Christina Hackl

Up-Regulation of Krüppel-Like Factor 5 in Pancreatic Cancer Is Promoted by Interleukin-1β Signaling and Hypoxia-Inducible Factor-1α

Krüppel-like factor 5 (KLF5) is a transcription factor involved in cell transformation, proliferation, and carcinogenesis that can be up-regulated by RAS mutations. However, controversy persists as to whether it functions as a tumor suppressor or as an oncogene. Because KRAS is frequently mutated in pancreatic cancer, we investigated the regulation of KLF5 in this cancer entity. Our results show that KLF5 is overexpressed in pancreatic cancer cells and exceeds KLF5 expression of KRAS-mutated colon cancer cells. Surprisingly, inhibition of B-Raf/C-Raf or MAPK/Erk did not reduce KLF5 levels, suggesting that KLF5 expression is not promoted by KRAS-Raf-MEK-Erk signaling in pancreatic cancer. This finding is in striking contrast to reports on MEK-Erk–mediated KLF5 induction in colon cancer cells. Moreover, KLF5 expression levels neither correlated with the mutational status of KRAS nor with MEK phosphorylation in pancreatic cancer cells. Importantly, KLF5 was significantly up-regulated by interleukin (IL)-1β or hypoxia. The IL-1 β–mediated induction of KLF5 was diminished by blocking the p38 pathway. In addition, blocking IL-1R reduced the constitutive KLF5 expression, suggesting an autocrine activation loop. Moreover, KLF5 coimmunoprecipitated with hypoxia-inducible factor-1α (HIF-1α) and HIF-1αsiRNA reduced constitutive KLF5. Similarly, KLF5siRNA reduced the expression of the HIF-1α target gene GLUT-1. Furthermore, KLF5 expression was significantly elevated by high cell density, by anchorage-independent cell growth, and in tumor spheroids. Down-regulation of KLF5 by RNAi reduced the expression of the target genes, survivin, and platelet-derived growth factor-A. In conclusion, overexpression of KLF5 in human pancreatic cancer cells is not mediated by KRAS/Raf/MAPK/Erk signaling, but involves the IL-1β/IL-1R system, p38, and the transcription factor HIF-1α. (Mol Cancer Res 2009;7(8):1390–8)

Activating transcription factor-3 (ATF3) functions as a tumor suppressor in colon cancer and is up-regulated upon heat-shock protein 90 (Hsp90) inhibition.

BackgroundActivating transcription factor-3 (ATF3) is involved in the complex process of cellular stress response. However, its exact role in cancer is discussed controversially because both tumor suppressive and oncogenic effects have been described. Here we followed-up on our previous observation that inhibition of Hsp90 may increase ATF3 expression and sought to determine the role of ATF3 in colon cancer.MethodsRegulation of ATF3 was determined in cancer cells using signaling inhibitors and a heat-shock protein-90 (Hsp90) antagonist. Human HCT116 cancer cells were stably transfected with an ATF3-shRNA or a luciferase-shRNA expression plasmid and alterations in cell motility were assessed in migration assays. The impact of ATF3 down-regulation on cancer growth and metastasis were investigated in a subcutaneous tumor model, a model of hepatic tumor growth and in a model of peritoneal carcinomatosis. Human colon cancer tissues were analyzed for ATF3 expression.ResultsThe results show that therapeutic Hsp90 inhibition substantially up-regulates the expression of ATF3 in various cancer cells, including colon, gastric and pancreatic cancer. This effect was evident both in vitro and in vivo. RNAi mediated knock-down of ATF3 in HCT116 colon cancer cells significantly increased cancer cell migration in vitro. Moreover, in xenogenic mouse models, ATF3 knock-down promoted subcutaneous tumor growth and hepatic metastasis, as well as peritoneal carcinomatosis. Importantly, ATF3 expression was lower in human colon cancer specimens, as compared to corresponding normal surrounding tissues, suggesting that ATF3 may represent a down-regulated tumor suppressor in colon cancer.ConclusionIn conclusion, ATF3 down-regulation in colon cancer promotes tumor growth and metastasis. Considering that blocking Hsp90 induces ATF3 expression, Hsp90 inhibition may represent a valid strategy to treat metastatic colon cancer by up-regulating this anti-metastatic transcription factor.

Dual targeting of Raf and VEGF receptor 2 reduces growth and metastasis of pancreatic cancer through direct effects on tumor cells, endothelial cells, and pericytes

The Ras/Raf/MEK pathway represents an important oncogenic signaling pathway in gastrointestinal malignancies, including pancreatic cancer. Although activating B-Raf mutations are infrequent in pancreatic cancer, we hypothesized that targeting Raf could be valuable for therapy of this cancer entity. Moreover, as vascular endothelial growth factor receptor 2 (VEGFR2) is involved in tumor angiogenesis, we sought to investigate the effects of dual inhibition of Raf and VEGFR2 on pancreatic tumor growth, vascularization, and metastasis. Effects of a Raf/VEGFR2 inhibitor (NVP-AAL881) on pancreatic cancer cells, endothelial cells, and vascular smooth muscle cells were determined by Western blotting, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide analysis, and migration assays, respectively. Changes in the expression of VEGF-A or survivin were investigated by ELISA and/or real-time PCR. The growth-inhibitory effects of Raf/VEGFR2 inhibition were additionally evaluated in orthotopic tumor models. Results showed that various Raf isoforms were activated in pancreatic cancer cells and NVP-AAL881 diminished the activation of MEK, Akt, Erk, and also STAT3. Moreover, dual inhibition of Raf/VEGFR2 significantly reduced VEGF expression and impaired cancer cell migration. Importantly, besides blocking VEGF-induced Erk and SAPK phosphorylation in endothelial cells, the Raf inhibitor diminished STAT3 phosphorylation, independent of a VEGFR2 blockade, and reduced the expression of survivin. In addition, cell proliferation and migration of both endothelial cells and vascular smooth muscle cells were significantly reduced. In vivo, blocking Raf/VEGFR2 significantly inhibited orthotopic tumor growth and vascularization and reduced cancer metastasis. In conclusion, blocking Raf exerts growth-inhibitory effects on pancreatic tumor cells, endothelial cells, and pericytes and elicits antiangiogenic properties. Dual targeting of Raf and VEGFR2 appears to be a valid strategy for therapy of pancreatic cancer. [Mol Cancer Ther 2008;7(11):3509–18]

Implication of RICTOR in the mTOR inhibitor-mediated induction of insulin-like growth factor-I receptor (IGF-IR) and human epidermal growth factor receptor-2 (Her2) expression in gastrointestinal cancer cells.

Inhibition of mTORC1 with the mTOR inhibitor rapamycin may lead to an induction of Akt phosphorylation in cancer cells via mTORC2 activation. Using gastric and pancreatic cancer cells, we further investigated this paradoxical signaling response and found that rapamycin additionally up-regulates both IGF-IR and Her2 expression. Using RNAi for down-regulating RICTOR, this induction of receptor kinase expression was identified to be mediated via an mTORC2-induced Akt activation. Moreover, mTORC2 inhibition reduced the phosphorylation of GSK-3 and NF-kappaB, and significantly impaired cancer cell motility. In conclusion, inhibition of mTORC2 may abrogate unfavorable signaling effects of mTOR inhibitors, hence providing a novel rationale for therapy.

A population-based analysis on the rate and surgical management of colorectal liver metastases in Southern Germany.

PurposeEarly detection and multidisciplinary treatment of colorectal liver metastases (CLM), preferably resection, can significantly prolong the survival of colorectal cancer patients. The purpose of this study was to analyze the incidence, management and long-term clinical outcome of CLM patients using data from a regional German tumour registry.MethodsWe conducted a retrospective analysis of 884 patients diagnosed with colorectal adenocarcinoma in the year 2002 and documented in a regional tumor registry in Southern Germany.ResultsTwo hundred thirty-six patients (26.7%) had or developed CLM, 132 patients (14.9%) had synchronous CLM and 104 patients (11.8%) developed metachronous CLM. At diagnosis of CLM, 86 patients (36.4%) had 3 or less documented lesions, 6 patients (2.5%) had 4 to 6 lesions and 89 patients (37.7%) showed multiple, diffuse metastases; for 55 patients (23.3%), the number of lesions was not specified. CLM patients (19.1%) (5.1% of all patients) underwent liver resection; a higher resection rate (28.3%) was observed in a subgroup of patients treated in two academic centres. Patients without CLM had a significantly better 5-year survival rate than patients with liver metastases (65.5% versus 16.3%). CLM patients with up to 3 liver metastases (i.e., potentially resectable) who underwent liver resection (n=34) showed a significantly higher 5-year survival than non-resected (n=52) patients (40% versus 5%).ConclusionsThe present study is the first population-based analysis of the surgical management and outcome of CLM in Southern Germany. The percentage of liver resections was lower than expected, particularly for patients with three or less metastases. The present data suggest that relevant undertreatment of CLM patients may occur which may have a negative impact on survival.

IRAK-M Expression in Tumor Cells Supports Colorectal Cancer Progression through Reduction of Antimicrobial Defense and Stabilization of STAT3

Colorectal cancer (CRC) is associated with loss of epithelial barrier integrity, which facilitates the interaction of the immunological microenvironment with the luminal microbiome, eliciting tumor-supportive inflammation. An important regulator of intestinal inflammatory responses is IRAK-M, a negative regulator of TLR signaling. Here we investigate the compartment-specific impact of IRAK-M on colorectal carcinogenesis using a mouse model. We demonstrate that IRAK-M is expressed in tumor cells due to combined TLR and Wnt activation. Tumor cell-intrinsic IRAK-M is responsible for regulation of microbial colonization of tumors and STAT3 protein stability in tumor cells, leading to tumor cell proliferation. IRAK-M expression in human CRCs is associated with poor prognosis. These results suggest that IRAK-M may be a potential therapeutic target for CRC treatment.

Current developments in pediatric liver transplantation

In 1953, the pioneer of human orthotopic liver transplantation (LT), Thomas E Starzl, was the first to attempt an orthotopic liver transplant into a 3 years old patient suffering from biliary atresia. Thus, the first LT in humans was attempted in a disease, which, up until today, remains the main indication for pediatric LT (pLT). During the last sixty years, refinements in diagnostics and surgical technique, the introduction of new immunosuppressive medications and improvements in perioperative pediatric care have established LT as routine procedure for childhood acute and chronic liver failure as well as inherited liver diseases. In contrast to adult recipients, pLT differs greatly in indications for LT, allocation practice, surgical technique, immunosuppression and post-operative life-long aftercare. Many aspects are focus of ongoing preclinical and clinical research. The present review gives an overview of current developments and the clinical outcome of pLT, with a focus on alternatives to full-size deceased-donor organ transplantation.

Liver transplantation for malignancy:current treatment strategies and future perspectives

In 1967, Starzl et al performed the first successful liver transplantation for a patient diagnosed with hepatoblastoma. In the following, liver transplantation was considered ideal for complete tumor resection and potential cure from primary hepatic malignancies. Several reports of liver transplantation for primary and metastatic liver cancer however showed disappointing results and the strategy was soon dismissed. In 1996, Mazzaferro et al introduced the Milan criteria, offering liver transplantation to patients diagnosed with limited hepatocellular carcinoma. Since then, liver transplantation for malignant disease is an ongoing subject of preclinical and clinical research. In this context, several aspects must be considered: (1) Given the shortage of deceased-donor organs, long-term overall and disease free survival should be comparable with results obtained in patients transplanted for non-malignant disease; (2) In this regard, living-donor liver transplantation may in selected patients help to solve the ethical dilemma of optimal individual patient treatment vs organ allocation justice; and (3) Ongoing research focusing on perioperative therapy and anti-proliferative immunosuppressive regimens may further reduce tumor recurrence in patients transplanted for malignant disease and thus improve overall survival. The present review gives an overview of current indications and future perspectives of liver transplantation for malignant disease.

Inhibition of mTORC2 component RICTOR impairs tumor growth in pancreatic cancer models

Mammalian Target of Rapamycin complex 2 (mTORC2) and its regulatory component Rapamycin-insensitive companion of mTOR (RICTOR) are increasingly recognized as important players in human cancer development and progression. However, the role of RICTOR in human pancreatic ductal adenocarcinoma (PDAC) is unclear so far. Here, we sought to analyze the effects of RICTOR inhibition in human pancreatic cancer cell lines in vitro and in vivo. Furthermore, RICTOR expression was determined in human PDAC samples. Results demonstrate that depletion of RICTOR with siRNA (transient knock-down) or shRNA (stable knock-down) has an inhibitory effect on tumor growth in vitro. Moreover, RICTOR inhibition led to impaired phosphorylation/activity of AGC kinases (AKT, SGK1). Interestingly, hypoxia-induced expression of hypoxia-induced factor-1α (HIF-1α) was diminished and secretion of vascular-endothelial growth factor-A (VEGF-A) was impaired upon targeting RICTOR. Stable RICTOR knock-down led to significant inhibition of tumor growth in subcutaneous and orthotopic tumor models which was accompanied by significant reduction of tumor cell proliferation. Finally, immunohistochemical analyses of 85 human PDAC samples revealed significantly poorer survival in patients with higher RICTOR expression. In conclusion, these findings provide first evidence for mTORC2/RICTOR as an attractive novel target for treatment of human PDAC.

Liver surgery in cirrhosis and portal hypertension

The prevalence of hepatic cirrhosis in Europe and the United States, currently 250 patients per 100000 inhabitants, is steadily increasing. Thus, we observe a significant increase in patients with cirrhosis and portal hypertension needing liver resections for primary or metastatic lesions. However, extended liver resections in patients with underlying hepatic cirrhosis and portal hypertension still represent a medical challenge in regard to perioperative morbidity, surgical management and postoperative outcome. The Barcelona Clinic Liver Cancer classification recommends to restrict curative liver resections for hepatocellular carcinoma in cirrhotic patients to early tumor stages in patients with Child A cirrhosis not showing portal hypertension. However, during the last two decades, relevant improvements in preoperative diagnostic, perioperative hepatologic and intensive care management as well as in surgical techniques during hepatic resections have rendered even extended liver resections in higher-degree cirrhotic patients with portal hypertension possible. However, there are few standard indications for hepatic resections in cirrhotic patients and risk stratifications have to be performed in an interdisciplinary setting for each individual patient. We here review the indications, the preoperative risk-stratifications, the morbidity and the mortality of extended resections for primary and metastatic lesions in cirrhotic livers. Furthermore, we provide a review of literature on perioperative management in cirrhotic patients needing extrahepatic abdominal surgery and an overview of surgical options in the treatment of hepatic cirrhosis.