Mechanisms of disease: Insights into the emerging role of signal transducers and activators of transcription in cancer.
ABSTRACT Members of the signal transducers and activators of transcription (STAT) pathway, which were originally identified as key components linking cytokine signals to transcriptional events in cells, have recently been demonstrated to have a major role in cancer. They are cytoplasmic proteins that form functional dimers with each other when activated by tyrosine phosphorylation. Activated STAT proteins translocate to the nucleus to regulate expression of genes by binding to specific elements within gene promoters. Constitutive activation of the STAT family members Stat3 and Stat5, and/or loss of Stat1 signaling, is found in a large group of diverse tumors. Increasing evidence demonstrates that STAT proteins can regulate many pathways important in oncogenesis including cell-cycle progression, apoptosis, tumor angiogenesis, tumor-cell invasion and metastasis, and tumor-cell evasion of the immune system. Based on these findings, a growing effort is underway to target STAT proteins directly and indirectly for cancer therapy. This review will highlight STAT signaling pathways, STAT target genes involved in cancer, evidence for STAT activation in human cancers, and therapeutic strategies to target STAT molecules for anticancer therapy.
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ABSTRACT: The aim of the present study was to investigate the expression of proteins associated with the sustained activation of the signal transducer and activator of transcription (STAT)-3 pathway during diethylnitrosamine (DEN)-induced rat liver carcinogenesis. DEN was intermittently administered to rats to induce liver cancer, and light and electron microscopy were used to observe the morphological changes in the liver during carcinogenesis. Western blotting and quantitative polymerase chain reaction (qPCR) were used to detect the expression of STAT-3, phosphorylated (p)-STAT-3, matrix metalloproteinase (MMP)-10, vascular endothelial growth factor (VEGF), kinase insert domain receptor (KDR), hypoxia inducible factor (HIF)-1α, basic fibroblast growth factor (bFGF) and interleukin (IL)-10, in order to investigate the association between STAT-3 and p-STAT-3 expression and MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10. The western blotting and qPCR results revealed that the expression of STAT-3, p-STAT-3, MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10 proteins gradually increased during carcinogenesis. Furthermore, the STAT-3 and p-STAT-3 levels were found to positively correlate with MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10 protein expression. During DEN-induced rat liver carcinogenesis, STAT-3 protein continually activated MMP-10, VEGF, KDR, HIF-1α, bFGF and IL-10, and its expression was found to positively correlate with the expression of these proteins.Oncology letters 08/2014; 8(2):608-614. · 0.24 Impact Factor
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ABSTRACT: Inflammatory condition is the consequence of defensive mechanism of immune system against viral and bacterial infection, tissue injury, UV radiation, stress and etc. Persistently acute inflammation leads to chronic phase which is characterized by production of pro-inflammatory mediators from T cells. These molecules (e.g. IL-6, TNF-α, IL-1β and IL-17) are mostly pleiotropic cytokines involved in multiple signaling cascades. NF-κB, STAT3, and HIF-1α are the major engaged pathways directing to several downstream targets associating with tumorigenesis and inflammation. Carcinogenesis processes such as DNA mutation/damage, proliferation, angiogenesis, apoptosis, and invasion are implicated to inflammation. Clearly there is a closely association between cancer and inflammation reported as “Seven Hallmark of Cancer”. The elucidation of relationship between inflammation and cancer and their interaction may result in effective therapy and prevention. Gastric cancer is one of the main cancer involved in complex correlation of inflammation and cancer. Inflammation in gastric epithelium could trigger cellular transformation and promote invasion by inducing immune responses and utilizing signaling cascades. Gastric tumor microenvironment has inverse association by providing cytokines and inflammatory mediators. This closely relationship facilitates gastric tumor development and the induction of chronic inflammation in tumor microenvironment. The current review will focus on describing the possible and critical ways in which inflammation and cancer are linked together with specific view to gastric cancer and inflammation. Finally, it introduces some putative treatment generally used in this way in order to direct more attention for further exploration.Res Mol Med. 2014; 2 (2). 06/2014; 2(2):1-15.
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ABSTRACT: STAT3 mediates cytokine and growth factor receptor signalling, becoming transcriptionally active upon tyrosine 705 phosphorylation (Y-P). Constitutively Y-P STAT3 is observed in many tumors that become addicted to its activity, and STAT3 transcriptional activation is required for tumor transformation downstream of several oncogenes. We have recently demonstrated that constitutively active STAT3 drives a metabolic switch towards aerobic glycolysis through the transcriptional induction of Hif-1α and the down-regulation of mitochondrial activity, in both MEF cells expressing constitutively active STAT3 (Stat3C/C) and STAT3-addicted tumor cells. This novel metabolic function is likely involved in mediating pre-oncogenic features in the primary Stat3C/C MEFs such as resistance to apoptosis and senescence and rapid proliferation. Moreover, it strongly contributes to the ability of primary Stat3C/C MEFs to undergo malignant transformation upon spontaneous immortalization, a feature that may explain the well known causative link between STAT3 constitutive activity and tumor transformation under chronic inflammatory conditions. Taken together with the recently uncovered role of STAT3 in regulating energy metabolism from within the mitochondrion when phosphorylated on Ser 727, these data place STAT3 at the center of a hub regulating energy metabolism under different conditions, in most cases promoting cell survival, proliferation and malignant transformation even though with distinct mechanisms.Cancers. 01/2014; 6(3):1579-1596.