Purpose Signal Transducers and Activators of Transcription (STATs) activate transcription in response to numerous cytokines, controlling proliferation, gene expression and apoptosis. Aberrant activation of STAT proteins, particularly STAT-3, is implicated in the pathogenesis of many cancers, including Globlastoma Multiforme (GBM), by promoting cell cycle progression, stimulating angiogenesis, and impairing tumor immune surveillance. Little is known about the endogenous STAT inhibitors, the Protein Inhibitors of Activated STATs (PIAS) proteins, in human malignancies. The objective of this study was to examine the expression of STAT-3 and its negative regulator, PIAS3, in human tissue samples from control and GBM brains. Experimental Design Control and GBM human tissues were analyzed by immunoblotting and immunohistochemistry to determine the activation status of STAT-3 and expression of the PIAS3 protein. The functional consequence of PIAS3 inhibition by siRNA or PIAS3 over-expression in GBM cells was determined by examining cell proliferation, STAT-3 transcriptional activity and STAT-3 target gene expression. This was accomplished using 3H-TdR incorporation, STAT-3 dominant-negative constructs, RT-PCR and immunoblotting. Results and Conclusions STAT-3 activation, as assessed by tyrosine and serine phosphorylation, was elevated in GBM tissue compared to control tissue. Interestingly, we observed expression of PIAS3 in control tissue, while PIAS3 protein expression in GBM tissue was greatly reduced. Inhibition of PIAS3 resulted in enhanced glioblastoma cellular proliferation. Conversely, PIAS3 over-expression inhibited STAT-3 transcriptional activity, expression of STAT-3 regulated genes, and cell proliferation. We propose that the loss of PIAS3 in GBM contributes to enhanced STAT-3 transcriptional activity and subsequent cell proliferation.
Glioblastoma is the most common and severe primary brain tumor in adults.
Progression of melanoma is dependent on cross-talk between tumor cells and the adjacent microenvironment. The thrombin receptor, Protease Activated Receptor-1 (PAR-1) plays a key role in exerting this function during melanoma progression. PAR-1 and its activating factors, which are expressed on tumor cells and the surrounding stroma, induce not only coagulation, but also cell signaling which promotes the metastatic phenotype. Several adhesion molecules, cytokines, growth factors and proteases have recently been identified as downstream targets of PAR-1 and have been shown to modulate interactions between tumor cells and the microenvironment in the process of melanoma growth and metastasis. Inhibition of these interactions by targeting PAR-1 could be utilized as a potential therapeutic modality for melanoma patients.
CD5 activates CK2, a serine/threonine kinase that constitutively associates with the CK2-binding domain at the end of its cytoplasmic tail. To determine the physiological significance of CD5-dependent CK2 activation in T-cells we generated a knock-in mouse that expresses a CD5 protein containing a microdeletion with selective inability to interact with CK2 (CD5ΔCK2BD). The levels of CD5 on developing and mature T-cell populations from CD5ΔCK2BD mice and CD5WT mice were similar. The thymus of CD5ΔCK2BD mice contained fewer double positive (DP) thymocytes than that of both CD5WT and CD5KO mice, though the numbers of all other immature and mature T-cell populations were unaltered. CD5ΔCK2BD T-cells hypoproliferated and exhibited enhanced AICD when stimulated with anti-CD3 or cognate peptide in comparison to CD5WT T-cells. We also found that functional CD5-dependent CK2 signaling was necessary for efficient differentiation of naïve CD4+ T-cells into Th2 and Th17 cells, but not Th1 cells. We previously showed that experimental autoimmune encephalomyelitis (EAE) in CD5KO mice was less severe and delayed in onset than in CD5WT mice. Remarkably, CD5ΔCK2BD mice recapitulated both EAE severity and disease onset of CD5KO mice. Increasing the immunization dose of myelin oligodendrocyte (MOG35-55) peptide, a model that mimics high dose tolerance, led to decreased severity of EAE in CD5 WT mice but not in CD5KO or CD5ΔCK2BD mice. This property was recapitulated in in vitro re-stimulation assays. These results demonstrate that CD5-CK2 signaling sets the threshold for T-cell responsiveness and it is necessary for efficient generation of Th2 and Th17 cells.
Potential treatments for ovarian cancers that have become resistant to standard chemotherapies include modulators of tumor cell survival, such as endothelin receptor (ETR) antagonist. We investigated the therapeutic efficacy of the dual ETR antagonist, macitentan, on human ovarian cancer cells, SKOV3ip1 and IGROV1, growing orthotopically in nude mice. Mice with established disease were treated with vehicle (control), paclitaxel (weekly, intraperitoneal injections), macitentan (daily oral administrations), or a combination of paclitaxel and macitentan. Treatment with paclitaxel decreased tumor weight and volume of ascites. Combination therapy with macitentan and paclitaxel reduced tumor incidence and further reduced tumor weight and volume of ascites when compared with paclitaxel alone. Macitentan alone occasionally reduced tumor weight but alone had no effect on tumor incidence or ascites. Immunohistochemical analyses revealed that treatment with macitentan and macitentan plus paclitaxel inhibited the phosphorylation of ETRs and suppressed the survival pathways of tumor cells by decreasing the levels of pVEGFR2, pAkt, and pMAPK. The dose of macitentan necessary for inhibition of phosphorylation correlated with the dose required to increase antitumor efficacy of paclitaxel. Treatment with macitentan enhanced the cytotoxicity mediated by paclitaxel as measured by the degree of apoptosis in tumor cells and tumor-associated endothelial cells. Collectively, these results show that administration of macitentan in combination with paclitaxel prevents the progression of ovarian cancer in the peritoneal cavity of nude mice in part by inhibiting survival pathways of both tumor cells and tumor-associated endothelial cells.
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