Notch inhibits expression of the Krüppel-like factor 4 tumor suppressor in the intestinal epithelium.

Division of Digestive Diseases, Department of Medicine, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322, USA.
Molecular Cancer Research (Impact Factor: 4.35). 12/2008; 6(12):1920-7. DOI:10.1158/1541-7786.MCR-08-0224
Source: PubMed

ABSTRACT The zinc finger-containing transcription factor, Krüppel-like factor 4 (KLF4), inhibits cell proliferation. An in vivo tumor-suppressive role for KLF4 is shown by the recent finding that Klf4 haploinsufficiency in Apc(Min/+) mice promotes intestinal tumorigenesis. Studies also show that KLF4 is required for the terminal differentiation of goblet cells in the mouse intestine. The Notch signaling pathway suppresses goblet cell formation and is up-regulated in intestinal tumors. Here, we investigated the relationship between Notch signaling and KLF4 expression in intestinal epithelial cells. The rate of proliferation of HT29 human colon cancer cells was reduced when treated with the gamma-secretase inhibitor dibenzazepine to inhibit Notch signaling or small interfering RNA directed against Notch. KLF4 levels were increased in dibenzazepine-treated or Notch small interfering RNA-treated cells. Conversely, overexpression of Notch in HT29 cells reduced KLF4 levels, suppressed KLF4 promoter activity, and increased proliferation rate. Treatment of Apc(Min/+) mice with dibenzazepine resulted in a 50% reduction in the number of intestinal adenomas compared with the vehicle-treated group (P < 0.001). Both the normal-appearing intestinal mucosa and adenomas obtained from dibenzazepine-treated Apc(Min/+) mice had increased goblet cell numbers and Klf4 staining accompanied by reduced cyclin D1 and Ki-67 staining when compared with those from vehicle-treated mice. Results of these studies indicate that Notch signaling suppresses KLF4 expression in intestinal tumors and colorectal cancer cells. Inhibition of Notch signaling increases KLF4 expression and goblet cell differentiation and reduces proliferation and tumor formation. KLF4 is therefore a potential mediator for the antitumor effect of Notch inhibitors such as dibenzazepine.

0 0
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Even though the number of anti-cancer drugs entering clinical trials and approved by the FDA has increased in recent years, many cancer patients still experience poor survival outcome. The main explanation for such a dismal prognosis is that current therapies might leave behind a population of cancer cells with the capacity for long-term self-renewal, so-called cancer stem cells (CSCs), from which most tumors are believed to be derived and fueled. CSCs might favor local and distant recurrence even many years after initial treatment, thus representing a potential target for therapies aimed at improving clinical outcome. In this review, we will address the CSC hypothesis with a particular emphasis on its current paradigms and debates, and discuss several mechanisms of CSC resistance to conventional therapies.
    Current pathobiology reports. 06/2013; 1(2):111-118.
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: Cancer cells frequently adopt cellular and molecular alterations and acquire resistance to cytostatic drugs. Chemotherapy with oxaliplatin is among the leading treatments for colorectal cancer with a response rate of 50%, inducing intrastrand cross-links on the DNA. Despite of this drug's efficiency, resistance develops in nearly all metastatic patients. Chemoresistance being of crucial importance for the drug's clinical efficiency this study aimed to contribute to the identification and description of some cellular and molecular alterations induced by prolonged oxaliplatin therapy. Resistance to oxaliplatin was induced in Colo320 (Colo320R) and HT-29 (HT-29R) colorectal adenocarcinoma cell lines by exposing the cells to increasing concentrations of the drug. Alterations in morphology, cytotoxicity, DNA cross-links formation and gene expression profiles were assessed in the parental and resistant variants with microscopy, MTT, alkaline comet and pangenomic microarray assays, respectively. Morphology analysis revealed epithelial-to-mesenchymal transition in the resistant vs parental cells suggesting alterations of the cells' adhesion complexes, through which they acquire increased invasiveness and adherence. Cytotoxicity measurements demonstrated resistance to oxaliplatin in both cell lines; Colo320 being more sensitive than HT-29 to this drug (P < 0.001). The treatment with oxaliplatin caused major DNA cross-links in both parental cell lines; in Colo320R small amounts of DNA cross-links were still detectable, while in HT-29R not. We identified 441 differentially expressed genes in Colo320R and 613 in HT-29R as compared to their parental counterparts (at least 1.5 -fold up- or down- regulation, p < 0.05). More disrupted functions and pathways were detected in HT-29R cell line than in Colo320R, involving genes responsible for apoptosis inhibition, cellular proliferation and epithelial-to-mesenchymal transition. Several upstream regulators were detected as activated in HT-29R cell line, but not in Colo320R. Our findings revealed a more resistant phenotype in HT-29R as compared to Colo320R and different cellular and molecular chemoresistance patterns induced by prolonged treatment with oxaliplatin in cell lines with identical origins (colorectal adenocarcinomas).
    BMC Genomics 07/2013; 14(1):480. · 4.40 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: To investigate the potential roles of Delta-like ligand 4 (DLL4) on the biological behavior of gastric cancer cells and its molecular mechanisms. A recombinant eukaryotic expression vector containing human DLL4 gene was constructed and transfected into the human gastric cancer cell line SGC7901. Clones with up-regulated DLL4 were selected and amplified. The effect of DLL4 up-regulation on gastric cancer cell growth was assessed using cell growth assay. The migration and invasion were assessed using a transwell migration assay and matrigel invasion assay. Matrix metalloproteinases were detected using the zymogram technique. Cells were implanted subcutaneously into male BALB/c nu/nu mice. Tumor volumes were then calculated and compared. DLL4 staining in the implanted tumor was performed using immunohistochemistry technique. Growth curves over a six-day time course showed significantly promoted cell proliferation of SGC7901 cells with up-regulated DLL4. DLL4 up-regulation in SGC7901 cells promoted the migration (205.4 ± 15.2 vs 22.3 ± 12.1, P < 0.05) and invasion (68.8 ± 5.3 vs 18.2 ± 6.0, P < 0.05) in vitro and tumorigenicity in vivo (2640.5 ± 923.6 mm(3) vs 1115.1 ± 223.8 mm(3), P < 0.05). Furthermore, significantly increased mRNA level and increased secretion of matrix metalloproteinase-2 (MMP-2) proenzyme were observed in SGC7901 cells with up-regulated DLL4. However, increased MMP-9 mRNA level but decreased extracellular MMP-9 proenzyme level was observed. Our observations indicated a mechanism by which activation of DLL4-mediated Notch signaling promotes the expression and secretion of MMP-2 proenzyme and influences the progress of gastric cancer.
    World Journal of Gastroenterology 07/2013; 19(28):4486-94. · 2.55 Impact Factor


1 Download
Available from