The dual role of C/EBPδ in cancer.

CCAAT/Enhancer-Binding Protein delta (C/EBPδ) is a transcription factor involved in differentiation and inflammation. While sparsely expressed in adult tissues, aberrant expression of C/EBPδ has been associated with different cancers. Initially, re-expression of C/EBPδ in cell cultures limited tumor cell proliferation, assigning it a tumor suppressor role. However, opposing observations were made in pre-clinical models and patients, suggesting that C/EBPδ not only mediates cell proliferation but dictates a broader spectrum of tumorigenesis-related effects. It is now widely accepted that C/EBPδ contributes to an inflammatory, tumor-promoting microenvironment, aids hypoxia adaption and contributes to the recruitment of blood vessels for improved nutrient supply to tumor cells and facilitated extravasation. This review summarizes the work published on this transcription factor in the field of cancer over the past decade. It points out areas in which a consensus on C/EBPδ's role appears to emerge and seek to explain seemingly contradictory results.

C/EBP-Family Redundancy Determines Patient Survival and Lymph Node Involvement in PDAC.

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a poor clinical prognosis and unsatisfactory treatment options. We previously found that the transcription factor CCAAT/Enhancer-Binding Protein Delta (C/EBPδ) is lowly expressed in PDAC compared to healthy pancreas duct cells, and that patient survival and lymph node involvement in PDAC is correlated with the expression of C/EBPδ in primary tumor cells. C/EBPδ shares a homologous DNA-binding sequence with other C/EBP-proteins, leading to the presumption that other C/EBP-family members might act redundantly and compensate for the loss of C/EBPδ. This implies that patient stratification could be improved when expression levels of multiple C/EBP-family members are considered simultaneously. In this study, we assessed whether the quantification of C/EBPß or C/EBPγ in addition to that of C/EBPδ might improve the prediction of patient survival and lymph node involvement using a cohort of 68 resectable PDAC patients. Using Kaplan-Meier analyses of patient groups with different C/EBP-expression levels, we found that both C/EBPß and C/EBPγ can partially compensate for low C/EBPδ and improve patient survival. Further, we uncovered C/EBPß as a novel predictor of a decreased likelihood of lymph node involvement in PDAC, and found that C/EBPß and C/EBPδ can compensate for the lack of each other in order to reduce the risk of lymph node involvement. C/EBPγ, on the other hand, appears to promote lymph node involvement in the absence of C/EBPδ. Altogether, our results show that the redundancy of C/EBP-family members might have a profound influence on clinical prognoses and that the expression of both C/EPBß and C/EBPγ should be taken into account when dichotomizing patients according to C/EBPδ expression.

C/EBPδ Suppresses Motility-Associated Gene Signatures and Reduces PDAC Cell Migration.

Pancreatic Ductal Adenocarcinoma (PDAC) is among the most aggressive human cancers and occurs globally at an increasing incidence. Metastases are the primary cause of cancer-related death and, in the majority of cases, PDAC is accompanied by metastatic disease at the time of diagnosis, making it a particularly lethal cancer. Regrettably, to date, no curative treatment has been developed for patients with metastatic disease, resulting in a 5-year survival rate of only 11%. We previously found that the protein expression of the transcription factor CCAAT/Enhancer-Binding Protein Delta (C/EBPδ) negatively correlates with lymph node involvement in PDAC patients. To better comprehend the etiology of metastatic PDAC, we explored the role of C/EBPδ at different steps of the metastatic cascade, using established in vitro models. We found that C/EBPδ has a major impact on cell motility, an important prerequisite for tumor cells to leave the primary tumor and to reach distant sites. Our data suggest that C/EBPδ induces downstream pathways that modulate actin cytoskeleton dynamics to reduce cell migration and to induce a more epithelial-like cellular phenotype. Understanding the mechanisms dictating epithelial and mesenchymal features holds great promise for improving the treatment of PDAC.

Pre-operative knee extensor and flexor torque after secondary ACL rupture: a comparative retrospective analysis.

BACKGROUND: Secondary anterior cruciate ligament (ACL) ruptures are a relevant clinical concern after surgical treatment of a primary ACL rupture. However, there is a lack of scientific evidence related to the role of muscle strength prior to revision surgery in a second ACL rupture. The aim of this study was to assess differences in knee extensor and flexor strength in patients before primary and secondary ACL reconstruction compared to healthy controls. METHODS: In total, n = 69 age, weight and sex matched individuals were included in the study: n = 23 patients with isolated primary ACL rupture, n = 23 with secondary ACL rupture, and n = 23 matched healthy controls. Maximal isokinetic knee extension and flexion torque normalized to body mass was assessed for both legs. RESULTS: For patients with secondary ACL ruptures, torques were reduced in the non-injured (extension: 1.94 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.25 Nm/kg vs. 1.59 Nm/kg, p < 0.05) and the injured leg (extension: 1.70 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.14 Nm/kg vs. 1.59 Nm/kg, p < 0.05) compared to healthy controls. For patients with a primary ACL rupture torques were reduced in the non-injured (extension: 1.92 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.24 Nm/kg vs. 1.59 Nm/kg, p < 0.05) and the injured leg (extension: 1.38 Nm/kg vs. 2.46 Nm/kg, p < 0.05, flexion: 1.01 Nm/kg vs. 1.59 Nm/kg, p < 0.05) compared to healthy controls. There were no differences between patients with primary and secondary ruptures, except of the knee extension on the injured leg showing higher values after a secondary ACL rupture (1.38 Nm/kg vs. 1.70 Nm/kg, p < 0.05). CONCLUSIONS: The findings indicate that maximal knee torques were significantly reduced in patients with primary and secondary ACL ruptures before surgical reconstruction for the non-injured and injured leg as compared to healthy controls. Further investigations are needed to assess strength abilities before and after a second revision within a prospective design.

Non-Tumor CCAAT/Enhancer-Binding Protein Delta Potentiates Tumor Cell Extravasation and Pancreatic Cancer Metastasis Formation.

CCAAT/enhancer-binding protein delta (C/EBPδ) is a transcription factor involved in apoptosis and proliferation, which is downregulated in pancreatic ductal adenocarcinoma (PDAC) cells. Loss of nuclear C/EBPδ in PDAC cells is associated with decreased patient survival and pro-tumorigenic properties in vitro. Interestingly however, next to C/EBPδ expression in tumor cells, C/EBPδ is also expressed by cells constituting the tumor microenvironment and by cells comprising the organs and parenchyma. However, the functional relevance of systemic C/EBPδ in carcinogenesis remains elusive. Here, we consequently assessed the potential importance of C/EBPδ in somatic tissues by utilizing an orthotopic pancreatic cancer model. In doing so, we show that genetic ablation of C/EBPδ does not significantly affect primary tumor growth but has a strong impact on metastases; wildtype mice developed metastases at multiple sites, whilst this was not the case in C/EBPδ-/- mice. In line with reduced metastasis formation in C/EBPδ-/- mice, C/EBPδ-deficiency also limited tumor cell dissemination in a specific extravasation model. Tumor cell extravasation was dependent on the platelet-activating factor receptor (PAFR) as a PAFR antagonist inhibited tumor cell extravasation in wildtype mice but not in C/EBPδ-/- mice. Overall, we show that systemic C/EBPδ facilitates pancreatic cancer metastasis, and we suggest this is due to C/EBPδ-PAFR-dependent tumor cell extravasation.

CCAAT/Enhancer-Binding Protein Delta (C/EBPδ): A Previously Unrecognized Tumor Suppressor that Limits the Oncogenic Potential of Pancreatic Ductal Adenocarcinoma Cells.

CCAAT/enhancer-binding protein δ (C/EBPδ) is a transcription factor involved in growth arrest and differentiation, which has consequently been suggested to harbor tumor suppressive activities. However, C/EBPδ over-expression correlates with poor prognosis in glioblastoma and promotes genomic instability in cervical cancer, hinting at an oncogenic role of C/EBPδ in these contexts. Here, we explore the role of C/EBPδ in pancreatic cancer. We determined C/EBPδ expression in biopsies from pancreatic cancer patients using public gene-expression datasets and in-house tissue microarrays. We found that C/EBPδ is highly expressed in healthy pancreatic ductal cells but lost in pancreatic ductal adenocarcinoma. Furthermore, loss of C/EBPδ correlated with increased lymph node involvement and shorter overall survival in pancreatic ductal adenocarcinoma patients. In accordance with this, in vitro experiments showed reduced clonogenic capacity and proliferation of pancreatic ductal adenocarcinoma cells following C/EBPδ re-expression, concurrent with decreased sphere formation capacity in soft agar assays. We thus report a previously unrecognized but important tumor suppressor role of C/EBPδ in pancreatic ductal adenocarcinoma. This is of particular interest since only few tumor suppressors have been identified in the context of pancreatic cancer. Moreover, our findings suggest that restoration of C/EBPδ activity could hold therapeutic value in pancreatic ductal adenocarcinoma, although the latter claim needs to be substantiated in future studies.

Apical constriction is necessary for crypt formation in small intestinal organoids.

Small intestinal organoids have become an important tool to study crypt homeostasis, cell fate dynamics and tissue biomechanics. Yet, the mechanisms that drive the budding of crypts from the smooth organoid epithelium remain incompletely understood. Locally enhanced proliferation has been suggested to induce tissue buckling and crypt initiation. Here we report that changes in cell morphology play a crucial role in crypt formation. Crypt formation is preceded by local epithelial thickening, apicobasal elongation, and apical narrowing, resulting in a wedge-like cell-shape, followed by apical evagination and crypt outgrowth. Myosin II activity is found to coincide with apical constriction of cells, while inhibition of myosin suppresses apical constriction and bud formation. The data suggest that myosin-driven apical constriction is a key driving force of bud initiation in small intestinal organoids.