HDAC-Linked "Proliferative" miRNA Expression Pattern in Pancreatic Neuroendocrine Tumors.

Epigenetic factors are essentially involved in carcinogenesis, tumor promotion, and chemoresistance. Two epigenetic key players are miRNAs and histone deacetylases (HDACs). As previously shown by own theoretical databank analysis, the crosstalk between miRNAs and HDACs is relevant in different human chronic diseases and cancerogenic pathways. We aimed to investigate a potential connection between the expression of a well-defined subset of "proliferation-associated" miRNAs and the expression of HDACs as well as clinical parameters in pancreatic neuroendocrine tumors (pNETs). MATERIALS AND METHODS: Expression levels of miRNA132-3p, miRNA145-5p, miRNA183-5p, miRNA34a-5p, and miRNA449a in 57 pNETs resected between 1997 and 2015 were measured and linked to the immunohistochemical expression pattern of members of the four HDAC classes on human tissue microarrays. All pNET cases were clinically and pathologically characterized according to published guidelines. Correlation analysis revealed a significant association between expression of specific miRNAs and two members of the HDAC family (HDAC3 and HDAC4). Additionally, a linkage between miRNA expression and clinico-pathological parameters like grading, TNM-staging, and hormone activity was found. Moreover, overall and disease-free survival is statistically correlated with the expression of the investigated miRNAs. Overall, we demonstrated that specific miRNAs could be linked to HDAC expression in pNETs. Especially miRNA449a (associated with HDAC3/4) seems to play an important role in pNET proliferation and could be a potential prognostic factor for poor survival. These first data could help, to improve our knowledge of the complex interactions of the epigenetic drivers in pNETs for further therapeutic approaches.

Thermographic real-time-monitoring of surgical radiofrequency and microwave ablation in a perfused porcine liver model.

Radiofrequency ablation (RFA) and microwave ablation (MWA) are currently the dominant modalities to treat unresectable liver tumors. Monitoring the ablation process with b-mode-sonography is often hampered by artefacts. Furthermore, vessels may cause cooling in the adjacent tumor target (heat-sink-effect) with risk of local recurrence. The present study evaluated infrared-thermography to monitor surgical RFA/MWA and detect heat-sink-effects in real-time. RFA and MWA of perfused porcine livers was conducted at peripheral and central-vessel-adjacent locations, and monitored by real-time thermography. Ablation was measured and evaluated by gross pathology. The mean time for ablation was significantly longer in RFA compared with MWA (8 vs. 2 min). Although mean macroscopic ablation diameter was similar (RFA, 3.17 cm; MWA, 3.38 cm), RFA showed a significant heat-sink-effect compared with MWA. The surface temperature during central RFA near vessels was 1/3 lower compared with peripheral RFA (47.11±8.35°C vs. 68.72±12.70°C; P<0.001). There was no significant difference in MWA (50.52±8.35°C vs. 50.18±10.35°C; P=0.74). In conclusion, thermography is suitable to monitor the correct ablation with MWA and RFA. The results of the current study demonstrated a significant heat-sink-effect for RFA, but not MWA near vessels. MWA reaches consistent surface temperatures much faster than RFA. With further in vivo validation, thermography may be useful to ensure appropriate ablation particularly near vulnerable or vascular structures.

Comprehensive immunohistochemical analysis of histone deacetylases in pancreatic neuroendocrine tumors: HDAC5 as a predictor of poor clinical outcome.

Epigenetic factors contribute to carcinogenesis, tumor promotion, and chemoresistance. Histone deacetylases (HDACs) are epigenetic regulators that primarily cause chromatin compaction, leading to inaccessibility of promoter regions and eventually gene silencing. Many cancer entities feature overexpression of HDACs. Currently, the role of HDACs in pancreatic neuroendocrine tumors (pNETs) is unclear. We analyzed the expression patterns of all HDAC classes (classes I, IIA, IIB, III, and IV) in 5 human tissue microarrays representing 57 pNETs resected between 1997 and 2013 and corresponding control tissue. All pNET cases were characterized clinically and pathologically according to recent staging guidelines. The investigated cases included 32 (56.1%) female and 25 (43.9%) male pNET patients (total n=57, 47.4% immunohistochemically endocrine positive). Immunohistochemical profiling revealed a significant up-regulation of all HDAC classes in pNET versus control, with different levels of intensity and extensity ranging from 1.5- to >7-fold up-regulation. In addition, expression of several HDACs (HDAC1, HDAC2, HDAC5, HDAC11, and Sirt1) was significantly increased in G3 tumors. Correlation analysis showed a significant association between the protein expression of HDAC classes I, III, and IV and rate of the pHH3/Ki-67-associated mitotic and proliferation index. Furthermore, especially HDAC5 proved as a negative predictor of disease-free and overall survival in pNET patients. Overall, we demonstrate that specific members of all 4 HDAC classes are heterogeneously expressed in pNET. Moreover, expression of HDACs was associated with tumor grading, proliferation markers, and patient survival, therefore representing interesting new targets in pNET treatment.

Differential role of Hedgehog signaling in human pancreatic (patho-) physiology: An up to date review.

Since the discovery of the Hedgehog (Hh) pathway in drosophila melanogaster, our knowledge of the role of Hh in embryonic development, inflammation, and cancerogenesis in humans has dramatically increased over the last decades. This is the case especially concerning the pancreas, however, real therapeutic breakthroughs are missing until now. In general, Hh signaling is essential for pancreatic organogenesis, development, and tissue maturation. In the case of acute pancreatitis, Hh has a protective role, whereas in chronic pancreatitis, Hh interacts with pancreatic stellate cells, leading to destructive parenchym fibrosis and atrophy, as well as to irregular tissue remodeling with potency of initiating cancerogenesis. In vitro and in situ analysis of Hh in pancreatic cancer revealed that the Hh pathway participates in the development of pancreatic precursor lesions and ductal adenocarcinoma including critical interactions with the tumor microenvironment. The application of specific inhibitors of components of the Hh pathway is currently subject of ongoing clinical trials (phases 1 and 2). Furthermore, a combination of Hh pathway inhibitors and established chemotherapeutic drugs could also represent a promising therapeutic approach. In this review, we give a structured survey of the role of the Hh pathway in pancreatic development, pancreatitis, pancreatic carcinogenesis and pancreatic cancer as well as an overview of current clinical trials concerning Hh pathway inhibitors and pancreas cancer.

Back to the start: Evaluation of prognostic markers in gastrointestinal stromal tumors.

The aim of this study was to provide a standardized risk stratification model for gastrointestinal stromal tumors (GISTs) based on tumor localization, tumor size, involved lymph nodes and metastases, as well as mitotic activity and other morphological and molecular markers, in order to improve the risk evaluation scheme for recurrence, metastatic spread and survival for patients with GIST. A total of 201 cases of patients with GIST were investigated according to standardized morphological markers, including nuclear pleomorphism, tumor cell necrosis, mucosal infiltration, ulceration, skeinoid fibers and growth pattern. In addition, all cases were immunohistochemically analyzed using a tissue microarray platform for various markers of differentiation (CD34, CD44, CD117, desmin, discovered on GIST 1, platelet-derived growth factor receptor α, S-100 and smooth muscle actin) and proliferation (B-cell lymphoma 2, P16, P53, phosphohistone H3 and Ki-67). These findings were correlated by uni- and multivariable analyses with clinicopathological characteristics, including recurrence, metastasis and survival. The general clinicopathological parameters of this GIST specimen cohort were comparable to previous studies. While several parameters exhibited clear associations to each other and to the defined clinical endpoints, the multivariate analysis reduced the number of relevant prognostic variables to localization, margin status, growth pattern and hematoxylin and eosin-based mitosis/Ki-67-based proliferation of GISTs. With the exception of CD34, none of the applied markers of differentiation and proliferation were found to be independent prognostic markers in GIST and the classical risk factors of GIST remain important prognostic factors. Additionally, growth pattern may predict the risk of recurrence and metastasis in GIST patients. Additional independent molecular prognostic markers remain to be identified and validated.

Role of histone deacetylases in pancreas: Implications for pathogenesis and therapy.

In the last years, our knowledge of the pathogenesis in acute and chronic pancreatitis (AP/CP) as well as in pancreatic cancerogenesis has significantly diversified. Nevertheless, the medicinal therapeutic options are still limited and therapeutic success and patient outcome are poor. Epigenetic deregulation of gene expression is known to contribute to development and progression of AP and CP as well as of pancreatic cancer. Therefore, the selective inhibition of aberrantly active epigenetic regulators can be an effective option for future therapies. Histone deacetylases (HDACs) are enzymes that remove an acetyl group from histone tails, thereby causing chromatin compaction and repression of transcription. In this review we present an overview of the currently available literature addressing the role of HDACs in the pancreas and in pancreatic diseases. In pancreatic cancerogenesis, HDACs play a role in the important process of epithelial-mesenchymal-transition, ubiquitin-proteasome pathway and, hypoxia-inducible-factor-1-angiogenesis. Finally, we focus on HDACs as potential therapeutic targets by summarizing currently available histone deacetylase inhibitors.

Endoplasmic Reticulum Stress in Pancreatic Neuroendocrine Tumors is Linked to Clinicopathological Parameters and Possible Epigenetic Regulations.

BACKGROUND: Endoplasmic reticulum (ER) stress is a highly-conserved cellular defense mechanism in response to perturbations of ER function. The role of ER stress in pancreatic neuroendocrine tumors (pNET) still remains unclear. MATERIALS AND METHODS: We analyzed the protein expression pattern of the four key players of ER stress, (chaperone binding imunoglobluin protein (BiP), C/EBP homologous protein (CHOP), activating transcription factor 4 (ATF4) and caspase 4) as well as histone deacetylases (HDACs) by a tissue microarray (TMA) of 49 human pNET resected between 1997 and 2013 following, extensive clinicopathological characterization. RESULTS: Immunohistochemical profiling revealed a significant up-regulation of BiP, ATF4, CHOP and caspase 4 in pNET cases compared to normal controls. Correlated to clinicopathological parameters especially BiP expression could be linked to higher grading and proliferation as well as to lower survival probability. Finally, expression of ER stress markers correlated with HDAC expression in situ and pharmalogical inhibition by panobinostat significantly reduced cell viability in vitro. CONCLUSION: Up-regulation of ER stress in pNET indicates the presence and engagement of ER stress signaling in this tumor entity demonstrating another possible anticancer therapy option in pNET.

Histone deacetylation meets miRNA: epigenetics and post-transcriptional regulation in cancer and chronic diseases.

INTRODUCTION: Epigenetic regulation via DNA methylation, histone acetylation, as well as by microRNAs (miRNAs) is currently in the scientific focus due to its role in carcinogenesis and its involvement in initiation, progression and metastasis. While many target genes of DNA methylation, histone acetylation and miRNAs are known, even less information exists as to how these mechanisms cooperate and how they may regulate each other in a specific pathological context. For further development of therapeutic approaches, this review presents the current status of the crosstalk of histone acetylation and miRNAs in human carcinogenesis and chronic diseases. AREAS COVERED: This article reviews information from comprehensive PubMed searches to evaluate relevant literature with a focus on possible association between histone acetylation, miRNAs and their targets. Our analysis identified specific miRNAs which collaborate with histone deacetylases (HDACs) and cooperatively regulate several relevant target genes. EXPERT OPINION: Fourteen miRNAs could be linked to the expression of eight HDACs influencing the α-(1,6)-fucosyltransferase, polycystin-2 and the fibroblast-growth-factor 2 pathways. Focusing on the complex linkage of miRNA and HDAC expression could give deeper insights in new 'druggable' targets and might provide possible novel therapeutic approaches in future.

Hedgehog/GLI signaling activates suppressor of cytokine signaling 1 (SOCS1) in epidermal and neural tumor cells.

Sustained hedgehog (Hh) signaling mediated by the GLI transcription factors is implicated in many types of cancer. Identification of Hh/GLI target genes modulating the activity of other pathways involved in tumor development promise to open new ways for better understanding of tumor development and maintenance. Here we show that SOCS1 is a direct target of Hh/GLI signaling in human keratinocytes and medulloblastoma cells. SOCS1 is a potent inhibitor of interferon gamma (IFN-y)/STAT1 signaling. IFN-у/STAT1 signaling can induce cell cycle arrest, apoptosis and anti-tumor immunity. The transcription factors GLI1 and GLI2 activate the SOCS1 promoter, which contains five putative GLI binding sites, and GLI2 binding to the promoter was shown by chromatin immunoprecipitation. Consistent with a role of GLI in SOCS1 regulation, STAT1 phosphorylation is reduced in cells with active Hh/GLI signaling and IFN-у/STAT1 target gene activation is decreased. Furthermore, IFN-у signaling is restored by shRNA mediated knock down of SOCS1. Here, we identify SOCS1 as a novel Hh/GLI target gene, indicating a negative role of Hh/GLI pathway in IFN-y/STAT1 signaling.