Pancreas morphogenesis and homeostasis depends on tightly regulated Zeb1 levels in epithelial cells.

The pancreas is comprised of exocrine and endocrine compartments releasing digestive enzymes into the duodenum and regulating blood glucose levels by insulin and glucagon release. Tissue homeostasis is depending on transcription factor networks, involving Ptf1α, Ngn3, Nkx6.1, and Sox9, which are already activated during organogenesis. However, proper organ function is challenged by diets of high sugar and fat content, increasing the risk of type 2 diabetes and other disorders. A detailed understanding of processes that are important for homeostasis and are impaired during type 2 diabetes is lacking. Here, we show that Zeb1-a transcription factor known for its pivotal role in epithelial-mesenchymal transition, cell plasticity, and metastasis in cancer-is expressed at low levels in epithelial cells of the pancreas and is crucial for organogenesis and pancreas function. Loss of Zeb1 in these cells result in an increase of islet mass, impaired glucose tolerance, and sensitizes to develop liver and pancreas steatosis during diabetes and obesity. Interestingly, moderate overexpression of Zeb1 results in severe pancreas agenesis and lethality after birth, due to islet insufficiency and lack of acinar structures. We show that Zeb1 induction interferes with proper differentiation, cell survival, and proliferation during pancreas formation, due to deregulated expression of endocrine-specific transcription factors. In summary, our analysis suggests a novel role of Zeb1 for homeostasis in epithelial cells that is indispensable for pancreas morphogenesis and proper organ function involving a tight regulation of Zeb1 expression.

The EMT-activator Zeb1 is a key factor for cell plasticity and promotes metastasis in pancreatic cancer.

Metastasis is the major cause of cancer-associated death. Partial activation of the epithelial-to-mesenchymal transition program (partial EMT) was considered a major driver of tumour progression from initiation to metastasis. However, the role of EMT in promoting metastasis has recently been challenged, in particular concerning effects of the Snail and Twist EMT transcription factors (EMT-TFs) in pancreatic cancer. In contrast, we show here that in the same pancreatic cancer model, driven by Pdx1-cre-mediated activation of mutant Kras and p53 (KPC model), the EMT-TF Zeb1 is a key factor for the formation of precursor lesions, invasion and notably metastasis. Depletion of Zeb1 suppresses stemness, colonization capacity and in particular phenotypic/metabolic plasticity of tumour cells, probably causing the observed in vivo effects. Accordingly, we conclude that different EMT-TFs have complementary subfunctions in driving pancreatic tumour metastasis. Therapeutic strategies should consider these potential specificities of EMT-TFs to target these factors simultaneously.

Generation and characterization of mice for conditional inactivation of Zeb1.

The multizinc finger containing transcription factor ZEB1 plays crucial roles during various aspects of mammalian development and tumorigenesis. Best studied in human tumors, ZEB1 is activating the embryo-derived program of epithelial-mesenchymal transition (EMT). The aberrant activation of EMT confers an invasive metastasizing phenotype with acquisition of stem cell properties and resistance to radio- and chemotherapy. Although ZEB1 has very important functions in tumor progression, not much is known about its role in physiological contexts and during development and homeostasis. We describe the generation of Zeb1flox/flox mice carrying a targeted mutation for conditional Zeb1 gene inactivation and show that homozygous Zeb1-depletion in the germline results in a phenotype similar to the conventional Zeb1 knockout.

The choroid plexus may be an underestimated site of tumor invasion to the brain: an in vitro study using neuroblastoma cell lines.

BACKGROUND: The central nervous system (CNS) is protected by several barriers, including the blood-brain (BBB) and blood-cerebrospinal fluid (BCSFB) barriers. Understanding how cancer cells circumvent these protective barriers to invade the CNS is of crucial interest, since brain metastasis during cancer is often a fatal event in both children and adults. However, whereas much effort has been invested in elucidating the process of tumor cell transmigration across the BBB, the role of the BCSFB might still be underestimated considering the significant number of meningeal cancer involvement. Our work aimed to investigate the transmigration of neuroblastoma cells across the BCSFB in vitro. METHODS: We used an inverted model of the human BCSFB presenting proper restrictive features including adequate expression of tight-junction proteins, low permeability to integrity markers, and high trans-epithelial electrical resistance. Two different human neuroblastoma cell lines (SH-SY5Y and IMR-32) were used to study the transmigration process by fluorescent microscopy analysis. RESULTS: The results show that neuroblastoma cells are able to actively cross the tight human in vitro BCSFB model within 24 h. The presence and transmigration of neuroblastoma cancer cells did not affect the barrier integrity within the duration of the experiment. CONCLUSIONS: In conclusion, we presume that the choroid plexus might be an underestimated site of CNS invasion, since neuroblastoma cell lines are able to actively cross a choroid plexus epithelial cell layer. Further studies are warranted to elucidate the molecular mechanisms of tumor cell transmigration in vitro and in vivo.