https://repository.kulib.kyoto-u.ac.jp/dspace/bitstream/2433/159777/1/j.cell.2006.07.024.pdf

Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors.

The mediators and cellular effectors of inflammation are important constituents of the local environment of tumours. In some types of cancer, inflammatory conditions are present before a malignant change occurs. Conversely, in other types of cancer, an oncogenic change induces an inflammatory microenvironment that promotes the development of tumours. Regardless of its origin, 'smouldering' inflammation in the tumour microenvironment has many tumour-promoting effects. It aids in the proliferation and survival of malignant cells, promotes angiogenesis and metastasis, subverts adaptive immune responses, and alters responses to hormones and chemotherapeutic agents. The molecular pathways of this cancer-related inflammation are now being unravelled, resulting in the identification of new target molecules that could lead to improved diagnosis and treatment.

/pdf/cancer-related-inflammation-ltml0xgfd3.pdf

Cancer-related inflammation.

Commensurate with their roles in regulating cytokine-dependent inflammation and immunity, signal transducer and activator of transcription (STAT) proteins are central in determining whether immune responses in the tumour microenvironment promote or inhibit cancer. Persistently activated STAT3 and, to some extent, STAT5 increase tumour cell proliferation, survival and invasion while suppressing anti-tumour immunity. The persistent activation of STAT3 also mediates tumour-promoting inflammation. STAT3 has this dual role in tumour inflammation and immunity by promoting pro-oncogenic inflammatory pathways, including nuclear factor-kappaB (NF-kappaB) and interleukin-6 (IL-6)-GP130-Janus kinase (JAK) pathways, and by opposing STAT1- and NF-kappaB-mediated T helper 1 anti-tumour immune responses. Consequently, STAT3 is a promising target to redirect inflammation for cancer therapy.

/pdf/stats-in-cancer-inflammation-and-immunity-a-leading-role-for-qkgjepy6w9.pdf

STATs in cancer inflammation and immunity: a leading role for STAT3

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important family of mediators involved in the regulation of the acute-phase response to injury and infection. Besides their functions in inflammation and the immune response, these cytokines play also a crucial role in haematopoiesis, liver and neuronal regeneration, embryonal development and fertility. Dysregulation of IL-6-type cytokine signalling contributes to the onset and maintenance of several diseases, such as rheumatoid arthritis, inflammatory bowel disease, osteoporosis, multiple sclerosis and various types of cancer (e.g. multiple myeloma and prostate cancer). IL-6-type cytokines exert their action via the signal transducers gp (glycoprotein) 130, LIF receptor and OSM receptor leading to the activation of the JAK/STAT (Janus kinase/signal transducer and activator of transcription) and MAPK (mitogen-activated protein kinase) cascades. This review focuses on recent progress in the understanding of the molecular mechanisms of IL-6-type cytokine signal transduction. Emphasis is put on the termination and modulation of the JAK/STAT signalling pathway mediated by tyrosine phosphatases, the SOCS (suppressor of cytokine signalling) feedback inhibitors and PIAS (protein inhibitor of activated STAT) proteins. Also the cross-talk between the JAK/STAT pathway with other signalling cascades is discussed.

/pdf/principles-of-interleukin-il-6-type-cytokine-signalling-and-1tgjc4ttsu.pdf

Principles of interleukin (IL)-6-type cytokine signalling and its regulation.

Extracellular proteins bound to cell-surface receptors can change nuclear gene expression patterns in minutes, with far-reaching consequences for development, cell growth and homeostasis. The signal transducer and activator of transcription (STAT) proteins are among the most well studied of the latent cytoplasmic signal-dependent transcription-factor pathways. In addition to several roles in normal cell decisions, dysregulation of STAT function contributes to human disease, making the study of these proteins an important topic of current research.

/pdf/stats-transcriptional-control-and-biological-impact-4uxqiluxhc.pdf

STATs: transcriptional control and biological impact

https://www.cell.com/cell/pdf/S0092-8674(00)81959-5.pdf

Stat3 as an Oncogene

STATs are latent transcription factors that mediate cytokine- and growth factor-directed transcription. In many human cancers and transformed cell lines, Stat3 is persistently activated, and in cell culture, active Stat3 is either required for transformation, enhances transformation, or blocks apoptosis. We report that substitution of two cysteine residues within the C-terminal loop of the SH2 domain of Stat3 produces a molecule that dimerizes spontaneously, binds to DNA, and activates transcription. The Stat3-C molecule in immortalized fibroblasts causes cellular transformation scored by colony formation in soft agar and tumor formation in nude mice. Thus, the activated Stat3 molecule by itself can mediate cellular transformation and the experiments focus attention on the importance of constitutive Stat3 activation in human tumors.

ErratumStat3 as an Oncogene

Clustered specific DNA binding sites for an array of activating transcription factors, plus proteins that bend DNA to facilitate contact between bound proteins, have been documented for a number of vertebrate genes (15, 21, 25, 37). These composite structures have been called enhanceosomes (8). The T-cell receptor alpha (15) and beta-interferon (IFN-β) (25) enhanceosomes, which are assembled in response to dimerization of the T-cell receptor or double-stranded RNA, respectively, have been most thoroughly and profitably explored. Two classes of genes that are very likely dependent on enhanceosome assembly have received a great deal of attention: genes expressed in a tissue-specific manner that acquire multiple binding proteins during development, and genes that are acutely activated by an external stimulus. The latter structures hold appeal for study because they can be examined in cultured cells, in which induced synchronous changes occur in all of the cells under observation, potentially allowing the acute assembly and disassembly of proteins in an enhanceosome to be revealed.

The STAT family of transcription factors is activated by the attachment of polypeptide ligands to specific cell surface receptors and, after tyrosine phosphorylation, dimerization, and translocation to the nucleus, can participate within minutes in gene activation (11). It seems likely that STAT molecules bind DNA regions where preenhanceosome structures exist (26, 27) and that the arrival of an activated STAT dimer(s) is the key to forming an active enhanceosome (27). Such a possibility is suggested by experiments showing closely spaced binding sites for STATs and other proteins in the response elements of a number of genes (17, 24, 27, 41). Furthermore, DNase and permanganate treatment of cell nuclei revealed proteins bound at or near Stat1 sites before polypeptide treatment. This was followed by detection of STAT molecules binding close to the same DNA regions after induction (26).

One intensively studied set of physiologically important genes that are transcriptionally induced in the liver are the acute-phase response proteins, whose levels increase in the wake of bacterial infections and other toxic assaults. Interleukin-6 (IL-6) stimulation of hepatocytes, via the activation of Stat3, is thought to be the main trigger for inducing the acute-phase genes (18). One of the best-studied enhancers of acute-phase response genes is the α2-macroglobulin enhancer (20) (reviewed in reference 18), a DNA fragment 100 bases long with binding sites for both Stat3 (also called a GAS site) and for AP-1, which includes members of the Fos, Jun, and activating transcription factor (ATF) families of transcription factors. Extracts from liver nuclei of IL-6-treated animals or transformed hepatocytes (hepatoma cells) in culture indicated induction of binding to this region. Since Stat3 and c-Jun interacted in yeast two-hybrid assays and cooperated in maximizing the transcription responses of reporter genes containing the ∼100-bp enhancer (30, 31), it seemed likely that this genomic region would form a STAT-dependent enhanceosome. The experiments presented here were designed to explore this possibility and to uncover the physical basis of c-Jun–Stat3 cooperation. We report evidence, in vitro and in vivo, for an interaction between a region within c-Jun and specific sites within Stat3. Mutations in the proposed contact residues of Stat3 both reduce c-Jun–Stat3 protein interaction and disrupt the cooperation between these two proteins that is required for maximal IL-6-dependent gene activation driven by the α2-macroglobulin enhancer.

Interacting Regions in Stat3 and c-Jun That Participate in Cooperative Transcriptional Activation

The invention is directed to constitutively active Stat proteins and methods for their preparation. The modified Stat proteins have at least one cysteine residue which may interact with the corresponding cysteine residue on another modified Stat protein to form a dimer. The constitutively active Stat proteins are capable of binding to DNA and activating transcription in the absence of tyrosine phosphorylation. Cell lines expressing the modified Stat protein exhibit a transformed phenotype and are capable of forming tumors in nude mice. Methods are describe utilizing the modified Stat proteins of the invention in the absence and presence of tyrosine phosphorylation in identifying agents capable of modulating Stat protein dimerization, transcriptional activity, and cellular transformation in vitro and in vivo. The invention is also directed to polynucleotides encoding modified, constitutively active Stat proteins.

Constitutively active transcription factors and their uses for identifying modulators of activity including dysproliferative cellular changes

The present invention relates to methods for identifying interacting regions of transcription factors, and methods for identifying agents which modulate the interactions, useful for affecting gene regulation, for example, cellular transformation. A site within residues 130-154 and within residues 343-358 in Stat3 were found to interact with the transcription factor c-Jun. On c-Jun, a site within residues 105 and 334, and more particularly, between 105 and 263, interact with Stat3. These sites of interactions permit methods for identifying agents which modulate the interaction between these transcription factors to modulate gene transcription.

Melissa H. Wrzeszczynska

Papers

Stat3 as an Oncogene

ErratumStat3 as an Oncogene

Interacting Regions in Stat3 and c-Jun That Participate in Cooperative Transcriptional Activation

Constitutively active transcription factors and their uses for identifying modulators of activity including dysproliferative cellular changes

Methods for identifying modulators of transcriptional activator protein interactions