HDAC3 ensures stepwise epidermal stratification via NCoR/SMRT-reliant mechanisms independent of its histone deacetylase activity.

Chromatin modifiers play critical roles in epidermal development, but the functions of histone deacetylases in this context are poorly understood. The class I HDAC, HDAC3, is of particular interest because it plays divergent roles in different tissues by partnering with tissue-specific transcription factors. We found that HDAC3 is expressed broadly in embryonic epidermis and is required for its orderly stepwise stratification. HDAC3 protein stability in vivo relies on NCoR and SMRT, which function redundantly in epidermal development. However, point mutations in the NCoR and SMRT deacetylase-activating domains, which are required for HDAC3's enzymatic function, permit normal stratification, indicating that HDAC3's roles in this context are largely independent of its histone deacetylase activity. HDAC3-bound sites are significantly enriched for predicted binding motifs for critical epidermal transcription factors including AP1, GRHL, and KLF family members. Our results suggest that among these, HDAC3 operates in conjunction with KLF4 to repress inappropriate expression of Tgm1, Krt16, and Aqp3 In parallel, HDAC3 suppresses expression of inflammatory cytokines through a Rela-dependent mechanism. These data identify HDAC3 as a hub coordinating multiple aspects of epidermal barrier acquisition.

Esophageal Expression of Active IκB Kinase-ß in Mice Up-Regulates Tumor Necrosis Factor and Granulocyte-Macrophage Colony-Stimulating Factor, Promoting Inflammation and Angiogenesis.

BACKGROUND & AIMS: IκB kinase-ß (IKKß) mediates activation of the nuclear factor-κB, which regulates immune and inflammatory responses. Although nuclear factor-κB is activated in cells from patients with inflammatory diseases or cancer, little is known about its roles in the development and progression of esophageal diseases. We investigated whether mice that express an activated form of IKKß in the esophageal epithelia develop esophageal disorders. METHODS: We generated ED-L2-Cre/Rosa26-IKK2caSFL mice, in which the ED-L2 promoter activates expression of Cre in the esophageal epithelia, leading to expression of a constitutively active form of IKKß (IKKßca) in epithelial cells but not in inflammatory cells or the surrounding stroma (IKKßca mice). Mice lacking the Cre transgene served as controls. Some mice were given intraperitoneal injections of neutralizing antibodies against granulocyte-macrophage colony-stimulating factor (GM-CSF) or tumor necrosis factor (TNF), or immunoglobulin G1 (control), starting at 1 month of age. Epithelial tissues were collected and analyzed by immunofluorescence, immunohistochemical, and quantitative real-time polymerase chain reaction assays. Transgenes were overexpressed from retroviral vectors in primary human keratinocytes. RESULTS: IKKßca mice developed esophagitis and had increased numbers of blood vessels in the esophageal stroma, compared with controls. Esophageal tissues from IKKßca mice had increased levels of GM-CSF. Expression of IKKßca in primary human esophageal keratinocytes led to 11-fold overexpression of GM-CSF and 200-fold overexpression of TNF. Incubation of human umbilical vein endothelial cells with conditioned media from these keratinocytes increased endothelial cell migration by 42% and promoted formation of capillary tubes; these effects were blocked by a neutralizing antibody against GM-CSF. Injections of anti-GM-CSF reduced angiogenesis and numbers of CD31+ blood vessels in esophageal tissues of IKKßca mice, but did not alter the esophageal vasculature of control mice and did not alter recruitment of intraepithelial leukocytes to esophageal tissues of IKKßca mice. Injections of anti-TNF prevented the development of esophagitis in IKKßca mice. CONCLUSIONS: Constitutive activation of IKKß in the esophageal epithelia of mice leads to inflammation and angiogenesis, mediated by TNF and GM-CSF, respectively.

KLF5 inhibition initiates epithelial-mesenchymal transition in non-transformed human squamous epithelial cells.

The transcriptional regulator Krüppel-like factor 5 (KLF5) is highly expressed in squamous epithelial cells of the esophagus. Increased KLF5 activity induces tumorigenesis and promotes metastasis in several cancers, although this function appears to be context-dependent. Here, we demonstrate that acute KLF5 inhibition, both genetically and with the potent KLF5 inhibitor ML264, causes non-transformed human primary esophageal squamous epithelial cells to enter the epithelial to mesenchymal transition (EMT). Moreover, chronic KLF5 inhibition with ML264 leads to the development of cells with a mesenchymal phenotype characterized by the expression of mesenchymal markers and functionally by reduced cell growth and increased migration and cellular invasion. This EMT resulting from chronic KLF5 inhibition is not driven by ß-Catenin or TGF-ß signaling. Pharmacologically, ML264 inhibits KLF5 by promoting proteasomal-mediated degradation. Taken together, we demonstrate that reduced KLF5 activity reprograms epithelial cells towards a mesenchymal phenotype and enhances their migratory and invasive potential. These findings have potential implications not only for esophageal cancers but also for normal processes such as esophageal tissue repair following injury.

Neutrophils in Cancer and Potential Therapeutic Strategies Using Neutrophil-Derived Exosomes.

Neutrophils are the most abundant immune cells and make up about 70% of white blood cells in human blood and play a critical role as the first line of defense in the innate immune response. They also help regulate the inflammatory environment to promote tissue repair. However, in cancer, neutrophils can be manipulated by tumors to either promote or hinder tumor growth depending on the cytokine pool. Studies have shown that tumor-bearing mice have increased levels of neutrophils in peripheral circulation and that neutrophil-derived exosomes can deliver various cargos, including lncRNA and miRNA, which contribute to tumor growth and degradation of extracellular matrix. Exosomes derived from immune cells generally possess anti-tumor activities and induce tumor-cell apoptosis by delivering cytotoxic proteins, ROS generation, H2O2 or activation of Fas-mediated apoptosis in target cells. Engineered exosome-like nanovesicles have been developed to deliver chemotherapeutic drugs precisely to tumor cells. However, tumor-derived exosomes can aggravate cancer-associated thrombosis through the formation of neutrophil extracellular traps. Despite the advancements in neutrophil-related research, a detailed understanding of tumor-neutrophil crosstalk is still lacking and remains a major barrier in developing neutrophil-based or targeted therapy. This review will focus on the communication pathways between tumors and neutrophils, and the role of neutrophil-derived exosomes (NDEs) in tumor growth. Additionally, potential strategies to manipulate NDEs for therapeutic purposes will be discussed.

KLF5 and p53 comprise an incoherent feed-forward loop directing cell-fate decisions following stress.

In response to stress, cells make a critical decision to arrest or undergo apoptosis, mediated in large part by the tumor suppressor p53. Yet the mechanisms of these cell fate decisions remain largely unknown, particularly in normal cells. Here, we define an incoherent feed-forward loop in non-transformed human squamous epithelial cells involving p53 and the zinc-finger transcription factor KLF5 that dictates responses to differing levels of cellular stress from UV irradiation or oxidative stress. In normal unstressed human squamous epithelial cells, KLF5 complexes with SIN3A and HDAC2 repress TP53, allowing cells to proliferate. With moderate stress, this complex is disrupted, and TP53 is induced; KLF5 then acts as a molecular switch for p53 function by transactivating AKT1 and AKT3, which direct cells toward survival. By contrast, severe stress results in KLF5 loss, such that AKT1 and AKT3 are not induced, and cells preferentially undergo apoptosis. Thus, in human squamous epithelial cells, KLF5 gates the response to UV or oxidative stress to determine the p53 output of growth arrest or apoptosis.

All-Trans Retinoic Acid Promotes a Tumor Suppressive OTUD6B-ß-TrCP-SNAIL Axis in Esophageal Squamous Cell Carcinoma and Enhances Immunotherapy.

ß-TrCP is an E3 ubiquitin ligase that plays important roles in multiple human cancers including esophageal squamous cell carcinoma (ESCC). Analysis of ESCC patient samples reveal that only protein level but not transcript level of ß-TrCP associated with patient prognosis, suggesting regulators of ß-TrCP protein stability play an essential role in ESCC progression and may be novel targets to develop ESCC therapies. Although ß-TrCP stability is known to be mediated by the ubiquitin-proteasome system, it is unclear which enzymes play a major role to determine ß-TrCP stability in the context of ESCC. In this study, OTUD6B is identified as a potent deubiquitinase of ß-TrCP that suppress ESCC progression through the OTUD6B-ß-TrCP-SNAIL axis. Low OTUD6B expression is associated with a poor prognosis of ESCC patients. Importantly, all-trans retinoic acid (ATRA) is found to promote OTUD6B translation and thus suppress ESCC tumor growth and enhance the response of ESCC tumors to anti-PD-1 immunotherapies. These findings demonstrate that OTUD6B is a crucial deubiquitinase of ß-TrCP in ESCC and suggest combination of ATRA and anti-PD-1 immune checkpoint inhibitor may benefit a cohort of ESCC patients.

Esophageal squamous cell dysplasia and delayed differentiation with deletion of krüppel-like factor 4 in murine esophagus.

BACKGROUND & AIMS: Krüppel-like factor 4 (Klf; previously known a gut-enriched Krüppel-like factor) is a DNA-binding transcriptional regulator highly expressed in skin and gastrointestinal epithelia, specifically in regions of cellular differentiation. Homozygous null mice for Klf4 die shortly after birth from skin defects, precluding their analysis at later stages. The aim of this study was to analyze the function of Klf4 in keratinocyte biology and epithelial homeostasis in the adult by focusing on the squamous lined esophagus. METHODS: By using the ED-L2 promoter of Epstein-Barr virus to drive Cre, we obtained tissue-specific ablation of Klf4 in the squamous epithelia of the tongue, esophagus, and forestomach. RESULTS: Mice with loss of Klf4 in esophageal epithelia survived to adulthood, bypassing the early lethality. Tissue-specific Klf4 knockout mice had increased basal cell proliferation and a delay in cellular maturation; these mice developed epithelial hypertrophy and subsequent dysplasia by 6 months of age. Moreover, loss of Klf4 in vivo was associated with increased expression of the pro-proliferative Klf5, and Klf4 down-regulated Klf5 both transcriptionally and posttranscriptionally. By using gene expression profiling, we also showed decreased expression of critical late-stage differentiation factors and identified alterations of several genes important in cellular differentiation. CONCLUSIONS: Klf4 is essential for squamous epithelial differentiation in vivo and interacts with Klf5 to maintain normal epithelial homeostasis.

Klf4 overexpression activates epithelial cytokines and inflammation-mediated esophageal squamous cell cancer in mice.

BACKGROUND & AIMS: Esophageal squamous cell cancer accounts for more than 90% of cases of esophageal cancers. Its pathogenesis involves chronic epithelial irritation, although the factors involved in the inflammatory process and the mechanisms of carcinogenesis are unknown. We sought to develop a mouse model of this cancer. METHODS: We used the ED-L2 promoter of Epstein-Barr virus to overexpress the transcriptional regulator Krüppel-like factor 4 (Klf4) in esophageal epithelia of mice; we used mouse primary esophageal keratinocytes to examine the mechanisms by which KLF4 induces cytokine production. RESULTS: KLF4 was an epithelial-specific mediator of inflammation; we developed a new mouse model of esophageal squamous dysplasia and inflammation-mediated squamous cell cancer. KLF4 activated a number of proinflammatory cytokines, including TNF-α, CXCL5, G-CSF and IL-1α, within keratinocytes in an NF-κB-dependent manner. KLF4 was not detected in proliferating or cancer cells, indicating a non-cell autonomous effect of KLF4 on proliferation and carcinogenesis. CONCLUSIONS: KLF4 has distinct functions in carcinogenesis; upregulation of Klf4 specifically in esophageal epithelial cells induces inflammation. This mouse model might be used to determine the molecular mechanisms of esophageal squamous cell cancer and inflammation-mediated carcinogenesis.

NOTCH1 and NOTCH3 coordinate esophageal squamous differentiation through a CSL-dependent transcriptional network.

BACKGROUND & AIMS: The Notch receptor family regulates cell fate through cell-cell communication. CSL (CBF-1/RBP-jκ, Su(H), Lag-1) drives canonical Notch-mediated gene transcription during cell lineage specification, differentiation, and proliferation in the hematopoietic system, the intestine, the pancreas, and the skin. However, the functional roles of Notch in esophageal squamous epithelial biology are unknown. METHODS: Normal esophageal keratinocytes were stimulated with calcium chloride to induce terminal differentiation. The squamous epithelia were reconstituted in organotypic 3-dimensional culture, a form of human tissue engineering. Notch was inhibited in culture with a γ-secretase inhibitor or dominant negative mastermind-like 1 (DNMAML1). The roles of Notch receptors were evaluated by in vitro gain-of-function and loss-of-function experiments. Additionally, DNMAML1 was targeted to the mouse esophagus by cytokeratin K14 promoter-driven Cre (K14Cre) recombination of Lox-STOP-Lox-DNMAML1. Notch-regulated gene expression was determined by reporter transfection, chromatin immunoprecipitation assays, quantitative reverse-transcription polymerase chain reaction, Western blotting, immunofluorescence, and immunohistochemistry. RESULTS: NOTCH1 (N1) was activated at the onset of squamous differentiation in the esophagus. Intracellular domain of N1 (ICN1) directly activated NOTCH3 (N3) transcription, inducing HES5 and early differentiation markers such as involucrin (IVL) and cytokeratin CK13 in a CSL-dependent fashion. N3 enhanced ICN1 activity and was required for squamous differentiation. Loss of Notch signaling in K14Cre;DNMAML1 mice perturbed esophageal squamous differentiation and resulted in N3 loss and basal cell hyperplasia. CONCLUSIONS: Notch signaling is important for esophageal epithelial homeostasis. In particular, the cross talk of N3 with N1 during differentiation provides novel, mechanistic insights into Notch signaling and squamous epithelial biology.

Reprogramming of the esophageal squamous carcinoma epigenome by SOX2 promotes ADAR1 dependence.

Esophageal squamous cell carcinomas (ESCCs) harbor recurrent chromosome 3q amplifications that target the transcription factor SOX2. Beyond its role as an oncogene in ESCC, SOX2 acts in development of the squamous esophagus and maintenance of adult esophageal precursor cells. To compare Sox2 activity in normal and malignant tissue, we developed engineered murine esophageal organoids spanning normal esophagus to Sox2-induced squamous cell carcinoma and mapped Sox2 binding and the epigenetic and transcriptional landscape with evolution from normal to cancer. While oncogenic Sox2 largely maintains actions observed in normal tissue, Sox2 overexpression with p53 and p16 inactivation promotes chromatin remodeling and evolution of the Sox2 cistrome. With Klf5, oncogenic Sox2 acquires new binding sites and enhances activity of oncogenes such as Stat3. Moreover, oncogenic Sox2 activates endogenous retroviruses, inducing expression of double-stranded RNA and dependence on the RNA editing enzyme ADAR1. These data reveal SOX2 functions in ESCC, defining targetable vulnerabilities.

Conditional deletion of the mouse Klf4 gene results in corneal epithelial fragility, stromal edema, and loss of conjunctival goblet cells.

The Krüppel-like transcription factor KLF4 is among the most highly expressed transcription factors in the mouse cornea (B. Norman, J. Davis, and J. Piatigorsky, Investig. Ophthalmol. Vis. Sci. 45:429-440, 2004). Here, we deleted the Klf4 gene selectively in the surface ectoderm-derived structures of the eye (cornea, conjunctiva, eyelids, and lens) by mating Klf4-LoxP mice (J. P. Katz, N. Perreault, B. G. Goldstein, C. S. Lee, P. A. Labosky, V. W. Yang, and K. H. Kaestner, Development 129:2619-2628, 2002) with Le-Cre mice (R. Ashery-Padan, T. Marquardt, X. Zhou, and P. Gruss, Genes Dev. 14:2701-2711, 2000). Klf4 conditional null (Klf4CN) embryos developed normally, and the adult mice were viable and fertile. Unlike the wild type, the Klf4CN cornea consisted of three to four epithelial cell layers; swollen, vacuolated basal epithelial and endothelial cells; and edematous stroma. The conjunctiva lacked goblet cells, and the anterior cortical lens was vacuolated in Klf4CN mice. Excessive cell sloughing resulted in fewer epithelial cell layers in spite of increased cell proliferation at the Klf4CN ocular surface. Expression of the keratin-12 and aquaporin-5 genes was downregulated, consistent with the Klf4CN corneal epithelial fragility and stromal edema, respectively. These observations provide new insights into the role of KLF4 in postnatal maturation and maintenance of the ocular surface and suggest that the Klf4CN mouse is a useful model for investigating ocular surface pathologies such as dry eye, Meesmann's dystrophy, and Steven's-Johnson syndrome.

ARID1A prevents squamous cell carcinoma initiation and chemoresistance by antagonizing pRb/E2F1/c-Myc-mediated cancer stemness.

Squamous cell carcinoma (SCC) is defined as a category of aggressive malignancies arising from the squamous epithelium of various organs. Resistance to chemotherapies is a common feature of SCCs, which leads to a poor prognosis among SCC patients. Recently, studies have illustrated the essential tumor suppressive role of ARID1A in several cancer types, but its role in SCCs remains unclear. Cancer stemness has been recognized as a main reason for tumorigenesis and is commonly correlated with chemoresistance, yet the relationship between ARID1A and cancer stemness remains unknown. In this study, we showed that Arid1a conditional knockout mice had a high incidence of SCCs occurring in the tongue and esophagus. ARID1A depletion promoted tumor initiation and cancer stemness in human SCC cells. Mechanistic studies revealed that ARID1A blocked the interaction between cyclin-dependent kinases (CDKs) and retinoblastoma protein (Rb), reducing the phosphorylation of Rb. Dephosphorylated Rb suppressed E2F1 activity and then suppressed cancer stemness by inactivating c-Myc. Furthermore, we showed that ARID1A depletion significantly increased the chemoresistance of SCC and that a CDK inhibitor exhibited a favorable effect on rescuing the chemoresistance caused by ARID1A loss. Collectively, our study showed that ARID1A inhibits the cancer stemness of SCCs by competing with CDKs to bind with Rb to inhibit the E2F1/c-Myc pathway.

Krüppel-like factor 4 is involved in functional differentiation of testicular Sertoli cells.

Krüppel-like factor 4 (KLF4) is a pleiotropic zinc finger transcription factor that regulates genes being involved in differentiation and cell-cycle control. Knockout studies revealed a critical function for KLF4 in the terminal differentiation of many epithelial cells. In testicular Sertoli cells, Klf4 is strongly inducible by the glycoprotein follicle stimulating hormone (FSH). Because KLF4 is essential for postnatal survival in mice, we deleted Klf4 specifically in Sertoli cells using the Cre/loxP system. Importantly, around postnatal day 18, a critical period of terminal Sertoli cell differentiation, mutant seminiferous tubules exhibited a disorganized germinal epithelium and delayed lumen formation. The ultrastructural finding of highly vacuolized Sertoli cell cytoplasm and the identification of differentially expressed genes, which are known to play roles during vesicle transport and fusion or for maintenance of the differentiated cell state, suggest impaired apical secretion of the Sertoli cell. Interestingly, a high proportion of all identified genes was localized in a small subregion of chromosome 7, suggesting coordinated regulation. Intriguingly, adult mutant mice are fertile and show normal testicular morphology, although the testosterone levels are decreased. In summary, KLF4 plays a significant role for proper and timely Sertoli cell differentiation in pubertal mice.

Haploinsufficiency of Krüppel-like factor 4 promotes adenomatous polyposis coli dependent intestinal tumorigenesis.

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/beta-catenin pathway. Here, we examined whether KLF4 plays a role in modulating intestinal tumorigenesis by comparing the tumor burdens in mice heterozygous for the Apc(Min) allele (Apc(Min/+)) and those heterozygous for both the Apc(Min) and Klf4 alleles (Klf4(+/-)/Apc(Min/+)). Between 10 and 20 weeks of age, Klf4(+/-)/Apc(Min/+) mice developed, on average, 59% more intestinal adenomas than Apc(Min/+) mice (P < 0.0001). Immunohistochemical staining showed that Klf4 protein levels were lower in the normal-appearing intestinal tissues of Klf4(+/-)/Apc(Min/+) mice compared with wild-type, Klf4(+/-), or Apc(Min/+) mice. In contrast, the levels of beta-catenin and cyclin D1 were higher in the normal-appearing intestinal tissues of Klf4(+/-)/Apc(Min/+) mice compared with the other three genotypes. Klf4 levels were further decreased in adenomas from both Apc(Min/+) and Klf4(+/-)/Apc(Min/+) mice compared with their corresponding normal-appearing tissues. Reverse transcription-PCR showed an inverse correlation between adenoma size and Klf4 mRNA levels in both Klf4(+/-)/Apc(Min/+) and Apc(Min/+) mice. There was also a progressive loss of heterozygosity of the wild-type Apc allele in adenomas with increasing size from Klf4(+/-)/Apc(Min/+) and Apc(Min/+) mice. Results from this study show that KLF4 plays an important role in promoting the development of intestinal adenomas in the presence of Apc(Min) mutation.

KLF4 activates NFκB signaling and esophageal epithelial inflammation via the Rho-related GTP-binding protein RHOF.

Understanding the regulatory mechanisms within esophageal epithelia is essential to gain insight into the pathogenesis of esophageal diseases, which are among the leading causes of morbidity and mortality throughout the world. The zinc-finger transcription factor Krüppel-like factor (KLF4) is implicated in a large number of cellular processes, such as proliferation, differentiation, and inflammation in esophageal epithelia. In murine esophageal epithelia, Klf4 overexpression causes chronic inflammation which is mediated by activation of NFκB signaling downstream of KLF4, and this esophageal inflammation produces epithelial hyperplasia and subsequent esophageal squamous cell cancer. Yet, while NFκB activation clearly promotes esophageal inflammation, the mechanisms by which NFκB signaling is activated in esophageal diseases are not well understood. Here, we demonstrate that the Rho-related GTP-binding protein RHOF is activated by KLF4 in esophageal keratinocytes, leading to the induction of NFκB signaling. Moreover, RHOF is required for NFκB activation by KLF4 in esophageal keratinocytes and is also important for esophageal keratinocyte proliferation and migration. Finally, we find that RHOF is upregulated in eosinophilic esophagitis, an important esophageal inflammatory disease in humans. Thus, RHOF activation of NFκB in esophageal keratinocytes provides a potentially important and clinically-relevant mechanism for esophageal inflammation and inflammation-mediated esophageal squamous cell cancer.

Krüppel-like factor 5 activates MEK/ERK signaling via EGFR in primary squamous epithelial cells.

Rapid cell proliferation is a hallmark of transit amplifying cells, but the mechanisms of this localized proliferation are not well understood. The Krüppel-like factor family member Klf5 (IKLF; BTEB2) promotes cell proliferation and is highly expressed in squamous epithelia, in regions of active proliferation. Here, using mouse primary esophageal keratinocytes as a model, we identify a critical role for Klf5 in regulating squamous epithelial proliferation via the epidermal growth factor receptor (EGFR), which, like Klf5, is localized to basal cells in squamous epithelia. We show that Klf5 increases proliferation, transcriptionally up-regulates EGFR, and activates MEK/ERK signaling, as indicated by increased phosphorylation of MEK and ERK. By chromatin immunoprecipitation, we demonstrate that Klf5 binds directly to the 5' regulatory region of EGFR. In addition, we show that regulation of proliferation by Klf5 is dependent on EGFR and MEK/ERK signaling, as the proliferative response to Klf5 is blocked by pharmacologic inhibition of EGFR or MEK. Inhibition of EGFR or MEK also decreases Klf5 expression. Thus, Klf5 regulates MEK/ERK signaling via EGFR and is also downstream of MAPK signaling, providing a novel mechanism for signal amplification or suppression and control of proliferation in basal cells.

Kruppel-like factor 5 is an important mediator for lipopolysaccharide-induced proinflammatory response in intestinal epithelial cells.

Lipopolysaccharide (LPS) is a bacterially-derived endotoxin that elicits a strong proinflammatory response in intestinal epithelial cells. It is well established that LPS activates this response through NF-kappaB. In addition, LPS signals through the mitogen-activated protein kinase (MAPK) pathway. We previously demonstrated that the Krüppel-like factor 5 [KLF5; also known as intestine-enriched Krüppel-like factor (IKLF)] is activated by the MAPK. In the current study, we examined whether KLF5 mediates the signaling cascade elicited by LPS. Treatment of the intestinal epithelial cell line, IEC6, with LPS resulted in a dose- and time-dependent increase in KLF5 messenger RNA (mRNA) and protein levels. Concurrently, mRNA levels of the p50 and p65 subunits of NF-kappaB were increased by LPS treatment. Pretreatment with the MAPK inhibitor, U0126, or the LPS antagonist, polymyxin B, resulted in an attenuation of KLF5, p50 and p65 NF-kappaB subunit mRNA levels from LPS treatment. Importantly, suppression of KLF5 by small interfering RNA (siRNA) resulted in a reduction in p50 and p65 subunit mRNA levels and NF-kappaB DNA binding activity in response to LPS. LPS treatment also led to an increase in secretion of TNF-alpha and IL-6 from IEC6, both of which were reduced by siRNA inhibition of KLF5. In addition, intercellular adhesion molecule-1 (ICAM-1) levels were increased in LPS-treated IEC6 cells and this increase was associated with increased adhesion of Jurkat lymphocytes to IEC6. The induction of ICAM-1 expression and T cell adhesion to IEC6 by LPS were both abrogated by siRNA inhibition of KLF5. These results indicate that KLF5 is an important mediator for the proinflammatory response elicited by LPS in intestinal epithelial cells.

WNT10A mutation causes ectodermal dysplasia by impairing progenitor cell proliferation and KLF4-mediated differentiation.

Human WNT10A mutations are associated with developmental tooth abnormalities and adolescent onset of a broad range of ectodermal defects. Here we show that ß-catenin pathway activity and adult epithelial progenitor proliferation are reduced in the absence of WNT10A, and identify Wnt-active self-renewing stem cells in affected tissues including hair follicles, sebaceous glands, taste buds, nails and sweat ducts. Human and mouse WNT10A mutant palmoplantar and tongue epithelia also display specific differentiation defects that are mimicked by loss of the transcription factor KLF4. We find that ß-catenin interacts directly with region-specific LEF/TCF factors, and with KLF4 in differentiating, but not proliferating, cells to promote expression of specialized keratins required for normal tissue structure and integrity. Our data identify WNT10A as a critical ligand controlling adult epithelial proliferation and region-specific differentiation, and suggest downstream ß-catenin pathway activation as a potential approach to ameliorate regenerative defects in WNT10A patients.