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Colorectal cancer (CRC) is the third leading cancer-related cause of death due to its propensity to metastasize. Epithelial-mesenchymal transition (EMT) is a multistep process important for invasion and metastasis of CRC. Krüppel-like... more
Colorectal cancer (CRC) is the third leading cancer-related cause of death due to its propensity to metastasize. Epithelial-mesenchymal transition (EMT) is a multistep process important for invasion and metastasis of CRC. Krüppel-like factor 4 (KLF4) is a zinc finger transcription factor highly expressed in differentiated cells of the intestinal epithelium. KLF4 has been shown to play a tumor suppressor role during CRC tumorigenesis - its loss accelerates development and progression of cancer. The present study examines the relationship between KLF4 and markers of EMT in CRC.MethodsImmunofluorescence staining for KLF4 and EMT markers was performed on archived patient samples after colorectal cancer resection and on colonic tissues of mice with colitis-associated cancer.ResultsWe found that KLF4 expression is lost in tumor sections obtained from CRC patients and in those of mouse colon following azoxymethane and dextran sodium sulfate (AOM/DSS) treatment when compared to their respec...
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Krüppel-like factor 4 (KLF4) is an evolutionarily conserved zinc finger-containing transcription factor that regulates diverse cellular processes such as cell growth, proliferation, and differentiation. Since its discovery in 1996, KLF4... more
Krüppel-like factor 4 (KLF4) is an evolutionarily conserved zinc finger-containing transcription factor that regulates diverse cellular processes such as cell growth, proliferation, and differentiation. Since its discovery in 1996, KLF4 has been gaining a lot of attention, particularly after it was shown in 2006 as one of four factors involved in the induction of pluripotent stem cells (iPSCs). Here we review the current knowledge about the different functions and roles of KLF4 in various tissue and organ systems.
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Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), significantly increases the risk for development of colorectal cancer. Specifically, dysplasia and cancer associated with IBD... more
Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD), significantly increases the risk for development of colorectal cancer. Specifically, dysplasia and cancer associated with IBD (colitis-associated cancer or CAC) develop as a result of repeated cycles of injury and healing in the intestinal epithelium. Animal models are utilized to examine the mechanisms of CAC, the role of epithelial and immune cells in this process, as well as the development of novel therapeutic targets. These models typically begin with the administration of a carcinogenic compound, and inflammation is caused by repeated cycles of colitis-inducing agents. This review describes a common CAC model that utilizes the pro-carcinogenic compound azoxymethane (AOM) followed by dextran sulfate sodium (DSS) which induces the inflammatory insult.
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In response to ionizing radiation-induced injury, the normally quiescent intestinal stem cells marked by BMI1 participate in the regenerative response. Previously, we established a protective role for Krüppel-like factor 4 (KLF4) in the... more
In response to ionizing radiation-induced injury, the normally quiescent intestinal stem cells marked by BMI1 participate in the regenerative response. Previously, we established a protective role for Krüppel-like factor 4 (KLF4) in the intestinal epithelium where it reduces senescence, apoptosis, and crypt atrophy following γ-radiation-induced gut injury. We also described a pro-proliferative function for KLF4 during the regenerative phase post irradiation. In the current study, using a mouse model in which Klf4 is deleted from quiescent BMI1(+) intestinal stem cells, we observed increased proliferation from the BMI1(+) lineage during homeostasis. In contrast, following irradiation, Bmi1-specific Klf4 deletion leads to decreased expansion of the BMI1(+) lineage due to a combination of reduced proliferation and increased apoptosis. Our results support a critical role for KLF4 in modulating BMI1(+) intestinal stem cell fate in both homeostasis and the regenerative response to radiati...
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Understanding the role of factors that regulate intestinal epithelial homeostasis and response to injury and regeneration is important. The current literature describes several different methodological approaches to obtain images of... more
Understanding the role of factors that regulate intestinal epithelial homeostasis and response to injury and regeneration is important. The current literature describes several different methodological approaches to obtain images of intestinal tissues for data validation. In this paper, we delineate a common protocol relating to the derivation and processing of mouse intestinal tissues. Proper fixation of intestinal tissues and Swiss-roll techniques that enhance intestinal epithelial morphology are discussed. Postresection processing and reorientation of embedded intestinal tissues are critical in obtaining paraffin-embedded blocks that display intact intestinal structural features after sectioning. The Swiss-rolling technique helps in histological assessment of the complete intestinal or colonic sections examined. An ability to differentiate intestinal structural features can be vital in quantitative measurements of intestinal inflammation and tumorigenesis along the entire length....
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Alterations in sphingolipid metabolism, especially ceramide and sphingosine 1-phosphate, have been linked to colon cancer, suggesting that enzymes of sphingolipid metabolism may emerge as novel regulators and targets in colon cancer.... more
Alterations in sphingolipid metabolism, especially ceramide and sphingosine 1-phosphate, have been linked to colon cancer, suggesting that enzymes of sphingolipid metabolism may emerge as novel regulators and targets in colon cancer. Neutral ceramidase (nCDase), a key enzyme in sphingolipid metabolism that hydrolyzes ceramide into sphingosine, is highly expressed in the intestine; however, its role in colon cancer has not been defined. Here we show that molecular and pharmacological inhibition of nCDase in colon cancer cells increases ceramide, and this is accompanied by decreased cell survival and increased apoptosis and autophagy, with minimal effects on noncancerous cells. Inhibition of nCDase resulted in loss of β-catenin and inhibition of ERK, components of pathways relevant for colon cancer development. Furthermore, inhibition of nCDase in a xenograft model delayed tumor growth and increased ceramide while decreasing proliferation. It is noteworthy that mice lacking nCDase tre...
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BACKGROUND: Krüppel-like factor 4 (KLF4) is a zinc-finger transcription factor with diverse regulatory functions in proliferation, differentiation, and development. KLF4 also plays a role in inflammation, tumorigenesis, and reprogramming... more
BACKGROUND: Krüppel-like factor 4 (KLF4) is a zinc-finger transcription factor with diverse regulatory functions in proliferation, differentiation, and development. KLF4 also plays a role in inflammation, tumorigenesis, and reprogramming of somatic cells to induced pluripotent stem (iPS) cells. To gain insight into the mechanisms by which KLF4 regulates these processes, we conducted DNA microarray analyses to identify differentially expressed genes in mouse embryonic fibroblasts (MEFs) wild type and null for Klf4. METHODS: Expression profiles of fibroblasts isolated from mouse embryos wild type or null for the Klf4 alleles were examined by DNA microarrays. Differentially expressed genes were subjected to the Database for Annotation, Visualization and Integrated Discovery (DAVID). The microarray data were also interrogated with the Ingenuity Pathway Analysis (IPA) and Gene Set Enrichment Analysis (GSEA) for pathway identification. Results obtained from the microarray analysis were co...
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Research Interests: Biology, Cell Biology, Mitochondria, Apoptosis, Medicine, and 15 moreHIV, Humans, Kidney, Female, Animals, Male, Chromatin Immunoprecipitation, Podocyte, Clinical Investigation, Podocytes, Glomerulosclerosis, Focal Segmental Glomerulosclerosis, binding sites, Medical and Health Sciences, and HIV infections
Gut radiation-induced injury is a concern during treatment of patients with cancer. Krüppel-like factor 4 (KLF4) is expressed in differentiated villous epithelial cells of the small intestine. We previously showed that KLF4 protects cells... more
Gut radiation-induced injury is a concern during treatment of patients with cancer. Krüppel-like factor 4 (KLF4) is expressed in differentiated villous epithelial cells of the small intestine. We previously showed that KLF4 protects cells from apoptosis following γ-irradiation in vitro. We sought to determine whether KLF4 mediates the small intestinal response to γ-irradiation in vivo. Mice with intestinal epithelium-specific deletion of Klf4 ( Klf4ΔIS) and control ( Klf4fl/fl) mice were irradiated with total-body γ-radiation. Following irradiation, the Klf4ΔISmice had significantly increased mortality compared with irradiated Klf4fl/flmice. Immunohistochemistry and immunofluorescence staining were used to assess the morphological changes, levels of proliferation, and apoptosis in the intestinal epithelium. At 96 h following irradiation, there was a regenerative response manifested by an expansion of the proliferative zone in both mouse groups, with the control mice having a higher ...
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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 ApcMin/+ mice promotes... more
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 ApcMin/+ 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 γ-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 act...
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Background Both mutational inactivation of the adenomatous polyposis coli (APC) tumor suppressor gene and activation of the KRAS oncogene are implicated in the pathogenesis of colorectal cancer. Mice harboring a germline Apc Min mutation... more
Background Both mutational inactivation of the adenomatous polyposis coli (APC) tumor suppressor gene and activation of the KRAS oncogene are implicated in the pathogenesis of colorectal cancer. Mice harboring a germline Apc Min mutation or intestine-specific expression of the KRAS V 12gene have been developed. Both mouse strains develop spontaneous intestinal tumors, including adenoma and carcinoma, though at a different age. The zinc finger transcription factor Krüppel-like factor 5 (KLF5) has previously been shown to promote proliferation of intestinal epithelial cells and modulate intestinal tumorigenesis. Here we investigated the in vivo effect of Klf5 heterozygosity on the propensity of Apc Min /KRAS V 12double transgenic mice to develop intestinal tumors. Results At 12 weeks of age, Apc Min /KRAS V 12mice had three times as many intestinal tumors as Apc Min mice. This increase in tumor number was reduced by 92% in triple transgenic Apc Min /KRAS V 12/Klf5 +/- mice. The reduct...
Research Interests: Biology, Research, Cancer Research, Medicine, Colorectal cancer, and 15 moreTransgenic Mice, Molecular, Intestinal Mucosa, Mutation, Mice, Animals, Oncogene, Statistical Significance, Transcription Factor, Carcinogenesis, Tumor Suppressor Gene, KRAS, Cumulant, Colorectal Neoplasms, and Familial adenomatous polyposis
Background Krüppel-like factor 4 (KLF4) is a member of the KLF family of transcription factors and regulates proliferation, differentiation, apoptosis and somatic cell reprogramming. Evidence also suggests that KLF4 is a tumor suppressor... more
Background Krüppel-like factor 4 (KLF4) is a member of the KLF family of transcription factors and regulates proliferation, differentiation, apoptosis and somatic cell reprogramming. Evidence also suggests that KLF4 is a tumor suppressor in certain cancers including colorectal cancer. We previously showed that KLF4 inhibits cell cycle progression following DNA damage and that mouse embryonic fibroblasts (MEFs) null for Klf4 are genetically unstable, as evidenced by increased rates of cell proliferation, and the presence of DNA double strand breaks (DSBs), centrosome amplification, chromosome aberrations and aneuploidy. Methods To determine whether re-expression of Klf4 corrects the observed genetic instability in MEFs null for Klf4 (Klf4 −/− ), we transfected Klf4 −/− MEFs with Klf4-expressing plasmids and compared the results to wild type (Klf4 +/+ ) and untransfected or mock-transfected Klf4 −/− MEFs. Results We show that overexpression of Klf4 in Klf4 −/− MEFs reduced cell prolif...
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Research Interests: Biology, Inflammation, Cell Adhesion, Nanoparticles, Macrophages, and 15 moreCancer Research, Medicine, Inflammatory Bowel Disease, Intestinal Mucosa, Mice, Female, Animals, Male, Clinical Sciences, Colitis, Fluorescent Antibody Technique, Cell Proliferation, Inflammatory Bowel Diseases, real time polymerase chain reaction, and reverse transcriptase polymerase chain reaction
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Research Interests: Gastroenterology, Biology, Cancer Research, Medicine, Humans, and 13 moreIntestinal Mucosa, Mice, Animals, Clinical Sciences, Carcinogenesis, Epithelial cells, Cell Proliferation, KRAS, Neurosciences, Cell Growth, Colorectal Neoplasms, Paediatrics and reproductive medicine, and Cell culture techniques
Research Interests: Gastroenterology, Biology, Cytokines, Inflammation, Cancer Research, and 15 moreMedicine, Colorectal cancer, Animals, Male, Clinical Sciences, Colitis, Lipopolysaccharides, Carcinogenesis, Disease Progression, Cell Proliferation, Lysophosphatidic Acid, Experimental Model, Autotaxin, Colonic Neoplasms, and Cyclooxygenase
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Research Interests: Gastroenterology, Biology, Immunohistochemistry, Cell Biology, Medicine, and 15 moreCell Differentiation, Intestinal Mucosa, Mice, Animals, Clinical Sciences, Intestinal absorption, Genotype, Epithelial cells, Ephrins, Cell Proliferation, Colon, Neurosciences, Crypt, Ileum, and Paediatrics and reproductive medicine
Research Interests: Developmental Biology, Regeneration, Biology, Medicine, Signal Transduction, and 15 moreBiological Sciences, RNA interference, Humans, Mice, Animals, Proteins, Tamoxifen, Cell Proliferation, Colon, Goblet Cells, Crypt, Small Intestine, Down-Regulation, Colorectal Neoplasms, and Medical and Health Sciences
Research Interests: Developmental Biology, Biology, Immunohistochemistry, Cell Biology, Medicine, and 15 moreBiological Sciences, Cell Differentiation, Intestinal Mucosa, Mice, Animals, Polymerase Chain Reaction, Alkaline phosphatase, Fluorescent Antibody Technique, Zinc Finger, Epithelial cells, Homeostasis, Cell Proliferation, Crypt, Small Intestine, and Medical and Health Sciences
The zinc finger transcription factor Krüppel-like factor 4 (KLF4) is frequently down-regulated in colorectal cancer. Previous studies showed that the expression of KLF4 was activated by the colorectal cancer tumor suppressor adenomatous... more
The zinc finger transcription factor Krüppel-like factor 4 (KLF4) is frequently down-regulated in colorectal cancer. Previous studies showed that the expression of KLF4 was activated by the colorectal cancer tumor suppressor adenomatous polyposis coli (APC) and that KLF4 repressed the Wnt/β-catenin pathway. Here, we examined whether KLF4 plays a role in modulating intestinal tumorigenesis by comparing the tumor burdens in mice heterozygous for the ApcMin allele (ApcMin/+) and those heterozygous for both the ApcMin and Klf4 alleles (Klf4+/−/ApcMin/+). Between 10 and 20 weeks of age, Klf4+/−/ApcMin/+ mice developed, on average, 59% more intestinal adenomas than ApcMin/+ mice (P < 0.0001). Immunohistochemical staining showed that Klf4 protein levels were lower in the normal-appearing intestinal tissues of Klf4+/−/ApcMin/+ mice compared with wild-type, Klf4+/−, or ApcMin/+ mice. In contrast, the levels of β-catenin and cyclin D1 were higher in the normal-appearing intestinal tissues...
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Background: The zinc finger transcription factor Krüppel-like factor 4 (KLF4) regulates numerous physiologic processes, including proliferation, differentiation, and development. Studies also showed that KLF4 is involved in tumorigenesis... more
Background: The zinc finger transcription factor Krüppel-like factor 4 (KLF4) regulates numerous physiologic processes, including proliferation, differentiation, and development. Studies also showed that KLF4 is involved in tumorigenesis and somatic cell reprogramming. Here, we aimed to assess whether KLF4 is a prognostic indicator for colon cancer. Methods: Levels of KLF4 were measured by immunohistochemical analysis of a tissue microarray containing 367 independent colon cancer sections. Univariate data analysis was done in addition to construction of multivariate models with several clinicopathologic factors to evaluate KLF4 as an independent predictor of survival and cancer recurrence (disease-free survival). Results: Colon cancer tissues had significantly overall lower KLF4 levels compared with noncancer tissues (P < 0.0001). Using logistic regression, a trend was noted for decreased odds of KLF4 expression in higher stages of tumors. In univariate and multivariate analyses,...
Research Interests: Oncology, Cancer, Survival Analysis, Immunohistochemistry, Medicine, and 15 moreColorectal cancer, Humans, Internal Medicine, Female, C2H2 zinc fingers, Male, Aged, Middle Aged, Retrospective Studies, Prognosis, Univariate Analysis, Case Control Studies, Disease Free Survival, Medical and Health Sciences, and Colonic Neoplasms
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The zinc finger transcription factor Krüppel-like factor 4 (KLF4) is frequently downregulated in colorectal cancer. Previous studies showed that KLF4 is a tumor suppressor in the intestinal tract and plays an important role in DNA... more
The zinc finger transcription factor Krüppel-like factor 4 (KLF4) is frequently downregulated in colorectal cancer. Previous studies showed that KLF4 is a tumor suppressor in the intestinal tract and plays an important role in DNA damage-repair mechanisms. Here, the in vivo effects of Klf4 deletion were examined from the mouse intestinal epithelium (Klf4ΔIS) in a genetic or pharmacological setting of colonic tumorigenesis: ApcMin/+ mutation or carcinogen treatment with azoxymethane (AOM), respectively. Klf4ΔIS/ApcMin/+ mice developed significantly more colonic adenomas with 100% penetrance as compared with ApcMin/+ mice with intact Klf4 (Klf4fl/fl/ApcMin/+). The colonic epithelium of Klf4ΔIS/ApcMin/+ mice showed increased mTOR pathway activity, together with dysregulated epigenetic mechanism as indicated by altered expression of HDAC1 and p300. Colonic adenomas from both genotypes stained positive for γH2AX, indicating DNA double-strand breaks. In Klf4ΔIS/ApcMin/+ mice, this was ass...
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Inactivation of the tumor suppressor adenomatous polyposis coli, with the resultant activation of β-catenin, is the initiating event in the development of a majority of colorectal cancers. Krüppel-like factor 5 (KLF5), a proproliferative... more
Inactivation of the tumor suppressor adenomatous polyposis coli, with the resultant activation of β-catenin, is the initiating event in the development of a majority of colorectal cancers. Krüppel-like factor 5 (KLF5), a proproliferative transcription factor, is highly expressed in the proliferating intestinal crypt epithelial cells. To determine whether KLF5 contributes to intestinal adenoma formation, we examined tumor burdens in ApcMin/+ mice and ApcMin/+/Klf5+/− mice. Compared with ApcMin/+ mice, ApcMin/+/Klf5+/− mice had a 96% reduction in the number of intestinal adenomas. Reduced tumorigenicity in the ApcMin/+/Klf5+/− mice correlated with reduced levels and nuclear localization of β-catenin as well as reduced expression of two β-catenin targets, cyclin D1 and c-Myc. In vitro studies revealed a physical interaction between KLF5 and β-catenin that enhanced the nuclear localization and transcriptional activity of β-catenin. Thus, KLF5 is necessary for the tumor-initiating activ...
Research Interests: Cancer, Biology, Cancer Research, Medicine, Colorectal cancer, and 15 moreCercopithecus aethiops, Mutation, Mice, Haplotypes, Animals, Male, Beta-Catenin, Haploinsufficiency, Transcription Factor, Intestines, Cell nucleus, Adenomatous Polyposis-coli, Adenoma, Colorectal Neoplasms, and Familial adenomatous polyposis
Krüppel-like factors (KLFs) are evolutionarily conserved zinc finger-containing transcription factors with diverse regulatory functions in cell growth, proliferation, differentiation, and embryogenesis. KLF4 and KLF5 are two closely... more
Krüppel-like factors (KLFs) are evolutionarily conserved zinc finger-containing transcription factors with diverse regulatory functions in cell growth, proliferation, differentiation, and embryogenesis. KLF4 and KLF5 are two closely related members of ...