sensitive to two-stage carcinogenesis, showing tumors with a much shorter latency, considerably larger in size, and enhanced progression of papillomas to SCCs. Importantly, Akt transgenic mice showed significant elevations in several downstream signaling pathways both in the absence and presence of TPA, including mTORC1 activity. Collectively, the studies with transgenic mice overexpressing Akt in epidermis (BK5.Aktwt) have suggested that activation of mTORC1 signaling may contribute to the process of skin tumor promotion. In this study, we have examined the ability of rapamycin, a known inhibitor of mTOR, on mTORC1 signaling in relation to its effect on TPA-induced epidermal cell proliferation and skin tumor promotion. Rapamycin given at doses of 1 μmol, 100 nmol, 20 nmol, and 5 nmol 30 min prior to 6.8 nmol TPA treatment inhibited mTORC1 activity in a dose-dependent manner. Notably, in a multiple treatment regimen (4 applications of rapamycin and TPA over a two week period) high doses of rapamycin significantly inhibited TPA-induced Akt phosphorylation at serine 473 as well as mTORC1 signaling in a dose dependent way, suggesting mTORC2 inhibition induced by prolonged high dose rapamycin treatment. The ability of rapamycin (at doses of 100, 20, and 5 nmol per mouse) to inhibit skin tumor promotion by TPA in BK5. Aktwt transgenic mice was compared with wild-type mice. Rapamycin significantly reduced TPA promotion in BK5.Aktwt mice, however, it was less effective compared to similar doses used in wild-type mice. The data demonstrate that rapamycin, although less effective, still retained significant inhibitory activity toward TPA promotion even when Akt and mTOR activities were elevated. These data demonstrate an important role for mTOR signaling in skin tumor promotion of TPA. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2475.

  • Activation of epidermal akt by diverse mouse skin tumor promoters.
    Molecular cancer research : MCR, 2007
    Co-Authors: Okkyung Rho, Linda M Beltran, Erik Wilker, John Digiovanni
    Abstract:

    Akt is a serine/threonine kinase involved in a variety of cellular responses, including cell proliferation and cell survival. Recent studies from our laboratory suggest that Akt signaling may play an important role in skin tumor promotion. To explore this premise, we examined epidermal Akt activation and signaling in response to chemically diverse skin tumor promoters. Mice received single or multiple applications of 12-O-tetradecanoylphorbol-13-acetate (TPA), okadaic acid, or Chrysarobin. All three tumor promoters were able to activate epidermal Akt as early as 1 h after treatment. Activation of Akt following tumor promoter treatment led to enhanced downstream signaling, including hyperphosphorylation of glycogen synthase kinase-3beta and Bad. Structure activity studies with phorbol ester analogues revealed that the magnitude of activation paralleled tumor-promoting activity. In cultured primary keratinocytes, TPA treatment also led to activation of Akt. Activation of the epidermal growth factor receptor (EGFR) seemed to underlie the ability of TPA to activate Akt as both PD153035, an inhibitor of EGFR, and GW2974, a dual-specific inhibitor of both EGFR and erbB2, were able to effectively reduce TPA-induced Akt phosphorylation as well as TPA-stimulated EGFR and erbB2 tyrosine phosphorylation in a dose-dependent manner. Furthermore, inhibition of protein kinase C (PKC) activity blocked TPA-stimulated heparin-binding EGF production and EGFR transactivation. Inhibition of PKC also led to a decreased association of Akt with the PP2A catalytic subunit, leading to increased Akt phosphorylation. However, combination of EGFR inhibitor and PKC inhibitor completely abrogated TPA-induced activation of Akt. Collectively, the current results support the hypothesis that elevated Akt activity and subsequent activation of downstream signaling pathways contribute significantly to skin tumor promotion. In addition, signaling through the EGFR via EGFR homodimers or EGFR/erbB2 heterodimers may be the primary event leading to Akt activation during tumor promotion in mouse skin.

  • Activation of Akt and mTOR in mouse keratinocytes by skin tumor promoters
    Cancer Research, 2007
    Co-Authors: Okkyung Rho, Guiyu Jiang, John Digiovanni
    Abstract:

    2621 Akt is a serine/threonine kinase involved in a variety of cellular responses including cell proliferation and survival. Tumor promoters including TPA, okadaic acid (OA), and Chrysarobin (CHRY) activate epidermal Akt early after tumor promoter treatment. Activation of Akt during tumor promoter treatment leads to enhanced downstream signaling. In the present studies, we demonstrated that phosphorylation of Akt was elevated in cultured primary keratinocytes exposed to TPA. TPA-induced activation of Akt was mediated by the PI3K and PDK-1-dependent pathways, not by MAPK pathways. TPA-induced PKC activation in cultured mouse keratinocytes results in increased HB-EGF production, followed by phosphorylation of the EGFr. The pan PKC inhibitor, bisindolylmaleimide I abrogates HB-EGF production and EGFr phosphorylation. However, PKC inhibition by bisindolylmaleimide I before or after TPA treatment stabilizes Akt phosphorylation even in the presence of reduced EGFr activation. The potent inhibitors of EGFr/erbB2 (GW2974) and EGFr (PD153035) reduced TPA-stimulated Akt activation as well as EGFr tyrosine phosphorylation in a dose dependent manner. Furthermore, phosphorylation of mTOR, an Akt downstream component was induced by TPA in a biphasic way; early activation of mTOR appeared to be PKC-mediated and then later phosphorylated through activation of Akt. The current results support the hypothesis that elevated Akt activity and subsequent activation of downstream signaling pathways is a common event in mouse keratinocyts following treatment with diverse skin tumor promoters. In addition, signaling through the EGFr via PI3K and PDK-1 dependent pathways may be the primary event leading to Akt activation during tumor promotion in mouse skin. Finally, activation of mTOR may also be critical for mouse skin tumor promotion. Together with data showing that overexpression of Akt in epidermis of transgenic mice enhances susceptibility to skin tumor promotion, the current results further demonstrate the importance of Akt signaling in epithelial carcinogenesis.

  • Elevation of transforming growth factor‐α mRNA and protein expression by diverse tumor promoters in sencar mouse epidermis
    Molecular carcinogenesis, 1995
    Co-Authors: Kaoru Kiguchi, Linda M Beltran, Jinsong You, Okkyung Rho, John Digiovanni
    Abstract:

    The study presented here was designed to further investigate the role of transforming growth factor-alpha (TGF alpha) in skin tumor promotion by examining the ability of 12-O-tetradecanoylphorbol-13-acetate (TPA) and several non-phorbol ester promoters to alter TGF alpha mRNA and protein levels in mouse epidermis. Total RNA was isolated from SENCAR mouse epidermis at various times after single topical treatments with TPA (3.4 nmol), Chrysarobin (220 nmol), okadaic acid (2.5 nmol), and thapsigargin (8.5 nmol). Northern analyses of these isolated RNA samples revealed that all four tumor promoters transiently elevated TGF alpha mRNA levels. Whereas TPA, okadaic acid, and thapsigarin elevated TGF alpha mRNA levels over similar time courses (peak at 4-8 h), Chrysarobin elevated TGF alpha mRNA levels with a markedly delayed time course (peak at 24-48 h). More detailed studies with TPA also revealed that multiple treatments (four over a 2-wk period) transiently elevated TGF alpha mRNA in both the epidermis and the dermis. The time courses for changes in TGF alpha mRNA after multiple TPA treatments were similar for both tissues. To facilitate studies of altered TGF alpha mRNA expression in mouse epidermis and possibly other mouse tissues, a semiquantitative reverse transcriptase-polymerase chain reaction method was developed. This method faithfully revealed changes in TGF alpha mRNA levels with all four tumor-promoting agents similar to those determined by northern blot analyses. Immunofluorescence analysis of frozen sections from promoter-treated skin revealed elevated TGF alpha protein levels in both epidermis and dermis, although staining was most intense in the epidermal layer. Immunofluorescence analysis of epidermal hyperplasia adjacent to a full-thickness wound also demonstrated significant epidermal TGF alpha staining. Collectively, these results indicate that mechanistically diverse tumor promoter stimuli elevate TGF alpha mRNA and protein in SENCAR mouse epidermis. Elevated levels of TGF alpha may play an essential role in mitogenic stimulation during tumor promotion by diverse promoting stimuli.

Ronald Bozeman - One of the best experts on this subject based on the ideXlab platform.

  • A novel mechanism of skin tumor promotion involving interferon‐gamma (IFNγ)/signal transducer and activator of transcription‐1 (Stat1) signaling
    Molecular carcinogenesis, 2014
    Co-Authors: Ronald Bozeman, Erika L. Abel, Linda M Beltran, Everardo Macias, Tianyi Cheng, John Digiovanni
    Abstract:

    The current study was designed to explore the role of signal transducer and activator of transcription 1 (Stat1) during tumor promotion using the mouse skin multistage carcinogenesis model. Topical treatment with both 12-O-tetradecanoylphorbol-13-acetate (TPA) and 3-methyl-1,8-dihydroxy-9-anthrone (Chrysarobin or CHRY) led to rapid phosphorylation of Stat1 on both tyrosine (Y701) and serine (S727) residues in epidermis. CHRY treatment also led to upregulation of unphosphorylated Stat1 (uStat1) at later time points. CHRY treatment also led to upregulation of interferon regulatory factor 1 (IRF-1) mRNA and protein, which was dependent on Stat1. Further analyses demonstrated that topical treatment with CHRY but not TPA upregulated interferon-gamma (IFNγ) mRNA in the epidermis and that the induction of both IRF-1 and uStat1 was dependent on IFNγ signaling. Stat1 deficient (Stat1−/−) mice were highly resistant to skin tumor promotion by CHRY. In contrast, the tumor response (in terms of both papillomas and squamous cell carcinomas) was similar in Stat1−/− mice and wild-type littermates with TPA as the promoter. Maximal induction of both cyclooxygenase-2 and inducible nitric oxide synthase in epidermis following treatment with CHRY was also dependent on the presence of functional Stat1. These studies define a novel mechanism associated with skin tumor promotion by the anthrone class of tumor promoters involving upregulation of IFNγ signaling in the epidermis and downstream signaling through activated (phosphorylated) Stat1, IRF-1 and uStat1. © 2014 Wiley Periodicals, Inc.

  • Abstract 2556: Stat1 plays a major role in skin tumor promotion by Chrysarobin but not TPA
    Carcinogenesis, 2012
    Co-Authors: Ronald Bozeman, John Digiovanni
    Abstract:

    The cellular and molecular mechanisms that underlie promotion by diverse tumor promoting agents remain to be fully elucidated. Studies using Stat1 knockout (KO) mice have shown that they were highly resistant to two-stage skin carcinogenesis using Chrysarobin as the promoter. In contrast, Stat1 KO mice treated with 12-O-tetradecanoylphorbol 13-acetate (TPA) as the tumor promoter exhibited no significant differences in tumor formation. To further investigate mechanism(s) whereby Stat1 mediates skin tumor promotion by Chrysarobin Stat1 KO mice and wild-type (WT) controls were treated with the respective tumor promoters and Stat1-dependent signaling pathways were evaluated. Mice deficient in Stat1 displayed an attenuated induction of epidermal Cox-2 mRNA and protein as well as reduced PGE2 levels compared to WT controls following topical application of Chrysarobin, whereas, mice treated with TPA exhibited no significant differences in Cox-2 levels or PGE2 levels. Other results also suggest that Stat1 may regulate various cytokine/chemokines involved in the inflammatory response following Chrysarobin treatment. Preliminary experiments have also shown that Stat1 KO mice exhibit reduced induction of interferon regulatory factor-1 (IRF-1) following Chrysarobin treatment, compared to WT controls. In contrast, treatment with TPA caused no significant differences in expression of IRF-1. Collectively, these findings suggest that Chrysarobin may elicit a Stat1-dependent signaling response that is dependent on IRF-1, whereas TPA-mediated tumorigenesis is independent of this signaling pathway. These and other ongoing studies aimed at characterizing the role of Stat1 and IRF-1 signaling in Chrysarobin-mediated tumor promotion will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2556. doi:1538-7445.AM2012-2556

  • Abstract 2730: Role of Stat1 in skin tumor promotion
    Carcinogenesis, 2011
    Co-Authors: Ronald Bozeman, John Digiovanni, Erika L. Abel
    Abstract:

    Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Inflammation is a key component of cancer development in many tissues. Emerging clinical observations support the idea of a strong association of chronic inflammation and cancer. The JAK-STAT pathway is one of the major signaling pathways involved in modulating both pro- and anti-inflammatory responses. Aberrant expression of STATs has been reported in multiple human cancers and in animal models of tumorigenesis. Previous work performed in our lab demonstrated a role for Stat1 in mediating the promotion stage of epithelial multi-stage carcinogenesis in mouse skin when Chrysarobin was used as the promoting agent. To further investigate the role of Stat1 in Chrysarobin-mediated skin tumor promotion, Stat1 knockout (KO) mice and wild-type controls were treated with Chrysarobin and the inflammatory response was assessed. Stat1 deficiency caused a reduction in the dermal inflammatory response following a single topical application of Chrysarobin. In this regard, Stat1 KO mice had reduced dermal immune cell influx following Chrysarobin treatment. In particular, Stat1 KO mice exhibited reduced influx of macrophages following a single application. Other results also suggest that Stat1 may regulate various cytokine/chemokines involved in the inflammatory response following Chrysarobin treatment. Mice deficient in Stat1 displayed an attenuated induction of Cox-2 mRNA and protein compared to wild-type controls following a single application of Chrysarobin (200 nmol per mouse). This latter data suggest that Stat1 may be involved in the regulation of Cox-2 in keratinocytes. Collectively, these findings suggest that Stat1 may contribute to Chrysarobin-mediated skin tumor promotion by regulating, in part, levels of Cox-2, PGE2 and ultimately skin inflammation. These and other ongoing studies aimed at identifying the mechanistic basis for the role of Stat1 in Chrysarobin-mediated tumor promotion will be presented. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2730. doi:10.1158/1538-7445.AM2011-2730

  • Abstract 2480: Role of Stat1 in epithelial carcinogenesis
    Carcinogenesis, 2010
    Co-Authors: Ronald Bozeman, Erika L. Abel, John Digiovanni
    Abstract:

    Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Aberrant expression and/ or activity of STATs 1, 3, and 5 have been reported in multiple human cancers as well as in murine models of tumorigenesis. Previous work performed in our lab demonstrated a critical role for Stat3 in mediating the initiation and promotion stages of epithelial multi-stage carcinogenesis in mouse skin. In light of these findings, we have begun investigating the role of other STATs, particularly Stat1, in multistage skin carcinogenesis using both wild-type and Stat1 knockout (KO) mice. Western blot analyses revealed that topical application of the skin tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and Chrysarobin induced phosphorylation of Stat1 in mouse epidermis. In addition, following treatment with Chrysarobin, the level of total Stat1 protein was also dramatically elevated. To further investigate the role of Stat1 during epithelial carcinogenesis, Stat1 KO mice and wild-type littermates were initiated with 25 nmol DMBA and promoted with either 6.8 nmol TPA or 220 nmol Chrysarobin. No significant differences were observed in either tumor incidence or multiplicity when TPA was used as the promoting agent, suggesting that Stat1 does not play a significant role in TPA-mediated skin tumor promotion. In contrast, Stat1 KO mice exhibited a dramatic reduction in both tumor multiplicity and incidence as compared to wild-type littermates when Chrysarobin was used as the promoting agent. Additionally, following topical treatment with Chrysarobin, Stat1 KO mice had a reduced epidermal proliferative response. To further investigate the impact of Stat1 deletion on Chrysarobin-induced tumor promotion, Stat1 KO mice and wild-type controls were treated topically with Chrysarobin and the inflammatory response was assessed. Stat1 KO mice displayed a significant reduction in Cox-2 induction compared to wild-type controls. Preliminary findings also showed that Stat1 KO mice have reduced immune cell influx following Chrysarobin treatment. To investigate the potential role of reactive oxygen species (ROS) in the effects of Chrysarobin on Stat1 activation, the dorsal skin of FVB mice were pre-treated topically with the anti-oxidants ascorbyl palmitate and α-tocopherol acetate. Topical application of α-tocopherol acetate significantly attenuated the epidermal proliferative response and Stat1 activation suggesting that Chrysarobin-mediated generation of ROS may play a role in its effects on Stat1 during tumor promotion. Additional studies are underway to further determine the mechanistic basis for the role of Stat1 in Chrysarobin-mediated tumor promotion. Supported by NIH grant CA 76520. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2480.