Glioblastoma remains one of the most lethal types of cancer, and is the most common brain tumour in adults. In particular, tumour recurrence after surgical resection and radiation invariably occurs regardless of aggressive chemotherapy. Here, we provide evidence that the transcription factor ZEB1 (zinc finger E-box binding homeobox 1) exerts simultaneous influence over invasion, chemoresistance and tumourigenesis in glioblastoma. ZEB1 is preferentially expressed in invasive glioblastoma cells, where the ZEB1-miR-200 feedback loop interconnects these processes through the downstream effectors ROBO1, c-MYB and MGMT. Moreover, ZEB1 expression in glioblastoma patients is predictive of shorter survival and poor Temozolomide response. Our findings indicate that this regulator of epithelial-mesenchymal transition orchestrates key features of cancer stem cells in malignant glioma and identify ROBO1, OLIG2, CD133 and MGMT as novel targets of the ZEB1 pathway. Thus, ZEB1 is an important candidate molecule for glioblastoma recurrence, a marker of invasive tumour cells and a potential therapeutic target, along with its downstream effectors.Glioblastoma have a poor prognosis, mainly due to infiltrating and therapy resistant cells leading to cancer recurrence. Here, tumor formation, invasion and resistance are not independent but intertwined processes regulated by the EMT activator ZEB1.

bcl-2 gene expression is induced by 17␤-estradiol (E2) in T47D and MCF-7 human breast cancer cells, and the mechanism of E2 responsiveness was further investigated by analysis of the bcl-2 gene promoter. The ؊1602 to ؊1534 distal region (bcl-2j) of the promoter was E2-responsive; however, in gel mobility shift assays, the estrogen receptor ␣ (ER ␣ ) did not bind [ 32 P]bcl-2j, whereas Sp1 protein formed a retarded band complex. Further analysis demonstrated that the upstream region (؊1603 to ؊1579) of the bcl-2 gene promoter contained two GC/GA-rich sites at ؊1601 (5-GGGCTGG-3) and ؊1588 (3-GGAGGG-5) that bound Sp1 protein. Subsequent studies confirmed that transactivation by E2 was dependent on ER ␣ /Sp1 interactions with both GCrich sites, and this was confirmed by in vitro footprinting. In contrast, a 21-base pair E2-responsive downstream region (؊1578 to ؊1534) did not bind Sp1 or ER ␣ protein; however, analysis of a complex binding pattern with nuclear extracts showed that ATF-1 and CREB-1 bound to this motif. These data coupled with results of transient transfection studies demonstrated that transcriptional activation by E2 of the ؊1578 to ؊1534 region of the bcl-2 gene promoter was dependent on induction of cAMP and subsequent activation through a cAMP response element. Thus, hormone regulation of bcl-2 gene expression in breast cancer cells involves multiple enhancer elements and E2-mediated transactivation does not require direct binding of the estrogen receptor with promoter DNA.

SUMMARY The ATP-dependent chromatin remodeling complex SWI/SNF regulates transcription and has been implicated in promoter nucleosome eviction. Efficient nucleosome disassembly by SWI/SNF alone in biochemical assays has however not been directly observed. Employing a model system of dinucleosomes rather than mononucleosomes, we demonstrate that remodeling leads to ordered and efficient disassembly of one of the two nucleosomes. An H2A/H2B dimer is first rapidly displaced and then in a slower reaction an entire histone octamer is lost. Nucleosome disassembly by SWI/SNF did not require additional factors such as chaperones or acceptors of histones. Observations in single molecules as well as bulk measurement suggest that a key intermediate in this process is one in which a nucleosome is moved towards the adjacent nucleosome. SWI/SNF recruited by the transcriptional activator Gal4-VP16 preferentially mobilizes the proximal nucleosome and destabilizes the adjacent nucleosome.