STAT3 controls matrix metalloproteinase-1 expression in colon carcinoma cells by both direct and AP-1-mediated interaction with the MMP-1 promoter.

Aberrant activation of STAT3 in colorectal carcinoma (CRC) tissue is correlated with elevated expression of matrix metalloproteinase-1 (MMP-1). We analyzed transcriptional regulation of the human MMP-1 promoter in CRC cells by tyrosine phosphorylated (pY-) STAT3. One of six putative STAT binding elements within a 4.3 kb MMP-1 trancriptional promoter fragment showed a particular high affinity for STAT3 in vitro. However, the most profound regulatory influence on MMP-1 promoter activity resides in a proximal region relative to the transcriptional start, bearing a pair of putative binding sites for STAT3 and AP-1. Mutational analysis of the combined STAT3/AP-1 recognition element revealed that the integrity of the STAT3 binding site is necessary, but not sufficient for both DNA interaction and transcriptional regulation by activated STAT3. Instead, the adjacent AP-1 site was essential for pY-STAT3-mediated transcription on the MMP-1 promoter. DNA-protein binding assays provided strong evidence for complex formation of STAT3 and c-Jun governed by protein-protein contacts. We observed striking coincidence for concerted aberrant activation of both STAT3 and AP-1 in human colon cancer specimens. This finding supports the notion that the combination of inappropriate STAT3 and AP-1 activities drives elevated MMP-1 expression and tissue invasion in colorectal cancer and is of clinical relevance.

Minimally-invasive temporary gastric stimulation: A pilot study to predict the outcome of electronic gastric stimulation with the Enterra™ system.

INTRODUCTION: Gastroparesis (GP) is defined as delayed gastric emptying (GE) without any obstruction of the pylorus. It can be divided into idiopathic, diabetic, post surgical and rare causes. Electronic gastric stimulation (EGS) - Enterra Medtronic™ - is a part of GP therapy. Although its positive impact has been reported in open label trials, randomized controlled trials failed in demonstrating a positive outcome. The aim of this pilot study was to establish a reliable prediction for permanent gastric stimulation. PATIENTS AND PROCEDURE: 6 female patients underwent laparoscopic implantation of 2 temporary electrodes. The Enterra™ system was connected and taped to the skin. Baseline and postoperative gastroparesis cardinal symptom index (GCSI), a validated index for GP therapy, was assessed. Response to EGS was defined as a 50% decrease of baseline GCSI. RESULTS: 4 of 6 patients responded to temporary EGS. 3 of 4 responders underwent permanent implantation. 1 non-responder received a permanent Enterra™ at another institution. After a median follow up time of 9months the responder group GCSI remained low, whereas the non-responder GCSI had increased. Moreover, the health care system was saved € 30,678.03 by this test stimulation concept. CONCLUSION: Laparoscopic implantation of a temporary EGS system predicts the outcome of permanent gastric stimulation and is cost-saving.

Persistent STAT3 activation in colon cancer is associated with enhanced cell proliferation and tumor growth.

Colorectal carcinoma (CRC) is a major cause of morbidity and mortality in Western countries. It has so far been molecularly defined mainly by alterations of the Wnt pathway. We show here for the first time that aberrant activities of the signal transducer and activator of transcription STAT3 actively contribute to this malignancy and, thus, are a potential therapeutic target for CRC. Constitutive STAT3 activity was found to be abundant in dedifferentiated cancer cells and infiltrating lymphocytes of CRC samples, but not in non-neoplastic colon epithelium. Cell lines derived from malignant colorectal tumors lost persistent STAT3 activity in culture. However, implantation of colon carcinoma cells into nude mice resulted in restoration of STAT3 activity, suggesting a role of an extracellular stimulus within the tumor microenvironment as a trigger for STAT activation. STAT3 activity in CRC cells triggered through interleukin-6 or through a constitutively active STAT3 mutant promoted cancer cell multiplication, whereas STAT3 inhibition through a dominant-negative variant impaired IL-6-driven proliferation. Blockade of STAT3 activation in CRC-derived xenograft tumors slowed down their development, arguing for a contribution of STAT3 to colorectal tumor growth.

Leukemia inhibitory factor triggers activation of signal transducer and activator of transcription 3, proliferation, invasiveness, and altered protease expression in choriocarcinoma cells.

Extravillous trophoblast cells resemble cancer cells with regard to their intrinsic invasiveness. They invade decidual tissue, but, unlike tumor cells, shut down their invasive properties, when they become inappropriate. Stimuli involved in the modulation of invasion, as well as their underlying signaling mechanisms require further clarification. We were especially interested in discovering signals capable of stimulating invasion in otherwise low-invasive cells involved in reproduction. Using the choriocarcinoma cell line Jeg-3 as a model, we have addressed the potential role of cytokine/growth factor-driven activation of signal transducer and activator of transcription 3 (STAT3) in this process. Jeg-3 cells were treated with various factors known to induce trophoblast proliferation, differentiation, migration, or invasiveness (insulin-like-growth-factor-II (IGF-II), hepatocyte growth factor (HGF), interleukin-6 (IL-6), and leukemia inhibitory factor (LIF)). Only LIF elicited strong tyrosine phosphorylation and specific DNA-binding activity of STAT3. It induced a significant acceleration of cell proliferation and promoted the capability of Jeg-3 cells to invade into an artificial extracellular matrix. Moreover, LIF influenced the expression pattern of proteases and protease inhibitors with potential relevance for invasiveness (downregulation of mRNA for tissue inhibitor of metalloproteinase 1 (TIMP-1) and upregulation of mRNA for caspase-4). In conjunction with earlier work, in which we found that STAT3 DNA-binding activity was increased in invasive cells (choriocarcinoma, first trimester trophoblasts) and absent in non-invasive cells (term trophoblasts), these findings suggest a connection between LIF-driven STAT3 activity and invasiveness of choriocarcinoma and trophoblast cells.

Signal transducer and activator of transcription 3 activation promotes invasive growth of colon carcinomas through matrix metalloproteinase induction.

Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in colorectal carcinomas (CRCs). Here, we define the relationship between STAT3 function and the malignant properties of colon carcinoma cells. Elevated activation of STAT3 enhances invasive growth of the CRC cell lines. To address mechanisms through which STAT3 influences invasiveness, the protease mRNA expression pattern of CRC biopsies was analyzed and correlated with the STAT3 activity status. These studies revealed a striking coincidence of STAT3 activation and strong expression of matrix metalloproteinases MMP-1, -3, -7, and -9. Immunohistological examination of CRC tumor specimens showed a clear colocalization of MMP-1 and activated STAT3. Experimentally induced STAT3 activity in CRC cell lines enhanced both the level of MMP-1 mRNA and secreted MMP-1 enzymatic activity. A direct connection of STAT3 activity and transcription from the MMP-1 promoter was shown by reporter gene experiments. Moreover, high-affinity binding of STAT3 to STAT recognition elements in both the MMP-1 and MMP-3 promoter was demonstrated. Xenograft tumors arising from implantation of CRC cells into nude mice showed simultaneous appearance and colocalization of p-Y-STAT3 and MMP-1 expression. Our results link aberrant activity of STAT3 in CRC to malignant tumor progression through upregulated expression of MMPs.

Evidence for a correlation between trophoblast invasiveness and STAT3 activity.

PROBLEM: Extravillous trophoblast cells are capable of invading decidual tissue during early pregnancy. This property is reminiscent of cancer cells. The invasiveness of trophoblasts, however, extends only to a well-regulated limit. Signal transduction processes underlying this phenomenon are as yet poorly characterized. Many factors involved in trophoblast invasiveness are known to trigger intracellular signaling cascades in other cell types that ultimately lead to the activation of signal transducers and activators of transcription (STATs). STAT3 activity was recently found related to the malignant phenotype of different tumor cells and potentially contributes to their invasive properties. METHOD OF STUDY: We investigated the status of STAT3 activity in ex vivo trophoblast cells from first trimester and term placentae employing an electrophoretic mobility shift assay (EMSA) and compared it with that of a highly malignant choriocarcinoma cell line. RESULTS: Specific DNA binding activity of two STAT3 variants (STAT3alpha and beta) was observed in immature trophoblasts and appeared to be lost in term placentae. The malignant phenotype of choriocarcinoma cells coincides with a high degree of STAT3 activity. CONCLUSION: These results suggest a connection between STAT3 activity and trophoblast invasiveness.