The human Fyn-related kinase (FRK) is a member of subfamily of Src-related kinases family. FRK is 54 kDa non-receptor tyrosine kinase protein composed of 505 amino acids. FRK consists of three functional domains: Src homology 3 (SH3), SH2 and kinase domain, as well as a putative tyrosine kinase regulator at the C-terminus. FRK has a conserved auto-regulatory tyrosine residue within its kinase domain. It has been reported that FRK is repressed in about 30 % of human breast cancer samples. Over-expression of FRK in breast cancer cells of the mammary gland was shown to suppress cell growth by interacting, phosphorylating and stabilizing the tumor suppressor PTEN, thus inhibiting AKT/PI3K signaling. Although it has been suggested that FRK is a tumor suppressor gene, the effects of activated FRK on cell proliferation, migration and invasion are unclear. Likewise, the signaling pathways regulated by the activation of FRK have not been yet fully characterized. We hypothesize that the activation of FRK is essential for the regulation of its cellular functions. Mutation of the C-terminal auto-regulatory tyrosine 497 to phenylalanine (FRK-Y497F) resulted in the constitutive activation of FRK. We generated stable cell lines expressing either the FRK wild type (FRK-WT) or FRK-Y497F from triple negative breast cancer MDA-MB-231 cells. The introduction of FRK-Y497F in MDA-MB-231 cells significantly suppressed their proliferation, migration, invasiveness and colony formation as compared to cells that expressed the FRK-WT gene. Over-expression of either FRK-WT or FRK-Y497F in MDA-MB-231 cells inhibited the phosphorylation of AKT, STAT3, JNK and P38 MAPK as compared to either the MDA-MB-231 parental cells or those that were transfected with the empty vector. Our results suggested that FRK represses cell proliferation, migration, invasiveness and colony formation at least in part by the inhibiting the activation of AKT/PI3K, JAK-STAT and MAPK signaling pathways.

Lung cancer is the common cause of cancer death. STAT3 (signal transducer and activator of transcription 3) has been reported to be an oncogenic transcription factor and high expression of STAT3 is associated with lung cancer progression. RECK (reversion-inducing cysteine-rich protein with Kazal motifs) is a tumor suppressor gene and a membrane-anchored glycoprotein that reduces the matrix metalloproteinases (MMPs)-induced destruction of extra-cellular matrix (ECM) and tumor metastasis. RECK also inhibits tumor angiogenesis. We have previously elucidated the transcriptional regulation of RECK gene. Recently, microRNAs (miRs) are shown to be key players in gene regulation and cancer progression. In this study, we try to elucidate whether ovexpression of STAT3 can affect microRNA expression to regulate RECK via post-transcriptional modulation. miR-17-92a cluster is a well-known oncomir which is highly expressed in lung cancer tissue. We find that miR-92a, a member of miR-17-92a cluster can target RECK 3¡¦UTR. In addition, our data suggest that STAT3 regulates the expression of miR-92a and inhibition of STAT3 can decrease miR-92a expression. Furthermore, overexpression of miR-92a can decrease RECK protein level. While knockdown of miR-92a expression in STAT3-overexpressing cell lines can restore RECK protein level, and reduce invasion and migration. Results of this study suggest that STAT3 up-regulates miR-92a to inhibit RECK expression and promote lung cancer metastasis.

No description available.

A Artrite reumatoide é uma doença autoimune que acomete cerca de 1% da população mundial adulta, sendo caracterizada pela participação de linfócitos Th17 no seu desenvolvimento. Na busca por novos alvos terapêuticos e pela compreensão da fisiopatologia, se destacam os inflamassomas que são plataformas proteicas, caracterizados pela produção de citocinas pró-inflamatórias por células do sistema imune inato. De forma interessante, foi demonstrado que linfócitos T CD4 também expressam alguns sensores dessas plataformas, como o Nlrp12. Adicionalmente, este sensor é responsável pela modulação negativa do NF-?B, demonstrando outra característica atípica em relação aos outros inflamassomas. Nesse sentido, foi avaliada a participação do Nlrp12 no desenvolvimento da artrite experimental e na diferenciação linfócitos Th17. Foi verificado nesse estudo que o Nlrp12 é regulado positivamente durante o desenvolvimento da artrite experimental, sendo um modulador negativo desse processo. Isso se deve a uma redução na resposta inflamatória inata do modelo e pela modulação negativa na resposta Th17. Nesse sentido, o controle da resposta Th17 e o desenvolvimento da artrite experimental ocorre por um mecanismo dependente da fosforilação do fator de transcrição Stat3, que é crítico na diferenciação de linfócitos Th17. Desta forma, este estudo demonstra uma nova função para o sensor Nlrp12 no desenvolvimento da artrite experimental, por modular a resposta imune adaptativa de forma direta nos linfócitos T CD4 / Rheumatoid Arthritis is an autoimmune disease that occurs in approximately 1% of the adult population worldwide, with critical role of Th17 cells in your development. In the search for new therapeutic targets and the understanding of the pathophysiology, there are inflammasomes which are protein platforms, characterized through pro-inflammatory cytokines production by innate immune system cells. Interestingly, it was demonstrated that CD4 T cells express some inflammasome sensors, as Nlrp12. Additionally, this sensor is responsible for downregulation of NF-?B, showing another atypical feature in relation to other inflammasomes. Thereby, it was evaluated the role of Nlrp12 on experimental arthritis development and Th17 differentiation. It was found in this study that Nlrp12 is upregulated during experimental arthritis development, working as negative regulator of this process. Thus, Nlrp12 downregulates innate inflammatory response from experimental model and Th17 response. Therefore, experimental arthritis development and Th17 differentiation control occurs in a Stat3 phosphorylation dependente-manne, which is a critical transcription factor on Th17 differentiation. Thus, this study demonstrates a new function for Nlrp12 on experimental arthritis development, by directly to modulate adaptive immune response in CD4 cells

A Artrite reumatoide é uma doença autoimune que acomete cerca de 1% da população mundial adulta, sendo caracterizada pela participação de linfócitos Th17 no seu desenvolvimento. Na busca por novos alvos terapêuticos e pela compreensão da fisiopatologia, se destacam os inflamassomas que são plataformas proteicas, caracterizados pela produção de citocinas pró-inflamatórias por células do sistema imune inato. De forma interessante, foi demonstrado que linfócitos T CD4 também expressam alguns sensores dessas plataformas, como o Nlrp12. Adicionalmente, este sensor é responsável pela modulação negativa do NF-?B, demonstrando outra característica atípica em relação aos outros inflamassomas. Nesse sentido, foi avaliada a participação do Nlrp12 no desenvolvimento da artrite experimental e na diferenciação linfócitos Th17. Foi verificado nesse estudo que o Nlrp12 é regulado positivamente durante o desenvolvimento da artrite experimental, sendo um modulador negativo desse processo. Isso se deve a uma redução na resposta inflamatória inata do modelo e pela modulação negativa na resposta Th17. Nesse sentido, o controle da resposta Th17 e o desenvolvimento da artrite experimental ocorre por um mecanismo dependente da fosforilação do fator de transcrição Stat3, que é crítico na diferenciação de linfócitos Th17. Desta forma, este estudo demonstra uma nova função para o sensor Nlrp12 no desenvolvimento da artrite experimental, por modular a resposta imune adaptativa de forma direta nos linfócitos T CD4 / Rheumatoid Arthritis is an autoimmune disease that occurs in approximately 1% of the adult population worldwide, with critical role of Th17 cells in your development. In the search for new therapeutic targets and the understanding of the pathophysiology, there are inflammasomes which are protein platforms, characterized through pro-inflammatory cytokines production by innate immune system cells. Interestingly, it was demonstrated that CD4 T cells express some inflammasome sensors, as Nlrp12. Additionally, this sensor is responsible for downregulation of NF-?B, showing another atypical feature in relation to other inflammasomes. Thereby, it was evaluated the role of Nlrp12 on experimental arthritis development and Th17 differentiation. It was found in this study that Nlrp12 is upregulated during experimental arthritis development, working as negative regulator of this process. Thus, Nlrp12 downregulates innate inflammatory response from experimental model and Th17 response. Therefore, experimental arthritis development and Th17 differentiation control occurs in a Stat3 phosphorylation dependente-manne, which is a critical transcription factor on Th17 differentiation. Thus, this study demonstrates a new function for Nlrp12 on experimental arthritis development, by directly to modulate adaptive immune response in CD4 cells

No description available.

Les gliomes sont des tumeurs du système nerveux central. Leur plus haut degré de malignité est le glioblastome (GBM), le plus fréquent des cancers du cerveau. Les patients atteints de GBM sont d’abord opérés (si possible) puis traités par la radiothérapie avec témozolomide concomitant et adjuvant. Ce traitement n’est cependant pas curatif, en partie en raison d’une radiorésistance primaire élevée des cellules de GBM. La voie de signalisation JAK/STAT3 (Janus Kinase/Signal Transducer and Activator of Transcription 3) semble contribuer à la gravité des GBM. STAT3 est une protéine intracellulaire de transduction du signal. Elle est activée par phosphorylation de ses résidus tyrosine 705 (pSTAT3-Y705) et sérine 727 (pSTAT3-S727). L’activation de la tyrosine 705 se produit en aval du signal induit par la liaison de la cytokine interleukine 6 (IL-6) à son complexe récepteur transmembranaire gp130-IL-6Rα. Les mécanismes d’activation de la sérine 727 sont moins bien caractérisés. Le rôle de l’activation de STAT3 dans la radiorésistance des GBM a été ici étudié. Une évaluation du niveau basal de pSTAT3-Y705, pSTAT3-S727 et de la radiorésistance intrinsèque a été faite sur un panel de 15 lignées de GBM humain. L’activation de STAT3 dans les lignées cellulaires de gliomes a été évaluée par western blot et la radiorésistance par la survie cellulaire à l’irradiation. En plus de la description de l’état basal d’activation de STAT3 dans les lignées cellulaires de gliomes, cette étude a mis en évidence pour la première fois, une corrélation de pSTAT3-S727 avec la radiorésistance intrinsèque des GBM. Une stratégie de blocage pharmacologique de STAT3 nous a permis d’identifier le Gö6976 comme inhibant la phosphorylation Y705 de STAT3 dans les cellules de GBM. Celui-ci s’est avéré inhiber aussi la phosphorylation S727 mais seulement dans les lignées de GBM pSTAT3-Y705 négatives. Le traitement par le Gö6976 ralentit la croissance des cellules de GBM, indépendamment du statut d’activation de STAT3. De façon intéressante, le Gö6976 a montré un pouvoir radiosensibilisant très significatif sur les lignées pSTAT3-Y705 négatives, ce qui est concordant avec la baisse du niveau de pSTAT3-S727. La pertinence de ces résultats est confortée par un marquage immunohistochimique sur des échantillons cliniques de GBM, montrant la présence à des degrés variables de pSTAT3-S727 dans toutes les cellules cancéreuses de tous les patients. En parallèle, une étude in vitro des fonctions de pSTAT3-S727 utilisant des dominants positif et négatif est en cours. En somme, nous avons démontré que pSTAT3-S727 participe à la radiorésistance intrinsèque et que pSTAT3-Y705 est un marqueur prédictif négatif de la réponse des cellules de GBM au Gö6976 à la fois comme inhibiteur de pSTAT3-S727 et radiosensibilisant. L’ensemble de nos résultats conforte l’intérêt d’une inhibition spécifique de pSTAT3-S727 pour radiosensibiliser les GBM et ainsi améliorer le traitement des patients. / Gliomas are tumors of the central nervous system. The highest degree in glioma malignancy is Glioblastoma (GBM) that is the most frequent of the brain cancers. GBM patients are treated by surgery at first (if it is possible), followed by radiotherapy and concomitant and adjuvant temozolomide. However, this treatment is not curative in part because GBM cells display an outstanding primary radioresistance. The JAK/STAT3 (Janus Kinase/Signal Transducer and Activator of Transcription 3) signaling pathway seems to be involved in the GBM aggressiveness. STAT3 is an intracellular signal transducer protein. It is activated by phosphorylation on its tyrosine 705 (pSTAT3-Y705) and serine 727 (pSTAT3-S727) residues. The tyrosine 705 activation is produced downstream the signal induced by the binding of interleukine-6 (IL-6) cytokine to its gp130-IL-6Rα transmembrane receptor complex. The mechanisms of the serine 727 phosphorylation are less characterized. The role of STAT3 activation in the radioresistance of GBM was studied here. Basal levels of pSTAT3-Y705, pSTAT3-S727 and intrinsic radioresistance were evaluateded in a panel of 15 GBM cel lines. Activation of STAT3 in the glioma cell lines was assessed by western blotting and radioresistance through cell surviving fraction to irradiation. In addition to the description of the basal activation of STAT3 in the glioma cell lines, this study evidenced, for the first time, a correlation between pSTAT3-S727 and GBM intrinsic radioresistance. Using a pharmacological inhibition strategy, we identified Gö6976 as a chemical blocking Y705 phosphorylation of STAT3 in GBM cells. Gö6976 also inhibited pSTAT3-S727 but only in the pSTAT3-Y705-negative cell lines. Treating GBM cell with Gö6976 slowed their growth regardless of STAT3 activation status. Interestingly, Gö6976 showed a highly significant radiosensitizing effect on pSTAT3-Y705-negative cell lines that was consistent with the down-modulation of pSTAT3-S727. The relevance of these results is strengthened by immunohistochemical assay performed of GBM clinical samples that showed a variable level of pSTAT3-S727 positive staining in all tumor cells of all the patients. Furthermore, we are currently running on an in vitro study of the pSTAT3-S727 biological function by the mean of STAT3 dominant positive and dominant negative proteins. In summary, we showed that pSTAT3-S727 is involved in the intrinsic radioresistance and that pSTAT3-Y705 is a negative predicting marker of GBM cell response to Gö6976 as both a pSTAT3-S727 inhibitor and a radiosensitizer. Altogether, our results strengthen the clinical relevance of a specific inhibition of pSTAT3-S727 to radiosensitize GBM and then improve the patient treatment.

Cachexia is a highly complex syndrome identified by metabolic, hormonal and cytokine-related abnormalities, but can be shortly characterized as accelerated skeletal muscle and adipose tissue loss in the context of a chronic inflammatory response. Cachexia is a debilitating complication of several diseases such as AIDS, sepsis, diabetes, renal failure, burn injury and cancer. Cachexia is responsible for 25-30% of cancer patient deaths. One of the most obvious outcomes of cancer cachexia is the redistribution of the total protein content, namely the depletion of skeletal muscle protein levels and increase in the acute phase response protein levels as a response to tissue injury. Although the plasticity of muscle mass and utility of skeletal muscle as a protein source are known facts, there have not been many studies concerning the mechanism of conversion of skeletal muscle proteins to other protein forms, for which the organism has greater need. IL-6 and activation of the acute phase response have been linked to cancer cachexia. However, IL-6 is generally not thought to signal directly on skeletal muscle and to date no studies have manipulated the STAT3 pathway for regulating skeletal muscle mass. Our data demonstrate direct action of IL-6 on activation of the STAT3 and acute phase response pathway at the skeletal muscle. In addition, our observations that STAT3 is broadly activated in cachexia and that STAT3 activation is sufficient and necesssary to induce muscle wasting are also novel. Thus, these studies define a new pathway leading to muscle wasting, which can be a potential target for reversing muscle wasting in cancer cachexia. Successful inhibition of skeletal muscle wasting and other metabolic derangements of cachexia will increase quality of life and survival of a significant fraction of cancer patients.

Signal Transducer and Activator of Transcription 3, Stat3, has been associated with cytokine-induced proliferation, anti-apoptosis and neoplastic transformation, while constitutively active Stat3 has been found in many human tumors. Stat3 activation by the Src oncoprotein leads to specific gene regulation and the Stat3 mediated signaling pathway is one of the critical signaling pathways involved in Src oncogenesis. Our laboratory demonstrated that engagement of cadherins, which are a class of cell-cell adhesion molecules, can activate Stat3, even in the absence of direct cell to cell contact. Interestingly, a significant increase in total Rac1 and Cdc42 protein levels triggered by cadherin engagement, and an increase in Rac1 and Cdc42 activity, which led to Stat3 activation by a mechanism involving gp130, a common subunit of the IL-6 family of cytokines, was also observed. To investigate the role of gp130 in vSrc transformation, we knocked down gp130 in vSrc transformed cells and found a decrease in the levels of phosphorylated Stat3, the rate of cell migration, rate of cell proliferation and the anchorage-independent growth. It was also previously demonstrated that vSrc had a negative effect on the function of cadherins. Surprisingly, however, despite the fact that vSrc may reduce cadherin adhesion, previous results in our lab showed that cell density still caused a significant increase in Stat3 activity in vSrc transformed cells. Moreover, Stat3 downregulation induced apoptosis in transformed cells which was more pronounced at high cell densities. This may reflect an increased need for Stat3 activity at high densities, possibly to overcome apoptosis, which raised the question of the actual role of cadherins in the density-mediated activation of Stat3 in such cells. The expression of cadherin-11, a type II cell adhesion molecule, is associated with invasive breast cancer and many studies suggest that it may play a significant role in facilitating tumor cell invasion and the formation of metastatic tumors. Since Src and its family members participate in many aspects of tumor progression and metastasis, it was interesting to see if Src needed cadherin-11 for neoplastic transformation. To this effect, when we knocked down cadherin-11 in Balb/c3T3 cells, we observed a significant reduction in levels of phosphorylated Stat3-ptyr705 which was also observed when vSrc was expressed in them. Moreover, expressing vSrc in cells in which cadherin-11 was knocked down also decreased the anchorage –independent growth and increased apoptosis indicating that cadherin-11 is needed for transformation and survival respectively, in vSrc transformed cells. Our results thus demonstrate that cadherin-11 may be a good target for the selective elimination of cells expressing Src and presumably other oncogenes as well. Stat3 activation by cadherins is so potent and important that tumor cell death can be enhanced by cadherin inhibition. In our experiments, the inhibition of cadherin-11 induced apoptosis in Src expressing cells, while the normal cells were not affected. Elucidation of the functions and regulation of cadherin-11 may enhance our understanding of the roles of cadherins in invasive cancer and may provide future targets for therapy. Through our work, the cadherin/IL-6 pathway may emerge as a crucial Stat3 activator in vSrc expressing cells. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2011-11-27 18:54:05.777

Master of Science / Biochemistry and Molecular Biophysics / Zhilong Yang / Poxvirus infections continue to threaten human health despite the eradication of smallpox, which was one of the most lethal infectious diseases in human history. Our objectives were to identify the host cell components/functions that are important for poxvirus infection and to gain insights into the molecular mechanism of poxvirus replication, ultimately guiding novel anti-viral development. Using vaccinia virus, the prototype poxvirus, we screened inhibitors of viral replication from over 3,000 chemical compounds, most of which have known cellular targets. This screening revealed numerous JAK/STAT3 inhibitors that could inhibit the replication of vaccinia virus. We further used multiple inhibitors of the JAK/STAT3 pathway and tested their effects on the replication of vaccinia virus in multiple primary and transformed cells through reporter assay and viral infectious particles measurement. The JAK/STAT3 inhibitors being tested were: SC144, an inhibitor of the interleukin 6(IL-6), a receptor of the JAK/STAT3 signaling pathway, AZ960 (a JAK2 inhibitor), Stattic and niclosamide (inhibitors of STAT3). Overall, our data indicate the JAK/STAT3 inhibitors could repressed vaccinia virus replication in multiple cell types, suggesting that the JAK/STAT3 signaling pathway is required for the efficient replication of vaccinia virus. Moreover, we observed that STAT3 was enriched in the cell nucleus, although the phosphorylation level of STAT3 was downregulated in vaccinia virus-infected cells during the early stages of infection. This study demonstrates an important role of the JAK/STAT3 signaling pathway in the replication of vaccinia virus, providing a possible novel direction by which to intervene in poxvirus infection and related diseases.